Ligand-Controlled Mixed-Valence Copper Rectangular Grid-Type Coordination Polymers Based on Pyridylterpyridine

Six mixed-valence CuICuII 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 CuCl2·2H2O or Cu(CH3COO)2·H2O with the L1 ligand
and NH4SCN, KI, or KBr under hydrothermal conditions afforded 1-dimensional mixed-valence CuICuII compounds
[Cu2(L1)(μ-1,1-SCN)(μ-Cl)Cl]n (1), [Cu2(L1)(μ-I)2Cl]n (2), [Cu2(L1)(μ-Br)2Br]n (3), and [Cu2(L1)(μ-1,3-SCN)2(SCN)]n
(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, I, 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·H2O with L2 and NH4SCN under hydrothermal
conditions gave mixed-valence CuICuII compound [Cu2(L2)(μ-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.