Assembled metal complexes of platinum(ii) and gold(i) ions often exhibit a characteristic color and intense luminescence based on electronic metal±metal interactions. Such complexes have recently attracted particular interest as sensor materials. [1] Herein, we report a new dinuclear platinum(ii) complex, syn-[Pt 2 (bpy) 2 (pyt) 2 ][PF 6 ] 2 (bpy ¼ 2,2'-bipyridine, pyt ¼ pyridine-2-thiolate ion), which exhibits a remarkable change in its luminescence in the presence of organic vapors such as acetonitrile or ethanol.Dark-red polyhedral crystals of syn-[Pt 2 (bpy) 2 (pyt) 2 ]-[PF 6 ] 2 ¥CH 3 CN were isolated from an acetonitrile/ethanol solution as the minor component of two geometrical isomers containing the [Pt 2 (bpy) 2 (pyt) 2 ] 2þ ion. The syn isomer has a head-to-head configuration of two bridging pyridine-2-thiolate ions ( Figure 1), with the platinum ions adopting different coordination environments: Pt1 is bonded to four nitrogen atoms, whereas Pt2 has N 2 S 2 coordination. This arrangement is in contrast to the anti isomer, which has a head-to-tail configuration (Figure 2), and is obtained as orange needlelike crystals. The Pt¥¥¥Pt separations for the syn-and anti isomers are 2.923(1) and 2.997(1) ä, respectively. These separations are amongst the shortest Pt¥¥¥Pt interactions observed in divalent platinum complexes. [2] Similar dinuclear complexes have been reported by Che an co-workers. [3] Crystals of the anti isomer exhibit very intense orange luminescence (l max ¼ 603 nm), even at room temperature (Figure 3 a). On the basis of the spectral profile and the emission lifetime (t ¼ 240 ns), the luminescene can be assigned as emission from the triplet metal±metal-to-ligand charge-transfer state, which has been observed in diimineplatinum(ii) complexes with short Pt¥¥¥Pt separations. [4] The emission state is thought to also include a contribution from the sulfur orbitals of the pyridine-2-thiolate ligands. [3a, 5] Crystals of the syn isomer are initially dark-red in appearance, but appear to become lighter in color upon standing in air for several hours at room temperatue ( Figure 4). Luminescence spectroscopy of these materials shows the generation of a concomitant emission (Figure 3 b and c). It is noteworthy that the luminescent light-red form reverts back to the nonemissive darker immediately upon exposure to acetonitrile or ethanol vapor, formwhich could be monitored COMMUNICATIONS Figure 1. Single-crystal X-ray structure of the syn isomer. Figure 2. Single-crystal X-ray structure of the anti isomer.Figure 3. Luminescence spectra at room temperature for a) the anti isomer, b) the light-red (desolvated) form of the syn isomer, and c) the dark-red (solvated) form of the syn isomer.

Dicyano(4,4′-dicarboxy-2,2′-bipyridine)platinum(II) forms pH-dependent polymorphs of various colors and displays outstanding vapochromism followed by luminescence changes upon exposure to certain organic vapors. The high sensitivity of the complex to vapor and pH is related to its three-dimensional network structure, which includes large cavities formed by hydrogen bonds and Pt···Pt interactions.

The neutral square-planar complexes [Pt(RNH2)2(NHCO(t)Bu)2] (R = H, 1; Et, 2) and [Pt(DACH)(NHCO(t)Bu)2] (DACH = 1,2-diaminocyclohexane, 3) act as metalloligands and make bonds to closed-shell Tl(I) ions to afford one- and two-dimensional platinum-thallium oligomers or polymers based on heterobimetallic backbones. A series of heteronuclear platinum(II)-thallium(I) complexes have been synthesized and structurally characterized. The structures of the Pt-Tl compounds resulted from [Pt(RNH2)2(NHCO(t)Bu)2] and TlX [X = NO3(-), ClO4(-), PF6(-), and Cp2Fe(CO2)2(2-)] are dependent on both counteranions and the amine substituents. The compounds [Pt(NH3)2(NHCO(t)Bu)2Tl]X (X = NO3(-), 8; ClO4(-), 9) adopt one-dimensional zigzag chain structures consisting of repeatedly stacked [Pt(NH3)2(NHCO(t)Bu)2Tl]+ units, whereas [{Pt(NH3)2(NHCO(t)Bu)2}2Tl2]X2 (X = PF6(-), 10) consists of a helical chain. Compound 3 reacts with Tl+ to give [{Pt(DACH)(NHCO(t)Bu)2}2Tl](NO3) x [Pt(DACH)(NHCO(t)Bu)2] x 3 H2O (14) and one-dimensional polymeric [{Pt(DACH)(NHCO(t)Bu)2}2Tl2]X2 (X = ClO4(-), 15; PF6(-), 16). Reactions of [Pt(DACH)(NHCOCH3)2] with Tl+ ions afford one-dimensional coordination polymers [{Pt(DACH)(NHCOCH3)2}2Tl2]X2 (X = NO3(-), 17; ClO4(-), 18; PF6(-), 19). The polymeric [{Pt(DACH)(NHCOR')2}2Tl2]2+ (R = CH3, (t)Bu) complexes adopt helical structures, which are generated around the crystallographic 2(1) screw axis. The distance between the coils corresponds to the unit cell length, which ranges from 22.58 to 22.68 A. The platinum-thallium bond distances fall in a narrow range around 3.0 A. The complexes derived from [Pt(NH3)2(NHCO(t)Bu)2] are luminescent at 77 K. The trinuclear complexes [{Pt(RNH2)(NHCO(t)Bu)2}2Tl]+ do not emit at room temperature but are emissive at 77 K, whereas the polymeric platinum-thallium complexes containing 1,2-diaminocyclohexane are intensively luminescent at both room temperature and 77 K. The color variations are interesting; 15 exhibits intense yellow-green, 16 exhibits green, and 17-19 exhibit blue luminescence. The presence of bonding between platinum and thallium is supported by the short metal-metal separations and the strong low-energy luminescence of these compounds in their solid states.

No abstract