Strongly luminous tetranuclear gold(I) complexes supported by tetraphosphine ligands, meso- or rac-Bis[(diphenylphosphinomethyl) phenylphosphino]methane

DOI: 10.1002/chem.201303729

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&

Photochemistry

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by

Tetraphosphine Ligands, meso- or rac-

Bis[(diphenylphosphinomethyl)phenylphosphino]methane

Tomoaki Tanase,*^[a]Risa Otaki,^[a]Tomoko Nishida,^[a]Hiroe Takenaka,^[a]Yukie Takemura,^[a]

Bunsho Kure,^[a]Takayuki Nakajima,^[a]Yasutaka Kitagawa,^[b]and Taro Tsubomura^[c]

Abstract: A series of tetragold(I) complexes supported by

tetraphosphine ligands, meso- and rac-bis[(diphenylphosphi-

nomethyl)phenylphosphino]methane (meso- and rac-

dpmppm) were synthesized and characterized to show that

the tetranuclear Au^Ialignment varies depending on syn- and

anti-arrangements of the two dpmppm ligands with respect

to the metal chain. The structures of syn-[Au₄(meso-

dpmppm)₂X]X’₃(X=Cl; X’=Cl (4a), PF₆(4b), BF₄(4c)) and

syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d), BF₄(4e), TfO (4 f);

TfO=triflate) involved a bent tetragold(I) core with a counter

anion X incorporated into the bent pocket. Complexes anti-

[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d), BF₄(5e), TfO (5 f))

contain a linearly ordered Au₄string and complexes syn-

[Au₄(rac-dpmppm)₂X₂]X’₂(X=Cl, X’=Cl (6a), PF₆(6b), BF₄

(6c)) and syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d), BF₄(6e),

TfO (6 f)) consist of a zigzag tetragold(I) chain supported by

the two syn-arranged rac-dpmppm ligands. Complexes

4d–f, 5d–f, and 6d–f with non-coordinative large anions are

strongly luminescent in the solid state (l_max=475–515 nm,

F=0.67–0.85) and in acetonitrile (l_max=491–520 nm, F=

0.33–0.97); the emission was assigned to phosphorescence

from ³[d_s*s*s*p_sss] excited state of the Au₄centers on the

basis of DFT calculations as well as the long lifetime (a few

ms). The emission energy is predominantly determined by

the HOMO and LUMO characters of the Au₄centers, which

depend on the bent (4), linear (5), and zigzag (6) alignments.

The strong emissions in acetonitrile were quenched by chlo-

ride anions through simultaneous dynamic and static

quenching processes, in which static binding of chloride

ions to the Au₄excited species should be the most effective.

The present study demonstrates that the structures of linear

tetranuclear gold(I) chains can be modified by utilizing the

stereoisomeric tetraphosphines, meso- and rac-dpmppm,

which may lead to fine tuning of the strongly luminescent

properties intrinsic to the Au^I₄cluster centers.

Introduction

clear gold(I) complexes are of rapidly increasing interest due to

intriguing photophysical properties, in which aurophilic inter-

actions have crucial effects on the steric and electronic struc-

tures of multinuclear gold centers. Linearly assembled crystal

structures with Au···Au separations of 2.7–3.3 ꢀ are often es-

tablished by the presence of the weak aurophilic attractions,

which are known to arise from dispersion effects with some

virtual charge transfer contribution between d¹⁰closed-shells

and are considerably strengthened by relativistic effects.^[1a,b,2]

In addition, to create molecular-based linear gold(I) chains by

controlling the aurophilic interactions, judicious choice of

bridging ligands is very important and, among them, single

methylene-bridged di- and tridentate phosphines, such as

dppm (bis(diphenylphosphino)methane) and dpmp (bis(diphe-

nylphosphinomethyl)phenylphosphine), have been known very

effective to stabilize photochemical and catalytic active multi-

metallic centers.^[5,6]Fackler, Jr. and Che independently reported

that [Au₂(dppm)₂]X₂(X=BF₄, ClO₄etc.)^[5b,c]is strongly phos-

phorescent, for example with BF₄, at l_max=593 nm (t=21 ms)

with a high quantum yield F=0.31 in acetonitrile.^[5b]While the

emission was originally assigned to arise from a triplet state of

³[5d_s*6p_s] in which both the antibonding 5d_s*and bonding 6p_s

Gold nanoclusters and nanoparticles have attracted extensive

attention because they can be used for various chemical and

biochemical sensing systems, optical and electronic devices,

and catalytic reactions.^[1–4]In their syntheses by means of

“bottom-up” approaches, small-size multinuclear gold com-

plexes are recognized as very important building blocks for

the construction of larger nanoclusters. In particular, multinu-

[a] Prof. T. Tanase, R. Otaki, T. Nishida, H. Takenaka, Dr. Y. Takemura,

Prof. B. Kure, Prof. T. Nakajima

Department of Chemistry, Faculty of Science

Nara Women’s University

Kitauoya-nishi-machi, Nara, 630-8506 (Japan)

[b] Prof. Y. Kitagawa

Department of Chemistry, Graduate School of Science

1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)

[c] Prof. T. Tsubomura

Department of Materials and Life Science

Seikei University, 3-3-1 Kichijoji-kitamachi

Musashino, Tokyo 180-8633 (Japan)

Supporting information for this article is available on the WWW under

http://dx.doi.org/10.1002/chem.201303729.

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orbitals of Au₂centers are singly occupied, it was thereafter re-

considered to come from an adduct of the excited states with

solvent, a so-called exciplex, and the intrinsic metal-centered

meric to each other with respect to the mirror plane com-

posed of four Au atoms; as a result, a bent Au₄chain is con-

structed with the meso-isomer (abbreviated as syn-(meso-

dpmppm)₂with C_2vsymmetry; Figure 1a top) and a zigzag Au₄

chain with the rac-form (syn-(rac-dpmppm)₂with C_2hsymme-

try; Figure 1b top). In the anti arrangement, the two

dpmppm’s are related with C₂symmetry and both meso- and

rac-isomers are able to support the linear Au₄chain of the C₂

axis (anti-(meso-dpmppm)₂with C_2hsymmetry—Figure 1a

bottom—and anti-(rac-dpmppm)₂with D₂symmetry—Fig-

ure 1b bottom). Consequently, the structures of Au₄chains

could be varied depending on the arrangement of two

dpmppm ligands and their configurational structures.

3

emission from the [5d_s*6p_s] excited state of digold(I) center

was found in a higher energy region around l_max=360–

368 nm for [Au₂(dcpm)₂]X₂(X=ClO₄, PF₆, TfO, Au(CN)₂) by

using a transparent diphosphine, bis(dicyclohexylphosphino)-

methane (dcpm).^[7a]Although metal-centered intense emissions

have not been observed in trigold(I) complexes with a dpmp

bridging ligand,^[6]bis(dicyclohexylphosphinomethyl)cyclohexyl-

phosphine (dcmp) was recently synthesized and a series [Au₃-

(dcmp)₂]X₃(X=ClO₄, TfO, PF₆) complexes exhibited very strong

high-energy emission from the ³[5d_s*s*6p_ss] excited state at

l_max=442–452 nm with quantum yields of 0.52–0.80.^[7b]On the

basis of these observations, red-shifted energy for the gold-

centered emission band is of particular interest if the Au^Ichain

can be extended linearly, and hence, single methylene-bridged

polydentate phosphine ligands are good candidates for explor-

ing the metal–metal concerted photochemical properties of

extended Au^Ichains. However, progress along this line have

not been made in the last decade owing to their difficult syn-

thesis, whereas multinuclear complexes supported by tetra-

dentate phosphine ligands with ethylene and longer methyl-

ene chains have been prepared and exhibited interesting syn-

ergistic effects by multinuclear metal centers.^[3b,8,9]

In the present study, we have been successful in synthesiz-

ing a new single methylene-bridged tetraphosphine ligand,

bis[(diphenylphosphinomethyl)phenylphosphino]methane

(dpmppm), meso- and rac-isomers being isolated as pure

forms. Since tetragold(I) ions aggregated by two dpmppm li-

gands, [Au₄(m-dpmppm)₂]⁴⁺would provide a useful platform

to study structure-related multinuclear effects on their photo-

physical properties, we have prepared a series of their isomers,

syn-[Au₄(meso-dpmppm)₂]X₄(4), anti-[Au₄(meso-dpmppm)₂]X₄

(5), and syn-[Au₄(rac-dpmppm)₂]X₄(6), which were character-

ized to contain a flexibly bent, entirely linear, and zigzag Au₄

chains, respectively. The Au₄molecular units with large coun-

terions, [Au₄(m-dpmppm)₂]X₄(X=PF₆, BF₄, TfO), are strongly lu-

minous in the solid state (F=0.67–0.85) from their

³[5d_s*s*s*6p_sss] excited states and the emission energy changed

systematically depending on the tetragold(I) structures from

the zigzag 6 (l_em=485–494 nm) to the bent 4 (l_em=475–

508 nm) and the linear 5 (l_em=513–515 nm). The phosphores-

cence of 4–6 was interestingly quenched by introducing chlo-

ride anions with remarkable efficiency. The present results

could be quite important to understand multinuclear d¹⁰

closed-shell concerted photochemical properties. Some of the

data, including the crystal structures of 4b, 4d, and 4g, have

already been communicated.^[11a]

Recently, we have expanded our studies with the linear tri-

phosphine dpmp^[6f,10]to those utilizing a methylene-linked

linear tetraphosphine, bis[(diphenylphosphinomethyl)phenyl-

phosphino]methane (dpmppm).^[11]This ligand has two stereo-

isomers, meso- and rac-forms, with respect to the chiral centers

of the two inner P atoms, and when two dpmppm ligands

support four gold(I) ions, four topologically different structures

of the Au₄chain can be established as depicted in Figure 1.

Ideally in the syn-arrangement, the two dpmppm’s are enantio-

Results and Discussion

Preparations of meso- and rac-dpmppm and [Au₄Cl₄(meso-

or rac-dpmppm)] (2 or 3)

Bis[(diphenylphosphinomethyl)phenylphosphino]methane

(meso-dpmppm) was prepared as shown in Scheme 1. Bis(phe-

nylphosphino)methane^[8a,12]was treated with nBuLi and then

with Me₃SiCH₂Cl to afford bis[(trimethylsilylmethyl)phenylphos-

phino]methane (tmsmppm), in which the ratio of meso- and

rac-isomers was about 4:1 determined by ³¹P{¹H} NMR spec-

troscopy. Addition of Ph₂PCl to tmsmppm, followed by heating

at 958C for 1 h, yielded meso-isomer-rich dpmppm, which was

precipitated from acetone and washed with methanol to give

meso-dpmppm as pure white powder in 50% yield versus

tmsmppm. The ³¹P{¹H} NMR spectrum showed two resonances

in AA’BB’ spin system of the P nuclei, which were simulated

with the parameters d=ꢀ23.0 (P_out) and ꢀ34.7 ppm (P_in) for

Figure 1. The ideal structures of [Au₄(m-dpmppm)₂]⁴⁺showing the arrange-

ments of two dpmppm ligands with respect to the tetragold chains abbrevi-

ated as a) top: syn-(meso-dpmppm)₂with C_2vsymmetry; bottom: anti-(meso-

dpmppm)₂with C_2hsymmetry; and b) top: syn-(rac-dpmppm)₂with C_2hsym-

metry; bottom: anti-(rac-dpmppm)₂with D₂symmetry.

2

the outer and inner P atoms, and J_P=117.1, J_P=92.1,

_inP_out

_inP_in’

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Scheme 2. Structures of [Au₄Cl₄(meso-dpmppm)] (2) and [Au₄Cl₄(rac-

dpmppm)] (3).

with ²J_P=114.2, ²J_P=105.4, ⁴J_P

=3.4, and ⁶J_P

=

_outP_out’

_inP_out

_inP_in’

_outP_in’

0.1 Hz (Figure S1b in the Supporting Information).

Each tetraphosphine was treated with [AuCl(tht)] in 1:4 ratio

in an ethanol suspension to give colorless microcrystals of

[Au₄Cl₄(meso-dpmppm)] (2) or [Au₄Cl₄(rac-dpmppm)] (3) quan-

titatively (Scheme 2), which were further recrystallized from

DMF as colorless needle crystals of 2·1.5DMF and

3·0.25DMF·2CH₂Cl₂, respectively. The ³¹P{¹H} NMR spectra of 2

and 3 exhibited two multiplets at d=25.6 (P_out) and 22.2 ppm

(P_in) for 2 and d=26.7 (P_out) and 21.4 ppm (P_in) for 3, which

Scheme 1. Preparations of meso- and rac-dpmppm.

were assigned to AA’BB’ spin systems with ²J_P=54.8,

_inP_out

4

6

2

⁴J_P

=3.9, and ⁶J_P

=0.1 Hz (see Figure S1a in the Support-

²J_P=56.6, J_P

=2.2, and J

=0.2 Hz for 2 and J_P

=

_inP_out

_outP_in’

_outP_out’

_inP_in’

_outP_in’

PoutPout’

ing Information).

56.7, ²J_P=48.0, ⁴J_P

=1.7, and ⁶J_P

=0.1 Hz for 3 (Fig-

_outP_out’

_inP_in’

_outP_in’

When solid meso-dpmppm was heated under argon atmos-

phere at 1658C for 1 h, the chiral centers of the P atoms were

readily epimerized through pyramidal inversion mechanisms^[13]

to result in an equilibrium mixture of meso- and rac-dpmppm

in an approximate 1:1 ratio. The isomerization of meso-

dpmppm occurred even in a [D₈]toluene solution at 1008C,

obeying first-order kinetics, with the analyzed values of k₁=

1.54ꢂ10^ꢀ2s^ꢀ1, k_ꢀ1=1.80ꢂ10^ꢀ2s^ꢀ1, and K=k₁/k_ꢀ1=0.85 (Fig-

ure S2 in the Supporting Information). The oily mixture of

meso- and rac-dpmppm was further reacted with about three

equivalents of [PdCl₂(cod)] in dichloromethane, immediately

forming a pale yellow precipitate of [Pd₂Cl₄(rac-dpmppm)] (1)

in 43% yield with respect to the starting material meso-

dpmppm. Complex 1 was recrystallized from N,N-dimethyl for-

mamide (DMF) and characterized by X-ray crystallography (Fig-

ure S3 in the Supporting Information); the X-ray analysis indi-

cates that it contains two cis-Pd^IICl₂units bridged by a rac-

dpmppm ligand with pseudo-C₂symmetry. The two palladium

atoms are spanned at an average distance of 4.430 ꢀ with

triple bridges of the P_inP_inand two P_outP_inpairs. The ³¹P{¹H}

spectrum in [D₇]DMF consisted of two resonances at d=19.4

(P_out) and 17.7 ppm (P_in) with the simulated coupling constants

ure S1d,e in the Supporting Information). Complexes 2 and 3

are sparingly soluble in usual organic solvents and soluble only

in DMF and dimethyl sulfoxide (DMSO).

An X-ray diffraction analysis was performed on the crystals

of 2 obtained from a DMSO/Et₂O mixed solvent (Figure 2).

Four AuCl units are attached to the tetraphosphine ligand

meso-dpmppm to form a neutral molecule composed of four

P-Au-Cl linear fragments (av AuꢀCl=2.295, av AuꢀP=2.233 ꢀ,

av P-Au-Cl=174.018). The flexible {PCH₂PCH₂PCH₂P} backbone

disperses the four Au^Iions with interatomic distances of

Au1···Au2=3.3392(6),

Au2···Au3=3.3712(6),

Au3···Au4=

3.3402(7) ꢀ, suggesting the presence of only a weak aurophilic

interaction.^[1a,b,2]The outer Au-P-P-Au torsion angles indicate

planar arrangements of Au1-P1-P2-Au2 (4.948) and Au3-P3-P4-

Au4 (1.888), which are in contrast to the twisted arrangement

of Au2-P2-P3-Au3 (58.618) in the central part, these may be

a result from a delicate balance between the attractive auro-

philic interactions and electrostatic repulsions within the

of ²J_P=45.7, ²J_P=38.6, ⁴J_P

=0.3, and ⁶J_P

=0.1 Hz

_outP_out’

_inP_out

_inP_in’

_outP_in’

(Figure S1c in the Supporting Information), which are in agree-

ment with the crystal structure. Since the mother liquor pre-

dominantly contained dipalladium complex with meso-

dpmppm, [Pd₂Cl₄(meso-dpmppm)] (the detailed structure is

not identified), the low solubility of 1 in CH₂Cl₂should be re-

sponsible for its successful isolation. Treatment of 1 with

excess of NaCN in a biphasic system with dichloromethane

and water^[14]lead to the quantitative isolation of rac-dpmppm

as pure oil; it was characterized by ³¹P{¹H} NMR spectroscopy,

showing two peaks at d=ꢀ23.3 (P_out) and ꢀ34.0 ppm (P_in)

Figure 2. ORTEP diagram of 2 with thermal ellipsoids at the 40% probability

level. The hydrogen atoms are omitted for clarity.

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Scheme 3. Synthesis of syn-[Au₄(meso-dpmppm)₂Cl]X₃(X=Cl (4a), PF₆(4b),

BF₄(4c), syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d), BF₄(4e), TfO (4 f)), and

syn-[Au₄(meso-dpmppm)₂I₂][PF₆]₂.

neighboring chloride anions (Cl1···Cl2=4.128(4), Cl2···Cl3=

4.894(5), and Cl3···Cl4=4.012(5) ꢀ). The similar twisted struc-

ture was observed in [Au₂Cl₂(dppm)] (Au···Au=3.351(2) ꢀ and

Au-P-P-Au=67(1)8).^[15]

Figure 3. ORTEP diagrams for a) {syn-[Au₄(meso-dpmppm)₂]Cl}³⁺of 4b and

b) {syn-[Au₄(meso-dpmppm)₂]OTf}³⁺of 4 f with thermal ellipsoids at the 40%

probability level. The hydrogen atoms are omitted for clarity.

Synthesis and structures of syn-[Au₄(meso-dpmppm)₂Cl]X₃

(X=Cl (4a), PF₆(4b), BF₄(4c)), syn-[Au₄(meso-dpmppm)₂]X₄

(X=PF₆(4d), BF₄(4e), TfO (4 f)), and {syn-[Au₄(meso-

dpmppm)₂I₂][PF₆]₂}₂(4g)

are recognized as deformed structures from the ideal syn-ar-

rangement of two meso-dpmppm ligands (abbreviated as syn-

(meso-dpmppm)₂with C_2vsymmetry, Figure 1). In the structures

of 4b and 4d, a terminal methylene unit of each meso-

dpmppm is flipped outside leading to a pseudo-C₂axis passing

through the midpoint of the central two Au atoms, Au2···Au3;

the Au₄chain is somewhat twisted with the Au-Au-Au-Au tor-

sion angles of 32.95(6)8 (4b) and 28.08(6)8 (4d). In 4e and 4 f,

the central methylene unit of one meso-dpmppm is turned

outside, resulting in pseudo-C_ssymmetrical structures in which

the four Au ions are constrained in a plane with the Au-Au-Au-

Au torsion angles of 2.30(2) (4e) and 5.15(2)8 (4 f). These defor-

mations may occur to avoid steric repulsions between the

phenyl groups of two meso-dpmppm ligands, which could

arise from incorporation of a counter anion into the bent Au₄

pocket (Figure 4).

When meso-dpmppm was treated in dichloromethane with

two equivalents of [AuCl(PPh₃)] in the presence of NH₄X, pale

yellow tetragold(I) complexes, syn-[Au₄(meso-dpmppm)₂Cl]X₃

(X=PF₆(4b) BF₄(4c)) were obtained in moderate yields

(Scheme 3). A similar reaction without NH₄X afforded syn-

[Au₄(meso-dpmppm)₂Cl]Cl₃(4a) in 67% yield. Complexes 4b

and 4c were transformed by treating with AgPF₆or AgBF₄to

give the anion-exchanged complexes syn-[Au₄(meso-

dpmppm)₂]X₄(X=PF₆(4d), BF₄(4e)), respectively, in good

yields. Reaction of 4b with excess NH₄OTf also yielded syn-

[Au₄(meso-dpmppm)₂][TfO]₄(4 f). When complex 4b was treat-

ed with 2.5 equivalents of KI in a CH₂Cl₂/MeOH mixed solvent,

orange crystals of the octagold(I) complex syn-[{Au₄(meso-

dpmppm)₂I₂}₂][PF₆]₄(4g) was isolated in 18% yield (Scheme 3).

Complexes 4a–g were characterized by ¹H and ³¹P{¹H} NMR,

ESI-MS, IR, and UV/Vis spectra and X-ray crystallography for

4b,d–g (the structures of 4b, 4d, and 4g have already been

communicated).^[11a]

In 4b, the Au···Cl interatomic distances of 3.664(6)

(Au1···Cl1), 3.132(6) (Au2···Cl1), 3.162(6) (Au3···Cl1), and

3.803(6) ꢀ (Au4···Cl1) suggest the presence of an electrostatic

attraction between the inner two Au^Iions (Au2, Au3) and the

Cl^ꢀanion, in the light of the sum of van der Waals radii

(3.26 ꢀ); the outer gold atoms (Au1, Au4) are out of the secon-

ꢀ

ORTEP diagrams for 4b and 4 f are illustrated in Figure 3a,

b (those for 4d and 4e are supplied as Figures S4 and S5 in

the Supporting Information) and selected structural parameters

are summarized in Table 1. Complexes 4b and 4d–f contain

bent Au^I₄chains bridged by two meso-dpmppm ligands, which

dary interaction range. The other anions PF₆(4d), BF₄(4e),

and TfO^ꢀ(4 f) are housed in their shallow pockets with much

weaker electrostatic interactions, presumably due to lower

charge densities of the polyatomic anions; all the observed in-

teratomic distances are longer than the sums of van der Waals

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Table 1. Structural parameters of syn-[Au₄(meso-dpmppm)₂Cl]X₃(X=PF₆(4b)) and syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d), BF₄(4e), TfO (4 f), I (4g)).

4b^[a,f]

4d^[b,f]

4e^[c]

4 f^[d]

4g^[e,f]

X

Cl

PF₆

BF₄

TfO

I

Au_out···Au_in[ꢀ]

2.948(1)

2.924(1)

av 2.936

2.953(1)

7.281

2.303

2.306

134.98(4)

137.37(3)

av 136.18

175.5

2.9743(2)

2.9700(5)

av 2.9722

2.9595(3)

8.274

2.312

2.316

143.19(1)

163.89(1)

av 153.54

178.19

2.9704(2)

2.9774(2)

av 2.9739

2.9562(2)

7.599

2.3238

2.3166

140.746(7)

141.866(8)

av 141.306

177.98

2.9388(3)

3.0080(3)

av 2.9734

2.9036(3)

7.942

2.3187

2.3177

149.583(8)

146.231(9)

av 147.907

175.59

3.0867(6)

2.954(1)

av 3.020

3.0243(8)

8.744

2.322

2.307

156.20(3)

166.90(3)

av 161.55

165.06

Au_in···Au_in[ꢀ]

Au_out···Au_out[ꢀ]

av Au_outꢀP_out[ꢀ]

av Au_inꢀP_in[ꢀ]

Au_out···Au_in···Au_out[8]

av P_out-Au_out-P_out[8]

av P_in-Au_in-P_in[8]

178.5

178.02

177.52

175.63

172.15

av P_out-Au_out-Au_in-P_in[8]

av P_in-Au_in-Au_in-P_in[8]

Au_out-Au_in-Au_in-Au_out[8]

av Au_in···X [ꢀ]

1.6

21.2

10.57

18.99

28.08(6)

3.077(6) (Au2ꢀF2)

3.081(6) (Au3ꢀF1)

av 3.080

20.73

2.63

2.30(2)

3.349(4) (Au2ꢀF1)

3.388(4) (Au3ꢀF1)

3.449(5) (Au3ꢀF3)

3.351(3) (Au2ꢀF2)

av 3.384

18.00

2.58

5.15(2)

3.204(4) (Au2ꢀO2)

3.458(4) (Au3ꢀO1)

3.531(4) (Au2ꢀO3)

av 3.332

4.9

0.8

3.8(1)

3.017(1) (Au2ꢀI1)

3.232(1) (Au3ꢀI2)

av 3.125

32.95(6)

3.132(6) (Au2ꢀCl1)

3.162(6) (Au3ꢀCl1)

av 3.147

av Au_out···X [ꢀ]

3.664(6) (Au1ꢀCl1)

3.803(6) (Au4ꢀCl1)

av 3.734

3.393(6) (Au1ꢀF2)

3.738(5) (Au4ꢀF1)

av 3.566

3.151(3) (Au1ꢀF2)

3.427(4) (Au4ꢀF3)

av 3.290

3.088(4) (Au1ꢀO2)

3.818(4) (Au4ꢀO1)

av 3.453

3.160(1) (Au1ꢀI1)

3.162(2) (Au2ꢀI2)

av 3.161

[a] See Figure 3a. [b] See Figure S4 in the Supporting Information. [c] See Figure S5 in the Supporting Information. [d] See Figure 3b in the Supporting In-

formation. [e] See Figure S6 in the Supporting Information. [f] Reference [11a].

the BF₄and TfO anions have shorter contacts to the Au_outions

(Au1···F2=3.151(3) (4e), Au1···O2=3.088(4) ꢀ (4 f)). The aver-

age Au···Au···Au angles vary from 136.18 (4b) to 141.31 (4e),

147.91 (4 f), to 153.548 (4d), depending on the size of the

trapped counter anions (Figure 4). The Au···Au separations are

not affected by the anions (av 2.942 (4b), 2.968 (4d), 2.968

(4e), and 2.950 ꢀ (4 f)) and indicate the presence of strong au-

rophilic interaction between them.^[1a,b,2]The intramolecular dis-

tances between the outer two Au ions are 8.274 (4d), 7.942

(4 f), 7.599 (4e), and 7.281 ꢀ (4b), which show an order similar

to that for the Au···Au···Au angles. These results demonstrated

that the flexible Au₄chains with a syn-(meso-dpmppm)₂ar-

rangement are likely to vary its bending form depending on

the size of counter anions trapped.

The complex cation of 4g was elucidated by X-ray crystal-

lography to have a linear octagold(I) core comprised of two

tetragold(I) units, syn-[Au₄(meso-dpmppm)₂I₂]²⁺(Scheme 3),

Figure 4. Perspective views showing interactions of syn-[Au₄(meso-

dpmppm)₂]⁴⁺with a) Cl^ꢀ(4b), b) PF₆^ꢀ(4d), c) BF₄^ꢀ(4e), and d) TfO^ꢀ(4 f).

connected by two m₃-iodide bridges (Figure S6 in the Support-

The tetragold parts and the counter anions are illustrated with space-filling

ing Information).^[11a]The Au···Au separations (2.954(1)–

models.

3.0867(6) ꢀ, av 3.022 ꢀ) are slightly longer than those of 4b,d–

radii (2.81–2.86 ꢀ) (Table 1). While the large PF₆anion of 4d fits

well the Au₄chain with rather short separations between the

central two Au_inions (Au2···F2=3.077(6), Au3···F1=3.081(6) ꢀ),

f, and the average Au···Au···Au angle of 161.558 is larger than

that of 4d. The AuꢀI distances, ranging from 3.017(1) to

3.232(2) ꢀ (av 3.125 ꢀ), fall between the values for the sums of

Chem. Eur. J. 2014, 20, 1577 – 1596

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The second and third groups exhibited an upfield shift in-

duced by appreciable interaction of the complex cations with

the halide anions, suggesting that 4a–c exist as an adduct of

{syn-[Au₄(meso-dpmppm)₂]Cl}³⁺and 4g as {syn-[Au₄(meso-

dpmppm)₂]I₂}²⁺, as observed in the crystal structures. Further-

more in 4a–c with a nesting chloride anion, the degrees of

higher field shift for the inner P atoms were more conspicuous

than for the outer P atoms, referenced to the chemical shifts

for 4d–f with large counter anions (the first group). The values

of chemical shifts for the first group complexes 4d–f are

ꢀ

almost identical irrespective of the counter anions of PF₆

,

BF₄^ꢀ, and TfO^ꢀ, indicating that the tetragold cations of 4d–f

exist in the solutions as syn-[Au₄(meso-dpmppm)₂]⁴⁺without

remarkable interaction with the anions.

Synthesis and structures of anti-[Au₄(meso-dpmppm)₂]X₄

(X=PF₆(5d), BF₄(5e), TfO (5 f))

AgX (X=PF₆, BF₄, TfO) (4 equiv), meso-dpmppm (1 equiv), and

2,6-xylyl isocyanide (XylNC) (4 equiv) were added to a suspen-

sion of [Au₄Cl₄(meso-dpmppm)] (2) in toluene and the mixture

was stirred at room temperature in the dark for 12 h. The resul-

tant precipitate was crystallized from a dichloromethane/dieth-

yl ether mixed solvent to afford pale yellow crystals of anti-

[Au₄(meso-dpmppm)₂]X₄in low yields (X=PF₆(5d, 29%), BF₄

(5e, 25%), TfO (5 f, 11%)) (Scheme 4). Complex 5 f was also ob-

tained by reacting 2 with one equivalent of meso-dpmppm in

the presence of AgOTf (4 equiv) in 11% yield. However,

though the roles of XylNC are not clear, the reactions in the

absence of the isocyanide led to a failure to isolate 5d and 5e.

The structures of 5d–f were determined by X-ray crystallog-

raphy; ORTEP plot for the complex cation of 5d is shown in

Figure 6 (those for 5e and 5 f are deposited in Figure S7 in the

Supporting Information), and the structural parameters are

listed in Table 2. The structures of 5d–f have crystallographical-

ly imposed inversion centers at the midpoint of the central

two Au_inatoms and have almost linearly aligned tetranuclear

Au^Iions supported by two meso-dpmppm ligands in the anti-

arrangement as shown in Figure 1 (abbreviated as anti-(meso-

dpmppm)₂). The Au···Au···Au angles are 177.78(2) (5d), 177.99

(av, 5e), and 171.34(1)8 (5 f), which definitely demonstrate

linear alignment of the tetragold chains and are in contrast to

the flexible bent structures of 4 with a syn-(meso-dpmppm)₂

arrangement. The Au···Au distances of 5 are shorter than those

of 4, suggesting the presence of stronger aurophilic interac-

Figure 5. ³¹P{¹H} NMR spectra for the meso-dpmppm region of a) 4 f, b) 4e,

c) 4d, d) 4a, e) 4c, f) 4b, and g) 4g in CD₂Cl₂at room temperature.

covalent bond (2.67 ꢀ) and van der Waals radii (3.61 ꢀ), sug-

gesting the presence of a weak bonding interaction between

the Au^Iand I^ꢀions. Whereas the octanuclear complex cation of

4g possesses a crystallographically imposed inversion center,

the tetragold(I) fragment itself has a pseudo-C₂axis at the mid-

point of the inner two gold ions as observed in 4b and 4d. In

the solution state, the octanuclear complex cation is assumed

to fragmentate into syn-[Au₄(meso-dpmppm)₂I₂]²⁺(Scheme 3),

which was confirmed by the ESI MS (m/z: 1149.05 for [Au₄-

(dpmppm)₂I₂]²⁺) and the ³¹P{¹H} NMR spectrum (d=29.03

(P_out), 22.03 ppm (P_in)).

The ³¹P{¹H} NMR spectra of 4a–g in CD₂Cl₂showed quite

similar spectral patterns with two multiplets in 1:1 intensity

ratio (Figure 5), consistent with the C_2vsymmetrical tetranu-

clear structure of syn-[Au₄(meso-dpmppm)₂]⁴⁺. Furthermore,

the complexes can be classified into three groups from the d

values of their chemical shifts:

1) 4d (d=36.5 (P_out), 32.3 ppm (P_in)), 4e (d=35.4 (P_out),

31.3 ppm (P_in)), 4 f (d=35.1 (P_out), 31.3 ppm (P_in)).

2) 4a (d=33.1 (P_out), 27.7 ppm (P_in)), 4b (d=34.5 (P_out),

28.1 ppm (P_in)), 4c (d=34.0 (P_out), 27.8 ppm (P_in)).

3) 4g (d=29.03 (P_out), 22.03 ppm (P_in)).

Scheme 4. Preparations of anti-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d), BF₄

(5e), TfO (5 f)).

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tion; in particular the Au_in···Au_indistances (2.8658(2)

(5d), 2.8833 (av, 5e), 2.8981(3) ꢀ (5 f)) are appreciably

shorter than those of the Au_in···Au_outdistances

(2.9106(3) (5d), 2.9390 (av, 5e), 2.9511(3) ꢀ (5 f)). Due

to the linearity, the Au_out···Au_outseparations (8.686

(5d), 8.763 (av, 5e), 8.778 ꢀ (5 f)) are large compared

with those for complexes 4b and 4d–f. The P-Au-P

linear moieties are rather twisted between the Au_out

and Au_incenters (P-Au-Au-P torsion angles are 14.54–

18.278) and in parallel between the two Au_incenters

(P-Au-Au-P torsion angles are 0.52–4.388). The two

counter anions very weakly contact to the central

Au_incenters (>ca. 3.2 ꢀ).

Table 2. Structural parameters of anti-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d), BF₄(5e),

and TfO (5 f)).

5d^[a]

5e^[b]

5 f^[c]

X

PF₆

BF₄

TfO

Au_out···Au_in[ꢀ]

2.9106(3)

2.9294(3), 2.9486(3)

av 2.9390

2.9511(3)

In the solution state, the anti complexes 5 are not

stable and slowly isomerize into syn-[Au₄(meso-

dpmppm)₂]⁴⁺(4); this process was monitored by

³¹P{¹H} NMR spectroscopy. The ³¹P{¹H} NMR spectrum

of 5 f in CD₃CN consists of two broad multiplets in

a narrow range around d=35–36 ppm; however, res-

onances for the syn complex 4 f appeared after sever-

al hours, and finally, the spectral patters mostly

changed to those of 4 f after several days (Figure S8a

in the Supporting Information). The isomerization

was analyzed with first-order kinetics for the concen-

tration^[5f]to give an apparent rate constant k=2.54ꢂ

10^ꢀ6s^ꢀ1and a half-life time t_1/2=2.73ꢂ10⁵s (Fig-

ure S8b, c in the Supporting Information). In CD₂Cl₂,

the anti-to-syn isomerization proceeded very slowly

Au_in···Au_in[ꢀ]

2.8658(2)

8.686

2.8898(3), 2.8833(3)

av 2.8866

8.7452(3), 8.7803(3)

av 8.7628

2.8981(3)

8.778

Au_out···Au_out[ꢀ]

av Au_outꢀP_out[ꢀ]

av Au_inꢀP_in[ꢀ]

2.319

2.311

177.78(2)

2.320

2.324

2.323

2.325

Au_out···Au_in···Au_out[8]

176.65(1), 179.336(8) 171.34(1)

av 177.99

P_out-Au_out-P_out[8]

P_in-Au_in-P_in[8]

P_out-Au_out-Au_in-P_in[8]

P_in-Au_in-Au_in-P_in[8]

Au_out-Au_in-Au_in-Au_out[8] 0.0

Au_in···X [ꢀ]

172.01(8)

174.82(8)

18.27(8)

3.49(8)

174.30

176.74

av 14.54

av 0.52

0.0

174.26(6)

174.92(7)

15.66(7)

4.38(7)

0.0

3.196(8) (Au2ꢀF8*) 3.339(5) (Au2ꢀF13)

3.187(5) (Au2ꢀF15*)

3.34(1) (Au2ꢀO1)

3.291(4) (Au4ꢀF5)

3.322(3) (Au4ꢀF8*)

[a] See Figure 6. [b] See Figure S7a, b in the Supporting Information. [c] See Fig-

ure S7c in the Supporting Information.

to afford an approximate 1:1 mixture of 5 f and 4 f after three

weeks.

Synthesis and structures of syn-[Au₄(rac-dpmppm)₂Cl₂]X₂

(X=Cl (6a), PF₆(6b), BF₄(6c)) and syn-[Au₄(rac-

dpmppm)₂]X₄(X=PF₆(6d), BF₄(6e), TfO (6 f))

Reaction of rac-dpmppm with [AuCl(PPh₃)] (2 equiv) in CH₂Cl₂

at room temperature afforded syn-[Au₄(rac-dpmppm)₂Cl₂]Cl₂

(6a) in 62% yield. Similar reactions using [AuCl(tht)] in the

presence of NH₄X (X=PF₆, BF₄) also gave syn-[Au₄(rac-

dpmppm)₂Cl₂]X₂(X=PF₆(6b), BF₄(6c)) in 47 and 63% yields,

respectively (Scheme 5), and that with NH₄OTf yielded syn-

[Au₄(rac-dpmppm)₂][TfO]₄(6 f) in 14% yield. When complex 6 f

was treated with NH₄X (X=PF₆, BF₄), the TfO anions were re-

placed by the respective large anions to afford pale yellow

crystals of syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d), BF₄(6e)).

Complexes 6a–f were characterized by IR, UV/Vis, ³¹P{¹H} and

¹H NMR spectroscopy and ESI mass spectrommetry, and for

6a–c,e,f in addition by X-ray crystallographic analyses.

ORTEP plots for the complex cations of 6b and 6 f are illus-

trated in Figure 7a, b (those for 6a,c,e are supplied in the Sup-

porting Information, Figure S9a–c), and the structural parame-

Figure 6. a) ORTEP view for the complex cation of anti-[Au₄(meso-

dpmppm)₂][PF₆]₄(5d) with thermal ellipsoids at the 40% probability level.

The hydrogen atoms are omitted for clarity. b) A diagram in which the tetra-

gold ions are illustrated with space-filling models to show the linear arrange-

ment.

ters are summarized in Table 3. In the crystal structures of 6a–

c,e,f, four two-coordinate gold(I) ions are bridged by two rac-

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Au···Au···Au angles of 138.37(1) (6a), 134.50(2) (6b), 142.83(2)

(6c), 145.35(2) (6e), and 148.58(2)8 (6 f), which are comparable

to those of 4 with bent structures by syn-(meso-dpmppm)₂ar-

rangement. The crystallographic C_isymmetry constrains the

zigzag Au₄chains as planar. Two counter anions are trapped

into each zigzag pocket of the Au₄structures (Figure 8a, b).

Like in complexes 4, the chloride ions in 6a–c should be more

tightly incorporated with the interatomic distances of 2.974(2)–

3.089(3) ꢀ to the Au_inions and 3.017(2)–3.218(3) ꢀ to the Au_out

ones, which are notably shorter than the sum of van der Waals

ꢀ

radii (3.26 ꢀ). The BF₄and TfO^ꢀions are also placed in the po-

sition with the shortest contacts to Au: Au_in···F1=3.121(8) (6e)

and Au_in···O2=3.151(11) ꢀ (6 f); these electrostatic interactions

should be very weak in comparison with that with the chloride

anions in 6a–c, which were evidenced by the higher field shift

in the ³¹P{¹H} NMR spectra. Whereas the ³¹P{¹H} NMR spectrum

of 6 f showed two broad multiplets at d=35.5 (P_out) and

31.1 ppm (P_in) in 1:1 intensity ratio, those of 6a–c exhibited

two peaks at d=32.5 (P_out) and 28.1 (P_in) (6a), 31.9 (P_out) and

27.2 (P_in) (6b), and 31.6 (P_out) and 26.3 ppm (P_in) (6c), both the

peaks for P_outand P_insuffering some higher field shifts, imply-

ing that the Au₂···Cl weak interaction in the Au₄zigzag pockets

are retained even in the solution state. The Au···Au distances

of 6 are also similar to those of 4; the Au_in···Au_indistances

(2.956(2) (6a), 2.9713(4) (6b), 3.0065(7) (6c), 2.9585(6) (6e),

2.9545(6) ꢀ (6 f)) are almost identical to those of the Au_in···Au_out

distances (2.973(2) (6a), 2.9635(4) (6b), 2.9736(7) (6c),

2.9442(6) (6e), 2.9080(4) ꢀ (6 f)), suggesting the presence of

aurophilic interactions. The Au_out···Au_outseparations (8.370 (6a),

8.294 (6b), 8.573 (6c), 8.505 (6e), 8.527 ꢀ (6 f)) fall between

the values for the linear anti complexes 5d–f and for the bent

syn complexes 4b,d–f. The P-Au-P linear moieties are rather

twisted between the Au_outand Au_incenters (P-Au-Au-P torsion

angle is 13.56–20.148) and in parallel between the two Au_in

centers (P-Au-Au-P torsion angle is 0.26–4.708).

Scheme 5. Preparations of syn-[Au₄(rac-dpmppm)₂Cl₂]X₂(X=Cl (6a), PF₆

(6b), BF₄(6c)) and syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d), BF₄(6e), TfO

(6 f)).

Electronic absorption and emission spectra and theoretical

calculations

The UV/Vis absorption and emission spectroscopic data of

complexes 4a–f, 5d–f, and 6a–f are listed in Table 4. The ab-

sorption spectra of 4d–f, 5d–f, and 6d–f in CH₂Cl₂(Figure 9a–

c) show a characteristic intense bands around 363–370 nm

(loge=4.51–5.07) for 4d–f, 387–389 nm (loge=4.81–5.11) for

5d–f, and 358–360 nm (loge=4.53–4.95) for 6d–f, together

with broad absorptions at l<300 nm by phenyl groups of the

phosphine ligands. On the basis of TD-DFT calculations on the

models, syn-[Au₄(meso-H₂PCH₂P(H)CH₂P(H)CH₂PH₂)₂]⁴⁺(M4),

anti-[Au₄(meso-H₂PCH₂P(H)CH₂P(H)-CH₂PH₂)₂]⁴⁺(M5), and syn-

[Au₄(rac-H₂PCH₂P(H)CH₂P(H)CH₂PH₂)₂]⁴⁺(M6), which were opti-

mized by DFT calculations using MPWPW91 functions^[16]with

Stuttgart–Dresden ECP basis set (SDD, the 19-valence electron

Wood–Boring quasi-relativistic pseudopotentials were used for

Au),^[17]the lowest energy bands are assigned to as spin-al-

Figure 7. ORTEP diagrams for a) {syn-[Au₄(rac-dpmppm)₂]Cl₂}²⁺of 6b and b)

{syn-[Au₄(rac-dpmppm)₂](OTf}₂}²⁺of 6 f with thermal ellipsoids at the 40%

probability level. The hydrogen atoms are omitted for clarity.

1

dpmppm ligands in a syn-arrangement as shown Figure 1 (ab-

breviated as syn-(rac-dpmppm)₂) with an inversion center. The

array of Au₄ions is not linear, but a zigzag form with the

lowed [5d_s*s*s*!6p_sss] (HOMO!LUMO) transition (l=365 nm,

f (oscillator strength)=0.383 for M4, l=365 nm, f=0.581 for

M5, and l=361 nm, f=0.433 for M6). The HOMOs of M4–6

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Table 3. Structural parameters of syn-[Au₄(rac-dpmppm)₂Cl₂]X₂(X=Cl (6a), PF₆(6b), BF₄(6c)) and syn-[Au₄(rac-dpmppm)₂]X₄(X=BF₄(6e), TfO (6 f)).

6a^[a]

6b^[b]

6c^[c]

6e^[d]

6 f^[e]

X

Cl

BF₄

TfO

X’

Cl

PF₆

BF₄

TfO

Au_out···Au_in[ꢀ]

Au_in···Au_in[ꢀ]

Au_out···Au_out[ꢀ]

av Au_outꢀP_out[ꢀ]

av Au_inꢀP_in[ꢀ]

Au_out···Au_in···Au_out[8]

P_out-Au_out-P_out[8]

P_in-Au_in-P_in[8]

P_out-Au_out-Au_in-P_in[8]

P_in-Au_in-Au_in-P_in[8]

Au_out-Au_in-Au_in-Au_out[8]

Au_in···X [ꢀ]

2.956(2)

2.973(2)

8.370

2.307

2.315

138.37(1)

171.83(7)

176.27(6)

13.56(6)

2.21(4)

0.0

2.9713(4)

2.9635(4)

8.294

2.310

2.311

134.50(2)

171.7(1)

177.4(1)

18.4(1)

0.26(8)

0.0

3.0065(7)

2.9736(7)

8.573

2.344

2.339

142.83(2)

176.5(1)

175.3(1)

19.5(1)

3.24(1)

0.0

2.9585(6)

2.9442(6)

8.505

2.330

2.331

145.35(2)

169.38(9)

176.53(10)

13.76(10)

1.44(9)

2.9545(6)

2.9080(4)

8.527

2.325

2.327

148.58(2)

176.82(13)

173.41(9)

20.14(11)

4.70(12)

0.0

2.974(2)(Au2ꢀCl1)

3.089(3)(Au2ꢀCl1)

3.032(2)(Au2ꢀCl1)

3.121(8)(Au2ꢀF1)

3.349(6)(Au2ꢀF2*)

3.283(8)(Au1ꢀF1)

3.151(11)(Au2ꢀO1)

3.566(16)(Au2ꢀO2*)

3.255(13)(Au1ꢀO3)

3.505(7)(Au1ꢀO1)

Au_out···X [ꢀ]

3.017(2)(Au1ꢀCl1)

3.044(3)(Au1ꢀCl1)

3.218(3)(Au1ꢀCl1)

[a] See Figure S9a in the Supporting Information. [b] See Figure 7a. [c] See Figure S9b in the Supporting Information. [d] See Figure S9c in the Supporting

Information. [e] See Figure 7b.

mixed with the orbitals of phosphine ligands (Figure 10a and

b, and Figures S10–S12 in the Supporting Information). Hence,

1

the [5d_s*s*s*!6p_sss] absorption might be partially mixed with

metal-to-metal-to-ligand charge transfer (¹MMLCT) character.

The absorption energy of 4d–f, 5d–f, and 6d–f is appreciably

red-shifted with respect to the 5d_s*!6p_stransition reported

for digold(I) complexes with dppm and dcpm (ca. 270–

300 nm)^[5,7a]and the 5d_s*s*!6p_sstransition for trigold(I) com-

plexes with dpmp and dcmp (ca. 329–350 nm).^[7b]In relation to

[Au₂(dcpm)₂]²⁺and [Au₃(dcmp)₂]³⁺together with our com-

pound syn-[Au₄(meso-dpmppm)₂]⁴⁺, Che and his co-workers

carried out TD-DFT calculations on the linear models of [Au_n-

{H₂P(CH₂PH)_nꢀ2CH₂PH₂}₂]ⁿ⁺(n=2–4) to assign the absorption

bands to spin-allowed metal-centered HOMO–LUMO transi-

1

tions [5d_s*!6p_s] partially mixed with MMLCT character. In the

present study, the optimized model structures of the singlet

ground state (S₀) slightly differ from each other depending on

the arrangement and configuration of the two phosphine li-

gands H₂PCH₂P(H)CH₂P(H)CH₂PH₂, although the steric factors

are neglected by replacing phenyl groups with hydrogen

atoms (Table 5). The calculated Au···Au separations are all indi-

cative of aurophilic interaction (Au···Au=3.064–3.132 ꢀ).

Whereas the optimized structures of the models M4 and M6

are rather linear compared with the corresponding crystal

ones, they converge at slightly bent (M4, Au···Au···Au=171.18)

and zigzag (M6, Au···Au···Au=160.48) structures, which are in-

terestingly in contrast with the linear Au₄alignment of M5

(Au···Au···Au=180.08), all the structures being reminiscent of

Figure 8. Perspective views showing interactions of syn-[Au₄(rac-

dpmppm)₂]⁴⁺with a) Cl^ꢀ(6b), and b) TfO^ꢀ(6 f) ions. The tetragold parts and

the counter anions are illustrated with space-filling models.

are mainly composed of anti-bonding d_sorbitals of the four

Au ions (5d_s*s*s*) and the LUMOs are derived from the bonding

interactions of the p_sorbitals of the four Au atoms (6p_sss

)

Chem. Eur. J. 2014, 20, 1577 – 1596

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1585

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in the acetonitrile (Figure 9d–i, Table 4). In the solid state at

room temperature, intense visible (blue to bluish-green) emis-

sions were observed with quantum yields of 0.67–0.85 (Figur-

es 9d–f and 11), and their energies are red-shifted 485–494

(6d–f) <(475–)508 (4d–f) <513–515 nm (5d–f), depending on

the Au₄structures. In CH₂Cl₂(298 K), they are also luminous

with the emission band maxima around 500 nm with a weak

band at 440 nm (for 4d–f and 5d–f). When the solutions were

exposed to air, the emission at 500 nm was slowly quenched,

whereas the higher energy band (ca. 440 nm), presumably an

intraligand fluorescence, was almost intact. In CH₃CN (298 K),

intense bluish-green emissions were observed at 491–520 nm

with microsecond lifetimes (5.9–7.4 ms) (Figure 9g–i). In the

light of the long lifetime and the DFT calculations, the emission

Table 4. Photophysical data of complexes 4b–f, 5d–f, and 6b–f

Medium l_abs[nm]

l_em

t

F_em

(e [dm³mol^ꢀ1cm^ꢀ1]) [nm] [ms]

syn-[Au₄(meso-dpmppm)₂]XX’₃

4a (X=X’=Cl)

CH₃CN

CH₂Cl₂

solid

398 (4.73ꢂ10⁴)

382 (2.59ꢂ10⁴)

486 1.0 0.003

476 1.9

510

512 4.6 0.02

509 4.4

0.01

4b (X=Cl, X’=PF₄) CH₃CN

383 (4.14ꢂ10⁴)

372 (2.32ꢂ10⁴)

CH₂Cl₂

solid

484

0.09

4c (X=Cl, X’=BF₄) CH₃CN

388 (2.65ꢂ10⁴)

367 (1.95ꢂ10⁴)

503 4.9 0.01

504 3.4

481

520 6.8 0.45

510 4.0

508

508 7.4 0.83

501 4.2

504

511

507 4.0

475

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

0.17

4d (X=X’=PF₆)

4e (X=X’=BF₄)

4 f (X=X’=TfO)

384 (1.02ꢂ10⁵)

370 (3.23ꢂ10⁴)

0.76

3

is assigned to come from a triplet excited state, [5d_s*s*s*6p_sss].

368 (3.89ꢂ10⁴)

363 (3.87ꢂ10⁴)

1

The Stokes shifts between the [5d_s*s*s*!6p_sss] absorption and

³[5d_s*s*s*!6p_sss] emission are about 6.4–7.7ꢂ10³cm^ꢀ1, compa-

rable to those observed in [Au₃(dcmp)₂]³⁺(ca. 7.5–8.0ꢂ

10³cm^ꢀ1)^[7b]and K₄[Pt₂(P₂O₅H₂)₄] (7.8ꢂ10³cm^ꢀ1).^[18]The emis-

sion bands of the tetragold(I) complexes are significantly red-

shifted in energy relative to those of the trigold(I) complexes

[Au₃(dcmp)₂]³⁺(442–452 nm)^[7b]and the digold(I) complexes

[Au₂(dcpm)₂]²⁺(360–368 nm); this shift should be ascribed to

a smaller 5d_s*!6p_sgap for higher nuclearity of the complexes

as discussed by Che et al.^[7b]The lowest triplet (T₁) excited

states for M4–M6 were analyzed by DFT optimizations with

MPWPW91/SDD methods (Table 5). In the T₁excited states, a-

HOMO and a-HOMOꢀ1 correspond to LUMO and HOMO of

the S₀ground states, respectively (Figure 10d, and Figur-

es S10–S12 in the Supporting Information), clearly indicative of

its generation through intersystem crossing from the

¹[5d_s*s*s*6p_sss] state. The Au···Au distances (2.748–2.982 ꢀ) in

the T₁states are appreciably shorter than those in the S₀states

(3.064–3.132 ꢀ) owing to singly occupied 6p_sssbonding and

5d_s*s*s*antibonding orbitals. The calculated emission wave-

lengths are 453 (M6), 459 (M4), and 462 nm (M5) (Figure S13b

in the Supporting Information); the order is roughly in agree-

ment with the observed data.

0.72

373 (3.89ꢂ10⁴)

366 (1.17ꢂ10⁵)

5.9 0.89

0.85

anti-[Au₄(meso-dpmppm)₂]X₄

5d (X=PF₆)

5e (X=BF₄)

5 f (X=TfO)

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

383 (9.55ꢂ10⁴)

387 (1.29ꢂ10⁵)

514 6.7 0.36

511

515

4.7

0.78

382 (6.76ꢂ10⁴)

387 (6.46ꢂ10⁴)

514 6.9 0.38

512 3.0

513

512 6.1 0.33

514 5.1

515

0.68

378 (4.47ꢂ10⁴)

389 (7.18ꢂ10⁴)

0.67

syn-[Au₄(rac-dpmppm)₂]X₂X’₂

6a (X=X’=Cl)

CH₃CN

CH₂Cl₂

solid

369 (1.90ꢂ10⁴)

375 (3.40ꢂ10⁴)

510 2.8 0.02

495 1.5

505

499 1.6 0.05

490 3.9

0.08

6b (X=Cl, X’=PF₆) CH₃CN

345 (2.40ꢂ10⁴)

367 (1.50ꢂ10⁴)

CH₂Cl₂

solid

483

0.24

0.05

[a]

6c (X=Cl, X’=BF₄) CH₃CN

370 (3.71ꢂ10⁴)

369 (2.82ꢂ10⁴)

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

CH₃CN

CH₂Cl₂

solid

503 3.6

487

501 6.7 0.85

490 3.5

6d (X=X’=PF₆)

6e (X=X’=BF₄)

6 f (X=X’=TfO)

352 (4.39ꢂ10⁴)

358 (3.39ꢂ10⁴)

In order to obtain more accurate theoretical consideration,

the DFT full optimization for syn-[Au₄(meso-dpmppm)₂]⁴⁺, anti-

[Au₄(meso-dpmppm)₂]⁴⁺, and syn-[Au₄(rac-dpmppm)₂]⁴⁺were

carried out with B3LYP-D^[19,20]functionals with Lanl2tzf^[21](Au)

and 6-31G* (others) basis sets for the S₀ground and lowest T₁

excited states (the initial coordinates were derived from 4d,

5e, and 6e, respectively). The PCM model^[22]was employed to

approximate the solvent dichloromethane. The converged

structures for the S₀states are in agreement with the respec-

tive crystal structures (Table 6 and Figures S14–16 in the Sup-

porting Information), which still showed slight elongation of

Au···Au distances by 0.08–0.28 ꢀ, although the hybrid function-

als include an empirical correction term for long-range disper-

sion interactions.^[20]Notably, the qualitative order of the

Au···Au distances (5e<6e<4d) is consistent with the ob-

served distances. The characters of HOMO and LUMO are es-

sentially identical to the results from the primitive calculations

on M4–M6, consisting of 5d_s*s*s*and 6p_sssorbitals, respective-

ly, partially mixed with the ligand orbitals (Figure 12). The DFT

485

0.75

353 (4.19ꢂ10⁴)

358 (5.13ꢂ10⁴)

500 6.7 0.97

492 4.1

494

491 7.1 0.75

486 3.5

485

0.85

356 (5.45ꢂ10⁴)

360 (8.91ꢂ10⁴)

0.67

[a] Not observed.

their parent crystal structures. As a result, the HOMO–LUMO

energy gap of M5 is smaller by 0.04–0.07 eV than those of M4

and M6 (Figure S13a in the Supporting Information). The

linear Au₄arrangement is likely to destabilize the 5d_s*s*s*anti-

bonding interaction and instead stabilize the 6p_sssin-phase or-

bital, and thus, responsible for the lower absorption energy of

5d–f than those of 4d–f and 6d–f.

Complexes 4d–f, 5d–f, and 6d–f containing large counter

anions are all strongly luminescent both in the solid states and

Chem. Eur. J. 2014, 20, 1577 – 1596

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Figure 9. Absorption spectra of a) syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d, blue), BF₄(4e, red), TfO^ꢀ(4 f, green), b) anti-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d,

blue), BF₄(5e, red), TfO^ꢀ(5 f, green), and c) syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d, blue), BF₄(6e, red), TfO^ꢀ(6 f, green), in CH₂Cl₂at room temperature.

Solid-state emission spectra of d) syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d, blue), BF₄(4e, red), TfO^ꢀ(4 f, green), e) anti-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d,

blue), BF₄(5e, red), TfO^ꢀ(5 f, green), and f) syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d, blue), BF₄(6e, red), TfO^ꢀ(6 f, green), at room temperature. Solution-state

emission spectra of g) syn-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(4d, blue), BF₄(4e, red), TfO^ꢀ(4 f, green), h) anti-[Au₄(meso-dpmppm)₂]X₄(X=PF₆(5d, blue), BF₄

(5e, red), TfO^ꢀ(5 f, green), and i) syn-[Au₄(rac-dpmppm)₂]X₄(X=PF₆(6d, blue), BF₄(6e, red), TfO^ꢀ(6 f, green), in CH₃CN at room temperature.

Table 5. Optimized structures and photophysical data of the ground sin-

glet (S₀) and lowest triplet (T₁) excited states for model complexes, syn-

[Au₄(meso-L)₂]⁴⁺(M4), anti-[Au₄(meso-L)₂]⁴⁺(M5), and syn-[Au₄(rac-L)₂]⁴⁺

(M6) (L=H₂PCH₂P(H)CH₂P(H)CH₂PH₂) from DFT calculations.

M4

M5

M6

S₀

T₁

S₀

T₁

S₀

T₁

Au_out···Au_in[ꢀ]

Au_in···Au_in’[ꢀ]

av Au···Au [ꢀ]

Au_outꢀP [ꢀ]

3.127

3.132

3.130

2.406

2.417

171.1

177.2

177.4

3.08

2.973

2.982

2.978

2.442

2.431

174.0

165.7

171.7

3.099

3.094

3.097

2.412

2.416

180.0

176.3

178.4

3.04

2.949

2.821

2.885

2.447

2.429

180.0

165.5

172.5

3.124

3.064

3.094

2.406

2.423

160.4

177.1

172.8

3.11

2.961

2.784

2.873

2.443

2.433

172.3

165.5

164.5

Au_inꢀP [ꢀ]

Au_out···Au_int···Au_in[8]

P-Au_out-P_’[8]

P-Au_in-P_’[8]

DE_HOMOꢀLUMO[eV]

calcd l_abs[nm]^[a]

calcd l_em[nm]^[b]

365

459

365

462

361

453

Figure 10. MO surface diagrams for a) LUMO and b) HOMO of syn-

[Au₄(meso-C₃H₁₂P₄)₂]⁴⁺(M4, singlet ground state S₀) and c) a-HOMO and

d) a-HOMOꢀ1 of syn-[Au₄(meso-C₃H₁₂P₄)₂]⁴⁺(M4, lowest triplet excited state

T₁).

[a] Calculated with TD-DFT methods on the S₀optimized structures with

with MPWPW91/SDD. [b] Calculated from energy difference,DSCF=E(T₁)

-E(S₀) on the T₁optimized structures.

Chem. Eur. J. 2014, 20, 1577 – 1596

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Figure 11. Photographs of solid samples 4d–f, 5d–f, and 6d–f under UV ir-

radiation (365 nm) at room temperature.

Figure 12. MO surface diagrams for HOMO and LUMO of syn-[Au₄(meso-

dpmppm)₂]⁴⁺(4d), anti-[Au₄(meso-dpmppm)₂]⁴⁺(5e), and syn-[Au₄(rac-

dpmppm)₂]⁴⁺(6e) in the ground state S₀, the structures of which are opti-

mized by DFT calculations with RB3LYP-D functionals.

single-point calculations on the crystal structures with the

same methods B3LYP-D/Lanl2tzf (Au) and 6-31G* (others) also

indicated the similar HOMO–LUMO characters. The HOMO–

LUMO energy gaps for the optimized and X-ray structures ex-

hibited the same tendency of 5e (anti-(meso-dpmppm)₂)<

4d(syn-(meso-dpmppm)₂)<6e(anti-(rac-dpmppm)₂) as ob-

served for the model compounds. The TD-DFT calculations on

the optimized and X-ray structures of 4d, 5e, and 6e clearly

indicated that the electronic absorptions around 360–390 nm

are assignable to HOMO–LUMO transitions; the values for the

optimized structures, 332 (f=0.771) (4d), 365 (f=1.092) (5e),

and 325 nm (f=0.588) (6e), are relatively comparable with

those for the X-ray structures, 366 (f=0.933) (4d), 378 (f=

1.173) (5e), and 366 nm (f=0.849) (6e) (Table 6). The structures

for the lowest triplet excited states (T₁) of 4d, 5e, and 6e were

optimized with UB3LYP-D/Lanl2tzf (Au) and 6–31G* (others), in

which the Au···Au distances are appreciably reduced due to

3

partial bonding interactions of the [5d_s*s*s*6p_sss] excited state;

average Au···Au=2.825 ꢀ (4d), 2.861 (5e), and 2.811 (6e). In

the T₁states of 4d and 6e, the average Au···Au distances are

reduced dramatically by 0.324 (4d) and 0.302 ꢀ (6e) with dis-

tinct increases of the average Au···Au···Au angles by 14.6 (4d)

and 26.78 (6e), showing a light-

induced elasticity of the bent

and zigzag Au₄chains. On the

Table 6. Optimized structures and photophysical data of the ground singlet (S₀) and lowest triplet (T₁) excited

states for syn-[Au₄(meso-dpmppm)₂]⁴⁺(4d), anti-[Au₄(meso-dpmppm)₂]⁴⁺(5e), and syn-[Au₄(rac-dpmppm)₂]⁴⁺

(6e) from DFT calculations.

other hand, the structural differ-

ence between the T₁and S₀

states of 5e is quite small with

D(av Au···Au)=0.156 ꢀ and D(av

Au···Au···Au)=0.58 owing to the

linearly constrained Au₄struc-

ture. The SCF energy differences

between the S₀and T₁states at

the T₁optimized structures

afford emissions originating

from the ³[5d_s*s*s*6p_sss] excited

states at 476 (4d), 479 (5e), and

473 nm (6e) (Figure S17 in the

Supporting Information), and the

TD-DFT methods on the T₁opti-

mized structures gave values of

486 (4d), 488 (5e), and 481 nm

(6e) (Table 6); these results show

a same order of the observed

emission of 492 (6e) <510 (4d)

<512 nm (5e) and can be com-

pared with 4d–f (501–510 nm),

5d–f (511–514 nm), and 6d–f

(486–492 nm) in dichlorome-

4d

5e

6e

S₀

T₁

S₀

T₁

S₀

T₁

Au1···Au2 [ꢀ]

Au2···Au3_’[ꢀ]

Au3···Au4_’[ꢀ]

av Au···Au [ꢀ]

3.256

3.067

3.123

3.149

2.968

2.336

2.330

133.3

164.6

149.0

153.6

171.8

173.4

4.33^[a](3.95)^[b]

332^[a,c](366)^[b,c]

370

476^[a,d](486)^[b,e]

510

2.857

2.744

2.875

2.825

3.042

2.967

3.043

3.017

2.916

2.339

2.330

178.5

179.2

178.9

176.6

177.3

177.6

3.95^[a](3.81)^[b]

365^[a,c](378)^[b,c]

387

479^[a,d](488)^[b,e]

512

2.897

2.789

2.897

2.861

3.112

3.100

3.127

3.113

2.953

2.335

2.331

133.1

129.8

131.5

145.4

174.2

172.6

4.45^[a](3.97)^[b]

325^[a,c](366)^[b,c]

358

473^[a,d](481)^[b,e]

492

2.850

2.736

2.848

2.811

obsd. av Au···Au [ꢀ]

Au_outꢀP [ꢀ]

2.346

2.339

158.9

168.3

163.6

2.342

2.334

179.2

179.5

179.4

2.349

2.334

157.9

158.5

158.2

Au_inꢀP [ꢀ]

Au1···Au2···Au3 [8]

Au2···Au3···Au4 [8]

av Au···Au···Au [8]

obsd. av Au···Au···Au [8]

P-Au_ou-P_’[8]

170.9

174.4

169.2

174.2

173.9

170.3

P-Au_in-P [8]

DE_HOMO–LUMO[eV]

calcd l_abs[nm]

obsd l_abs[nm] in CH₂Cl₂

calcd l_em[nm]

obsd l_abs[nm] in CH₂Cl₂

[a] For DFT optimized structures with B3LYP-D/Lanl2tzf (Au) and 6–31G*(others). [b] For X-ray determined struc-

tures. [c] Calculated with TD-DFT methods on the S₀optimized structures with B3LYP-D/Lanl2tzf (Au) and 6–

31+G*(others). [d] Calculated from energy difference, DSCF=E(T₁)-E(S₀) on the T₁optimized structures. [e] Cal-

culated with TD-DFT methods on the T₁optimized structures with UB3LYP-D/Lanl2tzf(Au) and 6–31+G*

(others).

Chem. Eur. J. 2014, 20, 1577 – 1596

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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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thane. Interestingly, the photo-

chemical properties are predom-

inantly determined by the

HOMO and LUMO characters of

the Au₄arrays, which are essen-

tially identical in the S₀, S₁, and

T₁states.

Table 7. Photophysical parameters for the emission quenching of 4d,e, 5d,e, and 6d,e by chloride ions at

room temperature in CH₃CN, determined from the Stern–Volmer plots for I₀/I and t₀/t, and UV/Vis titration.

4d

4e

5d

5e

6d

6 f

app

SV

K

[mol^ꢀ1dm³]^[a]

5.7ꢂ10⁵

8.4ꢂ10¹⁰

2.0ꢂ10⁵

2.9ꢂ10¹⁰

2.7ꢂ10⁵

3.2ꢂ10⁵

5.3ꢂ10^ꢀ19

7.9ꢂ10⁵

1.4ꢂ10⁶

1.9ꢂ10¹¹

2.1ꢂ10⁵

2.8ꢂ10¹⁰

3.0ꢂ10⁵

9.7ꢂ10⁵

1.6ꢂ10^ꢀ18

1.5ꢂ10⁶

9.3ꢂ10⁵

1.4ꢂ10¹¹

2.0ꢂ10⁵

3.0ꢂ10¹⁰

1.8ꢂ10⁴

7.5ꢂ10⁵

1.2ꢂ10^ꢀ18

9.7ꢂ10⁵

7.6ꢂ10⁵

1.1ꢂ10¹¹

1.8ꢂ10⁵

2.6ꢂ10¹⁰

5.4ꢂ10⁴

5.8ꢂ10⁵

9.6ꢂ10^ꢀ19

8.1ꢂ10⁵

2.3ꢂ10⁶

3.4ꢂ10¹¹

3.5ꢂ10⁵

5.2ꢂ10¹⁰

2.1ꢂ10⁴

1.5ꢂ10⁶

2.5ꢂ10^ꢀ18

1.9ꢂ10⁶

1.0ꢂ10⁶

1.5 x10¹¹

6.3ꢂ10⁵

9.4 x10¹⁰

5.5ꢂ10⁴

5.2ꢂ10⁵

8.6ꢂ10^ꢀ19

1.2ꢂ10⁶

k^a_q^pp[mol^ꢀ1dm³s^ꢀ1

K^D_SV[mol^ꢀ1dm³]^[c]

k^D_q[mol^ꢀ1dm³s^ꢀ1

]

[b]

[d]

]

K^S_AB[mol^ꢀ1dm³]^[e]

K^S_P[mol^ꢀ1dm³]^[f]

V_q[dm³]^[g]

Emission quenching by chlo-

ride anions

K^D_SV+K^S_AB+K^S_P

[a] Calculated from the extrapolated line with I₀/I=1+K^a_S^p_V^p[Cl^ꢀ] at very low quencher concentration range.

app

[b] Derived with a tentative equation of K =k_q^appt₀(t₀is lifetime without quencher). [c] Derived from the

The solid-state emissions are ap-

preciably quenched in com-

plexes 4b (F=0.09) and 4c

(F=0.17), referenced to 4d

(F=0.76) and 4e (F=0.72),

presumably due to interaction of

the Au₄chain with a chloride

SV

Stern–Volmer plots t₀/t=1+K^D_SV[Cl^ꢀ] (t₀and t are lifetime without and with quencher, respectively). [d] Derived

with an equation of K^D_SV=k_q^Dt₀(t₀is lifetime without quencher). [e] K_A^S_Bis the first chloride binding constants for

syn/anti-[Au₄(meso/rac-dpmppm)₂]⁴⁺+Cl^ꢀQ{syn/anti-[Au₄(meso/rac-dpmppm)₂]Cl}³⁺determined by titration

with adding nBu₄NCl monitored by UV/Vis spectra. [f] Derived from the Stern–Volmer plots for I₀/I with an

equation of ln{I₀/[I(1+K^D_SV[Cl^ꢀ])(1+K^S_AB[Cl^ꢀ])]}=K_P^S[Cl^ꢀ]. [g] K^S_P=V_qN_a; V_qis volume for the sphere of effective

quenching, and N_ais Avogadro’s constant.

anion as observed in the crystal structure of 4b (Figure 3a).

Even in acetonitrile, the intensities of the metal-centered emis-

sion for 4d (F=0.45) and 4e (F=0.83) distinctly decreased

when nBu₄NCl was added to the solution (Figure 13a and Fig-

ure S18 in the Supporting Information). Similar sensitive

quenching by chloride ions was also observed for the other

isomeric Au₄chains of 5d,e and 6d,e (Figure S18 in the Sup-

porting Information). In particular, more than 90% of emission

for 6d,e was effectively quenched by adding 0.5 equivalents of

Cl^ꢀat a concentration ca. 1.5 mm. These results revealed that

the luminous tetragold(I) units supported by two dpmppm li-

gands have the potential ability to detect chloride anions in

the solution state, which perturbed their metal-centered emis-

sion. Che et al. reported similar halide-quenching phenomena

of [Au₂(dcpm)₂]²⁺and [Au₃(dcmp)₂]³⁺, which were elucidated

to result from substrate-binding of their ³[d_s*s*p_ss] excited

states.^[7]

The observed decreases in emission intensity with varying

[Cl^ꢀ] do not follow the linear Stern–Volmer equation, I₀/I=1+

K_SV[Cl^ꢀ], and the I₀/I plots show upward curvatures at high

quencher concentrations (Figure 13b (black circles), Figure S18

in the Supporting Information), demonstrating that simultane-

ous dynamic and static quenching processes are involved in

the present systems.^[23a]The apparent Stern–Volmer constants

are derived from the extrapolated line at very low quencher

app

concentration range as K =5.7ꢂ10⁵–2.3ꢂ10⁶mol^ꢀ1dm³(Fig-

SV

ure 13b (blue line), Figure S18, Table 7). These values result in

apparent quenching rate constants, k^a_q^pp=8.4ꢂ10¹⁰–3.4ꢂ

10¹¹mol^ꢀ1dm³s^ꢀ1(K_SV=k_qt₀, t₀is lifetime without quencher),

which are appreciably higher than the diffusion-controlled

limit (ca. 10¹⁰mol^ꢀ1dm³s^ꢀ1) and suggested that static quench-

Figure 13. a) Emission spectral changes of syn-[Au₄(meso-dpmppm)₂][BF₄]₄

(4e) in CH₃CN at room temperature by successive titration with 0.1 equiv of

[nBu₄N]Cl. b) Plot of I₀/I at 508 nm versus [Cl^ꢀ] (black circle), along with an

extrapolated line at very low quencher concentration (blue),

I₀/I=(1+K^a_S^p_V^p[Cl^ꢀ]), and the Stern–Volmer plot for t₀/t (red circle) along with

a fitted line of t₀/t=(1+K_S^D_V[Cl^ꢀ]). c) Plot of ln{I₀/[I(1+K^D_SV[Cl^ꢀ])(1+K_A^S_B[Cl^ꢀ])]}

versus [Cl^ꢀ], the slope of which give a fitted value of K_P^Sfor equation of

I₀/I=(1+K^D_SV[Cl^ꢀ])(1+K_A^S_B[Cl^ꢀ])exp(K^S_P[Cl^ꢀ]).

ing processes are also substantial. In general, static quenching

involves two mechanisms, 1) static binding between chromo-

phore and quencher in ground states and 2) static bonding in

excited states of chromophore. To evaluate simultaneous dy-

namic and static quenching, the former case 1 is treated by an

equation of [Equation (1)], in which K^D_SV[mol^ꢀ1dm³] is the

Chem. Eur. J. 2014, 20, 1577 – 1596

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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper

Stern–Volmer constant for dynamic quenching, and K_A^S_B

[mol^ꢀ1dm³] is the static ground-state bimolecular binding con-

stant.

I₀=I ¼ ð1 þ K^D_SV½Cl^ꢀꢁÞð1 þ K_A^S_B½Cl^ꢀꢁÞ

ð1Þ

In the latter case 2, Perrin’s sphere of effective quenching

model is often used to approximate the static quenching of

excited species, and then the plot for I₀/I can be represented

by Equation (2) in which K^S_P[mol^ꢀ1dm³] (=V_qN_a) is static

quenching constant for excited chromophore, V_q[dm³] is

volume for the sphere of effective quenching, and N_ais Avoga-

dro’s constant.^[23a]

I₀=I ¼ ð1 þ K^D_SV½Cl^ꢀꢁÞexpðK^S_P½Cl^ꢀꢁÞ

ð2Þ

Notably, K^D_SVcan be determined from Stern–Volmer plot for

t₀/t (t₀and t are lifetimes without and with quencher), and

K^S_ABis determined by electronic absorption spectral titration.

At first, the Stern–Volmer plots for t₀/t were analyzed with

t₀/t=1+K^D_SV[Cl^ꢀ] (Figure 13b, red) to afford K_S^D_V=1.8–6.3ꢂ

10⁵mol^ꢀ1dm³(Table 7, Figure 13b (red line), Figure S18 in the

Figure 14. a) Absorption spectral changes of syn-[Au₄(meso-dpmppm)₂][BF₄]₄

(4e) in CH₃CN at room temperature by titrating with [nBu₄N]Cl and b) plot

of A₀/(A₀ꢀA) versus 1/[Cl^ꢀ], which afford the ground-state binding constant

Supporting Information). The obtained K^D_SVvalues are notably

app

SV

smaller than the apparent Stern–Volmer constant K

(5.7ꢂ

K^S_ABfor syn-[Au₄(meso-dpmppm)₂]⁴⁺+Cl^ꢀQ{syn-[Au₄(meso-dpmppm)₂]Cl}³⁺

.

10⁵–2.3ꢂ10⁶mol^ꢀ1dm³) (Table 7, Figure 13b (blue line), Fig-

ure S18 in the Supporting Information), and result in the

quenching rate constants k^D_qof 2.6–9.4ꢂ10¹⁰mol^ꢀ1dm³s^ꢀ1,

which are comparable or slightly higher than diffusion con-

trolled rate constants. The ground-state binding constants for

I₀=I ¼ ð1 þ K^D_SV½Cl^ꢀꢁÞð1 þ K_A^S_B½Cl^ꢀꢁÞexpðK^S_P½Cl^ꢀꢁÞ

ð3Þ

Since exp(K^S_P[Cl^ꢀ])ꢂ1+K^S_P[Cl^ꢀ] at low quencher concentra-

the

first

chloride

association,

syn/anti-[Au₄(meso/rac-

app

tions, the extrapolated apparent Stern–Volmer constant K

SV

dpmppm)₂]⁴⁺+Cl^ꢀQ{syn/anti-[Au₄(meso/rac-dpmppm)₂]Cl}³⁺

,

should approximately correspond to a summation K^D_SV+K_A^S_B

+

K^S_P. By using the K^D_SVand K_A^S_Bvalues, the static quenching con-

stants for the excited species (K^S_P) were derived according to

Equation (3); namely, the plots of ln{I₀/[I(1+K^D_SV[Cl^ꢀ])(1+

K^S_AB[Cl^ꢀ])]} versus [Cl^ꢀ] exhibited a linear correlation, and from

the slope K^S_Pare estimated as 3.2ꢂ10⁵–1.5ꢂ10⁶mol^ꢀ1dm³

(Table 7 and Figure 13, and Figure S18 in the Supporting Infor-

mation), which lead to unusually large sphere volumes of ef-

fective quenching V_q. From these results, the phosphorescence

of 4d,e–6d,e is estimated to quench through simultaneous

static and dynamic processes; in particular, static association of

chloride ions to the excited-state Au₄centers is significant for

the sensitive quenching. The contribution of ground-state

static quenching for 4d,f is notably higher than that for 5d,f

and 6d,f. The detailed mechanisms for the excited-state

quenching will be investigated in our subsequent studies.

were determined by UV/Vis titration with nBu₄NCl to afford

K^S_AB=1.8ꢂ10⁴–3.0ꢂ10⁵mol^ꢀ1dm³(Table 7, Figure 14, Fig-

ure S19 in the Supporting Information). These values are signif-

icantly larger than that found for [Au₂(dcpm)₂]²⁺with Cl^ꢀ(1.8ꢂ

10³mol^ꢀ1dm³)^[7a]and slightly larger than those foudn for for

[Au₂(dmpm)₂]²⁺and [Au₂(dmpe)₂]²⁺(ca. 10⁴mol^ꢀ1dm³).^[24]It

should be noted that the K^S_ABvalues for 4d,e (2.7–3.0ꢂ

10⁵mol^ꢀ1dm³) are one order of magnitude larger than those

of 5e,d and 6e,d (1.8–5.5ꢂ10⁴mol^ꢀ1dm³), which may be at-

tributed to high affinity of the bent Au₄pocket toward a chlo-

ride ion as observed in the X-ray structure of 4b.

Even by using the independently determined K^D_SVand K_A^S_B

values, the observed I₀/I data could not be fitted to Equa-

tion (1). On the other hand, the K^S_Pvalues obtained by using

Equation (2) with the pre-determined K^D_SVwere sufficiently

large (ca. 10⁵–10⁶mol^ꢀ1dm³), suggesting the effective sphere

of binding for the excited chromophore is the main quenching

process. Nevertheless, the K^S_Pvalues for 4d,e were fairly com-

parable to the K^S_ABvalues (ca. 10⁵mol^ꢀ1dm³), while those for

5d,e and 6d,e were one order of magnitude larger than the

corresponding K_A^S_Bvalues (ca. 10⁴mol^ꢀ1dm³). In the light of

these preliminary results, both the ground- and excited-state

static quenching processes were combined^[23b]with the Stern–

Volmer dynamic process and the I₀/I data were analyzed by

using Equation (3).

Conclusion

In the present study, a series of Au^I₄complexes with new tetra-

phosphine ligands, meso- and rac-bis[(diphenylphosphinome-

thyl)phenylphosphino]methane (meso- and rac-dpmppm) were

synthesized to demonstrate that the tetranuclear Au^Ialign-

ment varies depending on syn- and anti-arrangements of the

two dpmppm ligands as bent (syn-[Au₄(meso-dpmppm)₂]⁴⁺

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(4)), linear (anti-[Au₄(meso-dpmppm)₂]⁴⁺(5)), and zigzag (syn-

[Au₄(rac-dpmppm)₂]⁴⁺(6)) structures. Complexes 4–6 with

non-coordinative large anions (PF₆^ꢀ, BF₄^ꢀ, TfO^ꢀ) are strongly

luminescent in the sold state (l_max=475–508 (4), 513–515 (5),

485–494 nm (6)) with quantum yields F=0.67–0.85, which

resolution mass spectrometer or a JEOL JMS-T100 LC high-resolu-

tion mass spectrometer with positive ionization mode.

Syntheses

3

Bis[(trimethylsilylmethyl)phenylphosphino]methane (tmsmppm):

In a dry ice-methanol bath, nBuLi–hexane solution (1.61m, 44 mL,

71 mmol) in THF (20 mL) was added slowly to a solution of bis(di-

phenylphosphino)methane (7.32 g, 31.5 mmol) in THF (100 mL).

The reaction mixture was gradually warmed to room temperature

to result in a clear yellow-orange solution after stirring for 1 h.

Then, chloromethyltrimethylsilane (9.7 mL, 69 mmol) in THF

(20 mL) was added to the solution, which was cooled in a dry ice-

methanol bath. The reaction mixture was warmed again to room

temperature and then refluxed at 808C for 1 h to give a pale

yellow suspension. After cooling to room temperature, degassed

H₂O (30 mL) was added to the mixture. The resultant organic layer

was extracted with diethyl ether and the solvent was removed

under reduced pressure to afford clear oil of bis[(trimethylsilylme-

thyl)phenylphosphino]methane (tmsmppm) (11.8 g, yield: 92%).

¹H NMR (300 MHz, CDCl₃, RT): d=7.59–7.23 (m, 10H; Ph), 2.03 (m,

2H; CH₂), 1.40–1.23 (m, 1H; CH₂), 0.23–0.05 ppm (m, 18H; SiMe₃);

³¹P{¹H} NMR (121 MHz, CDCl₃, RT): d=ꢀ34.2 (s, 1P), ꢀ35.3 ppm (s,

1P); ESI-MS (in CH₃CN): m/z: 405.192 [tmsmppm+H]⁺(calcd:

405.175).

were assigned to phosphorescence from the [5d_s*s*s*6p_sss] ex-

cited state of the cluster centers on the basis of DFT calcula-

tions as well as the long lifetimes. The emission energy clearly

relates to the HOMO (5d_s*s*s*)ꢀLUMO (6p_sss) energy gaps,

which are systematically altered depending on the Au₄core

structures. In the light of DFT optimization of 4d, 5e, and 6e

in the lowest triplet excited states, an interesting light-induced

elasticity of the bent and zigzag Au₄chains was observed for

4d and 6e, while the structural difference between the T₁and

S₀states of 5e is quite small, owing to the linearly constrained

Au₄structure. In addition, the intense emission was sensitively

quenched by chloride anions through both the dynamic and

static quenching processes. For the static quenching, effective

sphere binding of chloride ions to the Au₄excited species is

assumed to be predominant for the linear and zigzag Au₄

chains of 5 and 6, while formation of ground-state non-lumi-

nescent complexes is also substantial for the quenching of the

bent Au₄chains of 4. These results are quite interesting as

strongly luminescent properties intrinsic to the fine tunable

linear tetragold(I) chains, and could lead to their application

meso-Bis[(diphenylphosphinomethyl)phenylphosphino]methane

(meso-dpmppm): A mixture of Ph₂PCl (12 mL, 58 mmol) and

tmsmppm (11.8 g, 29.1 mmol) was refluxed at 958C for 1 h to give

a white viscous liquid. After cooling down to room temperature,

the remaining chlorotrimethylsilane was removed under reduced

pressure to give a meso-rich mixture of dpmppm. The mixture was

dissolved in acetone and cooled at 28C to afford pure white

powder of meso-dpmppm, which was washed with methanol and

dried under vacuum (9.22 g, yield: 50%). IR (KBr): n˜ =1433 (s, PꢀC),

3

for anion sensing systems by utilizing their [5d_s*s*s*6p_sss] excit-

ed states.

Experimental Section

1

1096 (w), 774 (w), 732 (s), 694 cm^ꢀ1(s); H NMR (300 MHz, in CDCl₃,

2

General procedures

RT): d=7.70–7.19 (m, 30H; Ph), 2.56 (d, J_HH=13 Hz, 2H), 2.42 (d,

2

²J_HH=13 Hz, 2H), 2.37 (d, ²J_HH=16 Hz, 1H), 2.20 ppm (d, J_HH

=

All reactions were carried out under a nitrogen atmosphere by

using standard Schlenk techniques. Solvents were dried by stan-

dard procedures and freshly distilled prior to their use. Other re-

agents were of the best commercial grade and no further purifica-

14 Hz, 1H); ³¹P{¹H} NMR (121 MHz, in CDCl₃, RT): d=ꢀ23.0 (m, 2P;

P_out), ꢀ34.7 ppm (m, 2P; P_in) (²J_P=117.06 Hz, ²J_PinPin’=92.10 Hz,

_inP_out

6

⁴J_P

=3.85 Hz, J_P

=0.09 Hz, simulated by gNMR with AA’BB’

_outP_in’

_outP_out’

system); ESI-MS (in CH₃CN): m/z: 629.199 [dpmppm+H]⁺(calcd:

tions

were

performed.

Bis(phenylphosphino)methane,^[8c,12]

629.184).

[AuCl(PPh₃)],^[25]and [AuCl(tht)] (tht=tetrahydrothiophene)^[25]were

prepared according to the literature procedures. ¹H NMR spectra

were recorded on a Varian Gemini 2000 instrument or a Bruker AV-

300N spectrometers at 300 MHz, and the chemical shifts are refer-

enced to the residual resonances of the deuterated solvent. ³¹P{¹H}

NMR spectra were recorded on the same instruments at 121 MHz

with chemical shifts calibrated to 85% H₃PO₄as an external refer-

ence. Electronic absorption spectra were recorded on a Shimadzu

UV-3000 and HP Agilent 8453 spectrophotometers in dichlorome-

thane or acetonitrile. The solution and solid-state emission spectra

were measured on a Shimadzu RF-5300PC spectrofluorometer, or

JASCO FP-6600 and FP-6200 spectrofluorometers. Solvents (spec-

troscopic-grade acetonitrile and dichloromethane) were degassed

by repeated freeze-pump-thaw procedures under nitrogen. The

quantum yields for solid-state and acetonitrile solution samples

were determined by the measurements at room temperature

using ILF-533 (100 mm diameter) integrating photometer. Lumines-

cence decay curves were measured with N₂laser (337 nm) on a Ha-

meso/rac-Bis[(diphenylphosphinomethyl)phenylphosphino]me-

thane mixture (meso/rac-dpmppm): The white solid of meso-

dpmppm (200 mg, 0.32 mmol) was heated at 1658C for about 1 h

under an argon atmosphere. Then, the mixture was cooled to

room temperature to afford white oily product of an approximate

1

1:1 mixture of meso- and rac-dpmppm, which was analyzed by H

and ³¹P{¹H} NMR spectra.

[Pd₂Cl₄(rac-dpmppm)]·0.5CH₂Cl₂(1·0.5CH₂Cl₂): The 1:1 mixture of

meso- and rac-dpmppm (derived from 500 mg (0.80 mmol) of

meso-dpmppm) was dissolved in CH₂Cl₂(13 mL) at room tempera-

ture, and a portion of [PdCl₂(cod)] (671 mg, 2.35 mmol) was added

to the solution. After stirring for 30 s, white powder was precipitat-

ed and the resultant pale orange suspension was further stirred for

12 h. The product of [Pd₂Cl₄(rac-dpmppm)]·0.5CH₂Cl₂was separat-

ed by filtration, washed with CHCl₃(3 mLꢂ3) and diethyl ether

(3 mLꢂ3), and dried under vacuum (341 mg, yield: 43% vs. meso-

dpmppm). Elemental analysis calcd (%) for C_39.5H₃₇P₄Cl₅Pd₂

(1025.72): C 46.25, H 3.64; found: C 46.63, H 3.59; IR (KBr): n˜ =1435

mamatsu R-928 with

a Jovin-Ybon H-20 monochromator or

1

a Horiba TemPro Fluorescence Lifetime System. IR spectra (KBr)

were recorded on a Jasco FT/IR-410 spectrometer. ESI-TOF-mass

spectra were obtained with an Applied Biosystems Mariner high

(s, PꢀC), 1098 (m), 807 (m), 793 (w), 744 (m), 692 cm^ꢀ1(s); H NMR

(300 MHz, in [D₇]DMF, RT): d=8.39–7.40 (m, 30H; Ph), 4.44 (dt,

J

_HH=2, 6 Hz, 2H), 4.01–3.87 (m, 2H), 3.55–3.40 ppm (m, 2H);

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³¹P{¹H} NMR (121 MHz, in [D₇]DMF, RT): d=19.4 (m, 2P; P_out

17.7 ppm (m, 2P; P_in), (²J_P=45.68 Hz, ²J_P=38.63 Hz, ⁴J_P

)

(m, 4P; P_out), 27.7 ppm (m, 4P; P_inn); ESI-MS (CH₂Cl₂): m/z: 2151.184

=

_outP_in’

[Au₄(dpmppm)₂Cl₃]⁺(calcd: 2151.126).

_inP_out

_inP_in’

6

0.29 Hz, J_P

=0.12 Hz, simulated by gNMR with AA’BB’ system).

_outP_out’

syn-[Au₄(meso-dpmppm)₂Cl][PF₆]₃·CH₂Cl₂

(4b·CH₂Cl₂):

meso-

rac-Bis[(diphenylphosphinomethyl)phenylphosphino]methane

(rac-dpmppm): A solution of NaCN (503 mg, 19.3 mmol) in water

(1.1 mL) was added to a suspension of 1 (51 mg, 0.0052 mmol) in

CH₂Cl₂(7 mL), and the mixture was stirred for 1 h. Then, the organ-

ic layer was separated, washed with degassed water (3 mLꢂ3), and

dried over Na₂SO₄for 2 h. The organic solution was removed by fil-

tration, and the inorganic salts were washed with CH₂Cl₂(3 mLꢂ3).

The extracts were combined and concentrated to dryness under

reduced pressure, resulting in colorless oil of rac-dpmppm in

dpmppm (115 mg, 0.183 mmol) and NH₄PF₆(127 mg, 0.779 mmol)

were added to a solution of [AuCl(PPh₃)] (150 mg, 0.303 mmol) in

CH₂Cl₂(15 mL), and the reaction mixture was stirred for 6 h at

room temperature. The solution was evaporated to dryness. After

washing with diethyl ether, the residue was crystallized from an

acetone/diethyl ether mixed solvent to afford pale yellow crystals

of 4b·CH₂Cl₂(90 mg, yield: 46%). Elemental analysis calcd (%) for

C₇₉H₇₄P₁₁Au₄Cl₃F₁₈(2600.34): C 36.49, H 2.87; found: C 36.78, H 2.79;

IR (KBr pellet): n˜ =1437 (s, PꢀC), 1105 (m), 837 (s, P-F), 795 (m), 739

(s), 687 (s), 557 (s), 520 (m), 511 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=

1

a quantitative yield. H NMR (300 MHz, in CDCl₃, RT): d=7.19–7.75

1

(m, 30H; Ph), 2.50 (dd, 4H; J_PH=32, 13 Hz), 2.45 ppm (s, 2H;);

³¹P{¹H} NMR (121 MHz, in CDCl₃, RT): d=ꢀ23.3 (m, 2P; P_out),

ꢀ34.0 ppm (m, 2P; P_inn), (²J_P=114.21 Hz, ²J_P=105.43 Hz,

372 nm (2.32ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, CD₂Cl₂, RT): d=

7.86–7.95 (m, 60H; Ph), 4.32–4.23 (br, 6H; CH₂), 3.93 (br, 2H; CH₂),

1.81 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=34.5

_inP_out

_inP_in’

6

1

⁴J_P

=3.44 Hz, J_P

=0.12 Hz, simulated by gNMR with AA’BB’

(m, 4P; P_out), 28.1 (m, 4P; P_in), ꢀ144.7 ppm (sept, 3P, PF₆, J_PF

=

_outP_in’

_outP_out’

system).

713 Hz); ESI-MS (CH₂Cl₂): m/z: 2369.227 [Au₄(dpmppm)₂Cl+2PF₆]⁺

(calcd: 2369.116), 1112.090 [Au₄(dpmppm)₂Cl+PF₆]²⁺(calcd:

1112.076), 693.063 [Au₄(dpmppm)₂Cl]³⁺(calcd: 693.062).

[Au₄Cl₄(meso-dpmppm)]·1.5DMF (2·1.5DMF): meso-dpmppm

(115 mg, 0.183 mmol) was added to a suspension of [AuCl(tht)]

(240 mg, 0.748 mmol) in ethanol (8 mL), and the reaction mixture

was stirred at room temperature overnight. The mother liquor was

separated by filtration and the solid was washed with diethyl ether

and dried under vacuum. The colorless product was extracted with

DMF (5 mL), which was passed through a membrane filter. Addi-

tion of diethyl ether to the extract afforded colorless needle crys-

tals of 2·1.5DMF (yield: 184 mg, 76% vs. Au). Elemental analysis

calcd (%) for C_43.5H_46.5N_1.5O_1.5P₄Cl₄Au₄(1667.92): C 31.32, H 2.81, N

1.26; found: C 31.19, H 2.77, N 1.60; IR (KBr): n˜ =1647 (s, DMF),

1437 (s, PꢀC), 1103 (m), 802 cm^ꢀ1(m); ¹H NMR (300 MHz, in

[D₇]DMF, RT): d=7.13–7.93 (m, 30H; Ph), 4.45–4.47 (m, 4H), 4.14–

syn-[Au₄(meso-dpmppm)₂Cl][BF₄]₃(4c): A procedure similar to

that for 4b using NH₄BF₄was adopted for the preparation of 4c.

Crystallization from an acetone/diethyl ether mixed solvent afford-

ed pale yellow powder of 4c (yield: 47%). Elemental analysis calcd

(%) for C₇₈H₇₂P₈Au₄B₃ClF₁₂(2340.20): C 40.02, H 3.10; found: C

39.80, H 3.05; IR (KBr pellet): n˜ =1437 (s, PꢀC), 1103 (s), 1083 (s, Bꢀ

F), 793 (m), 741 (s), 688 (s), 522 (m), 512 cm^ꢀ1(m); UV/Vis (CH₂Cl₂):

l_max(e)=367 nm (1.95ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz,

CD₂Cl₂, RT): d=7.84–7.12 (m, 60H; Ph), 4.8–4.7 (br, 4H; CH₂), 4.4–

4.2 (br, 5H; CH₂), 3.82 (br, 1H; CH₂), 1.73 ppm (br, 2H; CH₂); ³¹P{¹H}

NMR (121 MHz, CD₂Cl₂, RT): d=34.0 (m, 4P; P_out), 27.8 ppm (m, 4P;

P_in); ESI-MS (acetone): m/z: 2254.287 [Au₄(dpmppm)₂Cl+2BF₄]⁺

(calcd: 2254.198), 1083.093 ([Au₄(dpmppm)₂Cl+BF₄]²⁺(calcd:

1083.096), 693.059 [Au₄(dpmppm)₂Cl]³⁺(calcd: 693.062).

4.21 ppm (m, 2H); ³¹P{¹H} NMR (121 MHz, in [D₆]DMSO, RT): d=

2

25.6 (m, 2P; P_out) 22.2 ppm (m, 2P; P_in), (²J_P=54.79 Hz, J_P

=

_inP_in’

_inP_out

56.63 Hz, ⁴J_P

=2.18 Hz, ⁶J_P

=0.15 Hz, simulated by gNMR

_outP_out’

with AA’BB’ system); ³¹P{¹H} NMR (121 MHz, in [D₇]DMF, RT): d=

_outP_in’

syn-[Au₄(meso-dpmppm)₂][PF₆]₄(4d): AgPF₆(49 mg, 0.19 mmol)

was added to a solution of complex 4b·CH₂Cl₂(100 mg, 3.86ꢂ

10^ꢀ2mmol) in acetone (10 mL), and the reaction mixture was

stirred overnight. The solution was filtered and evaporated to dry-

ness. The residue was crystallized from an acetone/diethyl ether

mixed solvent to afford pale yellow crystals of 4d (85 mg, yield:

84%). Elemental analysis calcd (%) for C₇₈H₇₂P₁₂Au₄F₂₄(2624.92): C

35.69, H 2.76; found: C 35.57, H 3.01; IR (KBr pellet): n˜ =1438 (s, Pꢀ

C), 1105 (m), 837 (s, PꢀF), 793 (m), 738 (s), 687 (s), 557 (s), 521 (m),

512 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=370 nm (3.23ꢂ

25.1 (m, 2P; P_out) 20.5 ppm (m, 2P; P_in); ESI-MS (in DMF): m/z:

1520.730 [Au₄Cl₃(dpmppm)]⁺

(calcd: 1520.950), 1484.756

[Au₄Cl₂(dpmppm)ꢀH]⁺(calcd: 1484.973).

[Au₄Cl₄(rac-dpmppm)]·0.25DMF·2CH₂Cl₂(3·0.25DMF·2CH₂Cl₂): By

a procedure similar to that for 2, complex 3·0.25DMF·2CH₂Cl₂

was obtained from rac-dpmppm (30 mg, 0.048 mmol) (yield:

70 mg, 95% vs. Au). Elemental analysis calcd (%) for

C_41.75H_41.75N_0.25O_0.25P₄Cl₈Au₄(1746.41): C 28.71, H 2.41, N 0.20; found:

C 28.41, H 1.98, N 0.11; IR (KBr): n˜ =1647 (s, DMF), 1436 (s, PꢀC),

1104 (m), 796 cm^ꢀ1(m); ¹H NMR (300 MHz, in [D₆]DMSO, RT): d=

7.26–8.07 (m, 30H; Ph), 3.83–3.99 (m, 4H; CH₂), 4.33–4.46 ppm (m,

2H; CH₂); ³¹P{¹H} NMR (121 MHz, in [D₆]DMSO, RT): d=26.7 (m, 2P;

1

10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, [D₆]acetone, RT): d=7.93–7.11

(m, 60H; Ph), 4.92–4.89 (br, 6H; CH₂), 4.45 (br, 4H; CH₂), 3.68 ppm

(br, 2H; CH₂); ³¹P{¹H} NMR (121 MHz, [D₆]acetone, RT): d=36.5 (m,

1

P_out

)

21.4 ppm (m, 2P; P_in) (²J_P=56.66 Hz, ²J_P=48.01 Hz,

4P; P_out), 32.3 (m, 4P; P_in), ꢀ144.4 ppm (sept, 4P; PF₆, J_PF

=

_inP_out

_inP_in’

6

⁴J_P

=1.66 Hz, J_P

=0.05 Hz, simulated by gNMR with AA’BB’

716 Hz); ESI-MS (acetone): m/z: 2479.163 [Au₄(dpmppm)₂+3PF₆]⁺

(calcd: 2479.112), 1167.083 [Au₄(dpmppm)₂+2PF₆]²⁺(calcd:

1167.074), 729.736 [Au₄(dpmppm)₂+PF₆]³⁺(calcd: 729.727).

_outP_in’

_outP_out’

system).

syn-[Au₄(meso-dpmppm)₂Cl]Cl₃·3H₂O (4a·3H₂O): meso-dpmppm

(95 mg, 0.151 mmol) was added to a solution of [AuCl(PPh₃)]

(150 mg, 0.303 mmol) in CH₂Cl₂(10 mL), and the reaction mixture

was stirred for 6 h at room temperature. The color of the solution

changed from colorless to yellow and the solution was evaporated

to dryness. After washing with diethyl ether, the residue was crys-

tallized from an CH₂Cl₂/diethyl ether mixed solvent to afford pale

yellow powder of 4a·3H₂O (110 mg, yield: 67%). Elemental analysis

calcd (%) for C₇₈H₇₈O₃P₈Au₄Cl₄(2240.92): C 41.81, H 3.51; found: C

41.60, H 3.90; IR (KBr pellet): n˜ =1436 (s, PꢀC), 1104 (w), 786 (w),

740 (s), 688 cm^ꢀ1(s); ¹H NMR (300 MHz, CDCl₃, RT): d=7.07–7.87

(m, 60H; Ph), 5.12–5.15 (br, 4H; CH₂), 4.52–4.63 (br, 4H; CH₂),

2.61 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, CDCl₃, RT): d=33.1

syn-[Au₄(meso-dpmppm)₂][BF₄]₄·CH₂Cl₂(4e·CH₂Cl₂): AgBF₄(48 mg,

0.25 mmol) was added to a solution of complex 4c (130 mg, 5.5ꢂ

10^ꢀ2mmol) in CH₂Cl₂(10 mL), and the reaction mixture was stirred

overnight in the dark. The solution was filtered and addition of

Et₂O at 58C gave pale yellow crystals of 4e·CH₂Cl₂(98 mg, yield:

72%). Elemental analysis calcd (%) for C₇₉H₇₄P₈Au₄F₁₆B₄Cl₂(2477.21):

C 38.30, H 3.01; found: C 38.61, H 3.15; IR (KBr pellet): n˜ =1438 (s,

PꢀC), 1104 (br), 1057 (br, BꢀF), 998 (br), 796 (m), 741 (s), 688 (s),

557 (s), 521 cm^ꢀ1(m); UV/Vis (CH₃CN): l_max(e)=368 nm (3.89ꢂ

1

10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, CD₂Cl₂, RT): d=6.98–7.76 (m,

60H; Ph), 4.49–4.61 (br, 6H; CH₂), 3.98–4.03 (br, 4H; CH₂), 3.64–

3.72 ppm (br, 2H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=35.4

Chem. Eur. J. 2014, 20, 1577 – 1596

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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper

(m, 4P; P_out), 31.3 ppm (m, 4P; P_in); ESI-MS (CH₂Cl₂): m/z: 2304.906

[Au₄(dpmppm)₂+3BF₄]⁺

(calcd: 2305.232), 1108.964

[Au₄(dpmppm)₂+2BF₄]²⁺(calcd: 1109.114).

anti-[Au₄(meso-dpmppm)₂][BF₄]₄(5e): AgBF₄(70 mg, 0.36 mmol),

meso-dpmppm (38 mg, 6.0ꢂ10^ꢀ2mmol), and 2,6-xylyl isocyanide

(34 mg, 0.26 mmol) were added to a suspension of 2 (93 mg, 6.0ꢂ

10^ꢀ2mmol) in toluene (10 mL), and the reaction mixture was

stirred overnight in the dark. The solution was filtered and evapo-

rated to dryness. The residue was crystallized from a CH₂Cl₂/diethyl

ether mixed solvent at 48C to yield pale greenish yellow crystals of

5e (37 mg, yield: 25%). Elemental analysis calcd (%) for

C₇₈H₇₂P₈Au₄B₄F₁₆(2392.28): C 39.16, H 3.03; found: C 38.33, H 2.86;

IR (KBr pellet): n˜ =1485 (w), 1438 (s, PꢀC), 1375 (w), 1083 (br, BꢀF),

806 (m), 740 (s), 688 (s), 523 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=

387 nm (6.46ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); UV/Vis (CH₃CN): l_max(e)=382 nm

(6.76ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, CD₂Cl₂, RT): d=6.78–

7.71 (m, 60H; Ph), 4.94 (m, 2H; CH₂), 4.85 (d, J=17 Hz, 4H; CH₂),

4.30 (br, 2H; CH₂), 4.08 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz,

CD₂Cl₂, RT): d=36.1 (m, 4P; P_out), 35.0 ppm (m, 4P; P_in); ESI-MS

(CH₂Cl₂): m/z: 2303.834 [Au₄(dpmppm)₂+3BF₄ꢀH]⁺(calcd:

syn-[Au₄(meso-dpmppm)₂][TfO]₄·0.5CH₂Cl₂(4 f·0.5CH₂Cl₂): NH₄OTf

(99 mg, 0.59 mmol) was added to a solution of complex 4b·CH₂Cl₂

(175 mg, 7.23ꢂ10^ꢀ2mmol) in CH₂Cl₂(10 mL), and the reaction mix-

ture was stirred overnight. The solution was filtered and evaporat-

ed to dryness. The residue was crystallized from a CH₂Cl₂/diethyl

ether mixed solvent to afford pale yellow crystals of 4 f·0.5CH₂Cl₂

(132 mg, yield: 69%). Elemental analysis calcd (%) for

C_82.5H₇₃O₁₂F₁₂P₈S₄ClAu₄(2683.81): C 36.92, H 2.74; found: C 36.87, H

2.58; IR (KBr pellet): n˜ =1439 (s, PꢀC), 1253 (br, CꢀF), 1160 (br, S=

O), 1103 (m), 1028 (s), 792 (br), 741 (m), 689 (m), 518 cm^ꢀ1(m); UV/

Vis (CH₂Cl₂): l_max(e)=366 nm (1.17ꢂ10⁵Lcm^ꢀ1mol^ꢀ1); (CH₃CN):

l_max(e)=373 (3.89ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, CD₂Cl₂,

RT): d=6.97–7.79 (m, 60H; Ph), 4.85 (dt, J=14, 4 Hz, 2H; CH₂), 4.69

(d, J=14 Hz, 4H), 4.26 (d, J=11 Hz, 4H), 4.03 ppm (dt, J=14, 3 Hz,

2H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=35.1 (m, 4P; P_out),

31.3 ppm (m, 4P; P_in); ESI-MS (CH₂Cl₂): m/z: 2491.228

2304.221),

1108.416

[Au₄(dpmppm)₂+2BF₄ꢀ4H]²⁺

(calcd:

1108.608), 1064.435 [Au₄(dpmppm)₂+BF₄ꢀ4H]²⁺(calcd: 1064.603),

1020.641 [Au₄(dpmppm)₂ꢀ5H]²⁺(calcd: 1020.598).

[Au₄(dpmppm)₂+3TfO]⁺

(calcd:

2491.076),

2377.093),

2377.217

1021.129

anti-[Au₄(meso-dpmppm)₂][TfO]₄·0.5Et₂O (5 f·0.5Et₂O): AgOTf

(80 mg, 0.31 mmol), meso-dpmppm (32 mg, 5.1ꢂ10^ꢀ2mmol), and

2,6-xylyl isocyanide (31 mg, 0.24 mmol) were added to a suspension

of 2 (80 mg, 5.2ꢂ10^ꢀ2mmol) in toluene (8 mL), and the reaction

mixture was stirred overnight in the dark. The solution was filtered

and evaporated to dryness. The residue was crystallized from

a CH₂Cl₂/diethyl ether mixed solvent at 48C to yield pale greenish

yellow, needle crystals of 5 f·0.5Et₂O (16 mg, yield: 11%). Elemental

analysis calcd (%) for C₈₄H₇₇O_12.5P₈S₄Au₄F₁₂(2678.40): C 37.67, H

2.90. found: C 37.83, H 2.78; IR (KBr pellet): n˜ =1486 (w), 1438 (s,

PꢀC), 1259 (br, OTf), 1161 (br, OTf), 1105 (m), 1029 (m), 804 (m),

741 (m), 688 (m), 637 (s), 522 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=

389 nm (7.18ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); UV/Vis (CH₃CN): l_max(e)=378 nm

(4.47ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, CD₂Cl₂, RT): d=7.65–

6.82 (m, 60H; Ph), 4.89–4.86 (br, 4H; CH₂), 4.31–4.28 (br, 4H; CH₂),

0.9 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=

35.8 ppm (m, 8P; P_out,in); ESI-MS (CH₂Cl₂): m/z: 2489.526

[Au₄(dpmppm)₂+Cl+2TfO]⁺

[Au₄(dpmppm)₂ꢀ2H]²⁺(calcd: 1021.102).

syn-[Au₄I₂(meso-dpmppm)₂][PF₆]₂·3.5CH₂Cl₂(4g·3.5CH₂Cl₂): KI

(7.9 mg, 4.7ꢂ10^ꢀ2mmol) was added to a solution of complex

4b·CH₂Cl₂(50.2 mg, 1.93ꢂ10^ꢀ2mmol) in a CH₂Cl₂/methanol mixed

solvent. The color of solution gradually changed from yellow to

orange. After stirring for 10 h, the solution was evaporated to dry-

ness. The residue was crystallized from an acetone/diethyl ether

mixed solvent to afford pale orange crystals of 4g·3.5CH₂Cl₂

(9.1 mg, yield: 18%). Elemental analysis calcd (%) for

C₁₅₉H₁₅₀P₂₀Au₈Cl₆F₂₄I₄(5433.77): C 35.15, H 2.78; found: C 34.96, H

2.68; IR (KBr pellet): n˜ =1437 (s, PꢀC), 1101 (m), 839 (s, PꢀF), 795

(m), 737 (s), 687 (s), 557 (s), 511 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=

450 (1.25ꢂ10⁴), 362 (5.69ꢂ10⁴), 320 nm (6.98ꢂ10⁴Lcm^ꢀ1mol^ꢀ1);

¹H NMR (300 MHz, CD₂Cl₂, RT): d=7.92–6.98 (m, 60H; Ph), 4.93–

4.23 (m, 3H; CH₂), 4.67 (br, 1H; CH₂), 4.50 (br, 3H; CH₂), 4.26 ppm

(br, 1H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=29.0 (m, 4P;

[Au₄(dpmppm)₂+3OTfꢀ2H]⁺

[Au₄(dpmppm)₂+2OTfꢀ4H]²⁺

[Au₄(dpmppm)₂+OTfꢀ4H]²⁺

(calcd:

2489.060),

1170.054),

1095.578),

1170.326

1095.395

1020.641

P

_out), 22.0 (m, 4P; P_in), ꢀ144.5 ppm (sept, 2P; PF₆, ¹J_PF=708 Hz);

ESI-MS (CH₂Cl₂): m/z: 2444.078 [Au₄I₂(dpmppm)₂+2PF₆]⁺(calcd:

[Au₄(dpmppm)₂ꢀ5H]²⁺(calcd: 1020.598).

syn-[Au₄(rac-dpmppm)₂Cl₂]Cl₂·1.5CH₂Cl₂

2443.946), 1149.059 [Au₄I₂(dpmppm)₂]²⁺(calcd: 1149.014).

(6a·1.5CH₂Cl₂):

anti-[Au₄(meso-dpmppm)₂][PF₆]₄·3CH₂Cl₂(5d·3CH₂Cl₂): AgPF₆

(70 mg, 0.27 mmol), meso-dpmppm (28 mg, 4.4ꢂ10^ꢀ2mmol), and

2,6-xylyl isocyanide (22 mg, 0.17 mmol) were added to a suspension

of 2 (66 mg, 4.2ꢂ10^ꢀ2mmol) in toluene (8 mL), and the reaction

mixture was stirred overnight in the dark. The solution was filtered

and evaporated to dryness. The residue was crystallized from

a CH₂Cl₂/diethyl ether mixed solvent at 48C to yield pale greenish

yellow crystals of 5d·3CH₂Cl₂(35 mg, yield: 29%). Elemental analy-

sis calcd (%) for C₈₁H₇₈P₁₂Au₄F₂₄Cl₆(2879.72): C 33.78, H 2.73;

found: C 33.79, H 2.83; IR (KBr pellet): n˜ =1485 (w), 1439 (s, PꢀC),

1297 (br), 1133 (w), 1106 (m), 841 (s, PꢀF), 740 (m), 688 (m),

558 cm^ꢀ1(w); UV/Vis (CH₂Cl₂): l_max(e)=387 nm (1.29ꢂ

[AuCl(PPh₃)] (84 mg, 0.17 mmol) was added to a solution of rac-

dpmppm (50 mg, 0.080 mmol) in CH₂Cl₂(10 mL) and the reaction

mixture was stirred for 12 h at room temperature, resulting in

a pale yellow suspension. The solution was evaporated to dryness.

After washing with diethyl ether, the residue was crystallized from

a concentrated CH₂Cl₂solution at 48C to afford pale yellow crystals

of 6a·1.5CH₂Cl₂(60 mg, yield: 62%). Elemental analysis calcd (%)

for C_79.5H₇₅P₈Au₄Cl₇(2314.27): C 41.26, H 3.27; found: C 41.22, H

2.89; IR (KBr pellet): n˜ =1436 (s, PꢀC), 1103 (s), 798 (br), 742 (m),

692 cm^ꢀ1

;

UV/Vis

(CH₂Cl₂):

l_max

(e)=375 nm

(3.40ꢂ

10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, [D₆]DMSO, RT): d=7.24–8.06

(m, 60H; Ph), 4.65 (d, J=14 Hz, 4H; CH₂), 4.20 (br s, 4H; CH₂),

3.47 ppm (m, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, [D₆]DMSO, RT): d=

32.5 (m, 4P; P_out), 28.1 ppm (m, 4P; P_in); ESI-MS (CH₂Cl₂): m/z:

2151.415 [Au₄(dpmppm)₂+3Cl]⁺(calcd: 2151.126), 1021.185

[Au₄(dpmppm)₂ꢀ2H]²⁺(calcd: 1021.102).

syn-[Au₄(rac-dpmppm)₂Cl₂][PF₆]₂·4CH₂Cl₂(6b·4CH₂Cl₂): [AuCl(tht)]

(34 mg, 0.10 mmol) and NH₄PF₆(46 mg, 0.28 mmol) were added to

a solution of rac-dpmppm (35 mg, 0.055 mmol) in CH₂Cl₂(5 mL)

and the reaction mixture was stirred for 12 h at room temperature.

The solution was evaporated to dryness. After washing with diethyl

10⁵Lcm^ꢀ1mol^ꢀ1),

(CH₃CN):

l_max

(e)=383 nm

(9.55ꢂ

10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, CD₂Cl₂, RT): d=7.62–6.83 (m,

60H; Ph), 4.68 (d, J=15 Hz, 4H; CH₂), 4.59 (d, J=16 Hz, 2H; CH₂),

4.35 (br, 2H; CH₂), 4.09 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz,

CD₂Cl₂, RT): d=35.6 (m, 4P; P_out), 35.2 (m, 4P; P_in), ꢀ143.9 ppm

(sept, 4P; PF₆, ¹J_PF=712 Hz); ESI-MS (CH₂Cl₂): m/z: 2477.627

1

[Au₄(dpmppm)₂+3PF₆ꢀH]⁺

[Au₄(dpmppm)₂+2PF₆ꢀ3H]²⁺

[Au₄(dpmppm)₂+PF₆ꢀ4H]²⁺

(calcd:

2478.104),

1166.570),

1093.539),

1166.345

1093.390

1020.641

[Au₄(dpmppm)₂ꢀ5H]²⁺(calcd: 1020.598).

Chem. Eur. J. 2014, 20, 1577 – 1596

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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper

ether, the residue was crystallized from a concentrated CH₂Cl₂solu-

tion at 48C to afford pale yellow crystals of 6b·4CH₂Cl₂(28 mg,

yield: 47%). Elemental analysis calcd (%) for C₈₂H₈₀P₁₀Au₄Cl₁₀F₁₂

(2745.63): C 35.85, H 2.94; found: C 35.97, H 2.60; IR (KBr pellet):

n˜ =1485 (w), 1438 (s, PꢀC), 1104 (s), 841 (s, PꢀF), 797 (m), 741 (m),

689 (m), 557 (s), 521 cm^ꢀ1(w); UV/Vis (CH₂Cl₂): l_max(e)=367 nm

(1.50ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, CD₂Cl₂, RT): d=7.23–

7.92 (m, 60H; Ph), 3.15 (br, 4H; CH₂), 3.90 (br, 4H; CH₂), 3.0–

BF₄), 797 (m), 743 (m), 689 cm^ꢀ1(m); UV/Vis (CH₂Cl₂): l_max(e)=

1

359 nm (4.17ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, [D₆]DMSO, RT):

d=7.30–7.93 (m, 60H; Ph), 4.90 (br, 4H; CH₂), 4.27 (brs, 4H; CH₂),

3.21 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, [D₆]DMSO, RT): d=

34.8 (m, 4P; P_out), 32.8 ppm (m, 4P; P_inn); ESI-MS (CH₃CN): m/z:

2305.224 [Au₄(dpmppm)₂+3BF₄]⁺(calcd: 2305.232), 1021.097

[Au₄(dpmppm)₂ꢀ2H]²⁺(calcd: 1021.102).

syn-[Au₄(rac-dpmppm)₂][TfO]₄·0.5CH₂Cl₂

(6 f·0.5CH₂Cl₂):

3.7 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT): d=31.90

[AuCl(tht)] (35 mg, 0.108 mmol) and NH₄OTf (49 mg, 0.29 mmol)

were added to a solution of rac-dpmppm (34 mg, 0.055 mmol) in

CH₂Cl₂(10 mL) and the reaction mixture was stirred for 12 h at

room temperature. The solution was evaporated to dryness. After

washing with diethyl ether, the residue was crystallized from a con-

centrated CH₂Cl₂solution at 48C to afford pale yellow needle crys-

tals of 6 f·0.5CH₂Cl₂(12 mg, yield: 17%). Elemental analysis calcd

(%) for C_82.5H₇₃O₁₂F₁₂S₄P₈Au₄Cl (2683.81): C 36.92, H 2.74; found: C

36.92, H 2.93; IR (KBr pellet): n˜ =1438 (s, PꢀC), 1255 (br, OTf), 1160

(br, OTf), 1104 (m), 1029 (s), 800 (m), 742 (m), 689 (m), 636 cm^ꢀ1(s);

UV/Vis (CH₂Cl₂): l_max(e)=360 nm (8.91ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); UV/Vis

(CH₃CN): l_max(e)=356 nm (5.45ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR

(300 MHz, CD₂Cl₂, RT): d=7.19–8.00 (m, 60H; Ph), 4.665 (br, 4H;

CH₂), 4.34–4.38 (m, 4H; CH₂), 3.64–3.67 ppm (m, 4H; CH₂); ³¹P{¹H}

NMR (121 MHz, CD₂Cl₂, RT): d=35.5 (m, 4P; P_out), 31.1 ppm (m, 4P;

P_in); ESI-MS (CH₂Cl₂): m/z: 2489.438 [Au₄(dpmppm)₂+3OTfꢀ2H]⁺

(calcd: 2489.060)), 1170.305 [Au₄(dpmppm)₂+2OTfꢀ4H]²⁺(calcd:

1170.054), 1095.375 [Au₄(dpmppm)₂+OTfꢀ4H]²⁺(calcd: 1095.578),

1020.443 [Au₄(dpmppm)₂ꢀ5H]²⁺(calcd: 1020.598).

1

(m, 4P; P_out), 27.2 (m, 4P; P_in), ꢀ144.3 ppm (sept, 3P; PF₆, J_PF

=

713 Hz); ESI-MS (CH₃OH): m/z: 1020.424 [Au₄(dpmppm)₂ꢀ5H]²⁺

(calcd: 1020.598).

syn-[Au₄(rac-dpmppm)₂Cl₂][BF₄]₂·CH₂Cl₂(6c·CH₂Cl₂): [AuCl(tht)]

(31 mg, 0.097 mmol) and NH₄BF₄(29 mg, 0.28 mmol) were added

to a solution of rac-dpmppm (35 mg, 0.055 mmol) in CH₂Cl₂(7 mL)

and the reaction mixture was stirred for 12 h at room temperature.

The solution was evaporated to dryness. After washing with diethyl

ether, the residue was crystallized from a concentrated CH₂Cl₂solu-

tion at 48C to afford pale yellow crystals of 6c·CH₂Cl₂(35 mg,

yield: 63%). Elemental analysis calcd (%) for C₇₉H₇₄P₈Au₄Cl₄B₂F₈

(2374.51): C 39.96, H 3.14; found: C 40.14, H 2.95; IR (KBr pellet):

n˜ =1483 (w), 1437 (s, PꢀC), 1104 (m), 1062 (br, BF₄), 798 (m), 744

(m), 690 (m), 523 (w), 513 cm^ꢀ1(w); UV/Vis (CH₂Cl₂): l_max(e)=

369 nm (2.82ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); UV/Vis (CH₃CN): l_max(e)=370 nm

(3.71ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); ¹H NMR (300 MHz, CD₂Cl₂, RT): d=7.21–

8.01 (m, 60H; Ph), 4.33–4.45 (m, 4H; CH₂), 3.93–3.97 (m, 4H; CH₂),

3.41–3.52 ppm (m, 4H; CH₂); ³¹P{¹H} NMR (121 MHz, CD₂Cl₂, RT):

d=31.6 (m, 4P; P_out), 26.3 ppm (m, 4P; P_in); ESI-MS (CH₃OH): m/z:

2179.748 [Au₄(dpmppm)₂+2Cl+BF₄ꢀH]⁺(calcd: 2200.153),

1020.424 [Au₄(dpmppm)₂ꢀ5H]²⁺(calcd: 1020.598).

X-ray crystallographic analyses of 1, 2, 4e, 4f, 5d–5f, 6a–6c,

6e, and 6f

syn-[Au₄(rac-dpmppm)₂][PF₆]₄(6d): NH₄PF₆(136 mg, 0.83 mmol)

was added to a solution of 6 f (28 mg, 0.010 mmol) in aceto-

ne(15 mL), and the mixture was stirred at room temperature for

12 h. The solvent was then removed under reduced pressure and

the residue was extracted with CH₂Cl₂(10 mL) and H₂O (10 mL).

The organic layer was separated and concentrated to dryness,

which was dissolved again in acetone (7 mL) and dried over

Na₂SO₄. The solution was filtered and concentrated, and was al-

lowed to stand at 48C after addition of diethyl ether, to afford pale

yellow crystals of 6d (9.3 mg, yield: 35%). Elemental analysis calcd

(%) for C₇₈H₇₂P₁₂Au₄F₂₄(2624.92): C 35.69, H 2.76; found: C 35.79, H

2.44; IR (KBr pellet): n˜ =1485 (w), 1439 (s, PꢀC), 1104 (s), 842 (s, Pꢀ

F), 799 (m), 741 (m), 688 (m), 558 cm^ꢀ1(s); UV/Vis (CH₂Cl₂): l_max

Crystals of 1, 2, 4e,f, 5d–f, 6a–c, 6e, and 6 f were quickly coated

with Paratone N oil and mounted on top of a loop fiber at room

temperature. The X-ray reflection data were measured with

a Rigaku VariMax Mo/Saturn CCD diffractometer equipped with

graphite-monochromated confocal Mo_Karadiation using a rotating-

anode X-ray generator RA-Micro7 (50 kV, 24 mA). Crystal and exper-

imental data are summarized in Tables S1–S3 in the Supporting In-

formation. All data were collected at ꢀ1208C and a total of 2160

oscillation images, covering a whole sphere of 6<2q<558, were

corrected by the w-scan method (ꢀ62<w<1188) with Dw of

0.258. The crystal-to-detector (70ꢂ70 mm) distance was set at

60 mm. The data were processed using the Crystal Clear 1.3.5 pro-

gram (Rigaku/MSC)^[26]and corrected for Lorentz-polarization and

absorption effects.^[27]The structures of complexes were solved by

direct methods with SHELXS-97^[28]and were refined on F²with full-

matrix least-squares techniques with SHELXL-97^[28]using the Crystal

Structure 3.7 package.^[29]All non-hydrogen atoms were refined

with anisotropic thermal parameters, and the CꢀH hydrogen

atoms were calculated at ideal positions and refined with riding

models. In both the structures of 1 and 4e, a solvent molecule of

crystallization is disordered (DMF for 1 and CH₂Cl₂for 4e). All cal-

culations were carried out on a Windows PC with Crystal Structure

3.7 package.^[29]The crystal data for 4b, 4d, and 4g were already

reported.^[11a]

1

(e)=358 nm (3.39ꢂ10⁴Lcm^ꢀ1mol^ꢀ1); H NMR (300 MHz, [D₆]DMSO,

RT): d=7.30–7.91 (m, 60H; Ph), 4.88–4.92 (br, 4H; CH₂), 4.25 (br s,

4H; CH₂), 3.23–3.26 ppm (br, 4H; CH₂); ³¹P{¹H} NMR (121 MHz,

[D₆]DMSO, RT): d=34.8 (m, 4P; P_out), 32.9 (m, 4P; P_in), ꢀ143.0 ppm

(sept, 4P; PF₆, ¹J_PF=713 Hz); ESI-MS (CH₂Cl₂): m/z: 2479.262

[Au₄(dpmppm)₂+3PF₆]⁺

(calcd:

2479.112),

2369.117),

2369.133

1021.121

[Au₄(dpmppm)₂+Cl+2PF₆]⁺

[Au₄(dpmppm)₂]²⁺(calcd: 1021.102).

syn-[Au₄(rac-dpmppm)₂][BF₄]₄·CH₂Cl₂(6e·CH₂Cl₂): NH₄BF₄(97 mg,

0.92 mmol) was added to a solution of 6 f (24 mg, 0.0089 mmol) in

acetone (10 mL), and the mixture was stirred at room temperature

for 12 h. The solvent was then removed under reduced pressure

and the residue was extracted with CH₂Cl₂(8 mL) and H₂O (5 mL).

The organic layer was separated and concentrated to dryness,

which was dissolved again in acetone (7 mL) and dried over

Na₂SO₄. The solution was filtered and concentrated, and was al-

lowed to stand at 48C after addition of diethyl ether, to afford pale

yellow crystals of 6e·CH₂Cl₂(7.0 mg, yield: 32%). Elemental analysis

calcd (%) for C₇₉H₇₄P₈Au₄Cl₂B₄F₁₆(2477.21): C 38.30, H 3.01; found:

C 38.18, H 3.12; IR (KBr pellet): n˜ =1485 (w), 1438 (s, PꢀC), 1054 (br,

CCDC-959320 (1), CCDC-959321 (2), CCDC-959322 (4e), CCDC-

959323 (4 f), CCDC-959324 (5d), CCDC-959325 (5e), CCDC-959326

(5 f), CCDC-959327 (6a), CCDC-959328 (6b), CCDC-959329 (6c),

CCDC-959330 (6e), and CCDC-959331 (6 f) contain the supplemen-

tary crystallographic data for this paper. These data can be ob-

tained free of charge from The Cambridge Crystallographic Data

Centre via www.ccdc.cam.ac.uk/data_request/cif.

Chem. Eur. J. 2014, 20, 1577 – 1596

www.chemeurj.org

1594

ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper

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Theoretical calculations

Gas-phase DFT calculations were performed on model compounds

(M4–M6) using the MPWPW91^[15]functions with Stuttgart–

Dresden ECP basis set, SDD (the 19-valence electron Wood–

Boring quasirelativistic pseudopotentials were used for

Au).^[16]The DFT optimization were carried out on the models,

syn-[Au₄(meso-H₂PCH₂P(H)CH₂P(H)CH₂PH₂)₂]⁴⁺(M4), anti-[Au₄(meso-

H₂PCH₂P(H)CH₂P(H)CH₂PH₂)₂]⁴⁺

(M5),

and

syn-[Au₄(rac-

H₂PCH₂P(H)CH₂P(H)CH₂PH₂)₂]⁴⁺(M6), the initial coordinates being

derived from the crystal structures of 4d, 5e, and 6e by replacing

phenyl groups by hydrogen atoms. TD-DFT calculations^[30]were

also performed with the optimized structures. The lowest triplet

(T₁) excited states for M4–M6 were analyzed by DFT optimizations

with the unrestricted MPWPW91/SDD methods.

Geometry optimizations and frequency analyses for the complexes

(4d, 5e and 6e) of the singlet (S₀) and the triplet (T₁) states were

carried out by the DFT method with B3LYP^[19]functional set and

Grimme’s D2 empirical dispersion (B3LYP-D)^[20]parameter. The po-

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they did not have any negative frequencies. After the geometry

optimizations, the single-point calculations and the time-depen-

dent DFT (TD-DFT) calculations were carried out with the larger

basis set that consisted of LANL2TZ(f) and 6-31+G* for Au and

other atoms, respectively. To examine absorption spectra of the

complexes, ten excited states (S₁–S₁₀) were calculated by TD-DFT

calculations with B3LYP functional set at the optimized S₀struc-

tures. The emission energy was estimated by both DSCF and TD-

DFT calculations with B3LYP-D functional set at the optimized trip-

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B3LYP functional set. All calculations were carried out on a UNIX

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This work was supported by the Ministry of Education, Culture,

Sports, Science and Technology, Japan through Grant-in-Aid for

Scientific Research and that on Priority Area 2107 (22108521,

24108727, 22108515, 24108721). T.T. is grateful to Nara

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Received: September 24, 2013

Published online on January 8, 2014

Chem. Eur. J. 2014, 20, 1577 – 1596

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Strongly luminous tetranuclear gold(I) complexes supported by tetraphosphine ligands, meso- or rac-Bis[(diphenylphosphinomethyl) phenylphosphino]methane

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