Synthesis and complexation properties of novel triazoyl-based ferrocenyl ligands

Two new ligand derivatives of ferrocene, namely N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbimine (L1) and N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl]ferrocene carbamide (L2), were synthesised in good yields by reacting the known compound 3,5-di-pyridine-2-yl-[1,2,4]triazol-4-ylamine (1) with ferrocenecarbaldehyde and chlorocarbonyl ferrocene, respectively. The structures of L1 and L2 were determined by X-ray crystallography. The complexation of L1 and L2 with Cu^I, Ag^I, Zn^II and Cd^II was studied by NMR and UV-vis spectroscopies, as well as by electrochemistry, with titrations used to determine metal:ligand stoichiometries. The cyclic voltammograms of L1 and L2 and their respective complexes indicated reversible one-electron transfers corresponding to the Fc^0/+ redox couple (Fc = ferrocene), with formal electrode potentials shifting to more positive values upon metal complexation.     

4,4′-联吡啶多钼酸盐的合成、结构与变色性质

通过水热合成法,合成了4,4′-联吡啶多钼酸盐((4,4′-bipyridine)Mo7O22·H2O)单晶超分子化合物.通过元素分析、热重-差热分析(TG-DTA)、粉末X射线衍射(XRD)、单晶X射线衍射、傅里叶变换红外(FTIR)光谱、紫外-可见漫反射光谱(UV-VisDRS)和电子自旋共振(ESR)技术对其组成、热稳定性、结构、光谱和电子特性进行了表征.实验结果表明:该超分子化合物的分子式为C10H12Mo7N2O23,在空气中320℃以下不分解.属于单斜晶系(空间群为P2/n),晶胞参数为a=1.22561(19)nm,b=0.55222(9)nm,c=1.8385(3)nm,β=103.221(2)°,V=1.2113(3)nm3,Z=2和Dc=3.289g·cm-3.基于F2的最终统计:GOF=0.982,R1=0.0228和wR2=0.0557(I2σ(I)).该单晶超分子化合物由质子化的4,4′-联吡啶阳离子和多金属钼酸盐阴离子[Mo7O22]2-及结晶水组成.它们通过氢键、静电引力和分子间作用力结合在一起的,并构成二维网络结构.样品在光照或加热条件下具有光致变色和热致变色性质.XRD和FTIR证明,变色前后,样品的结构除轻微的畸变外几乎没有变化;而ESR结果表明,光致变色与热致变色的机理可能存在差别.该光致和热致变色的超分子化合物能够为变色机理研究提供参考模型,并在传感器和光敏材料等领域具有潜在应用.     

Sensitization effects of supramolecular assemblies on the luminescence of terbium-ion prulifloxacin complexes

Luminescence enhancement of terbium-ion prulifloxacin complexes (Tb(III)-PUFX) in supramolecular hydrogels formed by assembly of 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS) was investigated by steady-state fluorescence, varying temperature fluorescence and time-resolved fluorescence. The luminescence images show that Tb(III)-PUFX were dispersed in the DBS gels. The luminescence intensity of Tb(III)-PUFX in the DBS gels was significantly increased in comparison with that in corresponding aqueous solutions. The varying temperature fluorescent spectra show that the luminescence intensity of Tb(III)-PUFX decreased with an increase in the temperature. This implies that the luminescence enhancement of Tb(III)-PUFX is related to the dissociation and the formation of the DBS assemblies. Time-resolved fluorescence measurements show slower rotational motion in DBS gels in comparison with that in the corresponding aqueous solutions. This may be ascribed to a unique microstructure of three-dimensional network formed by DBC aggregates, resulting in deactivation of the nonradiative relaxation. The images of field emission scanning electron microscopy and polarized optical microscopy indicate that the morphology of the DBS assemblies was not influenced upon addition of Tb(III)-PUFX to the DBS gels.     

Synthesis and characterization of a new dimeric polyoxometalate based on Anderson-type polyoxoanions and a trinuclear lanthanide coordination complex

An unusual compound, H₅[(C₆NO₂H₄)₄(H₂O)₁₅Nd₃][IMo₆O₂₄]₂·13.5H₂O (1) has been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray diffraction. Compound 1 consists of two [IMo₆O₂₄]^5? units joined by a trinuclear neodymium-pyridine-4-carboxylic acid complex, resulting in a dimeric polyoxometalate, which further interact via weak intermolecular interactions to form a three-dimensional supramolecular framework with channels. To the best of our knowledge, no analogous dimeric polyoxometalate structure composed of an Anderson-type polyoxometalate has been reported in the literature.     

Supramolecular assemblies of two piperazine metal-organic bismuth(III) derivatives: a new precursor for the preparation of bismuth(III) oxide bromide nano-structures

Two BiBr₃ supramolecular complexes, [Bi(2-bpmp)Br_2.06Cl_0.94] (1) and [Bi(4-H₂bpmp)Br_4.29Cl_0.71]·H₂O (2) {2-bpmp = N,N′-bis(2-pyridylmethyl)piperazine and 4-bpmp = N,N′-bis(4-pyridylmethyl)piperazine}, were prepared by reaction of bismuth(III) chloride and potassium bromide with two nitrogen donor ligands under thermal gradient conditions using the branched tube method. Compounds 1 and 2 were structurally characterized by single-crystal X-ray diffraction. In monomeric 1, bismuth is coordinated by two pyridyl and piperazine nitrogens of 2-bpmp, and by three halides. Compound 2 is also monomeric but is bonded to only one pyridyl nitrogen. In both compounds, extensive hydrogen-bonding interactions lead to supramolecular networks; in 2, the hydrogen bonds are augmented by π–π stacking interactions. Thermal stabilities of both compounds were studied by thermal gravimetric and differential thermal analyses. Thermal decomposition of nanosized 1 and 2 in air produced BiOBr nanoparticles.     

Multiresidue analysis of sulfonamides in meat by supramolecular solvent microextraction,liquid chromatography and fluorescence detection and method validation according to the 2002/657/EC decision

A multiresidue method was described for determining eight sulfonamides, SAs (sulfadiazine, sulfamerazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfadoxine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline) in animal muscle tissues (pork, chicken, turkey, lamb and beef) at concentrations below the maximum residue limit (100 μg kg⁻¹) set by the European Commission. The method was based on the microextraction of SAs in 300-mg muscle samples with 1 mL of a supramolecular solvent made up of reverse micelles of decanoic acid (DeA) and posterior determination of SAs in the extract by LC/fluorescence detection, after in situ derivatization with fluorescamine. Recoveries were quantitative (98–109%) and matrix-independent, no concentration of the extracts was required, the microextraction took about 30 min and several samples could be simultaneously treated. Formation of multiple hydrogen bonds between the carboxylic groups of the solvent and the target SAs (hydrogen donor and acceptor sum between 9 and 11) were considered as the major forces driving microextraction. The method was validated according to the European Union regulation 2002/657/EC. Analytical performance in terms of linearity, selectivity, trueness, precision, stability of SAs, decision limit and detection capability were determined. Quantitation limits for the different SAs ranged between 12 μg kg⁻¹ and 44 μg kg⁻¹, they being nearly independent of matrix composition. Repeatability and reproducibility, expressed as relative standard deviation, were in the ranges 1.8–3.6% and 3.3–6.1%. The results of the validation process proved that the method is suitable for determining sulfonamide residues in surveillance programs.     

Supramolecular solvent-based microextraction of ochratoxin A in raw wheat prior to liquid chromatography-fluorescence determination

A supramolecular solvent made up of reverse micelles of decanoic acid, dispersed in a continuous phase of THF:water, was proposed for the simple, fast and efficient microextraction of OTA in wheat prior to liquid chromatography-fluorescence determination. The method involved the stirring of 300 mg-wheat subsamples (particle size 50 μm) and 350 μL of supramolecular solvent for 15 min, subsequent centrifugation for 15 min and the direct quantitation of OTA in the extract, previous 5.7-fold dilution with ethanol/water/acetic acid (49.5/49.5/1), against solvent-based calibration curves. No clean-up of the extracts or solvent evaporation was needed. Interactions between the supramolecular solvent and major matrix components in the wheat (i.e. carbohydrates, lipids and proteins) were investigated. The reverse micelles in the extractant induced gluten flocculation but only in the coacervation region of lower analytical interest (i.e. at percentages of THF above 11%). The quantitation of OTA was interference-free. Representativity of the 300 mg-wheat subsamples was proved by analysing a reference material. OTA recoveries in wheat ranged between 84% and 95% and the precision of the method, expressed as relative standard deviation, was 2%. The quantitation limit of the method was 1.5 μg kg⁻¹ and was below the threshold limit established for OTA in raw cereals by EU directives (5.0 μg kg⁻¹). The method developed was validated by using a certified reference material and it was successfully applied to the determination of OTA in different wheat varieties from crops harvested in the South of Spain. OTA was not detected in any of the analysed samples. This method allows quick and simple microextraction of OTA with minimal solvent consumption, while delivering accurate and precise data.     

Towards the construction of mesoscopic species with emergent and functional properties via the derivatisation of molybdenum-oxide ‘Giant-Wheel’ clusters

Polyoxometalate chemistry has proved to be an extraordinary source of a large variety of compounds, clusters and solid–state structures—these are built using very simple metal oxygen fragments linked together in an enormous variety of modes. Herein we focus on the ‘Giant-Wheel’ clusters which contain 154 and 176 Mo atoms and examine the variety of structural modifications that has been achieved to date with these systems. The generation of structural vacancies (here referred to as defects), substitution of ligands, and incorporation of hetero-metallic centres offers many fascinating possibilities with respect to the targeted functionalisation of these species for a pre-determined function and application. Furthermore, evidence is presented which suggests the identity of the most labile and, therefore, most easily derivatised units present in these systems. The consequences of this assignment are then discussed in the context of inter- (formation of layers and chains) and intra- (assembly inside the cavity) molecular growth.     

One-pot synthesis of supramolecular polymer containing quadruple hydrogen bonding units

A facile, efficient technique was built to synthesize a supramolecular material containing quadruple hydrogen bonding sites. The current approach presented here involves a single-step reaction between the amine of precursor, e.g. methyl isocytosine (MIC) and the epoxy group of polymer, e.g. poly(ethylene glycol diglycidyl ether) (PEG DGE, M_n = 526 g/mol, as verified using ¹H NMR and FT-IR spectroscopy. Wide angle X-ray scattering (WAXS), UV/visible spectroscopy and differential scanning calorimeter (DSC) clearly show that the product is not a simple mixture of two components, but the supramolecular polymer containing quadruple hydrogen bonding sites. Complex melt viscosities reveal that mechanical properties of the supramolecular polymer are enhanced by more than 10⁴ times compared to the pristine low molecular weight polymer, giving rise to the significant change of physical state from liquid to solid. Current approach also illustrates an advantageous route because it does not need the selective use of monofunctionalized precursor and not produce a dead, difunctionalized precursor.     

A versatile liposome/cyclodextrin supramolecular carrier for drug delivery through the blood-brain barrier

For many commercial drugs, reaching the central nervous system in large amount without damaging the blood-brain-barrier (BBB) remains a challenging task. We present here a supramolecular strategy aiming at using a well-defined cyclodextrin-coated liposomes as drug carrier and adamantoyl saccharides as BBB-interacting ligands. In this study, the liposome is constituted of n-alkyldimethylammoniumcyclodextrins incorporated in the lipid bilayer of a 3/7 cholesterol/dipalmitoylphosphatidylcholine mixture and the ligand is constituted of an adamantoylglucose molecule whose adamantoyl moiety can be included in the CD cavity. The whole supramolecular assembly has been characterized by light-scattering and ³¹P NMR measurements. Toxicity and permeability studies on an in vitro model of the BBB clearly demonstrated a 5-fold improved ability of the modified liposome to enter the BBB-endothelial cells compared to the non-coated liposome. Fluorescence labelling of these liposomes is also displayed with DiI as a fluorescent probe.