Expanding the Variety of Pyridinium-Based bis-QACs with Antimicrobial Properties: Investigation into Linker Structure-Activity Correlation.

For decades quaternary ammonium compounds (QACs) have served as main component of a top antiseptic and disinfectant compositions. Among them, bis-QACs are the most prominent and effective class of biocides. Although mono-QACs still dominate the antiseptic market, their activity against Gram-negative bacteria is largely inferior to bis-QACs. Moreover, the new wave of bacterial resistance during the COVID-19 pandemic is threatening the efficiency of popular antiseptics. Therefore, the requirement for novel biocides is urgent. Reported here is a unified and simple two-step synthesis to achieve novel biocide's architectures with aromatic linkers. Thus, a series of 14 bis-QACs have been prepared using an Ullman-type reaction following by N-alkylation. The most prominent compounds showed strong bioactivity against a panel of nineteen microbial pathogens, multi-resistant bacterial ESKAPEE strains, fungi and biofilms, including strains, which acquired resistance during COVID-19 in 2021. Moreover, significant improvements in antibiofilm action were observed, where bis-QACs 5c and 6a outperformed gold standard pyridinium antiseptic octenidine. These findings will serve as a good basis for further studies of bis-QACs architectures as highly effective biocides.