Role of halogen atoms in the formation of one-dimensional Cu(I) coordination polymers based on 2-amino-5-halopyrimidine

The reactions of CuCl and CuBr with 2-amino-5-chloropyrimidine (L-Cl), 2-amino-5-bromopyrimidine (L-Br) and 2-amino-5-iodopyrimidine (L-I) in aqueous solutions of HCl and HBr afforded [CuCl2(HL-I) · H2O]n, 1, [CuBr2(HL-I) · H2O]n, 2, [CuCl2(HL-Br) · H2O]n, 3, [CuBr2(HL-Br) · H2O]n, 4, and [CuCl2(HL-Cl) · H2O)n, 5. Complexes 1-5 show 1D zigzag chains due to the zigzag arrangements of the bridging halide atoms. While the iodo atoms of the pyrimidyl rings in 1 and 2 are trans to the bridging halide anions and the Cu(I) ions are in a linear array, the chloro and bromo atoms of the pyrimidyl rings in 3-5 are cis to the bridging halide anions and the Cu(I) ions are in a zigzag fashion. The structural difference can most probably be ascribed to the identity of the halogen atoms. X-ray crystallographic study and Hirshfeld surface analysis are invoked to investigate the structural differences.181