Nonlinear optical properties of pyrene-based chalcones: Insights from experimental and computational studies

Pyrene-based chalcones (PyChs) have emerged as promising potential for nonlinear optical (NLO) applications, due to their extended π-conjugation, efficient intramolecular charge transfer (ICT), and tenable electronic properties. These materials exhibit significant third-order NLO responses which making them suitable for optoelectronic applications. The lack of an integrated understanding of how molecular structure and electronic properties affect the NLO response of PyChs limits their rational optimization. Although many compounds show promising third-order NLO properties, the absence of clear structure–property relationships and strong links between experimental and computational results hinders predictive design and practical development. This review aims to critically analyse the synthesis strategies, structural characterization, and NLO properties of PyChs. Particular emphasis is placed on the factors affecting the optical properties of these compounds. Additionally, to correlate molecular structural features with experimentally measured third-order NLO responses and computationally derived electronic parameters to establish clear structure–property relationships and provide guidance for the rational design of high-performance PyCh-based NLO materials. The synthesis of PyChs is discussed with emphasis on the Claisen-Schmidt condensation mechanism followed by structural analysis using single-crystal X-ray diffraction (SCXRD) and Fourier-transform infrared spectroscopy (FTIR). Their optical and electronic behaviours are further explored through computational approaches, including frontier molecular orbital (FMO) analysis, natural bond orbital (NBO) theory, excited-state electronic transitions, and the evaluation of polarizability and hyperpolarizability via density functional theory (DFT). Emphasis is placed on structure-property relationships governing NLO activity, particularly the roles of molecular planarity and donor–acceptor interactions. Additionally, third-order NLO responses are analysed using the Z-scan technique and correlated with computational insights. Overall, this review highlights PyChs as promising materials for potential applications in photonic technologies and opens up future research in high-performance NLO applications.