Three pimelato-bridged Cu(II) phenanthroline complexes:: [Cu2(phen)2(H2O)2L2]•4H2O, α- and β-[Cu2(phen)2L2]•4H2O, H2L = HOOC(CH2)5COOH

Reaction Of CuCl(2)center dot 2H(2)O, 1,10-phenanthroline (phen) and pimelic acid with Na2CO3 in aqueous methanol afforded a mixture consisting of [Cu-2(phen)(2)(H2O)(2)(C7H10O4)(2)]center dot 4H(2)O (1), alpha-[Cu-2(phen)(2)(C7H10O4)(2)]center dot 4H(2)O (2) and beta-[Cu-2(phen)(2)(C7H10O4)(2)]center dot 4H(2)O (3) at pH=5.8. The structure of compound I has been reported earlier, and consists of hydrogen bonded H2O molecules and dinuclear [Cu-2(phen)(2)(H2O)(2)(C7H10O4)(2)] molecules generated from pirnelate anions, acting as bis(monodentates), bridging square pyramidal Cu ions. The structures of dimorphs 2 and 3 have been established using single-crystal X-ray diffraction methods. They are monoclinic and triclinic, respectively (2: C2/c, a=20.344(2), b=9.828(1), c = 20.802(2) angstrom, beta = 116.10(7)degrees, Z = 4, D-calc = 1.558 g cm(-3); 3: P (1) over bar, a = 10.124(2), b = 10.658(2), c = 10.847(2) angstrom, alpha = 111.36(3), beta = 116.27(3), gamma =93.80(3)degrees, Z= 1, D-calc = 1.529 g cm(-3)). The structures of all three complexes are compared. Both 2 and 3 are composed of hydrogen bonded H2O molecules and polymeric (1)(infinity)[Cu-2(phen)(2)(C7H10O4)(2)] chains, in which dimeric Cu2N4O4 units with square pyramidal coordination geometry are bridged by pimelate anions. The dinuclear molecules in I and polymeric chains in 2 and 3 are assembled via pi-pi stacking and weak C-H center dot center dot center dot O hydrogen bonds into 2D layers, linked by hydrogen bonds.