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

Abstract

In this work, the photoisomerization and structural dynamics of two isomeric nitrosylruthenium(ii) complexes [Ru(OAc)(2cqn)2NO] (H2cqn = 2-chloro-8-quinolinol) in CDCl3 and DMSO are examined using NMR and IR spectroscopic methods. The two N atoms in the 2cqn ligand are in trans position in the synthesized cis-1 isomer, while they are in cis position in the cis-2 isomer. Kinetics monitored by NMR spectroscopy shows that the rate constant of photoisomerization from cis-2 to cis-1 isomer depends on the wavelength of irradiation and solvent polarity; it proceeds faster on irradiating near the absorption peak in the UV-Vis region, and also in more polar solvents (DMSO). Density functional theory computation indicates that the peculiarity of [Ru(ii)-NO(+)] group affects the structure and reactivity of the nitrosylruthenium complexes. Using the nitrosyl stretching (νNO) to be vibrational probe, the structural dynamics and structural distributions of the cis-1 and cis-2 isomers are examined by steady-state linear infrared and ultrafast two-dimensional infrared (2D IR) spectroscopies. The structural and photochemical aspects of the observed spectroscopic parameters are discussed in terms of solute-solvent interactions for the two nitrosylruthenium complexes.

Structural dynamics of nitrosylruthenium isomeric complexes studied with steady-state and transient pump-probe infrared spectroscopies

“…The results show that the T 1 time of the NO stretching vibrational state relaxes on the order of 7-10 ps, showing less than 30% variation from one isomer to another. It is well known that vibration energy relaxation involves both intramolecular and intermolecular energy-dissipation channels [28], the former is usually called intramolecular vibration redistribution (IVR) and the latter is called intermolecular vibrational energy relaxation (IVE). In the present case, the vibrational energy of excited NO stretching most likely relaxes through IVE, thus how the NO group interacts with solvent should be important.…”

“…The original coordinates of atoms in the cis-1, cis-2 and trans isomeric complexes were obtained from the crystal structures determined with X-ray diffraction [26][27][28][29][30][31]. Visualization was performed with GaussView 5.0 [33].…”

“…In our recent work, ultrafast two-dimensional infrared (2D IR) spectroscopy has been used to characterized spectral diffusion time, a key parameter for equilibrium structural dynamics that is closely associated with the frequency time-correlation function, of the [Ru(OAc)(2cqn) 2 NO] (H2cqn = 2-chloro-8-quinolinol) isomers in solution phases [28].…”

Linear and Nonlinear Infrared Spectroscopies Reveal Detailed Solute–Solvent Dynamic Interactions of a Nitrosyl Ruthenium Complex in Solution

“…In our recent works, − a similar Ru-NO complex with cis and trans configurations has been examined using ultrafast IR spectroscopies. It was found that nonlinear IR signatures (spectral line width, dynamical parameters), especially those extracted from 2D IR spectra, can be used to differentiate the cis and trans configurations .…”

Synthesis, Biomacromolecular Interactions, Photodynamic NO Releasing and Cellular Imaging of Two [RuCl(qn)(Lbpy)(NO)]X Complexes

“…The light irradiation time was 60 min in the wavelength of 420 nm filter and 30 min with Xe lamp. The quantum yield of two complexes were estimated at the wavelength of λ = 420 nm according to the equation: Φ 420 nm = n N A h c/E λ (where n was the number of reactant molecules in mol, N A was Avogadro constant, h was Plank constant, c was the speed of light and E was the absorbed photon energy), in which the absorbed photon energy was obtained by the formula E = I t S T (I was the power density of incident light; t was the time; S was the effective absorption area; T was the transmittance) [ 56 ].…”