New preorganized calix[4]arenes. Part II. Double Schiff-based calix[4]arenes derived from 4,6,10,12,16,18,22,24,25,26,27,28-dodecamethyl-5,11,17,23-tetrahydroxycalix[4]arene

We describe the condensation of an appropriate tetraaldehyde derivative of mesitol calix[4]arene with 1,n-diaminoalkanes to afford double Schiff-base calix[4]arene receptors in the 1,3-alternate conformation.     

Synthesis, characterization and electrochemical properties of two new calix[4]arene derivatives bearing two ferrocene imine or ferrocene amine units at the upper rim

A novel calix[4]arene derivative with two ferrocenyl Schiff-base groups at the upper rim 3 has been synthesized from 5,17-diformyl-25,27-dipropoxy-26,28-dihydroxy calix[4]arene and 4-ferrocenylaniline via condensation reaction. Reduction of 3 with sodium borohydride led to calix[4]arene derivative 4 with two amino ferrocenyl groups at the upper rim. The ferrocenyl Schiff-base calix[4]arene and its corresponding reduced amine have been purified and characterized by elemental analysis,¹H NMR, FTIR, Mass and UV-vis spectral data. Electrochemical properties of compounds 3 and 4 have been investigated. Cyclic voltammograms of 3 and 4 show reversible redox couples of ferrocene/ferrocinium at E_1/2=0.401 V and 0.346 V, respectively. Electrochemical studies show these redox active compounds electrochemically recognize trivalent lanthanides La³⁺ and Ce³⁺ and divalent Pb²⁺ and Cu²⁺cations. With ferrocenyl Schiff-base calix[4]arene 3 an anodic shift as large as 130 mV is observed on addition of one equivalent of Ce³⁺ ion. Also extraction properties of compound 4 towards some metal cations have been described. It has been observed that compound 4 has a good selectivity for metal cations Fe³⁺, Cu²⁺, Pb²⁺ and Cd²⁺ against Ni²⁺ and Co²⁺.     

AN EXCELLENT APPROACH TOWARDS THE DESIGNING OF A SCHIFF-BASE TYPE OLIGOCALIX[4]ARENE,SELECTIVE for THE TOXIC METAL IONS

ABSTRACT

A new Schiff-base type oligocalix[4]arene containing two nitrile ligating sites at narrow rim was synthesized via a simple condensation reaction through a wide rim of the calixarene moiety. The extraction ability of the oligomer with selected alkali and transition metals is compared with its monomeric analogous. It has been observed that the oligomer 6 is not selective as compared to its analogae 2 and 3, but shows a remarkable high affinity towards toxic metal cations such as Cu²⁺, Hg²⁺ and Pb²⁺.     

Isolation of ternary complex precursors and partially condensed␣intermediates to macrocyclic complexes of nickel(II) and copper(II)

Reaction in unheated solutions between metal salts, bis(3–aminopropyl)amine (dpt) and 2,6–diacetylpyridine (dap) gives the ternary complexes [M(dpt)(dap)]2+ (M=Ni or Cu), in which no Schiff-base condensation has occurred. Cyclisation requires long standing or heating. For tris(3–aminopropyl)amine and nickel(II), X-ray crystallography shows that reaction in MeOH can be stopped after condensation of one carbonyl and one amine group to give a coordinated open-chain hexadentate ligand, an intermediate in the formation of the fully condensed macrocycle. With the 2–(aminoethyl)-4–(butylamino)amine (ebt), the butylamine groups are involved in intermolecular condensation with carbonyl groups from adjacent units, giving oligomeric or polymeric complexes.     

Synthesis and crystal structure of a new dinuclear manganese(II) complex of a macrocyclic ligand with multi-ligating pendant-arms

A new dinuclear manganese(II) macrocyclic complex has been synthesized by [2 + 2] Schiff-base condensation between sodium 2,6-diformyl-4-chlorophenolate with the reduced 1:1 Schiff base of tris(2-aminoethyl)amine (tren) and 2-acetylpyridine in the presence of Mn(ClO₄)₂ · 6H₂O. The crystal structure shows that each pendant-arm is bonded in a bidentate fashion to the adjacent metal atom and that both arms are on the same side of the macrocycle. One manganese(II) ion is seven-coordinate with a geometry of a capped distorted octahedron, while another manganese(II) ion is six-coordinate with a geometry of a distorted octahedron.     

Homo dinuclear lanthanide(III) complexes of a mesogenic Schiff-base, N,N'-di-(4-decyloxysalicylidene)-1',6'-diaminohexane: synthesis and characterization

A mesogenic Schiff-base, N,N'-di-(4-decyloxysalicylidene)-1',6'-diaminohexane, H2ddsdh (abbreviated as H2L2) that exhibits smectic-B (SmB) mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H2L2, upon condensation with hydrated lanthanide(III) nitrates, yields LnIII complexes of the general composition [Ln2(L2H2)3(NO3)4](NO3)2, where Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L2H2) to the LnIII ions through two phenolate oxygens. The POM and DSC studies reveal that none of the LnIII complexes exhibits mesomorphism. Fluorescence studies show that the TbIII complex displays characteristic metal-centered fluorescence (solution state).     

New fluorenyl-substituted ditopic dioxotetraamine ligands and their copper(II) complexes--synthesis, crystal structure, magnetic properties and solution behavior

A new fluorenyl-substituted dioxotetraamine salicylaldehyde Schiff-base ligand (L1) has been synthesized by the non-template 1 + 2 condensation of ligand 6-(9-fluorenyl)-1,4,8,11-tetraazaundecane-5,7-dione (L) with salicylaldehyde. From reduction of L1 with an excess of NaBH4, a ditopic dioxotetraamine ligand (L2) has been obtained. The copper(II) complex of L1 has been synthesized and its properties were examined by ES-MS and variable-temperature magnetic susceptibility as well as its crystal structure being determined. Detailed studies have been made on solution chemistry of Cu(II) complex of L2 by pH-potentiometric and fluorometric titration.     

Acyclic or long-bond intermediate in the electron-transfer-catalyzed dimerization of 4-methoxystyrene

The electron-transfer-catalyzed dimerization of 4-methoxystyrene has long been a prototypical reaction for the study of radical cation reactivity. The different possible pathways were explored at the B3LYP/6-31G level of theory. Both [2 + 2] and [4 + 2] cycloadditions proceed via a stepwise pathway, diverging at an acyclic intermediate and interconnected by a vinylcyclobutane-type rearrangement. The experimentally observed stereoselectivity of the cycloaddition was traced to relatively high barriers for isomerization, while the previously described "long-bond" intermediate could not be located at the higher level of theory. CPCM calculations show that the highly exothermic [4 + 2] pathway becomes kinetically more favorable in condensed phase. Time-dependent density functional theory calculations indicate that the different possible intermediates have very similar absorption spectra, making the unambiguous assignment of the experimentally observed transient absorption of 500 nm to a given species difficult.     

Synthesis and Crystal Structure of Tri(4-(3-hydroxy2-ethyl-4-pyridinone-1-yl)-aniline Condensation Salicylaldehydato) Monohydratotricopper(II)Dimethylformamide Monohydrate Solvate

1 INTRODUCTION Synthesis of transition-metal complexes with Schiff-base has been a subject of considerable im- portance[1, 2]. These complexes are not only good coordination agents for Schiff-base, but also good bactericide and antitumour agent[3, 4]. A number of hydroxypyridinones are nontoxic compounds that have been applied in bioinorganic chemistry over many years[5], and their iron(III) complexes have been assessed for the amelioration of anaemia[6]. They have also been examined …     

Cobalt-mediated synthesis of angular [4]phenylene: structural characterization of a metallacyclopentadiene(alkyne) intermediate and its thermal and photochemical conversion

[reaction: see text] The first X-ray crystal structure of a mononuclear metallacyclopentadiene(alkyne) complex has been obtained. This type of metallacycle is believed to be the key intermediate in the cobalt-mediated [2 + 2 + 2]cycloaddition of alkynes. Thermal treatment leads to the generation of angular [4]phenylene, the X-ray structural details of which are described. Under photochemical conditions, the cobaltacycle isomerizes to a highly strained (cyclobutadieno)dibenzocyclooctatrienyne complex.     

系列新型硫杂杯[4]芳烃氮杂衍生物的合成

在对叔丁基硫杂杯[4]芳烃的下缘1,3位引入芳醛基, 合成了硫杂杯[4]二醛基衍生物2. 化合物2与苯胺、水杨酰肼、烟酰肼、异烟酰肼等通过席夫碱缩合反应得到新型硫杂杯[4]氮杂衍生物3a～3d, 产率分别为83%, 80%, 77%和79%. 化合物2与邻苯二胺、乙二酰肼、丙二酰肼、己二酰肼等通过“1＋1”分子间缩合得到新型1,3-桥联硫杂杯[4]氮杂衍生物4a～4d, 产率53%, 51%, 59%和66%. 新化合物的结构经IR, ¹H NMR, MS和元素分析等证实.     

三核铜配合物[Cu_3L_2](ClO_4)_2(H_2L=1,3-双（2-羟基-1-苯基-亚甲基）-丙烷)的合成与对pBR322DNA的切断作用

利用席夫碱配体[H_2L = 1，3-双（2-羟基-1-苯基-亚甲基）-丙烷]与铜盐作 用，得到了配合物[Cu_3L_2](ClO_4)_2，并用X射线单晶衍射测定了其晶体结构。 研究了该三核铜配合物与质粒pBR322 DNA之间的相互作用，琼脂糖凝胶电泳实验结 果表明该配合物能够将pBR322 DNA从超螺旋构型切割成开环型和线型。同时，紫外 光谱实验可以推测，配合物在对pBR322 DNA进行切断时，它们之间在一种插入作用 。     

Facile synthesis of selenium/sulfur-substituted 3-oxa-bicyclo[4.2.0]octa-1(8),5-diene and tetrahydro-1H-isochromene via sequential three-component conjugate addition/condensation/elimination/[2 + 2] or [4 + 2] cyclization reactions

An interesting sequential three-component reaction provides a facile synthesis of selenium/sulfur-substituted 3-oxabicyclo[4.2.0]octa-1(8),5-diene and tetrahydro-1H-isochromene from lithium alkylselenolates or alkylthiolates, 1-alkynylphosphine oxides, and aldehydes. The sequential reaction proceeds via a conjugate addition/condensation/elimination process to form the allene intermediate, which subsequently underwent [2 + 2] or [4 + 2] cyclization reaction to afford bicyclic frameworks.     

Synthesis and Properties of Double Calix[4]arene Derivatives Linked by Schiff-base in the Lower Rim

Calixarenesareregardedasthethirdgenerationofh0stmoleculesbecauseoftheirinclusionabilitytocati0ns,anionsandneutralmoleculesI'2.Duringthepastdecademosteff0rtshavebeentakenonthefunctionalizati0n0fcalixareness0thattheycanbeappliedn0tonlyastheionoph0resintheextractionprocess','andassensitivematerialsforionelectrodes"',butalsoastheenZymemimicscatalyzingthecleavageofphosphatediesters"'.Inordertoenablethemtoincludeandrecognizelargerchemicalspecies,manyappr0acheshavebeenusedtoc0nstructoIigo-calixarene…     

Heterobinuclear complexes as building blocks in designing extended structures

The heterobinuclear complex [CuPrL(NO(3))(3)] has been used as a building block for the construction of a two-dimensional coordination polymer with the formula [CuPrL(NO(3)(2)(IN)], 1 (L(2-) = the dianion of the compartmental Schiff-base ligand obtained from the 2:1 condensation of 3-methoxysalicylaldehyde with 1,3-propanediamine; IN(-) = the isonicotinate ion). The heterobinuclear units, [CuPrL(NO(3))(2)](+), are connected through the unsymmetrical exo-bidentate ligands, IN(-), leading to a unique extended structure. Crystal data for compound 1: FW, 790.94; monoclinic, space group P2(1)/n, a = 11.2837(3) A, b = 14.7785(4) A, c = 16.9745(4) A, beta = 100.427(1) degrees; V = 2783.86(12) A(3); Z = 4; R1 = 0.0210, wR2 = 0.0562 [I > 2sigma(I)].     

Directed assembly and reactivity of olefins within a one-dimensional ladder-like coordination polymer based on a dinuclear Zn(II) platform

A ladder-like coordination polymer involving a dinuclear Zn Schiff-base complex possesses organic linkers that undergo [2+2] photodimerisation in the solid state.     

Design and synthesis of binucleating macrocyclic clefts derived from Schiff-base calixpyrroles

The syntheses, characterisation and complexation reactions of a series of binucleating Schiff-base calixpyrrole macrocycles are described. The acid-templated [2+2] condensations between meso-disubstituted diformyldipyrromethanes and o-phenylenediamines generate the Schiff-base pyrrolic macrocycles H(4)L(1) to H(4)L(6) upon basic workup. The single-crystal X-ray structures of both H(4)L(3).2 EtOH and H(4)L(6).H2O confirm that [2+2] cyclisation has occurred, with either EtOH or H2O hydrogen-bonded within the macrocyclic cleft. A series of complexation reactions generate the dipalladium [Pd2(L)] (L=L(1) to L(5)), dinickel [Ni2(L(1))] and dicopper [Cu2(L)] (L=L(1) to L(3)) complexes. All of these complexes have been structurally characterised in the solid state and are found to adopt wedged structures that are enforced by the rigidity of the aryl backbone to give a cleft reminiscent of the structures of Pacman porphyrins. The binuclear nickel complexes [Ni2(mu-OMe)2Cl2(HOMe)2(H(4)L(1))] and [Ni2(mu-OH)2Cl2(HOMe)(H(4)L(5))] have also been prepared, although in these cases the solid-state structures show that the macrocyclic ligand remains protonated at the pyrrolic nitrogen atoms, and the Ni(II) cations are therefore co-ordinated by the imine nitrogen atoms only to give an open conformation for the complex. The dicopper complex [Cu2(L(3))] was crystallised in the presence of pyridine to form the adduct [Cu2(py)(L(3))], in which, in the solid state, the pyridine ligand is bound within the binuclear molecular cleft. Reaction between H(4)L(1) and [Mn(thf){N(SiMe(3))2}2] results in clean formation of the dimanganese complex [Mn2(L(1))], which, upon crystallisation, formed the mixed-valent complex [Mn2(mu-OH)(L(1))] in which the hydroxo ligand bridges the metal centres within the molecular cleft.     

Dimeric Calix[4]resorcinarene-based Porous Organic Cages for CO2/CH4 Separation

Investigating gas separation by emerging porous organic cage(POC) solids is still on its initial stage. In this work, two novel [2+4] organic cages with distinguished structures have been prepared based on the Schiff-based condensation reaction between tetraformyl-functionalized calix[4]resorcinarene building blocks and xylylenediamine(XDA) isomers. Specifically, the use of para-position XDA affords lantern-shaped cage(CPOC-105) with a medium cavity of ca. 0.526 nm³, while the meta-position produces peanut-shaped structure(CPOC-106) with two small cavities of ca. 0.181 nm³. Both CPOC-105 and CPOC-106 exhibit high selectivity capture of CO₂ over CH₄ with calculated selectivity coefficients of 4.5 and 3.1, respectively, under ambient conditions, and are capable of separating CO₂/CH₄ mixtures by fixed-bed column breakthrough experiments.     

Nickel(II) complexes of fully and partially condensed Schiff-base ligands derived from tris(3–aminopropyl)amine and acetylpyridine

In the presence of nickel(II), 2–acetylpyridine condenses with tris(3–aminopropyl)amine in absolute MeOH to give the fully condensed Schiff-base complex [Ni(tptpy3)]2+. Although the ligand is potentially heptadentate, the metal atom is effectively six-coordinate, interaction with the bridgehead nitrogen being rather weak. However, when aqueous MeOH is used, the condensation is limited to a single step, and a complex of the pentadentate mono-Schiff base adduct is formed, [Ni(tptpy)(H2O)]2+, which was characterised by X-ray diffraction of its PF6– salt.     

Imidotungsten(VI) complexes with chelating amino and imino phenolates

The reaction of WOCl(4) with 2,4-di-tert-butyl-6-((isopropylamino)methyl)phenol followed by the reaction with phenyl isocyanate leads to the formation of imidotungsten(VI) complex [W(NPh)Cl(3)(OC(6)H(3)(CH(2)NH-i-Pr)-2-t-Bu(2)-4,6)] 4 with a chelating aminophenolate ligand. When the same procedure was applied using aminophenols with bulkier substituents in the amino group, the final product was an unexpected Schiff-base complex [W(NPh)Cl(3)(OC(6)H(3)(CH=NPh)-2-t-Bu(2)-4,6)] 5, where the ligand is derived from 2,4-di-tert-butyl-6-((phenylimino)methyl)phenol. Complex 5 is also formed in the thermal degradation of 4. On the whole, 5 appears to be formed by a disproportionation of intermediate compounds, which are analogous to complex 4. The solid-state structures of 4 and 5 have been determined by X-ray crystallography whereas the solution structures were studied by (1)H and (13)C NMR.