N-Alkyl-p-nitroanilines: impact of alkyl chain length on crystal structures and optical SHG

N-Alkyl-p-nitroanilines from the propyl to the octyl derivative are synthes ised and characterised. Powder SHG studies show that the butyl derivative a lone is active, in agreement with earlier observations. Crystal structures of the propyl, butyl and pentyl derivatives are determined; the propyl and pentyl derivatives belong to the centrosymmetric space groups <P(1)over bar > and P2(1)/c respectively and the butyl derivative to the noncentrosymmetr ic P2(1)2(1)2(1) space group. Detailed analysis of these structures provide s insight into the critical role of the alkyl chain length in the formation of centrosymmetric or noncentrosymmetric crystal lattices. The utility of alkyl chain length as a crystal design element for quadratic NLO materials is noted.