Hydroxido-Supported and Carboxylato Bridge-Driven Aggregation for Discrete [Ni-4] and Interconnected [Ni-2](n) Complexes

Four different carboxylato bridges have been efficiently utilized for growth of three tetranuclear nickel(II) complexes [Ni-4(mu(3)-H2L)(2)(mu(3)-OH)(2)(mu(1,3)-CH3CO2)(2)] (ClO4)(2) (1), [Ni-4(mu(3)-H2L)(2)(mu(3)-OH)(2)(mu(1,3)-C2H5CO2)(2)] (ClO4)(2).1/2H(2)O (2), and [Ni-4(mu(3)-H2L)(2)(mu(3)-OH)(2)(mu(3)-O2C-C6H4-pNO(2))(2)](ClO4)(p-NO2-C6H4-CO2)-DMF center dot 5H(2)O (3) and one dinuclear nickel(II)-based chain complex {[Ni-2(mu-H2L)(mu(1,3)-O2CCH2Ph)(2)(H2O)] (ClO4)center dot 1/2(CH3OH)}(n) (4). These were obtained via the reaction of Ni(ClO4)(2)center dot 6H(2)O with H3L [2,6-bis ((2-(2-hydr oxyethylamino) ethylimino) methyl)-4-methyl-phenol] and RCO2Na (R = CH3,C2H5, p-NO2C6H4, and PhCH2). This family of complexes is developed from {Ni-2(mu-H2L)}(3+) fragments following self-aggregation. The complexes were characterized by X-ray crystallography and magnetic measurements. The changes from acetate, propionate, and p-nitrobenzoate to phenylacetate groups resulted in two different types of coordination aggregation. These compounds are new examples of [Ni-4] and [Ni-2] complexes where organization of the building motifs are guided by the type of the carboxylate groups responsible for in-situ generation and utilization of HO- bridges with alteration in the aggregation process within the same ligand environment. Studies on the magnetic behavior of the compounds reveal that the exchange coupling within 1-4 is predominantly antiferromagnetic in nature.