In situalkylation of N-heterocycles in organic templated cuprous halides

Abstract

Five new cuprous halides formulated as [etpy][Cu₃I₄] 1, [mepy][Cu₂Br₃] 2, [mepy][Cu₂I₃] 3 [dmebpp][Cu₇Br₉] 4 and [dmeDABCO]₄[Cu₈I₁₆] 5 (etpy = N-ethylpyridyl; mepy = N-methylpyridyl; dmebpp = N,N′-dimethyl-1,3-bis(4-pyridyl)propane; dmeDABCO = N,N′-dimethyl-1,4-diazabicyclo-[2.2.2]octane) have been prepared by solvothermal reactions of a copper source, halides and N-heterocyclic ligands in alcoholic solution. 1 contains an unprecedented trigonal two-dimensional cuprous halide layer Cu₃I₄⁻ constructed from trimeric Cu₃I₈ units via sharing peripheral μ₃-iodines; isostructural 2 and 3 contain infinite Cu₂X₃⁻ chains in which the copper atoms are arranged into a ladder; 4 is composed of novel twofold helical cuprous halide chains Cu₇Br₉²⁻ built up by CuBr₄ and CuBr₃; 5 contains an infinite edge-sharing tetrahedral chain with a periodic sequence of eight CuI₄ tetrahedra. In situ alkylation reactions of N-heterocycles with alcohols generated organic cationic templates, which played an important role in the control of the structures of anionic cuprous halides. A possible alkylation mechanism of N-heterocycles in the system has been proposed. The fluorescence properties of 1 and 4 were investigated. Time-dependent density functional theory (TD-DFT) calculations were carried out on the excited electronic states of 1 in order to understand the emission mechanism.