Solid-state coordination chemistry of the Cu/triazolate/X system (X = F-, Cl-, Br-, I-, OH-, and SO42-)

Hydrothermal reactions of 1,2,4-triazole with the appropriate copper salt have provided eight structurally unique members of the Cu/triazolate/X system, with X = F-, Cl-, Br-, I-, OH-, and SO42-. The anionic components X of [Cu-3(trz)(4)(H2O)(3)]F-2 (1) and [Cu-6(trz)(4)Br]Cu4Br4(OH) (4) do not participate in the framework connectivity, acting as isolated charge-compensating counterions. In contrast, the anionic subunits X of [(CuCuI)-Cu-II(trz)Cl-2] (2), [Cu-6(trz)(4)Br-2] (3), [(CuCuI)-Cu-II(trz)Br-2] (5), [Cu-3(trz)I-2] (6), [(Cu6Cu2I)-Cu-II(trz)(6)(SO4)(3)(OH)(2)(H2O)] (8), and [Cu-4(trz)(3)]OH center dot 7.5H(2)O (9 center dot 7.5H(2)O) are intimately involved in the three-dimensional connectivities. The structure of [(CuCuI)-Cu-II(trz)(2)][(Cu3I4)-I-I] (7) is constructed from two independent substructures: a three-dimensional cationic {Cu-2(trz)(2)}(n)(n+) component and {Cu3I4}(n)(n-) chains. Curiously, four of the structures are mixed-valence CuI/CuII materials: 2, 5, 7, and 8. The only Cu-II species is 1, while 3, 4, 6, and 9, 7.5H2O exhibit exclusively Cu-I sites. The magnetic properties of the CuII species 1 and of the mixed-valence materials 5, 7, 8, and the previously reported [Cu-3(trz)(3)OH][Cu2Br4] have been studied. The temperature-dependent magnetic susceptibility of 1 conforms to a simple isotropic model above 13 K, while below this temperature, there is weak ferromagnetic ordering due to spin canting of the antiferromagnetically coupled trimer units. Compounds 5 and 7 exhibit magnetic properties consistent with a one-dimensional chain model. The magnetic data for 8 were fit over the temperature range 2-300 K using the molecular field approximation with J = 204 cm(-1), g = 2.25, and zJ' = -38 cm(-1). The magnetic properties of [Cu-3(trz)(3)OH][Cu2Br4] are similar to those of 8, as anticipated from the presence of similar triangular {Cu-3(trz)(3)(mu(3)-OH)}(2+) building blocks. The Cu-I species 3, 4, 6, and 9 as well as the previously reported [Cu-5(trz)(3)Cl-2] exhibit luminescence thermochromism. The spectra are characterized by broad emissions, long lifetimes, and significant Stokes' shifts, characteristic of phosphorescence.