Phosphorylated Derivatives of Quaternary Ammonium Salts: Synthesis, X-Ray Crystal Structure, Antimicrobial Activity and Ecotoxicity.

Phosphorylated structural analogs of Benzalkonium Chloride-diisopropoxyphosphorylmethane (dimethyldodecylammonium) bromide 1 (phosphorylated quaternary ammonium salt) and isopropoxyphosphorylmethane (dimethylalkylammonium) 2 (phosphorylated betaine) were synthesized. The structure of compound 1 was confirmed by single crystal X-ray diffraction study. The antibacterial, antifungal, and ecotoxicological profiles of the synthesized compounds were evaluated against aquatic organisms and flowering plants. Both compounds demonstrated comparable toxicity toward Paramecium caudatum (Protista) and Ceriodaphnia affinis (Cladocera), with EC values of compound 1-0.62 g/L (P. caudatum), 0.13 g/L (C. affinis) and compound 2-0.90 g/L (P. caudatum), 0.08 g/L (C. affinis). These values indicate significantly lower toxicity compared to Benzalkonium chloride (BC) control (EC = 110 μg/L for P. caudatum, 30 μg/L for C. affinis). Neither compound exhibited toxicity toward the green alga Chlorella vulgaris, whereas BC inhibited growth by 93%. However, both compounds 1 and 2 inhibited Raphanus sativus seed germination at 10.0 g/L, whereas BC exhibited only marginal phytotoxicity even at this high concentration (10 g/L). According to the disk diffusion method, compound 1 exhibited superior activity against all tested isolates Bacillus subtilis (Gram-positive), Pseudomonas fluorescens (Gram-negative) and Fusarium sp. (micromycete). Compound 2 showed activity only against B. subtilis and Fusarium sp. at 10.0 g/L. Compound 1 inhibited microbial growth significantly more effectively than BC across all three microorganisms, while compound 2 performance did not differ substantially from the control. Thus, the synthesized compound 1-demonstrates antimicrobial efficacy comparable to reference compounds (Miramistin, Benzalkonium Chloride) while exhibiting substantially lower ecotoxicity. This enhanced safety profile suggests its production and application would pose reduced environmental risks.