Photosolvolysis of cis-[Ru(α-diimine)₂(4-aminopyridine)₂]²⁺ Complexes: Photophysical, Spectroscopic, and Density Functional Theory Analysis

Abstract

The photochemical and photophysical properties of the cis-[Ru(II)(α-diimine)2(4-APy)2](2+) complexes, where α-diimine = 1,10-phenanthroline (phen) and 4-APy = 4-aminopyridine I, 4,7-diphenyl-1,10-phenanthroline (Ph2phen) II, 2,2'-bipyridine (bpy) III, and 4,4'-dimethyl-2,2'-bipyridine (Me2bpy) IV, are reported. The four complexes were characterized using high-performance liquid chromatography, (1)H NMR, UV-visible, emission, and transient absorption spectroscopy. Upon photolysis in acetonitrile solution these complexes undergo 4-APy dissociation to give the monoacetonitrile complex (for II, III, and IV) or the bis(acetonitrile) complex (for I). A fairly wide range of excitation wavelengths (from 420 to 580 nm) were employed to explore the photophysics of these systems. Quantum yields and transient spectra are provided. Density functional theory (DFT) and time-dependent DFT analysis of singlet and triplet excited states facilitated our understanding of the photochemical behavior. A detailed assessment of the geometric and electronic structures of the lowest energy spin triplet charge transfer state ((3)MLCT) and spin triplet metal centered state ((3)MC) (dπ → σ* transitions) for species I-IV is presented. A second, previously unobserved, and nondissociative, (3)MC state is identified and is likely involved in the primary step of photodissociation. This new (3)MC state may indeed play a major role in many other photodissociation processes.

Combatting AMR: photoactivatable ruthenium(ii)-isoniazid complex exhibits rapid selective antimycobacterial activity

“…S11†), in agreement with our TEAS characterization and previous experimental and theoretical work performed on analogous systems. 21,25 …”

Theoretical illumination of highly original photoreactive3MC states and the mechanism of the photochemistry of Ru(ii) tris(bidentate) complexes

“…60,62,63 It is noteworthy that the key actors involved in the mechanism for ligand photorelease from ruthenium complexes have been studied theoretically with monodentate departing ligands only, using a combination of unrestricted DFT and TD-DFT. 29,30,32,33,[67][68][69][70][71] This reaction proceeds along a rather intuitive reaction coordinate, i.e. Ru-L elongation, which can be probed by relaxed surface scans.…”

“…Ru-L elongation, which can be probed by relaxed surface scans. 29,30,32,33,69 Mechanistic studies have 6 emphasized the complexity and the multistep nature of ligand photolabilisation processes. 30,67,70,71 However, following an in-depth study of the 3 PES, we have identified new structural isomers of the 3 MC state and have shown that, in addition to bond elongation, the reaction may also involve an offset of the departing ligand from its initial coordination axis.…”

So-called “dual emission” for 3MLCT luminescence in ruthenium complex ions: What is really happening?

“…2+ complexes [50]. The monodentate ligands permit reasonably facile photosolvolysis, which is different from the work emphasized above.…”