Solvent-dependent structural dynamics of an azido-platinum complex revealed by linear and nonlinear infrared spectroscopy

Abstract

The vibrational and anisotropic relaxation dynamics and structural dynamics of a potential anticancer prodrug, trans,trans,trans-[Pt(N3)2(OH)2(py)2], were investigated using time-resolved infrared pump-probe spectroscopy and ultrafast two-dimensional infrared (2D IR) spectroscopy. Herein, two representative bio-friendly solvents, H2O and DMSO, were used, in which the local structural and dynamical variations were monitored using the antisymmetric linear combination of the two N3 stretching vibrational modes as an infrared probe. It was found that the vibrational relaxation process of the N3 antisymmetric stretching (as) mode in H2O is two to three times faster than that in DMSO. The anisotropic relaxation process of the anticancer prodrug was observed to be hindered in DMSO; this indicated a tighter solvent environment around the sample molecule in this solvent. The vibrational frequency time correlation of the N3 antisymmetric stretching mode in H2O decays with a time constant of 1.94 ps, in agreement with the hydrogen bond formation and breaking times of water. In DMSO, the frequency time correlation of the N3 as mode decays on a much longer time scale; this further indicates its sensitivity to the out-layer DMSO structural dynamics, which are relatively static in the experimental time window.

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

“…The 2D IR spectroscopy is useful to characterize molecular structural dynamics and vibrational energy transfers on the ultrafast time scales through a network of waiting-time-dependent diagonal and off-diagonal signals. It is most common to present 2D IR spectra in the purely absorptive way, in which the 2D line-shape is phased and best frequency-resolved. − In a pump–probe geometry-based 2D IR spectrometer, the rephasing and non-rephasing signals have the same phase matching condition and are emitted along the probe beam, hence the probe self-heterodyned and purely absorptive signals in this dimension can be measured directly in the frequency domain using a monochromator, whereas the coherence dimension can be measured in the time domain using a fast scanning algorithm. , 2D IR spectra of the NO stretching mode of the Ru-NO complex in dDMSO and D 2 O at several waiting times are shown in Figure . Each 2D IR spectrum contains a pair of peaks arising from the 0–1 vibrational transition roughly on the diagonal and the 1–2 transition that is left-shifted along the horizontal frequency axis due to anharmonicity.…”

Ultrafast Intermolecular Vibrational Energy Transfer in Hexahydro-1,3,5-trinitro-1,3,5-triazine in Molecular Crystal by 2D IR Spectroscopy

“…These works demonstrated the power of the infrared methods in studying such energetic materials, particularly the 2D IR method, which is essentially a coherent and multidimensional pump–probe IR method possessing both high time resolution and high structural sensitivity and can simultaneously excite and probe many vibrational chromophores with varying frequencies in the mid-IR region . For this reason, in recent years, the 2D IR method has attracted extensive attention in the study of the structures and dynamics of condensed-phase molecular systems, as well as interface and surface molecular systems. − …”

Ultrafast Structure and Vibrational Dynamics of a Cyano-Containing Non-Fullerene Acceptor for Organic Solar Cells Revealed by Two-Dimensional Infrared Spectroscopy

“…It also shows the as–as mode (Δ ss–as ≈ 8.6 cm –1 ), which appears due to ultrafast energy transfer (i.e., intramolecular vibrational energy redistribution, IVR) from the ss–as mode to the as–as mode in the form of off-diagonal signal, actually has the diagonal anharmonicity of the energy-accepting mode (as–as). Figure a also reveals another type of off-diagonal anharmonicity that is due to AVC , between the ss–as mode and as–as mode (Δ ss–as,as–as ≈ 22.8 cm –1 ), which differs from and is significantly larger than both of the diagonal anharmonicities. From Figure b, a similar set of diagonal and off-diagonal anharmonicities are obtained at 2.5 ps waiting time (Table ), justifying the fitting results obtained from Figure a.…”