Highly Efficient Synthesis of Novel Poly-aza Bis-histidines

A series of novel poly-aza bis-histidines with much potential in medicinal, bioinorganic, bioorganic, biomimetic and supramolecular chemistry were synthesized conveniently, efficiently and readily in excellent yields from commercial histidine. The low temperature in the reaction of the protected histidine with poly-aza diamine 5 is key condition for the selective preparation of target compounds with high yields.     

Self-assembly of hollow cones in a bola-amphiphile/hexadiamine salt solution

Cones are a very rare form of supramolecular self-assembly. It is shown that mixing of an unsymmetrical bola-fatty acid and a diamine (catanionic system) in dilute solutions can produce aggregates having a conical shape. These assemblies are made of frozen unsymmetrical monolayers in which bolas are arranged on a regular hexagonal lattice. Cones are stabilized by the introduction of pentagonal or n-gonal defects in the bola-lattice which yields the quantification of the cone apex angle according to the Euler theorems. The formation of cones represents a novel route for lipid and surfactant systems to minimize the edge energy of a flat membrane.     

Supramolecular adducts of mesocyclic diamines with various carboxylic acids: Charge-assisted hydrogen-bonding in molecular recognition

Aggregation of saturated mesocyclic diamine 1,4-diazacycloheptane (dach) or piperazine (pipz) and diversiform carboxylic acids with mono- or di-carboxyls yields a series of novel binary supramolecular adducts via two-point molecular recognition. All the supramolecular assemblies were obtained by solvent evaporation method from different media. X-ray single-crystal diffraction analyses reveal that these supramolecular moieties present 1D chain motif, 2D flat, corrugated sheet structures and 3D CdSO₄, pillar-layered networks through carboxylate-amide N–H⋯O, as well as its proton transfer form N⁺–H⋯O⁻, carboxyl head to tail O–H⋯O, and extended hydrogen-bonding interactions. Their compositions and structures were also confirmed by Fourier transform infrared (FT-IR) spectroscopy. Thermal stability of these binary crystalline adducts has been investigated by thermogravimetric analysis (TGA), suggesting similar thermal stabilities.     

Microwave-assisted synthesis of pyrazolyl bistriazines

Reaction of 6-chloro-N,N′-bispyrazolyl-[1,3,5]triazine-2,4-diamines with 4-aminobenzylamine under microwave irradiation produces bistriazines in excellent yields. The use of a diamine bearing amino groups with different reactivities allowed the reaction to be carried out in two steps and selectively gave monotriazines, bistriazines with identical substituents and differently substituted bistriazines. The structures of these new compounds have been studied by NMR spectroscopy, mass spectrometry and in one case by X-ray crystallogrphy. These new bistriazines have promising applications in supramolecular chemistry based on hydrogen bonds and/or complexation with metals. The presence of a rigid linker can be used for the efficient preparation of extended supramolecular polymers with interesting fluorescence properties by complexation with cyanuric and barbituric acid derivatives.     

Supramolecular control for the modular synthesis of pseudopeptidic macrocycles through an anion-templated reaction

The anion-templated synthesis of different pseudopeptidic macrocycles has been studied in detail by using a multidisciplinary approach. The reaction between an open-chain pseudopeptidic diamine and the appropriate dialdehyde is highly affected by the presence of the best fitting anionic template. The formation of the corresponding macrocyclic tetraimino-template supramolecular complex is demonstrated by NMR (ROESY and PGSE) and mass spectrometry (ESI-TOF). These supramolecular complexes can be easily reduced to the corresponding more stable tetraamine macrocycles. Accordingly, we have used this reaction to efficiently synthesize a family of new pseudopeptidic macrocycles in a one-pot two-steps anion-templated reductive amination reaction, which comprises a multicomponent macrocyclization through the selective formation of four chemical bonds to yield a unique macrocyclic structure. Different variables like the aliphatic spacer between amino acidic moieties, geometry of the dialdehyde, and structure of the amino acid side chains were thoroughly studied, and their effect in the formation and stability of the supramolecular complexes discussed. The conformational preorganization induced by the template has been monitored by circular dichroism, reflecting the differences observed in the isolated yields, as well as by NMR spectroscopy. This effect has been also supported by molecular modeling. All the experimental and theoretical techniques were strongly consistent and reflected the same trends by comparing the different structural variables introduced in the system.     

Synthesis of Linear Amphipathic Porphyrin Dimers and Trimers: An Approach to Bilayer Lipid Membrane Spanning Porphyrin Arrays

A modular building-block approach has been developed for the construction of linear amphipathic porphyrin arrays. The reaction of meso-(trifluoromethyl)dipyrromethane and an aldehyde under the conditions of the two-step room temperature porphyrin synthesis affords the trans-substituted porphyrin (13-56% yields). A similar reaction with two different aldehydes provides access to porphyrins bearing two different functional groups. An ethyne porphyrin and an iodo porphyrin (either free base or zinc) are selectively joined via Pd(0)-catalyzed coupling reactions, affording a linear array with porphyrins in defined metalation states. Coupling of a zinc-porphyrin bearing iodo and ester groups with a free base porphyrin bearing ethyne and ester groups yielded the zinc-free base porphyrin dimer. Coupling of a bis-ethyne porphyrin with a porphyrin bearing iodo and ester groups afforded the porphyrin trimer. Cleavage of the esters yielded the amphipathic porphyrin dimer and trimer arrays. The arrays with adjacent zinc and free base porphyrins undergo efficient electronic energy transfer. Both amphipathic porphyrin arrays have been incorporated into L-alpha-phosphatidylcholine vesicles. This versatile synthetic strategy provides access to a family of porphyrin arrays for studies of photophysical processes in supramolecular assemblies.     

Supramolecular squares of porphyrazines

The design, self-assembly, and characterization of discrete arrays of porphyrazine (Pz) squares are presented to illustrate the supramolecular chemistry of these macrocycles, and to highlight that these arrays have physical chemical properties that are different from similar arrays of porphyrinic systems.     

Tessellation of porphyrazines with porphyrins by design

The efficient self-assembly and functional characterization of arrays containing multiple types of chromophores will provide a basis for the design and applications of functional photonic materials that are unobtainable using only one type of molecule. The design, synthesis, and characterization of supramolecular systems bearing two different types of porphyrinic chromophores, porphyrins and porphyrazines, are reported. Because the porphyrins and porphyrazines bear different exocyclic ligands for self-assembly by metal ion coordination, these systems require new supramolecular synthetic strategies wherein reactants are added in a specific order. These arrays display unique photophysical properties derived from the component chromophores, the metal geometry, and the supramolecular nanoarchitecture.     

界面超分子聚合

超分子聚合物诞生于高分子化学与超分子化学的交叉融合,一般是指单体间通过非共价键作用连接形成的聚合物,并在溶液或体相中表现出类似聚合物的性质。目前超分子聚合物一般通过均相溶液聚合制备得到,但溶液中的超分子聚合是一个自发的组装过程,具有浓度依赖性,组装过程不易可控。为解决此问题,研究人员可以将超分子聚合从均相溶液转移到界面,在界面上可控地制备超分子聚合物。通过界面聚合制备超分子聚合物具有一些独特的优势,如可以制备得到分子量更高的超分子聚合物,易于制备一些缺陷少、面积大、有序的二维超分子聚合物等。本文基于在液-液、气-液和固-液三种界面上制备超分子聚合物的一些代表性工作,介绍了界面超分子聚合方法和应用,并展望其未来发展。     

Visualization of various supramolecular assemblies of oligo(para-phenylenevinylene)-melamine and perylene bisimide

A melamine derivative has been covalently equipped with two oligo(para-phenylenevinylene) (OPV) chromophores. This procedure yields a bifunctional molecule with two hydrogen-bonding arrays available for complementary binding to perylene bisimide derivatives. Depending on the solvent, hydrogen-bonded trimers, tetramers, and dimers on a graphite surface are observed for pure OPV-melamine by using scanning tunneling microscopy (STM). Upon the addition of perylene bisimide, linear tapes of perylene bisimide, 12-membered rosettes that consist of alternating hydrogen-bonded OPV-melamine and perylene bisimide moieties are visualized. These results provide direct evidence for the possible modes of hydrogen bonding within a supramolecular co-assembly in solution. Subsequently, the optical properties of pure OPV-melamine and co-assemblies with a perylene bisimide derivative were characterized in solution. In an apolar solvent, OPV-melamine self-assembles into chiral superstructures. Disassembly into molecularly dissolved species is reversibly controlled by concentration and temperature. Complementary hydrogen bonding to a perylene bisimide derivative in an apolar solvent yields multicomponent, pi-stacked dye assemblies of enhanced stability that are characterized by fluorescence quenching of the constituent chromophores. Titration experiments reveal that a mixture of hydrogen-bonded oligomers is present in solution, rather than a single discrete assembly. The solution experiments are consistent with the STM results, which revealed various supramolecular assemblies. Our system is likely not to be optimally programmed to obtain a discrete co-assembled structure in quantitative yield.     

Controlled synthesis of ruthenium phthalocyanines and their use in the construction of supramolecular arrays

(Monocarbonyl) and bis(benzonitrile)ruthenium phthalocyanines, conveniently prepared from metal-free phthalocyanine precursors, are used as supramolecular building-blocks in the construction of phthalocyanine-porphyrin multi-chromophore arrays.     

Chiroptical nanofibers generated from achiral metallophthalocyanines induced by diamine homochirality

Optically active cofacial π-π phthalocyanine (Pc) stacked supramolecules were spontaneously and successfully generated from a mixture of four possible geometric isomers (C(4h), D(2h), C(2v), C(s)) of achiral 4(5),4'(5'),4'(5'),4'(5')-tetracarboxymetallophthalocyanine (tcPcM; M=Ni, Cu) induced by an equimolar amount of inexpensive chiral diamine molecular sources in DMSO/CHCl(3) mixed solvent under optimized conditions of the volume ratio of poor/good cosolvents, the molar ratio of chiral molecular diamine to tcPcM, the cavity metal of phthalocyanine, and the addition order of the amines. The sign and amplitude of circular dichroism spectra due to the supramolecular chirality and structure of the diamine molecules are impossible to remove by additions of the antipode diamine and trifluoroacetic acid. The chiral diamine was partly contained in nanofibers, and that retained in the solution can be recycled and reused to induce optically active tcPcM supramolecules.     

Grid-type metal ion architectures: functional metallosupramolecular arrays

Recent advances in supramolecular coordination chemistry allow access to transition-metal complexes of grid-type architecture comprising two-dimensional arrays of metal ions connecting a set of organic ligands in a perpendicular arrangement to generate a multiple wiring network. General design principles for these structures involve the thermodynamically driven synthesis of complex discrete objects from numerous molecular components in a single overall operation. Such supramolecular metal ion arrays combine the properties of their constituent metal ions and ligands, showing unique optical, electrochemical, and magnetic behavior. These features present potential relevance for nanotechnology, particularly in the area of supramolecular devices for information storage and processing. Thus, a dense organization of addressable units is represented by an extended "grid-of-grids" arrangement, formed by interaction of grid-type arrays with solid surfaces.     

Assemblies of supramolecular porphyrin dimers in pentagonal and hexagonal arrays exhibiting light-harvesting antenna function

Porphyrin-based supramolecular macrocyclic arrays were synthesized as mimics of photosynthetic light-harvesting (LH) antennae. Pentameric and hexameric macrocyclic porphyrin arrays EP5 and EP6 were constructed by complementary coordination of m-bis(ethynylene)phenylene-linked zinc-imidazolylporphyrin Zn-EP-Zn. The proton NMR spectra of noncovalently linked N-EP5 and N-EP6 indicate fast rotation of the porphyrin moieties along the ethyne axis. These macrocycles were covalently linked and identified as C-EP5 (6832 Da) and C-EP6 (8199 Da) by mass spectrometry. Fluorescence quantum yields of C-EP2 (10.0%), C-EP5 (10.1%), and C-EP6 (11.0%), even larger than that of the unit coordination dimer C-EP1 (9.3%), were significantly increased from those of the series without the ethynylene linkage. The order of increasing fluorescence quantum yields was parallel to that of decreasing fluorescence lifetimes (C-EP1 (1.65 ns), C-EP2 (1.45 ns), C-EP5 (1.42 ns), and C-EP6 (1.38 ns)), indicating that the radiative decay rate kF increased relative to the other decay rates with an increase in the number of ring components. Based on the exciton-exciton annihilation and anisotropy depolarization times, the excitation energy hopping (EEH) times in these macrocyclic systems were obtained as 21 ps for C-EP5 and 12.8 ps for C-EP6. EEH times depend strongly on the orientation factor of the component transition dipoles in the macrocyclic arrays. The hexagonal macrocyclic array with an orientation of better transition dipole coupling resulted in faster EEH time compared to the pentagonal one.     

Bifunctional catalysis of Morita-Baylis-Hillman (MBH) reaction with chiral primary-tertiary diamine: A non-typical MBH catalytic pathway

A simple primary-tertiary diamine has been explored as a novel catalyst for the Morita-Baylis-Hillman reaction of MVK and aryl aldehydes, and moderate to good chemical yields were obtained. Detailed mechanism study indicated that the diamine acted as a bifunctional cooperation catalyst via a bicyclic enamino-quaternary ammonium intermediate.     

Hooking Together Sigmoidal Monomers into Supramolecular Polymers

Supramolecular polymers show great potential in the development of new materials because of their inherent recyclability and their self‐healing and stimuli‐responsive properties. Supramolecular conductive polymers are generally obtained by the assembly of individual aromatic molecules into columnar arrays that provide an optimal channel for electronic transport. A new approach is reported to prepare supramolecular polymers by hooking together sigmoidal monomers into 1D arrays of π‐stacked anthracene and acridine units, which gives rise to micrometer‐sized fibrils that show pseudoconductivities in line with other conducting materials. This approach paves the way for the design of new supramolecular polymers constituted by acene derivatives with enhanced excitonic and electronic transporting properties.     

Substituent control over dimerization affinity of triply hydrogen bonded heterodimers

Linear arrays of hydrogen bonds represent important elements of the supramolecular toolkit for receptor design, assembly of supramolecular polymers, and other well-defined supramolecular structures. It is illustrated that remote substituent effects control dimerization affinity in a predictable manner using a conformer independent ureidoimidazole DDA motif and its amidoisocytosine based AAD partner.     

Copper‐Catalyzed Intramolecular Desymmetric Aryl C?O Coupling for the Enantioselective Construction of Chiral Dihydrobenzofurans and Dihydrobenzopyrans

O‐Heterocyclic structures such as 2,3‐dihydrobenzofurans are key motifs in many natural compounds and pharmaceuticals. Enantioselective formation of chiral dihydrobenzofurans and analogues was achieved through a copper‐catalyzed desymmetrization strategy with a chiral cyclic 1,2‐diamine. A broad range of substrates are compatible with this Cu^I‐diamine catalytic system and afford the desired coupling products with chiral tertiary or quaternary carbon centers in high yields and good to excellent enantioselectivities under mild conditions.     

Copper‐Catalyzed Intramolecular Desymmetric Aryl CO Coupling for the Enantioselective Construction of Chiral Dihydrobenzofurans and Dihydrobenzopyrans

O‐Heterocyclic structures such as 2,3‐dihydrobenzofurans are key motifs in many natural compounds and pharmaceuticals. Enantioselective formation of chiral dihydrobenzofurans and analogues was achieved through a copper‐catalyzed desymmetrization strategy with a chiral cyclic 1,2‐diamine. A broad range of substrates are compatible with this Cu^I‐diamine catalytic system and afford the desired coupling products with chiral tertiary or quaternary carbon centers in high yields and good to excellent enantioselectivities under mild conditions.