Solvent effect on the first hyperpolarizabilities of conjugated organic molecules

Abstract

The frequency dependent first hyperpolarizabilities βvec(−2ω;ω,ω) (second harmonic generation) of conjugated molecules are studied using the time-dependent Hartree–Fock theory with the inclusion of solvent effects treated with the self-consistent reaction field theory. Using the intermediate neglect of differential overlap model parametrized for spectra we obtain a plot of βvec(theory) vs βvec(expt) with a fitted slope of 1.07 when solvent effects are included and only 0.49 when the solvent effects are not included. The calculated dependence of βvec on the degree of conjugation for the (−OCH3,−NO2) series of molecules that we study is 2.1 compared to 2.2 obtained from experiment, and for the [−N(CH3)2,−NO2] series of molecules a calculated value of 1.9 is obtained compared to the 1.9 value obtained from experiment.

Computer simulation of the linear and nonlinear optical properties of liquid benzene: Its local fields, refractive index, and second nonlinear susceptibility

“…15 Therefore, in order to compare directly experimental and calculated hyperpolarizabilities, there is a need to establish quantitative relations between the macroscopic material properties measured in experiments and the molecular properties obtained from quantum chemical work. Attempts to accomplish this have been undertaken by Willets and Rice 16 and Yu and Zerner, 17 who have tried directly to incorporate the effect of the environment of a molecule into ab initio calculations via a reaction field approach.…”

“…Currently, it is believed that this effect may increase the first hyperpolarizability by a factor of 2 or more relative to the gas phase, with serious consequences on properties. [16][17][18][19] The objective of the work presented in this paper was to establish a quantitative relation between the macroscopic and molecular NLO properties of a molecular liquid and to assess the magnitudes and orientations of the local electric fields experienced by the molecules in such a liquid. Liquid benzene has been chosen as a test case, because of its relative simplicity and the fact that it has been studied extensively both by optical experiments and by simulations.…”

Time-dependent variational principle for nonlinear Hamiltonians and its application to molecules in the liquid phase

“…Cammi and Tomasi [3, 41 followed the opposite approach, showing that the variational optimization of the complete energy functional, 55', expressed in quantum mechanical terms, leads to the definition of a Schrodinger equation based on a Hamiltonian of type (1). Analogous considerations have been expressed by other authors [5-71: Explicit formulas for a multipole expansion of V(*) have recently been given by Angy5n [ 8 ] .…”

“…If H o is the Hamiltonian of the isolated molecule, the effective Hamiltonian has an expression that in the simpler cases may be written in the following form: (1) n efficient approach to the study of molecu-A lar systems in a condensed phase is based on the use of effective molecular Hamiltonians. These…”

The iterative self‐consistent reaction‐field method: The refractive index of pure water

“…Much effort has gone into devising methods from which linear and nonlinear molecular optical properties can be obtained [25,26,29,[56][57][58][59][60][61][62][63][64][65][66][67][68][69], the interest being driven by the vast and growing area of experimental laser studies of solutions and liquids. Refinements in the representation of the surrounding medium have focused mainly on aspects such as the cavity geometry, radial dependence of the dielectric constant, and effects of inertial polarization [21,23,24,27,29].…”