Ni(II)/Cu(I) based coordination polymers with heterofunctional ligands integrating pyridine and pyrimidinethione structural motifs

Abstract

Two coordination polymers with the heterofunctional ligand 4-PPT (4-(pyridin-4-yl)pyrimidine-2-thiol), {[Ni(4-PPT)2]·2(DMF)}n (1) and {[Cu2(4-PPT)2]·2(DMF)}n (2), have been isolated by reaction with Ni(OAc)2 and CuBr2, respectively. 1 shows a two-dimensional (2-D) layered structure with a 4-connected sql topology wherein the 4-PPT ligand exhibits a uniform μ2-1, κS κN(pyrimidine): 2, κN(pyridine) bridging mode. 2 also features an sql net based on a unique CuI4S4 cluster in which the 4-PPT ligand adopts two kinds of coordination modes, viz. μ3-1, κN(pyrimidine): 2,3, κS and μ4-1, κN(pyrimidine): 2,3, κS: 4, κN(pyridine). For comparison, the reaction of CuBr2 with 3-PPT (4-(pyridin-3-yl)pyrimidine-2-thiol, an isomer of 4-PPT) under the same conditions was also examined, which yielded a 2-D Cu(I)-based coordination polymer with the 63-hcb topology, [CuBr(3-ppds)]n (3) (3-ppds=di(4-(pyridin-3-yl)pyrimidin-2-yl)disulfide). In 3,3-ppds was in situ generated from 3-PPTvia an S–S oxidative coupling reaction, concurrent with in situ reduction CuII–CuI. UV–Vis diffuse reflectance and luminescence spectra have been measured for 1 and 2 in order to compare their photophysical properties.