Electrocatalytic reduction of CO₂ to CO by a series of organometallic Re(i)-tpy complexes

Abstract

A series of organometallic Re(I)(L)(CO)3Br complexes with 4'-substituted terpyridine ligands (L) has been synthesised as electrocatalysts for CO2 reduction. The complexes' spectroscopic characterisation and computationally optimised geometry demonstrate a facial...

Structural and Photophysical Trends in Rhenium(I) Carbonyl Complexes with 2,2′:6′,2″-Terpyridines

“…Similar to the structurally related [ReX(CO) 3 (bipy)], the UV-Vis spectra of [ReX(CO) 3 (terpy-κ 2 N)] display intense bands below 350 nm attributed to π→π* and n→π* intraligand (IL) transitions, along with moderate, broad absorption in the range of 350-450 nm largely assigned to MLCT excitations (Figure 2 and Table S4). This assignment was also supported by density functional (DFT) calculations [46][47][48].…”

“…Distinctly from the Re(I) complexes with phenyl, naphtyl, and phenanthrenyl pendant groups, the complexes [ReCl(CO)3(R-terpy-κ 2 N)] with 9-anthryl (5 Cl ), 2-anthryl (6 Cl ), and 1-pyrenyl (7 Cl ) groups are non-emissive in the solid state, and their solution photophysical properties are strongly affected by the aryl substituent [61,62]. As supported by Further evidence for the formation of the 3 MLCT state in these systems was provided using fs-TA spectroscopy, carried out for the representative complexes [ReX(CO) 3 (R-terpyκ 2 N)] with phenyl (1 Cl , 1 Br ) and 1-naphtyl substituent (2 Cl ) [48,59,61], as well as timeresolved infrared spectroscopy performed for 1 Cl [63]. All these studies confirmed the formation of the 3 S5) were attributed to the halide contribution to the excited state [47].…”

“…Among complexes [Re(X/L)(CO) 3 (R-terpy-κ 2 N)] 0/+ , structural differences are mainly noticed regarding the relative orientation of the appended aromatic group and central pyridine ring as well as the dihedral angle between the least squares planes of the central pyridine and the uncoordinated pyridyl group. The optical properties of [ReX(CO) 3 (terpy-κ 2 N)] (X = Cl, Br) have been extensively investigated, as reported in [32,39,[46][47][48][49][50]. The absorption behavior of [ReX(CO) 3 (terpy-κ 2 N)] was found to be typical of [ReX(CO) 3 (diimine)] chromophores.…”

“…A more comprehensive understanding of excited-state processes in [ReX(CO) 3 (terpyκ 2 N)] was achieved through femtosecond transient absorption (fs-TA) spectroscopy [48,50]. By analogy to [ReX(CO) 3 (bipy)] [53,54], the TA spectra of [ReX(CO) 3 (terpy-κ 2 N)] were characterized by two positive signals attributed to excited-state absorptions (ESA): a sharp band below 400 nm assigned to the absorption of the bipy/terpy anion radical and a broad absorption in the visible region corresponding to X/L •− →Re (Ligand-to-Metal-Charge-Transfer, LMCT) transitions.…”

“…Molecules 2024, 29, x FOR PEER REVIEW 9 of 28 frozen-state emission of 1 Cl -4 Cl appears in a noticeably higher energy region and shows a significantly prolonged luminescence lifetime in relation to the RT emission in solution. Further evidence for the formation of the 3 MLCT state in these systems was provided using fs-TA spectroscopy, carried out for the representative complexes [ReX(CO)3(R-terpy-κ 2 N)] with phenyl (1 Cl , 1 Br ) and 1-naphtyl substituent (2 Cl ) [48,59,61], as well as time-resolved infrared spectroscopy performed for 1 Cl [63]. All these studies confirmed the formation of the 3 S5) were attributed to the halide contribution to the excited state [47].…”