Photophysical and antimicrobial properties of new double-armed benzo-15-crown-5 ligands and complexes

New double-armed crown ether ligands linked to pyridine derivatives have been synthesized and characterized. These macrocyclic ligands (1–5) have been synthesized by the reactions of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 3-hydroxy pyridine derivatives. A series of Na+, K+ and Ag+ complexes (1a–5a, 1b–5b and 1c–5c) of the macrocyclic ligands have been prepared from sodium perchlorate, sodium picrate, potassium iodide, potassium picrate and silver nitrate salts, respectively. The most suitable cation Na+ is bound to the 15-crown-5 cavity and 1:1 “filling complexes” are formed (1a–5a) while the K+ cation interacts with the crown ether cavity and forms sandwich-type complexes (1b–5b). The Ag+ complexes (1c–5c) have been obtained with a pyridine moiety of the new crown ethers. New ligands undergo photophysical changes when bonding the cation. The influence of metal cations such as Na+, Li+, K+, Fe3+, Cu2+, Ca2+, Ba2+ and Al3+ on the spectroscopic properties of the pyridine linked to the double-armed crown ether moiety was investigated in EtOH solution by means of absorption and emission spectrometry. The prepared compounds (1–5, 1a–5a, 1b–5b and 1c–5c) were evaluated for antibacterial and antifungal activities against pathogenic microorganisms. The results show that the antimicrobial activity of the synthesized compounds varying a degree of inhibitory effects on the growth of different tested pathogenic strains.