Nonlinear optical response of some Boron-dipyrromethene dyes: An experimental and theoretical investigation

Abstract

The nonlinear optical properties of a functional Boron dipyrromethene (BODIPY) derivative, namely BODIPY 1, and its subsequent formed supramolecular romboidal cavitand BODIPY 2(OTf)4, formed by mixing 1 with the 90° platinum triflate Pt(dppp)(OTf)2 linker, were investigated under femtosecond (fs) and picosecond (ps) laser excitation conditions, using the Z-scan (50 fs, 800 nm and 35 ps, 532/1064 nm) and Optical Kerr effect (OKE) (50 fs, 800 nm and 35 ps, 532 nm) techniques. Both BODIPYs exhibited strong nonlinear refractive response (self-defocusing) under both excitation conditions, while they exhibited negligible nonlinear absorptive response under ps excitation and significant reverse saturable absorption under fs excitation. The nonlinear optical response of 2(OTf)4 was found importantly increased compared to 1 under both excitation regimes, due to the more dense electronic spectrum of the BODIPY-metal derivative. The experimental results are compared and discussed with the results obtained from theoretical computations performed using Density Functional Theory (DFT). In fact, the theoretical study showed that the polarization character of the BODIPY unit can be tuned upon functionalization. The theoretical calculations were found to be qualitatively in good agreement with the experimental results, predicting successfully the larger second hyperpolarizability of 2(OTf)4. The present findings are discussed and compared with the results from other similar studies in the literature.