Designing High-Performance Nonlinear Optical Materials via Interaction of Hexahelicene with Coinage Metal Clusters

We investigated NLO properties of hexahelicene–coinage metal (Cu, Ag, Au; n=۱–۳) adducts using DFT/B۳LYP with ۶-۳۱۱++G(۲d,۲p) (C,H) and LANL۲DZ (metals). The geometric and electronic structures of the resulting HH···Mₙ adducts were analyzed through vibrational frequency calculations, Molecular Electrostatic Potential (MEP), and Natural Bond Orbital (NBO) analysis. Furthermore, the optical absorption spectra and first-order hyperpolarizability (β₀) values were computed using Time-Dependent DFT (TD-DFT) to evaluate the NLO response of the designed systems. The results indicate a significant reduction in the HOMO–LUMO energy gap (Eg) upon complexation compared to the pristine hexahelicene molecule. On average, the Eg of pure Hexahelicene is ۳.۹۴ eV, while it decreases to values ranging from ۱.۲ to ۳.۶۵ eV in the Mn(H) adducts. Moreover, all studied adducts exhibit enhanced average polarizability (α) and remarkably improved first hyperpolarizability (β₀), highlighting their potential as efficient NLO materials. For instance, the β₀ value increases from ۲۲۹ a.u. in pure Hexahelicene to up to ۳۲۳۶۵ a.u. in the Cu₃H₃ adduct. Among the coinage metals, gold-based adducts generally show superior performance, although copper and silver derivatives also demonstrate considerable NLO activity. These findings suggest that hexahelicene–metal cluster adducts could serve as promising candidates for designing novel nonlinear optical materials with tunable electronic and optical properties.

کلیدواژه ها:

Average polarizability (&alpha ، ) ، Coinage metals ، first Hyperpolarizability (&beta ، ۰) ، gold and copper ، NonLinear Optical (NLO) properties