Vapor-Induced Luminescence Switching in Crystals of theSynIsomer of a Dinuclear (Bipyridine)platinum(II) Complex Bridged with Pyridine-2-Thiolate Ions

Abstract

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.

Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions

“…We 70 previously reported the one-step synthesis of homodinuclear platinum complexes syn-and anti- [PtPt] by the reaction of [PtCl 2 (bpy)] and Hpyt. 3 The syn and anti geometrical isomers were produced as a mixture and the isolation of the syn isomer of the minor component was troublesome in this method. For the 75 regioselective synthesis of the syn isomer, a stepwise complexation as shown in Scheme 2 should be favourable, in particular, it should be a good way to prepare heterodinuclear complexes.…”

“…The hexafluorophosphate salt of syn- [PtPt] exhibits an interesting vapour-induced colour change between dark-red and light-red on interactions from the dimer to the dimer-of-dimer structure could lower the energy of the metal-metal-to-ligand charge transfer (MMLCT) transition. 3 Thus, we proposed that the vapochromic behaviour for this system would occur by the change of the Pt···Pt electronic interactions between the dinuclear complexes. To 5 explore the electronic effects of the metal-metal interactions on the vapochromic behaviour, it would be effective to introduce different metal ions into the same dinuclear motif.…”

“…We previously reported a homometallic dinuclear platinum(II) complex, [Pt 2 (-pyt) 2 (bpy) 2 ] 2+ (pyt = pyridine-2-40 thiolate, bpy = 2,2′-bipyridine), 3 which has two geometrical isomers, the syn-and anti-isomers (syn- [PtPt] and anti- [PtPt]), corresponding to the case of M = Pt 2+ in Scheme 1. The hexafluorophosphate salt of syn- [PtPt] exhibits an interesting vapour-induced colour change between dark-red and light-red on interactions from the dimer to the dimer-of-dimer structure could lower the energy of the metal-metal-to-ligand charge transfer (MMLCT) transition.…”

“…3 As shown in Fig. 1a, the Pd 2+ ion in syn- [PdPt] was surrounded by four nitrogen atoms while the Pt 2+ ion was coordinated by two nitrogen atoms and two sulphur atoms.…”

Shape‐Memory Platinum(II) Complexes: Intelligent Vapor‐History Sensor with ON–OFF Switching Function

“…In particular, vapochromic materials that exhibit color changes upon adsorption/desorption of chemical vapors have attracted considerable attention because of their potential application for sensor devices for detecting vapor from volatile organic compounds (VOCs) which are widely used in our living environments. [2][3][4][5][6][7] Among the known vapochromic materials, square-planar Pt(II) complexes have been extensively studied in recent decades because they are well-known to exhibit color and luminescence changes based on a structural transformation involving modification of the intermolecular metallophilic interactions. [2][3][4][5][6] The vapor-sensing functionalities of most of the vapochromic materials reported so far are usually based on the color difference between the adsorbed and desorbed forms, as shown in Scheme 1(a).…”