Microsensor Chip Integrated with Gold Nanoparticles‐Modified Ultramicroelectrode Array for Improved Electroanalytical Measurement of Copper Ions

This paper presents a microsensor chip integrated with a gold nanoparticles‐modified ultramicroelectrode array (UMEA) as the working electrode for the detection of copper ions in water. The microsensor chip was fabricated with Micro‐Electromechanical System technique. Gold nanoparticles were electrodeposited onto the surface of UMEA at a constant potential of ?0.3 V. The ratio d/R_b of interelectrode spacing (d) over the individual electrode’s radius (R_b) was investigated to improve the electrochemical performance. The UMEA with a d/R_b of 20 showed the best hemispherical diffusion mode, resulted in fast response time and high current response. The gold nanoparticles increased the active surface area of UMEA by not changing the geometries of UMEA, and the current response was increased further. Incorporating the optimized characteristic of UMEA and gold nanoparticles, the microsensor showed a good linear range from 0.5 to 200 µg L^?1 of copper ions in the acetate buffer solutions with the method of square wave stripping voltammetry. Compared with the gold nanoparticles‐modified disk electrode, the gold nanoparticles‐modified UMEA showed higher sensitivity (0.024 µA mm^?2 µg^?1 L) and lower limit of detection (0.2 µg L^?1). Water samples from river water and tap water were analyzed by the microsensor chip with recovery ranging from 100.7 % to 107.8 %.     

Simultaneous Detection of Copper,Lead and Zinc on Tin Film/Gold Nanoparticles/Gold Microelectrode by Square Wave Stripping Voltammetry

In this work, three heavy metals (Cu(II), Pb(II) and Zn(II)) in wide potential window were simultaneously detected on tin film/gold nanoparticles/gold microelectrode (Sn/GNPs/gold microelectrode) by the method of square wave stripping voltammetry. The Sn/GNPs/gold microelectrode was fabricated by in situ plating of a Sn film on a gold nanoparticles (GNPs) modified gold microelectrode. The influence of hydrogen overflow on stripping of Zn(II) on the gold microelectrode was reduced by modification of GNPs, which made the stripping potential of target metals shift positively. The interference of sulfhydryl groups was reduced and the selectivity of the microelectrode was improved due to the addition of Sn in the detection solution. After accumulation at ?1.4 V for 300 s in acetate buffer solution (0.1 mol L^?1, pH 4.5), the Sn/GNPs/gold microelectrode revealed a good linear behavior in the examined concentration ranges from 5 to 500 µg L^?1 for Cu(II) and Pb(II), and from 10 to 500 µg L^?1 for Zn(II), with a limit of detection of 2 µg L^?1 for Cu(II), 3 µg L^?1 for Pb(II) and 5 µg L^?1 for Zn(II) (S/N=3). When compared with a Sb/GNPs/gold microelectrode and a Bi/GNPs/gold microelectrode, the Sn/GNPs/gold microelectrode showed the best stripping performance to Cu(II), Pb(II) and Zn(II). As a new type of environment‐friendly electrode, the Sn/GNPs/gold microelectrode has potential applications for detection of heavy metals.     

Syntheses,Characterization and x-ray Structures of Gold(III) Complexes Obtained by Addition of Bases to Gold(III)(2-Pyridinecarboxaldehyde)

Reaction of potassium tetrachloroaurate(III), KAuCl₄, with 2-pyridinecarboxaldehyde (2CHO-py) have been examined in protic HX (X=OH, OMe, OEt, OCH₂CH₂CH₂, OCH₂CH₂CH₂CH₃, OCH₂CF₃) solvents. Compounds in which the pyridine ligand is N or N-O coordinated in a newly carbonyl hydrated or in semi- and acetal-forms, derived by addition of one or two hydroxylic molecules, have been isolated; these include dichloro[pyridine-2(α-hydroxymethanolato)]gold(III) (1), dichloro[pyridine-2(α-ethoxymethanolato)] gold(III) (2), dichloro[pyridine-2[α-(2,2,2-trifluoroethoxymethanolato)]gold(III) (3), trichloro(2-pyridinecarboxaldehyde dimethyl acetal)gold(III) (4), trichloro(2-pyridinecarboxaldehyde diethyl acetal)gold(III) (5), trichloro(2-pyridinecarboxaldehyde di-1-propyl acetal)gold(III) (6) and trichloro(2-pyridinecarboxaldehyde di-1-butyl acetal)gold(III) (7). The crystal and molecular structures of (2), (5) and (7) have been determined by X-ray methods. Compound (2) crystallizes in space group Pna2₁ with Z=4, a=7.8914(4), b=17.3660(4) and c=8.3873(5)Å; (5) crystallizes in space group P&1macr; with Z=2, a=7.7779(3), b=8.2878(2) and c=13.3202(6)Å, α=96.975(2), β=95.096(2), γ=115.027(2)°; (7) crystallizes in space group P2₁/a with Z=4, a=14.5438(12), b=8.9865(7) and c=15.0362(11)Å.     

Variation in coordinative property of two different N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL¹] · CH₃OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N₂O₂ tetradentate Schiff base ligand H ₂ L ¹ , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL²)₃] · (ClO₄)₃ · H₂O (2) was synthesised using an asymmetric N₂O₂ tetradentate Schiff base ligand HL ² on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N₂O₂ functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.     

Surface Plasmon Resonance Immunosensor for Anionic Surfactants Based on an Indirect Competitive Immunoreaction

Abstract

A highly sensitive surface plasmon resonance immunosensor for the determination of linear alkylbenzene sulfonate (LAS) was fabricated. The method is based on an indirect competitive reaction of an anti‐LAS antibody in a sample solution with LAS immobilized on a sensor chip and with LAS in the sample solution. A sensor chip immobilized with LAS was prepared by utilizing an electrostatic interaction between an LAS conjugate, LAS–horseradish peroxidase (LAS‐HRP), and a self‐assembled monolayer of 11‐amino‐1‐undecanethiol hydrochloride, which was preliminary prepared on a gold thin film of the sensor chip. The quantitative determination of LAS in the concentration range 10–1000 ppb was achieved by using the proposed immunosensor.     

A combined theoretical and thermal analysis study on the solid state linkage isomerization of Ni(II)-nitrite complexes with ethylenediamine derivatives*

Solid state stepwise nitro–nitrito linkage isomerization of trans-[dinitrobis(ethylenediamine)nickel(II)], [Ni(en)₂(NO₂)₂] (N,N-en), trans-[dinitrobis(N,N′-dimethylethylenediamine)nickel(II)], [Ni(N,N′-dmen)₂(NO₂)₂] (N,N-dmen), and trans-[dinitritobis(N,N-dimethylethylenediamine)nickel(II)], [Ni(N,N-dmen)₂(ONO)₂] (O,O-udmen) were investigated by performing non-isothermal differential scanning calorimetry (DSC) analyses and the thermodynamic and thermokinetic parameters of isomerization were determined using DSC curves. Both N,N-en and N,N-dmen DSC curves show an endothermic peak at elevated temperatures, attributed to dinitro-to-dinitrito linkage isomerization. Similar exothermic peaks were observed in the cooling cycle, assigned to the reverse dinitrito-to-dinitro isomerization. The O,O-udmen isomer is more stable than the corresponding dinitro one at ambient temperatures, but an exothermic dinitrito-to-dinitro isomerization occurs upon cooling down to ?70 °C and reverts endothermically to dinitrito isomer upon heating up to ambient temperature. The overlapping DSC peaks associated with stepwise linkage isomerization were resolved using nonlinear fitting method. The peak temperature and the enthalpy changes of linkage isomerization are inversely dependent on the steric hindrance provided by diamine ligands, which increases in the order udmen > dmen > en. The results showed that the steric factor of the co-ligands also influences the kinetic parameters of isomerization, so that more bulky ligand substituent leads to higher isomerization rate constants. A DFT and TD-DFT calculations have been carrid out on both dinitro complexes of this investigation .     

Synthesis,crystal structure,magnetic property,and nuclease activity of a binuclear iron(III) complex

A μ-oxo-di-μ-carboxylato-bridged iron(III) complex containing two tridentate nitrogen ligands, {[Fe₂(bpma)(bpea)(μ-CH₃COO)₂ μ-O)] · (ClO₄)₂ · 0.5CH₃OH} (1) (bpma = N, N-bis(2-pyridylmethyl)methyl-amine, bpea = N,N-bis(2-pyridylmethyl)ethylamine), has been synthesized and determined by X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/c with a = 10.9434(12) Å, b = 23.118(3) Å, c = 15.8721(18) Å, β = 92.736(2)° and Z = 4. In 1, each Fe(III) has a distorted octahedral geometry with a N₃O₃ donor set. The Fe(III) atoms are bridged by two carboxyl groups and one μ-oxo oxygen with Fe1–Fe2 separation of 3.064 Å. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of the high-spin Fe(III) atoms with J = ?121.0 cm^?1 and g = 2.04. The interaction with calf thymus DNA was investigated by UV absorption and fluorescent spectroscopy. Results show that the complex binds to ct-DNA with a moderate intercalative mode. The interaction between 1 and pBR322 DNA has also been investigated by submarine gel electrophoresis; the complex exhibits effective DNA cleavage activity in the absence of activating agents under similar physiological conditions.     

Colorimetric detection of cadmium in water using L-cysteine Functionalized gold–silver nanoparticles

Abstract

A new simple colorimetric assay was developed for the selective and sensitive detection of cadmium (II) in water samples using L-cysteine functionalized gold–silver nanoparticles. The gold–silver nanoparticles were synthesized by reducing HAuCl₄ and AgNO₃ in aqueous medium and were further functionalized with L-cysteine. The formation of homogeneous gold–silver nanoparticles was characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, particle size distribution, and ultraviolet–visible absorption methods. In the presence of cadmium (II), the aggregation of functionalized gold–silver nanoparticles caused by the interaction between cadmium (II) and L-cysteine resulted in a naked-eye visible color change of L-cysteine functionalized gold–silver nanoparticles from orange–yellow to green, which can be monitored by a simple ultraviolet–visible spectrophotometer. Under the optimal conditions, the absorbance ratio at 600–435?nm (A₆₀₀/A₄₃₅) was linear to the concentration of cadmium (II) from 0.4 to 38.6?μM, and the limit of detection of cadmium (II) was 44?nM. Interference measurements showed that the method exhibited good selectivity. The proposed method was successfully applied to the determination of cadmium (II) in environmental water samples. The results indicated that this simple, selective, and sensitive sensing system has good potential for practical applications.     

Zinc(II) complexes containing N′-aromatic group substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines: Synthesis,characterization, and polymerizations of methyl methacrylate and rac-lactide

A novel series of Zn(II) complexes [L_nZnCl₂] (L_n = L_A ? L_F) based on N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine bidentate ligands, N,N-bis((1H-pyrazol-1-yl)methyl)-3,5-dimethylaniline [L_A], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-dimethylaniline [L_B], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylaniline [L_C], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diisopropylaniline [L_D], N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromoaniline [L_E] and N,N-bis((1H-pyrazol-1-yl)methyl)benzhydrylamine [L_F], has been synthesized and characterized. X-ray structures of these Zn(II) complexes showed a distorted tetrahedral geometry. No interaction exists between the N_amine and the Zn(II) center in the [L_nZnCl₂] (L_n = L_A ? L_F) complexes, resulting in formation of an eight-membered chelate ring. [L_FZnCl₂] exhibited the highest catalytic activity (3.95 × 10⁴ g PMMA/mol·Zn·h) for the polymerization of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) at 60 °C and yielded high molecular weight (M_w) (11.0 × 10⁵ g/mol) of poly(methylmethacrylate) (PMMA). All the complexes resulted in syndiotactic enriched PMMA with high T_g (125–131 °C). The steric bulk of ligand architecture plays an influential role in controlling the catalytic activity and stereoregularity of the resultant PMMA. Further, alkyl derivatives [L_nZnMe₂] (L_n = L_A ? L_F) of synthesized Zn(II) complexes, generated in situ, showed moderate to high activities toward ring opening polymerization (ROP) of rac-lactide (rac-LA) and yielded heterotactic polylactide (PLA) with P_r up to 0.95 at ?50 °C. The activity and stereoselectivity toward ROP of rac-LA by these dimethyl Zn(II) complexes should be considered as a combined effect of steric hindrance and electronic density around the metal center.     

Prototypical Nonelectrochemical Method for Surface Regeneration of an Integrated Electrode in a PDMS Microfluidic Chip

Abstract

A prototypical method for surface regeneration of an integrated electrode in a microfluidic chip is demonstrated. A platinum wire as working electrode was mounted in a polydimethylsiloxane chip vertical to the chip through the channel. The regeneration of the electrode was easily achieved by drawing the platinum wire out for 5 mm, because the area exposed to the channel or the stream would be altered. With continuous motion, the wire electrode can maintain a fresh surface just like a dropping mercury electrode. The current–time curve and open circuit potential (OCP) of dopamine solution show the performance of this prototypical system.     

Metal derivatives of thiosemicarbazones: crystal and molecular structures of mono- and di-nuclear copper(I) complexes with N1-substituted thiosemicarbazones

The reactions of copper(II) chloride with a series of N¹-substituted thiosemicarbazones, {R¹(H)C²=N³–N²(H)–C¹(=S)–N¹HMe, R¹ = furan, Hftsc-N-Me; thiophene, Httsc-N-Me; phenyl, Hbtsc-N-Me} in 1 : 2 molar ratio yield copper(I) complexes : sulfur-bridged dinuclear complexes, [Cu₂Cl₂(μ-S-Hftsc-N-Me)₂(η¹-S-Hftsc-N-Me)₂] (1), [Cu₂Cl₂(μ-S-Httsc-N-Me)₂(η¹-S-Httsc-N-Me)₂] (2), and a mononuclear complex [CuCl(η¹-S–Hbtsc-N-Me)₂] (3). Complexes 1–3 have been characterized by elemental analysis (C, H, N), spectroscopy (IR, ¹H NMR) and X-ray crystallography. The Cu(μ-S)₂Cu cores in 1 and 2 form parallelograms with unequal bond distances {Cu–S, 2.2831(3), 2.5955(4) Å (1); 2.2641(9), 2.8006(10) Å (2)}. Bond angles at sulfur and copper are, Cu–S–Cu, S–Cu–S, 69.86(11), 110.12(17)° (1); 75.84(3), 104.16(3)° (2), respectively. The Cu ··· Cu separations are 2.806 Å (1) and 3.141 Å (2) with each copper center a distorted tetrahedron (96.67–119.28°). Bond parameters of 3, Cu–S, 2.227(3), 2.224(3) Å, and 118.97–121.11° are different.     

Electrochemical DNA sensing based on gold nanoparticle amplification

A hybridization signal-amplified method based on a gold nanoparticle-supported DNA sequence for electrochemical DNA sensing has been investigated by cyclic voltammetry, differential-pulse voltammetry, and atomic-force microscopy (AFM). Quantitative analysis showed that the peak current increment (Ip) is linearly dependant on the concentration of the gold nanoparticle-supported DNA sequence Au2 over the range 0.51–8.58 pmol L^–1. AFM results indicated that the extent of surface hybridization was dependent on the concentration of the gold-nanoparticle-supported DNA sequence. Moreover, a new pair of peaks, which might arise from the special configuration of the gold-nanoparticle-supported DNA sequence, appeared in the cyclic voltammogram after hybridization. Although quite sensitive, this DNA sensing surface was not easily regenerated, so this kind of amplified method was suitable for disposable DNA sensors and chip-based gene diagnosis sensors.     

Acid Dissociation Behaviour and Complexation with Nickel(II), Copper(II) and Zinc(II) for Two Conformational Isomers of Dicyclohexylcyclam

Abstract

Acid dissociation constants for two conformational isomers of dicyclohexylcyclam, cis-anti-cis, (P) and cis-syn-cis, (N) have been determined at 25, 35 and 40°C, and thermodynamic data are estimated. It was found that (N) shows very different behaviour from (P). Stability constants of (P) and (N) toward Ni(II), Cu(II) and Zn(II) have been determined by pH-titration at 25°C by using a ligand exchange reaction. It is found that the (P) complex is more stable for Ni(II) and the (N) complex is more stable for Cu(II). Contributions of the cyclohexyl group to the macrocyclic effect (ME) have been also estimated by considering basicity corrections. It is found that substitution of the cyclohexyl group in cyclam increases ME only for the Ni(II) complex of (P).     

Double‐crosslinked reversible redox‐responsive hydrogels based on disulfide–thiol interchange

We present novel redox‐responsive hydrogels based on poly(N‐isopropylacrylamide) or poly(acrylamide), consisting of a reversible disulfide crosslinking agent N,N′‐bis(acryloyl)cystamine and a permanent crosslinking agent N,N′‐methylenebisacrylamide for microfluidic applications. The mechanism of swelling/deswelling behavior starts with the cleavage and reformation of disulfide bonds, leading to a change of crosslinking density and crosslinking points. Raman and ultraviolet‐visible spectroscopy confirm that conversion efficiency of thiol–disulfide interchange up to 99%. Rheological analysis reveals that the E modulus of hydrogel is dependent on the crosslinking density and can be repeatedly manipulated between high‐ and low‐stiffness states over at least 5 cycles without significant decrease. Kinetic studies showed that the mechanical strength of the gels changes as the redox reaction proceeds. This process is much faster than the autonomous diffusion in the hydrogel. Moreover, cooperative diffusion coefficient (D_coop) indicates that the swelling process of the hydrogel is affected by the reduction reaction. Finally, this reversibly switchable redox behavior of bulky hydrogel could be proven in microstructured hydrogel dots through short‐term photopatterning process. These hydrogel dots on glass substrates also showed the desired short response time on cyclic swelling and shrinking processes known from downsized hydrogel shapes. Such stimuli‐responsive hydrogels with redox‐sensitive crosslinkers open a new pathway in exchanging analytes for sensing and separating in microfluidics applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2590–2601     

Enhanced surface plasmon resonance by Au nanoparticles immobilized on a dielectric SiO2 layer on a gold surface

This paper introduces strategies for enhancement of a surface plasmon resonance (SPR) signal by adopting colloidal gold nanoparticles (AuNPs) and a SiO₂ layer on a gold surface. AuNPs on SiO₂ on a gold surface were compared with an unmodified gold surface and a SiO₂ layer on a gold surface with no AuNPs attached. The modified surfaces showed significant changes in SPR signal when biomolecules were attached to the surface as compared with an unmodified gold surface. The detection limit of AuNPs immobilized on a SPR chip was 0.1 ng mL⁻¹ for the prostate-specific antigen (PSA), a cancer marker, as measured with a spectrophotometer. Considering that the conventional ELISA method can detect ∼10 ng mL⁻¹ of PSA, the strategy described here is much more sensitive (∼100 fold). The enhanced shift of the absorption curve resulted from the coupling of the surface and particle plasmons by the SiO₂ layer and the AuNPs on the gold surface.     

Synthesis and properties of poly(amide–imide)s containing a N-methylcarbazole group

A new dicarboxylic acid monomer containing the N-methylcarbazole and imide structures, 3,6-bis(trimellitimido)-N-methylcarbazole (I), was prepared from the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anhydride. The diamine c was synthesized in three steps starting from the methylation of carbazole, followed by nitration and catalytic hydrazine reduction. A series of N-methylcarbazole-containing poly(amide–imide)s were synthesized by direct polycondensation from the diimide–diacid I with various aromatic diamines. These poly(amide–imide)s had inherent viscosities of 0.66–1.47 dl/g and were readily soluble in a variety of organic solvents, including N-methyl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions, and these films exhibited excellent mechanical strength. The glass-transition temperatures of these poly(amide–imide)s were in the range 317–362 °C. All the poly (amide–imide) did not degrade noticeably below 480 °C in nitrogen, and the 10% weight loss temperatures and char yields at 800 °C were above 520 °C and 60% in nitrogen, respectively, indicating high thermal stability. Received: 8 February 2000/Accepted: 23 March 2000     

Synthesis,structure and antimicrobial study of two new copper(II) complexes derived from N-(3-aminopropyl) benzylamine ligand (apba) and N-salicylidene-apba

Two new copper(II) complexes were synthesized by reaction of N-(3-aminopropyl)benzylamine (L1: apba, for complex 1) and N-salicylidene-apba (L2: for complex 2) with Cu²⁺. Crystals of complex 1 were orthorhombic, space group pccn, with a?=?15.2149(10), b?=?25.0071(16), c?=?7.6280(5)?Å and α?=?β?=?γ?=?90°. Complex 2 crystals were monoclinic, space group P2₁/c, with a?=?8.688(6), b?=?12.812(9), c?=?16.022(11)?Å and β?=?99.241(10)°. Structures of the two complexes were centro-symmetric and both Cu(II) atoms were four coordinate with a distorted square-planar geometry. The toxicity of the complexes was evaluated by testing antimicrobial activity against bacterial strands.     

Synthesis,structure, cytotoxic activities,and DNA-binding of 1-D copper(II) and zinc(II) coordination polymers

Two 1-D coordination polymers have been synthesized and identified as [Zn(ox)(en)] _n (H₂O)_{2 n} (1) and [Cu₂(dmeo)(N₃)₂] _n (2), where en represents diaminoethane, ox and dmeo stand for dianions of oxalic acid and N,N′-bis[2-(dimethylamino)ethyl]oxamide, respectively. Polymer 1 was characterized by elemental analysis, molar conductance measurement, IR and electronic spectra, and single-crystal X-ray diffraction. Polymer 1 consists of 1-D chains bridged by oxalate. The Zn^II can be described as a distorted octahedral environment and the Zn^II···Zn^II separation through the μ-oxalato-bridge is 5.5420(9)?Å. Hydrogen bonds assemble the coordination polymers to a 3-D supermolecular structure. The crystal structure of 2 has been reported previously. However, the bioactivities were not studied. The DNA-binding properties and cytotoxic activities of the two coordination polymers are investigated. The results suggest that the two polymers interact with HS-DNA in groove binding with binding affinity following the order of 1?>?2, which is consistent with their anticancer activities.     

Synthesis and characterization of organo-soluble poly(amide-imide)s based on 1,2-bis[4-(trimellitimido)phenoxy]ethane and aromatic diamines

<正>New organo-soluble poly(amide-imide)s(PAIs) 8a-8f were prepared from newly synthesized 1,2-bis[4,4'-(trimellitimido) phenoxy]ethane 6 via direct polycondensation with various aromatic diamines.The diacid 6 was synthesized by the condensation reaction of 12-bis[4-atninophenoxy]ethane 4 with trimellitic anhydride 5 in acetic acid.All polymers were obtained in quantitative high yields with inherent viscosities of 0.48-0.61 dL/g.All of these polymers were highly soluble in organic solvents such as,N-methyl-2-pyrrolidone(NMP),dimethylformamide(DMF),N,N'-dimethylacetamide (DMAc) and dimethylsulfoxide(DMSO) at room temperature and were fully characterized by means of NMR spectroscopy, FTIR spectroscopy,elemental analyses,inherent viscosity,solubility test,specific rotation,differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA).     

Synthesis,crystal structure,in vitro anticancer and in vivo acute oral toxicity studies of tetramethylene linked bis-benzimidazolium salts and their respective dinuclear Ag(I)–NHC complexes

The proligands of the series tetramethylenebis(N-n-alkylbenzimidazolium bromide) (where n = 3–10) (1–8) as N-heterocyclic carbene (NHC) precursors have been prepared by reacting the initially synthesized N-n-alkyl benzimidazole with 1,4-dibromobutane in 2 : 1 M ratio. A reaction of Ag₂O with 1–8 resulted in the formation of Ag(I) complexes tetramethylenebis{(N-n-alkylylbenzimidazol-2-ylidene)silver(I)hexafluorophosphate} (9–16), respectively. All the synthesized compounds were characterized by FT-IR, ¹H NMR, ¹³C NMR, atomic absorption and elemental analysis. Single-crystal X-ray diffraction study on tetramethylenebis{(N-n-octylbenzimidazol-2-ylidene)silver(I)hexafluorophosphate} (14) has revealed that the complex exists as a dinuclear compound. All compounds were assessed for their antiproliferation test on human colorectal cancer cell line (HCT 116). Interestingly, increasing the n-alkyl chain length from n = 3 to 10 of the proligands and their respective complexes showed trends in increased cytotoxicity against human colon cancer cell line. Cytotoxicity data showed that tetramethylene linked bis-benzimidazolium salts and their respective dinuclear Ag(I)–NHC complexes can be useful therapeutic agents against colon cancer.