Synthesis, Structural Characterization, and Antibacterial Activity of a Novel Quaternized Norbornene Carboxamide against Sulfate-Reducing Bacteria

<title>Abstract</title> <p> Microbiologically influenced corrosion associated with sulfate-reducing bacteria (SRB) is a significant concern in oil and gas production and transportation systems due to its contribution to accelerated metal deterioration and hydrogen sulfide generation. This study aimed to synthesize and characterize a novel benzyl bromide complex based on the amide of norborn-5-ene-2-carboxylic acid and diethylenetriamine and to evaluate its antibacterial activity against SRB. The target amide was synthesized by condensation of norborn-5-ene-2-carboxylic acid with diethylenetriamine, followed by quaternization with benzyl bromide. The molecular structure of the synthesized complex was confirmed by Fourier-transform infrared, ^1H and ^13C nuclear magnetic resonance spectroscopy. Density, refractive index, specific electrical resistance, and electrical conductivity were determined to assess its physicochemical characteristics. Antibacterial activity was evaluated against <italic>Desulfovibrio desulfuricans</italic> in Postgate B medium at inhibitor concentrations of 25, 50, and 75 mg/L. Bactericidal efficiency was determined based on the suppression of hydrogen sulfide production using iodometric titration. The synthesized complex demonstrated pronounced concentration-dependent antibacterial activity. Bactericidal efficiencies of 82.0%, 94.0%, and 99.5% were achieved at 25, 50, and 75 mg/L, respectively. The marked decrease in hydrogen sulfide generation compared with the untreated control confirmed effective suppression of SRB metabolic activity. These findings indicate that the synthesized benzyl bromide complex combines favorable physicochemical characteristics with high antibacterial efficiency and may serve as a promising multifunctional agent for controlling SRB-associated microbiologically influenced corrosion. Further studies should focus on its corrosion inhibition performance, long-term stability, and applicability under field-relevant oil and gas production conditions. </p>