First hyperpolarizability of H–(BN)N–H oligomers: analysis of geometry, asymmetry and delocalization effects

Abstract

We analyze the behavior with chain length of the longitudinal electronic first hyperpolarizability of linear H–(BN)_N–H chains. The evolution of the first hyperpolarizability, which strongly depends on geometrical and electron correlation effects, is explained in terms of delocalization and asymmetry. The influence of the bond length alternation on the first hyperpolarizability is also highlighted. Although small, the first hyperpolarizability of H–(BN)_N–H chains presents an evolution that proves that AB systems may behave like push–pull oligomers.