Synthesis and self-association properties of diethynylbenzene macrocycles

We synthesized diethynylbenzene macrocycles (DBMs), cyclic oligomers of diethynylbenzene, having functional groups in the periphery of the macrocyclic framework and investigated their self-association properties in solution resulting from π-π stacking interaction. The tetrakis-DBM having hexadecyl ester groups showed dimerization behavior not only in chloroform-d, but also in o-dichlorobenzene-d₄.     

Synthesis of macrocycles containing two pyridine and two polyamine moieties via Pd-catalyzed amination

The synthesis of macrocycles containing two pyridine and two polyamine fragments was carried out by the Pd-catalyzed amination of 2,6-dihalopyridines using polyamines and dioxadiamine. Two alternative approaches were elaborated and compared: via intermediate formation of N^α,N^ω-bis(6-halopyridin-2-yl)polyamines or via 2,6-bis(polyamino)substituted pyridines. The yields of linear and cyclic products were shown to be strongly dependent on the nature of the starting polyamines and that of the halogen atom.     

Synthesis, coordination properties, and analytical applications of mixed donor macrocycles containing the 1,10-phenanthroline sub-unit

The coordination properties towards different metal ions of a new class of mixed N/S-, and N/S/O-donor macrocycles containing the 1,10-phenanthroline sub-unit in the cyclic framework are reviewed. The conformational constraints imposed by the heteroaromatic fragment onto the aliphatic portion of the ring determine the coordination mode of these ligands which can stabilise low-valent Ni⁺, Pd⁺, Pt⁺, and Rh⁺ metal complexes. Structural and thermodynamic aspects of the coordination chemistry of these ligands are considered together with possible applications as building blocks in the synthesis of multi-centred systems, and as template in the construction of extended polyiodide networks. However, solution studies demonstrate the inability of these ligands to work as selective and specific fluorescent chemosensors for heavy transition and post-transition metal ions and the formation constants evaluated for the formation of 1:1 complexes with Pb²⁺, Cd²⁺, Hg²⁺, Cu²⁺, and Ag⁺ in acetonitrile are of the same order of magnitude. Nevertheless, some of these macrocyles are extremely effective to recognise Cu²⁺ or Ag⁺ over the other metal ions in transport processes, and have been successfully used as neutral ionophore in the construction of PVC-based ionselective electrodes and supported liquid membranes for analytical detection and separation, respectively, of these metal ions.     

Synthesis and properties of template-promoted switchable dithienylethenebased macrocycles

Three switchable macrocycles based on photochromic dithienylethene were synthesized under the template of dibenzylammonium hexafluorophosphate. Their structure were well-confirmed by NMR, ESI-MS and X-ray diffraction. Their photochromism indicated that they showed good reversibility in solution. Additionally, the theoretical calculation suggested that photoirradiation can change the cavity of macrocycles.     

芳炔类共轭大环化合物

芳炔类大环化合物是最近10年来新兴的一种富碳共轭大环状分子，迅速发展到 近100种，可在光、电、磁、纳米等功能材料中得到广泛应用，引起了人们极大的 兴趣，对芳炔类大环化合物的研究，特别是合成方法和性质进行了综述，并提出了 这一领域的发展方向和需要解决的重点课题。     

Synthesis and chiroptical properties of two new planar-chiral macrocycles

Could simple intraannular-arm macrocyclic systems exist in enantiopure stable forms? The effective synthesis of two representative compounds of such a class, their resolution into enantiomers, and experiments justifying their stability toward racemization are presented.     

Synthesis of highly functionalized macrocycles by the peripheral functionalization of macrocyclic diimines

The easily available macrocyclic diimines 4-7 can be stereoselectively transformed to macrocyclic bis-beta-amino acids 13-17, macrocyclic bisazetidines 18-20, and macrocyclic bisamides 21 and 22 by means of the corresponding bis-beta-lactam scaffolds 8-12. These key intermediates are available through standard Staudinger reaction and obtained as the cis-cis diastereomers, exclusively. An interesting relation between the proximity of the reactive C=N bonds and the selectivity in the formation of the bis-beta-lactams 8-12 is observed. Thus, diimine 4 leads to low selectivities, producing a 1:1 mixture of cis-syn-cis and cis-anti-cis diastereomers, while diimines 5-7 having the diimine sites more separated lead almost exclusively to the cis-anti-cis diastereomers. The stereochemistry of all the products was unambiguously assigned by X-ray diffraction analysis of compounds cis-syn-cis 8 and cis-anti-cis 12-Co2CO6 complex.     

Synthesis and ionophore properties of a series of new tetrapyrazolic macrocycles

The synthesis of several macrocycles containing two bipyrazolic subunits, with different cavity sizes and with donor-group-bearing side arms attached, is reported. Their alkali cation binding ability has been studied from two aspects : extraction and transport through an artificial liquid membrane. Macrocycles described here show a high selectivity towards Li⁺ and Na⁺ cations; furthermore one of them is remarkably well adapted to extract selectively and to transport efficiently the lithium cation in competitive conditions.     

Synthesis of nitrogen- and oxygen-containing macrocycles with several polyamine and anthracene or anthraquinone fragments in reactions of palladium-catalyzed amination

Palladium-catalyzed amination of 1,8-dichloroanthracene and 1,8-dichloroanthraquinone with polyamines made it possible to synthesize bis(haloaryl)-substituted polyamines and oxadiamines, 1,8-bis-(polyamino)substituted anthracenes and anthraquinones. The dependence of the yield of synthesized main and side products on the reaction conditions and on the nature of initial compounds was investigated. The cyclization of compounds obtained was performed leading to cyclodimers and cyclotrimers, and the limitations of this method were established. A possibility was examined of preparation of N,N-diarylated polyamines derivatives in reactions with excess 1,8-dichloroanthracene or 1,8-dichloroanthraquinone.     

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.     

Synthesis and characterisation of tetra-tetrazole macrocycles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl-chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of the previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl-chain linker, the relative orientation of the tetrazole rings on the benzene ring and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene ring are prevented from becoming co-planar on intramolecular (steric) grounds. In the 1,3- and 1,4-bis(tetrazole)benzene derivatives, there is no such impediment, and a co-planar arrangement is observed where intra- and/or intermolecular stacking interactions exist. Deviations from co-planarity are associated with optimisation of intermolecular interactions between the tetrazole rings and adjacent alkyl chains. In the macrocycle based on 1,4-bis(tetrazole)benzene with four-carbon linkers, an intramolecular stacking interaction exists, which precludes the presence of any cavity. In the macrocycle based on 1,3-bis(tetrazole)benzene with six-carbon linkers, a cavity of 10.8×9.4 Å is observed for each molecule in the solid state, although the packing of adjacent molecules is such that there are no extended channels running through the crystal.     

Influence of highly preorganised 7,7-diphenylnorbornane in the free energy of edge-to-face aromatic interactions

The influence of preorganised 7,7-diphenylnorbornane in the stability (Ka) of host-guest complexes as well as in the determination of the energy of edge-to-face aromatic interactions has been investigated. The guest molecules studied bind more strongly with hosts that contain the cofacial 7.7-diphenylnorbornane subunit than with similar hosts that have a 1,1-diphenylcyclohexane subunit. On the other hand, the value of the edge-to-face aromatic interactions calculated for our complexes (-0.2 +/- 0.6 kJmol(-1)) is significantly lower (by a factor of seven) than the one previously reported in the literature. This result highlights the importance of entropic factors in the determination of weak noncovalent interactions.     

芳香寡聚酰胺大环化合物的合成

通过芳香二胺单体1和二酸酰氯单体2的一步环化反应合成了酰胺键上的氢原子被2,4-二甲氧基苄基部分取代的一系列新型的芳香酰胺八聚体大环化合物3, 这些带有不同R基团环状八聚体的结构得到了核磁、高分辨质谱和MALDI-TOF的确认.     

Synthesis, crystal structures and photochromic properties of novel chiral Schiff base macrocycles

Enantiomerically pure and racemic forms of calixsalen-type macrocycles 1 and 2 were synthesized and their crystal structures were determined. The enantiomerically pure crystals of (S,S,S,S,S,S)-1 exhibited thermally reversible photochromism from yellow to orange-red upon photoirradiation in the solid state, while rac-crystals of 2 with the guest CH₃CN did not show any photocolouration.     

Self-assembled ring-in-ring complexes from metal-ligand coordination macrocycles and β-cyclodextrin

Ring-in-ring nanostructures can be assembled from readily available starting materials, including dipyridyl ligands, (en)Pd(NO₃)₂, and β-cyclodextrin (β-CD). When a series of dipyridyl ligands are mixed with β-CD and Pd(II) in aqueous solution, various self-assembled geometries can be obtained as a result of a combination of hydrobic interactions and metal-ligand coordinations. In the cases of dipyridyl ligands with flexible linker, dinuclear coordination macrocycles M₂L₂ are formed and included in the cavity of β-CD to form ring-in-ring complexes. When more rigid dipyridyl ligands are used, a tetranuclear coordination macrocycle M₄L₄ prevails and shows no interaction with β-CD, as apposed to the flexible ones.     

Synthesis and characterization of cationic iodonium macrocycles

A synthetic strategy for the high-yield preparation of iodonium containing macrocycles such as rhomboids, a square, and a pentagon is described, with the long-term objective of preparing iodonium compounds for potential molecular electronics applications. Two cationic rhomboid shaped molecules were prepared for the first time (55-70%) by the treatment of compounds 11 and 12a or 12b with Me3SiOTf. The reaction of dication 8 with 6 in the presence of Me3SiOTf gave an iodonium containing molecular square in 70% yield. In addition, a pentagon-shaped macromolecule was prepared in 60% yield. These iodonium-containing charged macromolecules were characterized by multinuclear NMR, mass spectrometry, and physical means.     

Synthesis and properties of highly lipophilic phosphazene bases

Twelve novel phosphazene bases (X-C₆H₄-NN-C₆H₄-NPR₃) with an unusual combination of properties – high lipophilicity of both neutral and charged forms, lack of localized charges in the cations, and strong spectral changes upon protonation/deprotonation – were synthesized using the Staudinger reaction and characterized by UV–Vis spectra, pK_a values and lipophilicities (logP values). The bases could potentially be useful as working agents in optical sensors and acid-base indicators for lipophilic membranes.     

Entropy directs the self-assembly of supramolecular palladium coordination macrocycles and cages

The self-assembly of palladium-based cages is frequently rationalized via the cumulative enthalpy (ΔH) of bonds between coordination nodes (M, i.e., Pd) and ligand (L) components. This focus on enthalpic rationale limits the complete understanding of the Gibbs free energy (ΔG) for self-assembly, as entropic (ΔS) contributions are overlooked. Here, we present a study of the M₂^linL₃ intermediate species (M = dinitrato(N,N,N′,N′-tetramethylethylenediamine)palladium(ii), ^linL = 4,4′-bipyridine), formed during the synthesis of triangle-shaped (M₃^linL₃) and square-shaped (M₄^linL₄) coordination macrocycles. Thermochemical analyses by variable temperature (VT) ¹H-NMR revealed that the M₂^linL₃ intermediate exhibited an unfavorable (relative) ΔS compared to M₃^linL₃ (triangle, ΔTΔS = +5.22 kcal mol⁻¹) or M₄^linL₄ (square, ΔTΔS = +2.37 kcal mol⁻¹) macrocycles. Further analysis of these constructs with molecular dynamics (MD) identified that the self-assembly process is driven by ΔG losses facilitated by increases in solvation entropy (ΔS_solv, i.e., depletion of solvent accessible surface area) that drives the self-assembly from “open” intermediates toward “closed” macrocyclic products. Expansion of our computational approach to the analysis of self-assembly in Pd_n^benL_2n cages (^benL = 4,4''-(5-ethoxy-1,3-phenylene)dipyridine), demonstrated that ΔS_solv contributions drive the self-assembly of both thermodynamic cage products (i.e., Pd₁₂^benL₂₄) and kinetically-trapped intermediates (i.e., Pd₈^cL₁₆).

These studies demonstrate that ΔS drives the self-assembly of supramolecular palladium-based coordination macrocycles and cages. As this ΔS contribution arises from solvation, these findings broadly reflect the thermodynamic drive of self-assembly to form compact structures.