Bis Benzimidazole Ligands Research Articles

Chemical Repair of Radical Damage to the GC Base Pair by DNA-Bound Bisbenzimidazoles.

The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC• pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio (r) ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC• pair neutral radical of ca. 1.54 V and that of the ligand radicals (E0', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus r give a common intercept at r = 0 and a free energy change of 12.2 ± 0.3 kcal mol-1, ascribed to the GC• pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, R, from the GC• pair radical, k2, is described by the relationship k2 = k0 exp(constant/R), where k0 includes the rate constant for surmounting a small barrier.

Synthesis, characterization, antibacterial and antioxidant activity of 1,5-bis(6-chloro-1H-benzimidazol-2-yl)pentan-3-one and its Fe(III), Co(II), Cu(II), Zn(II) and Ru(II) complexes

A new bis-benzimidazole ligand, 1,5-bis(6-chloro-1H-benzimidazol-2-yl)pentan-3-one (L, C19H16Cl2N4O), and its complexes with Fe(III), Co(II), Cu(II), Zn(II) and Ru(II) chlorides are synthesized and characterized by elemental analysis, molar conductivity, magnetic moment, TGA, FT-IR, 1H-NMR, fluorescence and UV-visible spectroscopy. The spectral data suggest that the chelating ligand acted as tridentate towards to Cu(II) ion however bidentate in the other complexes. According to the molar conductance data, [Fe(L)2Cl2]Cl•2H2O and [Cu(L)Cl]Cl•2H2O complexes are 1:1 electrolytes whereas [Co(L)Cl2]•2H2O, [Zn(L)(Cl)2(H2O)]•H2O and [Ru(L)(DMSO)(H2O)Cl2] complexes are non-ionic. In addition, antibacterial and antioxidant activity of the compounds were tested. The Ru(II) and Co(II) complexes showed moderate activity against to all tested bacteria whereas the ligand itself had no activity. According to the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•) scavenging results, the Ru(II) complex of L had quite significant radical scavenging activity almost the same as that of 3,5-di-tert-4-butylhydroxytoluene (BHT), a commercial standard.

Study on the Luminescence and Coordination Behavior of Semi‐rigid Dual‐Benzimidazole Ligands and Complexes

AbstractIn this work, two novel semi‐rigid bisbenzimidazole ligands with different substituents (L1,2‐H; L2,2H‐methyl; L3, 2H‐ethyl; L4, 2H‐isopropyl; L5, 2H‐tertbutyl, which L1‐L3 have been reported,[19,20]to compare the effects of different substituents on properties, herein, we re‐synthesize them) and two coordination compounds are synthesized. Single crystal structure X‐ray diffraction data suggests that the ligand(L1) exhibits boat‐like configuration in the crystal lattice which makes the compound 1 crystallizes in the polar space group (C2), otherwise, chair‐like structure of ligands (L2‐L4) makes compound 2–4 grow in centrosymmetric space group (C2/c). Interestingly, polar compound 1 demonstrates typical ferroelectric behavior with remnant electric polarization (Pr) of 0.308 μC/cm2 and an electric coercive field (Ec) of 20 kV/cm. In addition, the fluorescence of the compounds 1–4 all are in the blue‐violet light region under the combined action of metal ions and organic ligands. Notably, L5 emits bright charming orange light at 365 nm UV light, and we also verified the reason and possibility of luminescence through density functional theory (DFT) calculations. Besides, the photoluminescence quantum yield (PLQY) of the L5 is up to 24.6 % and fluorescence lifetime is 3.29 ns. In short, this work might provide strategy to construct metal organic frameworks (MOFs) with ferroelectric and photoluminescent properties.

Synthesis, structure and electrochemical H2O2-sensing of two silver(I) complexes with bisbenzimidazole ligands

Two new binuclear Ag(I) complexes of the types, [Ag2(Mebba)2(fumarate)]·2C2H5OH (1) and [Ag2(Meobb)2(μ-Cl)2] (2) (Mebba = bis(N-methylbenzimidazol-2-ylmethyl) aniline, Meobb = 1,3-bis(N-ethyl-benzimidazol-2-yl)-2-oxopropan), have been synthesized and characterized. Structural analysis showed that silver(I) centre in two complexes were both four-coordinated distorted tetrahedron geometry, but their bridging modes are significantly different: bridged by the fumarate in complex 1, μ2-Cl monoatomic bridging in complex 2. The electrochemical sensing performances of carbon paste electrode modified with silver(I) complex 1 (CPE-1) and complex 2 (CPE-2) towards H2O2 were investigated by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6) at −0.2 V. The CPE-1 exhibits a wide linear detection range from 0.5 μM to 4.0 mM and lower detection limit 0.61 μM with a relatively high sensitivity of 9.9935 µA/mM, and has excellent anti-interference ability and stability. There is not electrochemical H2O2-sensing performance for the CPE-2, which may be due to the fact that silver(I) ions and chloride ions form a more stable complex that is not easy to combine with hydrogen peroxide to form a catalytic transition state. The research results show that silver(I) complexes based on bisbenzimidazole ligands have the potential to become electrode materials.

A zinc(II) coordination polymer based on a flexible bis(benzimidazole) ligand: synthesis, crystal structure and fluorescence study

Abstract A new one-dimensional Zn(II) coordination polymer, {[ZnCl2(BBM)]·CH3OH} n (2,2-(1,4-butanediyl)bis-1,3-benzimidazole [BBM]), has been obtained from the hydrothermal reaction of zinc chloride with the flexible bis-benzimidazole ligand BBM and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–vis spectra. Structural analysis has revealed that the BBM ligand connects the Zn(II) atoms to form a square-wave chain, which is further extended into supramolecular layers through hydrogen bonds and π···π stacking interactions. Solid-state fluorescence investigations showed that the Zn(II) coordination polymer has an emission peak at 381 nm upon excitation at 330 nm, which is attributed to ligand-centered luminescence. It is only slightly red shifted as compared to the ligand but partially quenched due to the strong π···π stacking interactions.

Substituent-controlled Constructions of M2L4 Cage and 1D Network Structures for Cu(II) Complexes with Bis-benzimidazole Ligands

Multicopper(II) complexes were synthesized using bis-benzimidazole ligands expressed as B–CH2–C6R4–CH2–B (B = benzimidazole, R = Me (bbitrb), OMe (bbitrmob)). For the reactions with Cu(ClO4)2·6H2O ...

Synthesis, structures and characterization of two cobalt(II) coordination polymers with 2,5-dichloroterephthalic acid and flexible bis(benzimidazole) ligands

Two Co(II) coordination polymers (CPs), namely [Co(L1)(DCTP)]n (1) and [Co(L2)(DCTP)]n (2) [L1 = 1,4-bis(5,6-dimethylbenzimidazol-1-yl)butane, L2 = 1,5-bis(5,6-dimethylbenzimidazol-1-yl)pentane, H2DCTP = 2,5-dichloroterephthalic acid] were synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, powder X-ray diffraction (PXRD) and infrared spectroscopy. CP 1 has a 2D (4,4) corrugated sheet structure, which is further extended into a 2D double layer by C–H···O weak hydrogen bonding interactions, while CP 2 displays a 2D layer with hcb network, which is assembled into a 3D supramolecular framework through C–H···O hydrogen bonding. Both CPs exhibited promising photocatalytic activities for the degradation of methylene blue under UV irradiation. In addition, the thermal stabilities and the luminescence properties of both CPs have been investigated.

BODIPY-based Ir(III) rectangles containing bis-benzimidazole ligands with highly selective toxicity obtained through self-assembly

Selectivity for cancerous cells over normal cells remains one of the most important issues in studies of the biological activities of metal-based drugs. Herein, we show that benzimidazole-based iridium BODIPY rectangles can be used to selectively kill cancer cells. New tetranuclear (2 + 2) metalla-rectangles 1 and 2 were synthesized through the self-assembly of benzimidazole and BODIPY ligands with dichloro (pentamethylcyclopentadienyl) iridium dimer. The new complexes were fully characterized using different analytical techniques and a single-crystal structure was obtained for rectangle 2. Cytotoxicity studies revealed that complex 1 is highly selective for cervical cancer cells (HeLa) and human glioblastoma (U87) cancer cells over non-malignant lung fibroblast cells (WI38). The selectivity of complex 1 is much superior than that of well-known drug cisplatin. The cellular uptake and intracellular localization of these complexes were examined through confocal microscopy studies, and complex 1 was found to localize primarily in the cytoplasmic region of cancer cells. Furthermore, the interactions of these complexes with biomolecules in solution were investigated through spectroscopic studies.

Syntheses, Crystal Structures, and Fluorescent Properties of Two Mixed-Ligand Cadmium Coordination Polymers Based on Dicarboxylate and Bis-benzimidazole Ligands

Two cadmium(II) coordination polymers, {[Cd2(HO-bdc)(Hbbop)2]}n (1), and {[Cd2(H2N-bdc)(Hbbop)2]·2(H2O)}n (2), (HO-H2bdc = 5-hydroxyisophthalic acid, H2N-H2bdc = 5-aminoisophthalic acid, and H2bbop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane) have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectra, single crystal X-ray diffraction, and thermogravimetric analyses. Their structures are 2D networks with (63) topology, which are further connected by hydrogen bonds to form 3D supramolecular architectures. Additionally, fluorescent properties of the two complexes are reported. Two 2D mixed-ligand cadmium coordination polymers with (63) topology were synthesized and characterized.

Synthesis, structural elucidation and DNA binding profile of Zn(II) bis-benzimidazole complexes

Complexes of zinc (II) (L1ZnBr2, L2ZnBr2) were prepared in good yields using bis-benzimidazole ligands with olefinic bridges and different substituents on the nitrogen atoms in the benzimidazole cores (L1=H, L2=Bz). The crystal structure of L2 was determined, showing that both benzimidazole rings and the carbon atoms of the olefinic bridge are coplanar with a slight deviation and that the benzyl substituent is perpendicular to this plane. Also, the crystal structure of L1ZnBr2 was determined showing that in coordinated L1, benzimidazole rings are out the plane with respect to the olefinic bridge, allowing their coordination through the nitrogen atoms to get a strain-free seven-membered ring, achieving a distorted tetrahedral geometry. Both crystal structures of L2 and L1ZnBr2 exhibit π-π stacking interactions that hold their supramolecular arrangement. All ligands and complexes were fully characterized. Additionally, through DNA binding studies using absorption spectral titrations it was possible to determine a slight hypochromism and bathochromism when ligands and complexes interact with calf thymus DNA in neat DMSO and 3% DMSO/Tris-HCl buffer, the spectral changes being consistent with partial intercalation. The intrinsic binding constant Kb of ligands and complexes are reported for each medium.

Two 3D Supramolecular Architectures Based on Cobalt(II) Coordination Polymers with Dichloroterephthalate and Semi-rigid Bis(benzimidazole) Ligands

Two Co(II) coordination polymers (CPs) [Co(DCTP)(L1)]n (1) and [Co(DCTP)(L2)·(H2O)2]n (2), were synthesized from hydrothermal reaction of Co2+ ions with the 2,5-dichloroterephthalic acid (H2DCTP) and two semi-rigid bis(benzimidazole) ligands (L1 = 1,3-bis(benzimidazol-1-ylmethyl)benzene, L2 = 1,2-bis(benzimidazol-1-ylmethyl)benzene), and structurally characterized by X-ray single crystal diffraction analysis and FT–IR. The thermal stabilities and luminescence properties of 1–2 were investigated. The two CPs exhibit 2D (4,4)-connected layer structures, which are further extended to 3D supramolecular architectures by π⋯π stacking interactions for 1 and classical O–H⋯O hydrogen-bonding interactions for 2, respectively. In addition, two complexes show promising photocatalytic activities for the degradation of methylene blue under UV irradiation.

Role of annealing on the structural and optical properties of nanostructured diaceto bis-benzimidazole Mn(II) complex thin films

A coordination complex, manganese incorporated benzimidazole, thin films were prepared by chemical bath deposition method. Structural characterization of the deposited films, carried out by Fourier transform infrared spectroscopy, Raman and electron paramagnetic resonance spectral analyses, reveals the distorted tetrahedral environment of the metal ion with bis-benzimidazole ligand. Further the molecular composition of the deposited metal complex was estimated by energy-dispersive X-ray spectroscopy. The prepared thin films were thermally treated to study the effect of annealing temperature on the surface morphology and the results showed that the surface homogeneity of the films increased for thermally treated films up to 150°C. But distortion and voids were observed for the films annealed at 200°C. The Raman analysis reveals the molecular hydrogen bond distortion which leads to the evaporation of the metal complex from the thin film surface with respect to annealing temperature. The linear and nonlinear optical properties of the as prepared and annealed films were studied using ultraviolet-visible transmittance spectroscopy, second harmonic generation and Z-scan analyses. Films annealed at 150°C show a better linear transmittance in the visible region and larger SHG efficiency and third order nonlinear susceptibility when compared with the other samples. Further, the film annealed at 150°C was subjected to optical switching analysis and demonstrated to have an inverted switching behavior.

Syntheses, crystal structures, and DNA binding and catalytic properties of two transition metal coordination polymers constructed from 5-aminoisophthalic acid and bis-benzimidazole ligands

Two mixed-ligand transition metal coordination polymers, {[Co(aip)(bbp)]·(H2O)} n (1) and {[Ni2(aip)(Hbbop)2]·(H2O)2} n (2) (H2aip = 5-aminoisophthalic acid, bbp = 1,3-bis(benzoimidazol-2-yl)propane, H2bbop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane), were synthesized and characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric analyses. Complex 1 has a 1D chain structure, while 2 has a 3-connected 2D network with (63) topology. Both structures are further connected by hydrogen bonds and π–π stacking interactions to form the 3D supramolecular architectures. DNA binding and catalytic properties of the two complexes were investigated.

Synthesis, characterization, and crystal structures of 2D cobalt(II) and nickel(II) coordination polymers containing flexible bis(benzimidazole) ligands

Three coordination polymers, namely {[Ni(L1)(nip)(H2O)]·2H2O} n (1), [Co(L2)(tbip)] n (2), and {[Co2(L3)2(bptc)]·3H2O} n (3) (L1 = 1,4-bis(5,6-dimethylbenzimidazole)butane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)-2-butylene, L3 = 1,3-bis(5,6-dimethylbenzimidazole)propane, H2nip = 5-nitro-isophthalic acid, H2tbip = 5-tert-butyl-isophthalic acid, H4bptc = biphenyl-3,3′,4,4′-tetracarboxylic acid), have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single-crystal X-ray diffraction analysis. Complexes 1 and 2 both feature a two-dimensional (4,4) layer with (44 × 62) topology. Complex 3 possesses a uninodal 4-connected 2D htb network. The fluorescence spectra and catalytic properties of the complexes for the degradation of methyl orange by sodium persulfate in a Fenton-like process are reported.

Synthesis, Structures, and Catalytic Properties of Two Zinc(II) Coordination Polymers Constructed from Polycarboxylate and Bis(Benzimidazole) Ligands

Two Zn(II) coordination polymers, formulated as {[Zn(L1)0.5(btc)0.5(H2O)]·H2O} n (1) and {[Zn(L2)(1,4-ndc)]·2H2O} n (2) [L1 = 1,4-bis(2-methylbenzimidazole-1-ylmethyl)benzene, L2 = 1,4-bis(2-methylbenzimidazole)butane, H4btc = butane-1,2,3,4-tetracarboxylic acid, 1,4-H2ndc = 1,4-naphthalenedicarboxylic acid] have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 features a 3D (3,4)-connected network with the topology of fsh-3,4-P21/c. Complex 2 is a 2D (4,4) grid with sql topology and further extends into a 3D supramolecular framework by π–π stacking interactions. In addition, the thermal stability, fluorescence, and catalytic properties of two complexes for degrading methyl orange dye in a Fenton-like process were investigated.

Synthesis and characterization of copper(II) and nickel(II) coordination polymers containing 2,6-naphthalenedicarboxylate and bis(benzimidazole) ligands

Two coordination polymers, namely [Ni(L1)-(ndc)(H2O)] n (1) and [Cu(L2)0.5(ndc)] n (2) (L1 = 1,3-bis(2-methylbenzimidazol-1-ylmethyl)benzene, L2 = 1,4-bis(2-methylbenzimidazole)butane, H2ndc = 2,6-naphthalenedicarboxylic acid) have been synthesized and characterized by single-crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Complex 1 features a 2D 3-connected hcb network with 63 topology, which is further extended into a 3D supramolecular framework by O–H···O hydrogen bonding interactions. Complex 2 possesses a 3D threefold interpenetrating (4,5)-connected xah topological network, and its Schlafli symbol is (42.62.82)(46.64). Both complexes exhibit intense luminescence emissions in the solid state and promising catalytic activities for the degradation of Congo red azo dye in a Fenton-like process.

Three 2D mixed-ligand Co(II) coordination polymers containing flexible bis(benzimidazole) ligands with different spacers

Three new Co(II) coordination polymers, [Co(L1)(bpdc)]n (1), [Co(L2)(ndc)(H2O)·2H2O]n (2) and [Co(L3)(ndc)(H2O)·H2O]n (3) (L1 = 1,2-bis(5,6-dimethylbenzimidazole)ethane, L2 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L3 = 1,4-bis(5,6-dimethylbenzimidazole)butane, H2bpdc = 4,4′-biphenyldicarboxylic acid, H2ndc = 2,6-naphthalenedicarboxylic acid) have been synthesized under hydrothermal conditions and structurally characterized by X-ray crystallography. All three complexes feature (4,4) networks that extend into 3D supramolecular frameworks via hydrogen bonding interactions. The luminescence properties and catalytic activities of these complexes with respect to the degradation of methyl orange in a Fenton-like process have been investigated.

Syntheses, crystal structures, DNA binding and electrochemical properties of two mixed-ligand cobalt(II) coordination polymers constructed from 5-(carboxymethoxy)isophthalic acid and bis-benzimidazole ligands

Two new cobalt(II) coordination polymers, [Co(HL)(bbe)] n (1) and [Co(HL)(bbop)] n (2) (H3L = 5-(carboxymethoxy)isophthalic acid, bbe = 1,2-bis(benzimidazol-2-yl)ethane, bbop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane), were synthesized and characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction and thermogravimetric analyses. Both complexes exhibit 1D chain structures, constructed from HL2− anions bridging metal ions. The 1D chains are further connected by hydrogen bonds and π–π stacking interactions to form the 3D supramolecular architectures. The cobalt centers display different coordination environments, with a tetrahedral geometry in 1 and a distorted tetragonal pyramid in 2. The DNA binding properties of both complexes were investigated by UV absorption spectroscopy. The electrochemical properties of both complexes were studied by cyclic voltammetry.

Synthesis and characterization of two cobalt(II) coordination polymers based on 5-tert-butyl isophthalic acid and bis(benzimidazole) ligands

Two cobalt(II) coordination polymers, namely [Co(bbdmbm)(tbi)·H2O]n (1) and [Co(bmb)1.5(tbi)]n (2), (bbdmbm = 1,1′-(1,4-butanediyl)bis(5,6-dimethylbenzimidazole), bmb = 1,4-bis(2-methylbenzimidazol-1-ylmethyl) benzene, H2tbi = 5-tert-butyl isophthalic acid), have been synthesized and characterized by physico-chemical and spectroscopic methods and also by single-crystal X-ray diffraction. Complex 1 features a 1D ladder-like chain and is further extended into a 3D supramolecular architecture via strong O–H···O hydrogen bonds. Complex 2 exhibits a 2D corrugated (4,4) network constructed with bmb and tbi ligands, which is further assembled into a 3D 3,4,4-connected supramolecular framework with 3,4,4T25 topology through weak C–H···O hydrogen-bonding interactions. The fluorescence properties and catalytic activities of both complexes for the degradation of Congo red in a Fenton-like process have been investigated.

Synthesis, crystal structure, and DNA-binding studies of different coordinate binuclear silver(i) complexes with benzimidazole open-chain ether ligands

Three new binuclear silver(i) complexes with bis-benzimidazole ligands have been developed and they bind to CT-DNA in an intercalation mode.