Search results for "Supramolecular"

Reversible Dimerization and Polymerization of a Janus Diradical To Produce Labile C−C Bonds and Large Chromic Effects

2016

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ‐dimers and σ‐polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C−C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain …

Structural insight into the reaction mechanism of Pd-catalyzed nitrile hydration: Trapping the [Pd(H2O)4]2+ cation through a supramolecular complex

2016

Abstract Four new bis(oxamato)palladate(II) complexes of formula (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CN (1), (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CONH2 (2) and (n-Bu4N)4[Pd(H2O)4][Pd(4-Xpma)2]3·2CH3CONH2 with X = Br (3) and Cl (4) (2,4,6-Me3pma = N-2,4,6-trimethylphenyloxamate, 4-Brpma = N-4-bromophenyloxamate, N-4-chlorophenyloxamate and n-Bu4N+ = tetra-n-butylammonium) have been obtained and characterized by single crystal X-ray diffraction. All of them contain bis(oxamato)palladate(II) anions and bulky n-Bu4N+ cations, but compounds 3 and 4 have also the out of the ordinary [Pd(H2O)4]2+ inorganic cation. Acetonitrile and appealing acetamide are present as lattice molecules in compounds (1) and …

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

2020

Crown ethers are common building blocks in supramolecular chemistry and are frequently applied as cation sensors or as subunits in synthetic molecular machines. Developing switchable and specifically designed crown ethers enables the implementation of function into molecular assemblies. Seven tailor-made redox-active crown ethers incorporating tetrathiafulvalene (TTF) or naphthalene diimide (NDI) as redox-switchable building blocks are described with regard to their potential to form redox-switchable rotaxanes. A combination of isothermal titration calorimetry and voltammetric techniques reveals correlations between the binding energies and redox-switching properties of the corresponding ps…

Directional Shuttling of a Stimuli-Responsive Cone-Like Macrocycle on a Single-State Symmetric Dumbbell Axle

2018

Rotaxane-based molecular shuttles are often operated using low-symmetry axles and changing the states of the binding stations. A molecular shuttle capable of directional shuttling of an acid-responsive cone-like macrocycle on a single-state symmetric dumbbell axle is now presented. The axle contains three binding stations: one symmetric di(quaternary ammonium) station and two nonsymmetric phenyl triazole stations arranged in opposite orientations. Upon addition of an acid, the protonated macrocycle shuttles from the di(quaternary ammonium) station to the phenyl triazole binding station closer to its butyl groups. This directional shuttling presumably originates from charge repulsion and an …

Subcomponent Self-Assembly A Quick Way to New Metallogels

2013

Subcomponent self-assembly, introduced by the Nitschke group,[1] is a process which allow complex structures to be generated from simple building blocks (generally aldehydes and amines). In this bottom-up approach, the building blocks spontaneously self-assemble around templates (usually metal ions) leading to a simultaneous covalent (C=N) and dative (N– metal) bonds formation. The method has been successfully used to construct well-defined metal-organic macrocycles, helicates, catenanes, rotaxanes, grids,[2] and cages.[3] Our field of interest lies not in building-up of defined structures but in designing gelator molecules for a formation of supramolecular gels as functional nanomaterials.…

FOLATE RECEPTOR-TARGETED SUPRAMOLECULAR VESICULAR AGGREGATES (SVAS)FOR ANTICANCER THERAPY

2009

(-)-Isosteviol as a Versatile Ex-Chiral-Pool Building Block for Organic Chemistry

2013

(–)-Isosteviol is readily available in large quantities by the acidic treatment of a common alternative sweetener. The two functional groups of (–)-isosteviol are presented on the same side of the ent-beyerane scaffold with a mutual C–C distance of about 7 A. Their unique concave arrangement experiences a strong asymmetric environment due to an adjacent methyl group. Consequently, this building block has found several applications in supramolecular chemistry and organocatalysis. These areas and the chemical modification of this scaffold as well as its biological activity are surveyed.

Bis (μ-tetrazolato-NN′) bridged dinuclear nickel(II) Schiff base complexes: Tandem synthesis, structure and self assembly

2015

Abstract Two new bis(μ-tetrazolato-NN′) bridged dinuclear nickel(II) Schiff base complexes [Ni2L12(PTZ)2]·2(CH3)2SO·2.69H2O (1) and 2[Ni2L22(PTZ)2]·3H2O (2) (HL1 and HL2 are Schiff bases, HL1 = 2-((2-(dimethylamino)ethylimino)methyl)phenol, HL2 = 2-((2-(methylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) have been synthesized via [3+2] cyclo-addition of 2-cyanopyrazine and sodium azide in presence of nickel(II) acetate tetrahydrate and the respective Schiff bases. The structures of the complexes are confirmed by single crystal X-ray diffraction analysis. Both complexes show fluorescence. The change in the denticity of the Schiff base blocking ligand is shown to …

Mononuclear Fe(III) and tetranuclear [Fe(III)Gd(III)]2 complexes with a Schiff-base ligand derived from the o-vanillin: Synthesis, crystal structures…

2011

The mononuclear high-spin iron(III) complexes [Fe(3-MeOsalpn)Cl(H 2 O)] ( 1 ) and [Fe(3-MeOsalpn)(NCS)(H 2 O)]·0.5CH 3 CN ( 2 ) and the tetranuclear oxo-bridged compound [{Fe(3-MeOsalpn)Gd(NO 3 ) 3 } 2 (μ-O)]·CH 3 CN ( 3 ) [3-MeOsalpn 2−  =  N , N ′-propylenebis(3-methoxysalicylideneiminate)] have been prepared and magneto-structurally characterised. The iron(III) ion in 1 and 2 is six-coordinated in a somewhat distorted octahedral surrounding with the two phenolate-oxygens and two imine-nitrogens from the Schiff-base building the equatorial plane and a water ( 1 and 2 ) and a chloro ( 1 )/thiocyanate-nitrogen ( 2 ) in the axial positions. The neutral mononuclear units of 1 and 2 are assemb…

Copper(II) complexes with tridentate N2O donor Schiff base isomers: Modulation of molecular and crystalline architectures through supramolecular inte…

2013

Abstract Four copper(II) complexes, [Cu(L1)(μ-Cl)]n (1), [Cu2(L2)2(μ-Cl)2] (2), [Cu(L1)(μ1,5-NCNCN)]n (3) and [Cu(L2)(μ1,5-NCNCN)]n (4), where HL1 = 1-[(2-dimethylamino-ethylimino)-methyl]-naphthalen-2-ol and HL2 = 1-[(2-ethylamino-ethylimino)-methyl]-naphthalen-2-ol, acting as tridentate N2O donor ligands, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Complexes 1, 3 and 4 show polymeric chain structures, whereas 2 has a double chloride bridged dimeric structure. The existence of C–H⋯π interactions between the dimeric units of 2 gives rise to a 2D supramolecular network. Complex 3 shows a zipper structure…