Liquid-Liquid Interphase (Biphasic) as the Reaction Medium in the Assembly of a Hierarchy of Structures of 4,4′-Azodibenzoic Acid with Zinc and Cadmium

The compounds [Zn(C12H8N2)](2)[C12N2H8(COO)(2)](2)center dot(C6H12O)center dot(H2O), I, [Zn(C12H8N2)][C12N2H8(COO)(2)], II, [Cd(C12H8N2)(H2O)][C12N2H8(COO)(2)]center dot(H2O), III, [Zn(C10N2H8)][C12N2H8(COO)(2)]center dot 0.5(C10N2H8), IV, [Cd(C12N2H8(COO)(2)center dot H2O], V, and [Zn-3(mu(2)-O)(mu(3)-O)(3)][C12N2H8(COO)(2)], VI, have been synthesized by using a biphasic approach (I, III, V, VI) or regular hydrothermal method (II, IV). The compounds exhibit one (I and II), two (In), and three dimensionally (IV, V, VI) extended structures. The flexible azodibenzoate ligand gives rise to a 3-fold interpenetration (IV) when the synthesis was carried out using normal hydrothermal methods. The biphasic approach forms structures without any interpenetrations, especially in the three-dimensional structures of V and VI. Formation of Cd2O2 dimers in V and extended M-O(H)-M two-dimensional layers in VI suggests the subtle structural control achieved by the biphasic method. Transformation studies indicate that it is possible to transform I to II. Lewis acid catalytic studies have been performed to evaluate the role of the coordination environment in such reactions. All the compounds have been characterized by a variety of techniques that includes powder X-ray diffraction, infrared, thermogravitric analysis, UV-vis, photoluminescence studies.