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Macrocycles
Kinds of Macrocycles Selected AbstractsLithiation of a Cyclen-Derived (NNNN) Macrocycle and Its Reaction with n -ButyllithiumEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2010Sabine Standfuss Abstract Cyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, (Me3TACD)H (1), was metalated with n -butyllithium in pentane to give [Li2(Me3TACD)2] (2). The structure of this compound is dimeric in the solid state as shown by single-crystal X-ray diffraction. With an excess of nBuLi, nBuLi is incorporated into the product. Depending on the stoichiometry, the compounds [Li3(nBu)(Me3TACD)2] (3) or [Li4(nBu)2(Me3TACD)2] (4) are formed. As shown by single-crystal X-ray diffraction, both molecular structures show a ladder motif. (Me3TACD)H reacted with NaI/Na2CO3 in acetonitrile to give benzene-soluble [NaI(Me3TACD)H] (5). [source] Synthesis of Fullerene-Stoppered Rotaxanes Bearing Ferrocene Groups on the Macrocycle,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2010Aurelio Mateo-Alonso Abstract The synthesis, characterisation and behaviour of a series of rotaxanes containing a fulleropyrrolidine stopper and two ferrocene moieties on the macrocycle is reported. Remarkably, the presence of large and bulky ferrocene groups does not interfere either in the synthesis or in the translocation of the macrocycle induced by ,,, interactions between the macrocycle and the fullerene. The synthetic routes developed can also be applied to the preparation of rotaxane scaffolds that can be complexed to [Ru(CO)TPP] by axial coordination. Overall, the synthetic routes presented herein provide an efficient way to prepare a variety of rotaxanes and molecular shuttles with potential applications in different fields. [source] A Porphyrin-Related Macrocycle with an Embedded 1,10-Phenanthroline Moiety: Fluorescent Magnesium(II) Ion Sensor,ANGEWANDTE CHEMIE, Issue 1 2010Masatoshi Ishida Exklusiver Gast: Ein neuartiger, porphyrinähnlicher Makrocyclus konnte durch den Austausch der Dipyrromethen- gegen eine 1,10-Phenanthrolin-Einheit erhalten werden. Dieser Makrocyclus ermöglicht die hochselektive Komplexierung und Fluoreszenzdetektion von Mg2+ in Gegenwart anderer physiologisch relevanter Metallionen wie Na+, K+ und Ca2+ und eignet sich gut als Fluoreszenzsensor für Mg2+, selbst in HEPES-gepufferter H2O/DMSO-Lösung (pH,7.4). [source] ChemInform Abstract: Partial Substitution of Hydroxyl by Azide: An Unprecedented 2D Azido,Copper,Hydroxyl Compound with a [Cu24] Macrocycle in the Presence of [Cu(H2O)6]2+.CHEMINFORM, Issue 44 2008Yong-Fei Zeng Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis and Study of a New Diamidodipyrromethane Macrocycle.CHEMINFORM, Issue 43 2004An Anion Receptor with a High Sulfate-to-Nitrate Binding Selectivity. No abstract is available for this article. [source] Synthetic Studies on Ecteinascidin 743: Rapid Access to the Fully Functionalized Tetrahydroisoquinoline with a Bridged 10-Membered Sulfur Containing Macrocycle.CHEMINFORM, Issue 13 2004Michael De Paolis Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Crown Ethers with Azo or Azoxy Unit and Sulfur Atom(s) in 16-Membered Macrocycle.CHEMINFORM, Issue 44 2001J. Szczygelska-Tao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] An Anthracene-Based Photochromic Macrocycle as a Key Ring Component To Switch a Frequency of Threading MotionCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2008Keiji Hirose Dr. Abstract A concept and demonstration of a switching in frequencies of molecular motions are described using a pseudorotaxane system. The setup consists of dibenzylammonium hexafluorophosphate and a photochromic dianthrylethane-based [24]crown-8-type macrocycle, which we designed as a key ring component for the pseudorotaxane system having photocontrollable threading functionality by changing the size of ring component due to the action of light. [source] Novel Enantioselective Receptors for N-Protected Glutamate and AspartateCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2005Andrea Ragusa Abstract A series of chiral bisthiourea macrocycles 1,4 have been prepared and their binding properties with various dicarboxylate salts have been examined by using NMR titration and isothermal calorimetry experiments. Macrocycle 1, in particular, favours the 1:1 binding of N-protected L -glutamate and aspartate, but favours 1:2 binding of the corresponding D -amino acids in polar solvents (dimethyl sulfoxide and acetonitrile). The macrocycles, however, do not bind carboxylates at all in the less competitive solvent chloroform. The binding properties of these macrocyles are sensitive to small structural changes as demonstrated by the altered binding properties of macrocycles 2,4 compared with 1. [source] Superior Anion-Binding Properties of a Cryptand-like Oligopyrrolic MacrocycleCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2010Seong-Jin Hong Recognition by strapped system: Cryptand-type calix[4]pyrrole are shown to exhibit a highly enhanced affinity towards anionic guests as compared to other reported calix[4]pyrroles (see figure). The results obtained provide some insights as to how calix[4]pyrrole-based anion receptors may be designed to achieve higher affinity and selectivity. [source] Voltammetric Detection of Lead(II) Using Amide-Cyclam- Functionalized Silica-Modified Carbon Paste ElectrodesELECTROANALYSIS, Issue 15 2009Stéphanie Goubert-Renaudin Abstract 2-(4,8,11-Triscarbamoylmethyl-1,4,8,11-tetraazacyclotetradec-1-yl)acetamide (TETAM) derivatives bearing 1, 2, or 4 silylated arms have been synthesized and grafted to the surface of silica gel and ordered mesoporous silica samples. The resulting organic-inorganic hybrids have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Pb(II). The attractive recognition properties of these cyclam derivatives functionalized with amide pendent groups toward Pb(II) species and the highly porous structure of the adsorbents can be exploited for the selective and sensitive detection of the target analyte. Various parameters affecting the preconcentration and detection steps have been discussed with respect to the composition and pH of both accumulation and detection media, the nature of the adsorbent (number of silylated groups linking the macrocycle to silica, texture of materials), the accumulation time, and the presence of interfering cations. Under optimal conditions and for 2,min accumulation at open-circuit, the voltammetric response increased linearly with the Pb(II) concentration in a range extending from 2×10,7 to 10,5,M, while a longer accumulation time of 15,min afforded a linear calibration curve between 10,8 and 10,7,M with a detection limit of 2.7×10,9,M which is well below the European regulatory limit of lead in consumption water. [source] Synthesis and Photophysical Properties of LnIII,DOTA,Bipy Complexes and LnIII,DOTA,Bipy,RuII Coordination ConjugatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2010Miguel Vázquez López Abstract The synthesis and the systematic and comparative photophysical study of a series of visible (EuIII, TbIII) and NIR-emitting (NdIII, YbIII) lanthanide complexes (Ln2L) and ruthenium,lanthanide coordination conjugates (Ln2LRu) are reported. The GdIII complex, the GdIII,RuII coordination conjugate, as well as the RuII complex of the ligand H6L have also been synthesized and photophysically studied as control systems. The ligand H6L, composed of a central bipyridine binding unit and functionalized on each 5,-position with a DOTA macrocycle, has been successfully synthesized from cyclen, 5,5,-dimethyl-2,2,-bipyridine and 1,2-ethylendiamine in a nine-step process. Detailed luminescence studies of all complexes, including the determination of the quantum yield and lifetime, were carried out on finely powdered microcrystalline samples as well as in water, deuterated water and [D6]DMSO at ambient (295 K) and low temperature (77 K). The photophysical data corroborate the existence of energy transfer in the Ln2L complexes and in the Nd2LRu coordination conjugate. However, no (or at most, very little) energy transfer is takes place from the Ru(bipy)3 chromophore to the LnIII ion in the other Ln2LRu heteropolymetallic complexes. Moreover, the photophysical studies reveal that all the complexes and coordination conjugates adopt different conformations and hydration states in solution and in the solid state, which influences the efficiency of the energy transfer between the bipy and/or Ru(bipy)3 antennae and the LnIII ions. [source] Solid-State and Solution Structure of Lanthanide(III) Complexes with a Flexible Py-N6 Macrocyclic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009Cristina Núñez Abstract Lanthanide complexes of a hexaaza macrocyclic ligand containing a pyridine head unit (L) were synthesized (Ln = La,Lu, except Pm). The solid-state structures of the corresponding La, Ce, Pr, Nd, and Lu complexes were determined by single-crystal X-ray crystallography, and they reveal the presence of three different mononuclear complexes with three different conformations of the macrocycle and coordination environments around the metal ions. In all complexes the lanthanide ion is coordinated in an endomacrocyclic manner to the six nitrogen donor atoms of the ligand. In the La, Ce, and Pr complexes the metal ions show a 12-coordinate mononuclear environment in which 3 nitrate anions coordinate in a bidentate fashion. However, in the Nd analogue the metal ion displays a 10-coordinated environment with the coordination of 2 bidentate nitrate groups, whereas Lu shows a 9-coordinate environment interacting with 2 nitrate ligands, one of them acting as bidentate and the second one coordinating in a monodentate fashion. The 1H and 13C NMR spectra of the complexes recorded in CD3CN suggest that the complexes adopt in solution a similar structure to that observed for the Nd complex in the solid state. The [Ln(L)(NO3)3] and [Ln(L)(NO3)2]+ complexes were characterized by density functional theory (DFT) calculations (B3LYP model). The structures obtained from these calculations for La, Ce, Pr, and Nd are in good agreement with the experimental solid-state structures. The relative stabilities of the [Ln(L)(NO3)2]+ complexes with respect to the [Ln(L)(NO3)3] ones (Ln = La, Nd, Gd, Ho, or Lu) were studied both in vacuo and in acetonitrile solution (PCM model) at the same computational level. Our calculations indicate that in solution the [Ln(L)(NO3)2]+ species is the most stable one along the whole lanthanide series, in agreement with the NMR spectroscopic data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A Ruthenium(II)-Complexed Rotaxane Whose Ring Incorporates a 6,6,-Diphenyl-2,2,-bipyridine: Synthesis and Light-Driven MotionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Jean-Paul Collin Abstract By incorporating a 6,6'-diphenyl-2,2'-bipyridine (dpbipy) fragment in a ring, endo coordination of a ruthenium(II) center is performed selectively and almost quantitatively. The threaded system, containing a helical fragment, could be fully characterized. When the terminal functions of the rod-shaped helical complex threaded through the macrocycle are phenol groups, the complete rotaxane is prepared by the classical Williamson stoppering reaction in moderate yield. Light-induced motions of the unstoppered system (pseudorotaxane) and the real rotaxane have been studied. Under visible light irradiation, quantitative decoordination of the dpbipy-containing ring is observed, leading to the separate fragments (ring and helical thread) or to a new rotaxane (uncoordinated ring threaded by the dumbbell). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis and Physicochemical Characterization of Bis(macrocycles) Involving a Porphyrin and a meso -Substituted Corrole , X-ray Crystal Structure of a [(Free-base porphyrin),corrole]bis(pyridine)cobalt ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2005Jean-Michel Barbe Abstract A very efficient, simple synthesis of face-to-face porphyrin,corrole free-bases bearing substituents at the meso positions of the corrole ring is reported. Starting from the (porphyrin,aldehyde)zinc species 1Zn, porphyrin,corrole free-bases (3M, 3C) are obtained in two steps, in fairly good yields (40,43,%), compared to 11 steps for their corrole ,-pyrrole-substituted counterparts. Moreover, the possibility to directly synthesize the free-base (porphyrin,corrole)cobalt complex (5M or 5C) allows for the further preparation of heterodimetallic derivatives. Crystals of the bis(pyridine) adduct of 5M have been grown; the molecular structure clearly shows that the two pyridine molecules are coordinated to the cobalt ion in endo and exo positions, leading to an open-mouth geometry of the bis(macrocycle). The structure of 5M(py)2also shows intermolecular ,,, interactions along the [1,0,0] direction, leading to stacking of the complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Carboxy Ester Hydrolysis Promoted by a Dicopper(II) Macrocyclic Polyamine Complex with Hydroxypropyl Pendant GroupsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004Jin Huang Abstract A dinuclear CuII complex containing a hexaaza macrocyclic ligand bearing two 2-hydroxypropyl pendants, 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxypropyl)tricyclo[22.2.2.211,14]triaconta-1,11,13,24,27,29-hexaene (L), was synthesized. The title complex [Cu2(H,2L)Cl2]·6.5H2O was isolated as a blue crystal, orthorhombic, space group Fddd, with a = 16.4581(12), b = 32.248(2), c = 35.830(2) Å, V = 19017(2) Å3, Z = 16, R1 = 0.0690, and wR2 = 0.1546 [I > 2,(I)]. The protonation constants of Cu2L were determined by potentiometric titration, and it was found that the alcoholic hydroxypropyl group of the complex Cu2L exhibits low pKa values of pKa1 = 7.31, pKa2 = 7.83 at 25 °C. The hydrolysis kinetics of 4-nitrophenyl acetate (NA) promoted by the title complex have also been studied. The pH-rate profile for Cu2L gave a sigmoidal curve and showed a second-order rate constant of 0.39 ± 0.02 M,1 s,1 in 10% CH3CN/H2O(v/v), which is greater than that of the dinuclear CuII complex formed by a hexaaza macrocycle without pendants. The reason for the higher catalytic activity of the title complex is discussed. We found that the volume of nucleophile RO, can effect the hydrolysis of the carboxy ester, the nucleophilicity of RO, and the Lewis acidity of the metal macrocycle also affect the carboxy ester hydrolysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Copper(I)-Assembled Pseudorotaxanes Bearing Bis(nitrile) Ligands: Selective Formation of Large Chelate RingsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2004Efstathia G. Sakellariou Abstract The syntheses of two novel CuI -bis(benzonitrile) complexes of the type [Cu(dCNn)2][PF6] {where dCNn = NCPhO(CH2)nOPhCN, n = 3, 4} are described. Both compounds have been characterized by X-ray crystallography. To our surprise, and although the two complexes were quite similar, two very distinct structures were obtained. For the [Cu(dCN4)2][PF6] complex, a tetrahedral geometry was observed whereas for [Cu(dCN3)2][PF6], a polymeric assembly was formed. A further extension of this work involved the syntheses of two threaded species bearing the M30 macrocycle, Cu metal and a dCNn ligand. The formation of the desired complexes was confirmed by means of mass spectrometry as well as 1-D and 2-D 1H NMR spectroscopy. Finally, the cyclic voltammograms of all 4 new species were recorded giving rise to redox potentials ranging from +0.88 to +1.25 V. These new threaded complexes are of particular interest since they can form the basis of novel rotaxane structures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Metal,Macrocycle Complex as a Fluorescent Sensor for Biological Phosphate Ions in Aqueous SolutionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2010Xiao-huan Huang Abstract We synthesized tetraazamacrocycles 1 and 2 bearing two anthryl groups as sidearms, both of which exhibited high selectivity for the ZnII ion in switching-on-type responses in aqueous solution. For ligand 1, ZnII is coordinated by four nitrogen atoms of the macrocycle and two amino groups on the pendent arms, which results in proximity between the twofluorophores. So, 1 -ZnII shows obvious excimer emission in aqueous solution. When PPi or ATP was added (pH 7.4), the excimer emission of 1 -ZnII was quenched, whereas monomer emission was revived. To the best of our knowledge, no other known sensor has this characteristic under physiological pH conditions. At the same time, the obvious different fluorescence response of 1 -ZnII for PPi and ATP in water shows that receptor 1 -ZnII can be used as a selective fluorescent chemosensor for PPi and ATP anions. [source] Synthesis of Fullerene-Stoppered Rotaxanes Bearing Ferrocene Groups on the Macrocycle,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2010Aurelio Mateo-Alonso Abstract The synthesis, characterisation and behaviour of a series of rotaxanes containing a fulleropyrrolidine stopper and two ferrocene moieties on the macrocycle is reported. Remarkably, the presence of large and bulky ferrocene groups does not interfere either in the synthesis or in the translocation of the macrocycle induced by ,,, interactions between the macrocycle and the fullerene. The synthetic routes developed can also be applied to the preparation of rotaxane scaffolds that can be complexed to [Ru(CO)TPP] by axial coordination. Overall, the synthetic routes presented herein provide an efficient way to prepare a variety of rotaxanes and molecular shuttles with potential applications in different fields. [source] An Expedient Synthesis of Perfluorinated Tetraazamacrocycles: New Ligands for Copper-Catalyzed Oxidation under Fluorous Biphasic ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2006Augustin de Castries Abstract Conjugate additions of cyclam to perfluorohexyl vinyl sulfone and sulfoxide, which act as efficient fluorous Michael acceptors, readily give access to new fluoro-ponytail tetraazamacrocycles in good yields. The solubility of the N -tetrasubstituted macrocycles depends dramatically on the nature of the polar function (SO or SO2): the sulfoxide cyclam derivative is soluble in perfluorodecaline (pfd) and perfluoromethylcyclohexane (pfmc) while the sulfonyl derivative is almost insoluble in organic or fluorous solvents. In agreement with the well known affinity of cyclam for copper(II) ions, stable copper complexes of the fluorous macrocyclic ligands have been isolated and characterized. In chloroform/methanol, complexes with four perfluorinated tails have been obtained from reaction of the tetra- N -perfluorohexylsulfinyl-substituted macrocycle with copper nitrate and copper perfluorocarboxylate. In trifluoroethanol, a selective retro-Michael reaction has been observed and the same reaction specifically gives copper complexes of the tri- N -substituted macrocycle. Complexes with three and four fluorous tails associated with perfluorocarboxylate counteranions are soluble in fluorous solvents (pfd and pfmc). These copper complexes were tested as catalysts for the oxidation of cyclohexene by molecular oxygen in the presence of tert -butyl hydroperoxide (tbhp). The oxidation reactions proceed under fluorous biphasic conditions and the catalyst can be recovered and reused. Quenching experiments indicate that cyclohexenyl hydroperoxide is the main oxidation product of the reaction performed with or without tbhp. Interestingly, these perfluorinated copper complexes are good, recyclable catalysts for the oxidation of cyclohexene by molecular oxygen without tbhp at room temperature and 65 °C.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] The Effect of Ring Size on Catenane SynthesisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2003Stefan Duda Abstract The synthesis of a [2]catenane with 87-membered rings was improved and extended to [2]catenanes with 63- and 147-membered rings. One of the key features is the carbonate linkage between phenols with tolane substituents in the 2- and 6-positions, which serves as a covalent template for the geometrical arrangement of a macrocycle and a ring precursor. Subsequent cyclization of the threaded ring precursor gives the precatenane as the main product, and this is converted into the catenane by carbonate hydrolysis. As well as the precatenane, its dumbbell shaped isomer is formed in the cyclization step. From the known conformation of the templating carbonate moiety and the strong dependence of the ratio of precatenane and dumbbell on the ring size, the dumbbell's origin is attributed to the conformational flexibility of the large rings and not to geometrical ambiguity of the carbonate moiety. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Distinct Nanostructures from a Molecular Shuttle: Effects of Shuttling Movement on Nanostructural MorphologiesADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Weidong Zhou Abstract A solvent driven molecular shuttle that contains a TCBD chromophore and in which the macrocycle can be positioned close to or far from the TCBD unit with a change of solvent is prepared. Several distinct nanostructures are obtained by control of the shuttling movement of the macrocycle: i) in a mixed solvent of CHCl3/n -C6H14 (1/1, v/v), the macrocycle locates at the peptide station, and interlaced nanofibers form as a result of the extended intermolecular dipole,dipole interactions of the TCBD units; ii) in a solvent of dimethyl sulfoxide, the macrocycle moves along the long alkyl-chain, and worm-like nanoparticles form because the macrocycle obstructs the intermolecular dipole,dipole interactions of the TCBD units. This system confirms that the molecular aggregation behaviors can be controlled by the shuttling movement of the macrocycle. Exploitation of the molecular shuttle to control the molecular aggregation behaviors will provide greater understanding in the field of molecular shuttle applications. [source] NMR-Solution Structures and Affinities for the Human Somatostatin G-Protein-Coupled Receptors hsst1,5 of CF3 Derivatives of Sandostatin® (Octreotide)HELVETICA CHIMICA ACTA, Issue 12 2009Dieter Seebach Abstract The previously reported (Helv. Chim. Acta2008, 91, 2035) derivatives of octreotide (1) with a (CF3)-Trp substitution, i.e., 3, and with open-chain structures, i.e., 2, 4, and 5, have been tested for their affinities to hsst1,5 receptors and subjected to a detailed NMR analysis. Their affinities vary from 15,nM to 5,,M, as compared to 0.6,nM to 0.8,,M for octreotide itself (Table,1). This decreased bioactivity may have had to be expected for the open-chain compounds 4 and 5; possible reasons for this decrease in the case of CF3 derivative of octreotide, 3, are discussed. NMR Analysis (Tables,2 and 3) provides evidence for increased dynamics of all new derivatives 2,5. The dynamics of the octreotide molecule 1 was analyzed by (natural-abundance) longitudinal 13C-T1 -relaxation time measurements (Table,4), from which the conclusion is drawn that the backbone of the macrocycle is rather rigid on the time scale of this method. [source] Sensitized Lanthanide-Ion Luminescence with Aryl-Substituted N -(2-Nitrophenyl)acetamide-Derived ChromophoresHELVETICA CHIMICA ACTA, Issue 11 2009Michael Andrews Abstract The syntheses of the two tetraazamacrocyclic ligands L1 and L2 bearing a [(methoxy-2-nitrophenyl)amino]carbonyl chromophore, i.e., an N -(methoxy-2-nitrophenyl)acetamide moiety, together with their corresponding lanthanide-ion complexes are described. A combined spectroscopic (UV/VIS, 1H-NMR), structural (X-ray), and theoretical (DFT) investigation revealed that the absorption properties of the chromophores were dictated by the extent of electronic delocalisation, which in turn was determined by the position of the MeO substituent at the aromatic ring. X-Ray crystallographic studies showed that when attached to the macrocycle, both isomeric forms of the N -(methoxy-2-nitrophenyl)acetamide unit can participate in coordination, via the CO, to an encapsulated potassium cation. Luminescence measurements confirmed that such a binding mode also exists in solution for the corresponding lanthanide complexes (q ca. ,1), with the para -MeO derivative allowing longer wavelength sensitization (,ex 330,nm). [source] Kinetics and Mechanism of the Demetallation of Macrocyclic Nickel(II) Complexes by CyanideHELVETICA CHIMICA ACTA, Issue 3 2005Liselotte Siegfried The kinetics and the mechanism of the cyanide-induced demetallation of a series of Ni2+ complexes with macrocyclic ligands of different ring size (12- to 14-membered; see 1,4) and steric constraints was studied. Although the rates differ by almost five orders of magnitude when compared to each other under fixed experimental conditions (pH,10.5, [CN,]=10,2,M), all reactions proceed through the relatively rapid formation of cyano adducts [Ni(CN)nL] (n=1, 2), which then react with additional CN, or HCN to give the final products. Of paramount importance for the reaction rate is the geometry and configuration of the cyano adducts [Ni(CN)nL] (n=1,2). cis -Dicyano derivatives with a folded macrocycle react faster than trans -compounds. In the case of (1,4,8,11-tetraazacyclotetradecane)nickel(2+) ([Ni (4)]2+), which gives a trans- dicyano adduct, the base-catalyzed N-inversion necessary to obtain the cis- dicyano derivative becomes rate determining at high CN, concentrations. [source] Molecular Recognition of a Peptide by the Nickel(II) Complex of 1,4,7,10-Tetraazacyclododecane-2,9-dioneHELVETICA CHIMICA ACTA, Issue 3 2003Jian Gao The nickel(II) complex of the macrocycle 1,4,7,10-tetraazacyclododecane-2,9-dione (dota) was found to be efficient in the recognition of the dipeptide, glycyl-glycine (Gly-Gly) in aqueous solution. This (dota)NiII complex serves as a targeting molecule to form a stable ternary complex with the dipeptide at pH,8.3 in aqueous solution. The recognition constant (log K=19.20) and the recognition mechanism were investigated based on the potentiometric method. The single-crystal of a six-coordinated (dota)2NiII complex is also reported. [source] A Macrocyclic Model Dodecamer for Polyfluorenes,ADVANCED MATERIALS, Issue 1 2009Sascha C. Simon A , -conjugated, cyclododeca-2,7-fluorene macrocycle is synthesized as a new model compound for polyfluorenes. The structure formation is demonstrated by 1H NMR spectroscopy, MALDI-TOF, and STM measurements, and the optical properties of this monodisperse cycle are investigated using UV-vis and fluorescence spectroscopy. [source] One-Step Synthesis of Chiral Azamacrocycles via Palladium-Catalyzed Enantioselective Amination of 1,5-Dichloroanthraquinone and 1,5-DichloroanthraceneADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Elena R. Ranyuk Abstract Asymmetric amination of 1,5-dichloroanthraquinone and 1,5-dichloroanthracene with di- and trioxadiamines catalyzed by palladium complexes with various chiral phosphine ligands gave chiral macrocycles with ee values of up to 60%. The dependence of the chemical yields and enantiomeric excess on the nature of the starting compounds and the phosphine ligands employed was demonstrated. An unexpected spontaneous resolution upon crystallization of the macrocycle comprising anthraquinone and dioxadiamine moieties was observed while in the case of the macrocycle with a trioxadiamine linker racemic monocrystals were obtained. Crystallization of the enantiomerically enriched mixtures afforded chiral macrocycles with 88,99% ee. [source] Formation and applications of stable 10 nm to 500 nm supramolecular porphyrinic materialsISRAEL JOURNAL OF CHEMISTRY, Issue 3 2005Charles Michael Drain Nanoscaled materials of organic dyes are of interest for a variety of potential applications because of the rich photonic properties that this class of molecules can impart. One mode to form such nanoscaled materials is via self-organization and self-assembly, using reasonably well understood methods in supramolecular chemistry. But there are inherent complexities that arise from the use of organic-based supramolecular materials, including stability toward dioxygen, structural stability, and nanoarchitectures that may change with environmental conditions. Porphyrinoids have rich photonic properties yet are remarkably stable, have a rigid core, are readily functionalized, and metalation of the macrocycle can impart a plethora of optical, electronic, and magnetic properties. While there are many <10 nm porphyrinic assemblies, which may or may not self-organize into crystals, there is a paucity of 10,500 nm porphyrinic materials that can be isolated and stored. A variety of strategies towards the latter nanoscopic porphyrinic materials are discussed in terms of design, construction, and nanoarchitecture. The hierarchical structures include colloids, nanorods, nanotubes, nanorings, and nano-crystalline materials. This prolegomenon emphasizes the supramolecular chemistry, structure-stability, and structure-function relationships. The goal herein is to examine general trends and delineate general principles. [source] Complexation and chiral drug recognition of an amphiphilic phenothiazine derivative with , -cyclodextrinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2008Andrés Guerrero-Martínez Abstract Promethazine hydrochloride (PTZ) is an amphiphilic drug derived from the phenothiazine structure that possesses a charged aliphatic chain with a chiral carbon. In the presence of , -cyclodextrin (, -CD), this drug undergoes significant changes of its photophysical properties in aqueous solution. Fluorescence spectroscopy measurements show the formation of a 1:1 stoichiometry complex with quantum yield lower than that of the pure PTZ, and two fluorescence lifetimes, which can be assigned to the free and complexed forms of the drug. In addition, 1H NMR spectra, and 2D rotating-frame Overhauser enhancement spectroscopy (ROESY) were used to characterize the drug and the complex, and to determine the effects of the complexation on the aggregation. For the drug binary system, a noncooperative association process is observed, and in the presence of macrocycle, the chemical shifts reveal a chiral resolution of the drug enantiomers, with different stability constants of the complexes. , -CD modifies the aggregation of PTZ in an extension that confirms the formation of a 1:1 complex. ROE enhancements and molecular modeling strategies show the most likely structure of the complex in solution, in which one of the phenyl rings is buried into the CD cavity, with a slight inclusion of the aliphatic part. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1484,1498, 2008 [source] | |||||||||||||||||||||||||||||||||||||