Ligand-controlled mixed-valence copper rectangular grid-type coordination polymers based on pyridylterpyridine

Six mixed-valence (CuCuII)-Cu-I compounds containing 4'-(4-pyridyl)-2,2':6',2"-terpyridine (L1) or 4'-(2-pyridyl)-2,2':6',2"-terpyridine (L2) were prepared under the hydrothermal and ambient conditions, and their crystal structures were determined by single-crystal X-ray diffraction. Selection of CuCl2-2H(2)O or Cu(CH3COO)(2)-H2O with the L1 ligand and NH4SCN, KI, or KBr under hydrothermal conditions afforded 1-dimensional mixed-valence (CuCuII)-Cu-I compounds [Cu-2(L1)(mu-1,1-SCN)(mu-Cl)Cl](eta) (1), [Cu-2(L1)(mu-1)(2)Cl](n), (2), [Cu-2(L1)(mu-Br)(2)Br], (3), and [Cu-2(L1)(u-1,3-SCN)(2)(SCN)], (4), respectively. Compound 5, prepared by layering with CuSCN and L1, is a 2-dimensional bilayer structure. In compounds 1-5, the L1 ligand and X (X = Cl, Br, I, SCN) linked between monovalent and divalent copper atoms resulting in the formation of mixed-valence rectangular grid-type M4L4 or M6L6 building blocks, which were further linked by X (X = Cl, Br, 1, SCN) to form 1- or 2-dimensional polymers. The sizes of M4L4 units in 1-4 were fine-tuned by the sizes of X linkers. Reaction of Cu(CH3COO)(2)center dot H2O with L-2 and NH4SCN under hydrothermal conditions gave mixed-valence (CuCuII)-Cu-I compound [Cu-2(L2)(mu-1,3-SCN)(3)](n) (6). Unlike those in 1-5, the structure of 6 was constructed from thiocyanate groups and the pendant pyridine of L2 left uncoordinated. The temperature-dependent magnetic susceptibility studies on compounds 1 and 4 showed the presence of mixed-valence electronic structure.