Photocontrolled On‐Surface Pseudorotaxane Formation with Well‐Ordered Macrocycle Multilayers

The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine‐terminated SAMs and subsequently with multilayers of macrocycles through layer‐by‐layer self assembly. A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled deposition of the axle into the surface‐bound macrocycle‐multilayers was monitored by UV/Vis spectroscopy and led to an increase of the molecular order, as indicated by more substantial linear dichroism effects in angle‐resolved NEXAFS spectra.     

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.     

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 of macrocycles and their application as chiral solvating agents in the enantiomeric recognition of carboxylic acids and α-amino acid derivatives

The chiral macrocycles 1 and 2 with multiple binding sites have been synthesized from D-phenylalanine as chiral solvating agents (CSAs) for the enantiomeric discrimination and determination of the enantiomeric excess of carboxylic acids and a-amino acids derivatives by the ¹H NMR spectroscopy. The results show that chiral macrocycles 1 and 2 are effective CSAs towards the carboxylic acids and a-amino acids derivatives.     

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 of Carbohydrate Based Macrolactones and Their Applications as Receptors for Ion Recognition and Catalysis

Glycomacrolactones exhibit many interesting biological properties, and they are also important in molecular recognitions and for supramolecular chemistry. Therefore, it is important to be able to access glycomacrocycles with different sizes and functionality. A new series of carbohydrate-based macrocycles containing triazole and lactone moieties have been designed and synthesized. The synthesis features an intramolecular nucleophilic substitution reaction for the macrocyclization step. In this article, the effect of some common sulfonate leaving groups is evaluated for macrolactonization. Using tosylate gave good selectivity for monolactonization products with good yields. Fourteen different macrocycles have been synthesized and characterized, of which eleven macrocycles are from cyclization of the C1 to C6 positions of N-acetyl D-glucosamine derivatives and three others from C2 to C6 cyclization of functionalized D-glucosamine derivatives. These novel macrolactones have unique structures and demonstrate interesting anion binding properties, especially for chloride. The macrocycles containing two triazoles form complexes with copper sulfate, and they are effective ligands for copper sulfate mediated azide-alkyne cycloaddition reactions (CuAAC). In addition, several macrocycles show some selectivity for different alkynes.     

Novel enantioselective receptors for N-protected glutamate and aspartate

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.     

Synthesis and characterization of pyridine-based polyamido-polyester optically active macrocycles and enantiomeric recognition for D- and L-amino acid methyl ester hydrochloride

Five new chiral macrocycles, 3a-e, have been prepared by the acylation cyclization of chiral diamine dihydrobromide intermediates 2a-c with 2,6-pyridinedicarbonyl dichloride in highly diluted solution at room temperature. The chiral diesters 1a-c needed for the preparation of the macrocycles were obtained from condensation of corresponding N-(Z)-L-amino acids and 2,6-bishydroxymethyl pyridine in the presence of DCC and DMAP. The enantiomeric recognition of chiral macrocycles 3a-e for D- and L-amino acid methyl ester hydrochlorides has been characterized by fluorescence spectra, which indicate that some of them exhibited significant chiral recognition for the enantiomers of D- and L-amino acid methyl ester hydrochlorides. The stoichiometry and binding constants of 3a-L-Am(2) and 3c-L-Am(2) complexes have been determined. An X-ray analysis of the chiral macrocycle 3b show that the chiral ligand is rather rigid and strained.     

1,1'-Binaphthyl-substituted macrocycles as receptors for saccharide recognition

The preparation of receptors for saccharide recognition in a natural environment has been an unmet goal for a long time. We present herein the synthesis and binding properties of (R,S)-1,1'-binaphthyl-substituted macrocycles as receptors for saccharide recognition in water/acetonitrile (1:1) and in DMSO. Porphyrin and metalloporphyrin macrocycles with two to four 1,1'-binaphthyl substituents and multiple hydroxy groups generate a binding site for saccharides that incorporates hydrogen-bonding hydroxy groups together with the aromatic hydrophobic pocket. The specificity for di- and trisaccharides is governed by the cavity size. The mechanism of binding has been studied by 1H NMR spectroscopy and the role of H-bonding and CH-pi interactions has been evaluated; the ability to bind saccharides has been demonstrated by the surface plasmon resonance (SPR) technique. The application of these macrocyclic receptors to sensor development is also presented.     

An Original Electrochemical Pathway for the Synthesis of Porphyrin Oligomers

An electrosynthesis process has allowed the formation of four oligomers, containing three, four, or five macrocycles. This method is based on the nucleophilic attack of porphyrins substituted by several pendant pyridyl groups to the electrogenerated radical cation of zinc β‐octaethylporphyrin (ZnOEP), according to an ECEC processes. Thus, a control of the number of macrocycles and of the geometry of the oligomers can be performed. These new compounds have been characterized by HRMS as well as ¹H NMR, UV/Vis, and fluorescence spectroscopy, and electrochemistry. The results show a strong influence of the pyridinium spacers on the macrocycles.     

A photoelectron study of the alkali bromides and iodides

Precise values have been determined for the binding energies of the outer electronic bands of the alkali bromides and iodides using 40.81 eV ultraviolet photoelectron spectroscopy. These values have been corrected for relaxation effects and then favourably compared with the Born model for ionic solids in terms of both the absolute values of binding energy and the energy separation between the outer valence bands.     

New fluorescence PET systems based on N2S2 pyridine-anthracene-containing macrocyclic ligands. spectrophotometric, spectrofluorimetric, and metal ion binding studies

Three new fluorescent devices for protons and metal ions have been synthesized and characterized, and their photophysical properties have been explored; these are the macrocycles 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1) and 7-(10-methyl-9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L2) and the bis macrocycle 7,7'-[9,10-anthracenediylbis(methylene)]bis-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L3). All these systems have a pyridil-thioether-containing macrocycles as a binding site and an anthracene moiety as a signaling agent. The coordination properties of these ligands toward Cu(II), Co(II), Ni(II), Zn(II), and Pd(II) have been studied in solution and in the solid state. The addition of these metal ions to dichloromethane solutions of L1, L2, and L3 produce strong changes in the absorption and emission spectra of these ligands. The stoichiometry of the species, formed at 298 K, have been determined from absorption and fluorescence titrations. The Co(II) and Cu(II) complexes of L1 have been studied by EPR spectroscopy. This last complex and its free ligand have also been characterized by X-ray crystallography.     

Elite new anion ligands: polythioamide macrocycles

Prototypes for a new class of polythioamide-based macrocycles have been synthesized and anion-binding capabilities assessed. Results indicate higher anion binding for H(2)PO(4)(-), HSO(4)(-), and F(-) for monocycles, but somewhat lessened binding capabilities for bicycles compared with amide corollaries.     

Synthesis, structure, and computational studies of soluble conjugated multidentate macrocycles

[Chemical reaction: See text] Conjugated, shape-persistent macrocycles based on [3 + 3] Schiff-base condensation are of interest for supramolecular materials. In an effort to develop new discotic liquid crystals based on these compounds, a series of macrocycles with peripheral alkoxy groups of varying length have been prepared. The synthesis and mechanism of formation have been probed by isolation of oligomeric intermediates. A single-crystal X-ray diffraction study of one macrocycle revealed a nonplanar, strongly hydrogen-bonded structure. To our surprise, even with very long substituents, the macrocycles were not liquid crystalline. This has been rationalized by ab initio calculations that indicate the macrocycles are undergoing rotation of the dihydroxydiiminobenzene rings that may not allow a stable discotic liquid crystalline phase. These results provide new insight into the formation and properties of these large macrocycles and may provide guidance to developing stable liquid crystalline materials in the future.     

Oxazole-based peptide macrocycles: a new class of G-quadruplex binding ligands

Herein we report on the synthesis and DNA binding properties of a new class of water soluble oxazole-based peptide macrocycles that bind selectively to quadruplex DNA, with no detectable binding to duplex DNA. We have recently identified one quadruplex in the proto-oncogene c-kit that is suspected to act as a regulatory element for the expression of the c-kit gene. Here we provide the first example of a ligand binding to and stabilizing the c-kit quadruplex. Moreover, we show that these macrocycles show a preference for the c-kit quadruplex as compared to the human telomeric quadruplex.     

Synthesis of a new 24-membered tetramide macrocycle and X-ray crystal structure determination

The synthesis and characterization of a new 24-membered tetramide macrocycle (6) related to Leigh's macrocycles and catenanes is reported. The replacement of p-xylylenediamine (Leigh) by m-xylylenediamine (this work) strongly modifies the geometry and properties of the new macrocycle. NMR spectroscopy (in DMSO?d₆ solution) and X-ray crystallography have been used to characterize compound 6. The structural features in the crystal (conformational aspects and H-bonding) have been discussed comparatively to two similar macrocycles NEWHIJ and UJUNOC.     

Conformational effects of bay substituents on optical, electrochemical and dynamic properties of perylene bisimides: macrocyclic derivatives as effective probes

A series of diagonally and laterally bridged regioisomeric macrocycles based on 1,6,7,12-tetraaryloxy-substituted perylene bisimides (APBIs) have been synthesized and characterized. The different orientations of the aryloxy residues, that is, horizontal or perpendicular to the perylene core, in the regioisomeric macrocycles have been elucidated by NMR spectroscopy, and the dynamic properties of the laterally bridged regioisomers have been investigated by temperature-dependent NMR measurements. The influence of the different orientations of the aryloxy substituents on the electrochemical properties of APBIs is demonstrated by cyclic voltammetry, which reveals that a perpendicular orientation of the aryloxy residues relative to the perylene core leads to a substantial decrease of the LUMO energy level of the perylene bisimide electrophore. The optical properties of the regioisomeric macrocycles have been determined by UV/Vis and fluorescence spectroscopy. It has been shown that the diagonally bridged macrocycles exhibit optical properties that differ significantly from those of an open-chain reference compound, whereas the optical properties of the laterally bridged isomers resemble those of the reference system. This demonstrates that unrestricted aryloxy substituents prefer the lateral conformation in solution. Solvent-dependent fluorescent properties have been exemplified for one diagonally bridged derivative, suggesting a photoinduced electron transfer process as fluorescence quenching mechanism for APBIs. From these investigations, guidelines toward highly fluorescent APBI dyes in polar media could be derived.     

Uranium 4f binding energies studied by X-ray photoelectron spectroscopy

Uranium 4f binding in a range of U(IV) and U(VI) compounds have been measured by X-ray photoelectron spectroscopy.     

Double armed crown ethers and armed macrocycles as a new series of metal-selective reagents: a review

Various double armed crown ethers and related macrocycles are presented as metal-selective reagents characterized by macrocyclic ligands and metal-ligating sidearms. They exhibit unique metal binding and recognition functions via macroring-sidearm cooperative action. Since they form three dimensional complexes suitable for metal-sensing and separation, we can develop a new series of metal-selective reagents via armed macrocycle strategy. Polymerization and immobilization of the armed macrocycles further enhance the usefulness in analytical science. This review focuses primarily on the molecular design, host-guest chemistry, and analytical applications of the armed macrocycles, and clearly indicates that these macrocycles provide new options in designing a metal-selective reagent.