Ferrocene derivatives with planar chirality and their enantioseparation by liquid-phase techniques

In the last decade, planar chiral ferrocenes have attracted a growing interest in several fields, particularly in asymmetric catalysis, medicinal chemistry, chiroptical spectroscopy and electrochemistry. In this frame, the access to pure or enriched enantiomers of planar chiral ferrocenes has become essential, relying on the availability of efficient asymmetric synthesis procedures and enantioseparation methods. Despite this, in enantioseparation science, these metallocenes were not comprehensively explored, and very few systematic analytical studies were reported in this field so far. On the other hand, enantioselective high-performance liquid chromatography has been frequently used by organic and organometallic chemists in order to measure the enantiomeric purity of planar chiral ferrocenes prepared by asymmetric synthesis. On these bases, this review aims to provide the reader with a comprehensive overview on the enantioseparation of planar chiral ferrocenes by discussing liquid-phase enantioseparation methods developed over time, integrating this main topic with the most relevant aspects of ferrocene chemistry. Thus, the main structural features of ferrocenes and the methods to model this class of metallocenes will be briefly summarized. In addition, planar chiral ferrocenes of applicative interest as well as the limits of asymmetric synthesis for the preparation of some classes of planar chiral ferrocenes will also be discussed with the aim to orient analytical scientists towards ‘hot topics’ and issues which are still open for accessing enantiomers of ferrocenes featured by planar chirality.     

Application of pyridylazo and thiazolylazo reagents in flow injection preconcentration systems for determination of metals

Pyridylazo and thiazolylazo reagents are synthetic dyes widely used in analytical chemistry. These reagents are also very attractive for use in preconcentration systems. This paper covers the application of pyridylazo and thiazolylazo reagents in flow injection systems for the determination of metals. The article discusses flow injection preconcentration systems with solid-phase extraction, precipitation and cloud point extraction. The use of pyridylazo and thiazolylazo reagents in flow injection detection systems is also presented. The relative advantages and drawbacks of these systems are discussed. The application of pyridylazo and thiazolylazo reagents in new systems is presented in the concluding part of this review article.     

Paper‐based Electrochemical Devices Coupled to External Graphene‐Cu Nanoparticles Modified Solid Electrode through Meniscus Configuration and their Use in Biological Analysis

This paper demonstrates, for the first time, the use of paper‐based electrochemical devices coupled to external solid working electrodes. The paper‐based electrochemical cells were fabricated using inexpensive and largely available office paper, according to a simple protocol that consists on the creation of hydrophobic barriers using paraffinized paper and preheated metal stamp. The counter and reference electrodes were integrated to the paper platform through the deposition of carbon and silver inks, respectively. The electrochemical paper analytical device (ePAD) was coupled to external glassy carbon rod electrode modified with reduced graphene oxide doped with Cu nanoparticles through meniscus configuration. The analytical usefulness of this electrochemical approach was demonstrated through the simultaneous determination of paracetamol and caffeine in biological samples. The analytes were successfully quantified in real urine samples and limits of detection of 24.6 nM (paracetamol) and 36.1 nM (caffeine) were obtained. The paper platform showed good stability (RSD of 1.07 % for the peak currents and 1.43 % for the peak potentials) and satisfactory performance. The use of solid electrodes coupled to paper electrochemical devices, firstly demonstrated here, opens new possibilities for the utilization of ePADs in electrochemistry and electroanalytical chemistry and offers advantages such as the extremely reduced consumption of reagents and the minimal generation of wastes.     

Synthesis and Molecular Structure of Bis-Ferrocene-Containing Acyl Thiourea Derivatives

Ferrocene is a compound with excellent stability. In addition, it has very favourable electrochemical properties. So the synthesis, structure, electrochemistry and coordination behaviors of ferrocene-derivatives have attracted considerable attention in recent years.[1,2] Electrondonating atoms such as N, S, O in the derivatives are known for their coordination particularly with transition metals. [3] Two new bis-ferrocene-containing acyl thiourea derivatives are synthesized. The derivatives are confirmed by IR spectrum, 1H NMR and elemental analysis. These compoundshave many electrondonating atoms and two ferrocenes. The structure of one compound is shown below. The study onelectrochemistry and coordination behaviors is in the progress.     

5-azo derivatives of rhodanine and its analogues in the analytical chemistry of the noble metals

Progress in the synthesis and theoretical study of the 5-azo derivatives of rhodanine, thiorhodanine, 3-aminorhodanine, thiohydantoin, pseudothiohydantoin, thiopropiorhodanine, and selenoisorhodanine is discussed. Emphasis is placed on peculiarities in the interaction of this series of reagents with noble metals and their practical application in analytical chemistry.     

Functionalized pentamethylferrocenes: Synthesis, structure, and electrochemistry

The advantageous properties of the Cp^* ligand — intensified electron donation, steric bulk, and enhanced solubility in comparison to the ubiquitous Cp ligand — are finding increasing use in organometallic chemistry. A systematic evaluation of synthetic routes to pentamethylferrocene compounds with a wide range of functionalities, including carboxyl, carbonyl, aminomethyl, vinyl, ethynyl, fulvenyl, cyclopentadienylmethyl, and others is reported. Spectroscopic, structural, and electrochemical properties of such functionalized pentamethylferrocenes Fc^*/2—R are compared to those of non-methylated ferrocenes Fc—R. The electronic influence of the Cp^* ligand in these unsymmetricalferrocenes Fc^*/2—R has been studied by cyclic voltammetry measurements, demonstrating a decrease in oxidation potential of −0.276 V in direct comparison to non-methylated ferrocenes Fc—R.     

Copper-catalyzed cross-coupling of imines, acid chlorides, and organostannanes: a multicomponent synthesis of alpha-substituted amides

A copper-catalyzed cross-coupling of organotin reagents with imines and acid chlorides is reported. The reaction proceeds efficiently with a range of vinyl-, alkyl-, aryl- and heteroaryl-substituted organostannanes as well as a diverse set of imines of non-enolizable aldehydes. Use of chloroformates also allows for the formation of N-protected alpha-substituted amines. This chemistry has been applied to the synthesis of isoquinoline alkaloid derivatives through the activation of cyclic imines.     

Homocyclic o-dicarboxaldehydes: Derivatization reagents for sensitive analysis of amino acids and related compounds by capillary and microchip electrophoresis

Amino acids are essential compounds for living organisms, and their determination in biological fluids is crucial for the clinical analysis and diagnosis of many diseases. However, the detection of most amino acids is hindered by the lack of a strong chromophore/fluorophore or electrochemically active group in their chemical structures. The highly sensitive determination of amino acids often requires derivatization. Capillary electrophoresis is a separation technique with excellent characteristics for the analysis of amino acids in biological fluids. Moreover, it offers the possibility of precapillary, on-capillary, or postcapillary derivatization. Each derivatization approach has specific demands in terms of the chemistry involved in the derivatization, which is discussed in this review. The family of homocyclic o-dicarboxaldehyde compounds, namely o-phthalaldehyde, naphthalene-2,3-dicarboxaldehyde, and anthracene-2,3-dicarboxaldehyde, are powerful derivatization reagents for the determination of amino acids and related compounds. In the presence of suitable nucleophiles they react with the primary amino group to form both fluorescent and electroactive derivatives. Moreover, the reaction rate enables all of the derivatization approaches mentioned above. This review focuses on articles that deal with using these reagents for the derivatization of amino acids and related compounds for ultraviolet-visible spectrometry, fluorescence, or electrochemical detection. Applications in capillary and microchip electrophoresis are summarized and discussed.     

Electrochemical functionalization of carbon surfaces by aromatic azide or alkyne molecules: a versatile platform for click chemistry

The electrochemical reduction of phenylazide or phenylacetylene diazonium salts leads to the grafting of azido or ethynyl groups onto the surface of carbon electrodes. In the presence of copper(I) catalyst, these azide- or alkyne-modified surfaces react efficiently and rapidly with compounds bearing an acetylene or azide function, thus forming a covalent 1,2,3-triazole linkage by means of click chemistry. This was illustrated with the surface coupling of ferrocenes functionalized with an ethynyl or azido group and the biomolecule biotin terminated by an acetylene group.     

Derivatization in mass spectrometry-3. Alkylation (arylation)

The review is devoted to alkylation (arylation) as a widely employed derivatization procedure for the protection of OH (carboxylic acids, phosphoric acids, sulfonic acids, alcohols, polyols, phenols, enols), SH (thiols) and NH (amines, amides) groups in order to increase volatility, to improve the chromatographic properties and, if possible, mass spectral properties of derivatives. Chemical aspects of derivatization and various alkylation (arylation) reagents and reaction procedures are described. Specific mass spectral (electron ionization, chemical ionization) features of derivatives helpful in identification, structure elucidation, profiling and quantitative determination of the above-mentioned polar compounds by coupled gas chromatography or high-performance liquid chromatography are discussed. Some common analytical applications of the procedures in organic chemistry, clinical chemistry, environmental chemistry etc. are briefly summarized.     

Green analytical chemistry: Opportunities for pharmaceutical quality control

This review article summarizes the opportunities for utilizing the green analytical chemistry (GAC) techniques and principles in the field of quality control (QC) of pharmaceuticals. Green analytical chemistry is considered a branch of the green chemistry based on the principles overlapping with the goals of sustainable development. General definitions of quality and quality control, the principles of GAC, proposals for greener sample pretreatment and greener chromatographic method of analysis applied in QC laboratories are discussed herein. The main goal is to achieve more eco-friendly analysis in QC laboratories through different strategies and techniques, replace toxic reagents, and modify or replace analytical methods and/or techniques with safer ones, making it possible to dramatically reduce the amounts of reagents consumed and waste generated.     

基于核酸分子识别的电化学分析方法与应用

核酸作为生物体遗传信息的载体以及分子生物学和生物分析化学中重要的功能分子,近年来在电化学分析中受到了越来越多的重视。本文以作者所在研究组的工作为实例,对核酸分子识别的电化学分析方法作出简要的评述,内容涉及核酸序列和基因变异的电化学分析以及核酸作为功能分子进行识别检测的电化学分析等等。     

A comparative study of several HPLC methods for determining free amino acid profiles in honey

A study of the viability of three derivatizing reagents for obtaining amino acid profiles in honey through high performance liquid chromatography (HPLC) is presented. A method using diode array detection based on a reaction with diethyl ethoxymethylene malonate (DEMM) and two other methods using fluorescence detection based on derivatization with fluorenylmethyl chloroformate (FMOC-Cl) and 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) have been developed. The three methods yield detection limits close to the ppb level, but vary in relation to other analytical characteristics. The use of methyl chloroformate derivatives allows the profile to be obtained with the greatest sensitivity within a short time frame. On applying such methods to honey samples of diverse botanical origin, we observe that the proline values obtained are always lower than those found using the official spectrophotometric method, thereby underlining the advisability of using HPLC methods to reduce uncertainty in these results.     

有机高价碘化学简介及其应用

近几十年来,有机高价碘化学蓬勃发展,有机高价碘试剂也受到化学合成工作者的广泛关注,关于有机高价碘试剂的反应性研究也获得了迅猛发展。有机高价碘试剂作为绿色、高效、多功能化的氧化剂,通常容易制备且操作简单,与已有的合成方法相比,该类试剂参与的反应表现出了许多独特的优点,并且具有与汞、铬、铅、铊等重金属试剂类似的反应性,但却没有这些试剂所带来的毒性和环境污染问题。本文介绍了有机高价碘化学的起源与发展,高价碘试剂的结构特点与分类,高价碘试剂在有机合成、材料化学及工业合成中的应用。     

Synthesis of chiral,non-racemic ferrocene derivatives by ortho-metallation and partial reductive removal of ortho-directing amino groups

Chiral, non-racemic 1,2-disubstituted ferrocenes have been prepared from monosubstituted ferrocene derivatives by amine-mediated ortho-directed reactions and subsequent partial reductive removal of the stereogenic ortho-directing group. It was found that the ortho-directing amino group of 2-substituted derivatives of N,N-dimethylaminoethyl-ferrocene and similar compounds can, after quaternisation with methyl iodide, be reductively removed with sodium borohydride to give 2-substituted methyl- or ethylferrocenes. In most cases the substituents I, Br, COOEt, P(O)Ph₂ and CN tolerate the reaction conditions used. In addition, a few examples are reported that show how the use of LiTMP allows 2-bromo- and especially 2-cyano-substituted derivatives to be further ortho-lithiated and reacted to give 1,2,3-trisubstituted ferrocenes.     

量子化学在分析试剂反应性能中的应用

本文对量子化学方法应用于分析化学的有机显色反应能作一综述，重点从量子化学在生色理论，在试剂络合性能研究中，在试剂质子化及其酸碱平衡和存在形成研究中以及在取代基效应的中的应用四个方面进行了论述，重点介绍我国在这一方面的工作。认为用量子化学方法预测试剂和络合物的某些性质成为可能。参考文献６０篇。     

Derivatization for electrospray ionization-mass spectrometry. 4. Alkenes and alkynes

A survey of derivatization strategies and prospective derivatization reactions for conversion of simple alkenes and alkynes to 'electrospray-active' species is presented. General synthetic strategies are discussed and illustrative examples of prospective derivatives prepared from model compounds are presented along with their electrospray ionization (ES) mass spectra. The identified derivatives of these neutral, nonpolar analytes are either ionic or are ionizable in solution through Bronsted acid/base chemistry, by Lewis acid/base chemistry, or by chemical or electrochemical electron-transfer chemistry. Once ionized, the derivatives are expected to be amenable to detection by electrospray ionization-mass spectrometry. Derivatives are identified for positive and negative ion analysis of both alkenes and alkynes. Copyright 2000 John Wiley & Sons, Ltd.     

Recent Advance in the Electrochemical Detection of Sulphide and Sulphhydryl Species

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A Rapid HPLC Determination of C2–C7 Aliphatic Diamines by Precolumn Derivatization with Acetylacetone in Methanol-Water

A rapid reversed-phase high performance liquid chromatographic analysis for the determination of seven aliphatic diamines in water is described. Precolumn derivatization with acetylacetone is used for traces of aliphatic diamines in water-methanol (10:1 v/v) medium. The acetylacetone derivatives obtained after 15 min were extracted with an octadecylsilane functionalized silica cartridge, and then injected into the HPLC system. The HPLC system consisted of a reversed-phase column, and a spectrophotometric detector adjusted to 310 nm as elution solvent a methanol-tetrahydrofuran-water (55:3:42 v/v) mixture was used. The acetylacetone derivatives of the C2-C7 diamines were separated with a good resolution in 23 min. The detection limits achieved for each diamine were between 0.18-0.72 ng/ml for a 100 ml water sample. The recovery of diamine derivatives from river and seawater was 88-101%, with relative standard deviations of 2.2-4.0%, and 82-93%, with relative standard deviations of 2.8-4.6%, respectively. Aliphatic diamines are widely used as chemical reagents, occur as metabolic in biomedical studies and are used as chelating agents in analytical chemistry. As they are soluble in water, their use results in their ultimate release to the environment. The need for a sensitive, selective and rapid determination of aliphatic diamines in environmental samples thus has become important. Dobberpuhl et al. [1] have described a highly sensitive pulsed electrochemical detection for aliphatic monoamines and diamines following their chromatographic separation. Although, it is a sensitive method the determination has to be carried out in alkaline conditions. The most common method for the determination of aliphatic amines is high performance liquid chromatography (HPLC), using different derivatives with either fluorescence [2-5] or UV-visible detection [6-11]. The fluorescence detection method most often relies on post-column derivatization, which requires a second pump to deliver the reagent. Acetylacetone is soluble to some degree in water, and has been used as a pre-column derivatization reagent [12]. The reaction only is effective with diamines, and results in UV-active acetylacetone derivatives known as Schiff bases. But acetylacetone requires a long reaction time in water, which makes it rather unsuitable for routine analysis. In this paper an optimized reversed-phase HPLC determination procedure for C2-C7 aliphatic diamines at low ng/ml levels in water is described.     

Some unique properties of gas chromatography coupled with atomic-emission detection

The atomic-emission detector in gas chromatography is enormously versatile in applications in analytical chemistry. Its unique properties of high selectivity for most elements and low limits of detection combine to make it the preferred detector for many analytical problems. In this review the stress is laid on the possibility of using it for compound-independent calibration, for determination of the empirical formula of an unknown analyte, for isotope-selective detection, and on derivatization to give AED-active derivatives with advantageous detection properties. Both metals and non-metals are considered and examples of the use of atomic emission detection in real-world analysis are discussed.