On the structural, photophysical and antimicrobial properties of bimetallic Re-Fe coordination compounds bearing diimines ligands

A new complex fac-[(ferroceneCO2)ReI(CO)3(dppz)] (dppz = dipyrido[3,2-a:2',3'-c]phenazine) was obtained and fully characterized by elemental analysis, 1H and 13C NMR, ESI-mass, IR and UV-vis spectroscopy. We also report new insights into the structural and photophysical properties of the fac-[(ferroceneCO2)ReI(CO)3L], where L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen), parent complexes. For all complexes, our results showed that: (i) no singlet oxygen generation was detected in acetonitrile solutions and (ii) they exhibited a very low luminescence quantum yield. However, photoacoustic measurements showed that under photoexcitation the complexes released all the absorbed energy to the medium as prompt heat. The antimicrobial activity of the ferroceneCO2-Re(CO)3(phen) complex was detected against both bacteria from American Type Culture Collections (ATCC) and clinically isolated bacterial strains. Antibacterial activity was rationalized in relation to extension of the π-system of the diamine ligands. Additionally, the ferroceneCO2-Re(CO)3(phen) complex showed no mutagenic potential.