Crystal structure and spectroscopy of a hydrogen-bridged one-dimensional Cu(II) complex containing both octahedral and square pyramidal geometries inthe same unit cell

Single crystals of the helical hydrogen-bridged one-dimensional Cu(II) comp lex, [Cu(stpy)(2) (CH3COO)(2)(H2O)(2)] (1) [CU(Stpy)(2)(CH3COO)(2)(H2O)] (2 ), are prepared and characterized by elemental and thermal analyses, IR, el ectronic and X-ray crystal structure determination. The crystals are monocl inic, of space group C2/c, with unit cell parameters a = 31.842(7) Angstrom , b = 5.9829(10) Angstrom, c = 30.970(14) Angstrom, beta = 111.78(3)degrees , Z = 4. The asymmetric unit contains two different types of Cu(II) polyhed ra, namely, octahedron and square pyramid within the same unit cell. 1 has elongated octahedral geometry with two nitrogen atoms from stpy and two oxy gen atoms from synmonodentate acetate ligands, transcoordinated to Cu(II) i n the basal plane. The oxygen atoms of the two water molecules occupy the a xial positions. 2 has Cu(II) coordination polyhedra similar to 1, except th at only one of the apical positions is occupied by a water molecule. The st ructure consists of two independent linear chains, one involving octahedral (1) and the other involving square-pyramidal (2) polyhedra, held by hydrog en bridges. The Cu-Cu intra- and interchain separations in both 1 and 2 are 5.983 and 8.214 Angstrom. The unit cell packing shows weak pi -stacking be tween adjacent coordinated stpy ligands in the chain, resulting in ladder-t ype structure. Further, the extended packing reveals helical arrangement of Cu(II) polyhedra in the lattice.