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A series of metallophthalocyanine (PcM) complexes with axial N-heterocyclic carbene ligands (NHC; 1,3-diisopropylimidazol-2-ylidene (DIP) and 1,3-dimethylbenzimidazol-2-ylidene (DMB)) were prepared and structurally characterized. PcCoII(DIP), PcZnII(DIP), and PcZnII(DMB) are five-coordinate complexes with mild dome-type Pc-ring distortions, while PcFeII(DIP)2 is six-coordinate and has a very large ruffle-type ring-distortion with respect to typical PcM(L)2 systems. The distortion is induced by the highly steric axial DIP ligands. The distortions were quantified and classified by their bond lengths and torsion angles, and according to the normal-coordinate structural decomposition (NSD) analysis. Upon ligation of the NHC, the insoluble PcM materials were solublized in common organic solvents, with typical UV-visible Q-band maxima observable between 658 and 677 nm; the increased solubility is rationalized in terms of the reduced solid-state aggregation of the complexes, attributable to the axial ligation. [ABSTRACT FROM AUTHOR]

A series of ClRe[(CO).sub.3]-containing complexes with 1-metbyl-1H-tenzo[d]imidazol-2-yl)quinoline (Me-QuBIm), 1-benzyl-1H-benzo [d]imidazol-2-yl)qvjinoline (Bn-QuBIm), and 2-(1-(4-methoxybenzyl)-1H-benzo[d]imidazol-2-yl)quinoline (OMeBn-QuBIm) ligands were prepared and characterized. Each complex was characterized using [.sup.1]H and [.sup.13]C NMR, infrared, UV-vis, and fluorescence spectroscopies, and cyclic voltammetry. The physical properties of each complex are similar to the parent ClRe[(CO).sub.3](2-(1H-benzo[d]imidazol-2-yl)quinoline) complex. However, the electrochemical behavior is distinct from the parent, showing reversible voltammograms and poor C[O.sub.2] reduction activity. Addition of [K.sup.+] or [Mg.sup.2+] as Lewis acids modestly increases catalytic currents, but at large overpotentials. The work presented here is consistent with a mechanism that involves rhenium reduction and deprotonation of imidazole and benzimidazole prior to C[O.sub.2] reduction electrocatalysis. Key words: rhenium (I), carbon dioxide reduction, Lewis acids, electrocatalysis. Nous avons synthetise et caracterise une serie de complexes de ClRe[(CO).sub.3] portant des ligands de type l-methyl-1H-benzo[d] imidazol-2-yl)quinoline (Me-QuBIm), l-benzyl-1H-benzo[d]imidazol-2-yl)quinoline (Bn-QuBIm) et 2-(1-(4-methoxybenzyl)-1H-benzo[d]imidazol-2-yl)quinoline (OMeBn-QuBIm). Nous avons caracterise chaque complexe par spectroscopic RMN [.sup.1]H, RMN [.sup.13]C, infrarouge et UV-vis, par fluoroscopie et par voltamperometrie cyclique. Les proprietes physiques de chaque complexe sont semblables a celles du complexe ClRe[(CO).sub.3](2-(1H-benzo[d]imidazol-2-yl)qumoline) d'origine. Cependant, ces complexes presentent un comportement electrochimique distinct de celui du complexe d'origine, des voltamperogrammes reversibles, de meme qu'une faible activite reductrice envers le C[O.sub.2]. L'ajout d'acides de Lewis a base d'ions [K.sup.+] et [Mg.sup.2+] augmente legerement les courants catalytiques, mais des excedents de potentiel importants sont necessaires. Les resultats des presents travaux permettent de conclure a un mecanisme faisant intervenir la reduction et la deprotonation de l'imidazole et du benzimidazole avant que la reduction du C[O.sub.2] par electrocatalyse se produise. [Traduit par la Redaction] Mots-cles : rhenium (I), reduction du dioxyde de carbone, acides de Lewis, electrocatalyse., Introduction The electrochemical reduction of C[O.sub.2] to CO, C[H.sub.3]OH, or hydrocarbons is an important target in ongoing efforts at decarbonization. An artificial, closed-loop carbon cycle may be an important advance [...]

Porphyrins are archetypal ligands in inorganic chemistry. The last 10 years have seen important new advances in the use of metalloporphyrins as catalysts in the activation and reduction of small molecules, in particular O2 and CO2. Recent developments of new molecular designs, scaling relationships, and theoretical modeling of mechanisms have rapidly advanced the utility of porphyrins as electrocatalysts. This Minireview focuses on the summary and evaluation of recent developments of metalloporphyrin O2 and CO2 reduction electrocatalysts, with an emphasis on contrasting homogeneous and heterogeneous electrocatalysis. Comparisons for proposed reaction mechanisms are provided for both CO2 and O2 reduction, and ideas are proposed about how lessons from the last decade of research can lead to the development of practical, applied porphyrin‐derived catalysts. [ABSTRACT FROM AUTHOR]