Synthesis, characterization and photophysics of a new series of anionic C,N,C cyclometalated platinum complexes

Article abstract of DOI:10.1021/ic701298z

A novel series of anionic mononuclear terdentate dicyclometalated complexes (NBu₄)[Pt(C∧N∧C)X] (HC∧N∧CH = 2,6-diphenylpyridine) containing acetylide (X = C≡CR, R = ^tBu, 1; Ph, 2; Tol, 3; (4-OMe)C₆H₄, 4) or another anionic ligand (X = CN, 5; S-2Py, 6; CH₂COCH₃, 7) have been synthesized and fully characterized. The solid-state structures of complexes 1 and 4-6 have also been determined by X-ray diffraction studies, showing, in all the cases, the presence of several types of weak hydrogen interactions, leading to the generation of supramolecular 2D (1) or 3D (4-6) architectures. All the complexes (1-7) are intensely luminescent at low temperature (solid and glassy CH₂Cl ₂), exhibiting concentration dependence in the emissions of the glassy CH₂Cl₂ matrix.

Full text of DOI:10.1021/ic701298z

Inorg. Chem. 2007, 46, 9919−9930
Synthesis, Characterization and Photophysics of a New Series of
Anionic C,N,C Cyclometalated Platinum Complexes†
Jesu´s R. Berenguer, Elena Lalinde,* and Javier Torroba
Departamento de Qu´ımica, Grupo de S´ıntesis Qu´ımica de La Rioja, UAsC.S.I.C. UniVersidad de
La Rioja, 26006 Logron˜o, Spain
Received July 2, 2007
A novel series of anionic mononuclear terdentate dicyclometalated complexes (NBu4)[Pt(C∧N∧C)X] (HC∧N∧CH
2,6-diphenylpyridine) containing acetylide (X CR, R
tBu, 1; Ph, 2; Tol, 3; (4-OMe)C6H4, 4) or another
anionic ligand (X CN, 5; S-2Py, 6; CH2COCH3, 7) have been synthesized and fully characterized. The solid-
state structures of complexes 1 and 4 6 have also been determined by X-ray diffraction studies, showing, in all
the cases, the presence of several types of weak hydrogen interactions, leading to the generation of supramolecular
2D (1) or 3D (4 6) architectures. All the complexes (1 7) are intensely luminescent at low temperature (solid and
glassy CH2Cl2), exhibiting concentration dependence in the emissions of the glassy CH2Cl2 matrix.
)
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−
−
Introduction
homo- and polynuclear species incorporating phosphines as
auxiliary ligands (L). A wide range of rigid rod polymers,16-22
architectures featuring a central aromatic core,23-27 dendri-
mers,28,29 macrocycles,22,30-37 or molecular wires38-42 bearing
PtL2 entities have been reported. Furthermore, polypyridyl43-63
and related cyclometalated55,64-73 alkynyl platinum complexes
There is a considerable interest in the study of transition-
metal alkynyl σ complexes due to their widespread applica-
tion in material science.1-11 Since the first report on soluble
[Pt(PnBu3)2] containing oligomeric polymers in the 1970s,12,13
many new types of materials exhibiting very interesting
prospects for the design of new molecular-site electronic
devices have been studied and investigated.1-11,14,15 In
platinum chemistry, much research has been devoted to
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(19) Khan, M. S.; Al-Mandhary, M. R. A.; Al-Suti, M. K.; Al-Battashi, F.
R.; Al-Saadi, S.; Ahrens, B.; Bjernemose, J. K.; Mahon, M. F.; Raithby,
P. R.; Younus, M.; Chawdhury, N.; Ko¨hler, A.; Marseglia, E. A.;
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references therein.
* To whom correspondence should be addressed. E-mail: elena.lalinde@
unirioja.es.
† Dedicated to Professor Juan Fornie´s (University of Zaragoza) on the
occasion of his 60th birthday.
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10.1021/ic701298z CCC: $37.00
Published on Web 10/10/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 23, 2007 9919

Berenguer et al.
3
have also received significant attention over the past decade,
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actions.47,53-55,61 Within this area, cyclometalated derivatives
are of particular interest because of the very strong ligand
field induced by both the acetylide group and the cyclom-
etalated ligand. This fact usually raises the energy of metal-
centered (d-d) excited states, preventing access to the
deactivation of the lowest emitting excited state by radia-
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9920 Inorganic Chemistry, Vol. 46, No. 23, 2007

New Series of Anionic C,N,C Cyclometalated Pt Complexes
platinum(II) complexes containing terdentate ligands have
been extensively investigated,55,71-73,86-101 the most common
ligands used are monoanionic six-electron donors of the
“pincer” type, 2,6-(ECH2)2C6H3 (E ) NR2, PR2, SR),86-90
or conjugated donors having C-N-N-,N-C-N- or C-N-
S- donor sets.91-102 Cyclometalated Pt(II) complexes featur-
ing double deprotonated terdentate C-N-C ligands are still
rare,55,103-109 although very unusual diplatinum systems con-
taining the highly delocalized four-fold deprotonated
CNC∧CNC 12-electron bridging system (L) (H4L ) 6,6′-
diphenyl-2,2′-bipyridine) have been recently prepared by
Zucca at al.110
Figure 1.
Ar before use. NMR spectra were recorded at 293 K on Bruker
ARX 300 or ARX 400 spectrometers. Chemical shifts are reported
in ppm relative to external standards (SiMe4, CFCl3, and 85% H3-
PO4), and all coupling constants are given in hertz (Hz). The NMR
spectral assignments of the C∧N∧C ligand (HC∧N∧CH 2,6-diphen-
ylpyridine) follow the numbering scheme shown in Figure 1. IR
spectra were obtained on a Nicolet Nexus FT-IR Spectrometer,
using Nujol mulls between polyethylene sheets. Elemental analyses
were carried out with Perkin-Elmer 2400 CHNS/O or Carlo Erba
EA1110 CHNS-O microanalyzers. Mass spectra were recorded
on a HP-5989B (ES) or a Microflex MALDI-TOF Bruker (MALDI)
spectrometer operating in the linear and reflector modes using
dithranol as the matrix. Molar conductances were carried out on a
Crison GLP31 conductimeter in acetone and CH2Cl2 solutions (5
× 10-4 M). The optical absorption spectra were recorded using a
Hewlett-Packard 8453 (solution) spectrophotometer in the visible
and near-UV ranges. Emission and excitation spectra were obtained
on a Jobin-Yvon Horiba Fluorolog 3-11 Tau-3 spectrofluorimeter,
with the lifetime measured in phosphorimeter mode. Literature
methods were used to prepare the starting material [Pt(C∧N∧C)-
(dmso)] (dmso ) dimethylsulfoxide).106
Here we report the synthesis, characterization, electronic
absorption, and emissive properties of a novel series of
alkynyl dimetalated platinum complexes (NBu4)[Pt(CNC)-
t
(CtCR)] (R ) Bu, Ph, Tol, (p-OMe)C6H4) and those of
three related anionic complexes (NBu4)[Pt(CNC)X] (X )
CN, S-2Py, CH2COCH3) synthesized for comparative pur-
poses.
Experimental Section
General Comments. All reactions were carried out under an
atmosphere of dry argon, using standard Schlenk techniques.
Solvents were dried by standard procedures and distilled under dry
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Preparation of (NBu4)[Pt(C∧N∧C)(CtCtBu)] (1). [Pt(C∧N∧C)-
(dmso)] (0.25 g, 0.50 mmol) was added to a solution of LiCtCt-
Bu (3.00 mmol) (1:6 molar ratio) prepared from HCtCtBu (0.36
n
mL, 3.00 mmol) and BuLi (3.00 mmol) in diethyl ether (20 mL)
at low temperature (-40 °C), and the mixture was allowed to warm
to room temperature. After stirring for 5 h, the solvent was
evaporated and the resulting orange solid was extracted with cold
deoxygenated water (40 mL). The resulting orange solution was
rapidly filtered under Ar through celite, and the filtrate was treated
with a solution of (NBu4)Br (0.16 g, 0.50 mmol) in 5 mL of
deoxygenated water. The resulting orange solid was filtered, washed
with water, and air-dried (0.14 g, 37%). Found: C, 59.95; H, 7.89;
N, 3.87. Anal. Calcd for C39H56N2Pt‚2H2O: C, 59.75; H, 7.71; N,
3.57. MS MALDI(-): m/z (peak anion not observed) 448.8 [Pt-
(C∧N∧C) + Na]. IR (cm-1, Nujol): ν(CtC) 2091(s). H NMR
1
(CD3COCD3, δ (J, Hz)): 8.17 (d, J ) 7.0, 3J(Pt-H) ) 34.7, H10);
7.59 (t, J ) 7.6, H4); 7.43 (d, J ) 7.5, H7); 7.33 (d, J ) 7.8, 4J(Pt-
H) ) 5.0, H3); 7.08 (td, J ) 7.1, 1.3, J(Pt-H) ) 7.0, H9); 6.91
4
(td, J ) 7.5, 1.4, H8); 3.39 (m, NCH2, NBu4); 1.65 (m, -CH2-,
t
NBu4); 1.37 (s, Bu); 1.34 (m, -CH2-, NBu4); 0.92 (t, -CH3,
NBu4). 13C NMR (CDCl3, δ(J, Hz)): 174.2 (s, J(Pt-C) ) 705,
1
C5); 167.8 (s, J(Pt-C) ) 63, C2); 149.9 (s, J(Pt-C) ) 29, C6);
2
2
139.0 (s, 2J(Pt-C) ) 72, C10); 137.1 (s, C4); 130.2 (s, 3J(Pt-C) )
39, C9); 123.1 (s, J(Pt-C) ) 27, C7); 121.6 (s, C8); 115.9 (s,
3
tentatively assigned to tCâ); 113.5 (s, J(Pt-C) ) 44, C3); 91.9
3
(s, tentatively assigned to CRt); 58.6 (s, N-CH2, NBu4); 34.3 (s,
C(CH3)3); 30.1 (s, C(CH3)3); 24.3 (s, CH2, NBu4); 18.7 (s, CH2,
NBu4); 14.0 (s, CH3, NBu4). ΛM(acetone): 111 mol-1 cm2 Ω-1
Preparation of (NBu4)[Pt(C∧N∧C)(CtCPh)] (2). The proce-
dure was identical to that used for 1 with 8 equiv of LiCtCPh
(4.80 mmol) and [Pt(C∧N∧C)(dmso)] (0.30 g, 0.60 mmol) in
tetrahydrofuran (THF, 15 mL). The mixture was stirred for 30 min
.
(106) Cave, G. W. V.; Fanizzi, F. P.; Deeth, R. J.; Errington, W.; Rourke,
J. P. Organometallics 2000, 19, 1355.
(107) Newman, C. P.; Cave, G. W. V.; Wong, M.; Errington, W.; Alcock,
N. W.; Rourke, J. P. J. Chem. Soc., Dalton Trans. 2001, 2678.
(108) Lu, W.; Chan, M. C. W.; Cheung, K. K.; Che, C. M. Organometallics
2001, 20, 2477.
(110) Zucca, A.; Petretto, G. L.; Stoccoro, S.; Cinellu, M. A.; Minghetti,
G.; Manassero, M.; Manassero, C.; Male, L.; Albinati, A. Organo-
metallics 2006, 25, 2253.
(109) Kui, S. C. F.; Chui, S. S.-Y.; Che, C.-M.; Zhu, N. J. Am. Chem.
Soc. 2006, 128, 8297.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9921

Berenguer et al.
at -40 °C and then allowed to reach room temperature. The volatile
materials were removed in vacuo, and the resulting residue was
extracted with cold deoxygenated water (25 mL), filtered, and
treated with (NBu4)Br (0.194 g, 0.60 mmol), affording 2 as an
orange solid (0.21 g, 45%). Found: C, 63.99; H, 6.98; N, 3.27.
Anal. Calcd. for C41H52N2Pt: C, 64.12; H, 6.83; N, 3.27. MS
MALDI(-): m/z (peak anion not observed) 448.8 [Pt(C∧N∧C) +
Na]. IR (cm-1, Nujol): ν(CtC) 2105(sh), 2073(s). 1H NMR (CD3-
COCD3, δ (J, Hz)): 8.14 (d, J ) 6.3, 3J(Pt-H) ) 36.0, H10); 7.58
(t, J ) 8.1, H4); 7.42 (d, J ) 7.3, H7); 7.33 (m, H3 and o-H, Ph);
7.15 (t, J ) 7.5, m-H, Ph); 7.05 (td, J ) 7.0, 0.9, 4J(Pt-H) ≈ 7.1,
H9); 6.97 (t, J ) 6.7, p-H, Ph); 6.88 (td, J ) 7.2, 1.6, H8); 3.46 (m,
NCH2, NBu4); 1.71 (m, -CH2-, NBu4); 1.37 (m, -CH2-, NBu4);
0.88 (t, -CH3, NBu4). 13C NMR (CDCl3, δ (J, Hz)): 173.5 (s,
1J(Pt-C) ) 705, C5); 167.8 (s, 2J(Pt-C) ) 63, C2); 150.1 (s, 2J(Pt-
3.77 (s, OCH3); 3.39 (m, NCH2, NBu4); 1.63 (m, -CH2-, NBu4);
1.37 (m, -CH2-, NBu4); 0.85 (t, -CH3, NBu4). 13C NMR (CDCl3,
δ (J, Hz)): 173.4 (s, C5); 167.7 (s, C2); 156.5 (s, C4, C6H4-OCH3);
150.1 (s, C6); 138.8 (s, C10); 137.8 (s, C4); 132.4 (s, CH, C6H4-
OCH3); 130.3 (s, C9); 124.5 (s, C1, C6H4-OCH3); 123.3 (s, C7);
122.1 (s, C8); 114.4 (s, tentatively assigned to CRt); 113.6 (s, C3);
113.4 (s, CH, C6H4-OCH3); 103.0 (s, tentatively assigned to t
Câ); 59.0 (s, N-CH2, NBu4); 55.5 (s, OCH3); 24.5 (s, CH2, NBu4);
19.8 (s, CH2, NBu4); 14.0 (s, CH3, NBu4). ΛM(acetone): 98 mol-1
cm2 Ω-1
.
Preparation of (NBu4)[Pt(C∧N∧C)(CN)] (5). A mixture of [Pt-
(C∧N∧C)(dmso)] (0.30 g, 0.60 mmol) and (NBu4)CN (0.24 g, 0.90
mmol) in acetone (15 mL) was stirred at room temperature for 48
h. The resulting suspension was evaporated to dryness. The crude
solid was washed twice with water (5 mL) and recrystallized from
acetone/water to give a yellow microcrystalline solid (0.27 g, 65%).
Found: C, 58.65; H, 6.64; N, 5.99. Anal. Calcd for C34H47N3Pt:
C, 58.94; H, 6.84; N, 6.06. MS ES(-): m/z 450 M-, 100%. IR
(cm-1, Nujol): ν(CN) 2095(m). 1H NMR (CD3COCD3, δ (J,
Hz)): 7.99 (dd, J ) 7.1, ∼1.0, 3J(Pt-H) ) 34.7, H10); 7.61 (t, J )
2
C) ) 31, C6); 139.0 (s, J(Pt-C) ) 70, C10); 137.8 (s, C4); 131.4
3
(s, o-C, Ph); 130.3 (s, J(Pt-C) ) 40, C9); 127.9 (s, m-C, Ph);
3
123.5 (s, p-C, Ph); 123.3 (s, J(Pt-C) ) 26, C7); 122.1 (s, C8);
3
119.0 (s, i-C, Ph); 114.2 (s, CRt); 113.7 (s, J(Pt-C) ) 25, C3);
108.9 (s, 2J(Pt-C) ) 403, tCâ); 58.7 (s, N-CH2, NBu4); 24.3 (s,
CH2, NBu4); 19.7 (s, CH2, NBu4); 13.9 (s, CH3, NBu4). ΛM-
4
7.9, H4); 7.41 (d, J ) 7.6, H7); 7.34 (d, J ) 7.9, J(Pt-H) ) 6.5,
(acetone): 113 mol-1 cm2 Ω-1
.
H3); 7.05 (td, J ) 7.2, 1.3, 4J(Pt-H) ) 6.1, H9); 6.91 (td, J ) 7.5,
1.5, H8); 3.41 (m, NCH2, NBu4); 1.75 (m, -CH2-, NBu4); 1.38
(m, -CH2-, NBu4); 0.93 (t, -CH3, NBu4). 13C NMR (CDCl3, δ
Preparation of (NBu4)[Pt(C∧N∧C)(CtCTol)] (3). [Pt(C∧N∧C)-
(dmso)] (0.30 g, 0.60 mmol) was added to a solution of LiCt
CTol (4.80 mmol) in THF (15 mL) at -45 °C. The mixture was
stirred at this temperature for 2 min. The reaction mixture was then
allowed to warm to room temperature. The remaining steps were
identical to the procedure described for 1 (0.18 g, 39%). Found:
C, 64.38; H, 6.82; N, 3.99. Anal Calcd for C42H54N2Pt: C, 64.51;
H, 6.96; N, 3.58. MS MALDI(-): peak anion not observed. IR
(cm-1, Nujol): ν(CtC) 2103(sh), 2083(s). 1H NMR (CD3COCD3,
1
(J, Hz)): 171.3 (s, J(Pt-C) ≈ 703, C5); 168.3 (s, C2); 149.9 (s,
3
C6); 139.8 (s, J(Pt-H) ) 73, C10); 139.2 (s, C4); 131.2 (s, CN);
131.0 (s, 3J(Pt-H) ≈ 40, C9); 123.7 (s, 3J(Pt-H) ) 25, C7); 122.9
3
(s, C8); 114.1 (s, J(Pt-H) ≈ 30, C3); 58.8 (s, N-CH2, NBu4),
24.3 (s, CH2, NBu4); 19.7 (s, CH2, NBu4); 13.9 (s, CH3, NBu4).
ΛM(acetone): 145 mol-1 cm2 Ω-1
.
Preparation of (NBu4)[Pt(C∧N∧C)(S-2Py)] (6). A solution of
[Pt(C∧N∧C)(dmso)] (0.25 g, 0.50 mmol) in acetone was treated, at
0 °C, with NBu4OH (1.5 mL of a 0.7 M solution in MeOH) and
2-mercaptopyridine (0.067 g, 0.60 mmol). After stirring the mixture
for 5 min, the resulting red solution was evaporated to dryness and
3
δ (J, Hz)): 8.14 (d, J ) 6.7, J(Pt-H) ) 35.2, H10); 7.59 (t, J )
8.0, H4); 7.44 (d, J ) 7.4, H7); 7.35 (d, J ) 7.9, H3); 7.25 (t, J )
7.8, Tol); 7.07 (t, J ) 7.7, H9); 6.99 (d, J ) 7.8, Tol); 6.90 (td, J
) 8.0, 0.9, H8); 3.39 (m, N-CH2, NBu4); 2.26 (s, CH3, Tol); 1.65
(m, -CH2-, NBu4); 1.32 (m, -CH2-, NBu4); 0.85 (t, -CH3,
i
treated with cold PrOH to yield 6 as a red solid (0.31 g, 80%).
1
NBu4). 13C NMR (CDCl3, δ (J, Hz)): 173.6 (s, J(Pt-C) ) 704,
Found: C, 58.35; H, 6.83; N, 5.36; S, 4.26. Anal Calcd for
C38H51N3PtS: C, 58.74; H, 6.62; N, 5.41; S, 4.12. MS MALDI-
(-): peak anion not observed. 1H NMR (CD3COCD3, δ (J, Hz)):
8.03 (d, J ) 3.8, H2, SPy); 7.83 (d, J ≈ 8, H5, Spy); 7.80 (d, J )
2
2
C5); 167.8 (s, J(Pt-C) ) 64, C2); 150.1 (s, J(Pt-C) ) 29, C6);
139.0 (s, J(Pt-C) ) 69, C10); 137.7 (s, C4); 131.8 (s, C4, Tol);
2
131.3 (s, CH, Tol); 130.3 (s, J(Pt-C) ) 41, C9); 128.7 (s, CH,
3
Tol); 128.4 (s, C1, Tol); 123.3 (s, J(Pt-C) ) 26, C7); 122.0 (s,
3
3
8.0, J(Pt-H) ) 31, H10) (both signals overlap); 7.64 (t, J ) 7.9,
C8); 115.9 (s, tentatively assigned to CRt); 113.7 (s, J(Pt-C) )
3
4
H4); 7.44 (d, J ) 7.4, H7); 7.37 (d, J ) 8.0, J(Pt-H) ≈ 6, H3):
25, C3); 108.6 (s, 2J(Pt-C) ) 405, tCâ); 58.8 (s, N-CH2, NBu4);
6.90 (m, H8,9 dppy, CH, SPy); 6.52 (t, J ) 7.0, H3, SPy); 3.43 (m,
NCH2, NBu4); 1.75 (m, -CH2-, NBu4); 1.37 (m, -CH2-, NBu4);
0.93 (t, -CH3, NBu4). 13C NMR (CDCl3, δ (J, Hz)): the complex
6 is not stable enough in solution to record the spectrum.
24.3 (s, CH2, NBu4); 21.6 (s, CH3, Tol); 19.8 (s, CH2, NBu4); 14.0
(s, CH3, NBu4). ΛM(acetone): 120 mol-1 cm2 Ω-1
.
Preparation of (NBu4)[Pt(C∧N∧C){CtC(4-OCH3)C6H4)}] (4).
To a fresh (-50 °C) solution containing 8 equiv of LiCtC(4-
OCH3)C6H4 (4.8 mmol) in THF (15 mL) [Pt(C∧N∧C)(dmso)] (0.30
g, 0.6 mmol) was added, and the mixture was stirred at this
temperature for 2 min. The mixture was then allowed to reach room
temperature. The solvent was evaporated to dryness, and the red
solid residue was extracted with cold deoxygenated water (50 mL).
The resulting orange aqueous solution was rapidly filtered under
Ar through celite, and the filtrate was treated with vigorous stirring
with a solution of (NBu4)Br (0.29 g, 0.9 mmol) in 5 mL of H2O.
The resulting red solid was filtered, washed with water and iPrOH,
and air-dried (0.22 g, 48%). Found: C, 63.62; H, 6.52; N, 3.10.
Anal Calcd. for C42H54N2PtO: C, 63.22; H, 6.82; N, 3.51. MS ES-
ΛM(acetone): 90 mol-1 cm2 Ω-1
.
Preparation of (NBu4)[Pt(C∧N∧C)(CH2COCH3)] (7). A mea-
sure of 3 equiv of NBu4OH (1.1 mL of a 0.7 M solution in MeOH)
was added to a yellow solution of [Pt(C∧N∧C)(dmso)] (0.18 g, 0.37
mmol) in acetone (20 mL) at 0 °C. The resulting orange solution
was evaporated to ∼1 mL of volume, and the addition of H2O (25
mL) gave 7 as an orange solid, which was dried with anhydrous
MgSO4 in CH2Cl2 and recrystallized from CHCl3/Et2O (0.12 g,
45%). Found: C, 59.82; H, 7.32; N, 3.75. Anal. Calcd for C36H52-
ON2Pt: C, 59.73; H, 7.24; N, 3.87. MS ES(-): m/z 481 M-, 100%.
IR (cm-1, Nujol): ν(CdO) 1630(m). 1H NMR (CD3COCD3, δ (J,
3
Hz)): 7.96 (d, J ) 7.9, J(Pt-H) ) 23.4, H10); 7.57 (t, J ) 7.7,
1
4
(-): m/z 556 M-, 100%. IR (cm-1, Nujol): ν(CtC) 2081(s). H
H4); 7.39 (d, J ) 7.5, H7); 7.39 (d, J ) 7.6, J(Pt-H) ) 13, H3);
NMR (CD3COCD3, δ (J, Hz)): 8.15 (d, J ) 6.8, 3J(Pt-H) ) 35.7,
H10); 7.59 (t, J ) 7.9, H4); 7.44 (d, J ) 7.5, H7); 7.34 (d, J ) 7.9,
4J(Pt-H) ≈ 5.6, H3); 7.29 (d, J ) 7.5, CH, C6H4-OCH3); 7.07 (t,
H9); 6.90 (td, J ) 7.4, 1.2, H8); 6.78 (d, J ) 7.5, CH, C6H4-OCH3);
7.15 (t, J ) 6.6, H9); 6.89 (t, J ) 6.8, H8); 3.47, 3.40 (s, 2J(Pt-H)
) 114, 115, CH2, -CH2COCH3); 3.32 (m, NCH2, NBu4); 1.67 (m,
-CH2-, NBu4); 1.34 (m, -CH2-, NBu4); 1.03 (s, CH3, -CH2-
COCH3); 0.91 (t, -CH3, NBu4). 13C NMR (CDCl3, δ (J, Hz)): the
9922 Inorganic Chemistry, Vol. 46, No. 23, 2007

New Series of Anionic C,N,C Cyclometalated Pt Complexes
Scheme 1
complex 7 is not stable and soluble enough to record the spectrum.
ΛM(acetone): 102 mol-1 cm2 Ω-1
.
X-ray Crystallography. Table 4 reports details of the structural
analyses for all complexes studied. Red (1 and 4) or orange (6)
crystals were obtained by the slow diffusion of n-hexane into
dichloromethane (1 and 4) or fluorobenzene (6) solutions of each
compound at -30 °C. Orange crystals of complex 5 were prepared
by the slow evaporation of a solution of the complex in chloroform
at room temperature. For complex 4 one molecule of CH2Cl2 and
for complex 6 one-half a molecule of C6H5F were found in the
asymmetric unit, respectively. X-ray intensity data were collected
with a NONIUS κCCD area-detector diffractometer, using graphite-
monochromated Mo KR radiation. Images were processed using
the DENZO and SCALEPACK suite of programs.111 The structures
were solved by Patterson and Fourier methods using the DIRDIF92
program,112 and the absorption correction was performed using
SORTAV.113 All structures were refined by full-matrix least squares
on F2 with SHELXL-97,114 and all non-hydrogen atoms were
assigned anisotropic displacement parameters. The hydrogen atoms
were constrained to idealized geometries fixing isotropic displace-
ment parameters 1.2 times the Uiso value of their attached carbon
for the aromatic and CH2 hydrogens and that of 1.5 for the methyl
groups. For complex 5, which crystallizes in the noncentrosym-
metric space group P21, the crystal chosen for this structural analysis
was found to be a meroedric twin, as confirmed by the absolute
structure parameter (0.493(6)). Notwithstanding, inspection of the
symmetry (using PLATON115) reveals the possibility of the existence
of an inversion center. Thus, the structure has also been solved
and refined in the centrosymmetric group P21/c, but with worse
results. For 6‚0.5C6H5F, to establish the position of the N atom in
the 2-pyridyl-thiolate ligand, the structure was refined in three
different ways (with the identities of the p-C and N in one position,
with the element types reversed, and with a 50/50 hybrid scattering
factor at each of the affected atomic sites). Examination of the
∆MSDA values for bonds involving these atoms revealed the
correct assignment, with the nitrogen atom endo to the platinum
center.115,116 Furthermore, for complex 6‚0.5C6H5F, one aliphatic
chain (C35-C38) of the NBu4+ cation presents positional disorder,
which could be refined over three positions with partial occupancy
factors of 0.56/0.22/0.22. In this structure, the C6H5F molecule was
also disordered and modeled adequately. Finally, the structures
present one (5 and 6‚0.5C6H5F) or two (1 and 4‚CH2Cl2) residual
peaks greater than 1 e Å-3 in the vicinity of the platinum atoms or
the solvent (4‚CH2Cl2), but with no chemical significance.
acetonyl ligands. Treatment of [Pt(C∧N∧C)(dmso)] with an
excess of LiCtCR in diethyl ether (R ) tBu, 1) or THF (R
) Ph, 2; Tol, 3; (p-OMe)C6H4, 4), followed by reaction with
NBu4Br in deoxygenated water (see Experimental Section
for details), afforded the corresponding products as orange
(1-3) or red (4) solids in moderate yield (37-48%).
However, it is to be noted that all attempts to obtain the
analogous dinuclear derivative {[Pt(C∧N∧C)]2(1,4-Ct
CC6H4CtC)}2- under similar conditions, but starting from
[Pt(C∧N∧C)(dmso)] and Li2(CtCC6H4CtC) in a different
molar ratio, were unsuccessful. The reaction of [Pt(C∧N∧C)-
(dmso)] with a slight excess (1.5 equiv) of (NBu4)CN in
acetone gave 5 as a yellow microcrystalline product, while
complex 6 was isolated as a red microcrystalline solid by
reaction with HS-2Py in the presence of 2 equiv of (NBu4)-
OH at low temperature (0 °C). With the aim of preparing
the related hydroxy derivative, we also reacted [Pt(C∧N∧C)-
(dmso)] with 3 equiv of (NBu4)OH in acetone at 0 °C.
Nevertheless, the treatment of the resulting solution (see
Experimental Section) yielded the acetonyl complex 7 as an
orange microcrystalline solid. Metalated ketones are impor-
tant reagents in organic synthesis,117,118 those with transition
metals being of particular interest.119-123 The formation of
complex 7 is remarkable because the number of ketonyl
complexes of platinum(II) is rather scarce.123-125 In addition,
it is generated within minutes at room temperature. Other
Results and Discussion
The synthetic routes to complexes 1-7 are summarized
in Scheme 1. Starting from [Pt(C∧N∧C)(dmso)] (HC∧N∧CH
) 2,6-diphenylpyridine, dppy) we have synthesized new
anionic platinate(II) compounds by substitution of the dmso
molecule with anionic alkynyl (CtCR-), CN-, S-2Py-, and
(117) Seebach, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 1624.
(118) Culkin, D. A.; Hartwing, J. F. Acc. Chem. Res. 2003, 36, 234.
(119) Ogo, S.; Uehara, K.; Abura, T.; Fukuzumi, S. J. Am. Chem. Soc.
2004, 126, 3020.
(120) Masamune, S.; Choy, W.; Sita, L. R. Angew. Chem., Int. Ed.. 2004,
24, 1.
(121) Cheng, G. S.; Kwong, F. Y.; Chan, H. O.; Yu, W. Y.; Chan, A. S.
C. Chem. Commun. 2006, 1413.
(122) Sodeoka, M.; Hanashima, Y. Bull. Chem. Soc. Jpn. 2005, 78, 941.
(123) Vicente, J.; Abad, J. A.; Chicote, M. T.; Abrisqueta, M. A.; Lorca,
J. A.; Ram´ırez de Arellano, M. C. Organometallics 1998, 17, 1564.
(124) Vicente, J.; Arcas, A.; Ferna´ndez-Herna´ndez, J. M.; Bautista, D.
Organometallics 2006, 24, 4404.
(111) Otwinowski, Z.; Minor, W. In Methods in Enzymololgy; Carter, C.
V., Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol.
276A, p 307.
(112) Beursken, P. T.; Beursken, G.; Bosman, W. P.; de Gelder, R.; Garc´ıa-
Granda, S.; Gould, R. O.; Smith, J. M. M.; Smykalla, C. The
DIRDIF92 Program System; Technical Report of the Crystallography
Laboratory: University of Nijmegen: Nijmegen, The Netherlands,
1992.
(113) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(114) Sheldrick, G. M. SHELX-97, a Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(115) Spek, A. L. Acta Crystallogr. 1990, A46, C.
(125) Lai, S.-W.; Chan, M. C. W.; Cheung, K.-K.; Che, C.-M. Inorg. Chem.
1999, 38, 4262 and references therein.
(116) Hirshfeld, F. L. Acta Crystallogr., Sect. A 1976, 32, 239.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9923

Berenguer et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1,
4b‚CH2Cl2, 5, and 6‚0.5C6H5F
1
4‚CH2Cl2
5
6‚0.5C6H5F
Pt(1)-N(1)
Pt(1)-C(aryl)
2.012(3)
2.038(4)
2.045(4)
1.969(4)
2.012(4)
2.053(5)
2.064(6)
1.957(5)
2.031(5)
2.058(7)
2.062(7)
1.950(7)
1.996(3)
2.060(5)
2.064(5)
2.277(1)
Pt(1)-C(1)
(or S(1))
C(1)-C(2)
1.206(5)
1.483(5)
1.226(7)
1.435(7)
1.163(8)
1.762(5)
S(1)-C(1)
(or N(2))
C(2)-C(3)
C(aryl)-Pt(1)-C(aryl) 161.1(2)
160.9(2)
80.0(2)
80.9(2)
97.9(2)
101.2(2)
178.7(5)
161.0(2)
80.2(2)
80.8(2)
98.3(2)
100.8(2)
178.4(6)
161.6(2)
80.7(2)
80.9(2)
95.3(1)
103.1(1)
112.3(2) Pt(1)-
S(1)-C(1)
N(1)-Pt(1)-C(aryl)
80.4(2)
80.7(2)
97.3(2)
C(aryl)-Pt(1)-C(1)
(or S(1)) 101.6(2)
Pt(1)-C(1)-C(2)
175.2(4)
(or N(2))
C(1)-C(2)-C(3)
175.5(4)
174.5(5)
6 and 7) and in the solid state, and their identities have been
fully established by 1H NMR, 13C{1H} NMR, and IR
spectroscopies, and satisfactory elemental analyses. The
crystal structures of 1, 4, 5, and 6 have also been determined.
Different red crystals of 7, obtained from evaporation of
acetone solutions of the complex, were subjected to several
X-ray diffraction studies. Unfortunately, the crystals were
not of sufficient quality to give high accuracy analyses,
although the connectivity shown in Scheme 1, with the
presence of the acetonyl ligand, can be unequivocally
established since it has also been confirmed by the ES(-)
mass spectrum (481 [Pt(C∧N∧C)(CH2COCH3)]- 100%).
The alkynyl derivatives 1-4 show one ν(CtC) intense
absorption in the expected region (2081-2091 cm-1), with
a shoulder in complexes 2 and 3 (2105 cm-1, 2; 2103 cm-1,
3) probably due to effects in the solid state, while complex
5 shows one ν(CtN) absorption at 2095 cm-1, corresponding
to the terminal cyanide ligand, and in the IR spectrum of
compound 7 the absorption due to the ν(CdO) of the
acetonyl group can be observed at 1630 cm-1. Also, the
conductivity measurements of all of them (1-7) confirm their
behavior as 1:1 electrolytes. Well-resolved 1H and 13C{1H}
NMR spectra were observed for all derivatives (except for
complexes 6 and 7, whose 13C{1H} NMR spectra could not
be recorded, as they decompose in solution). The assignments
of the signals (see Experimental Section), consistent with
the presence of symmetric dicyclometalated (C∧N∧C) ligand,
1
were made on the basis of coupling constants and H-1H
COSY and g-HSQC experiments carried out on complexes
1 and 5.
Figure 2. ORTEP view of the molecular anions in complexes 1 (a), 4
(b), 5 (c), and 6 (d). Ellipsoids are drawn at the 50% probability level.
Hydrogen atoms and solvent have been omitted for clarity.
Crystal structure determination: Perspective drawings of
the complex anions of 1 and 4-6 are given in Figure 2.
Selected bond lengths and angles are shown in Table 1.
Complex 5 crystallizes in the noncentrosymmetric space
group P21, showing, in the asymmetric unit, two different
ketonyl derivatives have been prepared by reacting ketones
with hydroxo complexes126-130 or with chloro complexes in
the presence of a base,123,131-133 but on the whole, they need
longer reaction times127,132,133 or harsh thermal condi-
tions.123,126,128-131 Despite their anionic nature, all complexes
are stable in solution (CH2Cl2, CHCl3, and acetone, except
(129) Bennet, M. A.; Yoshida, T. J. Am. Chem. Soc. 1978, 100, 1750.
(130) Yoshida, T.; Okano, T.; Otsuka, S. J. Chem. Soc., Dalton Trans.
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(131) Lai, S.-W.; Chan, M. C. W.; Cheung, K.-K.; Che, C.-M. Inorg. Chem.
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(132) Almeida, J. F.; Pidcock, A. J. Organomet. Chem. 1981, 209, 415.
(133) Cairus, M. A.; Dixon, K. R.; Smith, M. A. R. J. Organomet. Chem.
1977, 135, C33.
(126) Ruiz, J.; Mart´ınez, M. T.; Rodr´ıguez, V.; Lo´pez, G.; Pe´rez, J.;
Chaloner, P. A.; Hitchcock, P. B. Dalton Trans. 2004, 3521.
(127) Arnold, D. P.; Bennett, M. A. J. Organomet. Chem. 1980, 199, 119.
(128) Appleton, T. G.; Bennet, M. A. Inorg. Chem. 1978, 17, 738.
9924 Inorganic Chemistry, Vol. 46, No. 23, 2007

New Series of Anionic C,N,C Cyclometalated Pt Complexes
Table 2. Absorption Data (5 × 10-5 M CH2Cl2 Solutions) for Complexes 1-7
compound
absorption/nm (10-3 ꢀ/M-1 cm-1
)
(NBu4)[Pt(C∧N∧C)(CtCBut)], 1
231(32.8), 249(36,4), 258(29.3),
277sh(32.0); 287(36.8), 330(9.7),
364(8.5), 423(5.6), 532(0.2)
(NBu4)[Pt(C∧N∧C)(CtCPh)], 2
(NBu4)[Pt(C∧N∧C)(CtCTol), 3
(NBu4)[Pt(C∧N∧C){CtC(4-OCH3)C6H4}], 4
(NBu4)[Pt(C∧N∧C)(CN)], 5
231 (25.6), 242sh(24.6), 277sh(27.4),
287(29.9), 328sh(14.5), 355sh(9.1),
371sh(6.2), 421(3.6), 527 (0.1)
231(26.0), 242(25.1), 258 (25.0),
276(26.1), 287(25.7), 330sh(12.1),
363sh(6.4), 422(3.1), 529 (0.2)
232(33.3), 243(35.1), 256sh(35.3),
277sh(41.4), 287(42.3), 328(16.8),
368(11.4), 423(8.3), 529(0.6)a
230(13.9), 244sh(19.4), 259(29.4),
275(31.6), 283(32.5), 316(6.7),
348(8.7), 365sh(7.8), 427(0.6),
452(0.5),a 516(0.1)a
(NBu4)[Pt(C∧N∧C)(S-2Py)], 6
231(25.9), 246(27.6), 278sh(23.4),
286(24.1), 328sh(12.0), 369(6.7),
396(5.0), 462(1.9), 529(1.1)a
(NBu4)[Pt(C∧N∧C)(CH2COCH3)], 7
232(34.8), 243sh(33.3), 265sh(29.3),
271(28.3), 303sh(17.4), 327sh(11.2),
364(5.4), 412(2.0), 472(0.4),a 529(0.1)a
a These absorptions follow the Lambert-Beer Law in the range of 5 × 10-5 to 10-3 M.
molecular anions, both having identical structural details
within experimental error. Therefore, only one of them will
be considered in the discussion. As expected, in all anions,
the platinum(II) center adopts a distorted square-planar
geometry with trans aryl carbon atoms C-Pt-C (range )
160.9(2)-161.6(2)°) significantly deviated from linearity due
to the steric restriction caused by the dicyclometalated ligand
(C∧N∧C). The anion [Pt(C∧N∧C)(CN)]- (5-) and the central
“Pt(C∧N∧C)(CtCR)” core in the alkynyl anions of 1- and
4- are essentially planar, with the p-OMe-C6H4 ring in 4
forming a dihedral angle of 17.5(1)° with the platinum
coordination plane. In 6-, the 2-pyridinthiolate ligand is not
coplanar with the Pt(C∧N∧C) moiety (dihedral angle 51.00-
(7)°) and is oriented with the nitrogen atom N(2) exo to the
platinum center. The Pt-CR alkynyl bonds in 1- and 4- and
the Pt-C(tN) bond in 5- (1.969(4) Å, 1; 1.957(5) Å, 4;
and 1.950(7) Å, 5) are unexceptional and compare well with
those of related complexes. In 6-, the Pt-S bond (2.277(1)
Å) is within the range of those observed for typical platinum-
(II) dithiolate derivatives134,135 and close to the values found
in [Pt(bpy)(S-2Py)2] (2.300(3) Å)136 or [Pt(terpy)(S-2Py)]+
(2.299(2) Å).136 Evidence that has gradually been ac-
cumulated over the last decades shows that weak hydrogen
bonds137-140 are almost ubiquitous, this being an important
factor in controlling crystal packing and playing a vital role
in various specific phenomena in chemistry and biochemistry,
including molecular recognition. Further inspection of the
crystal structures of four complexes reveals the presence of
different types of weak intermolecular hydrogen bonds,
including C-H‚‚‚π47,141-147 (aromatic, C‚‚‚C ) 3.38-3.84
Å, H‚‚‚C ) 2.66-3.23 Å, C-H‚‚‚C ) 176-113°; CtC,
C‚‚‚C ) 3.41-3.76 Å, H‚‚‚C ) 2.66-2.94 Å, C-H‚‚‚C )
172-119°), C-H‚‚‚N148-151 (C‚‚‚N ) 3.26-3.84 Å, H‚‚‚N
) 2.54-2.96 Å, C-H‚‚‚N ) 165-109°), C-H‚‚‚O152-155
(C‚‚‚O ) 3.68-3.75 Å, H‚‚‚O ) 2.72-3.22 Å, C-H‚‚‚O
) 173-118°), C-H‚‚‚S156-159 (C‚‚‚S ) 3.76-3.81 Å,
H‚‚‚S
)
2.90-3.00 Å, C-H‚‚‚S
)
143-141°),
C-H‚‚‚Cl141,153,160-163 (C‚‚‚Cl ) 3.51-3.90 Å, H‚‚‚Cl )
(141) Bernechea, M.; Lugan, N.; Gil, B.; Lalinde, E.; Lavigne, G.
Organometallics 2006, 25, 684.
(142) Nishio, M. CrystEngComm 2004, 6, 130 and references therein.
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Chem.sEur. J. 2003, 9, 6155 and references therein.
(145) Suezawa, H.; Yoshida, T.; Umezawa, Y.; Tsuboyama, S. T.; Nishio,
M. Eur. J. Inorg. Chem. 2002, 3148.
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(147) Steiner, T.; Tamm, M. J. Organomet. Chem. 1998, 570, 235.
(148) Maly, K. E.; Maris, T.; Gagnon, E.; West, J. D. Cryst. Growth Des.
2006, 6, 461.
(149) Stephenson, M. D.; Hardie, M. J. Cryst. Growth Des. 2006, 6, 423.
(150) Basavoju, S.; Aitipamula, S.; Desiraja, G. R. CrystEngComm 2004,
6, 120.
(151) Desiraju, G. R. Acc. Chem. Res. 2002, 35, 565.
(152) Gil, B.; Fornie´s, J.; Go´mez, J.; Lalinde, E.; Mart´ın, A.; Moreno, M.
T. Inorg. Chem. 2006, 45, 7788.
(153) Sreerama, S. G.; Pal, S. Inorg. Chem. 2005, 44, 6299.
(154) Desiraju, G. R. Chem. Commun. 2005, 2995.
(155) Potrzebowski, M. J.; Michalska, M.; Koziol, A. E.; Kazmierski, S.;
Lis, T.; Pluskowski, J.; Ciesielski, W. J. Org. Chem. 1998, 63, 4209.
(156) Novakovic, S. B.; Fraisse, B.; Bogdanovic, G. A.; Spasojevic´-de Bire´,
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(157) Ma, C.; Zhang, Q.; Qiu, L. J. Organomet. Chem. 2005, 690, 3033.
(158) Planas, J. G.; Vin˜as, C.; Teixidor, F.; Comas-Vives, A.; Ujaque, G.;
Lledos, A.; Light, M. E.; Hursthouse, M. B. J. Am. Chem. Soc. 2005,
127, 15976.
(134) Berenguer, J. R.; Bernechea, M.; Fornie´s, J.; Garc´ıa, A.; Lalinde,
E.; Moreno, M. T. Inorg. Chem. 2004, 43, 8185.
(135) Paw, W.; Lachicotte, R. J.; Eisenberg, R. Inorg. Chem. 1998, 37,
4139.
(136) Tzeng, B.-C.; Fu, W.-F.; Che, C.-M.; Chao, H. Y.; Cheung, K.-K.;
Peng, S.-M. J. Chem. Soc., Dalton Trans. 1999, 1017.
(137) Nishio, M. In Weak Hydrogen Bonds; Atwood, J. L., Steed, J. W.,
Eds.; Marcel Dekker, Inc.: New York, 2005; pp 1576.
(138) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in Structural
Chemistry and Biology; Oxford University Press: Oxford, 1999.
(139) Aakero¨y, C. B.; Seddon, K. R. Chem. Soc. ReV. 1993, 397.
(140) Pimentel, G. C.; McClellan, A. L. The Hydrogen Bond; W. H.
Freeman: San Francisco, 1960.
(159) Cosp, A.; Larrosa, I.; Anglada, J. M.; Bofill, J. M.; Romea, P.; Urpi,
F. Org. Lett. 2003, 5, 2809.
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Inorganic Chemistry, Vol. 46, No. 23, 2007 9925

Berenguer et al.
2.89-3.12 Å, C-H‚‚‚Cl ) 157-112°), and C-H‚‚‚F164-167
(C‚‚‚F ) 3.16-3.48 Å, H‚‚‚F ) 2.34-2.67 Å, C-H‚‚‚F )
158-118°). The weakness of most of these hydrogen
interactions may be due not only to the soft acidity of the
C-H donor bond142 but also to the steric requirement of the
+
NBu4 cation. Notwithstanding, these interactions seem to
be strong enough to arrange the solid-state structure of
complexes 1, 4‚CH2Cl2, 5, and 6‚0.5C6H5F, leading to the
generation of supramolecular networks (bidimensional shee-
tlike organization in complex 1 or 3D architecture in
complexes 4-6 (see Figures S1-S4 in the Supporting
Information).
Electronic Absorption and Emission Spectroscopy. The
UV-vis absorption data are summarized in Table 2. Com-
plexes 1-4 display absorption maxima below 370-363 nm,
which are attributed to ligand-centered transitions (1IL π f
π*) of the dicyclometalated C∧N∧C and alkynide groups,
together with a low-energy band (ꢀ ) 3.1-8.3 103 dm3 mol-1
cm-1) that appears to be fairly insensitive to the alkynyl
substituent (423 nm, 1 and 4; 421 nm, 2; 422 nm, 3). Pre-
vious work on related neutral derivatives [Pt(C∧N∧C)L]108,168
has attributed this absorption to a spin-allowed dπ(Pt) f
Figure 3. UV-vis absorption spectrum of 4 in CH2Cl2 (5 × 10-5 M).
Inset: absorbance variation of the low-energy band (529 nm) in the
concentration range of 5 × 10-5 to 1 × 10-3 M.
1
π* MLCT transition. A similar assignment is therefore
suggested for this absorption (421-423 nm) in complexes
1-4. In agreement with this assignment, the low-energy
absorption in related neutral complexes [Au(C∧N∧C)(Ct
CR)] reported by Yam et al. appears at higher energies (399-
402 nm)169 and has been assigned as a metal-perturbed
intraligand (IL) π-π* transition of the CNC ligand. All four
complexes of 1-4 also show a very weak band at 527-532
nm (ꢀ ) 0.1-0.6 103 dm3 mol-1 cm-1). As an illustrative
example of the influence of complex concentration on this
band, the absorption spectra of 4 in the concentration range
of 5 × 10-5 to 10-3 M were recorded. As is shown in the
inset of Figure 3, the intensity of the low-energy absorption
at 529 nm increases with the concentration. A linear plot of
absorbance versus concentration demonstrates that this band
(529 nm) obeys Beer’s Law, which excludes the presence
of ground-state oligomerization processes. Both ligands
(C∧N∧C and CtCR) are strong σ donors, and hence, ligand-
field d-d transitions are unlikely to occur at such low
energies. The very weak bands (527-532 nm) are tentatively
Figure 4. UV-vis absorption spectrum of 5 in CH2Cl2 (5 × 10-5 M).
Inset: absorbance variation of the two low-energy bands (452 and 516 nm)
in the concentration range of 5 × 10-5 to 1 × 10-3 M.
tion spectra of 5 and 7 were examined in the 5 × 10-5 to
10-3 M concentration range. As shown in Figure 4 for
complex 5, the absorption spectra reveal two very weak
features at 452 and 516 nm in CH2Cl2 (472 and 529 nm for
7), which obey Beer’s Law, being tentatively attributed to
the direct population of 3MLCT and 3ππ states, respectively.
In both complexes 5 and 7, the absorption profile of these
low-energy bands is similar in MeCN. The vibronic-
structured bands at 316-365 nm for complex 5 comprise at
least two overlapping bands, which are assigned to an
3
attributed to direct population of a π-π (C∧N∧C) state,
facilitated by the high spin-orbit coupling associated with
the Pt(II) ion. A similar assignment has been suggested for
an absorption at similar energies in related neutral [Pt-
(C∧N∧C)L] complexes.55 In complex 7, the low-energy band
at 412 nm (ꢀ ) 2.0 103 dm3 mol-1 cm-1) is attributed, as in
complexes 1-4, to 1MLCT transition. The electronic absorp-
1
1
admixture of IL (ππ*) and MLCT transitions. In this
1
complex (5), the large destabilization of MLCT from the
alkynyl (421-423 nm, 1-4) and ketonyl (412 nm, 7)
derivatives could be attributed to the strongly electron-
withdrawing character of the CN- ligand, as has been
previously noted in other polypyridyl platinum complexes
containing the strong field cyanide ion.53,170-172 The 2-py-
(163) Sarma, J. A. R. P.; Desiraju, G. R. Acc. Chem. Res. 1986, 19, 222.
(164) Chopra, D.; Thiruvenkatam, V.; Manjunath, S. G.; Guru Row, T. N.
Cryst. Growth Des. 2007, 7, 868.
(165) Berenguer, J. R.; Fornie´s, J.; Lalinde, E.; Mart´ın, A.; Serrano, B. J.
Chem. Soc., Dalton Trans. 2001, 2926 and references therein.
(166) Thornberry, M. P.; Slebodnick, C.; Deck, P. A.; Fronczek, F. R.
Organometallics 2000, 19, 5352.
(167) Dunitz, J. D.; Taylor, R. Chem.sEur. J. 1997, 3, 89.
(168) Lai, S. W.; Lam, H. W.; Lu, W.; Cheung, K. K.; Che, C. M.
Organometallics 2002, 21, 226.
(169) Wong, K. M.-C.; Hung, L.-L.; Lam, W. H.; Zhu, N.; Yam, V. W.-
W. J. Am. Chem. Soc. 2007, 129, 4350.
(170) Wilson, M. H.; Ledwaba, L. P.; Field, J. S.; McMillin, D. R. Dalton
Trans. 2005, 2754.
(171) Field, J. S.; Haines, R. J.; Ledwaba, L. P.; McGuire, J. R.; Munro,
O. Q.; Low, M. R.; McMillin, D. R. Dalton Trans. 2007, 192.
(172) Connick, W. B.; Marsh, R. E.; Schaefer, W. P.; Gray, H. B. Inorg.
Chem. 1997, 36, 913.
9926 Inorganic Chemistry, Vol. 46, No. 23, 2007

New Series of Anionic C,N,C Cyclometalated Pt Complexes
Table 3. Photophysical Data for Complexes 1-7
compound
medium (T/K)
λ
em/nm
τ/µs
(NBu4)[Pt(C∧N∧C)(CtCtBu)], 1
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5 M (77)
CH2Cl2 1 × 10-3 M (77)
not emissive
493, 529(λexc390)
572, 675(λexc454)
675 (λexc524)
16.4
19.5 at 572 nm
11.0 at 675 nm
solid (298)
not emissive
solid (77)
675(λexc520)
10.5
(NBu4)[Pt(C∧N∧C)(CtCPh)], 2
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5M (77)
CH2Cl2 1 × 10-3 M (77)
not emissive
493, 526, 623sh(λexc380)
572, 635, 665sh(λexc464)
635sh, 665(λexc520)
606(weak, λexc500)
638(λexc515)
27.9
∼14.4 at 572-635 nm
9.9 at 665 nm
solid (298)
solid (77)
13.1
(NBu4)[Pt(C∧N∧C)(CtCTol)], 3
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5 M (77)
CH2Cl2 1 × 10-3 M (77)
not emissive
497, 527, 665(weak)(λexc390)
560, 630, 655sh(λexc460)
630, 655(λexc520)
639 (weak, λexc475)
658(λexc517)
9.5
∼13.2 at 560-600 nm
7.5 at 655 nm
solid (298)
solid (77)
9.4
(NBu4)[Pt(C∧N∧C){CtC(4-OCH3)C6H4}], 4
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5 M (77)
CH2Cl2 1 × 10-3 M (77)
not emissive
508, 532, 626sh, 665(λexc400)
508, 550, 660(λexc450)
660(λexc520)
20.1
7.4 at 508 nm;
9.6 at 550 nm;
7.5 at 660 nm
solid (298)
solid (77)
618, 636(weak, λexc490)
666(λexc520)
8.6
(NBu4)[Pt(C∧N∧C)(CN)], 5
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5 M (77)
not emissive
490(weak), 525(weak), 560,
623 (λexc375-450)
15.6 at 490-525 nm;
13.0 at 560 nm;
8.8 at 623 nm
7.2
CH2Cl2 1 × 10-3 M (77)
solid (298)
628(λexc452-500)
590(weak, λexc438)
631(λexc510)
solid (77)
12.3
(NBu4)[Pt(C∧N∧C)(S-2Py)], 6
CH2Cl2 5 × 10-5 M (298)
CH2Cl2 5 × 10-5 M (77)
CH2Cl2 1 × 10-3 M (77)
not emissive
508, 530, 570sh(λexc440)
513, 555, 620(λexc440)
640, 660(λexc525)
17.2
8.9 at 513 nm;
8.5 at 555 nm;
5.7 at 640-660 nm
solid (298)
not emissive
solid (77)
640(λexc515)
11.3
(NBu4)[Pt(C∧N∧C)(CH2COCH3)], 7
CH2Cl2 5 × 10-5 M (298)
not emissive
CH2Cl2 5 × 10-5 M (77)
CH2Cl2 1 × 10-3 M (77)
485, 510, 545, 585(λexc375)
510, 545, 585, 610(λexc460)
485sh, 510, 550, 585(λexc380)
510, 550, 585(λexc460)
550, 585, 675(λexc500)
675(λexc525)
21.6 at 485 nm
13.5 at 585 nm
8.8 at 675 nm
solid (298)
solid (77)
not emissive
612, 660(λexc460-515)
10.7 at 612 nm
9.6 at 660 nm
ridinthiolate derivative 6 shows intense absorption bands at
246-396 nm and two broad low-energy peaks at 462 (ꢀ )
1.9 103 dm3 mol-1 cm-1) and 529 (1.1 103 dm3 mol-1 cm-1),
respectively. The high-energy bands are due to IL transitions,
although a detailed assignment is impeded by band overlap-
ping. According to previous studies135,173-175 of diimine and
polypyridine thiolate derivatives in which the low-energy
absorptions have been systematically attributed to ligand
(thiolate) or metal-thiolate-to-ligand (polyimine) charge-
transfer transitions, we assign the band at 462 nm to a
LL′CT.176 In accordance with this assignment, this band
exhibits a negative solvatochromic behavior, appearing at
435 nm in a polar solvent such as MeCN. This behavior is
indicative of a significant difference between the ground-
and excited-state dipole moments, and is typical of MLCT/
LLCT transitions.177 The weakest manifold at 529 nm seen
in CH2Cl2 could be assigned to a single-triplet satellite, which
would be of considerable oscillator strength due to the
presence of a heavy Pt(II) center.178
Emission Properties. The emission data for all the
complexes are depicted in Table 3. All complexes are
intensely luminescent in low temperature (77 K) rigid matrix
(glassy CH2Cl2 and in the solid state) while they are
nonemissive in fluid solution, probably caused by efficient
(176) It should be noted that the analogous absorption CT band in related
dithiolatediimineplatinum(II) systems has been designated as
MMLL′CT (mixed metal ligand-to-ligand charge transfer), indicating
that significant metal character exits in the HOMO (ref 175).
(177) Lever, A. B. P. Inorganic Electronic Spectroscopy, 2nd ed.; Elsevier
Amsterdam: Oxford, 1984.
(173) Vogler, A.; Kunkely, H. J. Am. Chem. Soc. 1981, 103, 1559.
(174) Vogler, A.; Kunkely, H. J. Am. Chem. Soc. 1990, 112, 5625.
(175) Paw, W.; Cummings, R. J.; Mansour, M. A.; Connick, W. B.; Geiger,
D. K.; Eisenberg, R. Coord. Chem. ReV. 1998, 171, 125.
(178) Weinstein, J. A.; Blake, A. J.; Davies, E. S.; Davis, A. L.; George,
M. W.; Grills, D. C.; Lileev, I. V.; Maksimov, A. M.; Matousek, P.;
Mel’nikov, M. Y.; Parker, A. W.; Platonov, V. E.; Towrie, M.;
Wilson, C.; Zheligovskaya, N. N. Inorg. Chem. 2003, 42, 7077.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9927

Berenguer et al.
Table 4. Crystallographic Data for 1, 4, 5, and 6
1
4‚CH2Cl2
5
6‚0.5C6H5F
empirical formula
fw
C39H56N2Pt
747.95
C43H56Cl2N2OPt
882.89
C34H47N3Pt
692.84
C41H53.5F0.5N3Pt
825.02
T (K)
173(1)
100(1)
100(1)
100(1)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
monoclinic
P21/c
9.8700(1)
16.3790(2)
22.1480(3)
90
96.400(1)
90
3558.15(7)
4
monoclinic
P21/a
9.1570(3)
38.6540(12)
11.8350(4)
90
108.951(1)
90
3962.0(2)
4
monoclinic
P21
9.8599(3)
18.5513(7)
16.5784(6)
90
91.567(2)
90
3031.29(18)
4
monoclinic
P21/a
18.0030(7)
10.0970(2)
20.5330(8)
90
96.496(1)
90
3708.4(2)
4
Z
D
calcd (Mg/m3)
1.396
3.971
1528
1.480
3.711
1792
1.518
4.655
1400
1.478
3.875
1676
abs coeff (mm-1
F(000)
)
cryst size (mm)
0.40 × 0.30 × 0.20
2.49 to 27.94
8486/0/386
1.041
0.30 × 0.20 × 0.10
1.05 to 27.70
9220/0/442
1.209
0.20 × 0.10 × 0.10
1.23 to 27.84
14202/1/686
1.023
0.20 × 0.15 × 0.10
2.28 to 27.48
8501/14/403
1.036
θ range for data collection (deg)
no. of data/restrains/params
GOF on F2
final R indices [I > 2σ(I)]
R1 ) 0.0352,
R2 ) 0.0820
R1 ) 0.0517,
R2 ) 0.0891
1.242 and -1.390
R1 ) 0.0358,
R2 ) 0.0903
R1 ) 0.0617,
R2 ) 0.1341
1.243 and -1.946
R1 ) 0.0362,
R2 ) 0.0687
R1 ) 0.0571,
R2 ) 0.0741
1.022 and -1.498
R1 ) 0.0404,
R2 ) 0.0830
R1 ) 0.0652,
R2 ) 0.0899
1.825 and -1.552
R indices (all data)
largest diff peak and hole (e·A-3
)
nonradiative decay via low-lying d-d excited states or
solvent interactions in the open coordination states. In the
solid state at 298 K, lumophore quenching due to weak
hydrogen contacts seems to be prevalent, so only very weak
or negligible emission is observed. Figure 5 shows the
emission spectra in CH2Cl2 glass and at low concentrations
(5 × 10-5 mol dm-3) for 1-4 and 6. The structured
emissions observed at 493-508 nm, with vibrational spacing
of about 1300 cm-1, are reminiscent of those observed in
related neutral [Pt(C∧N∧C)L],108 [Au(C∧N∧C)(CtCR]179
(470-529 nm), and [Au(C∧N∧C)(SPy)]180 (488 nm) com-
plexes. This fact and the long emission lifetimes (9.5-27.9
µs), which are suggestive of triplet parentage, indicate that
the emissions presumably come from states of metal-
and 2, the excitation spectra monitored at 572 nm and at the
low-energy band (675 nm for 1 and ∼665 nm for 2) were
also found to be different, indicating that the two emissive
bands are from different origins tentatively attributed to
excimeric and ground-state aggregation of the complexes.
The absence of monomeric emissions at 10-3 M for
complexes 1 and 2 indicates a stronger tendency of these
compounds to form excimers or aggregates. In complexes 4
and 6, the presence of more bulky CtC(p-OMe)C6H4 and
S-2Py ligands makes such processes less favorable. In
agreement with this hypothesis, the planar cyanide complex
5 exhibits, even at low concentration (5 × 10-5 M), in
addition to the vibronic-structured emission (see Figure 7)
due to the 3ππ*(IL) excited state with a long lifetime (∼15.6
µs), a broad emission centered at 623-628 nm, attributed
to oligomerization with a shorter lifetime (∼7.2 µs). Upon
increasing the concentration to 5 × 10-4 M, only the low
emission is observed (see Figure 7). Interestingly, the ketonyl
derivative 7 exhibits two different vibronic bands with
different emissive origins (485 and 510 nm) at low concen-
tration (10-5 M), clearly visible by changing the excitation
wavelength. Excitation at 360-390 nm produces an emission
vibronic profile with peak maxima starting at 485 nm, while
excitation at longer wavelengths (460 nm) gives rise to a
vibronic emission with peak maxima at 510, 545, 585, and
610 nm (Figure S8, Supporting Information). Lifetime
measurements recorded at 485 (λexc 375) and 585 nm (λexc
460) give values of 21.6 and 13.5 µs, respectively, confirming
long-lived spin-forbidden excited states. These emissions are
3
perturbed π-π* (C∧N∧C) origin. Time-resolved emission
profiles for 1-4 and 6 (Figures S5-S7, Supporting Informa-
tion) show the presence of monoexponential decay, thus
implying that at low concentrations a single emitting species
is present. However, the emission profiles are sensitive to
complex concentration (see Table 3 and Figure 6 for complex
4). Thus, with increasing concentration, complexes 3, 4, and
6 develop two additional bands centered around 550-560
and 640-660 nm. The structured high-energy emission is
visible even at a concentration of 10-3 M. At this concentra-
tion (10-3 M), complexes 1 and 2 show only the two low
emission bands centered at 572 and 665-675 nm. As shown
in Figure 6 for complex 4, the excitation spectra monitored
at 508 and 550 nm are similar, suggesting that the band at
550 nm is excimeric in nature. However, the excitation
profile of the low-energy band at 665 nm is different,
suggesting that this band originates from emissive states
resulting from ground-state aggregation. For complexes 1
3
3
tentatively attributed to ππ*(IL) and MLCT (or a mixed
3IL/3MLCT manifold), respectively. As in the remaining 1-6
complexes, two additional low-energy emissions at ca. 585
and 675 nm, respectively, due to excimeric/ground state 3ππ
excited states are also observed by increasing the concentra-
tion to 10-3 M. The appearance of low-energy bands at 77
(179) Yam, V. W.-W.; Wong, K. M. C.; Hung, L. L.; Zhu, N. Angew.
Chem., Int. Ed. 2005, 44, 2.
(180) Wong, K.-H.; Cheung, K.-K.; Chan, M. C.-W.; Che, C.-M. Orga-
nometallics 1998, 17, 3505.
9928 Inorganic Chemistry, Vol. 46, No. 23, 2007

New Series of Anionic C,N,C Cyclometalated Pt Complexes
Figure 5. Emission spectra of complexes 1-4 and 6 in CH2Cl2 glasses
(5 × 10-5 M, 77 K).
Figure 8. Solid-state emissions of 3 at 298 and 77 K.
temperature. In the solid state at 298 K, all complexes
(except 1 and 7) exhibit a weak emission with λmax between
590 nm (5) and 639 nm (3). Upon cooling to 77 K, the
emissions increase their intensity, with λmax values red-shifted
to 631 nm (5) to 666 nm (4). At low temperatures, complex
1 is also emissive, exhibiting a broad unstructured band
centered at λmax 675 nm. The emission profile of complex 7
(77 K, solid) is slightly dependent on excitation wavelength,
exhibiting a band at 612 with a shoulder at 660 by excitation
at 460 nm. However, the shoulder increases its intensity by
excitation at 515 nm. As an illustration of this, Figure 8
shows the solid-state emission of complex 3 at 298 and 77
K. These emissions are comparable to the low-energy
emissions observed in the 77 K CH2Cl2 glasses, and
therefore, we tentatively attribute the emissions to ground
state (or excimeric) 3ππ* excited states. The red shift to lower
energies observed at 77 K relative to room temperature can
be attributed to a lattice compression of the solid sample at
low temperature.
Figure 6. Steady-state spectra of CH2Cl2 glasses of 4 at different
concentrations.
Conclusions
Mononuclear anionic cyclometalated complexes (NBu4)-
[Pt(C∧N∧C)X] (HC∧N∧CH ) 2,6-diphenylpyridine, X ) Ct
CR, 1-4; CN, 5; S-2Py, 6; CH2COCH3, 7) have been
prepared and fully characterized. The solid-state structures
of complexes 1, 4, 5, and 6 have been determinated showing,
in all the cases, the presence of several types of weak
hydrogen interactions, which lead to the formation of
supramolecular networks. The electronic absorption spectra
of 1-5 and 7 are dominated by IL ππ* and MLCT tran-
sitions. In complex 6, the lower-energy absorption is at-
tributed to a LL′CT transition. In all complexes, the weak
absorption at 516-532 nm is thought to be due to spin-
forbidden π-π* (C∧N∧C) (3IL) transition. The emissions
3
Figure 7. Emission spectra of 5 for CH2Cl2 glasses (77 K) at different
concentrations.
at 77 K are sensitive to solvent concentration. In dilute glassy
solutions, complexes 1-4 and 6 exhibit highly structured
bands, which are assigned to a metal-perturbed 3ππ* excited
state, while complex 5 also shows an additional low-energy
K for glasses in all complexes, due to ground-state oligo-
merization, is not unprecedented,55,181 although they appeared
to obey Beer’s Law in their electronic absorption at room
(181) Sun, F. G.; Lin, Y.; Schanze, K. S. Inorg. Chem. 2005, 44, 4055.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9929

Berenguer et al.
emission attributed to ground-state aggregation. For the
Acknowledgment. We wish to thank the Ministerio de
Ciencia y Tecnolog´ıa, Spain, and the European Regional
Development Fund (Project CTQ2005-08606-C02,02/BQU)
for financial support. J.T. wishes to thanks the C. A. R. for
a grant.
ketonyl derivative 7, a dual emission is observed, which is
3
3
tentatively attributed to the fact that ππ*(IL) and MLCT
(or mixed 3ππ*(IL)/3MLCT) excited states are not coupled.
Complexes 3, 4, 6, and 7 exhibit two additional low-energy
emissions (∼575 and ∼670 nm) when the concentration is
increased, which are tentatively assigned to excimeric and
ground-state oligomerization of the complexes, respectively.
The following tendency to exhibit excimeric and ground state
oligomerization is observed: 7 < 3 ≈ 4 ≈ 6 < 1 ≈ 2 < 5.
The broad and unstructured emissions observed in the solid
state (298 and 77 K) compare well to the low-energy
emissions observed in the 77 K CH2Cl2 glasses and,
therefore, are similarly assigned.
Supporting Information Available: Figures of bidimensional
organization of complex 1 (Figure S1) and 3D arrangement of
complexes 4-6 (Figures S2-S4); time-resolved emission profiles
for complexes 1, 3, and 6 (Figures S5-S7) and steady-state spectra
of complex 7 with different excitation wavelengths (Figure S8),
both in diluted CH2Cl2 solutions at 77 K. This material is available
free of charge via the Internet at http://pubs.acs.org.
IC701298Z
9930 Inorganic Chemistry, Vol. 46, No. 23, 2007