Synthesis and structure of the mercury chloride complex of 2,2'-(2-bromo-5-tert-butyl-1,3-phenyl-ene)bis-(1-methyl-1H-benzimidazole)

Synthesis, biological evaluation and model membrane studies on metal complexes containing aromatic N,O-chelate ligands

Novel lanthanide (Ln) compounds [Ln(L)₂]Cl^.xH₂O (Ln = La³⁺, Ce³⁺, Sm³⁺) containing aromatic N,O-chelate ligands [HL1 = 4-amino-2-(1H-benzimidazol-2-yl)phenol; HL2 = 5-amino-2-(1H-benzimidazol-2-yl)phenol] have been synthesized and structurally characterized by elemental analysis, NMR and IR spectroscopy, molar conductance measurements, and mass spectrometry (MS). The spectroscopic data suggested that the benzimidazolyl-phenol ligands act as N,O-chelate ligands through the iminic nitrogen and phenolic oxygen atoms. Elemental analysis indicated that lanthanide compounds were formed in a 1:2 stoichiometry (metal:ligand). In vitro biological evaluation was carried out using these complexes, exhibiting moderate cytotoxicity against six different human tumor cell lines (U251, human glioblastoma; HCT-15, colorectal carcinoma; MCF-7, breast epithelial adenocarcinoma; PC-3, prostate cancer; K562, myelogenous leukemia; SKLU-1, lung carcinoma) and lower toxicity against a non-cancerous cell line (COS-7, primate kidney). In addition, the antibacterial activity of the compounds was assessed against two gram-positive strains (Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 19115) and two gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27583) using the microdilution method. The results obtained show that the metal complexes exhibit higher biological activity than the free ligands, confirming a synergistic effect. Further benzimidazolyl-phenol derivatives were explored for the detection of bacteria using fluorescence imaging studies. Interestingly, the fluorescent properties of these compounds make them potential candidates to monitor the morphology of bacteria at different compound concentrations. Hence, the interaction of the ligand and complexes with model membranes mimicking those of bacteria was studied by using differential scanning calorimetry (DSC) and molecular dynamics (MD), showing that both compounds decreased the enthalpy of transition in two model membranes as the concentration of the compounds increased. In addition, the main transition temperature was slightly reduced as a result of these interactions.

Synthesis and structure of an aryl-selenenium(II) cation, [C34H41N4Se+]2[Hg(SeCN)4]2-, based on a 5-tert-butyl-1,3-bis-(1-pentyl-1H-benzimidazol-2-yl)benzene scaffold

In the title salt, bis-{[5-tert-butyl-1,3-bis-(1-pentyl-1H-benzimidazol-2-yl)benzene]selenium} tetra-kis-(seleno-cyanato)-mercury, (C34H41N4Se)2[Hg(SeCN)4], the aryl-selenenium cations, [C34H41N4Se]+, are linked through [Hg(SeCN)4]2- anions by C-H⋯N hydrogen bonds. In the cation, the geometry around the Se atom in the 5-tert-butyl-1,3-bis-(1-pentyl-1H-benzimidazol-2-yl)benzene scaffold is T-shaped, resulting from the coordination of Se by the C atom of the central aromatic ring and the N atoms of both of the benzimidazole moieties. The trans Se-N bond lengths are almost equal [2.087 (3) and 2.099 (3) Å] and the Se-C bond length is 1.886 (3) Å. The N-Se-N angle is 159.29 (11)°. The geometry around the HgII atom in the [Hg(SeCN)4]2- anion is distorted tetra-hedral, with Se-Hg-Se angles ranging from 88.78 (3) to 126.64 (2)°. In [Hg(SeCN)4]2-, the Hg-Se bonds are unsymmetrical [2.5972 (4) and 2.7242 (5) Å]. One of the pentyl substituents is disordered over two equivalent conformations, with occupancies of 0.852 (8) and 0.148 (8).

Synthesis and structure of arylselenium(ii) and aryltellurium(ii) cations based on rigid 5-tert-butyl-1,3-bis-(N-pentylbenzimidazol-2′-yl)benzenes

The transmetalation reactions of mercury precursor, [^Pentyl(N^C^N)HgCl] (19) with selenium and tellurium halides led to isolation of air stable NCN pincer based arylselenium(ii) and aryltellurium(ii) cations due to facile ionization of Se/Te halogen bond.

Structure of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzimidazol-3-ium) tetra-chlorido-mercurate(II)

In the title salt, (C34H44N4)[HgCl4], the [C34H44N4]2+ cations and [HgCl4]2- anions are linked by N-H⋯Cl hydrogen bonds. One of the two n-pentyl side chains was refined as disordered over two sets of sites, with occupancies of 0.733 (18) and 0.267 (18). The geometry around the HgII atom in the [HgCl4]2- anion is distorted tetra-hedral, with bond angles ranging from 98.16 (3) to 120.68 (3)°. In the [HgCl4]2- anion, there are two short Hg-Cl bonds [2.4120 (9) and 2.4171 (11) Å], one inter-mediate Hg-Cl bond [2.4716 (12) Å] and one long Hg-Cl bond [2.6579 (13) Å] for the Cl atom involved in a trifurcated hydrogen bond as an acceptor, including two N-H⋯Cl⋯H-N interactions as well as one C-H⋯Cl inter-action. There are several C-H⋯Cl inter-actions, with C⋯Cl distances ranging from 3.492 (3) to 3.796 (3) Å. These link the cations and anions into a zigzag chain along the c-axis direction. In addition, there are Cl⋯Cl halogen bonds, as well as π-π inter-actions, with centroid-to-centroid distances of 3.4765 (18) Å, which link one of the two benzimidazole moieties into dimeric units.

Structure of the mercury(II) mixed-halide (Br/Cl) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzo[d]imidazole)

The mercury(II) complex of 2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benz-imidazole), namely catena-poly[[dihalogenido-mercury(II)]-μ-2,2'-(5-tert-butyl-1,3-phenyl-ene)bis-(1-pentyl-1H-benzimidazole)-κ2N3:N3'], [HgBr1.52Cl0.48(C34H42N4)], 2, has a polymeric structure bridging via the N atoms from the benzimidazole moieties of the ligand. The compound crystallizes in the ortho-rhom-bic space group Pca21 and is a racemic twin [BASF = 0.402 (9)]. The geometry around the HgII atom is distorted tetra-hedral, with the HgII atom coordinated to two N atoms, one Br atom, and a fourth coordination site is occupied by a mixed halide (Br/Cl). For the two ligands in the asymmetric unit, there is disorder with one of the two tert-butyl groups and benzimidazole moieties showing twofold disorder, with occupancy factors of 0.57 (2):0.43 (2) for the tert-butyl group and 0.73 (3):0.27 (3) for the benzimidazole group. In addition, there is threefold disorder for two of the four n-pentyl groups, with occupancy factors of 0.669 (4):0.177 (4):0.154 (4) and 0.662 (4):0.224 (4):0.154 (4), respectively. The mol-ecules form a one-dimensional helical polymer propagating in the b-axis direction. The helices are held together by intra-strand C-H⋯Br and C-H⋯Cl inter-actions. Each strand is further linked by inter-strand C-H⋯Br and C-H⋯Cl inter-actions. In addition, there are weak C-H⋯N inter-strand inter-actions which further stabilize the structural arrangement.