Second-Order Hyperpolarizabilities of Stilbazolium Cations Studied by Semiempirical Calculation

Abstract

Second-order hyperpolarizabilities (β), electron distribution, dipole moment, and excitation energy together with oscillator strength of stilbazolium cations have been investigated by a semiempirical calculation with PM3 parametrization of the MNDO Hamiltonian. Since stilbazoliums were found to generally have several times larger β value than nitrostilbene derivatives with similar experimental absorption maximum wavelength, such ionic species are concluded to be advantageous to create new second-order nonlinear optical materials having large β and short cutoff. Among the stilbazolium derivatives investigated, the β values increase with increasing electron-donating ability of the substituent at the para position of benzene ring, and exceptionally chlorinated one was found to have comparatively large β value withstanding its short absorption maximum wavelength. The main reason for the large β values of stilbazolium cations is the strong acceptor property of the pyridinium ring resulting in large difference in dipole moment between the ground and excited states, which could be shown using the two-level model. The tendency of calculated β values of stilbazolium cations shows good agreement with that obtained from the hyper Rayleigh scattering (HRS) measurement.

Determination of the Hyperpolarizability Components of Hemicyanine Dyes by Measuring the Anisotropic Fluorescence and Second Harmonic of the Dyes Uniformly Aligned within Zeolite Channels

“…[8][9][10] On the other hand, there have been several calculations carried out to find out the hyperpolarizability components in model nonlinear optical molecule of p-nitroaniline. [11][12][13] For example, Lalama and Garito calculated the frequency dependence of the hyperpolarizability components of p-nitroaniline, and they found out that zzz and zxx of hyperpolarizability components dominated near resonance, with zxx / zzz ∼ -0.…”

Theoretical study of solvent effect on the structure, first electronic excited state, and nonlinear optical properties of substituted stilbazolium cations

“…It should be notified that the HR scattering hyperpolarizability measurement for Cation 8 was also carried out by Coe et al [33]. The reported hyperpolarizability (β 0 = 25 × 10 −30 esu) significantly differs from the results of Duan et al [5,6,8] (Fig. 3).…”

Development of DAST-derivative crystals for terahertz waves generation

“…This means that the crystal has a favorable noncentrosymmetric packing arrangement. The same cation as DAST with high first hyperpolarizability [19] is considered to contribute to the high second-order nonlinearity of BDAS-TP. Fig.…”

“…Therefore, new NLO materials are desired in order to generate THz waves that cover the spectral range of 0.5-3 THz without absorption. Although several DAST derivative compounds with large NLO properties have been reported [16][17][18][19], there have been few investigations into the crystallization and THz generation [16,20].…”