Synthesis and structures of copper(II), copper(I,II) and copper(I) complexes with 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine. Luminescence of copper(I) complexes

Abstract

A series of Cu(II), Cu(I,II) and Cu(I) halide complexes, [CuL2Br]2[Cu2Br6], [CuL2Br2], [Cu2L2Br3]·EtOH, [Cu2L2Br3]·CHCl3, [Cu2L2Cl3]·MeCN, [Cu2L2Cl3]·CHCl3, [CuLCl], [CuLBr] and [Cu2L2I2] with 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) have been synthesized. Copper(II) compounds, [CuL2Br]2[Cu2Br6] and [CuL2Br2], were obtained by the reactions of CuBr2 with L in the Cu:L=1:1 and 1:2molar ratios, respectively, in EtOH solutions at room temperature. In the structure of [CuL2Br2], the double intermolecular lone pair– interactions were observed between N(piperidine) atom and π-deficient pyrimidine ring. Dinuclear mixed-valence copper(I,II) bromide compounds, [Cu2L2Br3]·EtOH and [Cu2L2Br3]·CHCl3, were prepared (i) by the reaction of CuBr2 and L in a 1:1molar ratio upon heating in EtOH either CHCl3/MeCN solutions, and (ii) by recrystallizing [CuL2Br]2[Cu2Br6] from CHCl3/MeCN mixture. Their analogs, mixed-valence copper(I,II) chloride compounds, [Cu2L2Cl3]·MeCN and [Cu2L2Cl3]·CHCl3, were prepared by reacting the complex [CuL2Cl2] with CuCl in MeCN/CHCl3 mixtures (various v/v ratios of the solvents). The frozen solutions of copper(II) and copper(I,II) complexes in CHCl3 were studied by EPR spectroscopy at 77K. These data revealed that mixed valence compounds are type I systems. In the structures of [Cu2L2Br3]·CHCl3 and [Cu2L2Cl3]·CHCl3, lone pair–π interactions were observed between Cl atom of chloroform solvent molecule and the phenyl group. The Cu(I) complexes, [CuLCl], [CuLBr] and [Cu2L2I2], were obtained by the reactions of CuHal (Hal=Cl, Br, I) and L in a 1:1molar ratio in MeCN solutions. The complex [Cu2L2I2] has dinuclear structure with rather short Cu–Cu distance, 2.59Å, within {Cu(μ-I)2Cu} central unit, while its chloride and bromide analogs seem to be mononuclear compounds. The complexes [CuLCl], [CuLBr] and [Cu2L2I2] were found to show bright yellow luminescence in the solid state at room temperature. The relative intensity of emission increases across the series: [CuLCl]<[CuLBr]<[Cu2L2I2]. At 77K, there is a noticeable red shift (ca. 20nm) in emission for [Cu2L2I2].