Electronic structures and second hyperpolarizabilities of alkaline earth metal complexes end-capped with NA2 (A = H, Li, Na)

Abstract

The ground state structures and NLO properties of a number of alkaline earth metal complexes end-capped with NA₂ groups (A = H, Li, Na) are calculated by employing the CAM-B3LYP, wB97XD and B2PLYP functionals along with MP2 and CCSD(T) for 6-311++G(d,p), 6-311++G(3df,3pd), aug-cc-pVTZ, aug-pc-2 and Hypol basis sets. The complexes are found to be significantly stable. The magnitude of second hyperpolarizability enhances appreciably with increase in the number of magnesium and calcium atoms in the chain, which has been indicated by the power law dependence γ = a + bn^c with c values ranging from 2.4–4.3 for Mg and 2.4–3.7 for Ca complexes, respectively. The largest second-hyperpolarizability (10⁹ au) is obtained for the complex Ca₇(NNa₂)₂ at the CAM-B3LYP level. The two state model has been used to explain the variation of hyperpolarizabilities.