Project

Synthesis, Characterization and Liquid Crystalline Studies of 1,3-bis(4-pyridyl) Propane Bridged Dicobaloximes

A large number of organo-bridged dicobaloximes, PyCo(L2)-R-Co(L2)Py, have been reported in the literature. Ligand-bridged complexes are of interest in view of their role as reaction intermediates in innersphere electron transfer processes. Nitrogen heterocycles are extensively used as bridging ligands in coordination and metallosupramolecular chemistry.

E. J. Starr et al have reported two series of monocobaloximes of type [Co(Hdmg)2{(CH2)nI}(py)] (n= 5, 6, 8, 9 or 10 and [Co(Hdmg)2{(CH2)3OC(O)-C6H4R)(py)] (R = H, o-, m- or p-OCH3, p-OC7H15 or p- OC9H19), anticipating liquid crystalline (mesomorphic) phases in these complexes. However, liquid crystalline properties were not observed for these complexes. Surfactant molecules sort of arrangement was observed only in solid state crystal packing due to van der Waals forcesfor n-C14H29Co(dmgH)2Py and due to intermolecular hydrogen bonding for n-C8H17Co(gH)(dpgH)Py.

Preliminary studies as part of this project show that ligand bridged dicobaloxime of the type [CH3Co(dmgH)2]2 μ-1,3 bis(4-pyridyl) propane show smectic-G mesophase under the optical polarising microscope. A thorough literature survey shows that so far no such study has been done in the mono or bridged cobaloximes. Therefore, the primary objective of this project is to synthesize a series of dipyridine bridged icobaloximes. Synthesis of these complexes is interesting in itself. In addition, the two cobaloxime moieties may give useful information on the cis-trans influence, and the mesomorphic phase. The two cobaloxime moieties provide rigidity which is required for the anisotropy; the – (CH2) spacer in the bridging ligand and the alkyl (Co-R) group provide flexibility to stabilize the molecular alignment within the mesophase.