Hyper-rayleigh scattering and two-photon luminescence of phenylamine-indandione chromophores

Based on results of quantum chemical (QC) screening, we put under research several phenylamine indane-1,3-dione derivatives including octupolar NLO chromophore A3BI. According to these calculations, molecular first hyperpolarizability (β_HRS) should be enhanced upon replacement of methyl substituents with phenyl groups. Surprisingly, β_HRS values obtained in our measurements by hyper-Rayleigh scattering (HRS) are much higher than one could expect from QC. Bearing in mind that two-photon luminescence (TPL) is usual cause for overestimation of β_HRS in HRS measurements, we have accomplished investigations of TPL properties of these compounds. All investigated triphenylamine derivatives exhibit strong TPL. In case of DANS and DMABI captured simultaneously, TPL spectra and HRS signal, reveal the least as clearly distinct on TPL background, thus TPL-free β_HRS values can be defined. Concurrently, sharp HRS signal of DPABI is sinking in TPL and background noise along with increase in concentration. Due to fairly intensive TPL for other investigated triphenylamino compounds, the HRS signal was rather indistinguishable and therefore correct β_HRS values could not be extracted.