FT-Raman, FT-IR, NMR structural characterization and antimicrobial activities of 1,6-bis(benzimidazol-2-yl)-3,4-dithiahexane ligand and its Hg(II) halide complexes

Abstract

1,6-Bis(benzimidaz-2-yl)-3,4-dithiahexane ligand (L) and its mercury halide complexes were prepared and characterised. The elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid, far), 1 H, 13 C NMR and geometry optimization in MOPAC using MNDOd parameter on CACHE, prove the existence of neutral, mononuclear and the distorted tetrahedral [Hg(L)X 2 ] complexes. In all the three complexes, the ligand acts as a chelating bidentate, through two of the bridging sulphur atoms and together with the monodentate coordination of the two anionic halide ligands to the metal centre forming a possible 4-coordinate compounds. The antimicrobial activities of free ligand, its hydrochlorinated salt, mercury halides and the complexes are evaluated using disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against 10 bacteria. The obtained results from disk diffusion method are assessed in side-by-side comparison with those of Penicillin-g, Ampicillin, Cefotaxime, Vancomycin, Oflaxacin and Tetracyclin well-known antibacterial agents. The results from dilution procedure are compared with Gentamycin as antibacterial and Nystatin as antifungal. The antifungal activities are reported on five yeast cultures namely Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii and Hanseniaspora guilliermondii, and the results are referenced with Nystatin, Ketaconazole and Clotrimazole, commercial antifungal agents. In most cases, the compounds show broad-spectrum (Gram + & Gram -bacteria) activities that are comparatively, slightly less active or equipotent to the antibiotic and antifungal agents in the comparison tests.

How Stabilizers and Reducing Agents Affect the Formation of Nanogold Amalgams

“…As shown in Figure S8 of the Supporting Information, the Raman peak registered at 320 cm –1 is assigned to the symmetric ν­(Au–S) stretch . After Hg 2+ addition, the Raman bands corresponding to the symmetric stretching of Hg–S appear at 255 and 291 cm –1 . , Thus, it is plausible that reduced Hg could interact simultaneously with the AuNRs and the sulfur atom through the Au–Hg–S bond. , In addition, the introduction of AA solution initially caused a slight redshift (from 630 to 635 nm) in the LSPR peak for 1-hexadecanethiol-coated AuNRs under low Hg 2+ conditions, presumably because excess AA exchanged a portion of CTAB that was not completely replaced during mercaptan modification . The TEM images in Figure S7 of the Supporting Information show the 1-hexadecanethiol-coated AuNRs in the absence of Hg 2+ as well as at medium and high concentrations.…”

“…26 After Hg 2+ addition, the Raman bands corresponding to the symmetric stretching of Hg−S appear at 255 and 291 cm −1 . 27,28 Thus, it is plausible that reduced Hg could interact simultaneously with the AuNRs and the sulfur atom through the Au−Hg−S bond. 25,29 In addition, the introduction of AA solution initially caused a slight redshift (from 630 to 635 nm) in the LSPR peak for 1-hexadecanethiol-coated AuNRs under low Hg 2+ conditions, presumably because excess AA exchanged a portion of CTAB that was not completely replaced during mercaptan modification.…”

A Three-Coordinate Ag(I) Complex Based on the V-Shaped Ligand 1,3-Bis(1-Ethylbenzimidazol-2-Yl)-2-Thiapropane: Synthesis, Crystal Structure and DNA-Binding Properties

“…The IR spectrum of the ligand 1 shows characteristic absorption bands of the benzimidazole group at 1274 and 1458 cm -1 , which can be assigned to ν (C-N) and ν (C=N) , respectively. 49,50 For the complex 2, these stretching frequencies are red shifted to 1180 cm -1 and 1430 cm -1 , respectively, which implies direct coordination of nitrogen atoms to metal ions.…”

Structural Elucidation of Sulfur Derivatives of Benzimidazoles by Density Functional Calculations, and Vibrational and NMR Spectral Analyses

“…Design and synthesis of BI derivatives have been greatly advanced over the last few decades due to their resemblance with the naturally occurring nucleotide bases, their structural and functional features, and their rich chemical behaviors. They play significant roles in organic and coordination chemistries as a result of their several potential donor centers [1][2][3], in medicinal chemistry as antibacterial, antifungal [4][5][6], antitumor [7][8][9][10], and anthelmintic (antiparasitic for humans, pets, livestock, and plants) [11] agents, in materials' applications as dyes, photographs, and catalytic agents [12][13][14]. Hence, structural investigations on BI derivatives are of great importance to understand their structure-function relationships better.…”