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.

Emission from a cationic cyclometalated iridium(III) complex, Δ- or Λ-[Ir(ppy)2(dmbpy)]+ (Hppy: 2-phenylpyridine and dmbpy: 4,4′-dimethyl-2,2′-bipyridine), adsorbed on a colloidal saponite clay was quenched stereoselectively by chiral [Ru(acac)3] (acac: acetylacetonato) in a solution at the overall selectivity factor of KSVo(Δ–Δ or Λ–Λ)/KSVo(Δ–Λ) = 1.84 in favor of the pseudo-enantiomeric pair between the emitter and the quencher.

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To make a molecular design of efficient indoline dyes, fluorescence lifetimes should be longer than ca. 0.8 ns in chloroform, in addition to suitable HOMO and LUMO levels and bathochromic UV-vis absorption bands.Indoline dyes are one of the most efficient organic sensitizers in dye-sensitized solar cells (DSSCs). D149 was reported to exhibit a high conversion efficiency of 6.1% on titanium oxide. 1 Since then, much effort has been made to obtain more efficient indoline dyes by changing the anchor moieties such as cyanoacrylic acid, 2,3 single, 4,5 double, 6-9 and triple rhodanines. 10 The double rhodanine dyes D205, 6 DN319, 7 and DN315, 8 have been reported to exhibit higher efficiency than D149. As the acceptor anchor moieties affect the energy levels of indoline dyes, it is important to check the HOMO and LUMO levels. The relationship between the HOMO level and maximum incident photon-to-current efficiency (IPCE) of indoline dyes has been reported. 11 As the HOMO level of double rhodanine indoline dyes is close to the I À /I 3 À redox level, the stabilization of the HOMO level and positive shi of the oxidation potential (E ox ), is required. To prepare new indoline dyes, we made molecular designs of pyridone acetic acid derivatives. These novel indoline dyes, GU113 and GU114, were predicted by the DFT calculations to show stabilized HOMO levels, and similar HOMO-LUMO gaps to D149. Unfortunately, these dyes did not act as sensitizers due to reduced electron injection abilities from the excited state to the conduction band of zinc oxide. To obtain efficient indoline dyes, an additional parameter of electron injection, besides the DFT calculations, is proposed in this report. Novel indoline dyes GU113 and GU114 were synthesized as shown in Scheme 1. Ethyl alkanoylacetoacetates 1, ethyl cyanoacetate (2), and glycine ethyl ester hydrochloride (3) were allowed to react in the presence of piperidine to give ethyl pyridone acetates 4, whose ester group was hydrolyzed to afford pyridone acetic acids 5. These compounds were allowed to react with aldehyde 6 to provide GU113 and GU114. D149 was also prepared as a reference compound.The structure of GU113 was optimized at the B3LYP/3-21G level. Fig. 1 indicates that the double bond of GU113 at the 7-position is in the Z conguration due to steric repulsion between the hydrogen atom at the 8-position on the indoline ring, and the methyl group on the pyridone ring. The indoline chromophore is almost planar, with the dihedral angle between the indoline and pyridone moiety q 1 being 0.5 . Meanwhile, the uorenyl moiety can act as steric hindrance to prevent Scheme 1 Reagents and conditions: (i) 3 (20.0 mmol), TEA (29.7 mmol), 5 min, EtOH (2 mL), then 1 (20.0 mmol), 2 (20.0 mmol), piperidine (6.1 mmol), reflux, 9 h, (ii) 4 (1.8 mmol), AcOH-HCl (2 : 1, 3 mL), reflux, 3 h, (iii) 5 (0.70 mmol), 6 (0.86 mmol), EtOH (10 mL), rt, 1 day.

We synthesized a thiosemicarbazone-functionalized flavin (Fl-(H)TSC: 2-[2- (3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)ethylidene]-hydrazinecarbothioamide) and its Pt(II) complex [Pt(Fl-TSC) 2 ], and characterized it using X-ray diffraction, UV-visible absorption and luminescence spectroscopy. X-ray structural analysis for [Pt(Fl-TSC) 2 ] revealed that the structure 10 of the isoalloxazine part was almost the same as that in lumiflavin (7,8,10-trimethylisoalloxazine), and the thiosemicarbazone moiety acted as a bidentate ligand to form a PtS 2 N 2 planar conformation. UV-visible absorption and luminescence spectra of these compounds were very similar to those of riboflavin, but the emission intensity and the lifetime decreased considerably.