Insights into the optoelectronic, quantum chemical, NBO and dynamic nonlinear optical properties of meso-BODIPY dyes

Herein, understanding the effect of substituents on the electronic absorption, optoelectronic, static and dynamic nonlinear optical (NLO) properties, and molecular stability of (CF₃-, CH₃-, CCl₃-, NH₂-, NO₂-) meso-substituted BODIPY dyes was specifically aimed at using density functional (B3LYP and CAM-B3LYP) approach with 6–311++G(d,p). Solvent perturbation of electronic excitation energy, oscillator strength and light-harvesting efficiency (LHE) was observed. The LHE increased from 74–80% in gas to 87–90% in acetonitrile. The static first-order and second-order (β, γ) NLO properties of the dyes were significantly greater than those of urea (a standard NLO material). Interestingly, the dynamic NLO [electro-optic Pockels effect: β(-ω;ω,0); second harmonic generation (SHG): β(-2ω;ω,ω); electro-optic Kerr effect: γ(-ω;ω,0,0); direct current SHG: γ(-2ω;ω,ω,0)] at ħω = 0.042823 au were greater than the static β and γ (ħω = 0). NO₂- substituted dye presented greatest NLO amplitudes. Natural bond orbital (NBO) analysis identified conjugative and hyperconjugative interactions as the major contributors to the structural stabilization of the dyes. Except for NO₂-dye, a negative free energy for electron injection and a positive open-circuit voltage were observed indicating good optoelectronic potential of the substituted BODIPY in dye sensitized solar cells. The molecular instability, chemical reactivity (from energy gap) and dynamic NLO response of the dyes increased in the order: NH₂- < CH₃- < CF₃- < CCl₃ < NO₂-.