Alkyne substituted mononuclear photocatalysts based on [RuCl(bpy)(tpy)]⁺

Abstract

The ethynyl-phenylene substituted 2,2':6',2''-terpyridine (tpy) derivatives, 4-(phenyl-ethynyl)-2,2':6',2''-terpyridine (L(1)), 4-(methoxyphenyl-ethynyl)-2,2':6',2''-terpyridine (L(2)), 4-(tolyl-ethynyl)-2,2':6',2''-terpyridine (L(3)) and 4-(nitrophenyl-ethynyl)-2,2':6',2''-terpyridine (L(4)) have been used to synthesize four new [RuCl(2,2'-bipyridine)(L(n))]PF6 based complexes. Electronic absorption, resonance Raman, cyclic voltammetry and spectroelectrochemistry aided by DFT calculations were used to explore the influence of the alkynyl substituents on the electronic structures, photochemical and redox properties of the complexes. Furthermore, it is shown that the addition of ethynyl phenyl moieties to the 4-position of the tpy ligand does not have a detrimental effect on these complexes, or the analogous aqua complexes, with respect to their ability to photocatalyse the oxidation of 4-methoxybenzyl alcohol to the corresponding benzaldehyde.

Catalytic Water‐Oxidation Activity of a Weakly Coupled Binuclear Ruthenium Polypyridyl Complex

“…The electronic absorption spectra of all mono‐ and binuclear species (Figure ) exhibit similar patterns, with polypyridyl ligand localized pπ→pπ* and n→pπ* transitions below 350 nm and Ru(dπ)→pπ* metal‐to‐ligand charge‐transfer (MLCT) transitions above 350 nm. These electronic transitions were assigned in detail with the support of time‐dependent DFT (TD‐DFT) calculations (Figures S7–S12 and Tables S5–S12) by using a well‐established approach that was successfully applied to structurally related complexes of the type [Ru(L)(bpy)(tpy)] n + (L = Cl – or H 2 O, n = 0 or 1) , …”

Crystal structure of a mononuclear RuIIcomplex with a back-to-back terpyridine ligand: [RuCl(bpy)(tpy–tpy)]+

“…One of these systems is the chromophore-catalyst dyad [(tpy)Ru(tpy-tpy)Ru(bpy)-(H 2 O)] 4+ , in which the well-defined photosensitizer {(tpy)Ru(tpy)} and catalyst {(tpy)Ru(bpy)(H 2 O)} moieties are linked by the single covalent bond between the back-to-back terpyridines (tpy-tpy). In this and other related photocatalysts containing the {(tpy)Ru(bpy)(L)} moiety (L = H 2 O or Cl À ), the aqua species is typically formed by easy ligand substitution from its chlorido precursor in water (Chen et al, 2009;Davidson et al, 2015;Jakubikova et al, 2009;Li et al, 2015). Therefore, the mononuclear chlorido complex 1 reported here was initially prepared and isolated as an intermediate in the synthesis of the dinuclear precatalyst [(tpy)Ru(tpy-tpy)-Ru(bpy)(Cl)] 3+ (Chen et al, 2009).…”

Synthesis and properties of new mononuclear Ru(ii)-based photocatalysts containing 4,4′-diphenyl-2,2′-bipyridyl ligands

“…The oxidation of benzyl alcohols is a convenient approach to probing the activity of mononuclear Ru photooxidation catalysts. [39][40][41] Following the recent studies of Low and colleagues with [Ru II Cl(bpy)(tpy)] + (tpy = 2,2′:6′,2″-terpyridyl), [Ru II (H 2 O)(bpy)(tpy)] 2+ and their analogues with 4-arylethynyl substituents, 41 investigations with a selection of our new complexes and their in situ generated aquo derivatives have been carried out.…”