Electric-Field-Induced Second Harmonic Generation Nonlinear Optic Response of A₄ β-Pyrrolic-Substituted Zn^II Porphyrins: When Cubic Contributions Cannot Be Neglected.

ABSTRACT: In this work, we have prepared a series of A₄ Zn^II porphyrins, carrying in the β-pyrrolic-position one or two π-delocalized ethynylphenyl moieties with a -NO₂ acceptor or a -NMe₂ donor pendant, and measured their second-order NLO response in CHCl₃ solution at 1907 nm via the electric-field-induced second harmonic generation (EFISH) technique. For some of these compounds, we have recorded an unexpected sign and/or absolute value of μβ₁₉₀₇. Since their sterically hindered A₄ structure should ensure the lack of significant aggregation processes in solution, we explain such anomalous EFISH results by invoking a non-negligible contribution of the electronic cubic term γ(-2ω; ω, ω, 0) to γ_EFISH, as supported by a qualitative evaluation of the third-order response through the measure of the cubic hyperpolarizability (γ_THG) and by computational evidence.

SUBMITTER: Di Carlo G 

PROVIDER: S-EPMC8007098 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature