Vapochromic copper(I) pyrazolate complex materials for phosphorescent chemosensors of ethanol

Abstract

Here chemosensor materials of trinuclear copper(I) pyrazolate complexes have been successfully synthesized and isolated using two types of 3,5-dimethyl and 4-(3,5-dimethoxybenzyl)-3,5-dimethyl pyrazole ligands. Upon excitation at 280 nm, the resulting trinuclear 3,5-dimethyl copper(I) pyrazolate complex (complex A) and trinuclear 4-(3,5-dimethoxybenzyl) copper(I) pyrazolate complex (complex B) showed emission bands centered at 590 and 604 nm, respectively. These results were in good agreement with their greenish-white powders and it is characteristic of phosphorescent metal complexes from the weak Cu(I)-Cu(I) metallophilic interaction. Upon direct or stepwise exposure to ethanol vapor with series of concentrations (12.5, 25, 50, 100, 150 and 200 μL in 22 mg of chemosensor), the emission of chemosensor complex A was not shifted even after 1 d. Interestingly, chemosensor complex B showed gradually changes in both emission band with shifting from 602 to 552 nm and color with changing from orange to green under Ultra-violet (UV) hand lamp (254 nm) at the dark room due to the attachment of benzyl ring to the pyrazole ligand. This positive response for chemosensor complex B was reversible; hence, this optical phosphorescent material can be used for developing vapochromic sensors of ethanol.