A new class of quaternary ammonium compounds as potent and environmental friendly disinfectants

Quaternary ammonium compounds (QACs) are inexpensive and readily available disinfectants, and have been widely used, especially since the COVID-19 outbreak. However, the toxicity of QACs to humans has raised increasing concerns in recent years. Here, a new type of QACs was synthesized by replacing the alkyl chain with zinc phthalocyanine (ZnPc), which consists of a large aromatic ring and is hydrophobic in nature, similar to the alkyl chain of QACs. Three ZnPc-containing disinfectants were synthesized and fully characterized. These compounds showed 15–16 fold higher antimicrobial effect against Gram-negative bacteria than the well-known QACs with half-maximal inhibitory (IC 50 ) values of 1.43 μM, 2.70 μM, and 1.31 μM, respectively. With the assistance of 680 nm light, compounds 4 and 6 had much higher bactericidal toxicities at nanomolar concentrations. Compound 6 had a bactericidal efficacy of close to 6 logs (99.9999% kill rate) at 1 μM to Gram-positive bacteria, including MRSA, under light illumination. Besides, these compounds are safe for mammalian cells. In a mouse model, compound 6 was effective in healing wound infection. Importantly, compound 6 was easily degraded at working concentrations under sunlight illumination, and had good environmental safety. Thus, compound 6 is a novel and promising disinfectant. • Quaternary ammonium compounds (QACs) degrade slowly in environment, causing health concerns. • A new type of QACs containing phthalocyanine group are synthesized. • New QACs degrade fast under environmental lighting. • New QACs show 15–16 times stronger bactericidal effect. • New QACs kill 6 logs of Gram-positive bacteria at 1 μM.