An insight into structural, spectroscopic and nonlinear optical Application of a promising malononitrile derivative: (Z)-2-(3-chloro-3-(4-chlorophenyl)allylidene)malononitrile

Abstract

Conjugated organic single crystals play a pivotal role as donor-acceptor molecules, showcasing nonlinear optical properties due to their unique molecular structure. In the present study, a novel functionalised allylidene malononitrile derivative, (Z)-2-(3-chloro-3-(4-chlorophenyl)allylidene)malononitrile, was synthesised and subjected to various spectroscopic and structural analyses for its optical and structural characterisation. This compound serves as an essential building block in developing photonic and optoelectronic materials. We synthesised the compound through a Vilsmeier-Haack reaction followed by a Knoevenagel condensation reaction and crystallised it using a slow evaporation method. In addition to SCXRD, the structural analysis of the compound was performed using NMR (1H, 13C), mass spectroscopy and FT-IR spectroscopy. The Intermolecular interactions were studied using Hirshfeld surfaces. The optical properties were analysed using UV–visible and photoluminescence spectroscopy. The third-order nonlinearity of the grown crystal was estimated using the NLO coefficients via the widely recognised femtosecond Z-scan technique, equipped with Ti:sapphire-based laser oscillator using laser pulses of 90 fs and a wavelength of 500 nm at various incident powers. It was observed that with increasing laser power, the nonlinear absorption coefficient of the sample also increased. These findings, combined with the calculation of the nonlinear refractive index, conclusively establish the potential of (Z)-2-(3-chloro-3-(4-chlorophenyl)allylidene)malononitrile for optoelectronic applications.