A metal-to-ligand charge transfer with mixed intraligand character is observed for the rhenium hexakisarylisocyanide complex [Re(CNAr)6]PF6 (CNAr = 2,6-dimethylphenylisocyanide, λmax = 300 nm). Upon oxidation to [Re(CNAr)6](PF6)2, the dominant low energy optical transition is a ligand-to-metal charge transfer (LMCT) mixed with intraligand transitions (λmax = 650 nm). TD-DFT was used to identify the participating ligand-based orbitals in the LMCT transition, revealing that the majority of the donor orbital is based on the aryl ring (85%) as opposed to the CN bond (14%). For both [Re(CNAr)6]+ and [Re(CNAr)6]2+, structural characterization by X-ray diffraction reveals deviations from Oh geometry at the central Re ion, with larger reduction in symmetry observed for Re(II). For [Re(CNAr)6]+, these structural changes lead to a broadening of the strong ν(CN) stretch (2065 cm–1), as the degeneracy of the T1u IR-active mode is broken. Furthermore, a shoulder is observed for this ν(CN) stretch, resulting from deviation of the C–N–Ar bond from linearity. By contrast, [Re(CNAr)6]2+ has two weak bands in the ν(CN) region (2065 and 2121 cm–1). DFT calculations indicate that reduction of symmetry at the central rhenium ion manifests in the decrease in intensity and the observed split of the ν(CN) band. Stability of both complexes are limited by light-induced decomposition where Re(I) dissociates a isocyanide ligand upon irradiation and Re(II) absorbance decays under ambient light. These data provide new insights to the electronic structure of [Re(CNAr)6]2+, enhancing our understanding of LMCT excited states and the versatility of isocyanide ligands.

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Inherently disordered structures of carbon nitrides have hindered an atomic level tunability and understanding of their catalytic reactivity. Herein, coordination of copper cations within a crystalline carbon nitride, i.e., poly(triazine imide) or CNx, was found to yield two ordered structures for Cu-CNx wherein one or two Cu(I) cations coordinate to its intralayer N-triazine groups. The crystallites electrophoretically deposit from aqueous particle suspensions and yield current densities of ~10 to 50 mA/cm2 with a concomitant and increasing reduction of CO2 and H2O. Reduction of CO2 increases for smaller particles as mechanistic calculations reveal its catalysis mediated by two intralayer Cu atoms.