Zhang Wei, Cozzolino Anthony F, Mahmoudkhani Amir H, Tulumello Mark, Mansour Sarah, Vargas-Baca Ignacio
Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada.
J Phys Chem B. 2005 Oct 6;109(39):18378-84. doi: 10.1021/jp053142u.
The wavelength-dependent second-harmonic generation (SHG) efficiency of two simple dipolar chromophores, 4-NO2C6H4N(H)Bun (1) and 4-NO2C6H4SN(H)But (2), was compared in solution and in the solid state. Hyper-Rayleigh scattering measurements at 532 nm provided comparable molecular first hyperpolarizabilities. Both compounds crystallize in non-centrosymmetric space groups, but a more efficient arrangement of dipole moments results in a significantly larger deff value for 2. Kurtz-Perry experiments from 450 to 700 nm revealed an important difference in the resonant component of the nonlinear optical responses of these compounds; the SHG efficiency of crystalline 1 depends more strongly on the incident wavelength than that of 2. This would be in contradiction with the TD-DFT excitation energies calculated for these molecules, but the observation can be explained by the resonant contribution from low-energy interchromophore excitations enabled by pi-stacking in the crystal of 1.
比较了两种简单的偶极发色团4-NO₂C₆H₄N(H)Bun（1）和4-NO₂C₆H₄SN(H)But（2）在溶液和固态中的波长依赖性二次谐波产生（SHG）效率。在532 nm处的超瑞利散射测量提供了相当的分子第一超极化率。两种化合物都结晶于非中心对称空间群中，但更有效的偶极矩排列导致化合物2的有效d值显著更大。在450至700 nm范围内进行的库尔茨-佩里实验揭示了这些化合物非线性光学响应的共振成分存在重要差异；晶体1的SHG效率比化合物2对入射波长的依赖性更强。这与为这些分子计算的含时密度泛函理论（TD-DFT）激发能相矛盾，但该观察结果可以通过1的晶体中π堆积使低能发色团间激发产生的共振贡献来解释。
