Doubly resonant three-wave-mixing spectroscopy of a chiral coupled-chromophore system in solution: Coherent two-dimensional optical activity spectroscopy

Abstract

Theoretical descriptions of doubly resonant two-dimensional (2D) sum-frequency-generation (SFG) and difference-frequency-generation (DFG) spectroscopies of coupled-chromophore systems are presented. Despite that each electronic or vibrational chromophore is achiral, the interaction-induced chirality of a coupled multichromophore system in solution can be measured by using the doubly resonant 2D three-wave-mixing (3WM) spectroscopic method. An electronically coupled dimer, where each monomer is modeled as a simple two-level system, can have nonvanishing SFG (or DFG) properties, e.g., susceptibility in frequency domain or nonlinear response function in time domain, if the induced dipole vector of the dimer is not orthogonal to the vector product of the two monomer electronic transition dipole vectors. In order to demonstrate that these 2D 3WM spectroscopic methods can be used to determine the solution structure of a polypeptide, the authors carried out quantum chemistry calculations for an alanine dipeptide and obtained first- and second-order dipole derivatives associated with the amide I vibrational transitions of the dipeptide. It is shown that the numerically simulated 2D IR-IR SFG spectrum is highly sensitive to the dipeptide secondary structure and provides rich information on the one- and two-exciton states. It is believed that the theoretically proposed doubly resonant 2D 3WM spectroscopy, which can be considered to be an optical activity spectroscopy, will be of use in studying both structural and dynamical aspects of coupled multichromophore systems, such as proteins, nucleic acids, nanoparticle aggregates etc.

Vibrational Sum-Frequency Generation Spectroscopy at the Water/Lipid Interface: Molecular Dynamics Simulation Study

“…70 Cheon et al pointed out that the 2D technique with the even-order susceptibility carries information on the chiral couplings. 75 The surface-specific 2D experiment was conducted on the model membrane system by using the IR-IR-IR-Visible pulse configuration. 76,77 The applications of these surface-specific 2D techniques to the water/lipid interface will provide a new experimental tool for probing the information on the intermolecular coupling of interfacial water.…”

Two-dimensional nonlinear optical activity spectroscopy of coupled multi-chromophore system

“…Recently, it was shown that the numerically simulated 2D IR-IR SFG spectrum is highly sensitive to the peptide secondary structure including dipeptide and polypeptides. 25,26 In this paper, we shall also show that the 2D IR-IR SFG spectroscopy can be of use to distinguish conformational difference between an anti-parallel b-sheet and a parallel b-sheet. 26 To demonstrate the usefulness of 2D IR-IR SFG, we considered three representative helical structures, i.…”

“…Recently, novel 2D optical spectroscopic methods using circularly polarized beams were theoretically proposed and shown to be useful in measuring the nonlinear optical activity of chiral molecules in an isotropic medium. [23][24][25][26][27][28][29][30] It has been known that the three-wave mixing (3WM) is the lowest-order nonlinear optical response of a molecular system on surface or at interface where the centrosymmetry is broken. [31][32][33][34] Shen and coworkers [35][36][37][38][39][40][41][42][43] showed that the IR-vis (IV) SFG spectroscopy is an incisive surface-specific vibrational spectroscopy, where the IR pulse is used to create vibrational coherence state and the electronically non-resonant visible pulse is Raman-scattered to generate the IR+vis sum frequency field.…”

“…As an extension of this surface 2D vibrational spectroscopy, we showed that the 2D IR-IR 3WM spectroscopic signal does not vanish if the solute molecule in solution is chiral and that the 2D IR-IR SFG spectrum depends on the secondary structure of polypeptide. 25,26 In parallel with the development of 2D doubly-resonant 3WM spectroscopy, we have theoretically shown that the socalled 2D circularly polarized pump-probe (CP-PP) and circularly polarized photon-echo (CP-PE) spectroscopy, [27][28][29][30] where a circularly polarized beam is used, are 2D optical activity measurement techniques. In practice, the difference between the left-and right CP-PP and CP-PE spectra should be measured and the difference signal was found to be dependent on the magnetic dipole-magnetic field interaction as well as on the electric quadrupole-electric field interaction strength.…”

“…The SFG measurement in time domain by using two temporally narrow pulses and by employing a heterodynedetection method has been mainly considered recently. The double Fourier transformation of the nonlinear response function is then related to the 2D SFG spectrum in the impulsive limit, i.e., 25…”