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

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-9 H -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 ( β HRS ) value was in the range of 102 × 10 −30  esu to 174 × 10 −30  esu, and the trends in the experimental β HRS have been rationalized in terms of the difference in the dipole moment (Δμ ge ) 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 β zzz 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, β HRS, 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.