Hydrogen-bonded aryl amide macrocycles: synthesis, single-crystal structures, and stacking interactions with fullerenes and coronene

Six hydrogen-bonded shape-persistent aryl amide macrocycles have been prepared by using one-step and (for some) step-by-step approaches. From the one-step reactions, 3 + 3, 2 + 2, or even 1 + 1 macrocycles were obtained in modest to good yields. The reaction selectivity was highly dependent on the structures of the precursors. The X-ray structural analysis of two methoxyl-bearing macrocycles revealed intramolecular hydrogen bonding and weak intermolecular stacking interaction; no column-styled stacking structures were observed. The 1H (DOSY) NMR, UV-vis, and fluorescent experiments indicated that the new rigidified macrocycles complex fullerenes or coronene in chloroform through intermolecular pi-stacking interaction. The association constants of the corresponding 1:1 complexes have been determined if the stacking was able to cause important fluorescent quenching of the macrocycles or coronene.     

A Model for Nicotinamide-Trytophane Charge-Transfer Interactions: The complexation of nicotinamide-ammonium salts by a macrocyclic receptor molecule bearing tryptophane side chains

The complexation of primary ammonium salt substrates by macrocyclic polyether receptor molecules provides a general method for studying the nature and stereochemistry of intermolecular interactions. The substrates and receptors are fitted each with one of the interacting units and the resulting effects in the complex are analyzed. The method is used to study the biologically important indole-pyridinium donor-acceptor interaction. The complexes between macrocycles, bearing an indole group in side chains, and pyridinium-ammonium salts display a characteristic charge-transfer band. The absorption coefficients and stability constants have been determined. Competition experiments also provide a new method for measuring the stability constants of macrocycle-ammonium complexes in organic solvents.     

Allyl‐Functionalized Dioxynaphthalene[38]Crown‐10 Macrocycles: Synthesis,Self‐Assembly,and Thiol‐ene Functionalization

Five dioxynaphthalene[38]‐crown‐10 ( DNP38C10 ) macrocycles bearing one, two, three, or four allyl moieties have been synthesized and their ability to spontaneously self‐assemble with methyl viologen to form [2]pseudorotaxanes has been evaluated. Association constants between methyl viologen and several of the allyl‐functionalized DNP38C10 macrocycles are found to be comparable to that of methyl viologen and unfunctionalized DNP38C10 , however, the enthalpic and entropic factors that underlie overall binding free energy vary systematically with increasing allyl substitution. These variations are explained through a combination of solution phase and solid‐state analysis of the macrocycles and their complexes. The utility of endowing DNP38C10 macrocycles with allyl moieties is further demonstrated by the ease with which they can be functionalized through thiol‐ene click chemistry.     

Stability, dynamics, and selectivity in the assembly of hydrogen-bonded hexameric capsules

Fluorescence resonance energy transfer (FRET) was employed to monitor the dynamics of hydrogen-bonded hexameric assemblies formed from resorcin[4]arenes and pyrogallol[4]arenes. Studies were designed to provide further insights into the degree of assembly and stability of these self-assembled capsules at the micro- to nanomolar concentration ranges that are not accessible by NMR studies. The results of this investigation reveal factors that influence the self-assembly of these macrocycles into hexameric capsules. Pyrogallolarenes are very sensitive to the concentration of mixing, with an increase in the equilibration half-life from 36 min at 250 nM to 156 min at 10 microM. The resorcinarenes showed little difference in exchange rates over the same concentration range. The temperature of mixing of the macrocycles was found to be important for both systems with a 12-fold increase in exchange rates over a 20 degree range for the pyrogallolarenes and a 2-fold rate increase for the resorcinarenes over the same temperature range. The stability of the capsules to polar additives such as methanol was probed, with the pyrogallolarenes requiring a higher percentage (1.6% v/v in dichloromethane) of methanol to disassemble the capsules than the resorcinarenes (1.0% v/v in dichloromethane). Pyrogallolarenes assemble in both anhydrous and wet solvents whereas water-saturated solvents are necessary to facilitate the formation of resorcinarene capsules. In addition to these studies, evidence of strict self-sorting in the formation of distinct pyrogallolarene and resorcinarene hexamers was obtained.     

Conductance study of the thermodynamics of complexation of amantadine, rimantadine and aminocyclohexane with some macrocyclic compounds in acetonitrile solution

A conductance study concerning the interaction between cationic organic ammonium ions amantadine, rimantadine, and aminocyclohexane with 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6) and cryptand C222 in acetonitrile solution has been carried out at different temperatures. The stability constants of the resulting 1:1 cornplexes at various temperatures were determined from the computer fitting of molar conductance-mole ratio data. The enthalpy and entropy of complexation reactions were evaluated from the temperature dependence of the formation constants. The influences of different parameters such as steric hindrance of organic amines and macrocycles, conformations of the free and complexed ligands, and solvent-ligand interaction on the thermodynamic data are discussed.     

Directing the Self-Assembly of Aromatic Foldamer Helices using Acridine Appendages and Metal Coordination

Folded molecules provide complex interaction interfaces amenable to sophisticated self-assembly motifs. Because of their high conformational stability, aromatic foldamers constitute suitable candidates for the rational elaboration of self-assembled architectures. Several multiturn helical aromatic oligoamides have been synthesized that possess arrays of acridine appendages pointing in one or two directions. The acridine units were shown to direct self-assembly in the solid state via aromatic stacking leading to recurrent helix-helix association patterns under the form of discrete dimers or extended arrays. In the presence of Pd(II), metal coordination of the acridine units overwhelms other forces and generates new metal-mediated multihelical self-assemblies, including macrocycles. These observations demonstrate simple access to different types of foldamer-containing architectures, ranging from discrete objects to 1D and, by extension, 2D and 3D arrays.     

C-取代二氧三胺大环配体合成及其Cu(II)配合物性质研究

本文合成了1, 4, 7-三氮杂环十烷-8, 10-二酮(td)和9-(2'-羟基苄基)-1, 4, 7-三氮杂环十烷-8, 10-二酮(btd)两个新型二氧三胺大环配体, 经元素分析, IR, 1H NMR以及MS等方法表征。采用分子力学方法探讨了取代基对配体合成的影响。利用pH法, 在25.0±0.1℃,I=0.1mol/L KNO3条件下, 测定了配体btd的质子化常数及其与Cu(II)配位的平衡常数。结合光谱滴定及配合物EPR结果, 讨论了二氧三胺大环配体与Cu(II)离子的配位方式。     

Synthesis and metalation of novel fluorescent conjugated macrocycles

[reaction: see text] Large shape-persistent conjugated macrocycles with tunable pore diameters in the nanometer regime were prepared by a simple, one-pot procedure. These new self-assembled macrocycles contain rings of 48-66 covalently bonded atoms and can bind multiple metal ions, forming soluble luminescent complexes.     

The Interaction of Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with Mixed Donor Macrocycles Containing Pendant Carboxylic Acid Functions

The syntheses of mixed oxygen-nitrogen donor macrocycles incorporating two or three pendant carboxylic acid groups are described. Potentiometric titrations in water (I = 0.1; KNO₃) at 25°C have been used to determine the stability constants for the 1: 1 (metal:ligand) complexes of Co(II). Ni(II), Cu(II), Zn(II), and Cd(II). The constants obtained are compared with the previously determined values for the corresponding complexes of the unsubstituted macrocyclic precursors. The results of these studies indicate that each carboxylate function participates in binding to the central metal. For some metal-ion/ligand systems there is evidence that ring size effects influence the overall stability patterns and that, in such cases, both the ether oxygens as well as the tertiary amines of the macrocyclic rings appear to bind to the metal.     

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.     

The unique properties observed for the unsymmetrical macrocyclic compounds with the highly distorted structure

A new class of aza-macrocycles with the highly distorted structure was found to exhibit unique properties. These macrocycles react with various lithium salts to form lithium complexes and their lithium complexation reactions depend on a substituent on the macrocyclic ring; slower rates and larger equilibrium constants were observed for the macrocycle with a bulkier substituent. The irradiation of these macrocycles by UV light was found to lead to the isomerization, and the photoisomerization rate of macrocycle with the bulky substituent was much faster. The highly distorted structure of these macrocycles makes it much easier to change the conformation of macrocyclic skeleton and these macrocycles have a variety of conformations. The factors to govern this conformational change were therefore explored. The solvent effect was examined by ¹H NMR spectroscopy, because these macrocycles have a strong intramolecular hydrogen bond in the ring. As a result, the solvent was found to have a big effect on the ¹H NMR spectra of macrocycles that could be explained in terms of the conformational change of macrocycle. This finding suggests the solvent to be an important way of controlling the conformation.     

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.     

Aza-crown macrocycles as chiral solvating agents for mandelic acid derivatives

A series of new chiral macrocycles containing the trans-1,2-diaminocyclohexane (DACH) subunit and arene- and oligoethylene glycol-derived spacers has been prepared in enantiomerically pure form. Four of the macrocycles have been characterized by X-ray crystallography, which reveals a consistent mode of intramolecular N-H···N hydrogen bonding and conformational variations about the N-benzylic bonds. Most of the macrocycles were found to differentiate the enantiomers of mandelic acid (MA) by (1)H NMR spectroscopy in CDCl(3); within the series of macrocycles tested, enantiodiscrimination was promoted by (i) a meta-linkage geometry about the arene spacer, (ii) the presence of naphthalene- rather than phenylene-derived arene spacers, and (iii) increasing length of the oligoethylene glycol bridge. (1)H NMR titrations were performed with optically pure MA samples, and the data were fitted to a simultaneous 1:1 and 2:1 binding model, yielding estimates of 2:1 binding constants between some of the macrocycles and MA enantiomers. In several cases, NOESY spectra of the MA:macrocycle complexes show differential intramolecular correlations between protons adjacent to the amine and carboxylic acid groups of the macrocycles and MA enantiomers, respectively, thus demonstrating geometric differences between the diastereomeric intermolecular complexes. The three most effective macrocycles were employed as chiral solvating agents (CSAs) to determine the enantiomeric excess (ee) of 18 MA samples over a wide ee range and with very high accuracy (1% absolute error).     

Molecular Triangles: Synthesis,Self‐Assembly,and Blue Emission of Cyclo‐7,10‐tris‐triphenylenyl Macrocycles

A set of cyclo‐7,10‐tris‐triphenylenyl macrocycles have been prepared by a Yamamoto cyclotrimerization protocol. In these novel macrocycles, three triphenylene units are covalently linked to each other, resulting in the formation of triangular‐shaped molecules. The fully planar derivative revealed pronounced self‐assembly behavior. NMR spectroscopy was used to determine the association constant in solution. 2D wide‐angle X‐ray scattering was applied to the study of the liquid crystallinity of this new discotic mesogen in the bulk state. Furthermore, nonplanar, laterally substituted derivatives were successfully tested as blue emitters in organic light‐emitting diodes owing to their unique optoelectronic properties and their high stability. In this case, substitution with sterically demanding phenyl groups was efficiently used to suppress intermolecular packing, thus preventing undesired quenching effects.     

Cyclic triureas--synthesis, crystal structures and properties

The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been studied by 1H NMR. Complexation constants for chloride, bromide and acetate have been measured for all trimers by UV spectrophotometry. Molecular dynamics simulations have been carried out to determine the conformation of the free receptors in chloroform and acetonitrile. They show that in chloroform, intramolecular hydrogen bonding occasionally facilitated by trans-->cis isomerisation of an amide bond dominates the conformation of the macrocycles while in acetonitrile (the solvent used for complexation measurements), the ligating urea NH protons are properly arranged for the complexation of anions, however, their strong solvation is counteractive to the complexation.     

Sterically congested, hexameric tetrakispyridinyl-Pd(II)/Cd(II)-metallomacrocycles: self-assembly and structural characterization

Hexagonal Pd(II)- or Cd(II)-tetrakispyridinyl-based macrocycles are quantitatively self-assembled from 4'-(3-pyridinyl)-4,4'-di(tert-butyl)-2,2'?:?6',2'-terpyridine and structurally confirmed by NMR and TWIM-MS.     

Facile synthesis of enantiopure chiral molecular rectangles exhibiting induced circular dichroism

[structure: see text] The facile syntheses of enantiopure molecular rectangles using 1,8-bis(trans-Pt(PEt(3))(2)(NO(3)))anthracene and optically pure d- or l-tartrate are reported in high yields. These self-assembled macrocycles are unique examples where the phenomenon of induced chiral dichroism (ICD) has been observed in chiral metallosupramolecular assemblies.     

Redox active macrocyclic receptors for neutral guests

A novel series of triazine-appended macrocyclic complexes has been investigated as potential hydrogen bonding receptors for complementarily disposed heterocycles. Cocrystallization of a melamine-appended azacyclam complex of Cu(II) has been achieved with barbitone, the barbiturate anion and thymine. In each case, a complementary DAD/ADA hydrogen bonding motif between the melamine group and the heterocycle has been identified by X-ray crystallography. Electrochemical studies of the copper macrocycles in both nonaqueous and aqueous solution show anodic shifts of the Cu(II/)(I) redox couple of more than 60 mV upon addition of guest molecules with matching H-bonding motifs. The Zn(II) analogues have been synthesized via transmetalation of the Cu(II) complex, and their guest binding properties investigated by NMR spectroscopy. (1)H NMR shifts of up to 0.8 ppm were observed upon addition of guest, and stability constants are similar to those obtained electrochemically.     

Aza-Oxa-Triazole Based Macrocycles with Tunable Properties: Design,Synthesis, and Bioactivity

A modular platform for the synthesis of tunable aza-oxa-based macrocycles was established. Modulations in the backbone and the side-chain functional groups have been rendered to achieve the tunable property. These aza-oxa-based macrocycles can also differ in the number of heteroatoms in the backbone and the ring size of the macrocycles. For the proof of concept, a library of macrocycles was synthesized with various hanging functional groups, different combinations of heteroatoms, and ring sizes in the range of 17–27 atoms and was characterized by NMR and mass spectrometry. In light of the importance of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and the significance of triazole groups for various applications, we employed the click-reaction-based macrocyclization. The competence of the synthesized macrocycles in various biomedical applications was proven by studying the interactions with the serum albumin proteins; bovine serum albumin and human serum albumin. It was observed that some candidates, based on their hanging functional groups and specific backbone atoms, could interact well with the protein, thus improving the bioactive properties. On the whole, this work is a proof-of-concept to explore the backbone- and side-chain-tunable macrocycle for different properties and applications.     

Bipyrrole- and dipyrromethane-based amido-imine hybrid macrocycles. New receptors for oxoanions

Three new amido-imine-type hybrid macrocycles based on substituted pyrrole units have been synthesized and shown to act as effective receptors for oxoanions in the solid state and in acetonitrile solution. One of the macrocycles in question, compound 15, was characterized by X-ray diffraction analysis as the free macrocycle and as a complex with sulfuric acid. A comparison of the resulting structures reveals that this receptor is capable of undergoing a conformational change and, as a consequence, varying the number of donor sites that can interact with a bound substrate. This system and the other two new receptors described in this work (macrocycles 14 and 16, respectively) display a high affinity toward oxoanions (studied as their tetrabutylammonium (TBA) salts), with association constants on the order of 10(7) M-1 being determined in acetonitrile solution using standard UV-vis spectroscopic titration methods. A competitive titration method was used to determine affinity constants in excess of ca. 10(6) M-1. Two of the receptors (14 and 15) were found to bind acetate, hydrogen sulfate, and dihydrogen phosphate anion well, and the bipyrrole-based receptor (14) was also found to bind the perrhenate anion. In contrast, the bis-dipyrromethane-derived receptor (16) was found to bind chloride anion preferentially. The unusual selectivity displayed by 16 for this spherical anion was rationalized on the basis of single-crystal X-ray diffraction data and DFT modeling calculations, which revealed a rigid structure appropriately suited for chloride anion recognition.