Development of Visible-Light Driven Cu(I) Complex Photosensitizers for Photocatalytic CO2 Reduction

Abstract

The visible-light responsive Cu(I)-complex photosensitizers were developed by introducing various aromatic substituents at the 4,7-positions of a 2,9-dimethyl-1,10-phenanthroline (dmp) ligand in a heteroleptic Cu I (dmp)(DPEphos) + -type complexes (DPEphos = [2-(diphenylphosphino)phenyl]ether) for photocatalytic CO 2 reduction. Introducing biphenyl groups (Bp-) on the dmp ligand enhanced the molar extinction coefficient (ε) of the metal-to-ligand charge transfer (MLCT) band in the visible region (ε = 7,500 M −1 cm −1 ) compared to that of the phenyl (Ph-)-containing analog (ε = 5,700 M −1 cm −1 at λ max = 388 nm). However, introducing 4-R-Ph- groups (R = the electron-withdrawing groups NC-, or NO 2 -) led to a red shift in the band to λ max = 390, 400, and 401 nm, respectively. Single-crystal X-ray analysis showed the Ph- groups were twisted because of the steric repulsion between the 2,6-protons of the Ph- groups and 5,6-protons of the dmp ligand. The result strongly indicated that the π-conjugation effect of the 4-R-Ph- groups is so weak that the lowering of the energy of the dmp π * orbitals is small. However, when 4-R-ph- was substituted by a 5-membered heterorings, there was a larger red shift, leading to an increase in the ε value of the MLCT absorption band. Thus, the substitution to 2-benzofuranyl- groups resulted in visible-light absorption up to 500 nm and a shoulder peak at around 420 nm (ε = 12,300 M −1 cm −1 ) due to the expansion of π-conjugation over the substituted dmp ligand. The photocatalytic reaction for CO 2 reduction was tested using the obtained Cu I complexes as photosensitizers in the presence of a Fe(dmp) 2 (NCS) 2 catalyst and 1,3-dimethyl-2-phenyl-2,3-dihydro-1 H -benzo[d]imidazole as a sacrificial reductant, which showed improved CO generation.

Construction of 1D Ag-AgBr/AlOOH Plasmonic Photocatalyst for Degradation of Tetracycline Hydrochloride

“…To date, many efforts like adsorption, coagulation, chemical oxidation, deposition, membrane separation, biological, physicochemical, and electrochemical techniques have been utilized to remove these dyes and antibiotics, with a particular focus on MB and TCH (Zhang et al, 2018;Gholami et al, 2019Gholami et al, , 2020Huo et al, 2019b;Kohtani et al, 2019;Li et al, 2019c;Liu et al, 2019b;Wang et al, 2019a). However, long handling times, secondary pollutants and low efficiencies limits the usage of these techniques (Wang et al, 2014;Li et al, 2017Li et al, , 2018Karimi et al, 2019;Liu et al, 2019a;Qi et al, 2019b,c;Shen et al, 2019;Takeda et al, 2019).…”

[Cu(bcp)(DPEphos)]+: A Versatile and Efficient Copper-Based Photoredox Catalyst and Photosensitizer

“…The geometry of [Cu(bcp)DPEPhos]PF6 in its solid state has been assessed by X-ray diffraction, (5) the complex adopting the classical distorded tetrahedric geometry. (4) In solution, it shows an absorption band centered around 380 nm and absorbs light up to 440 nm in a variety of organic solvents.…”

“…(F) CO2 photoreduction. (5,11) Highest TON among the photocatalytic systems using Fe complexes as catalyst.…”

Synthesis, structure, characterization and biological evaluation of 3‐substituted 1‐pyridin‐2‐ylimidazo[1,5‐a]pyridine‐based copper(I)–phosphine complexes for anticancer drug screening

“…All complexes show a oxidation wave at 0.75-0.92 V versus SCE, which, by comparison with similar complexes, can be assigned to metal centred oxidation to Cu(II). [53][54][55] The ΔE p of the complexes (LC41, 85; LC42, 166; LC43, 120; LC44, 170; and LC45, 124 mV) indicates that LC41 ( Figure S32) undergoes quasireversible metal oxidation whereas LC42-LC45 follow irreversible redox process. It is because the oxidation on the metal is likely to result in significant geometrical rearrangement, as divalent copper ions prefer a flatter geometry.…”