Deciphering ethynyl single crystal for NLO applications: Synergistic studies on the structural, Hirshfeld surface, photophysical and DFT assessment

Abstract

In this contribution, we have integrated multiple approaches in investigating the profiles and behaviour of simple ethynyl derivative, 1-[4-(4-(dimethylaminophenyl)ethynyl)phenyl]ethanone (4DME) tolane which is known to be integrated widely in molecular electronics as conjugated building block in functional molecules. Prepared via simplified aerobic Sonogashira cross-couping reaction, symmetrical chromophore of 4DME crystallizes in monoclinic with complex framework containing the space group of P21/n and includes four molecules within a unit cell. The fingerprint plots and Hirshfeld surface analyses demonstrate the presence of synergism between molecules supporting nonlinear optical response of the compound. It was shown that C⋯H contact (44.5 %) is the major contribution of intermolecular interaction executed by Hirshfeld surface area. The investigation on their spectroscopic, thermal analysis and density functional theory (DFT) analysis operating under B3LYP/6-31G (d,p) were conducted to determine the energies of the LUMO and HOMO level, NLO behaviour, intermolecular charge transport facilitated by global chemical reactivity descriptors, molecular electrostatic potentials (MEP) and hyperpolarizability analyses. From the simulated DFT calculation, it shows that 4DME has good polarizability properties with HOMO-LUMO energy gap of 3.89 eV. Calculated total first hyperpolarizability βtot of 4DME were 1261.40 × 10−30 esu which can be potentially applied as good nonlinear optical materials. The preliminary outcomes prove that this simple ethynyl derivative is capable of being used in optoelectronic industry as NLO-based products. A CW diode laser operating at 532 nm wavelength was used to perform the Z-scan measurements and 4DME showed an effective value of χ(3) in order of 10−6, indicating good nonlinear properties.