Unveiling the NLO Potential of Transition Metalides: Stability, Electronic Structure, and Frequency‐Dependent NLO Properties

A detailed investigation on the geometric, electronic, and nonlinear optical properties of new transition metalides has been carried out. The negative interaction energies ( E int ) of the designed complexes ranging from −41.59 to −119.25 kcal/mol show their thermodynamic stability. The transition metalide nature of the designed complexes is revealed through natural bonding orbitals (NBO) and frontier molecular orbital (FMO) analyses where negative charge and density of highest occupied molecular orbital (HOMO) over transition metals confirm their transition metalide nature. The loosely bound excess electrons reduce their HOMO‐LUMO gaps (H–L gaps). All these features are responsible for remarkable nonlinear optical (NLO) response which is evinced through considerably higher values of hyperpolarizability ( β o ) (up to 2.15x10 5 au). The controlling factors of β o , i.e., change in dipole moment (∆μ), oscillator strength ( f o) , and transition energy ( ∆E) have also been examined through two level model. Additionally, the results computed for electro‐optical Pockels effect, second harmonic generation, and hyper Rayleigh scattering (between 1300 and 1900 nm wavelengths) show improved hyperpolarizability values at larger wavelength. Moreover, remarkably high frequency dependent second order hyperpolarziability for the coefficients, i.e., dc‐Kerr effect and electric field induced second harmonic generation (SHG) has been computed along with quite high nonlinear refractive index for the designed complexes. Overall, these findings provide theoretical guidance for design and synthesis of NLO materials based on transition metalides with high NLO responses.