Interaction of copper(II) and palladium(II) with linked 2,2′-dipyridylamine derivatives: Synthetic and structural studies

Interaction of copper(II) salts with 2,2′-dipyridylamine (1), N-cyclohexylmethyl-2,2′-dipyridylamine (2), di-2-pyridylaminomethylbenzene (3), 1,2-bis(di-2-pyridylaminomethyl)-benzene (4), 1,3-bis(di-2-pyridylaminomethyl)benzene (5), 1,4-bis(di-2-pyridylaminomethyl)benzene (6), 1,3,5-tris(di-2-pyridylaminomethyl)benzene (7) and 1,2,4,5-tetrakis(di-2-pyridylaminomethyl)benzene (8) has yielded the following complexes: [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · H₂O, [Cu₂(4)(NO₃)₄], [Cu₂(5)(NO₃)₄] · 2CH₃OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Cu₄(8)](NO₃)₄] · 4H₂O while complexation of palladium(II) with 1, 4, 5 and 6 gave [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)Cl₄], [Pd₂(4)(OAc)₄], [Pd₂(5)Cl₄], [Pd₂(6)Cl₄] and [Pd₂(6)(OAc)₄] · CH₂Cl₂, respectively. X-ray structures of [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · 2C₂H₅OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂ are reported. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a diverse range of coordination geometries and lattice arrangements, with the structures of [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂, incorporating the isomeric ligands 4 and 6, showing some common features. Liquid–liquid (H₂O/CHCl₃) extraction experiments involving copper(II) and 1–3, 5, 7and 8 show that the degree of extraction depends markedly on the number of dpa-subunits (and concomitant lipophilicity) of the ligand employed with the tetrakis-dpa derivative 8 acting as the most efficient extractant of the six ligand systems investigated.     

Neutral (bis-beta-diketonato) iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) metallocycles: structural, electrochemical and solvent extraction studies

Neutral dimeric metallocyclic complexes of type [M(2)(L(1))(2)B(n)] (where M = cobalt(II), nickel(II) and zinc(II), L(1) is the doubly deprotonated form of a 1,3-aryl linked bis-beta-diketone ligand of type 1,3-bis(RC(O)CH(2)C(O))C(6)H(4) (R=Me, n-Pr, t-Bu) and B is pyridine (Py) or 4-ethylpyridine (EtPy)) have been synthesised, adding to similar complexes already reported for copper(II). New lipophilic ligand derivatives with R = octyl or nonyl were also prepared for use in solvent extraction experiments. Structural, electrochemical and solvent extraction investigations of selected metal complex systems from the above series are reported, with the X-ray structures of [Co(2)(L(1))(2)(Py)(4)] x 2.25CHCl(3) x 0.5H(2)O (R=Pr), [Co(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Ni(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Zn(2)(L(1))(2)(EtPy)(2)] (R=Me) and [Zn(2)(L(1))(2)(EtPy)(4)] (R=t-Bu) being presented. The electrochemistry of H(2)L(1) (R=t-Bu) and of [Fe(2)(L(1))(3)], [Co(2)(L(1))(2)(Py)(4)], [Ni(2)(L(1))(2)(Py)(4)], [Cu(2)(L(1))(2)] and [Zn(2)(L(1))(2)(Py)(2)] has been examined. Oxidative processes for the complexes are dominantly irreversible, but several examples of quasireversible behaviour were observed and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as a metal-centred oxidation. The reduction processes for the respective metal complexes are not simple, and irreversible in most cases. Solvent extraction studies (water/chloroform) involving variable concentrations of metal, bis-beta-diketone and heterocyclic base have been performed for cobalt(II) and zinc(II) using a radiotracer technique to probe the stoichiometries of the extracted species in each case. Synergism was observed when 4-ethylpyridine was added to the bis-beta-diketone ligand in the chloroform phase. Competitive extraction studies show a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).     

Anion recognition and sensing with Zn(II)-dipicolylamine complexes

This critical review covers the developments in anion recognition and sensing using Zn(II)-dipicolylamine functionalized receptors over the past decade with emphasis on recent rapid advances in the last five years.     

Synthesis of a family of cyclic peptide-based anion receptors

We report here the design and synthesis of a family of novel backbone modified cyclic peptides, bearing dipicolylamine side chains for metal complexation and subsequent anion binding studies. Two approaches to the cyclic peptides were investigated. Initially, a stepwise approach was employed, involving solid-phase assembly of oxazole-based building blocks, followed by solution-phase macrolactamisation of the resulting linear precursor. The alternative strategy involved the formation of linear bisoxazole fragments in solution-phase, followed by a cyclodimerisation reaction. The zinc(II) complexes of these receptors bind selectively to di- and tri-phosphate ions over hydrogenphosphate.     

Practical and Scalable Kinetic Resolution of BINOLs Mediated by a Chiral Counterion

BINOLs are valuable and widely used building blocks, chiral ligands, and catalysts that are effective across a remarkable range of different chemical transformations. Here we demonstrate that an ammonium salt catalyzed kinetic resolution of racemic BINOLs with benzyl tosylate proceeds with s up to 46. This is a scalable and practical process that can be applied across >30 different C₂‐ and non‐C₂‐symmetric BINOLs. Implementation of this method enables the enantioselective synthesis of a wide range of BINOL derivatives with over 99:1 e.r.     

Characterization of peptide immobilization on an acetylene terminated surface via click chemistry

Peptide (A-A-A-A-G-G-G-E-R-G-D)¹ conjugated surfaces were prepared on silicon surfaces through click chemistry. The amino acid sequence RGD is the cellular attachment site of a large number of extracellular matrices such as blood and cell surface proteins. Recent research has focused on developing RGD peptides which mimic cell adhesion proteins and integrins [1], [2].The steps involved the formation of an alkyne-terminated monolayer on Si(111), followed by linking the peptide to 4-azidophenyl isothiocyanate via a specific and gentle reaction. This was followed by the attachment of the azido peptide to the surface-bound alkynes using the Cu (I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The surface structures of the alkyne terminated monolayer and the attached peptide were characterized using high resolution impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (ATR-FTIR) Spectroscopy. EIS characterization revealed the alkyne layer and the hydrophobic and polar regions of the attached peptide. XPS analysis showed a high surface coverage of the peptide on the silicon substrates and this was confirmed by FTIR.Our results confirmed a specific covalent attachment of the peptide on the silicon surfaces. This approach offers a versatile, experimentally simple, method for the specific attachment of peptide ligands. This approach would have applications for cell attachment and biosensors.     

漫谈有效数字和计算器

介绍了有效数字的概念及其计算规则,介绍了计算器的一般特性及使用技巧,并给出计算实例.     

速度算符和电子的颤动

指出了国外某些量子力学教材中关于速度算符的概念错误和相对论自由电子进行颤动的错误,分析了错误的原因.