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Organo-bridged dicobaloximes with four different dioximes Py(L) 2 CoCH 2 -R-CH 2 Co(L) 2 Py (L ) dmgH, dpgH, chgH, and gH) have been synthesized and characterized by 1 H and 13 C NMR and FAB mass spectroscopy. The cis influencing order observed in dicobaloximes is similar to the previously observed order in monocobaloximes. The cyclic voltammetric results show that an irreversible single-step two-electron reduction of Co III to Co I takes place. The Co-C bond in 4a cleaves during crystallization and results in the formation of o-vinylbenzyl cobaloxime. The variable-temperature 1 H NMR study suggests that the Co-C bond rotation is restricted and its magnitude depends on both the nature of the bridging ligand and the dioxime.

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Background: Replacing chemical catalysts with biocatalysts is a widely recognized goal of white biotechnology. For biocatalytic processes requiring low water containing media, enzymes for example commercial preparations of lipases, show low catalytic efficiencies. Some high activity preparations for addressing this concern have been described. Protein coated microcrystals (PCMC) constitute one such preparation. The present work describes a Combi-PCMC for synthesis of biodiesel from the oil extracted from spent coffee grounds. Results: Different lipases were screened for biodiesel synthesis from crude coffee oil out of which Novozym 435 gave the best conversion of 60% in 4 h. Optimization of reaction conditions i.e. % water, temperature and purification of coffee oil further enhanced conversion upto 88% in 24 h. A mixture of Novozym 435 and a cheap commercially available 1,3-specific lipase RMIM (from Mucor miehei) was used in different ratios and 1:1 was found to be the best trade-off between conversion and cost. The commercial preparations then were replaced by a novel biocatalyst design called Combi-Protein coated microcrystals (Combi-PCMC) wherein CAL B and Palatase were co-immobilized with K 2 SO 4 as the core and this performed equivalent to the commercial preparations giving 83% conversion in 48 h.

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