Dimetal linked open frameworks: [(CH3)(4)N](2)(Ag-2,Cu-2)Ge4S10

Synthetic and X-ray structural details, optical and vibrational spectroscopic, and thermal properties of the materials [(CH3)(4)N](2)M(2)Ge(4)S(10) (where M = Cu, Ag), are described for the first time. Rietveld PXRD full-profile structure refinements of [(CH3)(4)N](2)M(2)Ge(4)S(10) reveal a novel open-framework architecture in which dimetal M(2)(2+) and adamantanoid Ge4S104- building blocks are alternately substituted into the tetrahedral Zn2+ and S2- sites of a zinc blende lattice, all linked together by [Ge(mu-S)](2)M-M[(mu-S)Ge](2) metal-metal bonded bridging units. The metal-metal distances in the S(2)M-MS(2) ''twisted I'' dihedral unit are 2.761 Angstrom (Ag) and 2.409 Angstrom (Cu). These internuclear separations are shorter than the bulk metals themselves (2.89 Angstrom, Ag; 2.54 Angstrom, Cu). This implies that the adamantanoid Ge4S104--based open-framework structure is held together by d(10)-d(11) M(+)-M(+) metal-metal bonds. FT-Raman provides a direct probe of this interaction. Dimetal-framework breathing vibrational modes are observed around 38 cm(-1) for M = Ag and 55 cm(-1) for M = Cu. In situ VT-PXRD analysis demonstrates that [(CH3)(4)N]2Ag2Ge4S10 retains its structural integrity upon exposure to air after in vacuo heating above the [(CH3)(4)N](+) loss temperature. It seems likely that the disilver connection of adamantanoid Ge4S104- building blocks confers thermal stability upon the framework.