Counterion-induced modulation in biochemical properties of nitrile functionalized silver(I)-N-heterocyclic carbene complexes

The new Ag(I) complexes (2-4) with proligand 1 were prepared and characterized as prospective antibacterial drug candidates. These compounds consist of a Ag(I) center linearly coordinated to two identical N-heterocyclic carbenes (NHCs). Crystal structures were solved for complexes 3 and 4, the resulting structural data being in good agreement with expectations. We wondered whether the presence of different counter ions in these compounds might lead to modulation of their biological properties. Notably, in spite of their similar structural pattern, Ag(I)-NHC complex 2 with Br- manifested better antibacterial actions than complexes 3 and 4 with PF6- and BF4-, respectively. Stability study over time in bacterial solutions revealed that these complexes have better stability than AgNO3. Their interaction with DNA and RNA was explored, cleavage activity indicates that all Ag(I)-NHC complexes exhibited interesting nuclease activity via non-oxidative pathway.