Systematic Study on Sensing Capability of Gold(I) Pyrazolate Complex for Vapochromic Chemosensors of Ethanol Vapors

Abstract

Modified gold complexes as dinuclear adducts with silver bridge ions, clusters with other metal ions, and bimetallic sandwiches have shown better sensing capabilities for vapochromic chemosensing of organic vapors than its unmodified structure. Herein, a simple gold(I) complex, synthesized from 4-(3,5-dimethoxybenzyl)-3,5-dimethyl pyrazole ligand, have been shown to have higher sensing capability toward ethanol (EtOH) vapors. Such sensing capability can be possibly achieved when EtOH vapors have enough time to diffuse to the main sensing sites of the sensor. Thus, 80 to 160 µL (with 20 µL increment) of EtOH vapors were exposed to the synthesized gold(I) pyrazolate complex at varied distances of 2.75, 11 and 22 cm for 15 minutes. The complex displayed its sensing capability by quenching at its emission intensity of 600 nm up to 80%, which suggests the possible interaction of the EtOH vapors with the inner sensing site originated from the Au(I)–Au(I) interaction of the complex where it is possible to breakdown the light-emitting capability. Prior to this interaction, there was only a slight blue-shifting of 9 nm away from its emission intensity by the binding of EtOH vapors to the methoxy of benzene ring hence only demonstrating weak sensing capability. These results indicated that sensing capability as shown by the quenching phenomenon at the emission intensity of gold(I) complex is dependent on diffusion time of EtOH vapors.