New bipyridyl ligands bearing azo- and imino-linked chromophores. Synthesis and nonlinear optical studies of related dipolar zinc complexes†

The synthesis and optical properties of 4,4′-bis(dialkylaminophenylazo)-2,2′-bipyridine and 4,4′-bis(dialkylaminophenylimino)-2,2′-bipyridine ligands are described; the corresponding dipolar bipyridyl zinc dichloride complexes have been prepared and their second order nonlinear optical properties determined by electric field-induced second harmonic generation (EFISH) at 1.34 µm.