Hydroxamate Complexes Research Articles

Synthesis, structural interpretation, DFT, molecular docking, antimicrobial assessment and cytotoxic profiling of a cadmium(II) hydroxamate complex: in vitro and in silico investigations

A Cd(II) complex of composition Cd(C11H9CONHO)2 has been synthesized by treating CdCl2 (anhydrous) with potassium 1-naphthaleneacetohydroxamate (C11H9CONHOK) (KHL) in 1:2 molar ratio in MeOH. Various physicochemical studies including elemental analysis, molar conductivity, FTIR, UV-visible,1H and 13C NMR spectroscopic techniques were employed to interpret the structure of the complex. O,O-Coordination has been proposed through the carbonyl and hydroxamic oxygen atoms and a distorted tetrahedral geometry around cadmium is supported by physicochemical and computational studies. Density Functional Theory studies have shown the stability of the complex and predict various structural parameters (bond lengths and angles). Chemical reactivity descriptors and Mulliken charge analysis were also calculated and analyzed. Molecular docking studies were conducted to analyze the interaction of the ligand and complex with two proteins, Escherichia coli Tem1 beta-lactamase (PDB ID = 1BTL) and Alternaria alternata major allergen alt a 1 (PDB ID = 4AUD). Further, the ligand and complex were tested in vitro for their antimicrobial activity against selected microbes such as S. aureus, S. typhi, E. coli, S. flexneri, Rhizoctonia solani, Alternaria alternata, and Fusarium Sambucinum. The complex was more effective against A. alternata, showing inhibition specifically against S. typhi and E. coli. In vitro cytotoxicity studies were conducted on Rhabdomyosarcoma RD cancer cell lines. The results revealed a reduction in cell viability, correlating with increasing concentrations of the compounds, thereby indicating efficient cytotoxic activity.

Synthesis, Spectroscopic, and DFT Studies of Vanadium (III) Hydroxamate Complex with Potential Biological Applications

A new vanadium (III) hydroxamate complex of composition V(4- NO2C6H4CH=CHCONHO)3 has been synthesized by reaction of VCl3 with potassium salt of 4-nitrocinnamohydroxamate (4-NO2C6H4CH=CHCONHO) in 1:3 molar ratio in dry methanol solvent. The newly synthesized complex is characterized by elemental analysis, molar conductivity, magnetic moment measurements and IR, UV-Vis spectral studies and mass spectrometry. DFT calculations were carried out by using Orca 4.2.1 program and the negative values of the energies of EHOMO and ELUMO for the V(III) complex confirm its stability. A distorted-octahedral geometry around vanadium center has been suggested for complex based upon physicochemical, spectroscopic and DFT studies, involving bonding through hydroxylamine and carbonyl oxygens (O O coordination). The cyclic voltammogram of the complex shows single anodic and cathodic peak. The TGA/DTA curve indicates the single step decomposion of complex. The biological potential of the ligand and complex have been tested by in vitro antimicrobial studies and cytotoxicity assay. Antimicrobial activity of complex has been found increased as compare to precursor and ligand. The results of cytotoxicity reveal the complex less toxic as compared to standard drug simvastatin.

Highly selective organo-gallium hydroxamate mediated inhibition of antibiotic resistant Klebsiella pneumoniae.

Five complexes of gallium derived from hydroxamic acids have been synthesised, characterised, and their anti-bacterial activity and mammalian cell toxicity established. These are three metal-organic complexes; [Ga(BPHA)3] 1, [Ga(BHA-H)3] 2, [Ga(SHA-H2)(SHA-H)3] 3, and two heteroleptic organometallic complexes [GaMe2(BPHA)] 4, and [GaMe(BHA-H)2] 5, along with the iron complex [Fe(BPHA)3] 6 (BPHA-H = N-benzoyl-N-phenylhydroxamic acid, BHA-H2 = phenylhydroxamic acid, and SHA-H3 = salicylhydroxamic acid). Solid-state structures of 1, 4-6 were identified by single-crystal X-ray crystallography. Complexes 1 and 6 adopt an octahedral geometry at the metal centre, while the organometallic complexes 4 and 5 adopt, respectively, tetrahedral and trigonal bipyramidal geometry. The solution and solid-state chemistry of complex 3 was found to differ: the solution state is composed of an equilibrium mixture of the bis-complexed hydroximate-hydroxamate species and the homoleptic tris-hydroxamate species, with the solid state preferring the bis-complexed hydroximate-hydroxamate composition. The methyl gallium complexes 4 and 5 differed in their preferred composition with 4 forming the expected dimethyl hydroxamate complex while 5 stabilises as the methyl bis-hydroxamate complex. Complexes were tested for the anti-microbial activity against a series of Gram-positive and Gram-negative bacteria, with an emphasis on the Gram-negative Klebsiella pneumoniae. While the metal-organic complexes 1, 2, 3 and 6 showed little to no activity towards either the bacteria or mammalian cells, the alkyl gallium complexes 4 and 5 were found to have exceptional activity toward K. pneumoniae in RPMI-HS media with MIC values of 78 nM. Interestingly, [GaMe2(OH)] also showed significant activity with an MIC of 156 nM.

Antibacterial and ct-DNA binding studies of new synthesized ruthenium (III) hydroxamate complexes: Design, synthesis, DFT calculations and in-vitro study

Ruthenium (III) complexes (1–5) with general composition [Ru(L1–4)3] and [Ru(HL5)3Cl3] where L1 = benzohydroximato (1), L2 = salicylhydroximato (2), L3 = acetohydroximato (3), L4 = hydroxyureato (4), HL 5 = N‑hydroxy-N-phenylbenzamide (5) were synthesized by reacting RuCl3·3H2O with respective hydroxamic acids in 1:3 molar ratio . The complexes were characterized using various techniques including ruthenium metal analysis, elemental analysis, UV–Vis, FT-IR, NMR (1H and 13C), and mass spectrometry. Antibacterial activity of the complexes was evaluated using the agar well diffusion method against ten pathogenic strains. The complexes showed significant inhibition zones and were more active than their corresponding ligands. DNA binding studies indicated intercalative binding mode, with hypochromism and red shift observed. Computational and structural parameters were determined using Frontier Molecular Orbital (FMO) energies and Density Functional Theory (DFT) calculations. The complexes demonstrated favorable molecular geometry, chemical reactivity, and biological activity.

Insights into the adsorption mechanism of benzohydroxamic acid in the flotation of rhodochrosite with Pb2+ activation

The adsorption mechanism of benzohydroxamic acid (BHA) on rhodochrosite surfaces under Pb2+ activation was systematically studied through a series of experiments. Comparing to the results of only BHA treatment, Pb2+ ions raised the adsorption amount of BHA and the floatability of rhodochrosite, especially at pH 8.0–9.0. It was proven that Pb(OH)+ was deemed as the critical species to adsorb onto rhodochrosite surfaces in the form of lead-containing complexes. Afterwards, rhodochrosite surfaces became much more activated for BHA adsorption. BHA collector reacted with adsorbed-Pb and Mn species of rhodochrosite surfaces, and the charged hydroxamic acid also adsorbed onto rhodochrosite surfaces through electrostatic attraction and co-adsorption. Besides, lead hydroxamate complexes generated in suspension had excellent adhesions on rhodochroganite surfaces. It was apparent that the BHA adsorption was strengthened under the activation of Pb2+ ions. BHA collector matching with Pb2+ ions had great potentials to improve the flotation recovery of rhodochrosite.

Synthesis, characterization and in vitro antibacterial activity of di- and tri n-butyltin(IV) complexes of 3-amino-4 -chloridobenzohydroxamic acid

New di-and tri- n-butyl tin(IV) hydroxamate complexes of composition [n-Bu2Sn(C6H3(3-NH2)(4-Cl)CONHO)2](I) and [n-Bu3Sn(C6H3(3-NH2)(4-Cl)CONHO)] (II) have been synthesized by the reactions of n-Bu2SnCl2 and n-Bu3SnCl with potassium 3-amino-4-chlorido benzohydroxamate(KHL) in predetermined metal:ligand 1:2 and 1:1 molar ratios respectively in MeOH+THF solvent medium and characterized by physiochemical, spectroscopic (IR,1 H and 13 C NMR) studies and mass spectrometry. The bidentate nature of hydroxamate ligand involving bonding through carbonyl and hydroxamic oxygen atoms (O,O coordination) has been inferred from IR spectra. The distorted octahedral and trigonal bipyramidal geometry around tin for (I) and (II) respectively have tentatively been proposed. The electrochemical behavior of complexes studied by cyclic voltammetric technique has shown two electron tin metal centered reductions. The in vitro antibacterial activity of (I) and (II) assayed against pathogenic gram -ve bacteria E.coli , P.aeruginosa; gram +ve bacteria S.aureus, B.cereus by MIC method has revealed these to be promising antibacterial agents relative to parent ligand.

Antidiabetic Potential of Ruthenium(III) Hydroxamate Complexes: Spectrophotometric Investigations

BACKGROUND: The potential antidiabetic and antioxidant properties of four ruthenium(III) hydroxamate complexes [RuCl(H2O)(LI-III)2] (1-3) and [RuCl3(H2O)(HLIV)2] (4) were investigated on α-cell enzymes (α-amylase and α-glucosidase). METHOD: In the instance of -amylase inhibition investigations, the antidiabetic studies of the complexes revealed that they are more active than even the Acarbose as standard, with complex 4 having an IC50 value of 52.31 g/ml. For α-glucosidase inhibition, complex 4 was observed to be the best inhibitor with a remarkable 0.35g/ml IC50 value, which may be attributed to the size and superior lipophilicity of this complex, enabling it to interact with the biological system more effectively than complexes 1-3.The complexes with the best IC50 values were studied further for enzyme kinetics. Molecular docking studies were performed as well to investigate the interactions between the synthesized complexes and target enzymes viz., α glucosidase and α-amylase. RESULT: The obtained in-vitro results have also been supported by the results of the in-silico docking studies. Furthermore, the antiradical activity of Ru(III) complexes was assessed for its effectiveness in reducing oxidative stress. CONCLUSION: All the complexes (except complex 3) exhibited remarkable antiradical activity.

Decreased Serum Cholinesterase Activity- A Reliable Diagnostic Aid for Tuberculosis

Introduction: Siderophore, the low molecular weight ferric iron chelator, is secreted extracellularly by Mycobacterium tuberculosis, an obligate aerobe. The pathogenic mycobacteria need iron as co-factor for the extracellularly secreted enzyme Superoxide Dismutase (SOD) for its pathogenicity as well as it requires iron for its metabolic functions like reduction of oxygen for synthesis of Adenosine Triphosphate (ATP), etc. The termination of impulse conduction is endorsed by the rapid hydrolysis of Acetylcholine (ACh) by Acetylcholinesterase (AChE) in the central as well as peripheral nervous system (cholinergic pathway). The inhibitors to Cholinesterase (ChE) might lead to accumulation of ACh, hyper stimulation of nicotinic and muscarinic receptors and also disruption of neurotransmission. Possibility of an inhibitor substance for AChE in Tuberculosis (TB) patients interestingly correlates with the symptom of night sweating in those subjects. Aim: To assay the level of serum ChE in normal control, lung disease control and tubercular subjects;circumvent the serum ChE level as a diagnostic potential in TB at an early stage. Materials and Methods: The study was conducted on total 124 subjects, and were divided into three groups: Group 1: normal control (n=31), Group 2: lung disease control (n=31) and Group 3: patients suffering from TB {3A: pulmonary TB (n=31) and 3B: extrapulmonary TB (n=31)}. Serum ChE activity for all the subjects were measured according to the method of Hestrin S. Serum ChE level was assayed for group 3 subjects after additional one month’s anti-TB drug treatment and also for group 2 subjects after one month with usual treatment. The level of significance was assessed using Student’s t-test. Results: There was a significant inhibition of serum ChE activity in both pulmonary and extrapulmonary TB patients in comparison to that of in normal control as well as lung disease control subjects (p<0.01). With the anti-tubercular drug therapy for one month, there was significant recovery in the serum ChE activity in pulmonary as well as extrapulmonary tubercular subjects (p<0.01). Conclusion: It appears that the high level of hydroxamate type of siderophores (secreted by Mycobacterium tuberculosis for acquiring iron) might form ACh ferric hydroxamate complex binding more strongly with serum ChE resulting in inhibition of serum ChE activity in tubercular subjects. With anti-tubercular drug therapy, there was decrease in serum ACh ferric hydroxamate complex level resulting in recovery of serum ChE activity.

Comment on "Investigation of Zr(iv) and 89Zr(iv) complexation with hydroxamates: progress towards designing a better chelator than desferrioxamine B for immuno-PET imaging" by F. Guérard, Y.-S. Lee, R. Tripier, L. P. Szajek, J. R. Deschamps and M. W. Brechbiel, Chem. Commun., 2013, 49, 1002.

An alternative analysis of the complexes formed by Zr(iv) with acetohydroxamate shows that, in comparison with the results reported in the title article, a more complicated complexation model is found, the stability constants of the common complexes are considerably different and complexation of Zr(iv) does not show any unusual behaviour.

Spot test exploiting smartphone-based digital images for determination of biodiesel in diesel blends

A simple, inexpensive, and fast colorimetric spot test is proposed for quantification of biodiesel in diesel blends. The procedure was based on formation of a violet complex between Fe(III) and the hydroxamate ion generated by the reaction of the alkyl esters characteristic of biodiesel with hydroxylamine. The analytical measurements were based on digital images acquired using a smartphone camera and converted to RGB values using a free application software (PhotoMetrix® 1.6). Values of the G channel corresponding to the intensities of the reflected radiation were taken as analytical parameter because of the complementarity with the absorption spectrum of the Fe(III)/hydroxamate complex. The effects of the reagents concentrations were evaluated by a Box-Bhenken experimental design and the optimized condition was 0.20 mol L−1 hydroxylamine, 0.30 mol L−1 NaOH, and 5.0 mmol L−1 Fe2(SO4)3. A linear response range was achieved from 3.0 to 30.0% (v/v) of biodiesel, described by equation G = 59.4 + 1.72 C (r = 0.999). The coefficient of variation and the limit of detection (99.7% confidence level) were estimated at 0.9% (n = 10) and 1.0% (v/v) of biodiesel, respectively. The proposed procedure consumed only 10 µL of sample, 830 μg NH2OH.HCl, and 110 μg Fe(III) and generated ca. 1.0 mL of residue per determination. The results for determination of biodiesel in diesel blends agreed with those obtained by the official method EN14078 at the 95% confidence level. The proposed procedure also allows monitoring formation of fatty acid methyl esters during the transesterification reaction.

Nitrosubstituted hydroxamate ligands in new triphenyltin(IV) complexes as prospective antimicrobial agents

New triphenyltin(IV) hydroxamate complexes, [Ph3Sn(4-NO2CnH)] and [Ph3Sn(4-NO2BzH)] have been synthesized by the reactions of Ph3SnCl with potassium 4-nitrocinnamo hydroxamate [4-NO2C6H4CHCHCONHOK] (KHL1) and potassium 4-nitro benzohydroxamate [4-NO2C6H4CONHOK] (KHL2). The complexes were synthesized in 1:1 molar ratio in MeOH + C6H6 and characterized by physicochemical and IR, 1H NMR, and mass spectrometry. The bidentate hydroxamate involving bonding through carbonyl and hydroxamic oxygen (O, O coordination) has been inferred from IR spectra. The electrochemical behavior of complexes has been analyzed. Quasi-irreversible two electron metal-centered cathodic process of type SnIV/SnII redox couple was indicated by cyclic voltammetric technique. The thermal behavior of 1 and 2 studied by TGA has shown continuous decomposition to yield Sn + 0.5SnO2 and SnO2 as final residues. The in vitro antimicrobial activity assays of 1 and 2 against pathogenic Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Salmonella typhi and Pseudomonas aeruginosa), and fungi (Aspergillus fumigatus and Alternaria alternata) were done by MIC method. The complexes have exhibited appreciable antimicrobial activity relative to the respective standard Gentamycin and Nystatin drugs.

Neptunium(iv)-hydroxamate complexes: their speciation, and kinetics and mechanism of hydrolysis.

Simple hydroxamic acids such as acteohydroxamic acid (AHA) have been identified as suitable reagents for the control of Pu and Np in advanced separation processes for nuclear fuel reprocessing such as the Advanced PUREX or UREX based recycle processes, due to their ability to strip the tetravalent form of Pu and Np from tri-butyl phosphate into nitric acid. However, both free and metal bound hydroxamates are known to undergo acid catalysed hydrolysis at low pH, the kinetics of which must be characterised before implementation of PUREX/UREX based reprocessing flowsheets. In support of this implementation, a comprehensive thermodynamic and kinetic model that describes both the complex speciation and hydrolysis of AHA in the presence of Np(iv) has been developed. The model has two unique features: (i) in the case of the hydrolysis reaction kinetics, the model includes the hydrolysis of not only free AHA but also both the mono- and bishydroxamato-Np(iv) complexes; (ii) for the associated speciation calculations, the model explicitly includes the ionic strength dependence of not only the mono- and bishydroxamato-Np(iv) complexes but also the mono- and bisnitrato neptunium(iv) and monohydroxoneptunium(iv) complexes. For the latter three species, respective SIT coefficients of Δε1,NO3 = -0.13 ± 0.03 kg mol-1, , Δε2,NO3 = -0.37 ± 0.13 kg mol-1, Δε1,OH = -0.36 kg mol-1 and log10 K01,OH = -1.23 were also determined. Using experimental data from a series of kinetic studies on the Np(iv)-AHA system, this model has been used to determine the rate constants for hydrolysis of mono- and bis-acetohydroxamatoneptunium(iv) at 25 °C for the first time. These were found to be 3.5 × 10-5 ± 2.5 × 10-5 dm3 mol-1 s-1 and 1.9 × 10-3 ± 1.3 × 10-3 dm3 mol-1 s-1, respectively. Comparison of these values with the rate constants for hydrolysis of free AHA indicates that complexation of AHA with Np(iv) increases the rate of hydroxamate hydrolysis - an observation that we attribute to the electron withdrawing effect of the metal centre within the Np(iv)-AHA complex increasing the susceptibility of the AHA carbonyl carbon to nucleophilic attack, the accepted first step in its mechanism of hydrolysis.

Simple zinc complex to model substrate binding to zinc enzymes

Abstract To model substrate binding to zinc containing enzymes, Zn(Tp∗)Cl (Tp∗ = tris(3,5-dimethyl-1-pyrazolyl)borate) was investigated as an inexpensive and easily prepared target. Both acetyl hydroxamic acid and acetic acid, common zinc binding moieties, were found to bind zinc in our model system and the resulting complexes were fully characterized. The hydroxamate complex was found to be both thermodynamically and kinetically favored in comparison to the acetate complex, in keeping with previous models, demonstrating the utility of this system in enzymatic mimicry.

Behaviour of ilmenite as a gangue mineral in the benzohydroxamic flotation of a complex pyrochlore-bearing ore

One challenge identified in the flotation of niobium bearing minerals with hydroxamates is the recovery of gangue minerals which can result in concentrate grade dilution. Micro-flotation of single and mixed minerals and bench scale flotation tests on a low-grade complex pyrochlore-bearing ore were conducted to assess the flotation behavior of ilmenite as a gangue mineral in the flotation of pyrochlore using benzohydroxamic acid (BHA) as a collector and sodium hexametaphosphate (SHMP) as a dispersant/depressant. In micro-flotation, high dosages of BHA resulted in high pyrochlore recovery and low ilmenite recovery at pH 8. It was observed that the order of addition of SHMP in relation to BHA had a strong effect on pyrochlore recovery, with high recovery maintained only when SHMP was added after BHA. When ilmenite and pyrochlore were floated in the same system, it was found that reagent addition order played an important role in selective flotation of pyrochlore. Flotation of pyrochlore was more selective over ilmenite when SHMP was added before BHA, similar to a cleaner flotation stage in real-ore flotation. Contrary to micro-flotation results titanium recovery was high (more than 60% TiO2 recovery in most cases) under similar pulp conditions in bench scale flotation, an indication that to some extent titanium minerals were recovered by a mechanism other than genuine flotation. Similarly, in mixed mineral micro-flotation, the recovery of ilmenite increased in the presence of pyrochlore. Two possible scenarios, one physical and the other chemical in nature, have been proposed to explain this observed phenomenon. First, it is possible that moderately floatable titanium mineral particles were recovered in the froth by association with highly floatable pyrochlore, particularly at starvation levels of a dispersant (SHMP) through the hydraulic entrainment of fines. The second possibility is that titanium minerals experienced inadvertent activation in multi-mineral systems, perhaps with metal-hydroxamates as the activating species, forming hydroxamate complexes involving ferric and/or niobium species. This research area is under further investigation.

Azahelicenes from the Oxidative Photocyclization of Boron Hydroxamate Complexes.

Aromatic hydroxamic acids (Ar-CO-NOH-Ar') were used as bidentate chelating ligands to generate the corresponding boron hydroxamate complexes, which were subsequently transformed into nitrogen-containing helicenes (azahelicenes) using an oxidative photocyclization method that is frequently used for stilbene-type (Ar-CH=CH-Ar') precursors of carbohelicenes. The nitrogen atom of the hydroxamate linker was thus directly embedded into the helicene core without using nitrogen-containing aromatic rings in the stilbene-type precursors. In a batch photoreaction, aza[4]helicenes were readily and efficiently prepared, but aza[6]helicenes underwent severe decomposition upon irradiation. Alternatively, a continuous flow photoreactor was employed to furnish an amide-type aza[6]helicene.

High throughput, colorimetric screening of microbial ester biosynthesis reveals high ethyl acetate production from Kluyveromyces marxianus on C5, C6, and C12 carbon sources.

Advances in genome and metabolic pathway engineering have enabled large combinatorial libraries of mutant microbial hosts for chemical biosynthesis. Despite these advances, strain development is often limited by the lack of high throughput functional assays for effective library screening. Recent synthetic biology efforts have engineered microbes that synthesize acetyl and acyl esters and many yeasts naturally produce esters to significant titers. Short and medium chain volatile esters have value as fragrance and flavor compounds, while long chain acyl esters are potential replacements for diesel fuel. Here, we developed a biotechnology method for the rapid screening of microbial ester biosynthesis. Using a colorimetric reaction scheme, esters extracted from fermentation broth were quantitatively converted to a ferric hydroxamate complex with strong absorbance at 520 nm. The assay was validated for ethyl acetate, ethyl butyrate, isoamyl acetate, ethyl hexanoate, and ethyl octanoate, and achieved a z-factor of 0.77. Screening of ethyl acetate production from a combinatorial library of four Kluyveromyces marxianus strains on seven carbon sources revealed ethyl acetate biosynthesis from C5, C6, and C12 sugars. This newly adapted method rapidly identified novel properties of K. marxianus metabolism and promises to advance high throughput microbial strain engineering for ester biosynthesis.

Covalency-Driven Dimerization of Plutonium(IV) in a Hydroxamate Complex.

The reaction of formohydroxamic acid [NH(OH)CHO, FHA] with Pu(III) should result in stabilization of the trivalent oxidation state. However, slow oxidation to Pu(IV) occurs, which leads to formation of the dimeric plutonium(IV) formohydroxamate complex Pu2(FHA)8. In addition to being reductants, hydroxamates are also strong π-donor ligands. Here we show that formation of the Pu2(FHA)8 dimer occurs via covalency between the 5f orbitals on plutonium and the π* orbitals of FHA(-) anions, which gives rise to a broad and intense ligand-to-metal charge-transfer feature. Time-dependent density functional theory calculations corroborate this assignment.

Molecular titanium-hydroxamate complexes as models for TiO2 surface binding.

Hydroxamate binding modes and protonation states have yet to be conclusively determined. Molecular titanium(iv) phenylhydroxamate complexes were synthesized as structural and spectroscopic models, and compared to functionalized TiO2 nanoparticles. In a combined experimental-theoretical study, we find that the predominant binding form is monodeprotonated, with evidence for the chelate mode.

Coordination Polymers and Oligonuclear Systems Based on Oximate or Hydroxamate Building Blocks: Magnetic and Sorption Properties

The review covers structures and properties of compounds, possessing porous crystal lattices, or coordination polymers, which are assembled on the basis of polynuclear oximate or hydroxamate complexes of 3d metals. It is shown that magnetic properties of such systems are governed by the exchange interactions in the polynuclear building blocks and can be pre-determined by the appropriate choice of starting compound. In contrast, the structure and topology of the framework, obtained on the basis of polynuclear oximate or hydroxamate, do not correlate with the quantity of vacancies in coordination spheres of metal ions in the starting compound, as well as they do not correlate with the quantity of ligand donor atoms. Some of the compounds, considered in this review, show ability to absorb different substrates. Such absorption is different from "classical" filling of micropores; sorption capacity is governed by the energy of host-guest interactions rather than the volume of rigid micropores in crystal lattice. Keywords: Building block approach, coordination polymer, hydroxamate, magnetic properties, metallacrown, oxime, sorption properties.

Synthesis and structural characterisation of bismuth(III) hydroxamates and their activity against Helicobacter pylori.

Seven new bismuth(iii) hydroxamate complexes derived from the hydroxamic acids N-methylfurohydroxamic acid (H-MFHA), N-benzoyl-N-phenylhydroxamic acid (H-BPHA), salicylhydroxamic acid (H2-SHA), benzohydroxamic acid (H2-BHA), and acetohydroxamic acid (H2-AHA) have been synthesized and characterized. The complexes formed are either tris-hydroxamato complexes containing only mono-anionic ligands, [Bi(H-SHA)3], [Bi(MFHA)3] and [Bi(BPHA)3]; mixed-anion complexes, [Bi(SHA)(H-SHA)] and [Bi(AHA)(H-AHA)]; and potassium bismuthate complexes, K[Bi(SHA)2] and K[Bi(BHA)2]. The solid-state structure of three complexes has been determined through single crystal X-ray diffraction; [Bi(MFHA)3]2·Me2C[double bond, length as m-dash]O, {[Bi(SHA)(H-SHA)(DMSO)2][Bi(SHA)(H-SHA)(DMSO)]·DMSO}∞ and [Bi(BPHA)3]2·2EtOH. All the complexes and their parent acids were assessed for the bactericidal activity against three strains of Helicobacter pylori (26695, B128 and 251). Of the acids, only acetohydroxamic acid showed any activity at low concentrations (MIC 6.25 μg mL(-1); 83.26 μM) while the others were not toxic below 25 μg mL(-1). In contrast, their bismuth(iii) complexes all showed excellent activity across all three strains (e.g. 0.28 μM for [Bi(H-SHA)3] to 6.01 μM for K[Bi(BHA)2] against strain 251) with only minor variations in activity being both ligand and composition dependant.