Photocatalytic Conversion of CO₂ to CO Using Rhenium Bipyridine Platforms Containing Ancillary Phenyl or BODIPY Moieties

Harnessing of solar energy to drive the reduction of carbon dioxide to fuels requires the development of efficient catalysts that absorb sunlight. In this work, we detail the synthesis, electrochemistry, and photophysical properties of a set of homologous fac-ReI(CO)3 complexes containing either an ancillary phenyl (8) or BODIPY (12) substituent. These studies demonstrate that both the electronic properties of the rhenium center and BODIPY chromophore are maintained for these complexes. Photolysis studies demonstrate that both assemblies 8 and 12 are competent catalysts for the photochemical reduction of CO2 to CO in dimethylformamide (DMF) using triethanolamine (TEOA) as a sacrificial reductant. Both compounds 8 and 12 display turnover frequencies (TOFs) for photocatalytic CO production upon irradiation with light (λex ≥ 400 nm) of ∼5 h–1 with turnover number (TON) values of approximately 20. Although structural and photophysical measurements demonstrate that electronic coupling between the BODIPY and fac-ReI(CO)3 units is limited for complex 12, this work clearly shows that the photoactive BODIPY moiety is tolerated during catalysis and does not interfere with the observed photochemistry. When taken together, these results provide a clear roadmap for the development of advanced rhenium bipyridine complexes bearing ancillary BODIPY groups for the efficient photocatalytic reduction of CO2 using visible light.利用太阳能驱动二氧化碳还原制备燃料，亟需开发可吸收太阳光的高效催化剂。本研究详细报道了一系列同系列面式三羰基合铼(I)（fac-Reᴵ(CO)₃）配合物的合成方法、电化学特性与光物理性质，其辅助配体分别为苯基（编号8）或二吡咯亚甲基氟化硼络合物（BODIPY，编号12）。研究表明，此类配合物均保留了铼中心与BODIPY发色团的固有电子特性。光解实验证实，配合物8与12均可作为高效催化剂，在以三乙醇胺（TEOA）为牺牲还原剂的二甲基甲酰胺（DMF）溶剂中，实现二氧化碳的光化学还原生成一氧化碳。在波长λ_ex ≥ 400 nm的光辐照下，两种配合物光催化生成一氧化碳的转换频率（TOFs）约为5 h⁻¹，转换数（TON）约为20。尽管结构与光物理表征结果显示，配合物12中BODIPY基团与fac-Reᴵ(CO)₃单元间的电子耦合作用较弱，但本研究明确证实，具有光活性的BODIPY官能团在催化过程中可稳定存在，且不会干扰观测到的光化学反应。综上，本研究结果为开发带有辅助BODIPY基团的高性能联吡啶三羰基合铼配合物，实现可见光驱动二氧化碳高效光催化还原提供了清晰的指导思路。