Design, synthesis, characterization, luminescence and non-linear optical (NLO) properties of multinuclear platinum(ii) alkynyl complexes

View Article Online / Journal Homepage / Table of Contents for this issue

This article is published as part of the Dalton Transactions themed issue entitled:

Dalton Transactions 40th Anniversary

Guest Editor Professor Chris Orvig, Editorial Board Chair

University of British Columbia, Canada

Published in issue 40, 2011 of Dalton Transactions

Image reproduced with permission of Shinobu Itoh

Welcome to issue 40 of the 40th volume of Dalton Transactions-40/40! Articles in the issue include:

PERSPECTIVE:

Synthesis and coordination chemistry of macrocyclic ligands featuring NHC donor groups

Peter G. Edwards and F. Ekkehardt Hahn

Dalton Trans., 2011, 10.1039/C1DT10864F

FRONTIER:

The future of metal–organic frameworks

Neil R. Champness

Dalton Trans., 2011, DOI: 10.1039/C1DT11184A

ARTICLES:

Redox reactivity of photogenerated osmium(II) complexes

Jillian L. Dempsey, Jay R. Winkler and Harry B. Gray

Dalton Trans., 2011, DOI: 10.1039/C1DT11138H

Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with

transition metal dications

Andrew Stephenson and Michael D. Ward

Dalton Trans., 2011, DOI: 10.1039/C1DT10263J

Visit the Dalton Transactions website for more cutting-edge inorganic and organometallic research

www.rsc.org/dalton

Dynamic Article Links

Dalton

Transactions

Cite this: Dalton Trans., 2011, 40, 10670

www.rsc.org/dalton

PAPER

Design, synthesis, characterization, luminescence and non-linear optical

(NLO) properties of multinuclear platinum(^II) alkynyl complexes†

Carmen Ka Man Chan,^aChi-Hang Tao,^aKing-Fai Li,^bKeith Man-Chung Wong,^aNianyong Zhu,^a

Kok-Wai Cheah*^band Vivian Wing-Wah Yam*^a

Received 28th April 2011, Accepted 19th July 2011

DOI: 10.1039/c1dt10784d

A series of luminescent multinuclear platinum(II) alkynyl complexes containing triethynylbenzene or

1,4-bis(3,5-diethynylphenyl)buta-1,3-diyne as cores has been successfully synthesized and

characterized. The electronic absorption, emission, nanosecond transient absorption and

electrochemical properties of these complexes have been reported. These complexes show long-lived

emissions in degassed benzene solution and in alcoholic glass at 77 K. Moreover, they are found to

exhibit two-photon absorption (2PA) and two-photon induced luminescence (TPIL) properties, and

their two-photon absorption cross-sections have been determined to be 6–191 GM upon excitation at

720 nm. Through a systematic comparison, it has been found that tetra- and hexanuclear platinum(II)

complexes show better 2PA and TPIL properties than their di- and trinuclear counterparts.

4,4¢,4¢¢-trisubstituted triphenylamine,⁸truxene,⁹as well as 1,3,5-

Introduction

tricyanobenzene,¹⁰1,3,5-trisubstituted benzene¹¹and others,¹²

There has been a growing interest in the development of hy-

which have been reported to show large two-photon absorption

perbranched molecules due to their attractive properties, such

cross-sections, preparation of organic materials with large two-

as physical,¹catalytic,²electrochemical,³energy transfer⁴and

photon absorption cross-sections could be achieved by using these

non-linear optical (NLO) properties.⁵Owing to their various

molecular design approaches.

applications, the discovery and search for new functional materials

Meanwhile, luminescence studies of transition metal complexes

has been one of the challenging goals in synthetic chemistry.

have attracted much attention, especially their triplet excited states

Conjugated systems with 1,2-, 1,3- and 1,4-diethynylphenyl and

that show phosphorescence due to large spin–orbit coupling in

1,3,5-triethynylphenyl units as cores have been employed for the

the presence of heavy metal centres. In addition to the study of

preparation of aromatic compounds with multiple ethynyl groups,

organic compounds and their non-linear optical behaviour, the

with poly(phenylethynylene)s, poly(yne) chains and with dendritic

study of metal complexes with non-linear optical properties has

structures. The structural properties of linear phenylenethynylenes

also aroused much attention in recent years. Some transition metal

have been investigated, and a correlation with their optical

complexes reported by various groups have shown interesting non-

properties has been studied.⁶Octupolar ethynylbenzenes, with C₃

symmetry, have also gained much attention for the exploration

of their NLO properties.⁷They are also suitable candidates for

the construction of carbon-rich building blocks with various

applications due to their high solubilities and good processabilities.

There has also been an ongoing search for new organic

compounds that are applicable to the development of new optical

materials and optoelectronic devices. With the studies of new

organic cores with two-photon absorption properties, such as

linear optical properties.^13–17

Unlike some rather intensively coloured organometallic com-

plexes that have been extensively studied for their non-linear

optical properties, platinum(II) phosphine alkynyl complexes are

believed to have some prospective advantages over their coloured

counterparts as a result of their high linear transmission in the

visible range and large spin–orbit coupling.^18–20Their negligible

absorptions in the visible region have rendered them promising

optical limiters in the visible region.^18c,d,21,22Organometallic poly-

meric materials have also attracted increasing interest since the

ﬁrst soluble platinum(II) and palladium(II) polyynyl complexes

were reported by Hagihara and coworkers.²³Since then, various

platinum(II) phosphine complexes, oligomers and metallopoly-

mers with different spacers and chain lengths have been reported

by Lewis,²⁴Raithby,²⁵Yam,^26,27Schanze,^19,28Gladysz,²⁹Cooper,³⁰

Wong³¹and others.^23,32Recent works by various researchers have

shown that besides polymeric materials, platinum(II) alkynyl com-

plexes could serve as promising and versatile building blocks for

^aInstitute of Molecular Functional Materialsb, Department of Chemistry

and HKU-CAS Joint Laboratory of New Materials, The University of Hong

Kong, Pokfulam Road, Hong Kong, P. R. China. E-mail: wwyam@hku.hk;

Fax: (852) 2857 1586; Tel: (852) 2859 2153

^bCentre for Advanced Luminescence Materials and Department of Physics,

Hong Kong Baptist University, Kowloon, Hong Kong, P.R. China.

E-mail: kwcheah@hkbu.edu.hk; Tel: (852) 3411 7029

† CCDC reference number 823518. For crystallographic data in CIF or

other electronic format see DOI: 10.1039/c1dt10784d

‡ Areas of Excellence Scheme, University Grants Committee (Hong Kong)

10670 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

the construction of multinuclear luminescent complexes.^{23,26,27,33,34}

The substitution of chloro ligands in the platinum(II) precursor

complexes could provide a facile synthetic pathway for the

construction of branched carbon-rich luminescent organometallic

materials.^33b,cWorks by Takahashi,³³Stang,³⁴and Yam^26a,b,dhave

shown that 1,3,5-triethynylbenzene could serve as a building block

for the construction of organoplatinum dendrimers. In addition,

the employment of platinum(II) alkynyl complexes and polymers in

the ﬁeld of NLO, such as optical limiting, two-photon absorption

and two-photon induced luminescence, has aroused numerous

attention.^{15–18a,26e,27,35}

(ⁿBu₄NF) (1 M solution in THF, Lancaster) and ﬂuorescein

(Acros, 99% pure, laser grade) were purchased and used as

received. All solvents were puriﬁed and distilled using standard

procedures before use. All other reagents were of analytical

grade and were used as received. All amines were distilled over

potassium hydroxide and stored in the presence of potassium

hydroxide prior to use.

Physical measurements and instrumentation

¹H NMR spectra were recorded on Bruker DPX 300 (300 MHz) or

Bruker DPX 400 (400 MHz) Fourier-transform NMR spectrom-

eters with chemical shifts reported relative to tetramethylsilane

Although organoplatinum(II) dendrimers with 1,3,5-

triethynylbenzene have been previously studied,^{26a,b,d,33,34}

metal complexes with 1,4-bis(3,5-diethynylphenyl)buta-1,3-

diyne as the core have been less explored. Recently, our

group has demonstrated that trinuclear platinum(II) alkynyl

complexes with carbazole, truxene and extended 1,3,5-

triethynylbenzene as the cores exhibited interesting two-photon

absorption properties.^26,27Although the incorporation of bis((4-

(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine))platinum(II)

into dendrimers has been reported,^18athe use of multinuclear

platinum(II) alkynyl with branched or dendritic phenyleneethylene

backbones in NLO studies has been relatively less explored. As

an extension of previous works and the recent efforts in the

design and synthesis of linear and branched luminescent metal

alkynyl complexes with various metal centres,^26,27,36herein, we

report the design and synthesis of a series of multinuclear

branched platinum(II) alkynyl complexes, with the use of

two organic building blocks, 1,3,5-triethynylbenzene and 1,4-

bis(3,5-diethynylphenyl)buta-1,3-diyne. With the employment

of the branched platinum(II) precursor [(ⁱPr₃SiC C)-1-

C₆H₃{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,5] previously reported by

our group,^26da series of luminescent multinuclear platinum(II)

alkynyl complexes has been synthesized and characterized

(Chart 1 and 2). Their luminescence properties of the complexes

with different cores and peripheral aryl alkynyl ligands have

also been studied. The excited state properties of some of

the complexes have been probed using nanosecond transient

absorption spectroscopy. The X-ray crystal structure of [{(C C)-

1-C₆H₃{(C₆H₄C C)-2-oxa-(C₆H₅)-5-(PEt₃)₂PtC C}₂-3,5}₂] (9)

has also been determined.

1

(Me₄Si) while ¹³C{ H} and ³¹P{ H} spectra wererecorded either on

a Bruker DPX 400 or a Bruker DPX 500 Fourier-transform NMR

spectrometer with chemical shifts reported relative to Me₄Si and

85% H₃PO₄, respectively. Positive-ion fast-atom bombardment

(FAB) mass spectra were recorded on Finnigan MAT95 mass

spectrometer. IR spectra were obtained using KBr disks on a Bio-

Rad FTS-7 Fourier-transform infrared spectrophotometer (4000–

400 cm^-1). Elemental analyses were performed on a Flash EA 1112

elemental analyzer at the Institute of Chemistry, Chinese Academy

of Sciences in Beijing.

The UV-visible absorption spectra were obtained by using a

Hewlett-Packard 8452 A diode array spectrophotometer. Steady-

state excitation and emission spectra at room temperature and

at 77 K were recorded on a Spex Fluorolog-2 Model F111

ﬂuorescence spectroﬂuorometer. Solid-state photophysical studies

were carried out with solid samples contained in a quartz tube

inside a quartz-walled Dewar ﬂask. Measurements of the ethanol–

methanol (4 : 1, v/v) glass or solid-samples at 77 K were conducted

by using liquid nitrogen ﬁlled in the optical Dewar ﬂask. All

solutions for photophysical studies were degassed with a high-

vaccum line on a two-compartment cell consisting of a 10 mL

Pyrex bulb and a quartz cuvette (1 cm path length) and sealed

from the atmosphere by a Bibby Rotaﬂo HP6 Telfon stopper. The

solutions were rigorously degassed with at least four successive

freeze–pump–thaw cycles. Emission lifetime measurements were

performed by using a conventional laser system. The excitation

source was a 355-nm output (third harmonic) from a Spectra-

Physics Quanta-Ray Q-switch GCR-150-10 pulsed Nd : YAG

laser. Luminescence decay signals were detected by a Hamamatsu

R928 photomultiplier tube, recorded on a Tektronix Model TDS-

620 A (500 MHz, 2 GS s^-1) digital oscilloscope, and analyzed by

using a program for exponential ﬁts.

Experimental

Materials and reagents

Photoluminescence quantum yields were measured by the

optical dilute method reported by Demas and Crosby.⁴¹An

aqueous solution of quinine sulfate in 0.5 M H₂SO₄has been used

as the reference and all samples were irradiated at 365 nm since all

the complexes absorb strongly in this region. The refractive indices

of the samples and the reference solution are 1.501 and 1.333,

respectively. The luminescence quantum yield of the reference is

0.55 with excitation wavelength at 365 nm.⁴¹

The two-photon absorption (2PA) cross-section (s₂) could

be determined by two main methods.^42a,bTwo-photon induced

luminescence (TPIL) is one of the methods to determine s₂in

which the luminescence intensity generated by 2PA was measured

and used to estimate the s₂values according to eqn (1). An

unknown sample is compared to a reference with known s₂values.

Me₃SiC CC₆H₄-aza-15-crown-5,³⁷(HC C)₃-C₆H₃-1,3,5,³⁸(HC

CC₆H₄)-2-oxa-C₆H₅-5,³⁹[{Cl(PEt₃)₂PtC CC₆H₄}₂-oxa-2,5],^27a

and

[(ⁱPr₃SiC C)-1-C₆H₃-{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,

5]^26dwere synthesized according to literature reported

synthetic procedures. trans-[(MeC₆H₄C C)(PEt₃)₂PtCl], trans-

[(MeOC₆H₄C C)(PEt₃)₂PtCl], trans-[(C₆H₅C C)(PEt₃)₂PtCl]

and trans-[{(C₆H₄C C)-2-oxa-(C₆H₅)-5}-(PEt₃)₂PtCl] were

synthesized according to the literature procedures.^26d,27a{(C C)-

40

1-C₆H₃-(C CSiⁱPr₃)₂-3,5}₂

was synthesized with a slight

modiﬁcation of a literature procedure using Cu(OAc)₂instead of

CuI. trans-Dichlorobis(triethylphosphine)platinum(II) (Aldrich,

98%), 1-ethynyltoluene (GFS, 98%), 1-ethynyl-4-methoxybenzene

(Maybridge, 97%), tetrabutylammonium ﬂuoride solution

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10671

©

Chart 1 Synthesis of di- and trinuclear branched platinum(II) complexes.

Fluorescein (1 ¥ 10^-4M in 0.1 M NaOH aqueous solution) has

where s₂is the two-photon absorption cross-section, C is the

concentration, n is refractive index, U is the luminescence quantum

yield and S is the integrated luminescence signal. The subscripts r

and s represent the reference and the sample material respectively.

The s₂and luminescence quantum yield of ﬂuorescein in 0.1 M

NaOH solution (pH ~ 11) at 720 nm were taken to be 19 GM

been used as the reference in the present study.^42c

C_rn_rΦS_s

r

s_2(s)

=

s_2(r)

(1)

C_sn_sΦS_r

s

10672 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

Chart 2 Synthesis of tetra- and hexanuclear branched platinum(II) complexes.

(Gøppert–Mayer, 1 GM = 1 ¥ 10^-50cm⁴s photon^-1molecule^-1)

generative ampliﬁer (Spectra-Physics, Spitﬁre) with pulse duration

of ~120 fs and repetition rate of 1 kHz. The 720-nm laser output

from the OPA (Coherent, TOPAS-C light conversion) was used

as the excitation source. The laser output was passed through the

sample cell and the luminescence intensity was monitored by the

spectrometer system with the monochromator (ACTON Research

and 0.90, respectively.^42cThe time-averaged laser power at 720 nm

was kept constant for the sample and the reference. The laser pulses

were generated by a mode-locked Ti : Sapphire laser (Spectra-

Physics, Tsunami) operating at a repetition rate of 85 MHz. The

pulses were ampliﬁed up to 1 mJ per pulse by the Ti : Sapphire re-

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10673

©

◦

n

Corporation, SpectraPro 2300i) and photomultiplier tube (Hama-

matsu, R636-10). For the power dependence measurements, the

laser beam power was altered by using two polarizers, which

was partially reﬂected to a photodiode for the monitoring of

the excitation power. The schematic diagram for the experimental

setup has been described elsewhere.^27a

dichloromethane (30 mL) and cooled to 0 C. Bu₄NF (2.9 mL,

1 M in THF solution) was added. The mixture was immediately

raised to room temperature and stirred under nitrogen for 2 h.

It was then quenched by deionized water. The orange solution

was successively washed with aqueous ammonium chloride

solution and deionized water. The organic fraction was dried

over anhydrous MgSO₄and ﬁltered. The solvent was evaporated

under reduced pressure. Further puriﬁcation was accomplished

by column chromatography on silica gel (70–230 mesh) with

n-hexane–dichloromethane (2 : 1, v/v) as eluent. Subsequent

recrystallization of the crude product from dichloromethane–

methanol afforded L2 as a pale orange solid. Yield: 0.08 g (56%).

¹H NMR (400 MHz, CDCl₃, 298 K, relative to Me₄Si): d 3.17 (s,

4H; –C CH), 7.65 (s, 6H; –C₆H₃–). Positive-ion EI: m/z: 298

[M]⁺. Elemental analysis calcd (%) for L2·0.5CH₃OH: C 93.60, H

3.85; found: 93.85, H 3.61.

Transient absorption measurements were performed on a

LP920-KS Laser Flash Photolysis Spectrometer (Edinburgh In-

struments Ltd, Livingston, UK) at room temperature. The excita-

tion source was the 355-nm output (third harmonic) of a Nd : YAG

laser (Spectra-Physics Quanta-Ray Lab-130 Pulsed Nd : YAG

Laser) and the probe light source was a Xe900 450 W xenon

arc lamp. The transient absorption spectra were detected by an

image intensiﬁed CCD camera (Andor) with PC plug-in controller,

operated by L900 spectrometer software. The absorption kinetics

were detected by a Hamamatsu R928 photomultiplier tube and

recorded on a Tektronix Model TDS3012B (100 MHz, 1.25 GS

s^-1) digital oscilloscope and analyzed using the same software

for exponential ﬁt (tail-ﬁt data analysis). Samples were freshly

prepared and degassed with at least four freeze–pump–thaw cycles

on a high-vacuum line in a two-compartment cell consisting of a

10 mL Pyrex bulb and a 1 cm path length quartz cuvette.

Cyclic voltammetric measurements were performed using

a CH Instruments, Inc., model CHI 750A electrochemical

analyzer. Electrochemical measurements were performed in

dichloromethane solutions with 0.1 M ⁿBu₄NPF₆as the support-

ing electrolyte at room temperature. The reference electrode was

a Ag/AgNO₃(0.1 M in acetonitrile) electrode and the working

electrode was a glassy carbon electrode (CH Instruments, Inc.)

with a platinum wire as the counter electrode. The working

electrode surface was ﬁrst polished with 1 mm alumina slurry

(CH Instruments, Inc.) and then with 0.3 mm alumina slurry (CH

Instruments, Inc.) on a microcloth (Buehler Co.). It was rinsed with

ultrapure deionized water and sonicated in a beaker containing

ultrapure deionized water for ﬁve minutes. The polishing and

sonicating steps were repeated twice and then the working

electrode was rinsed under a stream of ultrapure deionized water.

The ferrocenium/ferrocene couple (FeCp₂^+/0) was used as the

internal reference.⁴³All solutions for electrochemical studies were

deaerated with prepuriﬁed argon gas prior to measurements.

[Cl(PEt₃)₂Pt(C CC₆H₄-aza-15-crown-5)] (1). This was syn-

thesized according to a modiﬁed literature procedure for the

related platinum(II) phosphine alkynyl complex.^26d,27aL1 (0.13 g,

0.41 mmol) and trans-[Pt(PEt₃)₂Cl₂] (0.41 g, 0.82 mmol) were

dissolved in a mixture of toluene (70 mL) and piperidine (5 mL).

The reaction mixture was heated to reﬂux for 30 min; after which

CuI (5 mg, 0.03 mmol) was added and the reaction mixture was

then heated to reﬂux under nitrogen for two days. The solvent

was removed under reduced pressure. Further puriﬁcation was

accomplished by column chromatography on basic aluminium

oxide (50–200 mm), in which the excess trans-[Pt(PEt₃)₂Cl₂] was

ﬁrst eluted with dichloromethane–n-hexane (1 : 1, v/v), followed

by the elution of 1 with dichloromethane–acetone (10 : 1, v/v).

Yield: 0.24 g (75%). ¹H NMR (400 MHz, CDCl₃, 298 K, relative to

Me₄Si): d 1.15–1.23 (virtual quintet (vq), 18H, J = 8.0 Hz; –CH₃),

2.02–2.10 (m, 12H; –CH₂P), 3.55–3.61 (m, 4H; –NCH₂–), 3.63–

3.69 (m, 12H; –CH₂OCH₂–), 3.72–3.74 (m, 4H; –CH₂OCH₂–),

6.53 (d, 2H, J = 8.9 Hz; –C₆H₄–), 7.12 (d, 2H, J = 8.9 Hz; –

C₆H₄–). ³¹P{ H} NMR (162 MHz, CDCl₃, 298 K, relative to 85%

1

H₃PO₄): d 14.64 (s, J_Pt–P= 2407 Hz). Positive-ion FAB-MS: m/z:

786 [M + 1]⁺.

[Pt(PEt₃)₂{(C CC₆H₄)-2-oxa-C₆H₅-5}₂] (2). This was syn-

thesized according to a literature procedure for the related

platinum(II) phosphine alkynyl complexes.^26d,27a(HC CC₆H₄)-2-

oxa-C₆H₅-5 (0.26 g, 1.06 mmol) and trans-[Pt(PEt₃)₂Cl₂] (0.24 g,

0.48 mmol) were dissolved in a mixture of THF (20 mL) and Et₃N

(10 mL). CuI (5 mg, 0.03 mmol) was added to this reaction mixture

as a catalyst. The yellow mixture was stirred under nitrogen at

room temperature for 3 days; after which the solvent was removed

under reduced pressure. The orange residue was then dissolved in

dichloromethane, washed successively with brine and deionized

water, and dried over anhydrous Na₂SO₄. The solution was then

ﬁltered, and the solvent was removed under reduced pressure. The

orange residue was subjected to column chromatography on basic

aluminium oxide (50–200 mm), in which the excess (HC CC₆H₄)-

2-oxa-C₆H₅-5 was ﬁrst eluted with dichloromethane followed by

the elution of 2 with dichloromethane–acetone (20 : 1, v/v). Yield:

Syntheses

HC CC₆H₄-aza-15-crown-5 (L1). This was synthesized

according to modiﬁcation of

a

literature procedure.⁴⁴

Me₃SiC CC₆H₄-aza-15-crown-5 (0.52 g, 1.33 mmol) was

dissolved in dichloromethane (25 mL) and cooled to 0 ^◦C and

ⁿBu₄NF (4.0 mL, 4.01 mmol) was added. The mixture was stirred

under nitrogen for 4 h at 0 ^◦C. The reaction was monitored

by TLC until no starting materials was observed. It was then

evaporated to dryness under reduced pressure. The residue was

subjected to column chromatography on silica gel (70–230 mesh)

with chloroform as the eluent. Yield: 0.21 g (49%). ¹H NMR (400

MHz, CDCl₃, 298 K, relative to Me₄Si): d 2.96 (s, 1H; –C CH),

3.58–3.61 (m, 4H; –NCH₂–), 3.63–3.67 (m, 12H; –CH₂OCH₂–),

3.73–3.76 (m, 4H; –CH₂OCH₂–), 6.57 (d, 2H, J = 9.0 Hz; –C₆H₄–),

7.33 (d, 2H, J = 9.0 Hz; –C₆H₄–).

1

0.27 g (61%). H NMR (400 MHz, CDCl₃, 298 K, relative to

Me₄Si): d 1.22–1.30 (vq, 18H, J = 8.2 Hz; –CH₃), 2.17–2.24

(m, 12H; –CH₂P), 7.40 (d, 4H, J = 8.2 Hz; –C₆H₄–), 7.51–

7.55 (m, 6H; –C₆H₅), 7.99 (d, 4H, J = 8.2 Hz; –C₆H₄–), 8.13–

{(C C)-1-C₆H₃-(C CH)₂-3,5}₂

(L2). {(C C)-1-C₆H₃-

(C CSiⁱPr₃)₂-3,5}₂(0.44 g, 0.47 mmol) was dissolved in

10674 | Dalton Trans., 2011, 40, 10670–10685

8.15 (d, 4H, J = 8.9 Hz; –C₆H₅). ¹³C{ H} NMR (126 MHz,

1

This journal is

The Royal Society of Chemistry 2011

©

CDCl₃, 298 K, relative to Me₄Si): d 8.40 (–CH₃), 16.46 (t, J_C–P

17.5 Hz; –CH₂P), 109.88 (Pt–C C–C), 113.60 (Pt–C C–C),

=

n/cm^-1): 2099 (s), 2205 (w) n(C C). Positive-ion FAB-MS: m/z:

1474 [M + 1]⁺. Elemental analysis calcd (%) for 4: C 57.06, H 5.88;

found: C 57.02, H 5.96.

120.05, 124.10, 126.65, 126.89, 129.07, 131.36, 131.60, 132.46

1

(aromatic C’s), 164.31, 164.84 (C in oxa ring). ³¹P{ H} NMR (162

[(HC C)-1-C₆H₃{(C₆H₄C C)-2-oxa-(C₆H₅)-5-(PEt₃)₂PtC

CC₆H₄C C}₂-3,5] (5). The procedure was similar to that for 3

except that (HC CC₆H₄)-2-oxa-(C₆H₅)-5 (0.17 g, 0.68 mmol) was

used instead of 1-ethynyltoluene. Subsequent recrystallization of

the crude product from dichloromethane–methanol afforded 5 as

MHz, CDCl₃, 298 K, relative to 85% H₃PO₄): d 11.41 (s, J_Pt–P

=

2348 Hz). IR (KBr disk, n/cm^-1): 2098 (s) n(C C). Positive-ion

FAB-MS: m/z: 923 [M]⁺. Elemental analysis calcd (%) for 2: C

57.32, H 5.25, N 6.08; found: C 57.17, H 5.36, N 6.10.

1

[(HC C)-1-C₆H₃{(MeC₆H₄C C)(PEt₃)₂PtC CC₆H₄C C}₂-

a bright yellow solid. Yield: 0.19 g (66%). H NMR (400 MHz,

3,5] (3). This was synthesized according to

a modiﬁed

CDCl₃, 298 K, relative to Me₄Si): d 1.21–1.29 (vq, 36H, J = 8.0 Hz;

–CH₃), 2.17–2.21 (m, 24H; –CH₂P), 3.10 (s, 1H; –C CH), 7.25

(d, 4H, J = 8.8 Hz; –C₆H₄–), 7.38 (t, 8H, J = 8.8 Hz; –C₆H₄–),

7.53–7.57 (m, 8H; –C₆H₄– and –C₆H₃–), 7.64 (t, 1H, J = 1.4 Hz;

–C₆H₃–), 7.99 (d, 4H; J = 8.2 Hz; –C₆H₄–), 8.12–8.14 (m, 4H; –

literature

phosphine

procedure

alkynyl

for

the

related platinum(II)

[(ⁱPr₃SiC C)-1-

complexes.^26d

C₆H₃{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,5] (0.25 g, 0.17 mmol)

and 1-ethynyltoluene (0.08 g, 0.68 mmol) were dissolved in

a mixture of THF (20 mL) and Et₃N (10 mL). CuI (5 mg,

0.03 mmol) was added to this reaction mixture as a catalyst.

The yellow mixture was then stirred under nitrogen at room

temperature overnight; after which the solvent was removed

under reduced pressure. The yellow residue was then dissolved in

dichloromethane, washed successively with brine and deionized

water, and dried over anhydrous MgSO₄. The solution was then

ﬁltered, and the solvent was removed under reduced pressure. The

yellow residue was subjected to column chromatography on basic

aluminium oxide (50–200 mm) with dichloromethane–n-hexane

(1 : 3, v/v) as the eluent. Subsequent recrystallization of the

crude product from dichloromethane–methanol afforded the

ⁱPr₃Si-protected complex as a yellow solid. It was then dissolved

in dichloromethane (15 mL) and cooled to 0 ^◦C. ⁿBu₄NF (1.0 mL,

1 M solution in THF) was added and the reaction mixture was

stirred under nitrogen at room temperature for 2 h. The reaction

was quenched by addition of deionized water. The organic phase

was collected, dried over anhydrous MgSO₄and ﬁltered after

extraction. Subsequent recrystallization of the crude product

from dichloromethane–methanol afforded 3 as a dull yellow

1

C₆H₄–). ³¹P{ H} NMR (162 MHz, CDCl₃, 298 K, relative to 85%

H₃PO₄): d 11.35 (s, J_Pt–P= 2353 Hz). IR (KBr disk, n/cm^-1): 2097

(s), 2203 (w) n(C C). Positive-ion FAB-MS: m/z: 1702 [M]⁺.

Elemental analysis calcd (%) for 5: C 59.29, H 5.33, N 3.29; found:

C 59.31, H 5.37, N 3.42.

[{(C₆H₅C C)(PEt₃)₂PtC C}-1-C₆H₃{(C₆H₄C C)-2-oxa-

C₆H₅-5-(PEt₃)₂PtC CC₆H₄C C}₂-3,5] (6). The procedure

was similar to that for 2 except that 5 (0.09 g, 0.05 mmol) and

trans-[(C₆H₅C C)(PEt₃)₂PtCl] (0.10 g, 0.18 mmol) were used

instead of (HC CC₆H₄)-2-oxa-C₆H₅-5 and trans-[Pt(PEt₃)₂Cl₂].

The yellow residue was subjected to column chromatography on

basic aluminium oxide (50–200 mm), in which the excess trans-

[(C₆H₅C C)(PEt₃)₂PtCl] was ﬁrst eluted with dichloromethane–

n-hexane (2 : 1, v/v), followed by the elution of

6 with

dichloromethane–acetone (10 : 1, v/v). Subsequent recrystalliza-

tion of the crude product from dichloromethane–n-hexane af-

1

forded 5 as a light yellow solid. Yield: 0.07 g (63%). H NMR

(400 MHz, CDCl₃, 298 K, relative to Me₄Si): d 1.21–1.29 (vq,

54H, J = 8.0 Hz; –CH₃), 2.17–2.21 (m, 36H; –CH₂P), 7.28 (d, 4H,

J = 7.8 Hz; –C₆H₄–), 7.34 (d, 2H, J = 1.5 Hz; –C₆H₃–), 7.39 (t, 12H,

J = 8.8 Hz; –C₆H₄–), 7.44 (t, 1H, J = 1.5 Hz; –C₆H₃–), 7.52–7.55

(m, 7H; –C₆H₄– and –C₆H₅), 7.99 (d, 4H; J = 8.2 Hz; –C₆H₄–),

1

solid. Yield: 0.17 g (69%). H NMR (400 MHz, CDCl₃, 298 K,

relative to Me₄Si): d 1.18–1.26 (vq, 36H, J = 8.0 Hz; –CH₃),

2.14–2.21 (m, 24H; –CH₂P), 2.30 (s, 6H; –C₆H₄CH₃), 3.10 (s, 1H;

–C CH), 7.02 (d, 4H, J = 7.9 Hz; –C₆H₄–), 7.18 (d, 4H, J =

7.9 Hz; –C₆H₄–), 7.24 (d, 4H, J = 8.3 Hz; –C₆H₄–), 7.35 (d, 4H,

J = 8.3 Hz; –C₆H₄–), 7.59 (d, 2H, J = 1.4 Hz; –C₆H₃–), 7.63 (t, 1H,

1

8.13–8.15 (m, 4H; –C₆H₄–). ¹³C{ H} NMR (126 MHz, CDCl₃,

298 K, relative to Me₄Si): d 8.36, 8.50 (–CH₃), 16.39, 16.42 (t,

J_C–P= 17.5 Hz; –CH₂P), 89.36, 90.36 (–C C–), 109.73, 109.97 (Pt–

1

J = 1.4 Hz; –C₆H₃–). ³¹P{ H} NMR (162 MHz, CDCl₃, 298 K,

C

C–C), 119.45, 119.97 (Pt–C C–C), 123.48, 124.12, 125.03,

126.24, 126.63, 126.88, 127.87, 127.92, 128.84, 128.88, 129.05,

130.23, 130.79, 130.87, 130.95, 131.26, 131.32, 131.58, 132.54,

134.94, 135.03 (aromatic C’s), 164.29, 164.89 (C in oxa ring).

relative to 85% H₃PO₄): d 11.13 (s, J_Pt–P= 2369 Hz). IR (KBr disk,

n/cm^-1): 2099 (s), 2205 (w) n(C C). Positive-ion FAB-MS: m/z:

1442 [M]⁺. Elemental analysis calcd (%) for 3: C 58.33, H 6.01;

found: C 58.32, H 6.11.

1

³¹P{ H} NMR (162 MHz, CDCl₃, 298 K, relative to 85% H₃PO₄):

d 11.32 (s, J_Pt–P= 2361 Hz). IR (KBr disk, n/cm^-1): 2097 (s)

n(C C). Positive-ion FAB-MS: m/z: 2234 [M + 1]⁺. Elemental

analysis calcd (%) for 6·0.5C₆H₁₄: C 56.46, H 5.80, N 2.46; found:

C 56.54, H 5.60, N 2.66.

[(HC C)-1-C₆H₃{(MeOC₆H₄C C)(PEt₃)₂PtC CC₆H₄C

C}₂-3,5] (4). The procedure was similar to that for 3 except

that 1-ethynyl-4-methoxybenzene (0.09 g, 0.68 mmol) was used

instead of 1-ethynyltoluene. Subsequent recrystallization of the

crude product from dichloromethane–methanol afforded 4 as a

[{(aza-15-crown-5-C₆H₄C C)(PEt₃)₂PtC C}-1-C₆H₃-{(C₆H₄C

C)-2-oxa-C₆H₅-5-(PEt₃)₂PtC CC₆H₄C C}₂-3,5] (7). The

procedure was similar to that for 6 except that 1 (0.08 g, 0.10 mmol)

was used instead of trans-[(C₆H₅C C)(PEt₃)₂PtCl]. Subsequent

recrystallization of the crude product from dichloromethane–

methanol afforded 6 as a deep yellow solid. Yield: 0.08 g (65%). ¹H

NMR (400 MHz, CDCl₃, 298 K, relative to Me₄Si): d 1.21–1.29

(vq, 54H, J = 8.0 Hz; –CH₃), 2.16–2.21 (m, 36H; –CH₂P), 3.57

(t, 4H, J = 6.2 Hz; –NCH₂–), 3.64–3.67 (m, 12H; –CH₂OCH₂–),

1

yellow solid. Yield: 0.12 g (48%). H NMR (400 MHz, CDCl₃,

298 K, relative to Me₄Si): d 1.19–1.27 (vq, 36H, J = 8.0 Hz; –

CH₃), 2.14–2.21 (m, 24H; –CH₂P), 3.10 (s, 1H; –C CH), 3.78 (s,

6H; –C₆H₄OCH₃), 6.77 (d, 4H, J = 8.7 Hz; –C₆H₄–), 7.21 (d, 4H,

J = 8.7 Hz; –C₆H₄–), 7.24 (d, 4H, J = 8.2 Hz; –C₆H₄–), 7.35 (d, 4H,

J = 8.2 Hz; –C₆H₄–), 7.56 (d, 2H, J = 1.4 Hz; –C₆H₃–), 7.63 (t, 1H,

1

J = 1.4 Hz; –C₆H₃–). ³¹P{ H} NMR (162 MHz, CDCl₃, 298 K,

relative to 85% H₃PO₄): d 11.09 (s, J_Pt–P= 2368 Hz). IR (KBr disk,

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10675

©

3.74 (t, 4H, J = 6.2 Hz; –CH₂OCH₂–), 6.53 (d, 2H, J = 8.8 Hz;

–C₆H₄–), 7.16 (d, 2H, J = 8.8 Hz; –C₆H₄–), 7.24 (d, 4H, J =

8.4 Hz; –C₆H₄–), 7.34 (d, 2H, J = 1.5 Hz; –C₆H₃–), 7.38 (t, 8H,

J = 8.6 Hz; –C₆H₄–), 7.43 (t, 1H, J = 1.5 Hz; –C₆H₃–), 7.53–7.55

(m, 6H; –C₆H₅), 7.99 (d, 4H; J = 8.4 Hz; –C₆H₄–), 8.12–8.14 (m,

[{(C C)-1-C₆H₃{(MeC₆H₄C C)(PEt₃)₂PtC CC₆H₄C C}₂-

3,5}₂] (10). This was synthesized according to modiﬁcation of a

literature procedure for a homocoupling reaction.^45,46A solution

of 3 (0.10 g, 0.07 mmol) in the presence of Cu(OAc)₂(0.02 g,

0.11 mmol) in pyridine (15 mL) was stirred at 80 ^◦C for 48 h.

The solvent was removed under vacuum, and the greenish oily

residue was dissolved in dichloromethane and washed successively

with hydrochloric acid (1 M), aqueous sodium hydroxide (2 M)

and deionized water. The organic fraction was then dried over

MgSO₄and ﬁltered. The solvent was evaporated under reduced

pressure, and the residue was redissolved in dichloromethane

and puriﬁed by column chromatography on basic aluminium

oxide (50–200 mm), in which 10 was eluted with dichloromethane.

Subsequent recrystallization from dichloromethane–methanol

afforded 10 as a pale yellow solid. Yield: 0.06 g (30%). ¹H NMR

(400 MHz, CDCl₃, 298 K, relative to Me₄Si): d 1.19–1.26 (vq,

72H, J = 8.0 Hz; –CH₃), 2.14–2.21 (m, 48H; –CH₂P), 2.30 (s,

12H; –C₆H₄CH₃), 7.02 (d, 8H, J = 7.9 Hz; –C₆H₄–), 7.18 (d, 8H,

J = 7.9 Hz; –C₆H₄–), 7.24 (d, 8H, J = 8.2 Hz; –C₆H₄–), 7.36 (d,

8H, J = 8.2 Hz; –C₆H₄–), 7.60 (d, 4H, J = 1.3 Hz; –C₆H₃–), 7.66

1

4H; –C₆H₄–). ¹³C{ H} NMR (126 MHz, CDCl₃, 298 K, relative

to Me₄Si): d 8.32, 8.38 (–CH₃), 16.38, 16.43 (t, J_C–P= 17.5 Hz;

–CH₂P), 52.49 (–NCH₂–), 68.62, 68.64, 68.68 (–NCH₂CH₂O–),

70.19, 70.22 (–CH₂OCH₂–), 71.35 (–CH₂OCH₂–), 89.42, 89.99

(–C C–), 109.73, 109.99, 111.15, 111.21, 111.38 (Pt–C C–C),

115.71, 116.28, 119.49, 119.96 (Pt–C C–C), 123.44, 124.11,

126.33, 126.88, 128.84, 129.06, 129.27, 130.79, 131.58, 131.68,

131.91, 132.55, 133.35, 145.28 (aromatic C’s), 164.29, 164.85 (C

1

in oxa ring). ³¹P{ H} NMR (162 MHz, CDCl₃, 298 K, relative to

85% H₃PO₄): d 11.14 (s, J_Pt–P= 2369 Hz), 11.33 (s, J_Pt–P= 2356 Hz).

IR (KBr disk, n/cm^-1): 2097 (s) n(C C). Positive-ion FAB-MS:

m/z: 2451 [M + 1]⁺. Elemental analysis calcd (%) for 7·CH₂Cl₂: C

54.48, H 5.76, N 2.76; found: C 54.25, H 6.17, N 2.77.

[{(C C)-1-C₆H₃{(MeOC₆H₄C C)(PEt₃)₂PtC C}₂-3,5}₂]

(8). The procedure was similar to that for 7 except that L2

(0.02 g, 0.07 mmol) and trans-[(MeOC₆H₄C C)(PEt₃)₂PtCl]

(0.21 g, 0.35 mmol) were used instead of 5 and trans-

[(C₆H₅C C)(PEt₃)₂PtCl]. Subsequent recrystallization of the

crude product from dichloromethane–methanol afforded 8 as a

1

(t, 2H, J = 1.3 Hz; –C₆H₃–). ³¹P{ H} NMR (162 MHz, CDCl₃,

298 K, relative to 85% H₃PO₄): d 11.13 (s, J_Pt–P= 2368 Hz). IR

(KBr disk, n/cm^-1): 2099 (m) n(C C). Positive-ion FAB-MS:

m/z: 2881 [M]⁺. Elemental analysis calcd (%) for 10: C 58.37, H

5.95; found: C 58.35, H 5.98.

1

bright yellow solid. Yield: 0.12 g (65%). H NMR (400 MHz,

[ { ( C₆H₄C C ) ( PEt₃)₂PtC C } - 1 - C₆H₃{ ( MeC₆H₄C C ) -

(PEt₃)₂PtC CC₆H₄C C}₂- 3,5}₂-oxa-2,5] (11). The procedure

was similar to that for 6 except that 3 (0.13 g, 0.09 mmol)

and [{ClPt(PEt₃)₂C CC₆H₄}₂-oxa-2,5] (0.04 g, 0.03 mmol) were

used instead of 5 and trans-[Cl(PEt₃)₂Pt(C CC₆H₅)]. Subsequent

recrystallization of the crude product from dichloromethane–

methanol afforded 11 as a pale yellow solid. Yield: 0.08 g (60%).

¹H NMR (400 MHz, CDCl₃, 298 K, relative to Me₄Si): d 1.18–1.29

(vq, J = 8.0 Hz, 108H; –CH₃), 2.16–2.19 (m, 72H; –CH₂P), 2.29 (s,

12H; –C₆H₄CH₃), 7.02 (d, 8H, J = 8.0 Hz; –C₆H₄–), 7.18 (d, 8H,

J = 7.8 Hz; –C₆H₄–), 7.24 (d, 8H, J = 7.8 Hz; –C₆H₄–), 7.34 (d, 4H,

J = 1.1 Hz; –C₆H₃–), 7.36 (d, 8H, J = 8.0 Hz; –C₆H₄–), 7.39 (d, 4H,

J = 8.2 Hz; –C₆H₄–), 7.44 (t, 2H, J = 1.1 Hz; –C₆H₃–), 7.97 (d, 4H;

CDCl₃, 298 K, relative to Me₄Si): d 1.21–1.29 (vq, 72H, J =

8.0 Hz; –CH₃), 2.15–2.20 (m, 48H; –CH₂P), 3.78 (s, 12 H; –

C₆H₄OCH₃), 6.76 (d, 8H, J = 8.6 Hz; –C₆H₄–), 7.17 (s, 6H; –

1

C₆H₃–), 7.21 (d, 8H, J = 8.6 Hz; –C₆H₄–). ¹³C{ H} NMR (126

MHz, CDCl₃, 298 K, relative to Me₄Si): d 8.37 (–CH₃), 16.37 (t,

J_C–P= 17.5 Hz; –CH₂P), 55.27 (–C₆H₄OCH₃–), 104.56 (–C C–),

108.23, 108.92 (Pt–C C–C), 113.57 (Pt–C C–C), 121.10,

1

121.41, 128.87, 131.39, 131.96, 157.32 (aromatic C’s). ³¹P{ H}

NMR (162 MHz, CDCl₃, 298 K, relative to 85% H₃PO₄): d 11.05

(s, J_Pt–P= 2369 Hz). IR (KBr disk, n/cm^-1): 2097 (m) n(C C).

Positive-ion FAB-MS: m/z: 2546 [M + 1]⁺. Elemental analysis

calcd (%) for 8: C 50.98, H 6.10; found: C 50.98, H 6.04.

1

J = 8.6 Hz; –C₆H₄–).¹³C{ H} (126 MHz, CDCl₃, 298 K, relative

[{(C C)-1-C₆H₃{(C₆H₄C C)-2-oxa-(C₆H₅)-5-(PEt₃)₂PtC

C}₂-3,5}₂] (9). The procedure was similar to that

to Me₄Si): d 8.37, 8.41 (–CH₃), 16.39, 16.45 (t, J_C-P= 17.5 Hz;

–CH₂P), 21.30 (–C₆H₄CH₃), 89.22, 90.20 (–C C–), 109.52 (Pt–

for

8

except

that

trans-[{(C₆H₄C C)-2-oxa-(C₆H₅)-

C

C–C), 119.21 (Pt–C C–C), 120.12, 123.57, 125.83, 126.56,

5}(PEt₃)₂PtCl] (0.26 g, 0.35 mmol) was used instead of trans-

[(MeOC₆H₄C C)(PEt₃)₂PtCl]. Subsequent recrystallization of

the crude product from dichloromethane–methanol afforded 9 as

a yellow solid. Yield: 0.14 g (67%). ¹H NMR (400 MHz, CDCl₃,

298 K, relative to Me₄Si): d 1.21–1.29 (vq, 72H, J = 8.0 Hz;

–CH₃), 2.17–2.21 (m, 48H; –CH₂P), 7.20 (s, 6H; –C₆H₃–), 7.39 (d,

8H, J = 8.3 Hz; –C₆H₄–), 7.52–7.55 (m, 12H; –C₆H₅), 7.99 (d, 8H;

128.68, 129.15, 130.70, 130.80, 131.30, 133.24, 134.75 (aromatic

1

C’s), 163.40, 164.54 (C in oxa ring). ³¹P{ H} NMR (162 MHz,

CDCl₃, 298 K, relative to 85% H₃PO₄): d 11.12 (s, J_Pt–P= 2372 Hz),

11.47 (s, J_Pt–P= 2348 Hz). IR (KBr disk, n/cm^-1): 2097 (s) n(C C).

Positive-ion FAB-MS: m/z: 4012 [M]⁺. Elemental analysis calcd

(%) for 11: C 54.59, H 6.01, N 0.70; found: C 54.30, H 5.87, N

0.93.

J = 8.3 Hz; –C₆H₄–), 8.12–8.15 (m, 8H; –C₆H₄–). ¹³C{ H} (126

1

MHz, CDCl₃, 298 K, relative to Me₄Si): d 8.39 (–CH₃), 16.47 (t,

J = 17.5 Hz; –CH₂P), 108.45, 108.75 (–C C–), 109.68, 109.87

(Pt–C C–C), 119.98 (Pt–C C–C), 121.20, 124.12, 126.64,

126.89, 128.75, 129.06, 131.35, 131.59, 134.36 (aromatic C’s),

[{(C₆H₄C C)(PEt₃)₂PtC C}-1-C₆H₃{(MeOC₆H₄C C)-

(PEt₃)₂PtC CC₆H₄C C}₂- 3,5}₂-oxa-2,5] (12). The procedure

was similar to that for 11 except that 4 (0.13 g, 0.09 mmol) was used

instead of 3. Subsequent recrystallization of the crude product

from dichloromethane–methanol afforded 12 as a yellow solid.

Yield: 0.08 g (65%). ¹H NMR (400 MHz, CDCl₃, 298 K, relative

to Me₄Si): d 1.19–1.28 (vq, J = 8.0 Hz, 108H; –CH₃), 2.15–2.22

(m, 72H; –CH₂P), 3.78 (s, 12H, –C₆H₄OCH₃), 6.77 (d, 8H, J =

8.9 Hz; –C₆H₄–), 7.21 (d, 8H, J = 8.7 Hz; –C₆H₄–), 7.23 (d, 8H,

164.30, 164.86 (C in oxa ring). ^31P{ H} NMR (162 MHz, CDCl₃,

1

298 K, relative to 85% H₃PO₄): d 11.32 (s, J_Pt–P= 2354 Hz). IR

(KBr disk, n/cm^-1): 2099 (m) n(C C). Positive-ion FAB-MS:

m/z: 3002 [M + 1]⁺. Elemental analysis calcd (%) for 9·CH₃OH:

C 54.25, H 5.52, N 3.69; found: C 54.29, H 5.59, N 3.78.

10676 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

J = 8.4 Hz; –C₆H₄–), 7.33 (d, 4H, J = 1.4 Hz; –C₆H₃–), 7.36 (d,

8H, J = 8.4 Hz; –C₆H₄–), 7.39 (d, 4H, J = 8.6 Hz; –C₆H₄–), 7.44

(t, 2H, J = 1.4 Hz; –C₆H₃–), 7.97 (d, 4H, J = 8.4 Hz; –C₆H₄–).

10 was synthesized via a homocoupling reaction, in which two

equivalents of complex 3 were heated to reﬂux in dry pyridine

in the presence of Cu(OAc)₂as the catalyst. Both methods gave

the desired products. However, the former method involving the

use of {(C C)-1-C₆H₃(HC C)₂-3,5}₂as the starting material

is found to give higher yields than that for homocoupling as

there might be some loss of products during puriﬁcation in

the latter method. Therefore, {(C C)-1-C₆H₃(HC C)₂-3,5}₂has

been used as a building block for the synthesis of tetranuclear

complexes. Hexanuclear complexes 11 and 12 were obtained

through similar dehydrohalogenation method by reacting the

respective complexes 3 and 4 with [{Cl(PEt₃)₂C CC₆H₄}₂-oxa-

2,5] in the presence of copper iodide as the catalyst in relatively

good yields. The preparative routes for the tetra- and hexanuclear

platinum(II) complexes are shown in Chart 2.

1

³¹P{ H} NMR (162 MHz, CDCl₃, 298 K, relative to 85% H₃PO₄):

d 11.08 (s, J_Pt–P= 2372 Hz), 11.48 (s, J_Pt–P= 2371 Hz). IR (KBr

disk, n/cm^-1): 2097 (s) n(C C). Positive-ion FAB-MS: m/z: 4077

[M + 1]⁺. Elemental analysis calcd (%) for 12: C 53.63, H 5.89, N

0.69; found: C 54.00, H 6.00, N 0.69.

X-Ray crystal structure determination

A yellow crystal mounted in a glass capillary was used for data

collection at 301 K on a Bruker Smart CCD 1000 using graphite

˚

monochromatized Mo-Ka radiation (l = 0.71073 A). Raw frame

data were integrated with SAINT program.⁴⁷Semi-empirical

absorption correction with SADABS⁴⁸was applied. The structure

was solved by direct methods employing SHELXS-97 program⁴⁹

on PC. Pt, P and many non-H atoms were located according to

the direct methods. The positions of the other non-hydrogen atoms

were found after successful reﬁnement by full-matrix least-squares

using SHELXL-97 program⁵⁰on PC. In the ﬁnal stage of least-

squares reﬁnement, all non-H atoms were reﬁned anistropically.

H atoms were generated by SHELXL-97 program.⁵⁰Convergence

((D/s)_max= 0.001, av. 0.001) for 661 variable parameters by full-

matrix least-squares reﬁnement on F²reached to R₁= 0.0476 and

wR₂= 0.1136 with a goodness-of-ﬁt of 0.892, the parameters a and

b for the weighting scheme were 0.0717 and 0. The ﬁnal difference

Fourier map showed maximum rest peaks and holes of 2.140 (near

All the complexes have been characterized by IR spectroscopy,

1

positive FAB mass spectrometry, H and ³¹P{ H} NMR spec-

troscopy, and gave satisfactory elemental analyses. The absence

of terminal C CH signals in the H NMR spectra for all the

1

complexes conﬁrms the completion of the coupling reactions and

eliminates the possibility of the existence of partially substituted

1

complexes. The ³¹P{ H} NMR spectra of complexes 1–6 and 8–10

show a singlet signal, in the range of d 11.0–14.6 ppm, indicating

the highly symmetrical nature of these complexes. Complex 7

1

shows two sets of ³¹P{ H} NMR signals at d 11.14ppm, assigned to

the phosphine ligands bound to platinum atom near the aza-crown

moiety and at d 11.33 ppm that could be attributed to those bound

to the oxadiazole moieties, with an integral ratio of 1 : 2. Similar

ﬁndings have also been observed for the hexanuclear complexes 11

-3

˚

Pt) and -0.559 eA , respectively.

1

and 12. The ³¹P{ H} NMR spectra of 11 and 12 reveal two sets of

signals at d ~ 11.10 and 11.48 ppm, with the former corresponding

to the phosphine ligands bound to the four peripheral platinum

atoms and the latter to those bound to the two interior platinum

Results and discussion

Synthesis and characterization

atoms, with a 2 : 1 integral ratio. Platinum satellites with J_Pt–P

~

Chloroplatinum(II) complex 1 was obtained by modiﬁcation of

the method for preparation of the related trinuclear platinum(II)

complexes which were reported previously.^26d,27aThe preparation

of the alkynyl complexes was accomplished by reﬂuxing an excess

of trans-[Pt(PEt₃)₂Cl₂] with the alkyne in toluene and piperidine

in the presence of a catalytic amount of CuI to reduce the

formation of undesirable oligomeric materials and to increase

the reaction rate during the transmetallation processes.⁵¹The

synthetic routes for the di- and trinuclear platinum(II) complexes

are outlined in Chart 1. By using the dinuclear chloro complex,

[(ⁱPr₃SiC C)-1-C₆H₃{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,5], which

was reported previously by our group,^26das a building block, a

class of complexes having different peripheral ligands has been

readily synthesized. Since the dinuclear platinum(II) complexes are

found to be stable in bases, incorporation of different aryl alkynyl

groups at the periphery has been carried out before deprotection

of the triisopropylsilyl group. Using complex 5 as the building

block, trinuclear complexes 6 and 7 were obtained in reasonable

yields by reacting with different mono-platinum complexes.

Apart from these dinuclear and trinuclear platinum(II) com-

plexes, tetranuclear complexes have been prepared using two

different approaches (Chart 2). With {(C C)-1-C₆H₃-(HC C)₂-

3,5}₂as the organic core and different mono-platinum(II) com-

plexes as the starting materials, complexes 8 and 9 were synthesized

by copper(I)-catalyzed dehydrohalogenation reactions. Complex

2360 Hz have been observed, which are characteristic of a trans-

P–Pt–P conﬁguration.⁵¹

The IR spectra of these multinuclear branched complexes show

stretches in the alkynyl region. All of these complexes show a

stretch at ca. 2097 cm^-1, which is assigned as the n(C C) stretch

of the alkynyl group directly attached to the platinum centre. The

higher frequency bands observed at ca. 2200 cm^-1in the spectra of

complexes 3–5 are ascribed to the n(C C) stretch of the alkynyl

groups in between the two phenyl rings.⁵²

Crystal structure determination

Single crystals of complex 9 have been obtained by layering of

n-hexane onto a concentrated dichloromethane solution of the

complex, and its structure was solved by X-ray crystallography.

The crystal structure determination data are summarized in Table

1, while selected bond distances and angles are tabulated in

Table 2. The molecule lies about a crystallographic inversion

centre with one half molecular formula in the asymmetric unit.

The perspective drawing of complex 9 is shown in Fig. 1. The

platinum atoms in complex 9 adopt a slightly distorted trans-

square planar coordination environment with P–Pt–C bond angles

in the range of 89.4(2) and 90.7(2)^◦, which could be attributed

to a result of the coordination constraints imposed by the

triethylphosphine ligands.⁵³The Pt–P distances are in the range of

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10677

©

Table 1 Crystal and data collection parameters for complex 9

Empirical formula

Formula weight

Temperature

C₁₃₆H₁₆₂N₈O₄P₈Pt₄

3000.86

301(2) K

˚

Wavelength

0.71073 A

Crystal system

Space group

Unit cell dimensions

Monoclinic

P2₁/c

a = 90.00^◦

˚

a = 18.853(2) A

b = 21.959(2) A

b = 107.52(2)^◦

g = 90.00^◦

c = 18.266(2) A

3

˚

Volume

7211.1(13) A

Z

2

Density (calculated)

Absorption coefﬁcient

F(000)

1.382 gcm^-3

4.006 mm^-1

2996

Crystal size

q range for data collection

Index ranges

0.48 mm ¥ 0.25 mm ¥ 0.01 mm

2.08 to 25.68^◦

-22 £ h £ 22, -26 £ k £ 26, -22 £ l £ 22

42 000

Reﬂections collected

Independent reﬂections

Completeness to q = 25.68^◦

Reﬁnement method

Data/restraints^b/parameters

Goodness-of-ﬁt on F²

Final R indices [I > 2s(I)]

R indices (all data)

Largest diff. peak and hole

13636 [R_int= 0.0486]

99.6%

Full-matrix least-squares on F²

13656/90/661

0.892

R₁= 0.0476, wR₂= 0.1136^a

R₁= 0.0859, wR₂= 0.1255^a

-3

˚

2.140 and -0.559 eA

^aw = 1/[s (F_o²) + (aP)²+bP], where P is [2F_c²+ Max(F_o²,0)]/3. ^bRestraints were applied to the ethyl groups of PEt₃due to the high thermal parameters,

assuming similar P–C, C–C and 1,3-P ◊ ◊ ◊ C bond lengths or distances, respectively.

2

Fig. 1 Perspective view of complex 9 with atomic numbering scheme. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are shown at

the 30% probability level except for the carbons of the PEt₃ligands which are shown as small spheres of an arbitrary size.

˚

2.271(3)–2.294(19) A, which are similar to those observed in trans-

those found in other mono-substituted platinum(II) s-alkynyl

complexes.^26a,b,dThis could also be attributed to the stronger

trans inﬂuence of the second alkynyl ligand in the bis(alkynyl)

complexes.^26a,b,dThe C–Pt–C bond angles about the alkynyl ligand

and the platinum metal centres are in the range of 172.4(3)–

179.4(3)^◦, which are close to the ideal 180^◦for sp-hydridized

carbon bond angle and further conﬁrm the s-bonded nature of

the alkynyl groups in this tetranuclear complex. The coordination

53a

˚

[Pt(PEt₃)₂Cl₂] [2.298(18) A], trans-[Pt(PEt₃)₂Br₂] [2.315(4) A]

and trans-[Pt(PEt₂Ph)₂(C CPh)Cl] [2.283(5)–2.327(5) A]. The

53b

˚

C

C bonds adjacent to the platinum(II) atoms in 9 show bond

˚

distances in the range of 1.157(9)–1.220(8) A, which are found

to be comparable to those reported in other structurally related

platinum(II) s-alkynyl complexes.^26a,b,d,54The Pt–C distances of 9

˚

are in the range of 1.981(7)–2.015(7) A, which are longer than

10678 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

◦

˚

Table 2 Selected bond lengths [A] and bond angles [ ] for 9 with estimated

The observation of the low-energy absorption bands of complex

1 that has been red-shifted relative to N-phenylaza-15-crown-

5 and trans-[Pt(PEt₃)₂Cl₂], together with the extinction coefﬁ-

cients that are smaller than those found in trans-[Pt(PEt₃)₂Cl₂],

trans-[Pt(PEt₃)₂Cl(C CR)] and trans-[Pt(PEt₃)₂(C CR)₂], sug-

gest that the absorption bands of complex 1 at ca. 408–428 nm are

assigned as intraligand charge transfer (ILCT) transitions from

the nitrogen donor to the ethynylbenzene moiety in the ethynyl-N-

phenylaza-15-crown-5 (Fig. 2). However, given the red shift in the

absorption energies of these bands on going from N-phenylaza-

15-crown-5 to 1, an involvement of a metal-to-alkynyl metal-to-

ligand charge transfer (MLCT) transition is not unlikely. Similar

low-energy absorption bands have also been observed in other

related platinum(II) terpyridyl alkynyl⁵⁵and rhenium(I) bipyridyl

complexes^44,56that contain the amino functionalities. Thus the

lowest energy absorption bands in 1 would best be described

as a mixed MLCT [dp(Pt) → p(C CR)]/IL [p → p*(C CR)]

transitions with some mixing of an ILCT character, as a result of

the presence of the electron-donating amino group on the alkynyl

ligand.

In view of the rich vibronic structure and the very large

extinction coefﬁcients of triethynylbenzene and 1,4-bis(3,5-

diethynylphenyl)buta-1,3-diyne, the absorption bands of the

branched complexes 3–12 are likely to contain a substantial mixing

of an intraligand (IL) [p → p*(C CR)] character of the central

alkynyl core. The IL [p → p*(C CR)] absorption bands of

the peripheral ligands of these complexes might also occur at

similar energies, as related systems have also been reported to

show absorption bands in similar region.^57–59With reference to

previous spectroscopic studies on trans-[Pt(PEt₃)₂(C CR)₂],^57–59

in which the absorption bands at ca. 300–360 nm have been

assigned to contain platinum-to-alkynyl metal-to-ligand charge

transfer (MLCT) transitions, the low-energy transitions in these

branched complexes might also involve a platinum-to-alkynyl

MLCT character. The energies of the absorption tails of the

platinum(II) bis-alkynyl complexes 3–12 are found to be slightly

lower than that of the corresponding chloroplatinum(II) precursor

complexes.^26dThis is probably due to the increased electron

donation to the metal centre and the increase in the extent of p-

conjugation of the complex upon incorporation of the peripheral

alkynyl ligands, which lowers the energy of the transition. It is

worth noting that the extinction coefﬁcients of the lowest energy

absorption bands of 3–5 decrease in the order 5 > 3 > 4, which

indicates that the peripheral oxadiazole ligands may also absorb

strongly in this region. In addition, the extinction coefﬁcient of

the lowest energy absorption band (362 nm) of the tetranuclear

complex 10 is twice of that of the dinuclear complex 3 (Fig. 2),

which is in line with the increase in the number of chromophoric

units within the molecules and in accord with the involvement of

some MLCT character in these absorptions. Thus, the low-energy

transitions in complexes 2–12 are best described as an admixture

of IL [p → p*(C CR)] and MLCT [dp(Pt) → p*(C CR)]

transitions with predominantly IL character.

standard deviations (e.s.d.s.) in parentheses

˚

Selected bond lengths (A)

Pt(1)–C(1)

Pt(1)–C(13)

Pt(1)–P(1)

Pt(1)–P(2)

Pt(2)–C(10)

Pt(2)–C(29)

Pt(2)–P(3)

Pt(2)–P(4)

1.987(6)

C(1)–C(2)

1.220(8)

1.210(8)

1.198(9)

1.157(9)

1.200(9)

1.402(8)

1.403(8)

2.015(7)

2.288(2)

2.2943(19)

1.993(6)

1.981(7)

2.271(3)

2.283(2)

C(9)–C(10)

C(11)–C(12)

C(13)–C(14)

C(29)–C(30)

N(1)–N(2)

N(3)–N(4)

Selected bond angles (^◦)

C(1)–Pt(1)–C(13)

C(1)–Pt(1)–P(1)

C(13)–Pt(1)–P(2)

C(1)–Pt(1)–P(2)

C(13)–Pt(1)–P(1)

P(2)–Pt(1)–P(1)

C(2)–C(1)–Pt(1)

C(14)–C(13)–Pt(1)

C(29)–Pt(2)–C(10)

C(29)–Pt(2)–P(3)

C(10)–Pt(2)–P(3)

C(29)–Pt(2)–P(4)

C(10)–Pt(2)–P(4)

P(3)–Pt(2)–P(4)

179.4(3)

90.1(2)

89.8(2)

90.7(2)

C(9)–C(10)–Pt(2)

C(30)–C(29)–Pt(2)

C(1)–C(2)–C(3)

174.0(6)

170.8(8)

176.5(7)

173.9(7)

175.9(8)

179.4(9)

174.3(9)

106.2(6)

105.9(7)

106.1(6)

106.5(6)

101.6(6)

101.1(6)

C(10)–C(9)–C(7)

C(12)–C(11)–C(5)

C(13)–C(14)–C(15)

C(29)–C(30)–C(31)

C(38)–N(1)–N(2)

C(37)–N(2)–N(1)

C(21)–N(3)–N(4)

C(22)–N(4)–N(3)

C(37)–O(1)–C(38)

C(21)–O(2)–C(22)

89.4(2)

85.54(12)

179.1(16)

179.5(9)

172.4(3)

89.6(2)

88.2(2)

90.0(2)

91.6(2)

175.55(12)

planes of the peripheral oxadiazole ligands about the platinum

metal centres in 9 are not coplanar with the central aromatic rings,

giving interplanar angles of 6.23–48.7^◦. The out-of-plane twisting

of the coordination planes about the platinum atoms has also been

observed for other platinum s-aryl alkynyl complexes.^{26,27b,33,34a}

Electronic absorption and emission

The electronic absorption spectra of these multinuclear plat-

inum(II) alkynyl complexes have been recorded in benzene so-

lution. They exhibit intense absorption bands at ca. 300–310 and

340–428 nm, with extinction coefﬁcients in the order of 10⁴–10⁵

dm³mol^-1cm^-1. The photophysical data of complexes 1–12 are

summarized in Table 3. Fig. 2 shows the electronic absorption

spectra of complexes 1, 3 and 10 in benzene at room temperature.

Upon photo-excitation at l ≥ 365 nm, complex 1 is found

to be non-emissive while other branched complexes 2–12 dis-

play luminescence in deaerated benzene solutions at room

temperature. The emission data of these complexes are sum-

marized in Table 3. All the complexes show relatively large

Stokes shifts and lifetimes in the microsecond range, indicative

Fig. 2 Electronic absorption (left) and normalized emission spectra

(right) of complexes 1 ( ), 3 (—) and 10 ( ) in benzene at room

temperature. The absorbance of 1 has been magniﬁed by 20 times.

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10679

©

Table 3 Electronic absorption and photophysical data for complexes 1–12

b

Complex

l_abs[nm] (e [dm³mol^-1cm^-1])^a

Medium (T/K)

l_em[nm] (t_o[ms])

U_lum

c

d

1

408 sh (4260), 428 (5580)

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

C₆H₆(298)

solid (298)

solid (77)

glass (77)^e

—

d

c

2

306 (35630), 362 (98850)

362 (120410)

516 (35)

0.11

0.12

0.05

0.08

0.01

0.05

0.06

0.01

0.06

c

—

542 (0.3)

510 (504)

531 (73)

535 (0.4)

533 (90)

527 (400)

531 (79)

538 (<0.1)

540 (98)

528 (343)

529 (73)

535 (<0.1)

539 (<0.1)

526 (417)

529 (54)

530 (0.2)

539 (76)

522 (378)

528 (49)

536 (4.2)

536 (88)

524 (539)

512 (56)

3

4

300 (68310), 340 sh (115480), 364 (149270)

308 (59780), 366 (187310)

310 sh (75800), 362 (196490)

306 (82830), 366 (204310)

292 (121200), 344 (173360)

302 (82390), 350 (201090)

348 sh (211840), 362 (222640)

300 (119200), 364 (365900)

300 (148500), 364 (410200)

5

6

7

8

c

—

493 (242)

506 (426)

516 (70)

9

e

—

535 (113)

513 (292)

532 (98)

10

11

12

c

—

554 (160)

528 (404)

528 (100)

c

—

540 (66)

526 (369)

530 (78)

c

—

542 (95)

528 (340)

^aMeasured in C₆H₆at 298 K. ^bThe luminescence quantum yield, measured at room temperature using quinine sulfate in 0.5 M H₂SO₄as the reference

(excitation wavelength = 365 nm, U_lum= 0.55). ^cNon-emissive. ^dNot determined. ^eMeasured in EtOH–MeOH (4 : 1, v/v) glass.

of their triplet parentage. The complexes 2–12 show intense

yellowish green vibronically structured emission bands at room

temperature, with emission maxima at ca. 512–531 nm. Sim-

ilar vibronic structures at nearly identical wavelengths have

also been observed in the related platinum(II) complexes,

[(HC C)-1-C₆H₃{(MeOC₆H₄C C)(PEt₃)₂PtC C}₂-3,5]⁶⁰and

[(ⁱPr₃SiC C)-1-C₆H₃{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,5].^26dIn

contrast to the non-emissive behaviour of the chloro precur-

sor complex 1 at room temperature, the trinuclear complex

7 shows intense yellowish–green luminescence, with emission

wavelengths occurring at similar energies as that of 6. The

emission has been similarly assigned to originate from triplet

excited states of IL character predominantly localized on the

phenylene ring with mixing of metal character through the

interaction of platinum dp orbitals with the pp orbitals of the

alkynyl ligands. Similar assignments have previously been reported

for [{Pt(PBu₃)₂Cl}₂{C CC₆H₄C C}].^25bMoreover, the emission

3

from the IL state of the peripheral aryl–alkynyl ligands, such

as ethynyl-N-phenylaza-15-crown-5 or ethynylmethoxybenzene,

has not been observed since they are high-lying in energy. The

energy absorbed by the peripheral ligands would be transferred

to the central emitting core through directional energy trans-

fer. Similar ﬁndings have also been observed in other related

branched platinum(II) alkynyl complexes.^26b,d,27Therefore, the

3

lowest-lying emissive states are assigned to be derived from IL

states of the central emitting cores. It is believed that 1,4-bis(3,5-

diethynylphenyl)buta-1,3-diyne has a better p-conjugation than

that of triethynylbenzene. However, the emission maxima for

10680 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

Table 4 Nonlinear photophysical data for complexes 6–12 at 298 K

Complex

l_em^a/nm at l_ex= 720 nm

s₂/GM

Power dependence

6

532

531

512

517

534

530

531

52

29

6.3

71

48

191

133

1.71

1.94

1.88

1.82

2.01

1.89

1.81

7

8

9

10

11

12

^aMeasured in C₆H₆.

dinuclear complexes 3–5 (529–531 nm) are red-shifted with respect

to that observed for the tetranuclear complexes 8 and 9 (512–516

nm). One of the reasons might be the presence of some twisting in

the coordination planes of the phenyl rings within the central 1,4-

bis(3,5-diethynylphenyl)buta-1,3-diyne organic core in complexes

8 and 9. Similar ﬁnding has been observed for dinuclear complex

3 and tetranuclear complex 10, which show emission bands at

nearly identical wavelengths with similar vibronic structures (Fig.

2). Therefore, it is believed that a triplet IL [p → p*(C CR)]

state derived mainly from the central triethynylbenzene alkynyl

core is responsible for the emission for complexes 3–7 and 10–

12. The emission lifetimes in the solid state at room temperature

for complexes 2–7 are found to be considerably shorter than that

observed in dilute benzene solutions. This may be attributed to

originate from triplet–triplet annihilation or self-quenching in the

solid state.

The emission spectra of the complexes 2–12 in both deaerated

benzene solution and in 77 K glass display rich vibronic-structured

bands with vibrational progressional spacings of ca. 1150 and

2130 cm^-1, with the former corresponding to the aromatic ring

deformation and the latter to the n(C C) vibrational modes.

Additional vibrational progressional spacings of ca. 1030 cm^-1of

complexes 8, 9, 11 and 12 have been observed in low-temperature

glasses, typical of the n(C–O) stretch (Fig. 3).

Fig. 3 Emission spectra of 6 (top), 9 (middle) and 11 (bottom) in

ethanol–methanol (4 : 1, v/v) glass at 77 K. Excitation wavelength at

370 nm.

Two-photon induced luminescence (TPIL)

The multinuclear platinum(II) alkynyl complexes 6–12 are found

to emit in the yellowish–green region in benzene solutions upon

excitation with a mode-locked femtosecond Ti : Sapphire laser at

720 nm. No linear absorption in the wavelength range of 500–820

nm has been observed for these platinum(II) complexes, indicating

that the emission induced by 720 nm excitation could not be

attributed to a linear process but rather to a nonlinear process. The

emission maxima and the two-photon absorption cross-sections

s₂at 720 nm determined by TPIL study are summarized in

Table 4. The upconverted emission bands of these complexes are

almost identical to that observed in their corresponding single-

photon excited emission spectra. The TPIL spectrum of complex

9 in degassed benzene solution at room temperature is shown in

Fig. 4.

The dependence of the upconverted luminescence intensities

on the incident laser power has been measured and the power

dependence curve of complex 7 is shown in Fig. 5. The inset shows

the plot of log(emission intensity) vs. log(laser power). A straight

line plot with slope of 1.94 has been obtained. Since the 2PA has

a quadratic dependence of intensity dependence on the excitation

Fig. 4 Two-photon induced luminescence spectrum of complex 9 in

benzene at room temperature upon excitation with a mode-locked

femtosecond Ti : Sapphire laser at 720 nm.

power, theoretically, the log(emission intensity) vs. log(laser power)

should give a straight line with a slope of 2.⁶¹Therefore, the

observed quadratic dependence of the emission intensity on the

incident laser power further conﬁrms the two-photon nature of the

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10681

©

Transient absorption properties

In order to provide additional data regarding the properties of the

triplet state of these multinuclear platinum(II) complexes produced

by photoexcitation, nanosecond transient absorption spectra have

been measured in degassed benzene solution at room temperature.

The transient absorption spectra for complexes 2, 8, 9 and 11 are

shown in Fig. 6.

All the complexes reveal a broad and moderately intense

excited state absorption with a maximum between 400–700

nm throughout the whole visible region, with strong bleaching

bands at ca. 360–400 nm. Similar ﬁndings have been observed

for other structurally related platinum(II) phosphine alkynyl

complexes.^27b,64–67The negative difference absorption bands found

at ca. 365 nm for complexes 2, 8 and 9 and 11 are due to the p,p*

(S₀→ S₁) absorption of the central core ligands and the peripheral

alkynyl moieties.^65a,d,66a

Fig. 5 Power dependence of the up-converted luminescence intensity (ꢀ)

of complex 7 in benzene at room temperature. The black line shows

the theoretical curve for the quadratic function. The inset shows the

log(emission intensity) (᭡) vs. log(laser power) and its linear regression

(

).

The positive bands that occur at 400–750 nm for these complexes

3

could be assigned as derived from the p,p* absorption of the

triplet excited state. The transient absorption spectrum of 8 shows

an intense absorption band at l_max~ 450 nm, whose band shape

is different from that of complexes 2, 9 and 11. This absorption

process. The s₂values of these branched complexes with excitation

wavelength at 720 nm have been determined using the TPIL

method and are found to be in the range of 6–191 GM. The s₂

values of these multinuclear platinum(II) complexes are about 3–10

times greater than that for other mononuclear platinum(II) alkynyl

complexes, such as bis((4-(phenylethynyl)phenylethynyl)bis(tri-n-

butylphosphine)), which shows a s₂value of ~5–10 GM.^61,62The

larger s₂values might be attributed to the increased number of

chromophores in the branched complexes. The s₂values are also

comparable to the values reported by Cooper and Schanze on

some linear platinum(II) alkynyl complexes.¹⁹Other related trinu-

clear platinum(II) alkynyl complexes with two-photon absorption

properties have also reported previously by Yam and coworkers

with the s₂values in the range of ~13–32 GM, which are similar

to that of complexes 6 and 7.^26eThe 2PA s₂value of complex

6 has been found to be nearly twice that of the corresponding

aza-crown analogue complex 7. This might probably be due to the

differences in the quantum yields of the two complexes, suggesting

that azacrown is a slightly weaker donor group,⁶³leading to a

decrease in the s₂values of complex 7 than that of 6.

Apart from the trinuclear complexes 6 and 7, tetra- and

hexanuclear complexes 8–12 have also been synthesized in order

to study the effect of increased number of chromophores on the

s₂values. The s₂values are found to show dependence on the

central alkynyl cores or the peripheral substituents. For instance,

there is a great enhancement in 2PA s₂values upon addition of the

more electron-deﬁcient oxadiazole moieties at the periphery of 9

(71 GM) in comparison to the methoxybenzene moieties in 8 (6.3

GM). Similar ﬁndings can also be observed for the hexanuclear

complexes 11 (191 GM) and 12 (133 GM). It could be conceivable

that the oxadiazole ligand, with its larger electron-withdrawing

ability, could induce a greater dipole moment within the molecule,

leading to higher s₂values.

3

is believed to arise from the p,p* excited-state localized on the

central triethynylbenzene ligand. For complexes 2, 9 and 11, there

are two distinct absorption bands, with a weaker band at ca. 408

nm and a stronger one at 500–750 nm. Through a comparison

study between dinuclear complex 2 and multinuclear complexes

9 and 11, the absorption band at l_max625–650 nm is assigned as

3

derived from the p,p* excited-state localized on the oxadiazole-

containing ligands. The transient absorption decay lifetimes in

each case are found to be comparable to that of their emission

decay lifetimes, which support the assignment of a transient

absorption due to the triplet–triplet transition from the lowest

energy triplet excited state.^65d

Electrochemical properties

The electrochemical properties of the multinuclear platinum(II)

complexes 3–12 have been investigated in dichloromethane (0.1

M ⁿBu₄PF₆) by cyclic voltammetry and the data are summarized

in Table 5. No observable reductive wave for all the complexes

upon scanning up to -2.0 V vs. S.C.E. has been found, which

is similar to that reported in other related platinum(II) alkynyl

complexes.^{26c,d,f,g,27,31a,68}

The oxidative scans of complexes 3–7 containing (HC C)-

1-C₆H₃{C CC₆H₄C CH}₂-3,5 as the core ligand display

two to three irreversible waves at +0.92 to +1.91 V vs.

S.C.E. The ﬁrst oxidation waves of these complexes ap-

pear at +0.99 to +1.22 V, which occur at a similar po-

tential as their chloro precursor complex, [(ⁱPr₃SiC C)-1-

C₆H₃{Cl(PEt₃)₂PtC CC₆H₄C C}₂-3,5] (+1.25 V).^26dSince the

ﬁrst oxidation of RC₆H₄C CH is known to occur at ca. +1.50

to +1.70 V,⁶⁹which is more positive than that observed for these

trinuclear complexes, the oxidation waves of complexes 3–7 might

probably be attributed to the oxidation of the central platinum–

triethynylbenzene core. It is worth noting that the less positive

ﬁrst oxidative wave observed for 4 (+0.99 V) than 3 (+1.12 V)

than 5 (+1.22 V vs. S.C.E.) is in line with the electron-donating

effect of OCH₃> CH₃> C₆H₄-oxa-2,5. Therefore, the irreversible

These ﬁndings have demonstrated that the triethynylben-

zene and 1,4-bis(3,5-diethynylphenyl)buta-1,3-diyne moieties are

promising building blocks for the construction of two-photon

induced luminescent materials. They provide versatile handles for

tuning the s₂values and the emission energies by incorporation

of alkynyl ligands with different electronic properties.

10682 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

Fig. 6 Transient absorption difference spectra of 2 (top left), 8 (top right), 9 (bottom left) and 11 (bottom right) in degassed benzene solution at 298 K

following 355-nm pulsed laser excitation. The insets show the transient absorption decays.

Table 5 Electrochemical data for complexes 3–12 at 298 K^a

for these irreversible waves of complexes 8–10 (ca. +1.02 to

+1.28 V) is not favored. Thus, the ﬁrst oxidative waves are ascribed

b

Complex

Oxidation E_pa[V versus SCE]

to oxidation processes that involved substantial metal-centred

character. In contrast to complexes 4 and 8 bearing peripheral

methoxybenzene ligands, the ﬁrst oxidation wave of 8 (+1.02 V)

is more positive than that of complex 4 (+0.99 V vs. S.C.E.),

which is in line with the red shift in the absorption and emission

energies on going from 8 to 4. The second irreversible oxidative

waves for hexanuclear complexes 11 and 12 (+1.19 to +1.28 V

vs. S. C. E.) are found to occur at potentials less positive than

that observed for their chloroplatinum(II) precursor complex,

[{ClPt(PEt₃)₂C CC₆H₄}₂-oxa-2,5] (+1.40 V vs. S. C. E.). These

less positive potentials might be ascribed to oxidations with

involvement of some metal-centred character. These observations

show the presence of the mixed character of the HOMOs of this

class of platinum(II) alkynyl complexes, probably due to the pp–dp

overlap between the alkynyl ligands and the platinum(II) centre.^29a

[ⁱPr₃SiC C}-1-C₆H₃{Cl(PEt₃)₂-

+1.25, +1.59, +1.87

PtC CC₆H₄C C}₂-3,5]^26d

3

+1.12, +1.65

+0.99, +1.46, +1.63

+1.22, +1.68

+1.19, +1.70, +1.91

+0.52,^c+1.18, +1.69, + 1.91

+1.02, +1.43, +1.86

+1.28

+1.11, +1.65

+1.10, +1.19, +1.62

+0.99, +1.28, +1.59

4

5

6

7

8

9

10

11

12

^aIn dichloromethane (0.1 M ⁿBu₄NPF₆); working electrode, glassy carbon;

scan rate = 100 mV s^-1. ^b

E_pais the peak anodic potential for the irreversible

oxidation waves. ^cReversible couple. E_1/2= (E_pa+ E_pc)/2; E_paand E_pcare

the peak anodic and peak cathodic potentials, respectively.

Conclusion

oxidation waves of these complexes could best be described as

ligand-centred oxidation with some mixing of a metal-centred

character. The oxidation waves of complexes 6 and 7 are found to

occur at similar potentials, except thatareversible wave at ca. +0.52

V vs. S.C.E. is observed for complex 7. With the reference to studies

related to the oxidation of organic N-phenyl-aza-15-crown-5^70a

and aza-crown-containing ruthenium(II) polypyridine complex,^70b

the oxidation wave at +0.52 V, which is less positive than that

observed for the organic ligand, is assigned as the oxidation of the

amino substituent with mixing of some metal-centred character.

One to three irreversible oxidative waves at +1.02 to +1.86

V are observed for tetranuclear complexes 8–10. Since there is

no oxidative wave observed for the organic ligand {(C C)-1-

C₆H₃-(HC C)₂-3,5}₂, an assignment of ligand-centred oxidation

In summary, a series of multinuclear branched platinum(II) alkynyl

complexes with different organic core functionalities has been suc-

cessfully synthesized and characterized. The electronic absorption

spectra of these complexes are best described as an admixture

of IL [p → p*(C CR)] and MLCT [dp(Pt) → p*(C CR)]

transitions with predominantly IL character. These complexes

are found to be emissive at room temperature with rich vibronic-

structured bands in their emission spectra. These complexes are

also found to show 2PA, and their 2PA cross-sections at excitation

wavelength at 720 nm have been determined. By incorporation of

alkynyl ligands with different electronic properties, the emissions

of these complexes could be readily tuned. Through a systematic

comparison, tetra- and hexanuclear platinum(II) complexes have

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10683

©

been shown to display better 2PA and TPIL properties than their

di- and trinuclear counterparts.

molecules, 2006, 39, 2238; (b) E. Glimsdal, M. Carlsson, B. Eliasson,

B. Minaev and M. Lindgren, J. Phys. Chem. A, 2007, 111, 244; (c) P.

Lind, D. Bostro¨m, M. Carlsson, A. Eriksson, E. Glimsdal, M. Lindgren

and B. Eliasson, J. Phys. Chem. A, 2007, 111, 1598; (d) R. Westlund,

E. Glimsdal, M. Lindgren, R. Vestberg, C. Hawker, C. Lopes and E.

Malmstro¨m, J. Mater. Chem., 2008, 18, 166.

Acknowledgements

19 J. E. Rogers, J. E. Slagle, D. M. Krein, A. R. Burke, B. C. Hall, A.

Fratini, D. G. McLean, P. A. Fleitz, T. M. Cooper, M. Drobizhev, N. S.

Makarov, A. Rebane, K. Y. Kim, R. Farley and K. S. Schanze, Inorg.

Chem., 2007, 46, 6483.

20 R. D’Amato, A. Furlani, M. Colapietro, G. Portalone, M. Casalboni,

M. Falconieri and M. V. Russo, J. Organomet. Chem., 2001, 627, 13.

21 J. Staromlynska, T. J. McKay and P. Wilson, J. Appl. Phys., 2000, 88,

1726.

V.W.-W.Y. acknowledges support from The University of Hong

Kong under the Distinguished Research Achievement Award

Scheme, and the UGC Strategic Research Theme on Molec-

ular Materials. The work described in this paper has been

supported by the University Grants Committee Areas of Ex-

cellence Scheme (AoE/P-03/08) and the Special Equipment

Grant (SEG_HKU07). C.K.M.C. and C.-H.T. acknowledge the

receipt of a University Postgraduate Studentship and a University

Postdoctoral Fellowship, respectively, both from The University

of Hong Kong.

22 C. Desroches, C. Lopes, V. Kessler and S. Parola, Dalton Trans., 2003,

2085.

23 (a) K. Sonogashira, S. Takahashi and N. Hagihara, Macromolecules,

1977, 10, 879; (b) S. Takahashi, M. Kariya, T. Yakate, K. Sonogashira

and N. Hagihara, Macromolecules, 1978, 11, 1063.

24 (a) S. J. Davies, B. F. G. Johnson, M. S. Khan and J. Lewis, J. Chem.

Soc., Chem. Commun., 1991, 187; (b) B. F. G. Johnson, A. K. Kakkar,

M. S. Khan, J. Lewis, A. E. Dray, R. H. Friend and F. Wittmann, J.

Mater. Chem., 1991, 1, 485.

References

25 (a) M. S. Khan, A. K. Kakkar, N. J. Long, J. Lewis, P. R. Raithby,

P. Nguyen, T. B. Marder, F. Wittmann and R. H. Friend, J. Mater.

Chem., 1994, 4, 1227; (b) D. Beljonne, H. F. Wittmann, A. Ko¨hler, S.

Graham, M. Younus, J. Lewis, P. R. Raithby, M. S. Khan, R. H. Friend

and J. L. Bre´das, J. Chem. Phys., 1996, 105, 3868; (c) N. Chawdhury,

A. Ko¨hler, R. H. Friend, M. Younus, N. J. Long, P. R. Raithby and J.

Lewis, Macromolecules, 1998, 31, 722; (d) N. Chawdhury, A. Ko¨hler,

R. H. Friend, W. Y. Wong, J. Lewis, M. Younus, P. R. Raithby, T. C.

Corcoran, M. R. A. Al-Mandhary and M. S. Khan, J. Chem. Phys.,

1999, 110, 4963.

26 (a) V. W. W. Yam, L. Zhang, C. H. Tao, K. M. C. Wong and K. K.

Cheung, J. Chem. Soc., Dalton Trans., 2001, 1111; (b) V. W. W. Yam, C.

H. Tao, L. Zhang, K. M. C. Wong and K. K. Cheung, Organometallics,

2001, 20, 453; (c) C. H. Tao, K. M. C. Wong, N. Zhu and V. W. W. Yam,

New J. Chem., 2003, 27, 150; (d) C. H. Tao, N. Zhu and V. W. W. Yam,

Chem.–Eur. J., 2005, 11, 1647; (e) C. H. Tao, H. Yang, N. Zhu, V. W.

W. Ya m a n d S. J. X u , Organometallics, 2008, 27, 5453; (f) C. H. Tao,

N. Z h u a n d V. W. W. Ya m , J. Photochem. Photobiol., A, 2009, 207, 94;

(g) C. H. Tao and V. W. W. Yam, J. Photochem. Photobiol., C, 2009, 10,

130.

1 G. R. Newkome, C. N. Mooreﬁeld and F. Vo¨gtle, Dendritic Molecules:

Concepts, Synthesis, Perspectives, VCH, Weinhelm, Germany, 1996.

2 C. Ko¨llner, B. Pugin and A. Togni, J. Am. Chem. Soc., 1998, 120, 10274.

3 N. J. Long, A. J. Martin, F. F. de Biani and P. Zanello, J. Chem. Soc.,

Dalton Trans., 1998, 2017.

4 (a) Revadoss, P. Bharathi and J. S. Moore, J. Am. Chem. Soc., 1996,

118, 9635; (b) Q. S. Hu, V. Pugh, M. Sabat and L. Pu, J. Org. Chem.,

1999, 64, 7528.

5 I. R. Whitall, M. G. Humphrey, S. Houbrechts, J. Maes, A. Persoons,

S. Schmid and D. C. R. Hockless, J. Organomet. Chem., 1997, 544, 277.

6 (a) H. Meier, B. Mu¨hling and H. Kolshorn, Eur. J. Org. Chem., 2004,

1033; (b) G. T. Crisp and T. P. Bubner, Tetrahedron, 1997, 53, 11881;

(c) A. E. Stiegman, E. Graham, K. J. Perry, L. R. Khundkar, L. T.

Cheng and J. W. Perry, J. Am. Chem. Soc., 1991, 113, 7658; (d) K.

Kondo, T. Fujitani and N. Ohnishi, J. Mater. Chem., 1997, 7, 429;

(e) C. Dehu, F. Meyers and J. L. Bre´das, J. Am. Chem. Soc., 1993, 115,

6198.

7 (a) J. J. Wolff, F. Siegler, R. Matschiner and R. Wortmann, Angew.

Chem., Int. Ed., 2000, 39, 1436; (b) D. Beljonne, W. Wenseleers, E.

Zojer, Z. Shuai, H. Vogel, S. J. K. Pond, J. W. Perry, S. R. Marder and J.

L. Bre´das, Adv. Funct. Mater., 2002, 12, 631; (c) B. Traber, J. J. Wolff, F.

Rominger, T. Oeser, R. Gleiter, M. Goebel and R. Wortmann, Chem.–

Eur. J., 2004, 10, 1227; (d) G. Hennrich, I. Asselberghs, K. Clays and

A. Persoons, J. Org. Chem., 2004, 69, 5077.

27 (a) C. K. M. Chan, C. H. Tao, H. L. Tam, N. Zhu, V. W. W. Yam and

K. W. Cheah, Inorg. Chem., 2009, 48, 2855; (b) C. K. M. Chan, C. H.

Tao, K. F. Li, K. M. C. Wong, N. Zhu, K. W. Cheah and V. W. W. Yam,

J. Organomet. Chem., 2011, 696, 1163.

28 (a) Y. Liu, S. Jiang, K. Glusac, D. H. Powell, D. F. Anderson and K.

S. Schanze, J. Am. Chem. Soc., 2002, 124, 12412; (b) K. Glusac, M. E.

Ko¨se, H. Jiang and K. S. Schanze, J. Phys. Chem. B, 2007, 111, 929;

(c) E. C. Silverman, T. Cardolaccia, X. Zhao, K. Y. Kim, K. Haskins-

Glusac and K. S. Schanze, Coord. Chem. Rev., 2005, 249, 1491.

29 (a) J. Stahl, J. C. Bohling, E. B. Bauer, T. B. Peters, W. Mohr, J. M.

Mart´ın-Alvarez, F. Hampel and J. A. Gladysz, Angew. Chem., Int. Ed.,

2002, 41, 1871; (b) F. Zhuravlev and J. A. Gladysz, Chem.–Eur. J., 2004,

10, 6510; (c) Q. Zheng, J. C. Bohling, T. B. Peters, A. C. Frisch, F.

Hampel and J. A. Gladysz, Chem.–Eur. J., 2006, 12, 6486.

30 (a) J. E. Rogers, T. M. Cooper, P. A. Fleitz, D. J. Glass and D. G.

McLean, J. Phys. Chem. A, 2002, 106, 10108; (b) J. E. Rogers, B. C.

Hall, D. C. Hufnagle, J. E. Slagle, A. P. Ault, D. G. McLean, P. A.

Fleitz and T. M. Cooper, J. Chem. Phys., 2005, 122, 214708; (c) G.

Ramakirshna, T. Goodson III, J. E. Rogers-Haley, T. M. Cooper, D. G.

McLean and A. Urbas, J. Phys. Chem. C, 2009, 113, 1060.

31 (a) W. Y. Wong, G. L. Lu, K. H. Choi and J. X. Shi, Macromolecules,

2002, 35, 3506; (b) G. J. Zhou, W. Y. Wong, Z. Lin and C. Ye, Angew.

Chem., Int. Ed., 2006, 45, 6189; (c) W. Y. Wong, Dalton Trans., 2007,

4495.

32 T. B. Marder, G. Lesley, Z. Yuan, H. B. Fyfe, P. Chow, G. Stringer,

I. R. Jobe, N. J. Taylor, I. D. Williams and S. K. Kurtz, in Materials

for Nonlinear Optics: Chemical Perspectives, ACS Symposium Series

455, ed. G. D. Stucky, S. R. Marder and J. Sohn, American Chemical

Society, Washington, DC, 1991, p. 605.

33 (a) N. Ohshiro, F. Takei, K. Onitsuka and S. Takahashi, Chem. Lett.,

1996, 871; (b) N. Ohshiro, F. Takei, K. Onitsuka and S. Takahashi, J.

Organomet. Chem., 1998, 569, 195; (c) O. Kiyotaka, F. Masanori, K.

8 (a) S. R. Marder, Chem. Commun., 2006, 131; (b) H. J. Lee, J. Sohn, J.

Hwang, S. Y. Park, H. Choi and M. Cha, Chem. Mater., 2004, 16, 456.

9 Q. Zheng, G. S. He and P. N. Prasad, Chem. Mater., 2005, 17, 6004.

10 B. R. Cho, K. H. Son, S. H. Lee, Y. S. Song, Y. K. Lee, S. J. Jeon, J. H.

Choi, H. Lee and M. Cho, J. Am. Chem. Soc., 2001, 123, 10039.

11 S. I. Kato, T. Matsumoto, M. Shigeiwa, H. Gorohmaru, M. Shuuichi,

T. Ishii and S. Mataka, Chem.–Eur. J., 2006, 12, 2303.

12 G. S. He, L. S. Tan, Q. Zheng and P. N. Prasad, Chem. Rev., 2008, 108,

1245 and references therein.

13 (a) M. L. H. Green, S. R. Marder, M. E. Thompson, J. A. Bandy, D.

Bloor, P. V. Kolinsky and R. J. Jones, Nature, 1987, 330, 360; (b) M. L.

H. Green, J. Qin, D. O’Hare, H. E. Bunting, M. E. Thompson, S. R.

Marder and K. Chatakondu, Pure Appl. Chem., 1989, 61, 817; (c) J. A.

Bandy, H. E. Bunting, M. H. Garcia, M. L. H. Green, S. R. Marder,

M. E. Thompson, D. Bloor, P. V. Kolinsky, R. J. Jones and J. W. Perry,

Polyhedron, 1992, 11, 1429; (d) H. E. Bunting, M. L. H. Green, S. R.

Marder, M. E. Thompson, D. Bloor, P. V. Kolinsky and R. J. Jones,

Polyhedron, 1992, 11, 1489.

14 S. Barlow and S. R. Marder, Chem. Commun., 2000, 1555.

15 S. J. Davies, B. F. G. Johnson, J. Lewis and S. Muhammad, J. Organomet.

Chem., 1991, 401, C43.

16 M. C. B. Colbert, A. J. Edwards, J. Lewis, N. J. Long, N. A. Page, D. G.

Parker and P. R. Raithby, J. Chem. Soc., Dalton Trans., 1994, 2589.

17 (a) A. M. McDonagh, M. G. Humphrey, M. Samoc and B. Luther-

Davies, Organometallics, 1999, 18, 5195; (b) C. E. Powell and M. G.

Humphrey, Coord. Chem. Rev., 2004, 248, 725.

18 (a) R. Vestberg, R. Westlund, A. Eriksson, C. Lopes, M. Carlsson,

B. Eliasson, E. Glimsdal, M. Lindgren and E. Malmstro¨m, Macro-

10684 | Dalton Trans., 2011, 40, 10670–10685

This journal is

The Royal Society of Chemistry 2011

©

Hotaka, O. Nobuaki, T. Fumie and T. Shigetoshi, Chem.–Eur. J., 2004,

10, 6433.

34 (a) S. Leininger, P. J. Stang and S. Huang, Organometallics, 1998, 17,

3981; (b) B. Olenyuk, J. A. Whiteford, A. Fechtenko¨tter and P. J. Stang,

Nature, 1999, 398, 796.

35 (a) F. Guo, W. Sun, Y. Liu and K. S. Schanze, Inorg. Chem., 2005, 44,

4055; (b) F. Guo and W. Sun, J. Phys. Chem. B, 2006, 110, 15029; (c) P.

Shao, Y. Li and W. Sun, J. Phys. Chem. A, 2008, 112, 1172.

36 (a) V. W. W. Yam, K. M. C. Wong, S. H. F. Chong, V. C. Y. Lau, S. C.

F. Lam, L. Zhang and K. K. Cheung, J. Organomet. Chem., 2003, 670,

205; (b) S. H. F. Chong, S. C. F. Lam, V. W. W. Yam, N. Zhu and K. K.

Cheung, Organometallics, 2004, 23, 4924.

37 W. S. Tang, X. X. Lu, K. M. C. Wong and V. W. W. Yam, J. Mater.

Chem., 2005, 15, 2714.

38 E. Weber, M. Hedur, E. Koepp, W. Orlia and M. Czugler, J. Chem.

Soc., Perkin Trans. 2, 1988, 1251.

39 S. Chen, X. Xu, Y. Liu, W. Qiu, G. Yu, X. Sun, H. Zhang, T. Qi, K. Lu,

X. Gao, Y. Liu and D. Zhu, J. Mater. Chem., 2007, 17, 3788.

40 J. G. Rodr´ıguez, J. Esquivias, A. Lafuente and C. D´ıaz, J. Org. Chem.,

2003, 68, 8120.

and A. J. P. White, Organometallics, 2006, 25, 2525; (d) N. M. Shavaleev,

H. Adams, J. Best and J. A. Weinstein, J. Organomet. Chem., 2007, 692,

921.

55 (a) K. M. C. Wong, W. S. Tang, B. W. K. Chu, N. Zhu and V. W. W.

Yam, Organometallics, 2004, 23, 3459; (b) W. S. Tang, X. X. Lu, K. M.

C. Wong and V. W. W. Yam, J. Mater. Chem., 2005, 15, 2714; (c) K.

M. C. Wong, W. S. Tang, X. X. Lu, N. Zhu and V. W. W. Yam, Inorg.

Chem., 2005, 44, 1492; (d) Q. Z. Yang, Q. X. Tong, L. Z. Wu, Z. X. Wu,

L. P. Zhang and C. H. Tung, J. Inorg. Chem., 2004, 1948.

56 D. B. MacQueen and K. S. Schanze, J. Am. Chem. Soc., 1991, 113,

6108.

57 H. Masai, K. Sonogashira and N. Hagihara, Bull. Chem. Soc. Jpn.,

1971, 44, 2226.

58 L. Sacksteder, E. Baralt, B. A. DeGraff, C. M. Lukehart and J. N.

Demas, Inorg. Chem., 1991, 30, 2468.

59 (a) C. L. Choi, Y. F. Cheng, C. Yip, D. L. Phillips and V. W. W. Yam,

Organometallics, 2000, 19, 3192; (b) W. M. Kwok, D. L. Phillips, P. K.

Y. Yeung and V. W. W. Yam, Chem. Phys. Lett., 1996, 262, 699; (c) W.

M. Kwok, D. L. Phillips, P. K. Y. Yeung and V. W. W. Yam, J. Phys.

Chem. A, 1997, 101, 9286.

41 J. N. Demas and G. A. Crosby, J. Phys. Chem., 1971, 75, 991.

42 (a) C. Xu and W. W. Webb, Multiphoton Excitation of Molecular Flu-

orophores and Nonlinear Laser Microscopy in Topics in Fluorescence

Spectroscopy, ed. Joseph R. Lakowicz, Plenum Press, New York, 1997,

vol. 5, ch. 11, pp. 471–537; (b) C. X u a n d W. W. We bb , J. Opt. Soc. Am.

B, 1996, 13, 481; (c) M. A. Albota, C. Xu and W. W. Webb, Appl. Opt.,

1998, 37, 7352.

60 K. Onitsuka, M. Fujimoto, H. Kitajima, N. Ohshiro, F. Takei and S.

Takahashi, Chem.–Eur. J., 2004, 10, 6433.

61 (a) E. Glimdsal, M. Carlsson, B. Eliasson, B. Minaev and M. Lindgren,

J. Phys. Chem. A, 2007, 111, 244; (b) R. Westlund, E. Glimdsal, M.

Lindgren, R. Vestberg, C. Hawker, C. Lopes and E. Malmstro¨m, J.

Mater. Chem., 2008, 18, 166; (c) E. Glimsdal, M. Carlsson, T. Kindahl,

M. Lindgren, C. Lopes and B. Eliasson, J. Phys. Chem. A, 2010, 114,

3431.

43 R. R. Gagne, C. A. Koval and G. C. Lisensky, Inorg. Chem., 1980, 19,

2854.

62 T. J. McKay, J. Staromlynska, P. Wilson and J. R. Davy, J. Appl. Phys.,

44 J. D. Lewis and J. N. Moore, Dalton Trans., 2004, 1376.

45 V. W. W. Yam, K. M. C. Wong and N. Zhu, Angew. Chem., Int. Ed.,

2003, 42, 1400.

1999, 85, 1337.

63 S. J. K. Pond, O. Tsutsumi, M. Rumi, O. Kwon, E. Zojer, J.-L. Bre´das,

S. R. Marder and J. W. Perry, J. Am. Chem. Soc., 2004, 126, 9291.

64 (a) I. E. Pomestchenko, C. R. Luman, M. Hissler, R. Ziessel and F.

N. Castellano, Inorg. Chem., 2003, 42, 1394; (b) E. O. Danilov, I. E.

Pomestchenko, S. Kinayyigit, P. L. Gentili, M. Hissler, R. Ziessel and

F. N. Castellano, J. Phys. Chem. A, 2005, 109, 2465.

46 (a) T. B. Peters, J. C. Bohling, A. M. Arif and J. A. Gladysz,

Organometallics, 1999, 18, 3261; (b) Mohr, J. Stahl, F. Hampel and

J. A. Gladysz, Chem.–Eur. J., 2003, 9, 3324; (c) Q. Zheng, J. C. Bohling,

T. B. Peters, A. C. Frisch, F. Hampel and J. A. Gladysz, Chem.–Eur. J.,

2006, 12, 6486.

65 (a) K. Haskins-Glusac, I. Ghiviriga, K. A. Abboud and K. S. Schanze,

J. Phys. Chem. B, 2004, 108, 4969; (b) K. S. Schanze, E. E. Silverman

and X. Zhao, J. Phys. Chem. B, 2005, 109, 18451; (c) R. T. Farley, Q.

Zheng, J. A. Gladysz and K. S. Schanze, Inorg. Chem., 2008, 47, 2955;

(d) K. Y. Kim, A. H. Shelton, M. Drobizhev, N. Makarov, A. Rebane

and K. S. Schanze, J. Phys. Chem. A, 2010, 114, 7003.

66 (a) T. M. Cooper, D. M. Krein, A. R. Burke, D. G. McLean, J. E. Rogers

and J. E. Slagle, J. Phys. Chem. A, 2006, 110, 13370; (b) J. E. Haley, D.

M. Krein, J. L. Monahan, A. R. Burke, D. G. McLean, J. E. Slagle, A.

Fratini and T. M. Cooper, J. Phys. Chem. A, 2011, 115, 265.

67 S. M. Aly, C.-L. Ho, W.-Y. Wong, D. Fortin and P. D. Harvey,

Macromolecules, 2009, 42, 6902.

47 SAINT+SAX area detector integration program, Version 7.34A, Bruker

AXS Inc., Madison, WI,2006.

48 G. M. Sheldrick, SADABS, Program for area detector adsorption

correction, Institute for Inorganic Chemistry, University of Go¨ttingen,

Germany, 1996.

49 G. M. Sheldrick, SHELXS-97, Program for solution of crystal struc-

tures, University of Go¨ttingen, Germany, 1997.

50 G. M. Sheldrick, SHELXL-97, Program for reﬁnement of crystal

structures, University of Go¨ttingen, Germany, 1997.

51 A. Sebald, C. Stader, B. Wrackmeyer and W. Bensch, J. Organomet.

Chem., 1986, 311, 233.

52 O. Lavastre, L. Ollivier, P. H. Dixneuf and S. Sibandhit, Tetrahedron,

1996, 52, 5495.

53 (a) G. G. Messmer and E. L. Amma, Inorg. Chem., 1966, 5, 1775; (b) C.

J. Cardin, D. J. Cardin, M. F. Lappert and K. W. Muir, J. Chem. Soc.,

Dalton Trans., 1978, 46.

54 (a) M. I. Bruce, K. Constuas, J. F. Halet, B. C. Hall, P. J. Low, B.

K. Nicholson, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton

Trans., 2002, 383; (b) R. Saha, Md. A. Qaium, D. Debnath, M. Younus,

N. Chawdhury, N. Sultana, G. Kociok-Ko¨hn, L. L. Ooi, P. R. Raithby

and M. Kijima, Dalton Trans., 2005, 2760; (c) N. J. Long, C. K. Wong

68 M. Younus, A. Ko¨hler, S. Cron, N. Chawdhury, M. R. A. Al-Mandhary,

M. S. Khan, J. Lewis, N. J. Long, R. H. Friend and P. R. Raithby, Angew.

Chem., Int. Ed., 1998, 37, 3036.

69 A. J. Savall, The electrochemistry of Arenes, Styrenes and Arylalkynes,

in Rodd’s Chemistry of Carbon Compounds, Vol. 5 (Topical Volumes;

Organic Electrochemistry), ed. M. Sainsbury, Elsevier, Amsterdam,

2nd edn 2002, pp. 167–224.

70 (a) R. J. Mortimer and J. S. Weightman, J. Electroanal. Chem., 1996,

418, 1; (b) P. D. Beer, O. Kocian, R. J. Mortimer, C. Ridgway and N. R.

Stradiotto, J. Electroanal. Chem., 1996, 408, 61.

This journal is

The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 10670–10685 | 10685

©

Article Doi

Design, synthesis, characterization, luminescence and non-linear optical (NLO) properties of multinuclear platinum(ii) alkynyl complexes

DOI: 10.1039/c1dt10784d

Source and publish data:

Authors:

Article abstract of DOI:10.1039/c1dt10784d

Full text of DOI:10.1039/c1dt10784d

Products guided by the article

R&D Labs maybe for 1342795-14-5

Relevant to this article

Hot Product