New 2+2, 3+3 and 4+4 macrocycles derived from 1,2-diaminocyclohexane and 2,6-diformylpyridine

Two new Schiff base macrocycles - a 4+4 condensation product and a meso-type 2+2 condensation product - were obtained in a reaction of trans-1,2-diaminocyclohexane and 2,6-diformylpyridine. Reduction of these compounds led to the corresponding 4+4 and 2+2 macrocyclic amines. The macrocycles were characterised by NMR spectroscopy and electrospray mass spectrometry. The symmetry and stereochemistry of these macrocycles, as well as of new 3+3 and 4+4 diastereomers identified in solution, has been established. X-Ray structures of the 2+2 and 4+4 Schiff base macrocycles confirm the configurations determined on the basis of spectroscopic investigations. The crystal structures reveal that the centres of the square-shaped 4+4 macrocycles form channels as a result of columnar stacking.     

The syntheses of nitrogen‐oxygen donor macrocycles containing pyridine ring

Five new nitrogen‐oxygen mixed donor macrocycles have been prepared by condensation of 2,6‐bis [(2‐formylphenyl)oxymethyl]pyridine with different diamino compounds in hot methanol, followed by a one‐pot reduction of the intermediate bis‐Schiff base. All the macrocycles were identified by elemental analysis, and ir, uv, and nmr spectroscopy.     

Synthesis and Characterization of Novel Schiff Base Macrocyclic Compounds Containing Thiophene

Several novel Schiff base macrocyclic compounds containing thiophene were synthesized from d/ethyl 3,4-dialkoxythiophene-2,5-dicarboxylate, cyanuric chloride, diethylarnine and p-nitrophenol by reduction, oxidation, substitution and cyclization, and their structures were characterized by IR, NMR and electrospray ionization-rnass spectrorneter（ESI-MS）. The studies on their UV-Vis absorption spectra show that Schiff base rnacrocycles 6-10 have selective recognition for Fe^3＋.     

Zinc carboxylate cluster formation in conjugated metallomacrocycles: evidence for templation

A new [3 + 3] Schiff base macrocycle incorporating three N2O2 salphen-type binding sites and peripheral neopentyloxy substituents has been prepared. The incorporation of Zn2+ ions into this and related conjugated Schiff base macrocycles has been studied by NMR spectroscopy, mass spectrometry, and X-ray diffraction. When reacted with 7 equiv of zinc acetate, the macrocycles template the formation of heptanuclear complexes. Two tetranuclear Zn2+ complexes that are plausible intermediates in the assembly of the heptanuclear complexes have been isolated and structurally characterized. These reactive intermediates are promising substrates for the synthesis of polynuclear, mixed-metal clusters. We also demonstrate that this chemistry may be generalized to other bridging carboxylate ligands, such as methacrylate.     

Reversible-irreversible approach to Schiff base macrocycles: access to isomeric macrocycles with multiple salphen pockets

We have developed methodology for the formation of a new family of metal-free Schiff base macrocycles utilizing the differential exchange rates of aldimines and ketimines. The more robust ketimine bond is kinetically inert under the milder conditions used for aldimine bond formation. In particular, this route enables access to the first conjugated macrocycles with four unsymmetrical N2O2 salphen-like pockets.     

Highly substituted Schiff base macrocycles via hexasubstituted benzene: a convenient double Duff formylation of catechol derivatives

The synthesis of soluble, shape-persistent macrocycles is important for developing new materials. Double Duff formylation of 4,5-dialkylcatechol derivatives yields 3,6-diformyl-4,5-dialkylcatechols in moderate yields. These hexasubstituted aromatics are useful precursors to highly substituted Schiff base macrocycles. We illustrate convenient routes to these compounds as well as structural studies of two new macrocycles with alkyl substituents.     

Synthesis and characterization of new azo containing Schiff base macrocycle

Fully conjugated Schiff base macrocycle has been prepared through a simple and mild condition,a one-pot cyclization procedure of four-component without using a template.The condensation reaction of related bis（hydroxybenzaldehyde） with phenylenediamines to prepare a conjugated[2 + 2]Schiff base macrocycle has been investigated and fluorescent[2 + 2]Schiff base macrocycles with N₂O₂ binding pockets has been prepared and characterized by elemental analysis,¹H NMR,IR,fluorescent,UV-visible and MALDI mass spectroscopies.     

SYNTHESIS OF THE NEW SCHIFF BASE POLYAZA MACROCYCLES AND THEIR COMPLEXES WITH Cu2+ AND Ni2+

The new Schiff base macrocycles were synthesized from the condensation of diethylenetriamine or dipropylenetriamine with terephthalaldehyde. The relevant transition metal complexes were then formed with nickel and copper salts after the reduction of the macrocycles. CHN-analysis, IR, NMR, and mass spectroscopies were used for their structure characterization.     

Campestarenes: novel shape-persistent Schiff base macrocycles with 5-fold symmetry

A simple 1-step procedure yields a family of easily modifiable, stable, conjugated Schiff base macrocycles with 5-fold symmetry mediated by 3-center hydrogen bonding.     

One-pot synthesis of [1+1] and 62-membered [2+2] Schiff base macrocycles

New [1+1] and 62-membered [2+2] Schiff base macrocycles containing a 2,6-diamidopyridine subunit have been synthesized by condensation reaction of the precursors pyridine-2,6-dicarboxamide and 1,10-bis(20-formylphenyloxy)decane in the presence of phosphoric acid via a one-pot process. The cyclocondensed products were effectively isolated by gel column chromatography and characterized by ~1H NMR, FTIR, mass spectrometry and X-ray analysis. The two macrocycles have a twisted structure, and not an open ‘circular' conformation in the solid state.     

The synthesis and crystal structure of a new diprotonated Schiff base cryptand

Abstract

The synthesis and crystal structure of the diprotonated cryptand derived from the reaction of tren and 2,6-diacetyl pyridine is reported. The imino nitrogens of the Schiff base linkages are directed so that the dicarbimine functions are in trans, trans geometry relative to the pyridine C-N bond. This configuration has not previously been reported in related pyridine-derived Schiff base macrocycles.     

Novel chiral "calixsalen" macrocycle and chiral robson-type macrocyclic complexes

A family of novel chiral "calixsalen" Schiff base macrocycles R,R-H(3)L4, R,R-H(3)L5, containing three chiral diamino moieties were synthesized by an efficient self-assembly and characterized by (1)H and (13)C NMR, mass spectrometry, and X-ray diffraction. The systematic synthesis, structure, and coordination properties of the [2 + 2] and [3 + 3] Robson-type Schiff base macrocyclic mono-, di-, tri-, and tetranuclear metal complexes were explored.     

Synthesis and X-ray Structures of Novel Macrocycles and Macrobicycles Containing N,N-Di(pyrrolylmethyl)-N-methylamine Moiety: Preliminary Anion Binding Study

The [2 + 2] Schiff base condensation reactions between the newly synthesized dialdehyde, N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine), and ethylenediamine or p-phenylenediamine dihydrochloride readily afforded the 30- and 34-membered large size macrocycles in very high yields. Subsequent reduction reactions of these macrocycles with NaBH(4) gave the corresponding saturated macrocyclic hexaamines in good yields. The analogous reaction of the new dialdehyde with a triamine molecule afforded the [3 + 2] Schiff base macrobicycle in high yield, which was then reduced by reaction with NaBH(4) to give the saturated macrobicycle. All these compounds were characterized by spectroscopic methods. The anion binding properties of the saturated macrocycles having the ethylene and the phenylene linkers in CDCl(3) were studied by NMR titration methods. Although they have similar pyrrolic and amine NH groups their binding properties are different and interesting, owing to the conformational flexibility or rigidness rendered by the ethylene or phenylene groups, respectively. The macrocycle having the ethylene linkers binds anions in a 1:1 fashion, while the other receptor having the phenylene linkers prefers to bind anions in a sequential 1:2 fashion and has a multiple equilibria between a 1:1 and a 1:2 complexes, as shown by their binding constants, curve fittings by EQNMR, and Job plots. The X-ray structures of the 1:2 methanol, the aqua and the benzoate anion complexes of the macrocycles show two cavities in which the guests are bound, correlating with the high affinity found for the formation of stable 1:2 complexes in solution. The X-ray structure showed that the macrobicycle Schiff base adopts an eclipsed paddle-wheel shaped conformation and exhibits an out-out configuration at the bridgehead nitrogen atoms.     

The Rich Tautomeric Behavior of Campestarenes

Campestarenes are a new family of Schiff‐base macrocycles that form selectively in a one‐step synthesis. These macrocycles with five‐fold symmetry show solvent‐dependent tautomerization and dimerization or aggregation. In this paper, we have prepared new soluble campestarenes that do not aggregate. The initial single‐crystal X‐ray diffraction study of a campestarene reveals that these macrocycles are nearly flat. The tautomeric behavior of the campestarenes has been extensively studied by variable‐temperature, multinuclear NMR spectroscopy, UV/Vis spectroscopy, and IR spectroscopy. In polar solvents, such as DMF, the molecules exist predominantly in their keto‐enamine form, but the enol‐imine tautomer is dominant in non‐polar solvents. A detailed computational study of the tautomeric forms of campestarenes provides a theoretical basis for their behavior and corroborates the experimental data. The results of this study give the first comprehensive understanding of the electronic and spectroscopic properties of these pentagonal macrocycles.     

Synthesis and Electrical Conductivities of Fully Conjugated Schiff Base Macrocycles Containing 1,3,4-Oxadiazole

Thedelocalizedrs-electronicplanarstructureofthemoleculeisnecessarytodesignneworganicmetals.Recentlymuchattentionwaspaidontheuseofmuchrigidelectronwithdrawingl,3.4-oxadiazoleunitasbuildingblocksinthesynthesisofsyntheticmetalsandorganiclight-emittingdiodesmaterials'-'.Previouslywehavefoundthecon.lugatedmacrocyclecontainingl,3,4-oxadiazolecouldbeoxidativelydopedwithiodinetoformacharge-transfercomplexwithaconductivityof4.6x10-'scm-'.Tocontinuethisworkandunderstandtherelationshipsbetweenmoleculars…     

Surface Confined Synthesis of Hydroxy Functionalized Two-Dimensional Polymer: The Effect of the Position of Hydroxy Groups

We report on the on-surface synthesis of a series of two-dimensional polymers (2DPs) and macrocycles containing hydroxyl groups on a highly oriented pyrolytic graphite surface. The formed 2DPs and macrocycles were visualized through scanning tunneling microscopy. By varying the solvent and reaction temperature, structural evolution from oligomers to well-ordered 2DPs or discrete macrocycles was directly followed. In addition, we discovered that the reaction outcome can be steered from extended 2DPs to discrete macrocycles or catenular structures by exchanging the position of the hydroxyl and aldehyde group. These results indicate that the relative positions of hydroxyl and aldehyde groups on the biphenyl ring play a determining role in the control and selection of the final products of the surface-confined Schiff base coupling reaction.     

Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles

[reaction: see text] Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.     

Calix[4]pyrrole Schiff base macrocycles. Novel binucleating ligands for mu-oxo iron complexes

New bimetallic mu-oxo diferric complexes of several previously reported calix[4]pyrrole Schiff base macrocycles are described. The synthesis of a new member of this class of macrocycles is also reported; it was prepared via an acid-catalyzed condensation between 1,9-bisformyl-5,5-dipropyldipyrromethane and o-phenylenediamine. Reactions of the free base macrocycles or their bis-HCl salts with Fe(II) mesitylene, followed by air oxidation, gave the binuclear mu-oxo bis-Fe(III) compounds 6-10 in moderate yield. X-ray crystallography data reveal two different coordination environments for the Fe-O-Fe subunit in 6-10 that it is suggested can be controlled by altering the reaction conditions. Structural properties of these metalated pyrrolic macrocycles are also compared to those of mu-oxo diferric porphyrins and mu-oxo diferric texaphyrin. Complexes 6-10 exhibit two distinct types of M-N bonds that are similar in length to the bonds observed in metallotexaphyrin complexes. However, the electronics of the present systems are very different from those of texaphyrins and porphyrins in that no delocalized bonding patterns are observed within the ligands as a whole.     

Synthesis and Characterization of Macrocycles Containing 1,3,4-Oxadiazole

The design of molecules with delocalized π-electronic structures which are useful as organic conductor and light-emitting diodes(LEDs) has attracted much attention.^[1-2] We have synthesized some conjugated Schiff base macrocycles containing 1,3,4-oxadiazole(such as compound 1) and after being doped with I₂,they showed electrical conductivity in the region of semiconductor.^[3] To continue this work and understand the relationship between molecular structure and solid state properties, we designed other conjugated schiff base macrocycle containing 1,3,4-oxadiazole.     

Schiff base macrocycles containing pyrroles and pyrazoles

A double nucleophilic substitution reaction of 3,5-bis(chloromethyl)pyrazole with pyrroles generates a novel pyrrole-pyrazole hybrid building block, the pyrazole analogue to tripyrrane. Vilsmeier-Haack formylation produces the corresponding dialdehyde, which was used in the formation of a series of nonaromatic Schiff base macrocycles. NMR and UV/Vis spectroscopy and single-crystal diffractometry were used to characterize the novel macrocycles. The solid-state structures of select free bases and protonated members of this class of macrocycles display a range of intra- and intermolecular hydrogen-bonding patterns that suggest their use in molecular-recognition systems. They also contain an acid-sensitive chromophore. Their acid-base and anion-recognition properties were ascertained; alas, only modest anion-selective spectroscopic signatures could be detected by using UV/Vis and (1)H NMR spectroscopy. The macrocycles proved resistant toward oxidation to their aromatic congeners. The pyrrole-pyrazole building blocks presented are potentially useful for the synthesis of a range of pyrazole analogues of all-pyrrole macrocycles.