Temperature-dependent crystal structure and fluorescence properties of a tetranuclear copper(I) cluster from in situ [2 + 3] cycloaddition synthesis

Abstract

Hydrothermal reaction of CuSO₄·7H₂O and NaN₃ with 2-cyanothiophene in aqueous ethanol yielded a novel tetranuclear copper(I) polymer, {[Cu₄(tptz)₄]·0.5(C₂H₆O)}_n (1) (Htptz = 5-(thiophen-2-yl)-1H-tetrazole). The tptz ligand in the complex was generated through an in situ [2 + 3] cycloaddition reaction involving the cyano groups of the precursor 2-cyanothiophene. In a rare example, three different geometries of Cu(I) cations, namely the linear, triangle, and tetrahedron geometries of Cu(I) centers, are created and linked by Htptz ligands into a 1-D ladder structure. Additionally, 1 exhibits strong blue fluorescence (with λ = 467 nm) at room temperature in the solid state.

Keywords:

• Tetrazolate
• in situ synthesis
• fluorescence
• copper(I) complex