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Construction of artificial photosynthetic systems including CO2 reduction is a promising pathway to produce carbon-neutral fuels and mitigate the greenhouse effect concurrently. However, the exploitation of earth-abundant catalysts for photocatalytic CO2 reduction remains a fundamental challenge, which can be assisted by a systematic summary focusing on a specific catalyst family. Cobalt-based complexes featuring tripodal ligands should merit more insightful discussion and summarization, as they are one of the most examined catalyst families for CO2 photoreduction. In this feature article, the key developments of cobalt-based tripodal complexes as molecular catalysts for light-driven CO2 reduction are discussed to offer an upcoming perspective, analyzing the present progress in electronic/steric tuning through ligand modification and dinuclear design to achieve a synergistic effect, as well as the bottlenecks for further development. [ABSTRACT FROM AUTHOR]

The kinetics for interfacial electron transfer (ET) from a transparent conductive oxide (tin-doped indium oxide, ITO, Sn:In2O3) to molecular acceptors 4-[N,N-di(p-tolyl)amino]benzylphosphonic acid, TPA, and [RuII(bpy)2(4,4′-(PO3H2)2-bpy)]2+, RuP, positioned at variable distances within and beyond the electric double layer (EDL), were quantified in benzonitrile and methanol by nanosecond absorption spectroscopy as a function of the thermodynamic driving force, −ΔG°. Relevant ET parameters such as the rate constant, ket, reorganization energy, λ, and electronic coupling, Hab, were extracted from the kinetic data. Overall, ket increased as the distance between the molecular acceptor and the conductor decreased. For redox active molecules within the Helmholtz planes of the EDL, ket was nearly independent of −ΔG°, consistent with a negligibly small λ value. Rips–Jortner analysis revealed a non-adiabatic electron transfer mechanism consistent with Hab < 1 cm−1. The data indicate that the barrier for electron transfer is greatly diminished at the conductor–electrolyte interface. [ABSTRACT FROM AUTHOR]

We report here the spectroscopic properties of four very closely related mixed-valence cyanide-bridged bimetallic complexes, trans-[Ru(T)(bpy)(μ-NC)Ru(L)4(CN)]3+ (T = tris(1-pyrazolyl)methane (tpm, a) or 2,2';6',2"-terpyridine, (tpy, b), and L = pyridine (py, 1) or 4-methoxypyridine (MeOpy, 2)). In acetonitrile all the complexes present intervalence charge transfer (IVCT) transitions in the NIR region, but their intensities are widely different, with the intensity of the transition observed for 1a-b3+ around four times larger than that observed for 2a-b3+. This contrasting behavior can be traced to the different nature of the dπ acceptor orbitals involved in these transitions, as confirmed by (TD)DFT calculations. The spectroscopy of 1a-b3+ provides evidence that the spin density is delocalized over the two ruthenium ions, such as a narrowing of the IVCT bands that results in the resolution of the expected three bands, and a weak solvent dependence of the energy of these transitions. The spectroscopy of 2a-b3+ instead indicates that the spin density is localized on one ruthenium ion. The IVCT in these systems is particularly weak due to the configuration of the Ru(III), where the vacant orbital is perpendicular to the cyanide bridge. [ABSTRACT FROM AUTHOR]

The electrocatalytic reduction of CO 2 to high-value fuels by renewable electricity is a sustainable strategy, which can substitute for fossil fuels and circumvent climate changes induced by elevated CO 2 emission levels, making the rational design of versatile electrocatalysts highly desirable. Among all the electrocatalytic materials used in the CO 2 reduction reaction, nickel phthalocyanine (NiPc)-based electrocatalysts have attracted considerable attention recently because of their high CO selectivity and catalytic activity. Herein, we review the latest advances in CO 2 electroreduction to CO catalyzed by immobilized NiPc and its derivatives on diverse surfaces. Specific strategies, the structure-performance relationship and the CO 2 -to-CO reaction mechanism of these NiPc-based electrocatalysts are analyzed. Future opportunities and challenges for this series of powerful heterogeneous electrocatalysts are also highlighted.