Raman Detected Sensing of Volatile Organic Compounds by Vapochromic Cu[AuX2(CN)2]2 (X = Cl, Br) Coordination Polymer Materials

Abstract

Two vapochromic coordination polymers Cu[AuX2(CN)2]2 (X = Cl, 1; X = Br, 2) were prepared and spectroscopically characterized. Exposure of these solid materials to the volatile organic compounds dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, 1,4-dioxane, and ethylene glycol (glycol) resulted in distinct color, and IR and Raman changes. The thermal stability of the analyte-bound materials was assessed by thermogravimetric analysis. Single-crystal structures of Cu(analyte)4[AuX2(CN)2]2 (analyte = DMF, DMSO; X = Cl, Br) revealed an isostructural set of 1-D coordination polymer chains, where the analyte molecules were equatorially O-bound to the Cu(II) centers while axially bound [AuX2(CN)2]− units bridged these Cu(II) centers, while Cu(glycol)4[AuBr2(CN)2]2 is molecular, with monodentate glycol units. The structure of Cu2(OH2)4[AuCl2(CN)2]4·4dioxane is a 2-D coordination polymer network with H2O-bridged Cu(II) centers and dioxane units hydrogen bonded between the 2-D sheets. The intense Raman ...