Optical poling effect and optical absorption of cyan, ethylcarboxyl and [formula omitted] -buthyl derivatives of 1H-pyrazolo[3,4-b]quinoline: experiment and quantum–chemical simulations

Abstract

We present here results of experimental studies and quantum–chemical simulations of optical absorption and optical poling effects performed on a new synthesized cyan, ethylcarboxyl and t e r t -buthyl derivatives of 1H-pyrazolo[3,4-b]quinoline incorporated into polymer matrix or dissolved in organic solutions. The efficiency of second-order optical susceptibility d vs photoinduced power density I p clearly saturates to certain magnitude d eff at sufficient power densities ( I p ≥ 1.3 GW cm −2). Comparing experimental data and results of semiempirical quantum–chemical simulations one can conclude that there exists generally a good correlation between the magnitude of saturated susceptibilities d eff and macroscopic hyperpolarizabilities for all compounds except the chromophore 1,3-dimethyl-6-cyano-[PQ] only. The discrepancy for this compound may reflect a specific contribution of surrounding polymer matrix. According to the quantum chemical analysis the methyl-containing cyan and ethylocarcoxyl derivatives reveal four/five strong absorption bands in the spectral range 200–500 nm. A substitution of the methyl groups by the phenyl group causes the substantial changes of the absorption spectra mainly in the spectral range 240–370 nm. Measured and calculated absorption spectra manifest rather good agreement mainly in the part regarding the spectral positions of the first oscillator (absorption threshold). The quantum–chemical PM3 method shows the best agreement with experiment. At the same time a considerable broadening almost of all absorption bands appears as a characteristic feature of all measured spectra. The discrepancies between the calculated and the measured spectra are attributed to electron–vibronic coupling as well as to a specific rotational dynamics of phenyl rings.