Cheap, efficient water electrolysis with non-platinum catalysts is the key to a fossil fuel-free future. Highly conductive, mechanically strong separators are essential components.

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The preference of open chain of growing macromolecule vs. possible cyclic form was examined for the bifunctional cobalt(III)-salen catalyst for the copolymerization of CO2 with epoxides. A variety of possible isomers was considered (resulting from trans/cis-β salen arrangement, different mutual orientation of quaternary ammonium-chains, and possible binding modes). To explore the conformational space, a combined approach was applied, utilizing semiempirical (PM7) MD and the DFT calculations. The preference of the open and cyclic macromolecules attached to the metal center was compared with the corresponding results for isolated model macromolecules, and the systems built of the macromolecule interacting with the tetra-butyl ammonium cation. Result shows that the cyclic structures are strongly preferred for isolated ions, with relatively low cyclization barriers. In the field of positive point charge, the open structures are strongly preferred. For the ions interacting with tetrabutyl ammonium cation, the cyclic structures are preferred, due to delocalization of the positive charge in the cation. For the complexes involving model and “real” Co(III)-salen catalysts, the open structures are strongly preferred. The possible cyclization by dissociation of alkoxide and its transfer to the neighborhood of quaternary ammonium cation is characterized by high activation barriers. Further, the transfer of alkoxide from the metal center to the cation is less likely than the transfer of carbonate, since the metal-alkoxide bond-energy energy is much stronger than energy of metal-carbonate bonding, as shown by ETS-NOCV results. The conclusions are in qualitative agreement with experimental data showing high selectivity towards copolymer formation in the copolymerization processes catalyzed by bifunctional Co(III) salen-complexes.

Propylene oxide (PO) binding and ring-opening reaction with the bifunctional CO2/epoxide copolymerization catalyst, based on the Co(III)-salcy complex including two quaternary ammonium salts with n-butyl substituents (N+-chains) were investigated by Density Functional Theory (DFT) calculations and compared with the model systems without the N+-chains. The importance of the different possible stereoisomers and the stereoselectivity of these processes for (S)- and (R)-enantiomers of PO were considered. To explore the conformational space for the real catalyst, a complex approach, developed previously was applied. The calculations for the model systems directly demonstrate that PO-ring opening proceeds preferentially in trans catalysts’ configuration and no participation of cis-β isomers is viable; nucleophilic attack at the methylene-carbon atom is preferred over that at methine-carbon atom. For the real bifunctional catalyst, with the (S,S)-configuration of cyclohexane, the results indicate a preference of (R)-PO ring-opening over (S)-PO ring-opening (ca. 6 : 5). Concerning stereoisomers resulting from the orientation of N+-chains in the real catalyst, different groups of structures participate in the ring-opening reaction for (R)-PO, and different for (S)-PO. The high population of nonreactive complexes of (R)-PO may be the key factor responsible for decreasing the activity of the analyzed catalyst in the epoxide ring-opening reaction.