Exploring preliminary structural relationships and mitochondrial targeting of fac-[MI(CO)3]-bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re)

Abstract

Two bidentate PNP ligands N,N-bis(di-p-tolylphosphino)cyclohexylamine (Cy-pTolPNP) (1) and N,N-bis(di-p-tolylphosphino)cyclobutylamine (Cb-pTolPNP) (2) were synthesized and crystallized. Coordination to the fac-[M^I(CO)₃]⁺ core (M = Re, ⁹⁹Tc) yielded fac-[Re(Cy-pTolPNP)(CO)₃Br] (1A), fac-[⁹⁹Tc(Cy-pTolPNP)(CO)₃Cl] (1B), fac-[Re(Cb-pTolPNP)(CO)₃Br] (2A) and fac-[⁹⁹Tc(Cb-pTolPNP)(CO)₃Cl] (2B) in relatively good yields (56 to 86%): The structures of 1, 2, 1A and 1B were studied by single crystal X-ray crystallography. Preliminary mitochondrial/antimicrobial evaluation of the free ligand (N,N-bis(di-p-tolylphosphino)-cyclohexylamine) (1) and its respective fac-[Re(CO)₃]⁺ (1A) complex indicates that neither the free ligand nor the complex was active against selected fungi Eremothecium ashbyii and Nadsonia fulvescens. In addition, all four compounds were found to have no activity against Gram-positive and Gram-negative bacterial species. These biological results are essential to the understanding of how these types of complexes behave and show they are perfectly stable in the evaluated bio-environments. The results also indicate that these ligands and complexes may present themselves as excellent models for radiotoxicity studies using technetium-99m, but more specifically, rhenium Re-186 and Re-188.