The gas-phase proton affinities of 4,4'-di(R)-2,2'-bipyridines (R: H, Br, Cl, NO(2), Me) were determined by mass spectrometric measurements and by ab initio calculations at the HF/6-31G and MP2/6-31G levels of theory. The energy barriers for rotation about the central C-C bond were also studied computationally. Two minima were found for both unprotonated and protonated species, the global minima being at the trans planar and cis planar conformations, respectively. Local minima for the unprotonated compounds were at the cis nonplanar conformation and for the protonated compounds at the trans nonplanar. Two different proton affinity values were calculated for each compound by employing different conformations for the protonated species. The computational values were in good agreement with the experimental proton affinities. Substituents affect the proton affinity according to their ability to withdraw or to donate electrons, halogen and nitro-substituted bipyridines having a lower proton affinity and methyl-substituted bipyridine having a higher proton affinity than 2,2'-bipyridine itself.

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A series of [OsII(NN)(CO)2Cl2] complexes where NN is a 2,2′‐bipyridine ligand substituted in the 4,4′ positions by H (C1), CH3 (C2), C(CH3)3 (C3), or C(O)OCH(CH3)2 (C4) has been studied as catalysts for the reduction of CO2. Electrocatalysis shows that the selectivity of the reaction can be switched toward the production of CO or HCOO− with an electron‐donating (C2, C3) or ‐withdrawing (C4) substituent, respectively. The electrocatalytic process is a result of the formation of an Os0‐bonded polymer, which was characterized by electrochemistry, UV/Visible and EPR spectroscopies. Photolysis of the complexes under CO2 in DMF+TEOA produces CO as a major product with a remarkably stable turnover frequency during 14 h of irradiation. Our results suggest that electrocatalysis and photocatalysis occur through two distinct processes, starting mainly from an OsI dimer precatalyst if the reduction is performed by an electrode and an OsI mononuclear species in case of a photoreduction process.

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Carbon monoxide has been found to possess various beneficial effects in living organisms. To study the effects of CO further and to develop potential pharmaceutical agents, a meaningful method for delivering CO to the target organ is needed. It has been found that under physiological conditions various metal carbonyl complexes release carbon monoxide. In this study six novel ruthenium carbonyl complexes Ru(IMOX)(CO)(2)(COOR)Cl(1) (IMOX: imidazolecarbaldehyde oxime, R: Me, Et) were prepared and tested as carbon monoxide releasing molecules (CORMs). Synthesis of the complexes was performed under mild conditions in alcoholic solutions. The ability to release CO was tested spectrophotometrically by following the transformation of deoxymyoglobin to carbonmonoxy myoglobin. All of the complexes studied were found to release CO. Compared to formerly studied ruthenium-based CORMs these complexes offer a way for slower CO release.