Vapochromic Behaviour of M[Au(CN)2]2-Based Coordination Polymers (M = Co, Ni)

A series of M[Au(CN)(2)](2)(analyte)(x) coordination polymers (M = Co, Ni; analyte = dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), pyridine; x = 2 or 4) was prepared and characterized. Addition of analyte vapours to solid M(mu-OH2)[Au(CN)(2)](2) yielded visible vapochromic responses for M = Co but not M = Ni; the IR nu(CN) spectral region changed in every case. A single crystal structure of Zn[Au(CN)(2)](2)(DMSO)(2) revealed a corrugated 2-D layer structure with cis-DMSO units. Reacting a Ni(II) salt and K[Au(CN)(2)] in DMSO yielded the isostructural Ni[Au(CN)(2)](2)(DMSO)(2) product. Co[Au(CN)(2)](2)(DMSO)(2) and M[Au(CN)(2)](2)(DMF)(2) (M = Co, Ni) complexes have flat 2-D square-grid layer structures with trans-bound DMSO or DMF units; they are formed via vapour absorption by solid M(mu-OH2)[Au(CN)(2)](2) and from DMSO or DMF solution synthesis. Co[Au(CN)(2)](2)(pyridine)(4) is generated via vapour absorption by Co(mu-OH2)[Au(CN)(2)](2); the analogous Ni complex is synthesized by immersion of Ni(mu-OH2)[Au(CN)(2)](2) in 4% aqueous pyridine. Similar immersion of Co(mu-OH2)[Au(CN)(2)](2) yielded Co[Au(CN)(2)](2)(pyridine)(2), which has a flat 2-D square-grid structure with trans-pyridine units. Absorption of pyridine vapour by solid Ni(mu-OH2)[Au(CN)(2)](2) was incomplete, generating a mixture of pyridine-bound complexes. Analyte-free Co[Au(CN)(2)](2) was prepared by dehydration of Co(mu-OH2)[Au(CN)(2)](2) at 145 degrees C; it has a 3-D diamondoid-type structure and absorbs DMSO, DMF and pyridine to give the same materials as by vapour absorption from the hydrate.