Photoactive building blocks for coordination complexes: Gilding 2,2′:6′,2″-terpyridine

Article abstract of DOI:10.1016/j.poly.2011.08.001

The alkyne unit of 4′-ethynyl-2,2′:6′,2″- terpyridine has been functionalized with Ph₃PAu, (2-tolyl) ₃PAu or Au(dppe)Au units to produce compounds 1-3, respectively. These derivatives have been characterized by electrospray mass spec

Full text of DOI:10.1016/j.poly.2011.08.001

Polyhedron 30 (2011) 2704–2710
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Photoactive building blocks for coordination complexes: Gilding
2,20:60,200-terpyridine
⇑
⇑
Edwin C. Constable , Catherine E. Housecroft , Marzena K. Kocik, Jennifer A. Zampese
Department of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel, Switzerland
a r t i c l e i n f o
a b s t r a c t
The alkyne unit of 40-ethynyl-2,20:60,200-terpyridine has been functionalized with Ph3PAu, (2-tolyl)3PAu or
Au(dppe)Au units to produce compounds 1–3, respectively. These derivatives have been characterized by
electrospray mass spectrometry, solution 1H and 13C NMR, UV–Vis and emission spectroscopies, and sin-
gle crystal X-ray diffraction. In the solid state, molecules of 1 or 2 pack with separated domains of tpy and
Article history:
Received 14 June 2011
Accepted 1 August 2011
Available online 5 August 2011
R3PAu units; the tpy units in 2 (but not 1) exhibit face-to-face
2(3).CHCl3, and the folded conformation of the dppe backbone results in a short (2.9470(8) Å) aurophilic
interaction. Folded molecule 3 captures CHCl3, preventing intramolecular face-to-face -interactions
between the tpy units. In CH2Cl2 solution, 1–3 are emissive when excited between 230 and 300 nm,
but over minutes when kex = 230 nm, the emission bands decay as the compounds photodegrade.
Ó 2011 Elsevier Ltd. All rights reserved.
p-stacking. Compound 3 crystallizes as
Keywords:
Gold(I)
2,2,0:60,200-Terpyridine
Phosphane
Alkyne
p
Photophysics
1. Introduction
rectly attached to the 40-position of the tpy domain. This is in con-
trast to previously reported systems in which the tpy and C„C
Gold(I) alkynyl complexes [1,2] containing gold atoms in linear
coordination environments are popular building blocks for poly-
meric and macrocyclic organometallic assemblies [3–12]. The
luminescent properties of gold(I) species [13,14] and the ease of
synthesis of gold(I) alkynyls make them attractive candidates for
derivatization of other metal-binding domains such as pyridine
[15–19], 2,20-bipyridine (bpy) [16,20,21] and 2,20:60,200-terpyridine
(tpy) [21,22]. The combination of a luminescent gold(I) unit and a
chelating ligand provides an approach to the design of metal ion
sensors.
In gold(I) derivatives, aurophilic interactions (i.e. short Auꢀ ꢀ ꢀAu
contact of around 3.00–3.20 Å) [23] are considered important in
influencing their emissive behaviour [24–27]. Recently, we re-
ported the solid-state structures of four bis(gold(I) phosphane)-
decorated 4,40-diethynyl-2,20-bipyridines (Scheme 1) [20]. Chang-
ing the phosphane from PEt3 to PiPr3 alters the packing, producing
different polymeric chain motifs. In both, Auꢀ ꢀ ꢀAu contacts of less
than 3.4 Å are observed. For the more sterically demanding PPh3
and P(4-tolyl)3 substituents, no short Auꢀ ꢀ ꢀAu contacts are present
in the solid state. In CH2Cl2 solution, each compound (Scheme 1) is
a dual emitter at room temperature. However, with kex ꢁ 238 nm,
the emission spectra decay quite rapidly at the expense of a new
set of emission maxima, and we have proposed that this arises
from cleavage of the Au–Calkyne bond. We now turn our attention
to tpy-based compounds in which the alkynyl substituent is di-
units are separated by an arene spacer [21,22].
2. Experimental
2.1. General procedures
1H and 13C NMR spectra were recorded on a Bruker DRX-500
NMR spectrometer with chemical shifts referenced to residual sol-
vent peaks (CHCl3 = d 7.24 ppm, TMS = d 0 ppm). 31P NMR spectra
were recorded using a Bruker DRX-400 NMR spectrometer and
were referenced with respect to 85% H3PO4 = d 0 ppm. Absorption
spectra were recorded using a Varian-Cary 5000 spectrophotome-
ter and emission spectra using a Shimadzu RF-5301 PC spectroflu-
orometer; excitation/emission slit widths were set at 3/3, 5/3, 3/3,
and 5/5 for 40-ethynyl-2,20:60,200-terpyridine, 1, 2 and 3, respec-
tively. Electrospray ionization (ESI) mass spectra were measured
with a Bruker esquire 3000plus mass spectrometer.
40-Ethynyl-2,20:60,200-terpyridine was prepared according to the
literature procedure starting from 40-[(trifluoromethylsulfo-
nyl)oxy]-2,20:60,200-terpyridine [28]. R3PAuCl with R = Ph or 2-tolyl
was prepared by a reported route [29] with a reaction temperature
of ꢂ5 °C. Abbreviation: tht, tetrahydrothiophene.
2.2. {Au(40-C„Ctpy)}n
⇑
The synthesis of {Au(40-C„Ctpy)}n was based on that described
for {Au(4-C„Cpy)}n [17]. 40-Ethynyl-2,20:60,200-terpyridine (50 mg,
Corresponding author. Fax: +41 61 267 1018.
E-mail address: catherine.housecroft@unibas.ch (C.E. Housecroft).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.08.001

E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
2705
peak, calc. 758.2). Anal. Calc. for C38H31AuN3P.H2O: C, 58.84; H,
4.29; N, 5.42. Found: C, 59.14; H, 4.11; N, 5.38%.
2.5. Compound 3
Bis(diphenylphosphinoethane) (dppe, 22 mg, 55
l
mol) and
{Au(40-C„Ctpy)}n (50 mg, 110
lmol) were stirred in CH2Cl2
Scheme 1. Previously reported bis(gold(I) phosphane)-4,40-diethynyl-2,20-bipyri-
dine compounds [20].
(10 cm3) for 30–60 min. After this time, the solvent was evapo-
rated in vacuo and the crude product was purified in the dark by
preparative plate chromatography (Al2O3, CH2Cl2). Compound 3
was isolated as white solid (31.2 mg, 23.9 l
mol, 43.4%). 1H NMR
190
950
l
l
mol), [(tht)AuCl] (63.5 mg, 190 lmol) and NaOAc (77.9 mg,
mol) were added to a mixture of THF (5 cm3) and MeOH
(500 MHz, CDCl3) d/ppm 8.68 (d, J = 4.6 Hz, 4H, HA6), 8.56 (d,
J = 8.0 Hz, 4H, HA3), 8.55 (s, 4H, HB3), 7.82 (td, J = 7.8, 1.5 Hz, 4H,
HA4), 7.72 (m, 8H, HC2), 7.52 (overlapping m, 12H, HC3/C4), 7.38
(m, 4H, HA5), 2.69 (s, 4H, Ha). 13C NMR (126 MHz, CDCl3) d/ppm
156.2 (CA2), 155.3 (CB2), 149.2 (CA6), 136.7 (CA4), 135.0 (CB5),
133.5 (CC2), 132.3 (CC4), 129.7 (t, JPC = 6 Hz, CC3), 124.0 (CB3),
123.7 (CA5), 121.2 (CA3), 102.0 (poorly resolved, C„CAu), 24.0
(JPC = 17 Hz, Ca), signals for CC1 and C„CAu not observed. 31P
NMR (162 MHz, CDCl3) d/ppm 40.6. UV–Vis kmax/nm (CH2Cl2) 230
(5 cm3) under argon and with light excluded. The reaction mixture
was stirred for 6–12 h after which time a pale yellow precipitate
was obtained. This was collected by filtration and washed with
MeOH. {Au(40-C„Ctpy)}n was isolated as yellow solid (72 mg,
159 lmol, ca. 82%) and was used without further purification.
2.3. Compound 1
Ph3PAuCl (38 mg, 78
l
mol), 40-ethynyl-2,20:60,200-terpyridine
mol) were dissolved in CH2Cl2
(8 cm3) and MeOH (2 cm3). NaOAc (13 mg, 156
mol) was then
(e
/dm3 molꢂ1 cmꢂ1 122 000), 239 (11 6000), 254 (100 000), 277
(20 mg, 78
lmol), CuI (0.7 mg, 4
l
(136 000), 289 (156 000), 319 (26 000), 332 (19 000). Emission
(CH2Cl2, kexc = 241 nm) kem/nm 341, 355. ESI MS (CH2Cl2) m/z
1305.8 [M+H]+ (calc. 1305.3), 1048.6 [Au(dppe)AuCCtpy]+ (calc.
1048.2), 993.7 [(dppe)2Au]+ (calc. 993.2). Anal. Calc. for
l
added, and the reaction mixture stirred at room temperature in
the dark for 12–16 h. It was then filtered and the solvent removed
from the filtrate in vacuo. The crude material was purified by pre-
parative plate chromatography in the dark (Al2O3, CH2Cl2). 1 was
C
60H44Au2N6P2ꢀ2H2O: C, 53.74; H, 3.61; N, 6.27. Found: C, 53.76;
H, 3.41; N, 6.00.
isolated as a white solid (39.3 mg, 55.3 l
mol, 70.7%). 1H NMR
(500 MHz, CDCl3) d/ppm 8.66 (d, J = 4.0 Hz, 2H, HA6), 8.54 (d,
J = 8.1 Hz, 2H, HA3), 8.52 (s, 2H, HB3), 7.80 (td, J = 7.8, 1.7 Hz, 2H,
HA4), 7.54 (m, 6H, HC2/C3), 7.49 (m, 3H, HC4), 7.45 (m, 6H, HC2/C3),
7.29 (m, 2H, HA5). 13C NMR (126 MHz, CDCl3) d/ppm 156.5 (CA2),
155.4 (CB2), 149.4 (CA6), 136.8 (CA4), 135.3 (CB4), 134.5 (d,
JPC = 14 Hz, CC2/C3), 131.8 (d, JPC = 2 Hz, CC4), 129.6 (d, JPC = 56 Hz,
CC1), 129.4 (d, JPC = 11 Hz, CC2/C3), 124.3 (CB3), 123.7 (CA5), 121.3
(CA3), 102.3 (poorly resolved, C„CAu), signal for C„CAu not ob-
served. 31P NMR (162 MHz, CDCl3) d/ppm 42.4. UV–Vis kmax/nm
2.6. Crystal structure determinations
Data were collected on a Stoe IPDS diffractometer and the data
reduction, solution and refinement used Stoe IPDS software [30]
and SHELXL97 [31]. ORTEP figures were drawn using Ortep-3 for
Windows [32], and the structures were analysed using Mercury
v. 2.4 [33,34].
2.7. Compound 1
(CH2Cl2) 229
(e
/dm3 molꢂ1 cmꢂ1 53 000), 244 (50 000), 277
(54 000), 289 (62 000), 319 (9000), 331 (6000). Emission (CH2Cl2,
kexc = 244 nm) kem/nm 339, 355. ESI MS (CH2Cl2/MeOH) m/z
1174.4 [M+AuPPh3]+ (calc. 1174.2), 716.3 [M+H]+ (base peak, calc.
716.2). Anal. Calc. for C35H25AuN3P: C, 58.75; H, 3.52; N, 5.87.
Found: C, 58.55; H, 3.72; N, 5.92%.
C
35H25AuN3P, M = 715.52, colourless plate, monoclinic, space
group P21/c, a = 19.658(4), b = 8.3726(17), c = 17.853(4) Å,
b = 105.39(3)°, U = 2833.0(10) Å3, Z = 4, Dcalc = 1.678 Mg mꢂ3
(Mo K
) = 5.279 mmꢂ1, T = 173 K. Total 44 788 reflections, 5835
unique, Rint = 0.0979. Refinement of 5641 reflections (361 parame-
ters) with I > 2 (I) converged at final R1 = 0.0426 (R1 all
,
l
a
r
2.4. Compound 2
data = 0.0435), wR2 = 0.1087 (wR2 all data = 0.1098), Goodness-
of-fit = 1.144.
The method was as for 1, starting with (2-tolyl)3PAuCl (42 mg,
78
Ac (13 mg, 156
isolated as a white solid (36.2 mg, 47.8
l
mol), 40-ethynyl-2,20:60,200-terpyridine (20 mg, 78
l
mol), NaO-
mol). Compound 2 was
mol, 61.6%). 1H NMR
2.8. Compound 2
lmol) and CuI (0.7 mg, 4 l
l
C38H31AuN3P, M = 757.60, colourless plate, triclinic, space group
(500 MHz, CDCl3) d/ppm 8.68 (dd, J = 4.6, 0.8 Hz, 2H, HA6), 8.53
(d, J = 7.9 Hz, 2H, HA3), 8.48 (s, 2H, HB3), 7.79 (td, J = 7.7, 1.8 Hz,
2H, HA4), 7.44 (t, J = 7.5 Hz, 3H, HC4), 7.36 (m, 3H, HC3), 7.26 (ddd,
J = 7.4, 4.8, 1.0 Hz, 2H, HA5), 7.17 (t, J = 7.6 Hz, 3H, HC5), 6.93 (dd,
JPH = 12.2 Hz, JHH = 7.7 Hz, 3H, HC6), 2.73 (s, 9H, HMe). 13C NMR
(126 MHz, CDCl3) d/ppm 156.3 (CA2), 155.1 (CB2), 151.1 (CA6),
149.1 (d, JPC = 13 Hz, CC2), 136.6 (CA4), 135.4 (CB4), 133.6 (d,
JPC = 8 Hz, CC6), 132.2 (d, JPC = 9 Hz, CC3), 131.6 (d, JPC = 2 Hz, CC4),
126.6 (d, JPC = 9 Hz, CC5), 126.2 (d, JPC = 55 Hz, CC1), 124.0 (CB3),
123.5 (CA5), 121.1 (CA3), 102.4 (d, JPC = 26.6 Hz, C„CAu), 23.7 (d,
J = 11 Hz, CMe), signal for C„CAu not observed. 31P NMR
P1, a = 9.2574(9), b = 17.6618(19), c = 19.504(2) Å,
b = 96.023(8)°,
= 91.372(8)°, U = 3024.9(5) Å3, Z = 4, Dcalc
1.664 Mg mꢂ3 ) = 4.949 mmꢂ1, T = 173 K. Total 67 142
(Mo K
reflections, 12 533 unique, Rint = 0.1018. Refinement of 11 198
reflections (782 parameters) with I > 2 (I) converged at final
a
= 107.172(8)°,
ꢀ
c
=
,
l
a
r
R1 = 0.0491 (R1 all data = 0.0537), wR2 = 0.1379 (wR2 all data =
0.1417), Goodness-of-fit = 1.182.
2.9. Compound 2(3)ꢀCHCl3
C121H89Au4Cl3N12P4, M = 2729.16, colourless needle, monoclin-
ic, space group Pc, a = 10.389(2), b = 17.482(4), c = 15.652(3) Å,
(162 MHz, CDCl3) d/ppm 24.3. UV–Vis kmax/nm (CH2Cl2), 251 (e/
dm3 molꢂ1 cmꢂ1 53 000), 280 (59 000), 288 (64 000), 318 (9000),
332 (6000). Emission (CH2Cl2, kexc = 252 nm) kem/nm 341, 354.
ESI MS (CH2Cl2/MeOH) m/z 1258.5 [M+AuP(tolyl)3]+ (calc.
1258.3), 805.2 [Au{P(tolyl)3}2]+ (calc. 805.2), 758.4 [M+H]+ (base
b = 98.53(3)°, U = 2811.2(10) Å3, Z = 1, Dcalc = 1.612 Mg mꢂ3
, l
(Mo K
unique, Rint = 0.1933. Refinement of 9643 reflections (669 parame-
ters) with I > 2 (I) converged at final R1 = 0.0625 (R1 all
a
) = 5.384 mmꢂ1, T = 173 K. Total 49 946 reflections, 10 592
r

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E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
data = 0.0704), wR2 = 0.1525 (wR2 all data = 0.1591), Goodness-
of-fit = 1.075.
and [M+H]+, respectively. All isotope patterns were in accord with
those simulated.
For each of compounds 1 and 2, the 31P NMR spectrum showed
one singlet (d 42.4 and 24.3 ppm, respectively, in CDCl3) shifted to
higher frequency with respect to the corresponding R3PAuCl (d
30.2 and 5.2, respectively, in CDCl3). The signals in the solution
1H and 13C NMR spectra of 1 and 2 were assigned using COSY,
DEPT, HMQC and HMBC techniques, and were consistent with
the presence of a single tpy environment in each compound. In
the 13C NMR spectrum of 2, a doublet at d 102.4 ppm (JPC = 26.6 Hz)
[35] was assigned to C„CAu, and this was confirmed by the obser-
vation of a cross-peak between this resonance and that of proton
HB3 (see Scheme 2 for labelling). For 1, the HMBC spectrum exhib-
ited a cross-peak between the signal for HB3 and a poorly resolved
signal at d 102.3 ppm, and the latter was assigned to alkyne carbon
C„CAu. The resonance for the second alkyne 13C nucleus was not
observed in either 1 or 2, a feature that we have also reported for
gold(I) phosphane 4,40-diethynyl-2,20-bipyridine derivatives [20].
The structures of 1 and 2 were confirmed by single crystal X-ray
diffraction. Suitable crystals were grown by slow diffusion of Et2O
into CH2Cl2/toluene solutions of the compounds. Compound 1
(Fig. 1) crystallizes in the P21/c space group, while 2 (Fig. 2) crystal-
3. Results and discussion
3.1. Synthesis and characterization of compounds 1 and 2
We have previously shown that coupling of 4,40-diethynyl-2,20-
bipyridine and R3PAuCl in the presence of diisopropylamine and
CuI yields gold(I) phosphane-derivatized bpy ligands [20]. When
this methodology was extended to the synthesis of gold(I) phos-
phane derivatives of 40-ethynyl-2,20:60,200-terpyridine, we found
that it was more convenient to replace the organic base by NaOAc.
Treatment of 40-ethynyl-2,20:60,200-terpyridine with R3PAuCl (R = Ph
or 2-tolyl) in a mixture of MeOH and CH2Cl2 in the presence of CuI
and an excess of NaOAc resulted in the formation, after workup, of
white solids 1 and 2. In the ESI mass spectrum of 1, peaks at m/z
1174.4 and 716.3 were assigned to [M+AuPPh3]+ and [M+H]+. For
2, the mass spectrum exhibited peaks at m/z 1258.5, 805.2 and
758.4, consistent with the ions [M+AuP(tolyl)3]+, [Au{P(tolyl)3}2]+
ꢀ
lizesinspacegroupP1withtwoindependentmoleculesintheasym-
metric unit. The structural features of 1 and 2 are similar. The tpy
unit adopts the anticipated trans,trans-configuration and is essen-
tially planar. The angles between the least squares planes of the pyr-
idine rings containingN1/N2 and N2/N3 are 12.5(2)° and 3.4(2)° in 1,
2.6(3)°and15.5(3)°inmoleculeAof2, and7.8(3)°and3.9(3)°inmol-
ecule B of 2. The C8–C16–C17–Au1–P1 linkage is close to linear in
each compound (see captions to Figs. 1 and 2).
Fig. 3 illustrates the packing of molecules of 1 in the crystal lat-
tice. The molecules are organised to give sheets of either tpy or
Ph3PAu domains. Alkyne atom C17 exhibits short contacts to two
CHphenyl units, one in each of two adjacent molecules
(C17ꢀ ꢀ ꢀH27aiC27i = 2.67 Å, C17ꢀ ꢀ ꢀH32aiiC32ii = 2.90 Å, symmetry
codes i = ꢂx, 1/2 + y, 1/2 ꢂ z; ii = x, 1 + y, z). There are no face-to-face
p-interactions between adjacent tpy units. In contrast, the tpy
units in neighbouring molecules of 2 are
p-stacked (Fig. 4); tpy
rings containing atoms N1a and N2a lie over those with N1ai and
N2ai (symmetry code i = 3 ꢂ x, 2 ꢂ y, 2 ꢂ z) with an optimal slipped
arrangement and a separation of 3.4 Å. Similarly, the rings contain-
ing N1b and N2b are stacked over those containing N1bii and N2bii
(symmetry code ii = 1 ꢂ x, 2 ꢂ y, 1 ꢂ z) at a separation of 3.5 Å. The
tpy domains extend into layers which lie in the ac plane, and
consecutive tpy-sheets are separated by sheets of interlocked
P(2-tolyl)3 units (Fig. 4).
Scheme 2. Structures of compounds 1–3 with numbering schemes for NMR
spectroscopic assignments. Phenyl and 2-tolyl rings are labelled C.
Fig. 1. Structure of compound 1 (ellipsoids plotted at 30% probability level; H atoms omitted). Selected bond parameters: Au1–C17 = 2.003(4), Au1–P1 = 2.2742(10), P1–
C24 = 1.816(4), P1–C30 = 1.807(4), P1–C18 = 1.815(4), C16–C17 = 1.195(6) Å; C17–Au1–P1 = 176.93(11)°, C16–C17–Au1 = 176.1(4)°, C17–C16–C8 = 172.8(4)°.

E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
2707
Fig. 2. One of the two independent molecules (molecule A) of 2 (ellipsoids plotted at 40% probability level; H atoms omitted). Selected bond parameters: Au1a–
C17a = 1.996(6), Au1a–P1a = 2.2859(14), P1a–C18a = 1.815(5), P1a–C25a = 1.825(5), P1a–C32a = 1.830(6), C16a–C17a = 1.187(8) Å; C17a–Au1a–P1a = 172.31(19)°, C16a–
C17a–Au1a = 175.7(6)°, C17a–C16a–C8a = 178.8(8)°. Bond parameters for the second independent molecule (molecule B) are similar.
Fig. 3. View down the crystallographic c axis showing the packing of molecules of 1 into domains of tpy units (two domains shown) and Ph3PAu units (three domains shown).
Fig. 4. Packing of molecules of 2 involves
p-stacked domains of tpy units (two domains shown) separated by domains of (2-tolyl)3PAu units (three domains shown).
3.2. Synthesis and characterization of 3
the preparation of rod-like isonitrile derivatives from treatment
of CNC6H4O(O)CC6H4OC10H21-p with {Au(4-C„Cpy)}n [17]. The
During attempts to prepare compound 3 in a similar manner to
1 and 2, we encountered difficulties with the purification of the
product, and therefore turned to the use of {Au(40-C„Ctpy)}n as
a precursor, following the strategy adopted by Ferrer et al. for
polymer {Au(40-C„Ctpy)}n was prepared by reaction of 40-ethy-
nyl-2,20:60,200-terpyridine with [(tht)AuCl] in the presence of NaO-
Ac, and the yellow solid obtained was used without purification.
Treatment of {Au(40-C„Ctpy)}n with dppe in CH2Cl2 resulted, after

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E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
[(dppe)2Au]+. The solution 31P NMR spectrum exhibited one singlet
at d 40.6 ppm, consistent with a symmetrical environment for the
dppe ligand. This was supported by the observation of one signal
for the methylene groups in each of the 1H and 13C NMR spectra,
and the spectra were also consistent with the presence of one
tpy environment; the resonances were assigned using COSY, DEPT,
HMQC and HMBC methods. As for 1 and 2, the signal for C„CAu
was not observed, while the second alkyne carbon gave rise to a
poorly resolved signal at d 102.0 ppm. This assignment was con-
firmed by a cross-peak in the HMBC spectrum to the resonance
for proton HB3
.
Single crystals of 2(3).CHCl3 were grown by slow diffusion of
Et2O into a CH2Cl2/CHCl3/toluene solution of 3, and X-ray diffrac-
tion structure determination confirmed the molecular structure
shown in Fig. 5. The two gold(I) centres are in close contact with
a separation of 2.9470(8) Å, consistent with an aurophilic interac-
tion [36,37]. In theory, the folded conformation of 3 could have
resulted in face-to-face p-interactions between the two tpy units,
but as Fig. 6 illustrates, this is prevented by the guest chloroform
molecule. Closest contacts are C32H32aꢀ ꢀ ꢀCl2 = 3.27 Å and
C60H60aꢀ ꢀ ꢀCl3 = 3.61 Å.
Fig. 5. Molecule of 3 in 2(3).CHCl3 (ellipsoids plotted at 30% probability level; H
atoms omitted). Selected bond parameters: Au1–Au2 = 2.9470(8), Au1–C27 =
2.015(16), Au1–P1 = 2.287(3), Au2–C44 = 2.019(19), Au2–P2 = 2.272(4), P1–C1 =
1.806(17), P1–C3 = 1.815(14), P1–C9 = 1.827(17), P2–C21 = 1.797(14), P2–
The packing of molecules of 3 in 2(3).CHCl3 comprises two
assembly motifs. The first consists of ribbons which run parallel
to the a-axis and are generated by face-to-face
p-interactions;
C15 = 1.811(16),
P2–C2 = 1.830(16),
C27–C28 = 1.18(2),
C44–C45 = 1.18(2),
two out of three pyridine rings are involved (separation of rings
containing N4 and N2i = 3.3 Å, and of rings with N5 and
N3i = 3.5 Å, symmetry code i = 1 + x, y, z), leaving the third pyridine
ring protruding from one side of the ribbon (Fig. 7a). The ribbons
are arranged in a herringbone fashion (Fig. 7b), the assembly being
supported by CHꢀ ꢀ ꢀCalkyne and CHꢀ ꢀ ꢀNi contacts, the latter involving
C28–C36 = 1.453(17), C45–C53 = 1.46(2) Å; C27–Au1–P1 = 173.8(4)°, C27–Au1–
Au2 = 96.0(4)°, P1–Au1–Au2 = 87.54(9)°, C44–Au2–P2 = 176.8(4)°, C44–Au2–Au1 =
93.5(5)°, P2–Au2–Au1 = 88.37(10)°, C28–C27–Au1 = 174.2(13)°, C27–C28–C36 =
171.0(17)°, C45–C44–Au2 = 176.4(15)°, C44–C45–C53 = 175.9(17)°.
the non-
p
-stacked pyridine ring: C58H58aꢀ ꢀ ꢀC45i = 2.86 Å,
C31H31aꢀ ꢀ ꢀN5ii = 2.74 Å, symmetry codes i = x, 2 ꢂ y, 1/2 + z,
1
ii = ꢂ1 + x, 2 ꢂ y, ꢂ /2 + z. This leads to short, repulsive Hꢀ ꢀ ꢀH con-
tacts (C59H59aꢀ ꢀ ꢀH20aiC20i = 2.32 Å).
3.3. Photophysical properties
The electronic absorption spectrum of a CH2Cl2 solution of 40-
ethynyl-2,20:60,200-terpyridine exhibits bands at 241 and 280 nm
and a low energy tail with broad, low intensity maxima at 317
and 329 nm (Fig. 8). The absorptions arise from alkyne and tpy
p⁄
p
and p⁄ n transitions. An increase in emax is observed on
Fig. 6. Space-filling diagram to show the sandwich effect of the two tpy domains
around the CHCl3 solvent molecule.
going from 40-ethynyl-2,20:60,200-terpyridine to each of compounds
1, 2 and 3, and the approximate doubling in the values of emax on
going from 1 or 2 to compound 3 is consistent with the doubling
of the number of tpy and alkyne units per molecule. The pattern
of absorptions in the region between 260 and 310 nm is similar
for each of compounds 1–3, with two maxmima at ca. 276 and
289 nm. Based on studies of related species [21,38–41] the transi-
work up, in the isolation of 3 in moderate yield. In the ESI mass
spectrum, the highest mass peak envelope at m/z 1305.8 was as-
signed to [M+H]+. Additional peaks were observed at m/z 1048.6
and 993.7 arising from the ions [Au(dppe)AuCCtpy]+ and
Fig. 7. (a) Assembly of a ribbon along the crystallographic a axis through p-stacking of tpy domains. (b) View down the a axis showing the herringbone arrangement of the
ribbons.

E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
2709
Fig. 8. Electronic absorption spectra of CH2Cl2 solutions of 40-ethynyl-2,20:60,200-
terpyridine (ꢀꢀꢀꢀꢀ), 1 (—), 2 (– ꢀꢀ –) and 3 (–).
Fig. 11. Emission spectrum of 3 recorded approximately each minute over an 8 min
period (kex = 239 nm; ⁄first harmonic).
and new bands grew in (Fig. 10). Compared to those for 1, the
new emission bands appeared at similar wavelengths for 2, sug-
gesting that the photodegradation products were related. The
changes in emission spectra of 3 as a function of time are depicted
in Fig. 11. The broad band that grows in between 410 and 560 nm
is consistent with one of the broad emissions observed upon deg-
radation of 1 and 2, but the strong emission observed at 280 nm as
1 degrades (Fig. 10) is almost completely quenched in 3 (Fig. 11).
When kex was at wavelengths higher than 230 nm, photodecay
was much slower. We have not been able to determine the identi-
ties of the photodegradation products, but note that comparable
decay and growth of bands in the emission spectra of gold(I) phos-
phane derivatives of 4,40-diethynyl-2,20-bipyridine are observed
over time [20]. In particular, as 1 decays, the emission centred
around 570 nm (Fig. 10) matches that observed for the photodecay
of 4,40-(R3PAuC„C)2-2,20-bipyridine (R = Ph or 4-tolyl) and we
suggested [20] that this arises from the formation of small gold
nanoclusters [42].
Fig. 9. Emission spectra for CH2Cl2 solutions of 40-ethynyl-2,20:60,200-terpyridine
(ꢀꢀꢀꢀꢀ), 1 (—), 2 (– ꢀꢀ –) and 3 (–) (kex ꢃ 289 nm). Concentrations: 40-ethynyl-2,20:60,200-
terpyridine, 1.2 ꢄ 10ꢂ5; 1, 8.4 ꢄ 10ꢂ6; 2, 8.6 ꢄ 10ꢂ7; 3, 4.3 ꢄ 10ꢂ7 mol dmꢂ3. Slit
widths: see Section 2.
4. Conclusions
Functionalization of 40-ethynyl-2,20:6’,200-terpyridine with
Ph3PAu, (2-tolyl)3PAu or Au(dppe)Au units leads to the compounds
1–3 respectively which have been characterized spectroscopically
in solution and by single crystal X-ray diffraction studies. In the so-
lid state, molecules of 1 or 2 are arranged in domains of tpy or
R3PAu units; in 2, the tpy units engage in face-to-face p-stacking,
but analogous interactions are not observed in 1. Compound 3
crystallizes as 2(3).CHCl3; the dppe backbone adopts a folded con-
formation, bringing the two gold(I) centres within 2.9470(8) Å of
one another, but
p-stacking of the tpy domains is prevented by a
guested CHCl3 molecule. Compounds 1–3 are emissive in CH2Cl2
solution, but over a period of minutes when kex = 230 nm, the
emission bands decay, consistent with the photodegradation of
the compounds.
Fig. 10. Emission spectrum of 1 recorded approximately each minute over a 10 min
period (kex = 230 nm; ⁄first harmonic).
tions that give rise to the observed absorption spectra are most
Acknowledgements
likely to be tpy/alkyne p⁄
p with Au orbital participation.
When irradiated at 289 nm, 40-ethynyl-2,20:60,200-terpyridine
emits at 351 nm with a high energy shoulder at 342 nm. On going
to compounds 1–3 (kex = 289 nm), the emission is resolved into
two clearly defined bands at 338 and 352 nm for 1, 339 and 353
for 2, and 342 and 352 nm for 3 (Fig. 9). Excitation spectra confirm
that the origins of these emissions are the broad absorptions be-
tween 230 and 300 nm shown in Fig. 8.
We thank the Swiss National Science Foundation and the Uni-
versity of Basel for financial support.
Appendix A. Supplementary data
CCDC 829106, 829107 and 829108 contain the supplementary
crystallographic data for 2 and 4. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Measurements of the emission spectra for compounds 1–3
were repeated approximately every minute over a period of 10–
15 min with kex = 230 nm. The emission bands (Fig. 9) decayed

2710
E.C. Constable et al. / Polyhedron 30 (2011) 2704–2710
[20] E.C. Constable, C.E. Housecroft, M.K. Kocik, M. Neuburger, S. Schaffner, J.A.
Zampese, Eur. J. Inorg. Chem. (2009) 4710.
[21] J. Vicente, J. Gil-Rubio, N. Barquero, P.G. Jones, D. Bautista, Organometallics 27
(2008) 646.
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
[22] X.-L. Li, K.-J. Zhang, J.-J. Li, X.-X. Cheng, Z.-N. Chen, Eur. J. Inorg. Chem. (2010)
3449.
References
[23] H. Schmidbaur, Chem. Soc. Rev. 24 (1995) 391.
[24] C.-M. Che, S.-W. Lai, in: F. Mohr (Ed.), Gold Chemistry, Wiley-VCH, 2009, p.
249.
[25] See for example: P. Li, B. Ahrens, K.-H. Choi, M.S. Khan, P.R. Raithby, P.J. Wilson,
W.-Y. Wong, CrystEngComm 4 (2002) 405.
[26] See for example: C. King, J.-C. Wang, N.I. Khan, J.P. Fackler Jr., Inorg. Chem. 28
(1989) 2145.
[1] H. Schmidbaur, A. Schier, in: R.H. Crabtree, D.M.P. Mingos (Eds.),
Comprehensive Organometallic Chemistry III, vol. 2, Elsevier, Oxford, 2007,
p. 251 (Chapter 5).
[2] N.J. Long, C.K. Williams, Angew. Chem., Int. Ed. 42 (2003) 2586.
[3] M.J. Irwin, J.J. Vittal, R.J. Puddephatt, Organometallics 16 (1997) 3541.
[4] J. Vicente, M.T. Chicote, M.D. Abrisqueta, M.M. Alvarez-Falcón, J. Organomet.
Chem. 663 (2002) 40.
[5] F. Mohr, D.J. Eisler, C.P. McArdle, K. Atieh, M.C. Jennings, R.J. Puddephatt, J.
Organomet. Chem. 670 (2003) 27.
[6] G. Hogarth, M.M. Alvarez-Falcón, Inorg. Chim. Acta 358 (2005) 1386.
[7] J. Vicente, M.-T. Chicote, M.M. Alvarez-Falcón, P.G. Jones, Organometallics 24
(2005) 2764.
[8] M.-A. MacDonald, R.J. Puddephatt, G.P.A. Yapp, Organometallics 19 (2000)
2194.
[9] W.J. Hunks, M.-A. MacDonald, M.C. Jennings, R.J. Puddephatt, Organometallics
19 (2000) 5063.
[10] F. Mohr, R.J. Puddephatt, J. Organomet. Chem. 689 (2004) 374.
[11] N.C. Habermehl, D.J. Eisler, C.W. Kirby, N.L.-S. Yue, R.J. Puddephatt,
Organometallics 25 (2006) 2921.
[12] H.-S. Tang, N. Zhu, V.W.-W. Yam, Organometallics 26 (2007) 22.
[13] E.R.T. Tiekink, J.-G. Kang, Coord. Chem. Rev. 253 (2009) 1627.
[14] V.W.-W. Yam, E.C.-C. Cheng, Chem. Soc. Rev. 37 (2008) 1806.
[15] J. Vicente, M.T. Chicote, M.M. Alvarez-Falcón, Organometallics 23 (2004) 5707.
[16] R. Packheiser, A. Jakob, P. Ecorchard, B. Walfort, H. Lang, Organometallics 27
(2008) 1214.
[27] See for example: C.-M. Che, H.-L. Kwong, V.W.-W. Yam, K.-C. Cho, Chem.
Commun. (1989) 885.
[28] V. Grosshenny, F.M. Romero, R. Ziessel, J. Org. Chem. 62 (1997) 1491.
[29] M.I. Bruce, E. Horn, J.G. Matisons, M.R. Snow, Aust. J. Chem. 37 (1984) 1163.
[30] Stoe & Cie, IPDS Software v 1.26, Stoe & Cie, Darmstadt, Germany, 1996.
[31] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[32] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[33] I.J. Bruno, J.C. Cole, P.R. Edgington, M.K. Kessler, C.F. Macrae, P. McCabe, J.
Pearson, R. Taylor, Acta Crystallogr., Sect. B 58 (2002) 389.
[34] C.F. Macrae, I.J. Bruno, J.A. Chisholm, P.R. Edgington, P. McCabe, E. Pidcock, L.
Rodriguez-Monge, R. Taylor, J. van de Streek, P.A. Wood, J. Appl. Crystallogr. 41
(2008) 466.
[35] E.C. Constable, C.E. Housecroft, M. Neuburger, S. Schaffner, E.J. Shardlow,
Polyhedron 27 (2008) 65.
[36] F. Mendizabal, P. Pyykkö, N. Runeberg, Chem. Phys. Lett. 370 (2003) 733.
[37] P. Pyykkö, Angew. Chem., Int. Ed. 41 (2002) 3573.
[38] D. Li, X. Hong, C.M. Che, W.C. Lo, S.M. Peng, J. Chem. Soc., Dalton Trans. (1993)
2929.
[39] M. Ferrer, A. Gutierrez, L. Rodriguez, O. Rossell, J.C. Lima, M. Font-Bardia, X.
Solans, Eur. J. Inorg. Chem. (2008) 2899.
[40] V.W.-W. Yam, S.W.-K. Choi, K.-K. Cheung, Organometallics 15 (1996) 1734.
[41] V.W.-W. Yam, S.W.-K. Choi, J. Chem. Soc., Dalton Trans. (1996) 4227.
[42] Y. Bao, C. Zhong, D.M. Vu, J.P. Temirov, R.B. Dyer, J.S. Martinez, J. Phys. Chem. C
111 (2007) 12194.
[17] M. Ferrer, M. Mounir, L. Rodríguez, O. Rossell, S. Coco, P. Gómez-Sal, A. Martín,
J. Organomet. Chem. 690 (2005) 2200.
[18] H.-Y. Chao, W. Lu, M.C.W. Chan, C.-M. Che, K.-K. Cheung, N. Zhu, J. Am. Chem.
Soc. 124 (2002) 14696.
[19] M. Ferrer, L. Rodríguez, O. Rossell, F. Pina, J.C. Lima, M.F. Bardia, X. Solans, J.
Organomet. Chem. 678 (2003) 82.