Structures and Luminescence Properties of Cyclometalated Dinuclear Platinum(II) Complexes Bridged by Pyridinethiolate Ions

Abstract

A series of cyclometalated dinuclear platinum(II) complexes bridged by pyridine-2-thiolate (pyt) ions, [Pt2(L)2(pyt)2] (HL = 2-(p-tolyl)pyridine (Hptpy), 2-(2-thienyl)pyridine (Hthpy), or benzo[h]quinoline (Hbzqn)), as well as their two-electron-oxidized dinuclear platinum(III) complexes, [Pt2Cl2(L)2(pyt)2], have been synthesized and characterized. The structures and luminescence properties have been investigated by comparing them with those of the corresponding 2-phenylpyridinato (ppy) complex. All divalent complexes have similar dinuclear frameworks, with short Pt···Pt distances (ca. 2.85 Å), and exhibit similar intense luminescence from the triplet metal–metal-to-ligand charge-transfer (3MMLCT) state in glassy solutions. However, they provide different luminescence features reflecting their dynamic behaviors in fluid solutions and their intermolecular interactions in the solid state. [Pt2(bzqn)2(pyt)2] containing fused aromatic rings exhibits the most sensitive features to the environment, i.e., it shows the most red-shifted luminescence spectrum in the solid state due to the intermolecular π–π interaction. However, in fluid solution, it provides very weak luminescence based on a rapid nonradiative deactivation mainly caused by the fluctuation of the intramolecular π–π repulsion between the ligands. [Pt2(ptpy)2(pyt)2], on the other hand, is the most stable luminophore, which always exhibits intense luminescence with an almost constant emission maximum independent of its temperature and state.

N-Assisted CPh–H Activation in 3,8-Dinitro-6-phenylphenanthridine. New C,N-Cyclometalated Compounds of Platinum(II): Synthesis, Structure, and Luminescence Studies

“…Compounds 3-5 show one υ Pt-Cl absorption at ca. 277 cm -1 , which is consistent with a terminal Pt-Cl bond trans to C. Compound 5 exhibits one absorption at 2218 cm -1 assignable to υ C≡NR , of a terminal C≡N t Bu, 30,38,43,50,51 since it appears shifted to higher frequencies with respect to the free ligand (2125 cm -1 56 2,2'-bipyridine, 57 2-(2'-thienyl)pyridine 58 ).…”

Half-Lantern Pt(II) and Pt(III) Complexes. New Cyclometalated Platinum Derivatives

“…Oxidation of C, N-cyclometalated Pt 2 (II,II) compounds do not lead to mixed-valence oligomeric species but rather to discrete Pt 2 (III,III) dimers [13] (Scheme 2c). By way of example, complexes [{Pt(bzq)(μ-C 7 H 4 NYS-κN,S)} 2 ] (Y = S, O) undergo two-center, two-electron oxidation in their reactions with halogens (X 2 = Cl, Br, I) [15,16] to give [{Pt(bzq)(μ-C 7 H 4 NYS-κN,S)X} 2 ] (Y = S, O; X = Cl, Br, I) which show Pt−Pt distances (2.63 to 2.68 Å), about 10% shorter than their starting complexes (2.91, 2.97 Å).…”

“…The half-lantern Pt 2 (III,III)X 2 compounds (X = Cl, Br, I) seem to be quite stable, being the final products of diverse kinds of reactions. The dichloro compounds [Pt 2 (C^N) 2 (µ-pyt) 2 Cl 2 ] (Hpyt = pyridine-2-thiol, HC^N = 2-phenylpyridine (Hppy), 2-(p-tolyl)pyridine (Hptpy), 2-(2-thienyl)pyridine (Hthpy), benzo[h]quinolone (Hbzq)) were the final products of the reactions between (NBu 4 )[Pt(C^N)Cl 2 ] and Hpyt in the absence of a base [13] , X = Cl, Br, SCN, or py) [27,28], which exhibit red luminescence in an alcohol glass or in solid state at low temperature and [{Pt(κ 2 -As,C-C 6 H 3 -5-CHMe 2 -2-AsPh 2 ) 2 X} 2 ] (X = Cl, Br, I, CN) [29] that emit in the visible to NIR region even at room temperature.…”

Strong red emissions induced by Pt–Pt interactions in binuclear cycloplatinated(II) complexes containing bridging diphosphines

“…The Pt…Pt and π…π interactions become significantly weaker or completely vanish in a solvent . Herein, the role of linker ancillary ligands becomes important because the structural rigidity is protected in order to achieve a stable 3 MMLCT emission character even in a solvent …”