Benzimidazole Ring Research Articles

Broad-spectrum detection of benzimidazoles with lateral flow immunoassay: A computational chemistry-assisted hapten design strategy and explore of molecular recognition mechanism

Benzimidazoles (BMZs) are a class of veterinary drugs with a benzimidazole ring, the abuse of which poses a serious threat to ecological balance and human health. Consequently, the development of broad-spectrum antibodies and rapid assays are crucial for detecting BMZs in food samples. Herein, we scientifically designed three hapten structures, predicted the availability of the hapten with computational chemistry, and subsequently verified the broad-spectrum with immunological experiments. A broad-spectrum monoclonal antibody (6F10) was prepared based on the predicted hapten-2. Molecular recognition studies illustrated intricate interactions between mAb 6F10 binding to BMZs attributed to halogen bonds and π-π/π-alkyl interactions, revealing key amino acid sites and demonstrating the reliability of the hapten prediction strategies. Finally, a broad-spectrum, rapid, and sensitive lateral flow immunoassay based on aggregation-induced emission microspheres with high fluorescence intensity was established. The LOD values of the proposed method for eight kinds of BMZs were 0.027, 0.032, 0.058, 0.091, 0.087, 0.246, 0.369, and 0.311 ng mL−1, respectively. In this work, a hapten prediction strategy based on a computational chemistry method effectively guided the preparation of antibodies for broad-spectrum recognition of BMZs, and the molecular recognition studies verified the interaction of mAb 6F10 with BMZs, enabling broad-spectrum and sensitive detection of BMZs in milk.

Identification of 5-aminometonitazene and 5-acetamidometonitazene in a post-mortem case: Are nitro-nitazenes unstable?

In recent years the use of 2-benzylbenzimidazole opioids ('nitazenes') has increased with them becoming one of the most prominent synthetic opioid subclasses of novel psychoactive substances. With the increased prevalence there is also a concern of the dangers to public health with the use of nitazenes due to their high potency especially with polypharmacy. To aid in the detection of such compounds it is important that forensic toxicology laboratories maintain up-to-date compound libraries for drug screening methods and that sensitive analytical instrumentation is available to detect the low blood/plasma concentrations of more potent drugs. This includes not only the compounds themselves but also potential metabolites and/or degradation products. Metonitazene is a 'nitro-nitazene' with a nitro group at position 5 of the benzimidazole ring. As a nitro-nitazene there is a potential for bacterial degradation of metonitazene to 5-aminometonitazene, as occurs with nitro-benzodiazepines. In this study we provide evidence from a post-mortem case of degradation of metonitazene in unpreserved post-mortem blood using LC-QQQ-MS, and putative identification of the degradation/ metabolic products 5-aminometonitazene and 5-acetamidometonitazene by LC-QTOF-MS. The results from LC-QQQ-MS analysis indicated that there did not appear to be such degradation in preserved (fluoride/oxalate) blood. These results suggest that nitro-nitazenes may be subject to similar in vitro stability/degradation issues as nitro-benzodiazepines. These breakdown products should be added to instrument libraries to aid in the detection of the use of nitro-nitazenes, and nitro-nitazenes should be quantified in preserved blood samples where available.

Benzimidazole‐Containing Compounds as Anticancer Agents

AbstractCancer is the second leading cause of death today and remains a threat to human health. The advent of multi‐drug resistance and adverse effects make the current first‐line anti‐cancer medicines inadequate, despite the fact that numerous efforts have been made in the field of cancer therapy and significant progress has been made in the diagnosis and treatment of cancer. Consequently, the development of novel anticancer drugs with high activity and minimal toxicity is imperative. The benzimidazole ring has attracted the attention of medicinal chemists due to its medicinal and pharmacological properties. The heterocyclic pharmacophore of benzimidazole is a crucial scaffold for developing pharmaceuticals and drugs. In this review, we summarized the recent progress of benzimidazole as a privileged scaffold for the discovery of anti‐cancer agents based on biological targets, such as VEGFR (Vascular Endothelial Growth Factor), PI3 K inhibitors (Phosphoinositide 3‐kinase), EGFR kinase inhibitors (Epidermal Growth Factor Receptor), PARPs (Poly ADP‐ribose polymerases), Tubulin Polymerization, HAT/HDAC (histone acetylase/histone deacetylase), SphK1 (Sphingosine kinase‐1 inhibitors), aromatase, carbonic anhydrase, and topoisomerase inhibitors. The last 5 years of literature have been reviewed and relevant studies have been summarized in this review.

Anion Modulation of Ag-Imidazole Cuboctahedral Cage Microenvironments for Efficient Electrocatalytic CO2 Reduction.

How to achieve CO2 electroreduction in high efficiency is a current challenge with the mechanism not well understood yet. The metal-organic cages with multiple metal sites, tunable active centers, and well-defined microenvironments may provide a promising catalyst model. Here, we report self-assembly of Ag4L4 type cuboctahedral cages from coordination dynamic Ag+ ion and triangular imidazolyl ligand 1,3,5-tris(1-benzylbenzimidazol-2-yl) benzene (Ag-MOC-X, X=NO3, ClO4, BF4) via anion template effect. Notably, Ag-MOC-NO3 achieves the highest CO faradaic efficiency in pH-universal electrolytes of 86.1 % (acidic), 94.1 % (neutral) and 95.3 % (alkaline), much higher than those of Ag-MOC-ClO4 and Ag-MOC-BF4 with just different counter anions. In situ attenuated total reflection Fourier transform infrared spectroscopy observes formation of vital intermediate *COOH for CO2-to-CO conversion. The density functional theory calculations suggest that the adsorption of CO2 on unsaturated Ag-site is stabilized by C-H⋅⋅⋅O hydrogen-bonding of CO2 in a microenvironment surrounded by three benzimidazole rings, and the activation of CO2 is dependent on the coordination dynamics of Ag-centers modulated by the hosted anions through Ag⋅⋅⋅X interactions. This work offers a supramolecular electrocatalytic strategy based on Ag-coordination geometry and host-guest interaction regulation of MOCs as high-efficient electrocatalysts for CO2 reduction to CO which is a key intermediate in chemical industry process.

Anion Modulation of Ag‐Imidazole Cuboctahedral Cage Microenvironments for Efficient Electrocatalytic CO2 Reduction

AbstractHow to achieve CO2 electroreduction in high efficiency is a current challenge with the mechanism not well understood yet. The metal‐organic cages with multiple metal sites, tunable active centers, and well‐defined microenvironments may provide a promising catalyst model. Here, we report self‐assembly of Ag4L4 type cuboctahedral cages from coordination dynamic Ag+ ion and triangular imidazolyl ligand 1,3,5‐tris(1‐benzylbenzimidazol‐2‐yl) benzene (Ag‐MOC‐X, X=NO3, ClO4, BF4) via anion template effect. Notably, Ag‐MOC‐NO3 achieves the highest CO faradaic efficiency in pH‐universal electrolytes of 86.1 % (acidic), 94.1 % (neutral) and 95.3 % (alkaline), much higher than those of Ag‐MOC‐ClO4 and Ag‐MOC‐BF4 with just different counter anions. In situ attenuated total reflection Fourier transform infrared spectroscopy observes formation of vital intermediate *COOH for CO2‐to‐CO conversion. The density functional theory calculations suggest that the adsorption of CO2 on unsaturated Ag‐site is stabilized by C−H⋅⋅⋅O hydrogen‐bonding of CO2 in a microenvironment surrounded by three benzimidazole rings, and the activation of CO2 is dependent on the coordination dynamics of Ag‐centers modulated by the hosted anions through Ag⋅⋅⋅X interactions. This work offers a supramolecular electrocatalytic strategy based on Ag‐coordination geometry and host–guest interaction regulation of MOCs as high‐efficient electrocatalysts for CO2 reduction to CO which is a key intermediate in chemical industry process.

A chlorinated benzimidazole fluorescent probe for sensitive and rapid detection of iron and ferrous ions

A ‘off-on’ benzimidazole-based fluorescent probe ((E)-2-((4-(5-chloro-1H-benzo[d]imidazole-2-yl)benzylidene)amino)phenol) probe CBAP for the detection of Fe3+/2+ (probe CBAP) was developed. It didn't exhibit fluoresce at 450 nm in EtOH: H2O (v:v = 9:1), which was mainly attributed to the isomerization and rotation of the CN bond. The dihedral angle rotation hindered the charge transfer between benzimidazole and o-aminophenol. However, the CN in probe CBAP was cleaved to form compound 3 upon adding Fe3+/2+. Its electrons were transferred from the benzimidazole ring to the benzaldehyde portion upon excitation and showed blue-green fluorescence. Probe CBAP had high selectivity and sensitivity, with a detection limit as low as 1.12 nM, and didn't interfere with other analytes. In addition, the optimized structure and orbital energy levels of probe CBAP and compound 3 were calculated using time-varying density functional theory (TD-DFT) and PBE0 function. Moreover, the application of probe CBAP on mobile phones for rapid detection of Fe3+/2+ content in wine and confirmation of whether it exceeded the standard was explored.

In vitro structure-activity relationships and forensic case series of emerging 2-benzylbenzimidazole 'nitazene' opioids.

2-Benzylbenzimidazole 'nitazene' opioids are presenting a growing threat to public health. Although various nitazenes were previously studied, systematic comparisons of the effects of different structural modifications to the 2-benzylbenzimidazole core structure on μ-opioid receptor (MOR) activity are limited. Here, we assessed in vitro structure-activity relationships of 9 previously uncharacterized nitazenes alongside known structural analogues. Specifically, we focused on MOR activation by 'ring' substituted analogues (i.e., N-pyrrolidino and N-piperidinyl modifications), 'desnitazene' analogues (lacking the 5-nitro group), and N-desethyl analogues. The results from two in vitro MOR activation assays (β-arrestin 2 recruitment and inhibition of cAMP accumulation) showed that 'ring' modifications overall yield highly active drugs. With the exception of 4'-OH analogues (which are metabolites), N-pyrrolidino substitutions were generally more favorable for MOR activation than N-piperidine substitutions. Furthermore, removal of the 5-nitro group on the benzimidazole ring consistently caused a pronounced decrease in potency. The N-desethyl modifications showed important MOR activity, and generally resulted in a slightly lowered potency than comparator nitazenes. Intriguingly, N-desethyl isotonitazene was the exception and was consistently more potent than isotonitazene. Complementing the in vitro findings and demonstrating the high harm potential associated with many of these compounds, we describe 85 forensic cases from North America and the United Kingdom involving etodesnitazene, N-desethyl etonitazene, N-desethyl isotonitazene, N-pyrrolidino metonitazene, and N-pyrrolidino protonitazene. The low-to-sub ng/mL blood concentrations observed in most cases underscore the drugs' high potencies. Taken together, by bridging pharmacology and case data, this study may aid to increase awareness and guide legislative and public health efforts.

A fast, convenient and stable fluorescent probe for detecting Fe3+/2+ and its applications

A turn-on benzimidazole-based fluorescent probe (E)-2-((4-(5-bromo-1H-benzo[d]imidazole-2-yl)benzylidene)amino)phenol (BRAP) for the detection of Fe3+/2+ was developed. The probe BRAP was designed and synthesized using 2-hydroxyaniline as the recognition site and benzimidazole as the fluorophore. It was highly selective and sensitive with a detection limit as low as 2.1 × 10−8 mol/L and didn't interfere with other analytes. Using EtOH: H2O (v:v = 9:1) as the detection system, BRAP had non-fluorescence at 466 nm, which was mainly due to isomerization and rotation of the CN bond. The dihedral angle rotation hindered the charge transfer between benzimidazole and 2-hydroxyaniline. However, upon the addition of Fe3+/2+, the CN bond in probe BRAP was cleaved to form compound 3, whose electrons were transferred from the benzimidazole ring to the benzaldehyde portion upon excitation and showed blue fluorescence. In addition, the optimized structure and orbital energies of probe BRAP and its products were calculated by comparing three functional combinations with time-dependent density functional theory (TD-DFT) and the optimal functional and basis set [B3LYP/6-311 + G(d,p)]. In addition, the probe BRAP combined with a smartphone was explored for the rapid detection of Fe3+/2+ in wine.

Antiproliferative and Pro-Apoptotic Activity and Tubulin Dynamics Modulation of 1H-Benzimidazol-2-yl Hydrazones in Human Breast Cancer Cell Line MDA-MB-231.

(1) Background: The aim of the work is the evaluation of in vitro antiproliferative and pro-apoptotic activity of four benzimidazole derivatives containing colchicine-like and catechol-like moieties with methyl group substitution in the benzimidazole ring against highly invasive breast cancer cell line MDA-MB-231 and their related impairment of tubulin dynamics. (2) Methods: The antiproliferative activity was assessed with the MTT assay. Alterations in tubulin polymerization were evaluated with an in vitro tubulin polymerization assay and a docking analysis. (3) Results: All derivatives showed time-dependent cytotoxicity with IC50 varying from 40 to 60 μM after 48 h and between 13 and 20 μM after 72 h. Immunofluorescent and DAPI staining revealed the pro-apoptotic potential of benzimidazole derivatives and their effect on tubulin dynamics in living cells. Compound 5d prevented tubulin aggregation and blocked mitosis, highlighting the importance of the methyl group and the colchicine-like fragment. (4) Conclusions: The benzimidazole derivatives demonstrated moderate cytotoxicity towards MDA-MB-231 by retarding the initial phase of tubulin polymerization. The derivative 5d containing a colchicine-like moiety and methyl group substitution in the benzimidazole ring showed potential as an antiproliferative agent and microtubule destabilizer by facilitating faster microtubule aggregation and disrupting cellular and nuclear integrity.

The Synthesis and Antibacterial Activity of N-((1H-benzimidazol-2- yl)methyl)-2-substituted-3H- benzimidazol-5-amine Derivatives

Abstract: The increasing commonality of multi-drug-resistant bacteria as well as fungi is the motive for the development of new active antimicrobial agents. Heterocyclic compounds are major contributors in medical chemistry and are also found in biomolecules like vitamins, enzymes, natural products, etc. Benzimidazole is one of the nitrogens-containing heterocyclic compounds. Derivatives of benzimidazole have been found active against various bacterial diseases. Benzimidazole derivatives containing two benzimidazole rings also showed various pharmacological activities. In view of these, we aim to synthesize a new series of benzimidazole derivatives, N-((1H-benzimidazol-2-yl)methyl)-2-substituted-3H- benzimidazol-5-amine (6a–f) by the reaction of substituted 5-aminobenzimidazol derivatives with 2-chloromethyl benzimidazole and study their predicted bioactivity and actual antibacterial activity. To confirm the structures of the synthesized compounds, spectroscopic techniques like IR, 1H NMR,13C NMR and mass spectra were used. Initially, predicted bioactivity was studied using Molinspiration software. Among the synthesized compounds (6a-f), compounds 6a, 6d, 6e, and 6f showed good predicted activity. Then all the synthesized compounds 6a–f were screened for their antibacterial activity against E. coli (NCIM-2931), S. aureus (NCIM-2079), K. pnuemoniae (NCIM-2719) and P. aeruginosa (NCIM-2053) bacterial strains using the Ditchplate and Well Diffusion Method. Among them, compound 6f was found to be active against all used bacterial strains. Objectives: Synthesis and study of antimicrobial activity of benzimidazole derivatives. Methods: Simple, known laboratory methods are used for the synthesis of all new benzimidazole derivatives (6a-f). Predicted bioactivity was studied using Molinspiration software. The antibacterial activity of synthesized derivatives was studied against E. coli (NCIM-2931), S. aureus (NCIM-2079), K. pnuemoniae (NCIM-2719) and P. aeruginosa (NCIM-2053) bacterial strains using Ditch-plate and Well diffusion methods. Results: We successfully synthesized new bis-benzimidazole derivatives using simple laboratory methods and studied their antimicrobial activity. Among the synthesized derivatives, N-((1H-benzimidazol-2-yl)methyl)-2-(pyridin-3-yl)-3H-benzimidazol-5-amine (6f) showed good activity against used bacterial strains. Conclusion: In this paper, we report the synthesis of novel and biological activity benzimidazole derivatives by a simple and efficient method. The carried out predicted bioactivity as well as actual bioactivity was reported, and it was observed that predicted bioactivity and actual antibacterial activity showed similar results. The incorporation of a pyridine ring in a benzimidazole derivative increased bioactivity.

Benzimidazole and Benzoxazole Derivatives Against Alzheimer's Disease.

Benzimidazole and benzoxazole derivatives are included in the category of medical drugs in a wide range of areas such as anticancer, anticoagulant, antihypertensive, anti- inflammatory, antimicrobial, antiparasitic, antiviral, antioxidant, immunomodulators, proton pump inhibitors, hormone modulators, etc. Many researchers have focused on synthesizing more effective benzimidazole and benzoxazole derivatives for screening various biological activities. In addition, there are benzimidazole and benzoxazole rings as bioisosteres of aromatic rings found in drugs used in the treatment of Alzheimer's disease. Because of the diverse activity of the benzimidazole and benzoxazole rings and bioisosteres marketed as drugs for Alzheimer Diseases, designed compounds containing these rings are likely to be effective against Alzheimer's disease. In this study, the effectiveness of compounds containing benzimidazole and benzoxazole rings against Alzheimer's disease will be examined.

Highly Efficient N‐Heterocyclic Carbene Precursor from Sterically Hindered Benzimidazolium Salt for Benzoin Condensation

AbstractA diverse array of simple benzoin compounds featuring aryl and heteroaryl substituents were prepared from corresponding aldehydes, achieving moderate to excellent yields. To achieve this, a library of NHC precursors was designed and synthesized from imidazole and benzimidazole. Our custom‐designed NHC precursors (L1–L10) varied in size and structure. Built on imidazolinium and benzimidazolinium salts, these catalysts sported substituents at the N1 and N3 positions ranging from compact groups like butyl or benzyl to the much bulkier anthracenyl group. Treatment with a base transforms these salts into highly effective NHC precursors. After being activated, these NHCs become highly effective catalysts for the benzoin condensation reaction. We tested all the NHC precursors we made and found that L10, the one containing the large and bulky anthracenyl group attached to a benzimidazolium ring, worked the best for making benzoin derivatives.

Research Progress on Benzimidazole Fungicides: A Review.

Benzimidazole fungicides are a class of highly effective, low-toxicity, systemic broad-spectrum fungicides developed in the 1960s and 1970s, based on the fungicidal activity of the benzimidazole ring structure. They exhibit biological activities including anticancer, antibacterial, and antiparasitic effects. Due to their particularly outstanding antibacterial properties, they are widely used in agriculture to prevent and control various plant diseases caused by fungi. The main products of benzimidazole fungicides include benomyl, carbendazim, thiabendazole, albendazole, thiophanate, thiophanate-methyl, fuberidazole, methyl (1-{[(5-cyanopentyl)amino]carbonyl}-1H-benzimidazol-2-yl) carbamate, and carbendazim salicylate. This article mainly reviews the physicochemical properties, toxicological properties, disease control efficacy, and pesticide residue and detection technologies of the aforementioned nine benzimidazole fungicides and their main metabolite (2-aminobenzimidazole). On this basis, a brief outlook on the future research directions of benzimidazole fungicides is presented.

Receptor-based pharmacophore modeling, molecular docking, synthesis and biological evaluation of novel VEGFR-2, FGFR-1, and BRAF multi-kinase inhibitors

A receptor-based pharmacophore model describing the binding features required for the multi-kinase inhibition of the target kinases (VEGFR-2, FGFR-1, and BRAF) were constructed and validated. It showed a good overall quality in discriminating between the active and the inactive in a compiled test set compounds with F1 score of 0.502 and Mathew’s correlation coefficient of 0.513. It described the ligand binding to the hinge region Cys or Ala, the glutamate residue of the Glu-Lys αC helix conserved pair, the DFG motif Asp at the activation loop, and the allosteric back pocket next to the ATP binding site. Moreover, excluded volumes were used to define the steric extent of the binding sites. The application of the developed pharmacophore model in virtual screening of an in-house scaffold dataset resulted in the identification of a benzimidazole-based scaffold as a promising hit within the dataset. Compounds 8a-u were designed through structural optimization of the hit benzimidazole-based scaffold through (un)substituted aryl substitution on 2 and 5 positions of the benzimidazole ring. Molecular docking simulations and ADME properties predictions confirmed the promising characteristics of the designed compounds in terms of binding affinity and pharmacokinetic properties, respectively. The designed compounds 8a-u were synthesized, and they demonstrated moderate to potent VEGFR-2 inhibitory activity at 10 µM. Compound 8u exhibited a potent inhibitory activity against the target kinases (VEGFR-2, FGFR-1, and BRAF) with IC50 values of 0.93, 3.74, 0.25 µM, respectively. The benzimidazole derivatives 8a-u were all selected by the NCI (USA) to conduct their anti-proliferation screening. Compounds 8a and 8d resulted in a potent mean growth inhibition % (GI%) of 97.73% and 92.51%, respectively. Whereas compounds 8h, 8j, 8k, 8o, 8q, 8r, and 8u showed a mean GI% > 100% (lethal effect). The most potent compounds on the NCI panel of 60 different cancer cell lines were progressed further to NCI five-dose testing. The benzimidazole derivatives 8a, 8d, 8h, 8j, 8k, 8o, 8q, 8r and 8u exhibited potent anticancer activity on the tested cell lines reaching sub-micromolar range. Moreover, 8u was found to induce cell cycle arrest of MCF-7 cell line at the G2/M phase and accumulating cells at the sub-G1 phase as a result of cell apoptosis.

Self-Assembled Molecular Complexes of 1,10-Phenanthroline and 2-Aminobenzimidazoles: Synthesis, Structure Investigations, and Cytotoxic Properties.

Three new molecular complexes (phen)3(2-amino-Bz)2(H+)(BF4-)·3H2O 5, (phen)3(2-amino-5(6)-methyl-Bz)2(H+)(BF4-)·H2O 6, and (phen)(1-methyl-2-amino-Bz)(H+)(BF4-) 7, were prepared by self-assembly of 1,10-phenanthroline (phen) and various substituted 2-aminobenzimidazoles. Confirmation of their structures was established through spectroscopic methods and elemental analysis. The X-ray diffraction analysis revealed that the crystal structure of 7 is stabilized by the formation of hydrogen bonds and short contacts. In addition, the molecular geometry and electron structure of molecules 5 and 6 were theoretically evaluated using density functional theory (DFT) methods. According to the DFT B3LYP/6-311+G* calculations, the protonated benzimidazole (Bz) units act as NH hydrogen bond donors, binding two phenanthrolines and a BF4- ion. Non-protonated Bz unit form hydrogen bonds with the N-atoms of a third molecule phen. The molecular assembly is held together by π-π stacking between benzimidazole and phenanthroline rings, allowing for N-atoms to associate with water molecules. The complexes were tested in vitro for their tumor cell growth inhibitory effects on prostate (PC3), breast (MDA-MB-231 and MCF-7), and cervical (HeLa) cancer cell lines using MTT-dye reduction assay. The in vitro cytotoxicity analysis and spectrophotometric investigation in the presence of ct-DNA, showed that self-assembled molecules 5-7 are promising DNA-binding anticancer agents warranting further in-depth exploration.

Study on the host-guest interactions between tetramethyl cucurbit[6]uril and 2-heterocyclic-substituted benzimidazoles.

Cucurbit[n]urils (Q[n]s) are a class of supramolecular host compounds with hydrophilic carbonyl ports and hydrophobic cavities, which can selectively form host-guest inclusion complexes with guest molecules to change the properties of guest molecules. In this paper, tetramethyl cucurbit[6]uril (TMeQ[6]) was used as the host and three 2-heterocyclic substituted benzimidazole derivatives as the guests, and their modes of interaction were investigated using X-ray crystallography, 1H NMR spectrometry, and other analytical techniques. The results showed that TMeQ[6] formed a 1 : 1 host-guest inclusion complex with three guest molecules, and the binding process between them was mainly enthalpy-driven. The X-ray diffraction analysis indicated that the main driving forces for the formation of these three inclusion complexes included hydrogen bonding interactions and ion dipole interactions. There are two modes of interaction between G3 and TMeQ[6] in the liquid phase, indicating that the benzimidazole ring and heterocyclic substituents on the guest molecule compete with the cavity of TMeQ[6]. Besides, the addition of TMeQ[6] significantly enhanced the fluorescence of these guests and slightly improved their solubility.

Neutral 2-phenylbenzimidazole-based iridium(III) complexes with picolinate ancillary ligand: tuning the emission properties by manipulating the substituent on the benzimidazole ring.

We report the synthesis and characterization of ten neutral bisheteroleptic iridium(III) complexes with 2-phenylbenzimidazole cyclometallating ligand and picolinate as ancillary ligand. The 2-phenylbenzimidazole has been modified by selected substituents introduced on the cyclometallating ring and/or on the benzimidazole moiety. The integrity of the complexes has been assessed by NMR spectroscopy, by high-resolution mass spectrometry and by elemental analysis. The complexes are demonstrated to be highly phosphorescent at room temperature and a luminescence study with comprehensive ab initio calculations allow us to determine the lowest emitting excited state which depends on the substituent nature and its position on the cyclometallating ligand.

Structural regulation of NHC-protected copper(i) clusters through substitution for photoluminescence enhancement

The Cu(i) clusters with Cu2, Cu3 and Cu4 kernel can be synthesized by simply changing the N-substituents onto benzimidazole ring, which could be explained by synergistic effect of steric and electronic properties. Among them, Cu2 exhibited admirable luminescence and processability.

2‐Aryl Imidazolium Salts as Potential Bladder Cancer Chemotherapeutic Candidates

AbstractAs potential intravesical exfoliants for the treatment of bladder cancer, four new imdiazolium salts have been prepared. These compounds are modified on the nitrogen positions of the 4,5‐diphenyl‐1H‐imidazole or benzimidazole rings with naphthalen‐2‐ylmethyl groups, and the 2 positions on the azolium cations are occupied by arene rings. The 4,5‐diphenyl‐1H‐imidazole and benzimidazole precursors are produced from 1,2‐phenylenediamine and benzil respectively, and the imidazolium cations are generated from sequential alkylation of the nitrogen positions using 2‐bromomethyl naphthalene. The four imidazolium salts were screened for their chemotherapuetic activity using the NCI‐60 Human Tumour Cell Line Screen, and we observed that the cytotoxicity was more dependent on the identity of the imidazolium group (benzimidazolium versus diphenylimidazolium) rather than on the 2‐aryl position structure.

Divergent Synthesis of 3-(Indol-2-yl)quinoxalin-2-ones and 4-(Benzimidazol-2-yl)-3-methyl(aryl)cinnolines via Polyphosphoric Acid (PPA)-Mediated Intramolecular Rearrangements of 3-(Methyl/aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones.

Herein, we report a polyphosphoric acid (PPA)-mediated divergent metal-free operation to access a diverse collection of 3-(indol-2-yl)quinoxalin-2-ones and 4-(benzimidazol-2-yl)-3-methylcinnolines in moderate to excellent overall yields. The described process involves two distinct, and competing rearrangements of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, namely [3,3]-sigmatropic Fischer rearrangement with the formation of an indole ring to produce 3-(indol-2-yl)-quinoxalin-2-ones, and Mamedov rearrangement with simultaneous construction of benzimidazole and cinnoline rings to form the new biheterocyclic system─4-(benzimidazol-2-yl)-3-methylcinnolines. The reaction mechanism of both rearrangement channels is explored by extensive dispersion-corrected DFT calculations. It is partcularly remarkable that when 3-(aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones is used, instead of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, reactions proceed regioselectively with the formation of only rearrangement products─4-(benzimidazol-2-yl)-3-arylcinnolines with high yields. This operationally simple protocol enables a rapid access to these scaffolds and is compatible with a wide scope of starting materials. In addition, the new rearrangement found features a promising approach for the design of unique compound libraries for drug design and discovery programs.