Homoleptic Ruthenium Complexes Research Articles

Two-Photon Absorption Cooperative Effects within Multi-Dipolar Ruthenium Complexes: The Decisive Influence of Charge Transfers.

One- and two-photon characterizations of a series of hetero- and homoleptic [RuL3-n(bpy)n]2+ (n = 0, 1, 2) complexes carrying bipyridine π-extended ligands (L), have been carried out. These π-extended D−π−A−A−π−D-type ligands (L), where the electron donor units (D) are based on diphenylamine, carbazolyl, or fluorenyl units, have been designed to modulate the conjugation extension and the donating effect. Density functional theory calculations were performed in order to rationalize the observed spectra. Calculations show that the electronic structure of the π-extended ligands has a pronounced effect on the composition of HOMO and LUMO and on the metallic contribution to frontier MOs, resulting in strikingly different nonlinear properties. This work demonstrates that ILCT transitions are the keystone of one- and two-photon absorption bands in the studied systems and reveals how much MLCT and LLCT charge transfers play a decisive role on the two-photon properties of both hetero- and homoleptic ruthenium complexes through cooperative or suppressive effects.

Synthesis, crystal structures, photophysical, electrochemical studies, DFT and TD-DFT calculations and Hirshfeld analysis of new 2,2′:6′,2′′-terpyridine ligands with pendant 4′-(trimethoxyphenyl) groups and their homoleptic ruthenium complexes

[Ru(L1)2](PF6)2 (1) and [Ru(L2)2](PF6)2 (2): X-ray structures, CH⋯F/O, OH⋯F/N, CH⋯O/π, π⋯π interactions, absorption and emission spectra, DFT/TD-DFT, Hirshfeld analysis.

Homoleptic ruthenium complexes with N-heterocyclic carbene ligands as photosensitizers in the photocatalytic generation of H2 from water

There is great interest in the catalytic photoreduction of water to give hydrogen as a fuel to harness solar energy and a series of ruthenium complexes has been synthesized and tested as photosensitizers in this photoreduction process. There are very few precedents for N-heterocyclic carbene complexes in this field. The complexes obtained in this work were of the type [Ru(:CˆNˆC:)2](PF6)2 and [Ru(NˆC:)3](PF6)2 with N-heterocyclic carbene ligands derived from pyridine and imidazole heterocycles with methyl or benzyl substituents. The photophysical properties of the complexes were studied. Some complexes were luminescent and, although the quantum yields were rather low, the lifetimes were quite high (1.5–1.7 μs). The emissive complexes behave as photosensitizers in the generation of H2 using [Co(bpy)3]Cl2 (bpy = 2,2′-bipyridine) as catalyst and triethanolamine (TEOA) as the sacrificial reductant through an oxidative quenching mechanism. The amount of hydrogen obtained was higher for the benzyl derivative.

Ruthenium Complexes Bearing Unsymmetric CNC′ Pincer Ligands: Molecular Structures and Electronic Properties

Homoleptic ruthenium complexes [Ru(Ln)2]2+ bearing unsymmetric pyridine-based bis N-heterocyclic carbene (NHC) pincer ligands are synthesized and structurally characterized. These complexes feature the coexistence of a five-membered and a six-membered ruthenacycle within the same ligand framework, allowing an ideally octahedral CNHC–Ru–NPy bite angle close to 90°. In the solid state, impressive 3MLCT lifetimes of microsecond regime were detected in all of the complexes, of which [Ru(L4)2]2+, featuring four benzimidazol-2-ylidene donors, exhibited the longest values. Electronic properties of all of the ruthenium complexes are investigated by cyclic voltammetry and spectroscopic techniques. Density functional theory results were used to support the experimental observations.

Ruthenium(II) complexes containing novel asymmetric tridentate ligands: synthesis, structure, electrochemical and spectroscopic properties

Three novel asymmetrical tridentate ligands, 3-(1,10-phenanthrolin-2-yl)-5,6-diphenyl-as-triazine (dppt), 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f ]acenaphthylene (pta) and 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f ]phenanthrene (ptp) have been prepared. Their homoleptic ruthenium complexes [Ru(L)2]2+ (L = dppt, pta or ptp) and heteroleptic ruthenium complexes [Ru(tpy)(L)]2+ have been synthesized and characterized by 1H NMR, ES-MS, electronic absorption spectroscopy and cyclic voltammetry. The heteroleptic ruthenium complexes were also characterized by X-ray crystallography. The electrochemical and spectroscopic studies of the complexes display the changes in properties in comparison with [Ru(tpy)3]2+ owing to the structural differences.