Linking of amino-capped quinonediimines by divalent transition metal ions: Synthesis, characterization, and comparison to electronic structure calculations

Quantum mechanical density functional theory (DFT) calculations are reported for novel, self-assembled transition metal linked dimers of N,N′-bis (3′-carboxy,4′-aminophenyl)-1,4-quinonediimine, with the metals manganese, iron, cobalt, nickel, copper and zinc each in the +2 oxidation state. Infrared spectroscopy detected systematic changes in the carbon–nitrogen double bond involving the imine nitrogen atoms, from 1457 cm−1 for manganese complex to 1622 cm−1 for the iron complexes. The calculated electronic band gaps of the complexes compare favorably to those for the uncomplexed quinonediimines. The synthesis of the compounds demonstrates a feasible route to the design of a tunable architecture of linear molecular wires derived from properly derivatized quinonediimines.