Superalkali-alkaline earthide ion pairs of δ + (AM-HMHC)-AM' δ - (AM = Li, Na and K; AM' = Be, Mg and Ca) possessing large NLO responses and excellent electronic stabilities and alkalide characteristics: a DFT study.

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ + (AM-HMHC)-AM' δ - is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M + (calix[4]pyrrole)M' - (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ + (AM-HMHC)-AM' δ - are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response ( β HRS ). These alkaline earthides suggest prominently high β HRS up to 2.59 × 10 4 a.u. (boat forms of δ + (Na-HMHC)-Ca δ - ). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.