Coordination self-assembly of tetranuclear Pt(ii) macrocycles with an organometallic backbone for sensing of acyclic dicarboxylic acids

Article abstract of DOI:10.1039/c2dt31828h

Coordination self-assembly of a series of tetranuclear Pt(ii) macrocycles containing an organometallic backbone incorporating ethynyl functionality is presented. The 1:1 combination of a linear acceptor 1,4-bis[trans-Pt(PEt ₃)₂(NO₃)(ethynyl)]benzene (1) with three different dipyridyl donor 'clips' (L_a-L_c) afforded three [2 + 2] self-assembled Pt^II₄ macrocycles (2a-2c) in quantitative yields, respectively [L_a = 1,3-bis(3-pyridyl) isothalamide; L_b = 1,3-bis(3-pyridyl)ethynylbenzene; L_c = 1,8-bis(4-pyridyl)ethynylanthracene]. These macrocycles were characterized by multinuclear NMR (¹H and ³¹P); ESI-MS spectroscopy and the molecular structures of 2a and 2b were established by single crystal X-ray diffraction analysis. These macrocycles (2a-2c) are fluorescent in nature. The amide functionalized macrocycle 2a is used as a receptor to check the binding affinity of aliphatic acyclic dicarboxylic acids. Such binding affinity is examined using fluorescence and UV-Vis spectroscopic methods. A solution state fluorescence study showed that macrocycle 2a selectively binds (K_SV = 1.4 × 10⁴ M^-1) maleic acid by subsequent enhancement in emission intensity. Other aliphatic dicarboxylic acids such as fumaric, succinic, adipic, mesaconic and itaconic acids caused no change in the emission spectra; thereby demonstrating its potential use as a macrocyclic receptor in distinction of maleic acid from other aliphatic dicarboxylic acids.

Full text of DOI:10.1039/c2dt31828h

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Coordination selfꢀassembly of tetranuclear Pt(II) macrocycles with organometallic
backbone for sensing of acyclic dicarboxylic acids
Sankarasekaran Shanmugaraju,a Arun Kumar Bar,a Harshal Jadhav,a Dohyun Moon,*b and
Partha Sarathi Mukherjee*a
aDepartment of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560
012, India. Fax: 91-80-2360-1552; Tel; 91-80-2293-3352
E-mail: psm@ipc.iisc.ernet.in
bPohang Accelerator Laboratory, Pohang, Kyungbook-790784, South Korea
E-mail: dmoon@postech.ac.kr
______________________________________________________________________________
Abstract
Coordination selfꢀassembly of a series of tetranuclear Pt(II) macrocycles containing
organometallic backbone incorporating ethynyl functionality is presented. The 1 : 1 combination
of a linear acceptor 1,4ꢀbis[transꢀPt(PEt3)2(NO3)(ethynyl)]benzene (1) with three different
dipyridyl donor ‘clips’ (La−Lc) afforded three [2 + 2] selfꢀassembled PtII macrocycles (2a−2c)
4
in quantitative yields, respectively [La = 1,3ꢀbis(3ꢀpyridyl)isothalamide; Lb = 1,3ꢀbis(3ꢀ
pyridyl)ethynylbenzene; Lc = 1,8ꢀbis(4ꢀpyridyl)ethynylanthracene]. These macrocycles were
characterized by multinuclear NMR (1H and 31P); ESIꢀMS spectroscopy and the molecular
structures of 2a and 2b were established by single crystal Xꢀray diffraction analysis. These
macrocycles (2a−2c) are fluorescent in nature. The amide functionalized macrocycle 2a is used
as a receptor to check the binding affinity of aliphatic acyclic dicarboxylic acids. Such binding
affinity is examined using fluorescence and UVꢀVis spectroscopic methods. Solution state
fluorescence study showed that macrocycle 2a selectively binds (KSV = 1.4 × 104 Mꢀ1) maleic

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acid by subsequent enhancement in emission intensity. Other aliphatic dicarboxylic acids such as
fumaric, succinic, adipic, mesaconic and itaconic acids caused no change in the emission spectra;
thereby demonstrates its potential use as macrocyclic receptor in distinction of maleic acid from
other aliphatic dicarboxylic acids.
______________________________________________________________________________
Introduction
Selfꢀassembly via coordination is a powerful tool to synthesize delicate supramolecular
architectures of defined shapes and sizes.1 Metalꢀligand directional bonds between two or more
predesigned molecular building units often furnish significant synthetic advantages such as fewer
steps with very high yield of the target product and easy way to control the size and shape of the
resulting supramolecular complexes.2 A large number of finite twoꢀdimensional (2D) and threeꢀ
dimensional (3D) supramolecular polygons and polyhedra have been fabricated by employing
this efficient coordinationꢀdriven selfꢀassembly.3 Among various known twoꢀdimensional
metallamacrocycles like square, rhomboid, triangle, rectangle, and polygons of higher symmetry,
first two types dominate the literature. Despite their structural simplicity, rectangles are known to
be less explored molecular polygons due to limitation of their synthesis from the readily
available cisꢀblocked 90° acceptor. To overcome this difficulty, Stang et al. and others have
established a novel way of designing rectangles by [2 + 2] selfꢀassembly of a linear 180° ditopic
building unit with a ‘clip’ type complementary building unit having bite angle of 0°.4
Furthermore, substantial efforts are being focused on incorporating suitable functional groups
into the resulting supramolecular complexes in view to fabricate functional artificial molecular
devices for potential applications in the field of optoelectronics. Among several functionality,
incorporation of unsaturated ethynyl functional group enriches the resulting assemblies to be πꢀ

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electron rich and thus makes them luminescent for sensing applications.5,6 Sensors for distinction of
isomers are of special interest since in many cases isomers have similar chemical and physical properties.
Scheme 1. [2 + 2] Selfꢀassembly of metallamacrocycles (2a−2c) using a PtII ꢀorganometallic
2
180° acceptor 1 in combination with ditopic donors (La−Lc).
Herein, we report the synthesis and characterization of a PtII − organometallic 180° acceptor
2
1,4ꢀbis[transꢀPt(PEt3)2(NO3)(ethynyl)]benzene (1) and its [2 + 2] selfꢀassembly with three
different ditopic donor “clips” (La−Lc) to afford three rectangular metallamacrocycles 2a−2c
(Schemes 1). The [2 + 2] selfꢀassembled rectangles (2a−2c) were characterized using various

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spectroscopic techniques including structure determination of 2aꢀb by single crystal Xꢀray
diffraction. Furthermore, the ability of macrocycle 2a as a receptor for dicarboxylic acids in
solution has been demonstrated using fluorescence and UVꢀVis titrations. Maleic acid and its
transꢀanalogue (fumaric acid) are geometrical isomers with different orientation of the –COOH
groups around C=C bond. Due to having amide functionality in proper fashion, macrocycle 2a
selectively recognized maleic acid by fluorescence enhancement over its isomeric fumaric acid
and other dicarboxylic acids like succinic, adipic, mesaconic and itaconic acids. This result
demonstrates a novel way of distinction of maleic acid from several other aliphatic acyclic
dicarboxylic acids.
Experimental section
Materials and methods. The binuclear PtII − acceptor 1 was synthesized under dry nitrogen
2
atmosphere using standard Schlenk technique. All the required solvents were dried and distilled
according to the standard literature procedures. 1,4ꢀdiiodobenzene, 1,3ꢀdibromobenzene,
isonicotinylchloride hydrochloride and 3ꢀaminopyridine were purchased from Aldrich (USA)
and were used as received without further purification. 1,3ꢀbis(3ꢀpyridyl)isophthalamide (La),
1,3ꢀbis(3ꢀpyridyl)ethynylbenzene (Lb) and 1,8ꢀbis(4ꢀpyridyl)ethynylanthracene (Lc) were
synthesized following the reported procedures.7 NMR spectra were recorded on a Bruker 400
1
MHz spectrometer. The chemical shifts (δ) in H NMR spectra are reported in ppm relative to
tetramethylsilane (Me4Si) as internal standard (0.0 ppm) or proton resonance resulting from
incomplete deuteration of the NMR solvents: CD3OD (3.33), CD3NO2 (4.33) and CDCl3 (7.26).
31P NMR were recorded at 121 MHz, and the chemical shifts (δ) are reported in ppm relative to
external 85% H3PO4 at 0.00 ppm. Electrospray ionization mass spectrometry (ESIꢀMS)
experiments were performed in Bruker Daltonics (Esquire 300 Plus ESI model) using standard

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spectroscopic grade solvents CH3CN or CH3OH. IR spectra were recorded on a Bruker ALPHA
FTꢀIR spectrometer. Electronic absorption spectral measurement was done using Perkin Elmer
LAMBDA 750 UV/visible spectrophotometer and fluorescence emission studies were carried out
on HORIBA JOBIN YVON Fluoromaxꢀ4 spectrometer.
Synthesis of 1,4ꢀbis[transꢀPt(PEt3)2I(ethynyl)]benzene (1a). 1,4ꢀDiethynylbenzene (200.6 mg,
1.59 mmol) and transꢀ(PEt3)2PtI2 (3.27 g, 4.77 mmol) were added to a 100 mL round bottom
Schlenk flask. 40 mL of freshly distilled toluene and 20 mL of dry diethylamine were added to
the above mixture through a glass syringe under nitrogen atmosphere. The mixture was stirred
for 15 min at room temperature before 40 mg of CuI was added in one portion. After 36 h of
stirring, the solvent was removed under vacuum and the resulting residue was purified by
column chromatography (silica gel) using hexane/dichloromethane (8:2) as eluent. Yield: 850
1
mg, 43 %. Anal. Calcd for C34H64I2P4Pt2: C, 32.91; H, 5.20. Found: C, 33.26; H, 5.49. H NMR
(CDCl3, 400 MHz): δ 7.12 (s, 4H), 2.19 (m, 24H, CH2ꢀPEt3), 1.15 (m, 36H, CH3ꢀPEt3). 31P{1H}
1
13
NMR (CDCl3, 121 MHz): δ 8.53 (s, JPtꢀP = 1737.0 Hz). C{1H} NMR (CDCl3, 100 MHz): δ
130.8 (4C, phenyl), 125.9 (2C, phenyl), 101.0 (2C, ethynyl), 30.2 (2C, ethynyl), 17.2 (12C, CH2ꢀ
PEt3), 8.7 (12C, CH3ꢀPEt3). IR (neat): υ = 2114 cmꢀ1 for ethynyl group.
Synthesis of 1,4ꢀbis[transꢀPt(PEt3)2(NO3)(ethynyl)]benzene (1). A 20 mL vial was charged
with 148.9 mg (0.12 mmol) of 1,4ꢀbis[transꢀPt(PEt3)2I(ethynyl)]benzene and 10 mL of
chloroform. To the resulting solution was added 40.8 mg (0.24 mmol) of AgNO3 in 5 mL
methanol at once. After 3 h of stirring at room temperature in dark, AgI was filtered through
celite using a glass fiber. To the concentrated filtrate (5 mL) cold diethyl ether was added to
precipitate out 1 as offꢀwhite powder. Yield: 100 mg (75 %). Anal. Calcd for C34H64N2O6P4Pt2:
1
C, 36.76; H, 5.81; N, 2.52; Found: C, 36.84; H, 5.87; N, 2.58. H NMR (CDCl3, 400 MHz): δ

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31
7.07 (s, 4H), 1.92 (m, 24H, CH2ꢀPEt3), 1.19 (m, 36H, CH3ꢀPEt3). P{1H} NMR (CDCl3, 121
MHz): δ 20.02 (s, 1JPtꢀP = 1856.86 Hz). 13C{1H} NMR (CDCl3/CD3OD, 100 MHz): δ 131.2 (4C,
phenyl), 125.8 (2C, phenyl), 104.1 (2C, ethynyl), 30.1 (2C, ethynyl), 14.8 (12C, CH2ꢀPEt3), 8.8
(12C, CH3ꢀPEt3). IR (neat): υ = 2124.7 cmꢀ1 for ethynyl group. ESIꢀMS (m/z): 1048.6 [1 −
NO3]+.
Synthesis of 2a. To a stirred suspension of ditopic donor 1,3ꢀbis(3ꢀpyridyl)isophthalamide La
(2.9 mg, 0.009 mmol) in 0.5 mL of methanol, was added a clear solution of PtII acceptor 1 (10.0
2
mg, 0.009 mmol) in chloroform (0.5 mL) dropꢀbyꢀdrop. After stirring the reaction mixture at
room temperature for 24 h in a closed 4 mL glass vial, the solution was concentrated to 0.5 mL.
The product (2a) was isolated as offꢀwhite powder upon addition of diethyl ether (~5 mL) into
the concentrated reaction mixture. Isolated yield = 86 %. Anal. Calcd for C104H156N12O16P8Pt4:
1
C, 43.70; H, 5.50; N, 5.88. Found: C, 43.87; H, 5.79; N, 5.99. H NMR (CDCl3/CD3OD, 400
MHz): δ 9.43 (s, 2H, phenylꢀH5), 8.36 (s, 4H, pyridylꢀH1), 8.17 (s, 4H, phenylꢀH6), 8.13 (d, 4H,
J = 7.6 Hz, pyridylꢀH2), 8.07 (m, 4H, pyridylꢀH3), 7.53 (m, 2H, phenylꢀH7), 7.05 (s, 8H, phenylꢀ
Ha), 6.9 (d, 4H, J = 7.2 Hz), 1.70 (br, 48H, CH2ꢀPEt3), 1.07 (br, 72H, CH3ꢀPEt3). 31P NMR
(CDCl3/CD3OD, 121 MHz): δ 15.87 (s, 1JPt ꢀP = 1742.64 Hz). IR (neat): υ(cmꢀ1) = 2124.7 (C≡C)
ꢀ 2+
ꢀ 4+
and 1675.7 (C≡O). ESIꢀMS (m/z): 1366.41 [2a − 2NO3 ] , 652.20 [2a − 4NO3 ] .
Synthesis of 2b. Complex 2b was synthesized in an analogous way as applied for 2a using Lb
instead of La and was isolated as offꢀwhite powder in 80% yield. Anal. Calcd for
1
C108H152N8O12P8Pt4: C, 46.62; H, 5.51; N, 4.03. Found: C, 46.70; H, 5.48; N, 4.10. H NMR
(CD3NO2, 400 MHz): δ 8.96 (s, 4H, pyridylꢀH1), 8.80 (br, 4H, pyridylꢀH2), 8.24 (br, 4H, pyridylꢀ
H4), 7.85 (s, 2H, phenylꢀH5), 7.77 (br, 4H, phenylꢀH6), 7.72 (d, 4H, pyridylꢀH3, J = 7.6 Hz), 7.59
(m, 2H, phenylꢀH7), 7.25ꢀ7.19 (d, 8H, phenylꢀHa), 1.94 (m, 48H, CH2ꢀPEt3), 1.23 (m, 72H, CH3ꢀ

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31
1
PEt3). P NMR (CD3NO2, 121 MHz): δ 15.96 (s, JPt ꢀP = 1719.89 Hz). IR (neat): υ(cmꢀ1) =
ꢀ 3+
2123.3 for C≡C. ESIꢀMS (m/z): 864.87 [2b − 3NO3 ] .
Synthesis of 2c. To a stirred suspension of ditopic donor 1,8ꢀbis(4ꢀpyridylethynyl)anthracene Lc
(3.4 mg, 0.009 mmol) in acetone (0.5 mL) was added a clear solution of 1 (10.0 mg, 0.009
mmol) in chloroform (0.5 mL) dropꢀbyꢀdrop with continues stirring. Initially, a clear solution
was formed, which upon further stirring at room temperature for 24 h yielded product as bright
yellow precipitate. The solid product was isolated and washed several times with cold acetone
and finally washed with diethyl ether. Isolated yield = 78 %. Anal. Calcd for
1
C124H160N8O12P8Pt4: C, 49.93; H, 5.41; N, 3.76. Found: C, 50.21; H, 5.72; N, 3.91. H NMR
(CDCl3/CD3OD, 400 MHz): δ 9.14 (s, 2H, anthraceneꢀH5), 8.87 (d, 8H, pyridylꢀHα), 8.56 (s, 2H,
anthraceneꢀH4), 8.15 (d, 4H, anthraceneꢀH3, J = 8.4 Hz), 7.99 (d, 4H, anthraceneꢀH1, J = 6.8 Hz),
7.89 (d, 8H, pyridylꢀHβ, J = 6.0 Hz), 7.53 (m, 4H, anthraceneꢀH2), 7.11ꢀ7.04 (m, 8H, phenylꢀHa),
1.80 (m, 48H, CH2ꢀPEt3), 1.14 (m, 72H, CH3ꢀPEt3).31P NMR (CD3NO2, 121 MHz): δ 15.83 (s,
ꢀ
1JPt ꢀP = 1728.60 Hz). IR (neat): υ(cmꢀ1) = 2123.3 for C≡C. ESIꢀMS (m/z): 1428.20 [2c − 2NO3
ꢀ 3+
ꢀ 4+
]2+, 931.87 [2c − 3NO3 ] , 683.13 [2c − 4NO3 ] .
Xꢀray data collection and structure refinements. The diffraction data of 1a was collected on a
Bruker SMART APEX CCD diffractometer using the SMART/SAINT software. Intensity data
were collected using graphiteꢀmonochromatic MoꢀKα radiation (0.7107 Å) at 150 K on a crystal
as obtained after several attempts. The diffraction data were obtained using SMART/SAINT
software8 and the structures were solved by direct methods using the SHELXꢀ979 incorporated in
WinGX.10 Empirical absorption corrections were applied with SADABS.11a All nonꢀhydrogen
atoms of 1a were refined with anisotropic displacement coefficients. The diffraction data of
macrocycles 2a and 2b were collected with with synchrotron radiation (2a; λ = 0.90000 Å, 2b; λ

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= 0.75000 Å) on a 2D Supramolecular Crystallography Beamline in ADSC Quantumꢀ210
detector with a silicon (111) doubleꢀcrystal monochromator at the Pohang Accelerator
Laboratory, Korea. The ADSC Quantumꢀ210 ADX program (Ver. 1.96)12 was used for data
collection and HKL2000 (Ver. 0.98.699)13 was used for cell refinement, reduction, and
absorption correction. The diffraction data were solved by direct methods using the SHELXTLꢀ
PLUS (ver 2008).13 All nonꢀhydrogen atoms were refined with anisotropic displacement
coefficients except coordinated triethylphosphine at platinum metals and amide groups at ligand
in complex 2a. The data of complex 2a is insufficient to refine the data set fully anisotropically
and therefore the structure was determined as partial structure refinement. All nonꢀhydrogen
atoms were refined with anisotropic displacement coefficients in complex 2b. Hydrogen atoms
in both complexes (2a and 2b) were assigned isotropic displacement coefficients, U(H) =
1.2U(C) or 1.5U (Cꢀmethyl), and their coordinates were allowed to ride on their respective
carbons. The leastꢀsquares refinement of the structural model was performed under geometry
constraint AFIX for phenyl groups of the complex 2a, and under geometry restraints and
displacement parameter restraints such as, DFIX, DANG, ISOR, SIMU and DELU for several
atoms around PEt3 groups residue in both the complexes. The final refinement of both complexes
were performed with the modification of the structure factors for the electron densities of the
solvents (complex 2a; 470.9 Å3, 15.4 % of the crystal volume, complex 2b; 1336.6 Å3, 20.9 % of the
crystal volume, respectively) using the SQUEEZE option of PLATON. The refinement converged for
complex 2a at a final R1 = 0.1226 and wR2 = 0.6145 for 3671 reflections with I > 2σ (I); R1 = 0.1806
and wR2 = 0.3559 for all 5972 reflections and the largest difference peak and hole were 1.542 and ꢀ1.202
e•Å3, respectively. The refinement converged for complex 2b at a final R1 = 0.0578 and wR2 = 0.1748
for 10239 reflections with I > 2σ (I); R1 = 0.0729 and wR2 = 0.1834 for all 36378 reflections and the
largest difference peak and hole were 1.889 and ꢀ2.086 e•Å3, respectively.

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Dicarboxylic acids binding study. Stock solutions (1 mM) of dicarboxylic acids such as maleic,
fumaric, succinic, malonic, mesaconic, adipic and itaconic acid (1 × 10−3 M) in CH3CN/CH3OH
(10:0.4, v/v) and that of macrocycle 2a (1.0 × 10−4 M ) in CH3CN/CH3OH (10:0.4, v/v) were
prepared. 2 mL stock solution of 2a was placed in a quartz cell of 1 cm width and dicarboxylic
acid solution was added in an incremental fashion. Their corresponding fluorescence spectra
were recorded at 298 K. Each titration was repeated at least two times to get consistent value.
For all measurements λexc = 343 nm and the emission wavelength was monitored from 360–600
nm. Both excitation and emission slit widths were 5 nm. There was no considerable change in
shape of the emission spectra except gradual enhancement of the fluorescence emission intensity
upon addition of acid solution. Analysis of the normalized fluorescence intensity (I0/I) as a
function of increasing acid concentration ([G]) was well described by the SternꢀVolmer equation
I0/I = 1 + KSV[G]. The KSV was calculated from the slope of the SternꢀVolmer plot.
Results and discussion
Synthesis and characterization of the linear acceptor 1. Since the first report of Sonagashira
et al. on coupling of terminal alkynes with aryl halides to make C−C bond using Pd(II) catalyst,
large numbers of multinuclear organometallic complexes comprising ethynyl functionality have
been synthesized.14 Here, we utilized the coupling reaction of transꢀPtI2(PEt3)2 with the terminal
alkynes as the key step to synthesize 180° acceptor 1. As shown in Scheme 2, the 1,4ꢀ
diethynylbenzene having two terminal alkynes was first reacted with 3.0 equivalents of transꢀ
PtI2(PEt3)2 to give 1,4ꢀbis[transꢀPt(PEt3)2(I)(ethynyl)]benzene (1a) and its subsequent
deiodination using 2.0 equivalents of silver nitrate (AgNO3) in chloroform/methanol mixture
under dark condition resulted in the isolation of acceptor 1 in high yield (75%).

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Scheme 2:
Schematic presentation
of the synthesis of 1,4ꢀbis[transꢀ
Pt(PEt3)2(NO3)(ethynyl)]benzene (1) from 1,4ꢀdiethynylbenzene and transꢀPtI2(PEt3)2.
The binuclear linear acceptor 1 was fully characterized by various spectroscopic techniques like
31
13
IR, multinuclear NMR {1H, P and C} and ESIꢀMS analysis. IR spectrum showed an intense
peak at υ = 2124.74 cmꢀ1 due to the ethynyl group (Fig. S1, Supporting Information). The
diplatinum acceptor 1 showed a singlet at δ = 20.02 ppm with concomitant 195Pt satellites (1JPtꢀP
1
= 1856.86 Hz) in the 31P NMR spectrum (Fig. 1). The H NMR spectrum exhibited a sharp
singlet at δ = 7.07 ppm corresponding to the phenyl protons in the aromatic region (Fig. 1). The
13C NMR spectrum of the acceptor 1 exhibited all the characteristics peaks correspond to phenyl,
ethynyl and triethylphosphene units in the expected region in the range of δ = 131.2−8.27 ppm
(Fig. S5, Supporting Information). Electrospray ionization (ESIꢀMS) mass spectrometric analysis
of the linear acceptor 1 showed (Fig. S6, Supporting Information) peak at m/z = 1048.6
ꢀ +
corresponds to the fragment [1 − NO3 ] . The experimental isotopic distribution pattern of this
fragment was consistent with its charge state (Fig. S6, Supporting Information).

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1
31
Fig. 1. H (above) and P NMR (below) spectra of the acceptor 1 recorded in CDCl3 with the
peak assignments.

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Finally the formation of linear acceptor 1 was unambiguously established by single crystal Xꢀray
diffraction analysis of the iodide analogue 1,4ꢀbis[transꢀPt(PEt3)2I(ethynyl)]benzene (1a).
Suitable single crystals of 1a were obtained by slow evaporation of a solution of 1a in
dichloromethane/nꢀhexane (1/1) mixture at ambient temperature. The diiodide complex 1a was
crystallized in monoclinic P 21/n space group with two formula units in asymmetric unit. A ball
& stick representation of the structure of 1a (Fig. 2) shows that it is indeed a 180° linear building
unit with PtꢀphenylꢀPt angle being perfectly 180.0°. The coordination geometry around each PtII
metal center is almost squareꢀplanar with I−Pt−P angles being in the range of 89.07°−91.47° and
the C−Pt−P angles being in the range of 89.15°−90.33°. The Pt−I bond distance of 2.67 Å in 1a
is very close to the reported Pt−I distances in similar complexes.15 Crystallographic data and
refinement parameters are summarized in Table S1 (Supporting Information), while the selected
bond lengths and angles are assembled in Table S2, Supporting Information.
Fig. 2. Molecular structure of the 180° PtII ꢀ diiodide complex 1a (color codes: green = Pt,
2
orange = I, magenta = P, light grey = C). Hydrogen atoms are omitted for the sake of clarity.

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Synthesis and characterization of the macrocycles 2a−2c. The PtII – based linear acceptor 1
2
was treated separately with three different ‘clip’ type ditopic donors (La−c) [La = 1,3ꢀbis(4ꢀ
pyridyl)isophthalamide; Lb = 1,3ꢀbis(3ꢀpyridyl)isophthalamide; Lc = 1,2ꢀdi(4ꢀpyridyl)ethane] in
1 : 1 molar ratio in chloroform/methanol or acetone (1 : 1) mixture (4 mL) to obtain the [2 + 2]
selfꢀassembled metallamacrocycles (2a−2c) after 24 h of stirring at room temperature (Scheme
31
1). All the three selfꢀassembled macrocycles were characterized by IR, multinuclear (1H & P)
NMR as well as by ESI mass spectrometry. Multinuclear NMR (1H, 31P) spectra of the
assemblies (2a−2c) were consistent with the formation of a single and symmetrical products
(Fig. 3 and Supporting Informations). The 31P NMR spectra of 2aꢀ2c exhibited sharp singlet
[15.87 ppm (2a), 15.96 (2b), 15.83 ppm (2c)] shifted upfield with respect to the starting platinum
building unit 1 (δ = 20.02 ppm) by 4.06 – 4.19 ppm, respectively. The upfield shifts of the
phosphorous peaks indicated the ligand to Pt electron donation due to metalꢀligand coordination.
Moreover, decrease in coupling of the flanking 195Pt satellites (ca. ꢀJ = ꢀ1742.64 Hz for 2a, ꢀJ =
ꢀ1719.89 Hz for 2b, ꢀJ = ꢀ1728.60 Hz for 2c) with respect to the starting platinum building unit
1 (1JPtꢀP = 1856.86 Hz) was consistent with the back donation from Pt(II) metal centers. In the
1H NMR spectrum of the macrocycles 2a−2c, hydrogen atoms of the pyridine rings exhibited
small downfield shift due to the loss of electron density upon coordination of pyridineꢀN atom to
platinum metal center (Fig. 3 and Supporting Informations).

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Fig. 3. 1H (top) and 31P NMR (bottom) spectra of the macrocycle 2a recorded in CDCl3ꢀCD3OD
solvents mixture with the peak assignments.
The information about the composition of the resulted [2 + 2] selfꢀassembled tetranuclear
macrocycles 2a − 2c was supported by ESIꢀMS spectrometric analysis, where multiple charged
ions correspond to the expected macrocycles were observed (Supporting Information). ESIꢀMS
experiments were performed on acetonitrile solution of the corresponding macrocycles. The

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ꢀ 2+
ꢀ 4+
multiple charged molecular ions for 2a at m/z = 1366.41 [2a − 2NO3 ] , 652.20 [2a − 4NO3 ] ;
ꢀ 3+
ꢀ 2+
for 2b at m/z = 864.87 [2b − 3NO3 ] ; for 2c at m/z = 1428.20 [2c − 2NO3 ] , 931.87 [2c −
ꢀ 3+
ꢀ 4+
3NO3 ] , 683.13 [2c − 4NO3 ] , were observed. The experimentally observed isotopic
ꢀ 2+
ꢀ 4+
ꢀ 3+
distributions of the peaks corresponding to [2a − 2NO3 ] , [2a − 4NO3 ] , [2b − 3NO3 ] and
ꢀ 2+
[2c − 2NO3 ] fragments were consistent with their charge states (Supporting Information).
Molecular structures of the macrocycles 2a−2b. The Xꢀray diffraction quality single crystals
of 2a and 2b were grown by slow vapor diffusion of diethyl ether into a
dichloromethane/methanol (1:1) solution. The diffraction data (even using synchrotron radiation)
of 2a were not of good quality due to the unstable nature of the single crystals for very fast
solvent evaporation. The crystallographic data for 2a as partial structure determination is
presented here. The gross connectivity of the building units and rectangular geometry of 2a were
established without any doubt from the obtained Xꢀray data set. Macrocycle 2a was crystallized
in triclinic Pꢀ1 space group with one formula unit in asymmetrical unit, whereas 2b crystallized
in monoclinic P 21/n space group with two formula units in asymmetrical unit. Single crystal Xꢀ
ray diffraction analysis evidenced the formation of an expected [2 + 2] selfꢀassembled PtII
4
rectangular macrocycles 2a and 2b with the dimensions of (0.9 nm × 3.0 nm) and (1.1 nm × 2.8
nm), respectively (Fig. 4). The lengths [3.0 nm (2a) and 2.8nm (2b)] and widths [0.9 nm (2a)
and 1.1 nm (2b)] of the macrocycles are measured as the distances between the centroids of the
opposite phenyl and pyridyl rings, respectively. The coordination geometry around each Ptꢀmetal
centers deviates slightly from the ideal square planar geometry due to the bulky PEt3 groups. The
PꢀPtꢀC angles range between 85º−89º (2b), while the PꢀPtꢀN angles range between 90º−94º (2b).
Although, the single crystal Xꢀray diffraction analysis confirmed the formation of rectangular

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ꢀ
geometry, we were not able to locate the –NO3 counter anions of the macrocycles due to their
high disorder, even though the data were collected at low temperature.
Fig. 4. Xꢀray crystal structures of the macrocycles 2a (top) and 2b (bottom): (color code) green =
Pt, magenta = P, blue = N, red = O, light grey = C. The hydrogen atoms are removed for the sake
of clarity.

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Unfortunately, all efforts to obtain Xꢀray diffraction quality single crystals of 2c were
unsuccessful. However, the analysis of multinuclear NMR (1H and 31P) in concurrence with ESIꢀ
MS spectroscopic studies confirmed the formation of a [2 + 2] selfꢀassembled tetranuclear
macrocycle like 2a & 2b. In view to gain further information about the size and shape of this
macrocycle, energy minimized structure of 2c was obtained using molecular mechanics universal
force field simulations (MMUFF).16 A view of the optimized geometry of 2c is depicted in Fig.
5.
Fig. 5. A view of the energy minimized structure of 2c (Color code; green = Pt, magenta = P,
blue = N, red = O, light grey = C). The hydrogen atoms are removed for the sake of clarity.
UV−vis absorption and fluorescence studies. Photophysical data of the macrocycles (2a − 2c)
are summarized in Table 1. The absorption spectra of the macrocycles 2a − 2c in CH3CN (1.0 ×
10ꢀ5 M) show peaks at λ = 261 nm, 278 nm and 344 nm (2a); λ = 282 nm, 301 nm and 346 nm
(2b); λ = 261 nm, 345 nm, 392 nm and 416 nm (2c) (Fig. 6). The peaks in the range of 301−416
nm are tentatively assigned to metal to ligand charge transfer (MLCT), whereas the peaks in the
range of 261−282 nm are ascribed to the intra/intermolecular π−π* transitions. All the three

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synthesized macrocycles show high fluorescence characteristics in CH3CN solution and their
high luminescence behavior is basically attributed to the presence of unsaturated Ptꢀethynyl
functionality and extended πꢀconjugation (Fig. 6).
Fig. 6. UVꢀvisible (left) and fluorescence (right) spectra of the macrocycles 2a − 2c recorded in
CH3CN solution (1.0 × 10ꢀ5 M) at room temperature.
Table 1. Photophysical data of the macrocycles 2a − 2c in aerated CH3CN solution.
Molar extinction
coefficient
Fluorescence
emission maxima at
298K
Absorption
maxima
Macrocycles
103 ε Mꢀ1 cmꢀ1
[λmax(nm)]
λ
max (nm)
λ
max(nm)
261, 278, 344
282, 301, 346
261, 345, 416
106 (344)
100 (346)
96 (345)
405, 424, 506 (sh)
402, 422, 507 (sh)
430, 454, 488 (sh)
2a
2b
2c

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Dicarboxylic acids binding study
The development of artificial receptors capable of signaling the presence analytes like anions,
cations and neutral molecules has attracted great interest in recent time and efforts have been
devoted in the modern supramolecular chemistry to develop various abiotic receptors.17 In
particular, the design and synthesis of suitable receptors for carboxylic acids (ꢀCOOH) and
carboxylate anions (ꢀCOOꢀ) have been studied extensively due to their vital roles in various
metabolic, biological and environmental processes.18ꢀ19 Although several synthetic receptors are
known for recognition of monocarboxylic acids, selective receptor for distinction of a diꢀ/ multiꢀ
carboxylic acid from other members of the same homologue is appealing. In this regards,
considerable interest has sparked among supramolecular chemists to find a suitable receptor for
sensing multicarboxylic acids with particular attention being paid to fluorescent chemosensors
due to its high sensitivity and fast response even at very low concentration of analytes.20
Accordingly, the newly designed molecular rectangle 2a was used as a macrocyclic
receptor to sense various aliphatic diꢀcarboxylic acids for the following reasons: a) linking of
aromatic hydrocarbons with Ptꢀethynyl functionality develops luminescence behavior; b) amideꢀ
based ‘clip’ type donor was used to make an effective receptor site which could bind with anions
through hydrogen bonding interaction; c) attachment of bulky PEt3 groups with Pt(II) centers
helps to avoid the intermolecular πꢀπ stacking and hence prevents the possible selfꢀquenching of
intrinsic fluorescence behavior. The sensing behavior of receptor 2a towards various
dicarboxylic acids was monitored using fluorescence and UVꢀVis absorption spectroscopy. The
solution state fluorescence study shows that macrocycle 2a (1.0 × 10ꢀ5 M) in CH3CN/CH3OH (10
: 0.4, v/v) doesn’t undergo any significant change in its emission spectrum upon addition of
different dicarboxylic acids such as fumaric, succinic, adipic, mesaconic and itaconic (9.0 × 10ꢀ5

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M) in CH3CN/CH3OH (10 : 0.4, v/v) (Fig. 7). Under identical condition, however, the addition
of maleic acid (9.0 × 10ꢀ5 M) to a solution of receptor 2a induced a fluorescence enhancement in
the emission intensity (Fig. 7). The obvious reason for this increase in intensity of 2a upon the
addition of maleic acid over the other tested acids is attributed to its cisꢀconfiguration, which
perfectly fits within the amide functionalized cleft.
Fig. 7. Relative changes (left) in the initial fluorescence intensity of 2a (1.0 × 10ꢀ5 M) upon
addition of different dicarboxylic acids (9.0 × 10ꢀ5 M) in CH3CN/CH3OH (10:0.4, v/v) and their
corresponding bar spectra (right).
Moreover, the gradual titration of CH3CN/CH3OH (10 : 0.4, v/v) solution of maleic acid with a
solution of 2a did not alter the shape of emission spectrum, except an enhancement in the initial
emission intensity (Fig. 8). The final fluorescence enhancement factor (FEF = IMaleic acid/I2a) was
approximately 1.6 times compared to the emission intensity of 2a. The calculated SternꢀVolmer

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binding constant from the titration profile was KSV = 1.4 ×104 Mꢀ1. Binding assay calculation
from the fluorescence titration data using the method of continuous variation (Jobs plot)
indicated 1:2 mode of binding between 2a and maleic acid (Fig. S14, Supporting Information).
Macrocycle 2a is composed of phenylꢀethynyl based fluorophore and amide based receptor. In
the electronic excited states, there may be a strong electronic coupling via electron transfer from
the acidꢀfree amide receptor to the excited state of phenylꢀethynyl based fluorophore subunit. As
a result, due to photoinduced electron transfer (PET) process, macrocycle 2a shows moderate
fluorescence emission (Fig. 8) in the acidꢀfree situation.
Fig. 8. Enhancement in the fluorescence intensity (left) of 2a (1.0 × 10ꢀ5 M) upon the gradual
addition of maleic acid (1.0 × 10ꢀ3 M) in CH3CN/CH3OH (10:0.4, v/v) solution and obtained
SternꢀVolmer plot (right).
However, the efficiency of PET process could be suppressed effectively upon binding of acid
into the amide receptor through hydrogen bonding interaction. Such a suppression of the PET
process results in an enhancement of emission intensity upon gradual addition of maleic acid
solution.1k, 18a We also performed UVꢀvis absorption study check the binding affinity of 2a

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towards maleic acid using a CH3CN/CH3OH (10 : 0.4, v/v) solution (1.0 × 10ꢀ5 M) of the
receptor 2a and maleic acid (1.0 × 10ꢀ3 M) in CH3CN/CH3OH (10 : 0.4, v/v). Gradual addition of
maleic acid in increasing concentration (0−69.7 ꢁM) causes a noticeable enhancement in initial
absorption along with a moderate redꢀshift (~4 nm) in the absorption spectra of 2a, which
indicates the existence of a strong interaction between 2a and maleic acid (Fig. 9).
Fig. 9. Absorption spectral change (left) of 2a (1.0 × 10ꢀ5 M) in CH3CN/CH3OH (10 : 0.4, v/v)
upon titration with maleic acid in CH3CN/CH3OH (10 : 0.4, v/v) (0 − 69.7 × 10ꢀ6 M) at 25°C and
corresponding BenesiꢀHilderbrand plot (right).
Moreover, the appearance of a well–defined isobestic point centered at λ = 342 nm indicates a
neat interconversion between the uncomplexed and complexed states (Fig. 9). A reciprocal plot
of changes in the initial absorption intensity of 2a upon increasing the concentration of the
maleic acid yields a linear correlation and the binding constant Ka = 1.6 × 103 Mꢀ1 was obtained
from the slope and intercept of the plot.

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Conclusions
We report here the use of a PtII ꢀorganometallic linear acceptor 1 in combination with several
2
‘clip’ type dipyridyl donors (La−Lc) to construct [2 + 2] selfꢀassembled molecular rectangles
(2a−2c) in good yields under mild condition. All these selfꢀassembled macrocycles (2a−2c) were
characterized by various spectroscopic techniques and molecular structures of the macrocycles
2a & 2b were obtained through Xꢀray diffraction analysis. Macrocycles (2a−2c) show
luminescent characteristics in solution due to the presence of Ptꢀethynyl functionality and
extended πꢀconjugation. In addition, the amide functionalized macrocycle 2a was tested as a
macrocyclic receptor for various aliphatic acyclic dicarboxylic acids and the solution state
fluorescence titration of 2a with maleic acid caused an increase in emission intensity.
Interestingly, no such perturbation in fluorescence intensity was observed when the titration was
carried out with other dicarboxylic acids (fumaric, succinic, adipic, mesaconic and itaconic).
Though, several receptors are known to recognize monoꢀ or dicarboxylic acids,18ꢀ20 receptor 2a
represents an interesting system for discrimination of maleic acid from other dicarboxylic acids.
Acknowledgement. S.S. gratefully acknowledges the CSIRꢀ New Delhi, India for the award of
research fellowship. P.S.M thanks the CSIRꢀIndia for financial support. The authors are grateful
to Johnson Matthey Pvt. Ltd. U. K. for generous supply of K2PtCl4 as loan.
Supporting Information Available: Crystallographic details of 1a and 2b; IR, NMR (1H and
31P) and ESIꢀMS spectrum of 1, 2a−2c are available. CCDCꢀ895738 and CCDCꢀ895739 contain
the supplementary crystallographic data of 1a and 2b, respectively. These data can be obtained
free
of
charge
from
the
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif.

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References
1. (a) S. Leininger, B. Olenyuk and P. J. Stang, Chem. Rev., 2000, 100, 853. (b) M. Fujita,
Chem. Soc. Rev., 1998, 27, 417. (c) F. A. Cotton, C. Lin and C. A. Murillo, Acc. Chem.
Res. 2001, 34, 759. (d) N. P. E. Barry and Therrien, B. Eur. J. Inorg. Chem. 2009, 4695.
(e) U. N. Nehete, G. Anantharaman, V. Chandrasekhar, R. Murugavel, H. W. Roesky, D.
Vidovic, J. Magull, K. Samwer and B. J. Sass, Angew. Chem. Int. Ed. 2004, 43, 3832. (f)
N. L. Toh, N. Nagarithinum and J. J. Vittal, Angew. Chem., Int. Ed. 2005, 44, 2237. (g) S.
Shanmugaraju, A. K. Bar and P. S. Mukherjee, Inorg. Chem. 2010, 49, 10235. (h) S.
Shanmugaraju, A. K. Bar and P. S. Mukherjee, Organometallics 2010, 29, 2971. (i) A.
M. Spokoyny, M. S. Rosen, P. A. Ulmann, C. Stern and C. A. Mirkin, Inorg. Chem.,
2010, 49, 1577. (j) S. Goeb, V. Prusakova, X. Wang, A. Vezinat, M. Salle and F. N.
Castellano, Chem. Commun., 2011, 47, 4397. (k) J.ꢀY. Balandier, M. Chas, S. Goeb, P. I.
Dron, D. Rondeau, A. Belyasmine, N. Gallego and M. Salle, New J. Chem., 2011, 35,
165.
2. (a) F. Fan, J. A. Whiteford, B. Olenyuk, M. D. Levin and P. J. Stang, J. Am. Chem. Soc.
1999, 121, 2741. (b) P. J. Stang, J. Fan and B. Olenyuk, J. Chem. Soc., Chem. Commun.
1997, 1453. (c) C. M. Drain and J. M. Lehn, J. Chem. Soc., Chem. Commun. 1994, 2313.
(d) A. Ikeda, H. Udzu, Z. Zhong, S. Shinkai, S. Sakamoto and K. Yamaguchi, J.
Am.Chem. Soc., 2001, 123, 3872. (e) A. Ikeda, M. Yoshimara, F. Tani, Y. Naruta and S.
Shinkai, Chem. Lett. 1998, 587. (f) A. Ikeda, M. Yoshimara, H. Udzu, C. Fukuhara and S.
Shinkai, J. Am. Chem. Soc., 1999, 121, 4296. (g) J. A. Whiteford, P. J. Stang and S. D.
Huang, Inorg. Chem., 1998, 37, 5595. (h) R. D. Schnebeck, L. Randaccio, E. Zangrando,
and P. Lippert, Angew. Chem., Int. Ed. 1998, 37, 119. (i) C. A. Schalley, A. Lutzen and

Page 25 of 32
Dalton Transactions
View Article Online
M. Albrecht, Chem.-Eur. J. 2004, 10, 1072. (k) C. H. M. Amijs, G. P. M. Van Klink and
G. Van Koten, Dalton Trans., 2006, 308. (j) M. Wang, V. Vajpayee, S. Shanmugaraju,
Y.ꢀR. Zheng, Z. Zhao, H. Kim, P. S. Mukherjee, K.ꢀW. Chi and P. J. Stang, Inorg. Chem.
2011, 50, 1506. (h) A. M. Johnson and R. J. Hooley, Inorg. Chem, 2011, 50, 4671. (i) Q.
Han, Q.ꢀJ. Li, J. He, B. Hu, H. Tan, Z. Abliz, C.ꢀH. Wang, Y. Yu and H.ꢀB. Yang, J. Org.
Chem., 2011, 76, 9660. (j) S. Goeb, S. Bivaud, P. I. Dron, J.ꢀY. Balandier, M. Chas and
M. Salle, Chem. Commun., 2012, 48, 3106. (k) S. Bivaud , J.ꢀY. Balandier , M. Chas , M.
Allain , S. Goeb and M. Sallé, J. Am. Chem. Soc., 2012, 134, 11968.
3. (a) Y. R. Zheng and P. J. Stang, J. Am. Chem. Soc., 2009, 131, 3487. (b) Y. R. Zheng, H.
B. Yang, B. H. Northrop, K. Ghosh and P. J. Stang, Inorg. Chem., 2008, 47, 4706. (c) N.
Das, A. Ghosh, O. M. Singh and P. J. Stang, Org. Lett., 2006, 8, 1701. (d) N. Das, P. J.
Stang, A. M. Arif and C. F. Campana, J. Org. Chem., 2005, 70, 10440. (e) N. Das, A.
Ghosh, A. M. Arif and P. J. Stang. Inorg. Chem., 2005, 44, 7130. (f) N. Das, A. M. Arif,
P. J. Stang, M. Sieger, B. Sarkar, W. Kaim and J. Fiedler, Inorg. Chem., 2005, 44, 5798.
(g) T. Megyes, H. Jude, T. Grósz, I. Bakó, T. Radnai, G. Tárkányi, G. Pálinkás and P. J.
Stang, J. Am. Chem. Soc., 2005, 127, 10731. (h) C. Addicott, I. Oesterling, T. Yamamoto,
K. Müllen and P. J. Stang, J. Org. Chem., 2005, 70, 797. (i) M. J. E. Resendiz, J. C.
Noveron, H. Disteldorf, S. Fischer and P. J. Stang, Org. Lett., 2004, 6, 651. (j) N. Das, P.
S. Mukherjee, A. M. Arif and P. J. Stang, J. Am. Chem. Soc., 2003, 125, 13950. (k) C. J.
Kuehl, C. L. Mayne, A. M. Arif and P. J. Stang, Org. Lett., 2000, 2, 3727. (l) R.
Chakrabarty, P. S. Mukherjee, and P. S. Stang, Chem. Rev., 2011, 111, 6810.

Dalton Transactions
Page 26 of 32
View Article Online
4. (a) C. J. Kuehl, S. D. Huang and P. J. Stang, J. Am. Chem. Soc., 2001, 123, 9634. (b) A.
K. Bar, B. Gole, S. Ghosh and P. S. Mukherjee, Dalton Trans., 2009, 6701. (c) S. Ghosh,
R. Chakrabarty and P. S. Mukherjee, Inorg. Chem., 2009, 48, 549. (d) W. Kaim, B.
Schwederski, A. Dogan, J. Fiedler, C. J. Kuehl and P. J. Stang. Inorg. Chem., 2002, 41,
4025. (e) T. Rajendran, B. Manimaran, F.ꢀY. Lee, G.ꢀH. Lee, S.ꢀM. Peng, C. M. Wang
and K.ꢀL. Lu, Inorg. Chem., 2000, 39, 2016. (f) S. Shanmugaraju, A. K. Bar, S. A. Joshi,
Y. P. Patil and P. S. Mukherjee, Organometallics 2011, 30, 1951. (g) J. Mattsson, P.
Govindaswamy, A. K. Renfrew, P. J. Dyson, P. Stepnicka, G. S. Fink and B. Therrien,
Organometallics 2009, 28, 4350. (h) B. Therrien, Eur. J. Inorg. Chem., 2009, 2445. (i)
W.ꢀG. Jia, Y.ꢀF. Han, Y.ꢀJ. Lin, L.ꢀH. Weng and G.ꢀX. Jin, Organometallics 2009, 28,
3459. (j) P. Thanksekaran, R. T. Liao, L. H. Liu, T. Rajendran, R. Rajagopal, K.ꢀ.L. Lu,
Coord. Chem. Rev., 2005, 249, 1085.
5. (a) V. W.ꢀW. Yam, C.ꢀH. Tao, L. Zhang, K. M.ꢀC. Wong and K.ꢀK. Cheung,
Organometallics 2001, 20, 453. (b) L. Sacksteder, E. Baralt, B. A. DeGraff, C. M.
Lukehart and J. N. Demas, Inorg. Chem., 1991, 30, 2468. (c) V. W.ꢀW. Yam, L. P. Chan
and T. F. Lai, Organometallics 1993, 12, 2197. (d) V. W.ꢀW. Yam, P. K. Y. Yeung, L. P.
Chan, W. M. Kwok, D. L. Phillips, K. L. Yu, R. W. K. Wong, H. Yan, Q. J. Meng,
Organometallics 1998, 17, 2590. (e) C. W. Chan, L. K. Cheng and C. M. Che, Coord.
Chem. Rev., 1994, 132, 87. (f) M. Hissler, W. B. Connick, D. K. Geiger, J. E. McGarrah,
D. Lipa, R. J. Lachicotte and R. Eisenberg, Inorg. Chem., 2000, 39, 447. (g) M. S. Khan,
A. K. Kakkar, N. J. Long, J. Lewis, P. Raithby, P. Nguyen, T. B. Marder, F. Wittmann
and R. H. Friend, J. Mater. Chem. 1994, 4, 1227. (h) N. Chawdhury, A. Kohler, R. H.
Friend, M. Younnus, N. J. Long, P. R. Raithby and J. Lewis, Macromolecules 1998, 32,

Page 27 of 32
Dalton Transactions
View Article Online
722. (i) N. Chawdhury, A. Kohler, R. H. Friend, W. Y. Wong, J. Lewis, M. Younus, P. R.
Raithby, T. C. Corcoran, M. R. A. AlꢀMandhary and M. S. Khan, J. Chem. Phys., 1999,
110, 4963. (j) V. Grosshenny, A. Harriman, M. Hissler and R. Ziessel, J. Chem. Soc.,
Faraday Trans. 1996, 92, 2223. (k) R. Ziessel, M. Hissler, A. Elꢀghayoury and A.
Harriman, Coord. Chem. Rev., 1998, 178, 1251. (l) S. Shanmugaraju, S. A. Joshi and P.
S. Mukherjee, J. Mater. Chem., 2011, 21, 9130. (m) B. Gole, S. Shanmugaraju, A. K. Bar
and P. S. Mukherjee, Chem. Commun., 2011, 10046.
6. (a) A. K. Bar, S. Shanmugaraju, K.ꢀW. Chi and P. S. Mukherjee, Dalton Trans., 2011,
40, 2257. (b) S. Shanmugaraju, S. A. Joshi and P. S. Mukherjee, Inorg. Chem., 2011, 50,
11736. (c) N. L. S. Yue, D. J. Eisler, M. C. Jennings and R. J. Puddephatt, Inorg.
Chem., 2004, 43, 7671. (d) Z. Qin, M. C. Jennings and R. J. Puddephatt, Inorg.
Chem., 2003, 42, 1956. (e) K. D. Benkstein, J. T. Hupp and C. L. Stern, Inorg.
Chem., 1998, 37, 5404. (f) K. D. Benkstein, J. T. Hupp and C. L. Stern, J. Am. Chem.
Soc., 1998, 120, 12982. (g) P. H. Dinolfo, M. E. Williams, C. L. Stern and J. T. Hupp, J.
Am. Chem. Soc., 2004, 126, 12989. (h) B. Manimaran, T. Rajendran, Y. L. Lu, G. H. Lee,
S. M. Peng ad K. ꢀL. Lu, J. Chem. Soc., Dalton Trans., 2001, 515.
7. (a) L. S. Nancy, E. J. Dana, M. C. Jennings and R. J. Puddephatt, Inorg. Chem., 2004,
43, 7671. (b) S. Ghosh and P. S. Mukherjee, P. S. Organometallics 2008, 27, 316. (c) S.
Ghosh, B. Gole, A. K. Bar and P. S. Mukherjee, Organometallics 2009, 28, 4288. (e) P.
S. Mukherjee, K. S. Min, A. M. Ariff and P. J. Stang, Inorg. Chem., 2004, 43, 6345.
8. SMART/SAINT; Bruker AXS, Inc.: Madison, WI, 2004.
9. G. M. Sheldrick, SHELXꢀ97, Program for the Solution and Refinement of Crystal
Structures; University of Gottingen: Gottingen, Germany, 1998.

Dalton Transactions
Page 28 of 32
View Article Online
10. L. J. Farrugia, WinGX: An Integrated System of Windows Programs for the Solution,
Refinement and Analysis for Single Crystal Xꢀray Diffraction Data, version 1.65.04;
Department of Chemistry: University of Glasgow, 2003. (L. J. Farrugia, J. Appl.
Crystallogr., 1999, 32, 837).
11. (a) G. M. Sheldrick, SADABS, Bruker Nonius Area Detector Scaling and Absorption
Correction, version 2.05; University of Gottingen: Gottingen, Germany, 1999. (b) A. J.
Arvai, C. Nielsen, ADSC Quantumꢀ210 ADX Program, Area Detector System
Corporation; Poway, CA, USA, 1983. (c) Z. Otwinowski, W. Minor, Methods in
Enzymology, ed. Carter, Jr., C. W.; Sweet, R. M. Academic Press, New York, 1997, 276,
307. (d) G. M. Sheldrick, SHELXTLꢀPLUS, Crystal Structure Analysis Package; Bruker
Analytical Xꢀray; Madison, WI, USA, 1997.
12. (a) L. J. Farrugia, ORTEPꢀ3 for Windows, version 1.08. J. Appl. Crystallogr., 1997, 30,
565. (b) A. L. Spek, Acta Crystallogr., 1990, A46, C34.
13. (a) Arvai, A. J.; Nielsen, C. ADSC Quantumꢀ210 ADX Program, Area Detector System
Corporation; Poway, CA, USA, 1983. (b) Otwinowski, Z.; Minor, W.; in Methods in
Enzymology, ed. Carter, Jr., C. W.; Sweet, R. M. Academic Press, New York, 1997, vol.
276, part A, pp. 307. (c) Sheldrick, G. M. SHELXTLꢀPLUS, Crystal Structure Analysis
Package; Bruker Analytical XꢀRay; Madison, WI, USA, 1997.
14. (a) H. Werner, P. Bachmann and M. Martin, Can. J. Chem., 2001, 79, 519. (b) K. D. John
and M. D. Hopkins, Chem. Commun., 1999, 589. (c) H. Werner, P. Bachmann, M.
Laubender and O. Gevert, Eur. J. Inorg. Chem., 1998, 1217. (d) W.ꢀY. Wong, C.ꢀK
Wong, G.ꢀL, Lu, A.W.ꢀM. Lee, K.ꢀW. Cheah and J.ꢀX. Shi, Macromolecules 2003, 36,
983. (e) J. R. Berenguer, M. Bernechea, J. Fornies, E. Lalinde, J. Torroba,

Page 29 of 32
Dalton Transactions
View Article Online
Organometallics 2005, 24, 431. (f) J. Vicente, M.ꢀT. Chicote, M. M. AlvarezꢀFalcon, P.
G. Jones, Organometallics 2005, 24, 2764. (g) F. Lin, H.ꢀY. Peng, Jꢀ.X. Chen, D. T. W.
Chik, Z. Cai, K. M. C. Wong, V. W. W. Yam and H. N. C. Wong, J. Am. Chem. Soc,
2010, 132, 16383. (h) P.ꢀH. Lanoe, H. Bozec, J. A. G. Williams, J.ꢀL. Fillaut and V.
Guerchais, Dalton Transactions, 2010, 39, 707. (i) M. Janka, G. K. Anderson and N. P.
Rath, Organometallics 2004, 23, 4382. (j) K. Campbell, R. McDonald, M. J. Ferguson
and R. R. Tykwinski, J. Organomet. Chem., 2003, 683, 379. (k) C. Mueller, J. A.
Whiteford and P. J. Stang, J. Am. Chem. Soc, 1998, 120, 9827. (l) R. Faust, F.
Diederich, V. Gramlich and P. Seiler, Chem. Eur. J., 1995, 1, 111. (m) F. Paul and C.
Lapinte, C. Coord. Chem. Rev., 1998, 178, 431. (n) R. Ziessel, M. Hissler, A. Elꢀ
ghayoury and A. Harriman, Coord. Chem. Rev. 1998, 178, 1251. (o) P. Nguyen, P.
GomezꢀElipe and I. Manners, Chem. Rev. 1999, 99, 1515. (p) R. Dembinski, T. Bartik, B.
Bartik, M. Jaeger and J. A. Gladysz, J. Am. Chem. Soc., 2000, 122, 810. (q) N. J. Long
and C. K. Williams, Angew. Chem., Int. Ed., 2003, 42, 2586.
15. H. Ogawa, T. Joh, S. Takahashi, Y. Yamamoto and Y. Yamazaki, Organometallics 1988,
7, 2257.
16. ArgusLab 4.0, M. A. Thompson, Planaria Software LLC, Seattle, WA.
http://www.arguslab.com.
17. (a) H. N. Kim, M. H. Lee, H. J. Kim, J. S. Kim and J. Yoon, Chem. Soc. Rev., 2008, 37,
1465. (b) Y.ꢀF. Han, H. Li G.ꢀX. Jin, Chem. Commun., 2012, 46, 6879. (c) J. Lagona, P.
Mukhapadhyay, S. Chakrabarti and L. Isaacs, Angew. Chem. Int. Ed., 2005, 44, 4844. (d)
M. D. Pluth and K. N. Raymond, Chem. Soc. Rev., 2007, 36, 161. (e) M. E. Germain and
M. J. Knapp, Chem. Soc. Rev., 2009, 38, 2543. (f) B. M. Rambo and J. L. Sessler, Chem.