Study on Preferential Solvation of Water by Electrochemical Method

The preferential solvation of water plays an important role in ferrocene research which is a subject of current interest. Voltammetric investigations were carried out for Au electrode in acetonitrile/water, showing preferential solvation of water. In our work, the preferential solvation of water in acetonitrile/water was studied by electrochemical methods including cyclic volitammetry, electrochemical impedance spectra and double‐step chronoamperometry. Ferrocenemethanol (FcCH₂OH) molecules as a solute spontaneously adsorb on the electrode surface in anhydrous acetonitrile, resulting from acetonitrile molecules tend to form an acetonitrile solvent layer on the surface of the electrode and acetonitrile solvent layer has a lower energy barrier than the aqueous solvent layer, which has been obtained by modeling solvation. The solvent strongly influences electrochemical behavior of solute. Once there is an amount of water in acetonitrile solvent, FcCH₂OH that adsorbed on the electrode surface desorb. This is because water preferentially solvate with FcCH₂OH in term of intermolecular forces between solvent and solute. Moreover, hydrogen bond between water molecules and FcCH₂OH molecules is stronger than dipole‐dipole interaction between acetonitrile molecules and FcCH₂OH molecules in solvation effect. Through electrochemical behavior of FcCH₂OH changing, preferential solvation of water is analyzed by electrochemical methods.     

Nanocarbon Paste Electrodes

The electrochemical behaviour of carbon paste electrodes prepared using nanocarbon and mineral oil was investigated and the results contrasted with different carbon and carbon pastes electrodes. The composition of carbon paste was studied by performing cyclic voltammetry performed in 0.1 M KCl solution in the presence of 4.0 mM Ru(NH₃)₆Cl₃, a well‐characterized redox system commonly used to test the electrode behaviour. After optimisation of the paste composition, the sensors chosen were tested for the analysis and characterization of three different systems: Ru(NH₃)₆^3+/2+, FcCH₂OH/FcCH₂OH⁺ and acetaminophen. The ability to obtain high quality voltammetry from the nanocarbon electrode was demonstrated and simulation of the voltammetry allowed the extraction of electrode kinetic parameters with high precision.     

The Measurement of the Gibbs Energy of Transfer Between Oil and Water Using a Nano‐Carbon Paste Electrode

The use of nano‐carbon paste electrodes for the measurement of Gibbs energies of transfer between oil and aqueous phases is reported. In this method the oil of interest is used as the binder for the nano‐carbon paste electrodes and the molecule of interest is dissolved in the organic or aqueous phase. Voltammetry is performed over a period of time and used to monitor the transfer of the molecule between the two phases. The method is illustrated for the transfer of ferrocenemethanol between water and oil using the ferrocenemethanol / ferroceniummethanol (FcCH₂OH/FcCH₂OH⁺) redox couple. Three pairs of voltammetric peaks were observed in a 0.1 M KCl solution when the nano‐carbon paste electrode was modified by dissolution of FcCH₂OH in the binder oil: P1 [E=0.23 V, 0.17 V vs. Ag/AgCl (1 M KCl)], P2 [E=0.36 V, 0.32 V vs. Ag/AgCl (1 M KCl)] and P3 [E=0.55 V, 0.46 V vs. Ag/AgCl (1 M KCl)]. These are assigned to the FcCH₂OH species existing in the aqueous solution [FcCH₂OH(aq)/FcCH₂OH⁺(aq)], originating in the oil (o) [FcCH₂OH(o)/FcCH₂OH⁺(aq)] and to oxidation of adsorbed (ads) material on the nano‐carbon [FcCH₂OH(ads)] respectively. When supporting electrolyte containing the anions Cl^?, NO₃^? or SCN^? was used, an expulsion of the oxidised ferrocene occurred and the difference in midpoint potentials (E_mid) between the peaks P1 and P2 observed in these experiments allowed the calculation of the Gibbs energy (ΔG°) of transfer of ferrocenemethanol from water to oil. The average ΔG° value thus obtained was (?12.7±0.2) kJ mol^?1. For more hydrophobic anions (X^?=PF₆^?, AsF₆^?), the electron transfer is coupled to the transfer of the anion into the oil and the ΔG° for the transfer of the ion pair of FcCH₂OH⁺ and X^? ions from water to oil was found to be ?1.3 and ?3.9 kJ mol^?1 for PF₆^? and AsF₆^? respectively.     

Synthesis, properties and crystal structures of ferrocene derivatives containing pyrazinium and quinoxalinium units

The pyrazinium salt [FcCH₂pyz][BF₄] (1) and the quinoxalinium salt [FcCH₂quin][BF₄] (2) were prepared by the reaction of [FcCH₂][BF₄] with pyrazine and quinoxaline, respectively and characterised by spectroscopic methods, cyclic voltammetry and by single-crystal X-ray diffraction, which revealed the absence of any π-π-stacking motifs in the crystal structures.     

Addition of α-hydroxyalkylferrocenes to electrochemically oxidized poly(aniline)

A series of α-hydroxyalkylferrocenes (ferrocenemethanol [FcCH₂OH], α-hydroxyethylferrocene, and 1,1′-ferrocenedimethanol) have been shown to incorporate into highly oxidized films of poly(aniline) [PAn]. Surface immobilization is readily evident in cyclic voltammetric studies by the rapid growth of a pair of sharp redox waves at E_1/2=0.455 V versus SCE in the case of FcCH₂OH. A general mechanism for the attack of α-hydroxyalkylferrocenes on oxidized PAn is inferred from the electrochemical data.     

Copper(II) and lanthanoid(III) complexes of a new β-diketonate ligand with an appended non-coordinating phenol group

New mononuclear compounds of the ligand 1-(2-hydroxyphenyl)-3-phenylpropane-1,3-dione (H₂L) with Cu(II) and several lanthanoid(III) ions, where Ln(III) = Pr, Nd, Eu, Gd, have been synthesized and characterized by spectroscopic methods and X-ray crystal structure determinations. In all compounds, the ligand coordinates in a bidentate chelating manner, using the diketone function. In the [Cu(HL)₂], the coordination geometry of Cu(II) ion is slightly distorted square-planar; two strong intramolecular (OH?O) hydrogen-bonding interactions are established between the phenolate group and the neighboring ketone function. The lanthanoid(III) compounds have the general formula [Ln(HL)₃(CH₃OH)₂] · CH₃OH · 2H₂O; the lanthanoid(III) ion (Ln) is eight-coordinated and the coordination geometry is based on a distorted square-antiprism. In addition to the intramolecular hydrogen bonding (OH?O), intermolecular hydrogen-bonding interactions are also present between the coordinated methanol molecule and the non-coordinated methanol molecule giving rise to a three-dimensional network.     

Synthesis and structure of ferrocenylmethylphosphines, their borane adducts, and some related derivatives

Syntheses of the known ferrocenylmethylphosphines FcCH₂PH₂ (2, Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)), (FcCH₂)₂PH (3), and (FcCH₂)₃P (4) have been reinvestigated. The reaction of [FcCH₂NMe₃][I] with P(CH₂OH)₃, generated from [P(CH₂OH)₄][Cl] and KOH, gave a mixture of the major product (FcCH₂)P(CH₂OH)₂ (1) and over-alkylated (FcCH₂)₂P(CH₂OH) (9). Treatment of pure 9 with Na₂S₂O₅ gave the secondary phosphine 3; slow addition of Na₂S₂O₅ to 1 gave 2 in improved yield. Reaction of 1 with [FcCH₂NMe₃][I], followed by treatment with NEt₃, gave the tertiary phosphine (FcCH₂)₃P (4), along with the known phosphonium salt [(FcCH₂)₄P][I] (5), which could be prepared in higher yield by adjusting the stoichiometry. Phosphine 4 oxidized slowly in air to yield (FcCH₂)₃P(O) (12), was protonated by HBF₄(OMe₂) to give [(FcCH₂)₃PH][BF₄] (13), and reacted with Pt(COD)Cl₂ or PtCl₂ to yield a mixture of cis- and trans-Pt(P(CH₂Fc)₃)₂Cl₂ (14). Silylation of 2 with n-BuLi/Me₃SiCl gave FcCH₂P(SiMe₃)₂ (10); treatment of 1 with Me₃SiCl/Et₃N gave FcCH₂P(CH₂OSiMe₃)₂ (11). The phosphine-borane adducts FcCH₂PH₂(BH₃) (6), (FcCH₂)₂PH(BH₃) (7), (FcCH₂)₃P(BH₃) (8) and (FcCH₂)P(CH₂OSiMe₃)₂(BH₃) (15) were prepared from the corresponding phosphines and BH₃(SMe₂). The phosphines 2, 3, and 4, phosphonium salts 5 and 13, phosphine oxide 12, Pt complex trans-14, and phosphine-boranes 6, 7 and 8 were structurally characterized by X-ray crystallography. The solid cone angle of (FcCH₂)₃P, 139°, in Pt complex 14 showed that 4 was bulkier than PPh₃, but less sterically demanding than P(t-Bu)₃. The structural changes observed on quaternization of P (shorter P-C bonds and larger angles at P), along with results from NMR and IR spectroscopy and DFT calculations, were consistent with the expected rehybridization at phosphorus. Related observations for analogous methylphosphines suggest that methyl and ferrocenylmethyl phosphorus substituents have similar properties.     

Different hydrogen-bonding patterns in two [Zn(ENTPP)] complexes with water or methanol as ligands

We have synthesized zinc complexes of H₂ENTPP (5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin) as a model to study hydrogen-bonding interactions. When water or methanol is a ligand, crystals of [Zn(ENTPP)(CH₃OH)] or [Zn(ENTPP)(H₂O)]?·?C₆H₅CH₃ were obtained. In both structures, the ligand has hydrogen-bonding interactions, but in different patterns. In [Zn(ENTPP)(CH₃OH)], the methanol oxygen and carboxylate oxygen in the naphthyl group form an intermolecular hydrogen bond. In [Zn(ENTPP)(H₂O)]?·?C₆H₅CH₃, there are two independent molecules A and B. In molecule B, there is an intramolecular hydrogen bond between the water oxygen and the carboxylate oxygen, while in molecule A, besides the intramolecular hydrogen bond, there is an intermolecular hydrogen bond between the water oxygen and the carboxylate oxygen. ¹H NMR spectra suggest the binding of methanol or water to zinc are equilibrium processes in solution. Equilibrium constant has been determined by UV-Vis measurements, and it suggests the binding affinity of zinc to methanol has been moderately increased.     

Deuterium Isotope Effect on Excess Enthalpies of Methanol or Ethanol and Their Deuterium Derivatives at 298.15 K

Excess enthalpies of six binary mixtures of CH₃ OD+CH₃ OH, CH₃ OD+CD₃ OD, CD₃ OD+CH₃ OH, C₂ D₅ OD+C₂ H₅ OH, C₂ D₅ OD+C₂ H₅ OD, C₂ H₅ OD+C₂ H₅ OH have been determined over the whole range of mole fractions at 298.15 K in order to know the isotopic effect on hydrogen-bonding accurately, although there are many reports on the differences in the strength of hydrogen-bonding between OH and OD. All excess enthalpies measured are very small and endothermic. The mixtures of CH₃ OD+ CH₃ OH, and C₂ D₅ OD+C₂ H₅ OH showed the largest excess enthalpies among each methanol and ethanol mixtures. The difference of intermolecular interaction between OH and OD in methanol and ethanol was almost same value of (1.82±0.04) J mol^-1 Excess enthalpies of 1,4-dimethylbenzene+1,3-dimethylbenzene and 1,4-dimethylbenzene+1,2-methylbenzene were measured by three different principle calorimeters at 298.15 K in order to know the precision of calorimetry for a small enthalpy change. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and characterization of ferrocenylalkoxygermatranes and crystal structures of FcCH2OGe (OCH2CH2)3N and FcCH(CH3)OGe(OCH2CH2)3N1

Germatranes bearing a ferrocenylalkoxyl moiety have been obtained by the reaction of HOGe(OCH₂CH₂)₃N with various ferrocenyl alcohols. A convenient new synthesis method of FcCH₂OGe(OCH₂CH₂)₃N was reported. FcCH₂OGe(OCH₂CH₂)₃N was prepared in 93% yield when FcCH₂OH reacted with HOGe(OCH₂CH₂)₃N in chloroform at room temperature in the presence of molecular sieves (3 Å) as a dehydrating agent. All compounds were characterized by elemental analysis, ¹H NMR and IR spectroscopy. The molecular structures of FcCH₂OGe(OCH₂CH₂)₃N and FcCH(CH₃)OGe(OCH₂CH₂)₃N have been determined by X‐ray diffraction. The antitumor activities of FcCH₂OGe(OCH₂CH₂)₃N and p‐FcC₆H₄CH₂OGe(OCH₂CH₂)₃N were determined. Copyright © 2005 John Wiley & Sons, Ltd.     

Ferrocenylalkylation processes under electrospray ionization conditions

The electrospray ionization behavior of some ferrocenylalkylazoles CpFeC₅H₄CH(R)Az (AzH are derivatives of imidazole, pyrazole, triazole and their benzo analogs; R = H, Me, Et, Ph), ferrocenylalkanols CpFeC₅H₄CH(R)OH (R = H, Me), and mixtures of the latter with azoles was studied. The electrospray ionization mass spectra of these compounds, in addition to the molecular ion [M]^+·, the protonated molecule [M + H]⁺, and ferrocenylalkyl cation [FcCHR]⁺ peaks, exhibit also intensive peaks for the binuclear ions [(FcCHR)₂X]⁺ (X = Az or O), resulting from ferrocenylalkylation of the initial compounds with the ferrocenylalkyl cations. Electrospray ionization of an equimolar mixture of ferrocenylmethanol FcCH₂OH and imidazole gives the protonated ferrocenylmethylimidazole molecule [FcCH₂Im + H]⁺ and the [FcCH₂(Im)₂ + H]⁺ dimer, apart from the ions typical of each component, i.e., ferrocenylalkylation of azoles with the ferrocenylalkylcarbinols, known in the chemistry of solutions, takes place under electrospray conditions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1318–1321, August, 2006.     

Ferrocene-mediated carbon paste electrode modified with d-fructose dehydrogenase for batch mode measurement of d-fructose

A mediated modified carbon paste and renewable surface electrode for fructose amperometric measurement based on d-fructose dehydrogenase (FDH) was prepared and optimized. Commercially available ferrocene (FcH) and hydroxymethyl ferrocene (FcCH₂OH) were used as mediators. The substituted FcH showed better linearity and higher sensitivity. The influence of different experimental parameters was studied for optimum analytical performance. The final FDH-modified electrode showed good analytical performance for batch mode measurements of fructose.     

Spontaneous Synthesis of Silver-Nanoparticle-Decorated Transition-Metal Hydroxides for Enhanced Oxygen Evolution Reaction

The fabrication of metal-supported hybrid structures with enhanced properties typically requires external energy input, such as pyrolysis, photolysis, and electrodeposition. In this study, silver-nanoparticle-decorated transition-metal hydroxide (TMH) composites were synthesized by an approach based on a spontaneous redox reaction (SRR) at room temperature. The SRR between silver ions and TMH provides a simple and facile route to establish effective and stable heterostructures that can enhance the oxygen evolution reaction (OER) activity. Ag@Co(OH)_x grown on carbon cloth exhibits outstanding OER activity and durability, even superior to IrO₂ and many previously reported OER electrocatalysts. Experimental and theoretical analysis demonstrates that the strong electronic interaction between Ag and Co(OH)₂ activates the silver clusters as catalytically OER active sites, effectively optimizing the binding energies with reacted intermediates and facilitating the OER kinetics.     

Spontaneous Synthesis of Silver‐Nanoparticle‐Decorated Transition‐Metal Hydroxides for Enhanced Oxygen Evolution Reaction

The fabrication of metal‐supported hybrid structures with enhanced properties typically requires external energy input, such as pyrolysis, photolysis, and electrodeposition. In this study, silver‐nanoparticle‐decorated transition‐metal hydroxide (TMH) composites were synthesized by an approach based on a spontaneous redox reaction (SRR) at room temperature. The SRR between silver ions and TMH provides a simple and facile route to establish effective and stable heterostructures that can enhance the oxygen evolution reaction (OER) activity. Ag@Co(OH)_x grown on carbon cloth exhibits outstanding OER activity and durability, even superior to IrO₂ and many previously reported OER electrocatalysts. Experimental and theoretical analysis demonstrates that the strong electronic interaction between Ag and Co(OH)₂ activates the silver clusters as catalytically OER active sites, effectively optimizing the binding energies with reacted intermediates and facilitating the OER kinetics.     

Supercritical carbon dioxide in organometallic synthesis: Combination of sc-CO2 with Nafion film as a novel reagent in the synthesis of ethers from hydroxymethylmetallocenes

Metallocenyl carbinols FcCH₂OH (1a) and RcCH₂OH (1b) dissolved in sc-CO₂ penetrate into the acidic Nafion film under 20 MPa and 80 or 35 °C. After removal of pressure and leaving at room temperature, the crystals rapidly formed on the surface of the film, were identified as ethers McCH₂OCH₂Mc, Mc = Fc or Rc, by X-ray study. Mechanism of their formation is discussed.     

Perturbation approach for frequency shifts in IR spectra of molecular clusters

A second order perturbation approach for the evaluation of the splitting and shifting of the infrared vibrational bands of molecular clusters, based on early publications of Buckingham, is presented. The Hamiltonian of the system comprises harmonic- and anharmonic intramolecular vibration terms, as well as the intermolecular potential. The anharmonic contributions of the intramolecular force field and the intermolecular potential are treated as a perturbation. In order to extend the applicability of the approach to homogeneous molecular clusters, the formalism of degenerate perturbation theory is employed. The new approach is applied to methanol clusters from dimer to hexamer for calculating the frequency shifts of the OH stretching mode (ω₁=3681.5 cm^?1), the CH₃ rocking mode (ω₇=1074.5 cm^?1), and the CO stretching mode (ω₈=1033.5 cm^?1). The numerical results compare favourably with experimental and previous theoretical data (except for ω₁), but with a tendency to overestimate the shifts.     

An intermolecular perturbation approach to hydrogen bondings in systems in the ground and excited electronic states

The intermolecular interaction energy for binary systems in the ground and excited electronic states was partitioned into the Coulomb, exchange-repulsion, induction, dispersion and charge-transfer interaction terms by the perturbation expansion method. The various interaction terms were evaluated for the hydrogen bondings in (HF)₂, (H₂O)₂, (CH₃OH)₂, (RCOOH)₂, and HF·H₂O in various geometrical configurations. It has been found that the Coulombic interaction plays a dominant role in the stability of these hydrogen bonded systems. The method was further applied to the HCOOH·H₂O codimer in both the ground and excited singlet electronic states. The results were in accord with the well-known water solvent effects on the shifts of absorption spectral bands.     

Pd Loaded NiCo Hydroxides for Biomass Electrooxidation: Understanding the Synergistic Effect of Proton Deintercalation and Adsorption Kinetics

The key issue in the 5-hydroxymethylfurfural oxidation reaction (HMFOR) is to understand the synergistic mechanism involving the protons deintercalation of catalyst and the adsorption of the substrate. In this study, a Pd/NiCo catalyst was fabricated by modifying Pd clusters onto a Co-doped Ni(OH)₂ support, in which the introduction of Co induced lattice distortion and optimized the energy band structure of Ni sites, while the Pd clusters with an average size of 1.96 nm exhibited electronic interactions with NiCo support, resulting in electron transfer from Pd to Ni sites. The resulting Pd/NiCo exhibited low onset potential of 1.32 V and achieved a current density of 50 mA/cm² at only 1.38 V. Compared to unmodified Ni(OH)₂, the Pd/NiCo achieved an 8.3-fold increase in peak current density. DFT calculations and in situ XAFS revealed that the Co sites affected the conformation and band structure of neighboring Ni sites through CoO₆ octahedral distortion, reducing the proton deintercalation potential of Pd/NiCo and promoting the production of Ni³⁺−O active species accordingly. The involvement of Pd decreased the electronic transfer impedance, and thereby accelerated Ni³⁺−O formation. Moreover, the Pd clusters enhanced the adsorption of HMF through orbital hybridization, kinetically promoting the contact and reaction of HMF with Ni³⁺−O.     

A Stable Primary Phosphane Oxide and Its Heavier Congeners

(Ferrocenylmethyl)phosphane ( 1 ) oxidation with hydrogen peroxide, elemental sulfur and grey selenium produced (ferrocenylmethyl)phosphane oxide 1O , sulfide 1S and selenide 1Se , respectively, as the first isolable primary phosphane chalcogenides lacking steric protection. At elevated temperatures, compound 1O disproportionated into 1 and (ferrocenylmethyl)phosphinic acid. In reactions with [(η⁶-mes)RuCl₂]₂, 1O underwent tautomerization into a phosphane complex [(η⁶-mes)RuCl₂{FcCH₂PH(OH)-κP}], whereas 1S and 1Se lost their P-bound chalcogen atoms, giving rise to the phosphane complex [(η⁶-mes)RuCl₂(FcCH₂PH₂-κP)] (Fc=ferrocenyl, mes=mesitylene). No tautomerization was observed in the reaction of 1O with B(C₆F₅)₃, which instead produced a Lewis pair FcCH₂P(O)H₂-B(C₆F₅)₃. Phosphane oxide 1O added to C=O bonds of aldehydes and ketones and even to cumulenes PhNCE (E=O and S). However, both PH hydrogens were only employed in the reactions with aldehydes and cyanates.     

Time-Dependent Density Functional Theory Study on the Electronic Excited State of Hydrogen-Bonded Clusters Formed by 2-Hydroxybenzonitrile (<Emphasis Type="Italic">o</Emphasis>-Cyanophenol) and Carbon Monoxide

Time-dependent density functional theory (TDDFT) method has been carried out to investigate excited-state hydrogen-bonding dynamics between 2-hydroxybenzonitrile (o-cyanophenol) and carbon monoxide. We have demonstrated that intermolecular hydrogen bond between 2-hydroxybenzonitrile (o-cyanophenol) and C=O group are significantly strengthened in the electronically excited state by theoretically monitoring the changes of the bond lengths of hydrogen bonds and hydrogen-bonding groups in different electronic states. In this study, we firstly analyze frontier molecular orbitals (MOs). Our results are consistent with the intermolecular hydrogen bond strengthening in the electronically excited state of Coumarin 102 in alcoholic solvents, which has been demonstrated for the first time by Zhao and Han. Moreover, the calculated electronic excitation energies of the hydrogen bonding C=O and O–H groups are markedly red-shifted upon photoexcitation, which illustrates the hydrogen bonds strengthen in the electronically excited state again. And the geometric structures in both ground state and the S₁ state of this hydrogen-bonded complex are calculated using the density functional theory (DFT) and TDDFT methods, respectively.