Second-Order Optical Nonlinearity of Two 1,3,4-Oxadiazole Derivatives: an Experimental and Theoretical Study

Measurements and theoretical modeling of the second-order optical nonlinearity of 2-(4-(dodecyloxy)phenyl)-5-(pyridin-3-yl)-1,3,4-oxadiazole (Oxa-4-Py) and 2-(4-(dodecyloxy)phenyl)-5-(4-(5-(thiophen-2-yl)-1,3,4-oxadiazol-2-yl)phenyl)-1,3,4-oxadiazole (DiOxaBn-2-Tio) are reported here. The hyper-Rayleigh scattering technique was applied to measure the dynamic first hyperpolarizability, βexpλ=1064, of the samples. The excitation source was a Nd:YAG laser operating at 1064 nm, 6 ns and 10 Hz, and a two-level approximation was applied to estimate the static first hyperpolarizability, βexpλ=0, of the samples. The obtained values for βexpλ=1064 were 173×10−30 esu (Oxa-4-Py) and 226×10−30 esu (DiOxaBn-2-Tio), and the calculated values for static first hyperpolarizability, βexpλ=0 were 106×10−30 esu (Oxa-4-Py) and 126×10−30 esu (DiOxaBn-2-Tio). The βexpλ=1064 value determined for the DiOxaBn-2-Tio is among the largest experimental values reported so far for a 1,3,4-oxadiazole derivative. The calculations based on a density functional method confirmed the trend of the βexpλ=1064 values among the samples, i.e. the first hyperpolarizability of DiOxaBn-2-Tio is approximately 30% larger than βexpλ=1064 for Oxa-4-Py.