Impact of Single Basepair Mismatches on Electron‐Transfer Processes at Fc‐PNA⋅DNA Modified Gold Surfaces

Gold‐surface grafted peptide nucleic acid (PNA) strands, which carry a redox‐active ferrocene tag, present unique tools to electrochemically investigate their mechanical bending elasticity based on the kinetics of electron‐transfer (ET) processes. A comparative study of the mechanical bending properties and the thermodynamic stability of a series of 12‐mer Fc‐PNA?DNA duplexes was carried out. A single basepair mismatch was integrated at all possible strand positions to provide nanoscopic insights into the physicochemical changes provoked by the presence of a single basepair mismatch with regard to its position within the strand. The ET processes at single mismatch Fc‐PNA?DNA modified surfaces were found to proceed with increasing diffusion limitation and decreasing standard ET rate constants k⁰ when the single basepair mismatch was dislocated along the strand towards its free‐dangling Fc‐modified end. The observed ET characteristics are considered to be due to a punctual increase in the strand elasticity at the mismatch position. The kinetic mismatch discrimination with respect to the fully‐complementary duplex presents a basis for an electrochemical DNA sensing strategy based on the Fc‐PNA?DNA bending dynamics for loosely packed monolayers. In a general sense, the strand elasticity presents a further physicochemical property which is affected by a single basepair mismatch which may possibly be used as a basis for future DNA sensing concepts for the specific detection of single basepair mismatches.     

Stereochemical analysis of ferrocene and the uncertainty of fluorescence XAFS data

Methods for the quantification of statistically valid measures of the uncertainties associated with X‐ray absorption fine structure (XAFS) data obtained from dilute solutions using fluorescence measurements are developed. Experimental data obtained from 10 mM solutions of the organometallic compound ferrocene, Fe(C₅H₅)₂, are analysed within this framework and, following correction for various electronic and geometrical factors, give robust estimates of the standard errors of the individual measurements. The reliability of the refinement statistics of standard current XAFS structure approaches that do not include propagation of experimental uncertainties to assess subtle structural distortions is assessed in terms of refinements obtained for the staggered and eclipsed conformations of the C₅H₅ rings of ferrocene. Standard approaches (XFIT, IFEFFIT) give refinement statistics that appear to show strong, but opposite, preferences for the different conformations. Incorporation of experimental uncertainties into an IFEFFIT‐like analysis yield refinement statistics for the staggered and eclipsed forms of ferrocene which show a far more realistic preference for the eclipsed form which accurately reflects the reliability of the analysis. Moreover, the more strongly founded estimates of the refined parameter uncertainties allow more direct comparison with those obtained by other techniques. These XAFS‐based estimates of the bond distances have accuracies comparable with those obtained using single‐crystal diffraction techniques and are superior in terms of their use in comparisons of experimental and computed structures.     

An Alternative Preparation of 1-(N,N-Dimethylaminomethyl)-1′-(diphenylphosphanyl)ferrocene: Synthesis and Structural Characterization of AuI and PdII Complexes with this Hybrid Ligand

1-(N,N-Dimethylaminomethyl)-1′-(diphenylphosphanyl)ferrocene (1) was synthesized in good yield by lithiation of 1-bromo-1′-(diphenylphosphanyl)ferrocene and subsequent reaction with Eschenmoser''s salt (dimethylmethylideneammonium iodide). Making use of an easily accessible, nontoxic starting material, this procedure represents a convenient alternative to the original synthetic protocol based on stepwise lithiation/functionalization of 1,1′-bis(tributylstannyl)ferrocene and reductive amination [M. E. Wright, Organometallics 1990, 9, 853–856]. Compound 1 has typical hybrid-donor properties. When reacted with [AuCl(tht)] (tht=tetrahydrothiophene), it afforded the expected Au^I phosphane complex [AuCl(1-κP)] (2). An attempted removal of the chloride ligand from 2 with AgClO₄ produced an ill-defined material formulated as Au(1)ClO₄. The uncoordinated amine substituent reacted with traces of hydrogen chloride formed by slow decomposition typically occurring in solution. In this manner, complexes [AuCl(Ph₂PfcCH₂NHMe₂)]Cl (3, fc=ferrocene-1,1′-diyl) and [AuCl(Ph₂PfcCH₂NHMe₂)]ClO₄ (4) were isolated from crystallizations experiments with 2 and Au(1)ClO₄, respectively. On a larger scale, complex 3 was prepared easily from 2 and hydrogen chloride. The course of reactions between [PdCl₂(cod)] (cod=cycloocta-1,5-diene) and 1 were found to depend on the ligand-to-metal ratio. Whereas the reaction with two equivalents of 1 afforded bis(phosphane) complex trans-[PdCl₂(1-κP)₂] (5), that of a Pd:P ratio 1:1 produced ligand-bridged dimer [(μ-1)PdCl₂]₂ (6). With hydrogen chloride, complex 6 reacted to afford zwitterionic complex [PdCl₃(1H-κP)] (7), which was also formed when ligand 1 and [PdCl₂(cod)] were allowed to react slowly by liquid-phase diffusion of their chloroform solutions. The compounds were characterized by spectroscopic methods (multinuclear NMR and ESI–MS), and the molecular structures of complex 2–4, 6⋅2CHCl₃ and 7⋅1.5CHCl₃ were determined by single-crystal X-ray diffraction analysis.     

Sensitive and Selective Determination of Phenylhydrazine in the Presence of Hydrazine at a Ferrocene Monocarboxylic Acid Modified Carbon Nanotube Paste Electrode

In the present paper, the use of a carbon paste electrode modified by ferrocene monocarboxylic acid (FMC) and carbon nanotubes prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of phenylhydrazine (PHZ) and hydrazine (HZ) with a 300 mV separation of both peaks. Differential pulse voltammetric peak currents of PHZ and HZ increased linearly with their concentrations at the range of 0.8 µM to 700 µM and 16 µM to 800 µM and the detection limits (3σ) were determined to be 0.42 µM and 14 µM, respectively.     

Theoretical study on the one‐, two‐, and three‐photon absorption properties of exohedral functionalized derivative of Sc3N@C80

Geometrical structures of three investigated molecules Sc₃N@C₈₀, Sc₃N@C₈₀‐Fc, and C₆₀‐Fc were optimized by density functional theory (DFT) at the B3LYP/6‐31G* level. Then the time‐dependent DFT was employed to investigate the excited states of these molecules. After exohedral functionalization by ferrocene (Fc‐) group as the electron donor or replacing C₆₀ with Sc₃N@C₈₀ as the electron acceptor, the wavelengths of the first one‐photon absorption peak and the strongest two‐photon absorption (2PA) and three‐photon absorption (3PA) peaks shift red. The corresponding cross sections of Sc₃N@C₈₀‐Fc in the 2PA and 3PA processes increase as compared with those of Sc₃N@C₈₀, which originate from the contributions of charge transfers from Fc‐ group to C₈₀ cage and simultaneously the transfers from the C₈₀ cage to the encapsulated Sc₃N cluster. When compared with C₆₀‐Fc, the 2PA and 3PA cross sections of Sc₃N@C₈₀‐Fc decrease, which may result from the more negative charge surface of C₈₀ cage in Sc₃N@C₈₀‐Fc molecule which blocks the charge transfers from Fc‐ moiety to the C₈₀ cage in the excitation processes by compared with C₆₀‐Fc. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

含二茂铁基树形两亲性分子的合成及其电化学行为

合成了2, 3, 4-三-（11-二茂铁基）十一烷氧基苯甲酸, 用元素分析、核磁共振谱, 红外及紫外光谱等对产物进行了表征. 利用循环伏安法（CV）, 线性扫描伏安法（LSV）, 常规脉冲伏安法（NPV）, 计时电流法（CA）和计时电量法（CC）研究了该物质的电化学行为, 测定了其电化学参数. 结果表明该二茂铁基两亲性分子在溶液中具有良好的氧化还原可逆性, 是由扩散控制的可逆过程, 且三个二茂铁基团之间没有强相互作用而显示等同的氧化还原性.     

Fast and convenient construction of carbamate/urea‐based dendrimers with a diisocyanate building block

A novel, fast, and simple synthetic procedure for polycarbamate/urea dendrimers, based on an AB–CD₂ coupling strategy, is presented. The reactivity difference of the two isocyanate functionalities of the AB building block allows the construction of these dendrimers without the necessity of activation or deprotection steps. This makes it possible to construct dendrimers within 2–3 days, even the largest dendrimers. The resulting dendrimers could be fully characterized by ¹³C NMR, IR spectroscopy, and mass spectrometry. The synthetic strategy necessitates only techniques such as stirring, heating, and accurate dosing, and there is no workup required for the purification of the compounds. On account of a wide variety of polyols, amines, and aminoalcohols, this new procedure is not limited to the synthetic strategy followed but allows the incorporation of a large variety of functional molecules in the core, in the branching units, or at the end groups. The method is even applicable when organometallic species are incorporated into the dendritic structure, thereby showing its versatility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3112–3120, 2001     

手性二茂铁聚酰胺催化剂的合成及应用

以二茂铁为原料,经酰化、氧化和酰氯反应得到二茂铁二酰氯继而与手性二氨作用合成未见文献报道的三种新的手性二茂铁聚酰氨配体。其Ｒｈ（Ｉ）配合物催化苯乙酮的不对称氢转移化应应得到高的转化率,ｅ．ｅ．值１６．５％。新化合物的结构通过元素分析,核磁共振及红外光谱得到确证。     

3,5-Bis(ferrocenylmethylene)-1-methyl-4-methylenepiperidine. Synthesis and some chemical properties

3,5-Bis(ferrocenylmethylene)-1-methyl-4-methylenepiperidine, a diferrocenyltriene with a fixeds-cisoid conformation of the exocyclic double bonds, was synthesized. On heating, this compound cyclodimerizes according to the [4+2]-cycloaddition scheme; it forms Diels-Alder adducts with azodicarboxylic and maleic acidN-phenylimides. The compound easily cyclodimerizes in the presence of acids by a proton cyclodimerization mechanism to give a spiro cyclodimer. The triene also adds a 3,5-bis(ferrocenylmethylene)-1,4-dimethyl-1-azonia-4-cyclohexyl salt to the terminal methylene group yielding linear and cyclic addition products. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 511–516, March, 2000.     

铕-二茂铁衍生物配合物修饰电极的电化学行为

研究了影响铕 二茂铁衍生物配合物薄膜修饰电极伏安性质的各种因素 ,讨论了薄膜电极的电荷传递过程。在LiClO4 和甘氨酸底液中 ,在 0～ 0 8V(vs.SCE)电位范围内可观察到修饰电极的氧化还原峰 ,薄膜修饰电极在底液中是一种薄层扩散过程 ,用计时库仑法测得其表观扩散系数为 2 1× 1 0 - 10 cm2 ·s- 1。溶液平衡离子的水合半径大小、离子强度、溶剂对薄膜的溶胀性质以及薄膜的厚度是影响薄膜修饰电极伏安性质的主要因素。同时测定了电极反应的表观速率常数ks 为 6 7× 1 0 - 1s- 1。