Carbazole modification of ruthenium bipyridine–dicarboxylate oxygen evolution molecular catalysts. Issue 44 (3rd November 2021)

• Record Type: Journal Article
• Authors: Otsuka, Hiroki; Kobayashi, Atsushi; Yoshida, Masaki; Kato, Masako
• Is Part Of: Dalton transactions. Volume 50:Issue 44(2021)
• Page Start: 16233
• Page End: 16241
• Publication Date: 2021-11-03
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d1dt02824c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Two oxygen-evolution molecular catalysts bearing the carbazole moiety as the hole-mediating precursor were synthesized and their activities were evaluated. Abstract : We synthesized new oxygen-evolving molecular Ru(ii ) catalysts with one or two carbazole moieties on the axial pyridyl ligands, namely [Ru(bda)(cbz-py)(py)] and [Ru(bda)(cbz-py)2 ] [C1 and C2 ; bdaH2 = 2, 2′-bipyridyl-6, 6′-dicarboxylic acid, py = pyridine, and cbz-py = 9-(pyridin-4-yl)-9 H -carbazole] to investigate the effect of cbz modification on the photophysical and catalytic properties of the well-known molecular catalyst [Ru(bda)(py)2 ] (C0 ). The initial oxygen-evolving catalytic activities of C1 and C2 were higher than that of C0 in both a chemical reaction driven by the strong oxidant (NH4 )2 [Ce(NO3 )6 ] (CAN = ceric ammonium nitrate) and photochemical oxidation using a [Ru(bpy)3 ] 2+ (bpy = 2, 2′-bipyridine) photosensitizer with Na2 S2 O8 as the sacrificial oxidant. The higher activities were ascribed to the electron-withdrawing cbz groups, which promoted the radical coupling reaction to form a Ru IV –O–O–Ru IV species. A unique oxygen-evolution rate change behaviour was observed for both C1 and C2 in the presence of a large excess of CAN, suggesting the competitive oxidation of the cbz moiety during the chemical oxygen evolution reaction. This work suggests that the cbz modification of an oxygen evolution molecular catalyst is a promising approach for integrating the hole accumulator near the oxygen evolution catalytic centre.