Novel inorganic aromatic mixed-valent superalkali electride CaNCa: an alkaline-earth-based high-sensitivity multi-state nonlinear optical molecular switch

Focusing on innovative high-performance single-pole double-throw nonlinear optical (NLO) molecular switches, two C 3v configurations ( 1 and 3 ) and one D 3h configuration ( 2 ) of bipyramidal CaN 3 Ca have been obtained by using quantum mechanical methods. Not only are 1 , 2 , and 3 alkaline-earth-based aromatic superalkalis, but they are also interesting electrides. The salt-like electronic structures of e − Ca 2+ N 3 3− Ca 2+ ( 1 ) and Ca 2+ N 3 3− Ca 2+ e − ( 3 ) with localized redox centres are rare inorganic Robin-Day class II-type structures, and e 0.5− Ca 2+ N 3 3− Ca 2+ e 0.5− ( 2 ) with a delocalized structure is a class III-type mixed-valent superalkali electride. Under a small external electric field of ±0.0110 a.u. (0.565 V Å −1 ), the short-distance hopping of Ca atoms in CaN 3 Ca from the D 3h configuration with in-plane aromaticity to each C 3v configuration with out-of-plane aromaticity brings about the long-range transfer of half an electron from one Ca atom to another. And, subsequently, a large dipole moment ( μ 0 ) and remarkable static first hyperpolarizability ( β 0 ) occur. μ z and β zzz range from 0 ( D 3h , off form) to −12.1 or 12.1 D ( C 3v , on forms) and from 0 ( D 3h , off form) to −19 428 or 19 428 a.u. ( C 3v , on forms), respectively. These extremely large differences in μ z and β zzz values between the D 3h and each of the C 3v configurations confirm the potential of these inorganic aromatic Robin-Day-type superalkali electrides for applications in high-sensitivity multi-state nonlinear optical switches. Focusing on innovative high-performance single-pole double-throw nonlinear optical (NLO) molecular switches, two C 3v configurations ( 1 and 3 ) and one D 3h configuration ( 2 ) of bipyramidal CaN 3 Ca have been obtained by using quantum mechanical methods.