Structural Designs and Property Characterizations for Second-Harmonic Generation Materials

Second-harmonic generation (SHG) materials only exist in solids that have no inversion center space groups, and they are constructed by the building blocks or chromophores of noncentrosymmetricity (NCS). In this chapter, we employed one or multiple chromophores that result from the coordination structure distortions of a d⁰ cation, polar displacement of d¹⁰ cation center, a stereochemically active lone pair (SCALP) of cations, and asymmetrical delocalization π-charge systems, as building blocks to obtain some new compounds with NCS space group. The single-crystal structures were characterized, and physical properties, in particular SHG responses, were measured for these compounds. The electronic structures and density of states were calculated by DFT method, and the SHG properties are simulated to gain an insight into the relations between structure and NLO properties for the materials. The electronic origination of large SHG responses was assigned in terms of the calculated results.