Temperature-dependent halogen⋯halogen synthon crossover in coordination compounds

Abstract

The temperature-dependent Br⋯Br halogen⋯halogen synthon crossover in two coordination compounds of HgI₂ and N-(3-bromophenyl)pyridine-3-carboxamide flexible ligand, L^3Br-nic, have been investigated. The results show that when starting with equivalent amounts of the reagents and when the reaction was carried out at room temperature, a 1 : 2 adduct of HgI₂ : 2L^3Br-nic, complex 1, was generated, whereas when the reaction temperature was fixed at −4 °C, a 1 : 1 adduct, complex 2, was obtained. In 1, individual molecules form a wave-like chain through type II Br⋯Br halogen bonding interactions, while the Br⋯Br interactions generate dimeric units in 2.