Crystallographic studies of salts of quaternary phosphonium cations, tetraphenylphosphonium and benzyltriphenylphosphonium, reveal differences in size and shape of the phosphonium cations dominate the intermolecular packing with the cations self-associated through phenyl embraces.

New hydrazone Schiff base ligands were synthesized from the condensation of cinnamaldehyde and three different hydrazides (benzhydrazide, isoniazid, and 4-phenylsemicarbazide), and these compounds were further reacted with copper(II) ion affording three different Schiff base metal complexes. All hydrazone Schiff base ligands and their respective metal complexes were chemically characterised using NMR, FTIR, CHN analyses, and UV-visible spectrophotometry and these chemical analyses showed successful coordination of hydrazone Schiff base ligands to copper(II) ion. All synthesized Schiff base ligands and metal complexes were screened against Staphylococcus aureus, Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa. Interestingly, all Schiff base metal complexes showed a higher antibacterial activity than their parent hydrazone Schiff base ligands; as shown by an increase of up to 60% of inhibition observed for one of the metal complexes.