Enantiomerism, diastereomerism and thermochromism in two Cu7I4 cluster-based coordination polymers

Abstract

Solvothermal reaction between CuI and 5-(3-pyridyl)tetrazole (HPTA) in CH₃CN and NH₃·H₂O/n-BuOH, afforded two kinds of Cu₇I₄ cluster-based coordination polymers 1 and 2, respectively. 1 is a racemic conglomerate of enantiomers crystallizing in the P6₃22 space group and 2 is a mesomer crystallizing in the Pc1 group. Both 1 and 2 show dual-channel emissions in which low-energy emission originates from a cluster-centered (CC) excited state while high-energy emission is attributed to an iodide-to-ligand charge transfer (XLCT)/metal-to-ligand charge transfer (MLCT) excited state. Of particular interest, 2 exhibits thermochromic luminescence originating from the combined effects of non-radiative transition and thermal deactivation of the XLCT excited state.