Raman detected sensing of volatile organic compounds by vapochromic cu[AuX(CN)] (X = Cl, Br) coordination polymer materials

Two vapochromic coordination polymers Cu[AuX(CN)] (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)[AuX(CN)] (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 [AuX(CN)] units bridged these Cu(II) centers, while Cu(glycol)[AuBr(CN)] is molecular, with monodentate glycol units. The structure of Cu(OH)[AuCl(CN)]·4dioxane is a 2-D coordination polymer network with HO-bridged Cu(II) centers and dioxane units hydrogen bonded between the 2-D sheets. The intense Raman v stretches for 1, 2, and their adducts form distinct, signature patterns. These "antenna" Raman v stretches are an effective means for sensing VOCs, and their characteristic patterns can be used to identify the VOC being detected.