An imidazole-copper(I) metallacycle complex exhibiting thermochromic fluorescence.

In this paper, we firstly report the synthesis and structural characterization of a discrete coordination metallacycle complex, [CuI (bipy)] 2 (1). The x-ray diffraction structure, temperature-dependent electronic absorption, and photoluminescence spectra have been investigated. The solid-state fluorescence at variable temperatures shows that complex 1 exhibits an obvious thermochromic fluorescence. At low temperature, the dual fluorescence with peaks at 590 and 694 nm was observed. The emission color significantly changes from red at 77 K to yellow at 200 K and blue-green at 330 K. The thermochromic fluorescent molecular materials show great potential as temperature sensing.