Copper(i) 5-phenylpyrimidine-2-thiolate complexes showing unique optical properties and high visible light-directed catalytic performance?

Dalton Transactions Pub Date: 2016-10-10 DOI: 10.1039/C6DT03721F

Abstract

Solvothermal reactions of 5-phenylpyrimidine-2-thiol (5-phpymtH) with equimolar CuBr afforded one hexanuclear cluster [Cu6(μ3-5-phpymt)6] (1) along with a tetranuclear by-product [{(Cu2Br)(μ-5-phpymtH)}(μ3-5-phpymt)]2 (2). A two dimensional (2D) polymer [Cu4(μ5-5-phpymt)2(μ-Br)2]n (3) was isolated from the reaction of 5-phpymtH with two equiv. of CuBr. Analogous reactions of 5-phpymtH with one or four equiv. of CuI produced one tetranuclear cluster [{Cu2(μ-5-phpymtH)(μ-5-phpymt)}(μ3-I)]2 (4) and one 2D polymer [Cu6I2(μ4-I)2(μ4-5-phpymt)2]n (5). Compound 1 possesses a water-wheel-shaped hexameric structure. Compound 2 has an H-shaped tetrameric structure. Compound 3 possesses a 2D network in which unique 1D [Cu8(μ-Br)2(μ5-5-phpymt)4]n chains are connected by μ-Br? ions. Compound 4 has another tetrameric structure in which two {Cu2(μ-5-phpymtH)2(μ-5-phpymt)} fragments are linked by a pair of μ3-I? ions. Compound 5 contains another 2D network in which hexanuclear {Cu6I2(μ4-I)2} units are linked by μ4-5-phpymt bridges. The 5-phpymt ligand shows four coordination modes: μ–κ1(S)–κ1(N) (4), μ3–κ2(S)–κ1(N) (1 and 2), μ4–κ1(N)–κ2(S)–κ1(N′) (5) and μ5–κ1(N)–κ3(S)–κ1(N′) (3). Complex 1 shows strong solvatochromic behaviour and displays reversible luminescence switching upon alternate addition of CF3COOH and Et3N into its CHCl3 solution. Complexes 1–5 exhibit a high photocatalytic activity towards the aerobic oxidative hydroxylation of arylboronic acids to phenols under visible light irradiation. Catalyst 5 can be reused in several cycles without any obvious decay of the catalytic efficiency. These results offer an interesting insight into how the CuX/5-phpymtH molar ratios and X? ions exert great impacts on the coordination modes of the 5-phpymt? ligand, the structures of the final complexes, and the luminescence and catalytic properties.

Graphical abstract: Copper(i) 5-phenylpyrimidine-2-thiolate complexes showing unique optical properties and high visible light-directed catalytic performance
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