cis–trans Photoisomerization in [Ru(DIP)₂(MeOH)₂][OTf]₂: synthesis, NMR, X-ray structure of the trans-isomer and photophysical properties

Abstract

The first trans-ruthenium complex trans-[Ru(DIP)2(MeOH)2][OTf]2 (1b, where DIP = 4,7-diphenyl-1,10-phenanthroline) incorporating a pi-extended ligand was prepared via two methods: either photolysis of cis-[Ru(DIP)2(OTf)2] in MeOH-Et(2)O or via crystallization from MeOH-Et(2)O in direct sunlight. The X-ray molecular structure of is reported and confirmed the trans geometry of the title compound. The cis-trans isomerization process was monitored by 1H-NMR and showed that 1b reverts back to cis-[Ru(DIP)2(MeOH)2][OTf]2 (1a) in methanol-d4 after 15 h at 55 degrees C or several days at room temperature. The absorption spectra recorded in MeOH showed a bathochromic shift of the MLCT band of the trans-isomer 1b relative to that of the cis complex 1a. Interestingly at 77 K the emission spectrum of 1b is red shifted compared to the cis analog 1a. A rational explanation in terms of the energy of the excited states in the cis- and trans-isomers is proposed to explain this behavior.

A Mesoionic Carbene as Neutral Ligand for Phosphorescent Cationic Ir(III) Complexes

“…This is also reflected in a less pronounced hypsochromic shift when lowering the temperature from 298 to 77 K. Moreover, it should be stressed that, at low temperature, also the emission spectrum of 3 displays a pronounced vibronic structure with the main progression displaying a frequency similar to that observed for 5 (i.e., 1441 vs 1358 cm –1 ; see Figure S12). Such vibrational frequency can be associated with the aromatic CC stretching of the mesoionic carbene ligands, indicating that the emitting state is probably a 3 LC state in both complexes, not involving the ancillary ligands …”

Photoisomerization and structural dynamics of two nitrosylruthenium complexes: a joint study by NMR and nonlinear IR spectroscopies

“…[1][2][3] Among them, the photo induced isomerization is a special reaction that has application potentials. [4][5][6] Photomodulated isomers can represent the '0' and '1' of digital codes homologous to the 'on' and 'off' states, respectively. The molecular devices based on photoisomerization enable the storage of information at the molecular level, which has the potential to significantly influence the development of optoelectronics, sensing, as well as information technologies.…”

Photophysical properties of metal complexes

“…93 The complex [Ru(NN) 2 (MeOH) 2 ] 2+ (NN = 2,7-diphenylphen) undergoes a cis-trans photoisomerisation process; the emission spectrum of the trans-isomer is red-shifted compared to the cis-isomer which is rationalised in terms of the excited state energies. 94 A family of Ru(II) complexes containing substituted 1,10-phenanthroline ligands with extended conjugation, [Ru-(bpy) 2 (L 15 )] 2+ , unusually display two simultaneously emissive 3 MLCT excited states in solutions at room temperature, originating from bpy-based (t = 0.9 to 2.2 ms) and longer lived phen(L 15 )-based (t = 3.7 to 11.5 ms) excited states. 95 Visible light decomposition of NH 3 to N 2 in a photocatalyst aqueous solution based on a photoelectron relay system of either sensitiser [Ru(bpy) 3 ] 2+ /K 2 S 2 O 8 or [Ru(bpy) 3 ] 2+ /methyl viologen dichloride/O 2 was investigated using absorption spectroscopy and gas chromatography analysis.…”