Mechanoluminescence and nonlinear optical properties of a self-assembled piperazine-based supramolecular system: structural insights and computational analysis

Abstract

The present work reports on the mechanoluminescence (ML) and third-order nonlinear optical (NLO) properties of a self-assembled supramolecular compound, 1-(4-methoxyphenyl)-4-(4-nitrophenyl)piperazine (MPNPP). The solid-state structure of MPNPP was confirmed using single-crystal X-ray diffraction, which revealed that the piperazine ring adopts a chair conformation, with a strong activating group (4-methoxyphenyl) and a strong deactivating group (4-nitrophenyl) positioned at the 1,4-positions in the equatorial plane, with no conventional hydrogen bonding. π⋯π and C–H⋯π interactions lead to the formation of a self-assembled supramolecular arrangement with loose packing and low lattice energy in the molecular crystal system. These non-covalent interactions make the crystal susceptible to external mechanical stimuli, such as grinding, and are crucial for exhibiting the mechanoluminescence properties of the compound. Hirshfeld surface and fingerprint analyses were used to visually and quantitatively examine interactions in the solid state. The analysis of the nonlinear optical properties of the MPNPP compound in a simulated crystalline environment revealed significant results for the linear refractive index and third-order nonlinear susceptibility, evaluated as functions of electric field frequency using the supermolecule approach at the DFT/CAM-B3LYP/6-311+G(d) level. Compared to data obtained from other organic crystals, the compound exhibited considerable potential as a nonlinear optical material. The study also evaluated the anticancer potential of the MPNPP compound against lung (2YJR) and breast (1USN) cancer proteins, with results compared to those from standard anticancer drugs such as Lorlatinib and Doxorubicin.