Theoretical study of 36Adz based alkaline earthides M+(36Adz)M− (M+ = Li & Na; M− = Be, Mg & Ca) with remarkable nonlinear optical response

Abstract

The 36Adz complexant has been used to design and investigate another group of alkaline earthides, M+(36Adz)M−. Here, M+ represents the alkali metals i.e., Li & Na while M− represents alkaline earth metals i.e., Be, Mg & Ca. Basic pattern of arrangement of atoms in alkaline earthides includes the insertion of the alkali metal at the middle of hollow 36Adz cage and the space outside the cage is occupied by the alkaline earth metal. Natural bond orbitals are scrutinized, and calculation results show the alkaline earth metals as anions (negative charges on them). Highest occupied molecular orbitals are also analysed and the results of this analysis show that highest occupied molecular orbitals are present on alkaline earth metals. Both these characteristics confirm that the designed compounds are alkaline earthides. The same characteristic i.e., locale of excess electron, is further corroborated by the partial density of states spectra of the compounds. Moreover, extraordinarily higher first hyperpolarizabilities are shown by these compounds, the highest βo being shown (equal to 5.1 × 108 au) by Li+(36Adz)Mg−. These inordinately higher values of hyperpolarizability are ascribed to the distinctive feature of these compounds i.e., alkaline earth metals incorporate excess electron/bear negative charge. Furthermore, these complexes show very low transition energies (ΔE) and vertical ionization energy (VIE) values, ranging from 0.30 to 2.57 eV and 2.24 eV–2.51 eV, respectively. Such lower ΔE and VIE justify their larger values of hyperpolarizabilities. These results reveal that the alkaline earthides are a useful entry for high-performance NLO materials.