Abstract
The effect of heterocyclic metalated and bridging ligands on the optical and electrochemical properties of [Pt(C^N)(μ-N^S)]2 complexes ((C^N)− and (N^S)− are the deprotonated forms of 1-phenylpyrazole, 2-tolylpyridine, benzo[h]quinoline, 2-phenylbenzothiazole and 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptopyridine) is studied by 1H NMR, electronic absorption, and emission spectroscopy, as well as by voltammetry. The long-wavelength spin-allowed (415–540 nm) absorption bands of the complexes are attributed to the metal-metal-to-ligand charge transfer (MMLCT) optical transitions. It is shown that the interaction of the dZ2 and π(C^N*) orbitals of two {Pt(C^N)} fragments of binuclear complexes leads to a cathodic shift (0.5–1.0 V) of their metal-centered oxidation potential and to an anodic shift (0.1–0.2 V) of their ligand-centered reduction potential with respect to [Pt(C^N)En]+ complexes. The luminescence of binuclear complexes in solutions at room temperature is assigned to the spin-forbidden MMLCT transition. It is shown that, in frozen (77 K) solutions, in addition to the MMLCT optical transitions, spin-forbidden radiative processes occur from the intraligand (π(C^N)−π(C^N)*) and metal-to-ligand charge transfer (dPt−π(C^N)*) excited states.
Published Version
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