Theoretical design of alkaline earthides M+(36 adz) Be− (M+ = V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) with excellent nonlinear optical response and ultraviolet transparency

A novel series of alkaline earthides containing eight complexes based upon 3⁶adz complexant are designed by placing carefully transition metals (V–Zn) on inner side and alkaline earth metal outer side of the complexant i.e., M⁺(3⁶adz) Be⁻ (M⁺ = V, Cr, Mn, Fe, Co, Ni, Cu and Zn). All the designed compounds are electronically and thermodynamically stable as evaluated by their interaction energy and vertical ionization potential respectively. Moreover, the true nature of alkaline earthides is verified through NBOs and FMO study, showing negative charge and excess electrons on alkaline earth metal respectively. Furthermore, true alkaline earthides characteristics are evaluated graphically by spectra of partial density state (PDOS). The energy gap (HOMO -LUMO gap) is very small (ranging 2.95 eV–1.89 eV), when it is compared with pure cage 3⁶adz HOMO-LUMO gap i.e., 8.50 eV. All the complexes show a very small value of transition energy ranging from 1.68eV to 0.89eV. Also, these possess higher hyper polarizability values up to 2.8 x 10⁵au (for Co⁺(3⁶adz) Be⁻). Furthermore, an increase in hyper polarizability was observed by applying external electric field on complexes. The remarkable increase of 100fold in hyper polarizability of Zn⁺(3⁶adz) Be⁻ complex is determined after application of external electric field i.e., from 1.7 x 10⁴ au to 1.7 x 10⁶ au when complex is subjected to external electric field of 0.001 au strength. So, when external electric field is applied on complexes it enhances the charge transfer, polarizability and hyper polarizability of complexes and proves to be effective for designing of true alkaline earthides with remarkable NLO response.