A relaxation-assisted 2D IR spectroscopy method (original) (raw)
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The Journal of Chemical Physics, 2009
Ultrafast two dimensional infrared ͑2D IR͒ spectroscopy has been applied to probe the intermolecular vibrational energy exchange between two model molecules, benzonitrile and acetonitrile-d3. The vibrational energy exchange between these two molecules is manifested through the growth of cross peaks in their 2D IR spectra. In experiments, their nitrile groups ͑CN͒ are not involved in the energy exchange but serve as reporters of the process. Our experiments demonstrate that intermolecular vibrational energy transfer can be directly probed with the 2D IR method. Results also show that the mode specific energy transfer can be important in intermolecular vibrational energy transfers.
Applied Spectroscopy, 1995
A quantitative two-dimensional correlation analysis for various spectroscopic techniques is introduced. Normalization of the spectral intensities enables two-dimensional infrared (2D IR) spectroscopy to be used for quantitative purposes. As a result of the normalization, the correlation strengths are characterized by the dynamic parameters of the correlated spectral intensities. Relationships between the chemical species associated with peak positions in 2D IR spectra are characterized by both the magnitude and the sign of the correlation strength. The magnitude describes the degree of harmonization, while the sign shows the relationship between the dynamic behaviors of the correlated spectral intensities. The phase spectrum, which indicates the quantitative relationship among the dynamic behavior of the spectral intensities, is also introduced.
The Journal of Chemical Physics, 2020
Vibrational energy transfer (VET) between two isotopologues of [Re(dcb)(CO)3Br] immobilized on a TiO2 surface is studied with the help of 2D IR spectroscopy in dependence of surface coverage. To dilute the molecules on the surface, and thereby control the intermolecular distances, two different diluents have been used: a third isotopologue of the same molecule and 4-cyanobenzoic acid. As expected, the VET rate decreases with dilution. For a quantitative investigation of the distance dependence of the VET rate, we analyze the data based on an excitonic model. This model reveals the typical 1/r6-distance dependence for a dimer of a donor and acceptor, similar to the nuclear Overhauser effect in NMR spectroscopy or Förster resonant energy transfer in electronic spectroscopy. However, VET becomes a collective phenomenon on the surface, with the existence of a network of coupled molecules and its disappearance below a percolation threshold, dominating the concentration dependence of the VET rate.
Instrumental aspects of dynamic two-dimensional infrared spectroscopy
Applied Spectroscopy, 1993
Dynamic two-dimensional infrared (2D IR) correlation maps are a convenient means of examining the information contained in time-resolved IR spectra. Dynamic 2D IR spectra can be collected with the use of either dispersive or Fourier transform (FT) IR spectrometers. Use of a step-scanning FT-IR spectrometer has advantages over conventional rapid-scan FT-IR spectrometry when one is acquiring time-resolved IR data on time scales faster than about 0.1 s, because the spectral multiplexing is removed from the time domain. Dynamic IR spectra of atactic polystyrene (undergoing a small-amplitude oscillatory strain) collected on both dispersive and FT instrumentation are compared. Although the dispersive approach produces higher signal-to-noise ratios over small spectral regions, the multiplex advantage makes the FT approach attractive when broader spectral coverages are required. The first vibrational circular dichroism (VCD) spectrum [of (-)-a-pinene] collected on a step-scanning interferometer is also presented.
Two-dimensional infrared (2D IR) spectroscopy. A new tool for interpreting infrared spectra
Mikrochimica Acta, 1988
Two-dimensional infrared (2D IR) spectroscopy is used to study atactic polystyrene. 2D IR is a technique based on time-resolved detection of IR signals in response to an external perturbation, such as mechanical strain. Since different chemical functional groups respond to the applied perturbation at unique and often different rates, characteristic time-dependent variations of the IR-band intensities are observed. Correlation analysis of the dynamic variation of the IR signals yields a new spectrum defined by two independent wave numbers. Peaks located on a 2D IR spectral plane imply interactions and connectivities among chemical functional groups. By spreading convoluted IR bands over two dimensions, the spectral resolution is also greatly enhanced.
Ultrafast N–H vibrational dynamics of hydrogen-bonded cyclic amide reveal by 2DIR spectroscopy
Chemical Physics, 2018
Hydrogen-bonding strongly influences the vibrational dynamics of the N-H stretch vibration, hence the molecular structure and dynamics. Therefore the N-H stretch vibration is an important probe to study hydrogen-bond dynamics as well as the molecular structure and dynamics, specially for the biological molecule. In this article, the dynamics and couplings of N-H stretching vibrations of biological molecules are investigated with linear infrared spectroscopy and ultrafast two-dimensional infrared (2DIR) spectroscopy with a model molecule 2-Pyrrolidinone. In solution, 2-Pyrrolidinone makes three different kinds of intermolecular hydrogen bonding, whose spectra have been collected with FTIR as well as with 2DIR spectroscopy and discussed. Inter-molecular hydrogen bond making and breaking between N-H and C]O vibrational bands are discussed also.
Scalable Computing: Practice and Experience, 2018
In the present study, a molecular dynamics study of irinotecan molecule with the atom-centered density matrix propagation scheme was carried out at AM1 semiempirical level of theory, at series of different temperatures, ranging from 5 K to 300 K. Molecular dynamics simulations were performed within the NVE ensemble, initially injecting (and redistributing among the nuclei) various amounts of nuclear kinetic energies to achieve the desired target temperatures. Subsequently to initial equilibration phase of 2 ps, productive simulations were carried out for 8 ps. The accuracy of simulations and the closeness of the generated trajectory to those at the Born-Oppenheimer surface were carefully followed and analyzed. To compute the temperature-dependent rovibrational density of states spectra, the velocity-velocity autocorrelation functions were computed and Fourier-transformed. Fourier-transformed dipole moment autocorrelation functions were, on the other hand, used to calculate the temperature-dependent infrared absorption cross section spectra. The finite-temperature spectra were compared to those computed by a static approach, i.e. by diagonalization of mass-weighted Hessian matrices at the minima located on the potential energy surfaces. Thermally-induced spectral changes were analyzed and discussed. The advantages of finite-temperature statistical physics simulations based on semiempirical Hamiltonian over the static semiempirical ones in the case of complex, physiologically active molecular systems relevant to intermolecular interactions between drugs and drug carriers were pointed out and discussed.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2019
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Broadband two dimensional infrared spectroscopy of cyclic amide 2-Pyrrolidinone
Physical Chemistry Chemical Physics, 2015
In the past one-and-a-half decade there has been a significant methodological and technological development of two dimensional infrared (2DIR) spectroscopy, which unfolds many underlying physical and chemical processes of complex molecules, especially for biological molecules.
Computational Vibrational Spectroscopy of Hydrophilic Drug Irinotecan
2016
A computational study of structural and vibrational spectroscopic properties of hydrophilic drug irinotecane was carried out. Both static and dynamical approaches to the problem have been implemented. In the static ones, vibrational spectra of the title system were computed within the double harmonic approximation, diagonalizing the mass-weighted Hessian matrices. These were calculated for the minima on AM1, PM3, PM6 and B3LYP/6-31G(d,p) potential energy surfaces. Within the dynamical approach, atom-centered density matrix propagation scheme was implemented at AM1 level of theory. From the computed molecular dynamics trajectories at series of temperatures (ranging from 10 to 300 K), velocity-velocity autocorrelation function was calculated and the vibrational density of states was sequentially obtained by Fourier transformation. Comparison with the experimental data revealed that the employed density functional level of theory exhibited remarkable performances. Of all semiempirical ...