Exploring the two-photon absorption response in short π-chain organic compounds: Hydrazones and pyrazolines derivatives

We compared the experimental two-photon absorption spectra of two hydrazone derivatives of chalcone (HDC-1 and HDC-2) and two pyrazoline derivatives of dibenzylideneacetone and chalcone (PD-1 and PD-2). The compounds were synthesized by the Claisen-Schmidt reaction and characterized using NMR, FTIR, and UV–Vis. Using femtosecond pulses, the Z-scan technique recorded two-photon absorption cross-section (σ2PA) spectra of the investigated compounds, which presented values of σ2PA, ranging from ∼12 GM to ∼50 GM. Such σ2PA difference is generally associated with the conjugated chain length and the different functional and peripherical groups used. For example, increasing the π-chain and peripherals donor groups p-OCH3 from HDC-1 to HCD-2 led to a change in the σ2PA magnitude (σHDC−12PA∼35GM, σHDC−22PA∼50GM). The modification on the pyrazoline derivatives, i.e., increasing the conjugated chain and adding p-OCH3 in both phenyls in the PD-2 compared to compound PD-1 doubled the σ2PA magnitude (σPD−12PA∼12GM, σPD−22PA∼22GM). According to the obtained results and considering the investigated compounds' short π-chain, we could claim that these classes of organic molecules promise nonlinear optical materials for optical limiting due to optical transparency ranging from 450 nm for pyrazolines to 550 nm for hydrazone derivatives. •Short π-Chain Organic Compounds: Hydrazones have N=N bonds and aromatic rings; pyrazolines have a 5-member nitrogen ring.•Z-Scan Technique: using femtosecond pulses under 100 μW to accurately characterize the two-photon absorption spectra.•Molecular Structure Impact: affect their two-photon absorption, ranging from 12-50 GM.•PotentialPhotonic Applications: Hydrazones and pyrazolines show potential in optical limiting devices.