Anthracene-bridged dinuclear rhenium complexes are reported for electrocatalytic carbon dioxide (CO) reduction to carbon monoxide (CO). Related by hindered rotation of each rhenium active site to either side of the anthracene bridge, cis and trans conformers have been isolated and characterized. Electrochemical studies reveal distinct mechanisms, whereby the cis conformer operates via cooperative bimetallic CO activation and conversion and the trans conformer reduces CO through well-established single-site and bimolecular pathways analogous to Re(bpy)(CO)Cl. Higher turnover frequencies are observed for the cis conformer (35.3 s) relative to the trans conformer (22.9 s), with both outperforming Re(bpy)(CO)Cl (11.1 s). Notably, at low applied potentials, the cis conformer does not catalyze the reductive disproportionation of CO to CO and CO in contrast to the trans conformer and mononuclear catalyst, demonstrating that the orientation of active sites and structure of the dinuclear cis complex dictate an alternative catalytic pathway. Further, UV-vis spectroelectrochemical experiments demonstrate that the anthracene bridge prevents intramolecular formation of a deactivated Re-Re-bonded dimer. Indeed, the cis conformer also avoids intermolecular Re-Re bond formation.

Well-defined dinuclear rhenium photocatalysts featuring an anthracene chromophore are significantly faster and more durable than their mononuclear counterparts.

Triaquabenzoatocalcium monobenzoate [Ca(Ben)(H 2 O) 3 ](Ben)(s) was synthesized by the method of liquid phase reaction. Chemical and element analyses and X-ray crystallography were used to characterize the composition and structure of the complex. The lattice potential energy of the compound was calculated to be U POT ) 426.61 kJ · mol -1 on the basis of crystal structure information. Low-temperature heat capacities over the temperature range from (78 to 360) K were measured by an automated adiabatic calorimeter, and a polynomial equation was fitted by the least-squares method. On the basis of the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated at intervals of 5 K. The thermal decomposition of the complex was studied using TG and DSC analyses. In accordance with Hess's law, a reasonable thermochemical cycle was designed based on the preparation reaction of the compound. The standard molar enthalpies of dissolution for the reactants and product of the reaction in the selected solvent were measured by an isoperibol solutionreaction calorimeter. The enthalpy change of the liquid phase reaction was calculated to be ∆ r H m o ) -(46.68 ( 0.40) kJ · mol -1 , and the standard molar enthalpy of formation of the complex was determined to be ∆ f H m o [Ca(Ben)(H 2 O) 3 ](Ben),s ) -(2088.2 ( 1.1) kJ · mol -1 by means of the enthalpy change of the reaction and other auxiliary thermodynamic quantities.