Self-assembled Supramolecular Architectures Research Articles

Novel self-assembled supramolecular architectures of Mn(ii) ions with a hybrid pyrazine–bipyridine ligand

A new hybrid pyrazine-bipyridine ligand L (C26H20N6) and its complexes with Mn(NO3)2, Mn(ClO4)2, MnCl2 and MnBr2 have been synthesised. By the self-assembly of L and Mn(II) ions three different kinds of supramolecular complexes have been obtained: binuclear baguette complex [Mn2L(H2O)6](NO3)4·2.5H2O 1 and tetranuclear [2 × 2] grid-type complex [Mn4L4](ClO4)8·2.5(CH3CN)·2CH3OH 2 and mononuclear complexes [MnL2]X2 (where X = Cl(-)3 and X = Br(-)4). Crystal structures and magnetic properties of Mn(II) complexes 1 and 2 have been also investigated. The crystal structures reveal that in both 1 and 2 complexes the Mn(II) ions have coordination number 6 and distorted octahedral coordination geometry. In 2 four metal cations and four ligands have assembled into a grid-type [2 × 2] array, with a perchlorate anion occupying the central cavity, with clearly a good fit for the center of the cavity. The perchlorate anion, in contrast to the nitrate anion, probably acts as a template in the formation of tetranuclear grid-type complexes. Magnetic susceptibility measurements indicate that the Mn(II) ions are all high spin, and in both 1 and 2 complexes there are weak antiferromagnetic interactions between Mn(II) ions.

A unique non-catenane interlocked self-assembled supramolecular architecture and its photophysical properties.

A novel, interlocked, self-assembled (M(2)L(2))(2) molecular architecture was constructed from an arene-Ru acceptor and a 1,4-di(pyridin-4-yl)buta-1,3-diyne donor. Two M(2)L(2) units, with cavities of ~7.21 Å, spontaneously interlock, with one unit encapsulating a twin in a non-catenane fashion. The dimeric host-guest complex thus formed is unique among two-dimensional self-assemblies and is stabilized by π-π interactions between the M(2)L(2) units.

Self-assembled supramolecular architecture with alternating porphyrin and phthalocyanine, bonded by hydrogen bonding and π–π stacking

5, 10, 15, 20-tetraphenyl porphyrinato manganese (III) (MnTPP) ligated by THF in opposite axial directions and a sixcoordinate phthalocyaninato cobalt (II) (CoPc) with 1-phenyl-1H-tetrazole-5-thiol (HL) molecules as axial ligands were self-assembled in a mixed solution of tetrahydrofuran and acetone ( v/ v = 1:1) to form a hydrogen bonding “polymer” alternated with porphyrin (Por) and phthalocyanine (Pc) molecules, MnTPP(THF) 2CoPc(L) 2( 1). The hydrogen bonding interaction was contributed by nitrogen [in the axial ligand (L −) of phthalocyanine] and hydrogen atom (in a peripheral phenyl around the porphyrin ring). This hydrogen bonding “polymer” was also enhanced by π–π stacking of the tetrazole in L − with both TPP and Pc macrocycles. These polymer chains were constructed into their three-dimension (3D) architecture only by Van der Waal’s attractions. Crystal data for 1 indicate a triclnic system of P-1. Unit cell: a = 11.3932(8) Å, b = 12.6462(9) Å, c = 14.4939(11) Å, α = 91.1970(10)°, β = 95.5050(10)°, γ = 90.7200(10)°, and with cell volume of 2078.0(3) Å 3.

Breath figure fabrication of honeycomb films with small molecules through hydrogen bond mediated self-assembly

Honeycomb films fabricated with small molecules via the breath figure (BF) method are reported. Water droplet templates were stabilized by self-assembled supramolecular architectures and a subsequent gelation process. The formed honeycomb film features a hydrogen bonded network of a dynamic nature.

Optical modulation of supramolecular assembly of amphiphilic photochromic diarylethene: from nanofiber to nanosphere

A diarylethene derivative with histamines as side chains was synthesized and the morphology of self-assembled supramolecular architecture can be tuned from nanofiber to nanosphere by photo irradiation. The theoretical calculation and model of the self-assembled nanostructure are presented to illuminate the possible self-assembly mechanism.

Understanding Cooperativity in Hydrogen-Bond-Induced Supramolecular Polymerization: A Density Functional Theory Study

Understanding the molecular mechanism of cooperative self-assembly is a key component in the design of self-assembled supramolecular architectures across multiple length scales with defined function and composition. In this work, we use density functional theory to rationalize the experimentally observed cooperative growth of C(3)-symmetrical trialkylbenzene-1,3,5-tricarboxamide- (BTA-) based supramolecular polymers that self-assemble into ordered one-dimensional supramolecular structures through hydrogen bonding. Our analysis shows that the cooperative growth of these structures is caused by electrostatic interactions and nonadditive effects brought about by redistribution of the electron density with aggregate length.

Coordination assembly of p-substituted aryl azo imidazole complexes: Influences of electron donating substitution and counter ions

Abstract The formation of a series of Cu(II), Zn(II) and Cd(II) complexes using the p-substituted aryl azo system has been reported. Presence of electron donating –Me, –OMe groups impart some unusual coordination behaviors in Cu(II) complexes. Varying coordination mode and electron density in the ligand results in the formation of an unusual Cu–S bond in complex 1 and an unusual equatorial coordination of H2O in Cu(II) complex 2 with a square-pyramidal geometry. The hydrogen bonding site along with the metal coordination site in the ligand results in the formation of higher dimensional self-assembled supramolecular architectures. Compatibility of the hard–soft nature of the metal ion and symbiosis effect of the ligand with metal is responsible for the formation of long range higher dimensional networks in the solid-state, which were confirmed by single crystal X-ray structure analysis. Furthermore, various physicochemical studies, viz. thermal behaviors, absorption spectra, electrochemistry and EPR studies, have been conducted to rationalize the structures in the solution phase.

Molecular to Supramolecular Structure: Influence of Coordination Environment in Azo-dye Complexes

The mixed donor ligand 2-(phenylazo)imidazole (L 1 ) forms a family of seven different metal complexes of varying coordination environments at the molecular level. The presence of hydrogen bonding sites along with metal coordination sites results in the formation of three-dimensional (3D) self-assembled supramolecular architectures. Variation of the 3D architecture is a consequence of fine-tuning of the coordination behavior of the mixed donor ligand. Compatibility of the hard-soft nature of the metal ion and the mixed donor Li controls the long-range 3D order in the solid-state. The solid-state structures of L 1 and their complexes were identified by single crystal X-ray structure analysis. The optical, electrochemical, and thermal properties of azodyes and their metal complexes were studied in detail and compared with their molecular structures.

Rufigallol-based self-assembled supramolecular architectures

Discotic liquid crystals have been attracting growing interest not only because of the fundamental importance as model systems for the study of charge and energy transport but also due to their potential application in organic electronic devices. The 1,2,3,5,6,7-hexahydroxy-9,10-anthraquinone, commonly known as rufigallol, is one of the earliest systems reported to form columnar mesophases. Over the past 25 years, more than 100 discotic liquid crystals based on this core have been realized and studied for various physical properties. This review summarizes synthesis and thermal behaviour of all these materials. A brief summary of various physical studies on these materials has also been given.

Self-assembled tetrapyrrole–fullerene and tetrapyrrole–carbon nanotube donor–acceptor hybrids for light induced electron transfer applications

This review article highlights the recent progress made in the design and study of self-assembled supramolecular architectures based on tetrapyrrole macrocycles as donors, and fullerene and carbon nanotubes as electron acceptors for electron and energy transfer applications in solution. The remarkable features of the utilized biomimetic organization principles viz., hydrogen bonding, π–π stacking, metal-mediated complexation, and electrostatic attraction in governing the stability and geometry of the nanohybrids, and their significance in controlling the structure and electron transfer properties are discussed.

Self-Assembly of Supramolecular Architectures Using Chlorotetra(Pyrrole-2-Carboxylato)Diruthenium Molecules as Building Blocks

Two new complexes, based on the unit Ru2Cl(μ-O2CC4H4N)4 (1) (O2CC4H4N = pyrrole-2-carboxylate), Ru2Cl(μ-O2CC4H4N)4(H2O)·4H2O [1(H2O)·4H2O], and Ru2Cl(μ-O2CC4H4N)4(Me2CO) [1(Me2CO)], are synthesized and structurally characterized. The physical properties of these complexes are studied and compared with those previously reported for Ru2Cl(μ-O2CC4H4N)4(thf)·thf·H2O [1(thf)·thf·H2O]. The nature of the solvent molecule bonded to the axial position of the dimetallic unit determines the supramolecular interactions leading to different arrangements in the solid state. The presence of NH groups in the pyrrolic rings favours the existence of hydrogen bond interactions that are present in the three complexes. In addition, complex 1(Me2CO) shows π–π stacking interactions through pyrrolic rings of different dimetallic units.

Matrix-molecule induced chiral enhancement effect of binary supramolecular liquid crystals

Chiral enhancement effects associated with supramolecular liquid crystalline structures are studied, using a complex of achiral molecules (4,4′-bipyridine, 4Bpy) and chiral cholesteric liquid crystalline molecules (3-cholesteryloxycarbonylpropanoic acid, C4) as the model system. Non-mesogenic achiral molecule 4Bpy is used as the matrix element. The chiral enhancement of the supramolecular liquid crystalline structures can be revealed by circular dichroism (CD) and helical twisting power measurements. It is interesting that CD spectra of the complex exhibited an appreciably enhanced chiral property in comparison with that of the pure chiral cholesteric C4 molecules at room temperature. The helical pitch measurements by the Grandjean–Cano method also confirm the chiral enhancement effect. In addition, polarizing optical microscopy (POM) measurements indicate that the addition of matrix molecules leads to the explicit expression of the chiral liquid crystalline texture, i.e. twisted grain boundary (TGBA*) phase, at the liquid crystal temperature. Differential scanning calorimetry (DSC) and variable-temperature X-ray diffraction measurements further confirm the existence of the TGBA* phase. The binary supramolecular assembly structures are investigated by scanning tunneling microscope (STM) and the formation of hydrogen bonds between the chiral mesogens and the achiral matrix molecules can be directly observed. The variable-temperature Fourier transform infrared (FTIR) results further demonstrate that the hydrogen bonds persist until 168 °C. These results indicate that the introduction of a bifunctional aromatic base such as bipyridine could lead to self-assembled supramolecular architectures with discernible enhancements of chiral properties.

Bioengineering polyfunctional copolymers. VII. Synthesis and characterization of copolymers of p-vinylphenyl boronic acid with maleic and citraconic anhydrides and their self-assembled macrobranched supramolecular architectures

New boron-containing anion active functional copolymers are synthesized by complex-radical copolymerization of 4-vinylphenyl boronic acid and maleic or citraconic anhydrides with 2,2′-azobisisobutyronitrile as an initiator in DMF at 70 °C under nitrogen atmosphere. Macrobranched derivatives of these copolymers are synthesized by the partial grafting with α-hydroxy,ω-methoxy-poly(ethylene oxide) and incorporation with poly(ethylene imine). Effect of H-bonding on the formation of self-assembled supramolecular macrocomplexes with higher crystallinity and thermal stability was observed and confirmed by FTIR, and 1H( 13C DEPT-135( NMR spectroscopy, X-ray diffraction, DSC and TGA analyses of monomer, homopolymer, copolymer and grafted copolymer systems. Observed water solubility, biocompatibility and high density of acid groups in macromolecules allow these anion active B-containing copolymer systems for the developing new generation of effective antitumor agents, polymeric carriers for enzymes, gene delivery and boron neutron capture therapy.

Synthesis, crystal structures and luminescent properties of two supramolecular assemblies containing [Au(CN)2]? building block

Two self-assembled supramolecular architectures {{MnH2O(Phen)2[Au(CN)2]}[Au(CN)2]·0.5C2H5OH·0.5H2O}n (phen = 1, 10-phenanthroline) (1) and [C6H13N4][Au(CN)2]·H2O(C6H13N4 = 4-amide-3, 5-diethyl-1, 2, 4-triazole cation) (2) have been synthesized and structurally characterized. X-ray crystallography revealed a three-dimensional structure of 1 formed by the incorporation of coordinative linkage, aurophilic, hydrogen-bonding and π–π interactions. The 2D structure of 2 is formed by aurophilic and hydrogen-bonding interactions. Both the solid phases and aqueous solutions of 1 and 2 display interesting luminescence at room temperature.

A novel self-assembled supramolecular architecture involving cation, anion and a calix[4]arene heteroditopic receptor

In the presence of potassium acetate the heteroditopic calix[4]arene receptor 1 , in the 1,3- alternate structure and bearing two pentafluorophenyl amide groups as anion binders and a crown-5 polyether for cation complexation, self-assembles in an unexpected 2:2:2 (calixarene:cation:anion) supramolecular structure, as shown by X-ray crystal structure.

From liquid crystal polymers containing crown ethers to tapered building blocks containing crown ethers which self‐assemble into tubular supermolecules

Abstract : Molecular recognition directed self-assembly of supramolecular architectures or noncovalent synthesis, and molecular recognition directed self-assembly of transition states or self-synthesis, are two of the most active topics of research in the area of supramolecular chemistry. We are concerned with the use of the simplest endo-receptor i.e., crown ether in the design of two classes of systems. The first one is a system which is externally regulated by molecular recognition processes via a crown ether endo-receptor. This system is based on various classes of liquid-crystalline polymers which exhibit phase transitions that are manipulated by the reversible complexation of the crown ether present in different parts of their repeat unit with metal salts. The information gained from these experiments is then exploited in the design of the second group of systems. This consists of self-assembling building blocks containing various combinations of crown ether as endo-receptor and a tapered group as exo-receptor. Upon complexation with metal salts, these building blocks self-assemble into tubular supramolecular architectures. Therefore, while the first system exhibits molecular recognition directed phase transitions, the second one self-assembles into tubular supramolecular architectures via various molecular recognition processes. These tubular supramolecular architectures display a thermotropic hexagona columnar (phi h) liquid crystalline phase, which enables the structure of the self-assembled supramolecular architecture to be determined by X-ray diffraction experiments. jg