Ruthenium Picolinate Complex as a Redox Photosensitizer With Wide-Band Absorption

Abstract

Ruthenium(II) picolinate complex, [Ru(dmb) 2 (pic)] + ( Ru(pic) ; dmb = 4,4′-dimethyl-2,2′-bipyridine; Hpic = picolinic acid) was newly synthesized as a potential redox photosensitizer with a wider wavelength range of visible-light absorption compared with [Ru(N ∧ N) 3 ] 2+ (N ∧ N = diimine ligand), which is the most widely used redox photosensitizer. Based on our investigation of its photophysical and electrochemical properties, Ru(pic) was found to display certain advantageous characteristics of wide-band absorption of visible light (λ abs < 670 nm) and stronger reduction ability in a one-electron reduced state ( = −1.86 V vs. Ag/AgNO 3 ), which should function favorably in photon-absorption and electron transfer to the catalyst, respectively. Performing photocatalysis using Ru(pic) as a redox photosensitizer combined with a Re(I) catalyst reduced CO 2 to CO under red-light irradiation (λ ex > 600 nm). TON CO reached 235 and Φ CO was 8.0%. Under these conditions, [Ru(dmb) 3 ] 2+ ( Ru(dmb) ) is not capable of working as a redox photosensitizer because it does not absorb light at λ > 560 nm. Even in irradiation conditions where both Ru(pic) and Ru(dmb) absorb light (λ ex > 500 nm), using Ru(pic) demonstrated faster CO formation (TOF CO = 6.7 min −1 ) and larger TON CO (2347) than Ru(dmb) (TOF CO = 3.6 min −1 ; TON CO = 2100). These results indicate that Ru(pic) is a superior redox photosensitizer over a wider wavelength range of visible-light absorption.

It Takes Three to Tango: The Length of the Oligothiophene Chain Determines the Nature of the Long‐Lived Excited State and the Resulting Photocytotoxicity of a Ruthenium(II) Photodrug

“…The electronic absorption spectra of the compounds within the Ru‐ip‐ n T series (Figure 2a) are characterized by IL transitions localized to the dmb and phen portion of the ip ligand below 300 nm as well as a broad metal‐to‐ligand charge transfer (MLCT) band in the 420–550 nm range, consistent with the spectrum of the parent [Ru(dmb) 3 ] 2+ complex [14,15] . An additional band centered near 370 nm is visible in Ru‐ip‐2T that shifts to longer wavelengths in Ru‐ip‐3T and Ru‐ip‐4T .…”

Supramolecular photocatalysts fixed on the inside of the polypyrrole layer in dye sensitized molecular photocathodes: application to photocatalytic CO2 reduction coupled with water oxidation

“…S1a and S1c, † respectively. In the case of PyrRu, one reversible and one irreversible oxidation wave were observed at E ox 1/2 ¼ 0.86 V and E ox p ¼ 1.19 V vs. Ag/AgNO 3 , respectively; the former was attributed to the one-electron oxidation of the central Ru(II) to Ru(III), as that of [Ru(dmb 47 and the latter was attributed to the oxidation of pyrrole groups. On the other hand, the cyclic voltammogram of Pyr2Ru featured only one broad large oxidation wave at E ox p ¼ 1.00 V, which was attributed to the combination of Ru(II) / Ru(III) oxidation and pyrrole group oxidation.…”

“…S1b and S1d †). 47 A NiO nanoparticle-modied transparent uorine-doped tin oxide (FTO) electrode was prepared by the previously reported squeeze method 9,10 and used as the working electrode for the oxidative electropolymerization (induced by 25 or 50 potential sweeps between E ¼ 0 and +1.35 V vs. Ag/AgNO 3 ) of Ru(II) complexes with pyrrole groups. Fig.…”