Synthesis, linear and non-linear optical properties of “push-pull” chromophores based on 9,9-dimethyl-9H-fluoren-2-amine

Abstract

Photophysical properties including the first hyperpolarizability of a series of chromophores (SP1-SP5) possessing “push-pull” type conjugation were investigated to evaluate the proficiency as non-linear optically active materials. The compounds are based on the 9,9-dimethyl-9H-fluoren-2-amine platform, which acts as a donor unit and different types of acceptors have been incorporated to design SP1-SP5. The first hyperpolarizability (βHRS) value was in the range of 102 × 10−30 esu to 174 × 10−30 esu, and the trends in the experimental βHRS have been rationalized in terms of the difference in the dipole moment (Δμge) of the ground and excited state, oscillator strength of the contributing absorption bands and the band gaps. The intrinsic efficiency of the non-linear response of these dipolar compounds possessing a single major dipolar hyperpolarizability tensor component βzzz was also determined from the intrinsic hyperpolarizability, a real figure of merit of the non-linear optical response. Comparison of the experimental off-resonant first hyperpolarizability, βHRS, as well as the intrinsic hyperpolarizability of this set of D-π-A chromophores, lacking linear conjugation, revealed advantage over the already reported counterparts based on benzothiazole platform.