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Purpose: To investigate the antimicrobial, antibiofilm, and cytotoxicity properties of methallyl substituted benzimidazolium-based, silver-bound N-heterocyclic carbene (Ag(I)-NHC) complexes, with respect to their potential to act as antimicrobial agents. Methods: The antimicrobial, antibiofilm, and cytotoxicity properties of the four complexes, the synthesis and characterization of which were carried out previously, were investigated. The antimicrobial properties were tested using the broth microdilution method, while their antibiofilm potential were determined by microtiter plate assay. The L-929 cell line was used for cytotoxic studies. Results: Strong antibiofilm and antimicrobial effects were produced by Ag(I)-NHC complexes. Compounds 2 and 3 showed potent activities against E. coli strain, with effects similar to that of positive control antibiotic, while compounds 1 and 4 exhibited antimicrobial activity at a concentration of 31.2 µg/mL. The compounds were effective against biofilms formed at concentrations in the range of 32 -- 84 %, and degraded mature biofilms at a concentration range of 14 - 66 %. Compounds 1 and 2 did not significantly affect cell survival (p > 0.05), while compounds 3 and 4 significantly reduced cell survival, when compared with untreated cells in the control group (p < 0.001). Conclusion: This study may be one of the few studies on benzimidazolium-derived NHCs. The compounds which produced antimicrobial, antibiofilm, and cytotoxic properties in this study may be valuable and novel antimicrobial agents. Therefore, there is need for further in vivo and in vitro studies on these compounds. [ABSTRACT FROM AUTHOR]

Microorganisms in the biofilm structure cause severe health problems and economic losses. Therefore, it is very important to design and screen anti-biofilm molecules that can solve the related problems. This paper is aimed to demonstrate the antimicrobial and anti-biofilm properties of allyl substituted benzimidazolium-based Ag(I)-containing N-heterocyclic carbene (NHC) complexes. In this work, the antimicrobial and anti-biofilm properties of six allyl-substituted benzimidazolium-based Ag(I)-NHC complexes, the synthesis and characterization of which had been carried out previously, were investigated. The antibacterial properties of Ag(I)-NHC complexes were tested by the broth microdilution method. The biofilm formation was detected by microtiter plate assay. All test compounds (1–6) showed strong and same activity against Escherichia coli ATCC 25922 at concentrations of ≤3.9 μg/mL as compared to that of the reference anti-biotics (ampicillin). Test compounds exhibited the same or stronger activity than the reference drug against the Acinetobacter baumannii isolate with MedIC values of 15.6 – 31.25 μg/mL in comparison to the positive control colistin. All compounds inhibited the formation of E. coli biofilms at sub-MIC concentrations by 56 – 90%. Furthermore, it was found that these compounds reduced Klebsiella pneumoniae biofilm formation by 29 – 65%, S. aureus biofilm formation by 36 – 52%, E. faecalis biofilm formation by 38 – 50%, A. baumannii biofilm formation by 51 – 60%, and Candida albicans biofilm formation by 38 – 53%. Regarding the biofilms formed, it was established that the test compounds eradicated the mature of E. coli biofilm by 43 – 63%, K. pneumoniae biofilm by 16 – 40%, S. aureus biofilm by 18 – 39%, E. faecalis biofilm by 15 – 27%, A. baumannii biofilm by 27 – 53%, and C. albicans biofilm by 18 – 41%. Compounds evaluated in our work, which is one of the few studies on benzimidazolium-derived NHCs, have the potential to become new biological agents with strong antimicrobial properties and activity against microbial biofilms. Therefore, further in vivo and in vitro studies should be conducted. [ABSTRACT FROM AUTHOR]

In this work, a novel compound, 1-(2,5-dimethylbenzyl)benzimidazole (1) was prepared by N-alkylation of benzimidazole with 2,5-dimethylbenzyl chloride in the presence of KOH base. Quaternization of 1 with 2,5-dimethylbenzyl chloride gave 1,3-bis(2,5- dimethylbenzyl)benzimidazolium chloride (2) salt. The reaction of 2 with palladium(II) acetate, PPh3, LiCl and Et3N gave [PdCl2{1,3-bis(2,5-dimethylbenzyl)benzimidazolin-2-ylidene}(PPh3)] (3) complex. The prepared compounds were characterized by spectroscopic methods and elemental analysis. The palladium complex 3 was used as catalyst in Suzuki-Miyaura cross-coupling reactions of some aryl bromides and chlorides with phenylboronic acid. In the reactions of the all aryl bromides, the catalyst displayed excellent activity and biphenyl compounds were achieved in >99% yields. High activity was observed with some aryl chlorides. [ABSTRACT FROM AUTHOR]

A series of ester-functionalized benzimidazolium salts 2a–c were prepared by quaternization of 1-{(ethoxycarbonyl)methyl}benzimidazole (1) with 3,5-dimethylbenzyl bromide, 2,5-dimethylbenzyl chloride and 3-methoxybenzyl chloride, respectively. Refluxing 2a–c with nickelocene in THF yielded the neutral cyclopentadienyl NHC nickel(II) complexes 3a–c. Their structures were defined by NMR, IR and elemental analysis techniques. Molecular weights of 3a–c were affirmed by MALDI-TOF mass spectrometry. Catalytic tests of 3a–c were performed in Kumada coupling of some aryl chlorides with phenylmagnesium bromide at 25 °C. [ABSTRACT FROM AUTHOR]

A series of novel N-heterocyclic carbene rhodium complexes (NHC-Rh), containing benzimidazole framework, were prepared smoothly by a five-step route. Their structures were elucidated based on spectral techniques, including NMR and MS spectrometry. Along with several NHC-Rh complexes we prepared before, the compounds prepared herein were evaluated for their cytotoxicities against MCF human breast cancer cells and several of them showed strong activities with IC50 values ranging from 0.38 to 1.18µM, which were better than the positive control paclitaxel. [ABSTRACT FROM AUTHOR]

Abstract A new N-heterocyclic carbene (NHC) salt was synthesized by the reaction of 1-allyl benzimidazole with 2-methyl benzyl chloride. The structure of N-heterocyclic carbene salt was determined by elemental analysis, FT-IR, 1 H NMR and 13 C NMR spectroscopy and supported by the computational spectral analyses. For this purpose, the stable conformational structures obtained by Potential Energy Surface (PES) scan at B3LYP/6-31G (d,p) level of the theory have been used to elucidate the spectroscopic studies of the NHC salt as well as to search the electronic properties being important to predict the chemical reactivity behavior and nonlinearity properties of the NHC salt. FMO amplitudes and MEP diagrams have been used to show the chemically active sites of each stable conformer. Graphical abstract Image 1 Highlights • Synthesis and characterization of the NHC salt. • The structure was investigated by NM and FT-IR spectroscopy. • Stable conformers of NHC salt were revealed by computational modeling. • Spectral data were compared with computational ones. • NBO, NLO, FMO and MEP diagrams were investigated by computational tools. [ABSTRACT FROM AUTHOR]

A series of C2-symmetric chiral benzimidazolium salts, the precursor of N-heterocyclic carbene ligands, were designed and synthesized from 1,2-dibromobenzene. In situ prepared corresponding carbenes were tested in the asymmetric palladium-catalyzed intramolecular -arylation of amides, affording chiral diarylmethanols with high yields and moderate enantioselectivities. [ABSTRACT FROM AUTHOR]

• Novel silyl-tethered benzimidazolium salts were synthesized via stepwise N-alkylation of benzimidazole. • These salts were characterized by elemental analysis, IR, 1H, 13C NMR spectroscopy. • Their antibacterial and antifungal activities were investigated. • These salts showed good antimicrobial activity. A series of new silyl-substituted benzimidazolium salts were synthesized in good yield by the reaction of 1-(dimethylvinylsilyl)methylbenzimidazole and various alkyl halides. These salts were characterized by spectroscopic techniques. Also, crystal structure of 2c has been determined by the single-crystal X-ray diffraction method. Newly synthesized compounds were tested for antibacterial and antifungal activities and the minimum inhibitory concentrations were determined. The results indicates that some of compounds exert effective antibacterial activity against four Gram (-) bacterial and four Gram (+) bacterial strains and two yeast strains. [Display omitted] [ABSTRACT FROM AUTHOR]

A highly effective, easy to handle and environmentally benign process for a palladium mediated Heck reaction was developed. The in situ prepared 3-component system, Pd(OAc)2/1,3-dialkylbenzimidazolium chlorides (LHX = 1a-g) and Cs2CO3, catalyzes quantitatively the Heck coupling of aryl bromides under mild conditions in aqueous media. [ABSTRACT FROM AUTHOR]