Three novel dimolybdenum dimers [Mo2(DAniF)3]2(μ-OSCC6H4CSO), [Mo2(DAniF)3]2(μ-O2CC6H4CS2), and [Mo2(DAniF)3]2(μ-S2CC6H4CS2) (DAniF = N,N'-di(p-anisyl)formamidinate) have been synthesized and characterized by single-crystal X-ray diffractions. Together with the terephthalate analogue, the four compounds, denoted as [O2-O2], [OS-OS], [S2-S2], and [O2-S2], have similar molecular skeletons and Mo2···Mo2 separations (∼12 Å), but varying sulfur contents or symmetry. The singly oxidized complexes [O2-O2](+), [OS-OS](+), [S2-S2](+), and [O2-S2](+) display characteristic intervalence transition absorption bands in the near- and mid-IR regions, with differing band energy, intensity, and shape. Applying the geometrical length of the bridging group "-CC6H4C-" (5.8 Å) as the effective electron transfer distance, calculations from the Mulliken-Hush equation yield electronic coupling matrix elements (H(ab)) in the range 600-900 cm(-1). Significantly, this series presents a transition from electron localization to "almost-delocalization" as the carboxylate groups of the bridging ligand are successively thiolated. In terms of Robin-Day's scheme, [S2-S2](+) is best described as an intermediate between Class II and III, while [O2-O2](+) and [OS-OS](+) belong to Class II. It is unusual that the Class II-III transition occurs in such a weakly coupled system (H(ab) < 1000 cm(-1)). This is attributed to the d(δ)-p(π) conjugation between the Mo2 center and bridging ligand. By electrochemical and spectroscopic methods, the internal energy difference for [O2-S2](+) is determined to be 2250 ± 80 cm(-1), which controls the charge distribution of the cation radical. The experimental results and theoretical analyses illustrate that the unsymmetrical geometry leads to unbalanced electronic configurations and asymmetrical redox and optical behaviors.

Three symmetrical and one unsymmetrical dimolybdenum dimers, namely, [Mo2(DAniF)3]2(E2CC6H4CE2) (DAniF = N,N′-di(p-anisyl)formamidinate and E = O or S), are structurally and electronically closely related. The mixed-valence cation radicals display well-defined metal to ligand (ML), ligand to metal (LM), and metal to metal (MM) charge transfer absorption bands. Successive thiolations of the complexes result in steady increases of the electronic coupling between the two [Mo2] units. The electronic coupling matrix elements (H ab) calculated from the Hush model fall in the range of 600–900 cm–1, which are remarkably consistent with the results from the CNS superexchange formalism. Spectroscopic analyses suggest that the intramolecular electron transfer occurs by electron-hopping and hole-hopping in concert. The rate constants (k et) are estimated in the range of 1011–1012 s–1 for the symmetrical analogues and 107 s–1 for the unsymmetrical species. The ultrafast electron transfer in such a weakly coupled system (H ab < 1000 cm–1) is attributed to the d(δ)–p(π) conjugation between the dimetal centers and the bridge.

The first thiocarboxylation of styrenes and acrylates with CO was realized by using visible light as a driving force and catalytic iron salts as promoters. A variety of important β-thioacids were obtained in high yields. This multicomponent reaction proceeds in an atom- and redox-economical manner with broad substrate scope under mild reaction conditions. Notably, high regio-, chemo-, and diasteroselectivity are observed. Mechanistic studies indicate that a radical pathway can account for the unusual regioselectivity.

Light-driven carbon dioxide (CO 2 ) capture and utilization is one of the most fundamental reactions in Nature. Herein, we report the first visible-light-driven photocatalyst-free hydrocarboxylation of alkenes with CO 2 . Diverse acrylates and styrenes, including challenging tri-and tetrasubstituted ones, undergo anti-Markovnikov hydrocarboxylation with high selectivities to generate valuable succinic acid derivatives and 3-arylpropionic acids. In addition to the use of stoichiometric aryl thiols, the thiol catalysis is also developed, representing the first visible-lightdriven organocatalytic hydrocarboxylation of alkenes with CO 2 . The UV-vis measurements, NMR analyses, and computational investigations support the formation of a novel charge-transfer complex (CTC) between thiolate and acrylate/styrene. Further mechanistic studies and density functional theory (DFT) calculations indicate that both alkene and CO 2 radical anions might be generated, illustrating the unusual selectivities and providing a novel strategy for CO 2 utilization.