Two new N-salicylidene-N'-aroylhydrazines ligands have been prepared: N-4-diethylaminosalicylidene-N'-4-nitrobenzoyl-hydrazine (L-1) and N-4-diethylaminosalicylidene-N'-4-(4-nitrophenylethylidene)-benzoyl-hydrazine (L-2). The ligands are properly functionalized with strong electron donor-acceptor groups and are of potential interest in second-order nonlinear optics (NLO), Dimeric copper(II) and palladium(II) complexes with L-1 and L-2 have been prepared, and, starting from these, mononuclear acentric adducts with pyridine as a further ligand have been prepared and characterized. The X-ray structures of three adducts are also reported. The NLO activity of the adducts has been determined by EFISH measurements giving mubeta values up to 1500 x 10(-48) esu for an incident wavelength of 1.907 mum.