Novel 1D Cu(I) coordination polymers formed by the combination of Cu(I) halides and 4-(2-pyridyl)pyrimidine

Abstract

Three novel 1D Cu(I) coordination polymers [Cu 4X 4(pprd) 2] n (X = Cl( 1), Br( 2) and I( 3); pprd = 4-(2-pyridyl)pyrimidine) were systematically synthesized by Cu(I) halides and the pprd ligand, and they have been characterized by X-ray, IR, and TG-DTA analyses. The molecular structure of complex 1 essentially resembles to that of complex 2. In complexes 1 and 2, four Cu(I) atoms are bridged by four Cl or Br anions to form an eight-membered Cu 4X 4 framework in the twist-chair form. Furthermore, the Cu 4X 4 frameworks are coordinated by the chelate and bridging sites of two pprd ligands to form a unique 1D two-stepped Cu(I) coordination polymer, in which two stairs are formed by the Cu 4X 4 core and two heteroaromatic planes of pprd. In the crystal packing structures, it is interesting that two heteroaromatic planes of pprd are stacking along the b-axis for complex 1 and the a-axis for complex 2. In contrast, four Cu(I) atoms in complex 3 are bridged by four I atoms to form a Cu 4I 4 stepped cubane tetramer. Additionally, the Cu 4I 4 stepped cubane cores are linked by the chelate and bridging sites of two pprd ligands to form an infinite 1D zigzag-chain Cu(I) coordination polymer. The thermal decomposition behaviors for Cu(I)–X/pprd complexes 1, 2 and 3 were determined by thermogravimetric analysis (TG-DTA). Although the thermal decomposition behaviors of complex 1 were unidentified, those of complexes 2 and 3 were assigned. The mass loss at the first stage of thermal decomposition for polymeric [Cu 4X 4(pprd) 2] n was identical to the formation of oligomeric [Cu 4X 4(pprd)] by the elimination of one pprd molecule. The mass loss at the next stage was decided to the formation of Cu 4X 4 by the elimination of another pprd molecule.