M. D. Reshetova

New bioorganometallic ferrocene derivatives as efficient mediators for glucose and ethanol biosensors based on PQQ-dependent dehydrogenases

One known and two new ferrocene-containing mediators incorporating the organometallic moiety and the fragments of natural substrates of oxidative enzymes, viz. 4-ferrocenylphenol (FP), 2-ferrocenyl-4-nitrophenol (FNP), and N -(4-hydroxybenzylidene)-4ferrocenylaniline (HBFA), were studied as electron transfer mediators between the coenzyme pyrroloquinoline quinone (PQQ) of glucose (GDH) and alcohol (ADH) dehydrogenases and the carbon electrode surface. A screen-printed carbon electrode (SPCE) suitable for ADH and GDH immobilization served as a transducer. The electrodes were integrated into a flow-through amperometric cell. All data were obtained at a flow rate of 1 ml min � 1 . The maximal currents (jmax) obtained from the calibration curves for the oxidation of ethanol and D-glucose by ADH and GDH of 2.3 and 3.0 mA, respectively, were obtained when SPCE was modified with HBFA, i.e. with a mediator with a longer arm and a high degree of conjugation. The biosensors were used for ethanol and D-glucose measurements in beverages. There was a good correspondence (r � /0.978 for D-glucose and r � /0.920 for ethanol) between the data obtained by using the biosensors, on one hand, and by the refractometric or hydrometric methods, on the other. The operational stability of biosensors is determined by the inactivation of the immobilized enzymes rather than by leakage of a mediator from an electrode. # 2002 Elsevier Science B.V. All rights reserved.

4-Ferrocenylphenol as an electron transfer mediator in PQQ-dependent alcohol and glucose dehydrogenase-catalyzed reactions

Abstract Enzyme electrodes containing pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) and glucose dehydrogenase (GDH) as a biological component in combination with 4-ferrocenylphenol ( 1 ) as an electron transfer mediator between PQQ and a carbon electrode were constructed and used for measurements of ethanol and d -glucose. Analysis of the current response of the carbon electrodes modified with 1 at different pH and potentials demonstrated that 1 participates in the bioelectrocatalytic oxidation of d -glucose or ethanol. The biosensors showed the highest response at pH 5.5 and the working potentials of 0.3 and 0.4 V (versus Ag|AgCl) for ADH and GDH, respectively. The electrocatalytic processes under such conditions at these electrodes are characterized by the apparent values of the Michaelis constants K M app of 7.1 and 13 mM and the maximal current density j max 40 and 26 μA cm −2 for ethanol and d -glucose, respectively. No electrocatalysis was found when glucose oxidase from Aspergillus niger was used instead of GDH.

Novel diamides of 2,2′-dipyridyl-6,6′-dicarboxylic acid: synthesis, coordination properties, and possibilities of use in electrochemical sensors and liquid extraction

The procedure was proposed for the synthesis of various dipyridyldiamides. Their various properties in the series of rare-earth elements were studied. The possibility to use the synthe-sized compounds in polymer membranes of electrochemical sensors for the development of novel types of sensors was shown. A comparison of the influence of the ligand structure on the extraction and sensor characteristics was performed.

Pincer ligands based on α-amino acids: I. Synthesis of polydentate ligands from pyrrole-2,5-dicarbaldehyde

New chiral pincer ligands having CH=N moieties were synthesized by condensation of 1H-pyrrole-2,5-dicarbaldehyde with l-methionine and l-histidine methyl esters. Their reduction under mild conditions (NaBH4, −30°C) gave the corresponding amine ligands in high yields. An improved procedure for the preparation of 1H-pyrrole-2,5-dicarbaldehyde was proposed.

Analysis of vibrational spectra of naphthalene, deuterionaphthalenes, and chromium (η6-naphthalene)tricarbonyl based on density functional calculations

The vibrational frequencies and force constants for naphthalene (C10H8), 1,4,5,8- and 2,3,6,7-tetradeuterionaphthalenes (C10H4D4), octadeuterionaphthalene (C10D8), and chromium (η6-naphthalene)tricarbonyl were calculated by the DFT method using the PBE approximation in extended and split bases. The results calculated without the use of scaling factors are in good agreement with the IR and Raman experimental data. All vibrational frequencies for the free ligand and π-complex molecules were assigned. The influence of coordination to the transition metal on the frequencies and force field of the naphthalene molecule (both for the free ring and the ring coordinated to the transition metal) was discussed.

Enzymatic chemistry of ferrocenes: micellar tuning of the glucose oxidase reactivity toward solubilized electrochemically generated n-alkylferricenium cations

Abstract Remarkable kinetic tuning of the glucose oxidase activity by the nature of micelle–alkylferrocene assemblies is realized during the electrochemical coupling between the enzyme reduced by d -glucose and the electrochemically generated alkylferricenium cations H(CH2)nFc+ (n=0, 2, 4–8) solubilized in micelles of neutral, positively and negatively charged surfactants (Triton X-100, CTAB and SDS, respectively) in the presence of d -glucose at pH 7. The relative electron-transfer rate increases 14 times for n-butylferrocene in CTAB and decreases by a factor of 3000 for n-pentylferrocene in SDS micelles relative to their reactivities in the neutral Triton X-100 medium.

Solvent switchable CuII complexes

A new tetranuclear complex Cu4, [Cu2L(OH)]2·2CH3OH·H2O (1), with the functionalized Schiff base ligand 2,6-bis((2-(acetylamino)phenylimino)methyl)-4-tert-butylphenol (H3L) has been obtained and characterized in the solid state by X-ray diffraction. The formation of the tetranuclear species is solvent dependent, the presence of water being a determinant in its isolation. Based on the mass-spectrometric evidence, the behaviour of the H3L–CuII system in the presence of water was investigated. Namely, water can switch the nuclearity of the CuII cluster from dinuclear to tetranuclear. The redox behaviour of this species in DMSO solution, showing two cathodic metal-centred peaks at EP = −0.80 and −1.35 V and an irreversible ligand-centred anodic peak at EP = 1.03 V, was found to be similar to that of a pristine dinuclear complex. The tetranuclear species was also characterized in the solid state by magnetic measurements, showing a dominating bulk antiferromagnetic behaviour, with a singlet ground state at approximately 2 K. DFT calculations permitted us to estimate the strong intradimer antiferromagnetic exchange interaction (J1 = −440 cm−1), together with two weak interdimer ferromagnetic exchange interactions (J2 = +0.5 and J3 = +1.7 cm−1).

Quantum chemical modeling of 2,2´-bipyridine-6,6´-dicarboxylic acid diamide structures: a relationship between the extraction ability and conformational behavior of the ligands

Approaches to the theoretical evaluation of a comparative affinity to metal ions of 2,2´-bipyridine-6,6´-dicarboxylic acid diamides, which are new promising extracting agents for the isolation of minor actinides from highly acidic radioactive waste, were tested in terms of the density functional theory (DFT) with the PBE0 functional in the TZ basis sets. The amides containing an aromatic substituent are more preorganized for binding with metal ion than their tetraalkyl-substituted analogs. However, the influence of substituents in the aromatic fragment of the molecule is very weak. The introduction of substituents into the pyridine or anilide fragment of the diamide molecule exerts almost no effect on the conformational dynamics and on the charges on the heteroatoms, whereas the extraction behavior depends strongly on these factors. The estimation of the affinity to metal ions by the calculation of the reorganization energy of the ligand for binding in a complex with metal gave the results differed from those calculated by the PBE0 method. The obtained values of the energies correlate well with the distribution coefficients of lanthanides for extraction from nitric acid solutions (Pearson´s coefficient is–0.86 for 0.5 M HNO3 and–0.91 for 1 M HNO3) and also are well described in the framework of the linear model. The method for the estimation of reorganization energies is more timeand labor-consuming than an analysis of the conformational behavior but gives much better results because makes it possible to evaluate qualitatively preorganization and find quantitative parameters for this estimation.

Binuclear and polynuclear transition metal complexes with macrocyclic ligands. 2. New macrocyclic Schiff"s base in the reaction of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene. Synthesis and structural, spectroscopic, and theoretical study

Condensation of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macrocyclic Schiffs base containing the alternating >C=N and >CH—NH fragments. In solution, this compound exists as the only isomer in which two endocyclic hydrogen atoms are bound to the oxygen atoms of the phenol groups and two other endocyclic H atoms are attached to the nitrogen atoms of the CH2—NH fragments. All endocyclic protons are involved in hydrogen bonding and undergo rapid exchange with each other at room temperature. In the crystal, the planar macrocyclic molecules are arranged in closely packed stacks. The steric hindrances resulting from overlapping of the bulky tert-butyl groups are eliminated through rotation of the molecules with respect to each other in the adjacent layers. Study of the potential energy surface for the Schiffs base under consideration by the DFT method demonstrated that the structure corresponding to the global minimum is similar to that found in solution. However, the isolated molecule is nonplanar, its macrocycle adopting a ladder conformation. The local minimum on the potential energy surface whose energy is 2.6 kcal mol–1 higher than that of the global minimum corresponds to the zwitterionic structure in which all four endocyclic hydrogen atoms are attached to the nitrogen atoms and the macrocycle adopts a tub conformation. Flattening of the ring is considered as a consequence of stacking interactions between the molecules in the crystal.

Binuclear and polynuclear transition metal complexes with macrocyclic ligands 1. Synthesis and the structure of an antiferromagnetic binuclear nickel complex prepared by the reaction of o-phenylenediamine with pyrrole-2,5-dicarbaldehyde and nickel pivalate

The reaction of pyrrole-2,5-dicarbaldehyde (1) with o-phenylenediamine (2) in anhydrous EtOH afforded a [1+1]-condensation product, viz., Schiffs base. The structure of the latter was established by NMR spectroscopy and X-ray diffraction analysis. The reaction of this product or a mixture of 1 and 2 with Ni9(μn-OOCBut)12(HOOCBut)4(μ4-OH)3(μ3-OH)3 in MeCN in the presence of AcOH gave rise to an antiferromagnetic binuclear complex. According to the X-ray diffraction data, the macrocycle in the latter complex is a [2+2]-condensation product of compounds 1 and 2, μeff ranging from 0.569 to 2.614 μB (2—301 K), –2J = 360 cm–1. The Ni2(OAc)2 fragment is located in the central cavity of the macrocycle. The structures of the condensation products are discussed based on the results of DFT quantum-chemical calculations.