Supramolecular Chemistry

In this paper, we present a summary of our work on highly photostable supramolecular ruthenium complexes, which may be incorporated into more complex systems for artificial solar energy conversion. We have used supramolecular chemistry and photochemistry to synthesize highly photostable ruthenium bipyridine cnronates and a bipyridazine podate complex and to enhance photoelectron-transfer reactions in physical model systems for artificial photosynthesis.

Hydrogenation of vegetable oils is a heterogeneous process where the process factors influence the conversion and selectivity. A Statistical study was performed on a sunflower oil (SFO) hydrogenation process using Pd-B/g-Al 2 O 3 catalyst to study the effect of the process factors, including temperature, hydrogen pressure, agitation, catalyst dose and reaction time on the iodine value and trans fatty acid content of hydrogenated SFO. It was found that each factor has a noticeable effect on the iodine value and trans fatty acid content of hydrogenated SFO. The study was also aimed to find out the optimum values for the hydrogenation factors which are capable to decline the IV to 70 (g iodine per 100 g oil) as well as produce a minimum trans fatty acid content of the hydrogenated SFO. The optimum values were found to be 431 K, 1000 kPa, 1000 kPa, 0.29 % and 42.2 min for the temperature, hydrogen pressure, agitation, catalyst dose and reaction time respectively.

Figure 10. UV-vis spectra (A) and TEM images and size distributions (B) of (a) [AuCl 4 ]before reduction; dodecanethiol-AuNPs (b) as prepared and after heat treatment at (c) 150, (d) 190, and (e) 230°C; and (f) octadecanethiol-AuNPs heat-treated at 250°C. Reprinted with permission from ref 188b (Miyake's group).

Stability constants of complexes of Ag(I) and Cu(II) perchlorates and nitrates with some macrocyclic compounds in 90 and 75% (v/v) DMSO 1 water and 75% (v/v) DMF 1 water media have been determined by potentiometry. Silver and copper wires, and Coated Wire Ion Selective Electrodes (CWISE) were used as indicator electrodes. It was observed that complexation is stronger when the salt is present as a perchlorate than when it is as a nitrate. For both cations the stability constant values in 75% (v/v) DMF 1 water were somewhat higher than in 75% (v/v) DMSO. The macrocyclic effect due to cyclization of linear amine tosylates has been observed. Competitive potentiometry has been utilized to compare some of the results.

In supramolecular chemistry [1] synthetically designed organic constituents interact noncovalently, in a directed and specific way to form host-guest complexes of higher complexity. The ability to tailor the molecular interplay with respect of chemical design, specificity, and molecular switching opens up the development of new molecular materials for artificial molecular recognition, molecular organization, and selfassembly. We have used mechanical single-molecule force spectroscopy to investigate the binding of individual resorc-[4]arene-ligand host-guest complexes. By using diluted samples of the host and guest molecules that are modified with a long linker which is attached to an atomic force microscope (AFM) tip, we were able to prevent multiple binding and to observe single host-guest unbinding events in a supramolecular system for the first time. The molecular binding forces, their dependence on external loading rates, the rate of dissociation, and the molecular cavity length directly relate to the molecular properties of the supramolecular species and are consistent with an activated decay of a metastable bound state, a finding already established for biological receptor-ligand complexes. This result allows new insights into the mechanisms, kinetics, and thermodynamics of intermolecular association in chemistry and biology, and opens new possibilities in the investigation, design, and development of synthetic receptor systems.

The Research about Synthesis and Characterization of SiO2 have been worked. We have synthesized Silica from "petung"bamboo leaf ash as SiO2 source. This step used sol gel methode. SiO2 were characterized by Fourier Transform Infra Red (FTIR) to investigated the stucture andX-Ray Diffaction to know about structure and crystallinity. FTIR spectra show peak at 617,22 cm-1 area that spesific for Si-H bond, peak at 786,96 cm-1 and 1095,57 cm-1 area specific for Si-O-Si bonds. Difractogram of SiO2 show that there are peak at 2θ 21,99; 31,67 and 38,88 were specific for SiO2 that calcinated at 800 o C, while for SiO2 that calcinated at 400 o C there were no peak at 2θ 31,67 dan 38,88. That peaks not shown may be because low crystallinity of SiO2 that calcinated at 400 o C. Calcination temperature greatly affects the crystallinity of SiO2.

Wet spinning and radial self-assembly of a carbohydrate low molecular weight gelator into well organized hydrogel fi laments A single biocompatible small molecule, the N-heptyl-D-galactonamide can be spun into well-defi ned hydrogel fi laments. A solution of this molecule in dimethylsulfoxide is injected in water, resulting in the formation of a continuous fi lament. The counter-diff usion of water and dimethylsulfoxide triggers the self-assembly of the molecule into supramolecular nanofi bers. A radial organization of the fi bers was observed in the gel fi laments. This method could be used for making well-defi ned cell culture scaff olds. As featured in: rsc.li/nanoscale

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur under conventional heating and modifications in selectivity (chemo-, regio-and stereoselectivity) have even been reported. Recent advances in microwave-assisted combinatorial chemistry include high-speed solid-phase and polymer-supported organic synthesis, rapid parallel synthesis of compound libraries, and library generation by automated sequential microwave irradiation. In addition, new instrumentation for high-throughput microwave-assisted synthesis continues to be developed at a steady pace. The impressive speed combined with the unmatched control over reaction parameters justifies the growing interest in this application of microwave heating. In this review we highlight our recent advances in this area, with a particular emphasis on cycloaddition reactions of heterocyclic compounds both with and without supports, applications in supramolecular chemistry and the reproducibility and scalability of organic reactions involving the use of microwave irradiation techniques.

Offset-linked dimers of C-ethylpyrogallol[4]arene (PgC 2 ) , 18-crown-6 have been synthesised and structurally elucidated. The 18-crown-6 acts as a template/guest for the assembly of the first observed tri-solvent-bridged, extended pyrogallol[4] arene-based dimers. Oppositely, adjacently and diagonally positioned macrocycles are connected through a complex network of solvent-mediated H bonds.

The binding affinity for Pb 2+ , Cd 2+ and Hg 2+ of the sinapic acid-calix[4]arene hybrid 2, having four sinapyl pendants at the upper rim, has been investigated via an UV-Vis study. Compound 2 has better complexing ability than the monomeric p-phenetidine derivative 1. This highlights that the clustering of sinapyl units in a basket-like structure, dictated by the calixarene scaffold, greatly enhances the complexing properties. Ligand 2 forms complexes even with Hg 2+ , which is not complexed by 1 at all; the complexes formed by 2 with Pb 2+ and Cd 2+ are much stronger than the analogous complexes formed by 1. The UV-Vis investigation shows that the hybrid 2 markedly favors Pb 2+ over Cd 2+ and Hg 2+. Information on the structural properties of the complex species was obtained by 1 H NMR spectroscopy. NMR data show that all three metal ions are placed into the cavity consisting of the calixarene scaffold and the sinapyl pendants, though their binding affects the coordinating regions to a different extent.

Cyclodextrins (CDs) are a family of cyclic oligosaccharides composed of a-(1,4)-linked glucopyranose subunits. The most important feature of CDs is their ability to form inclusion complexes (host-guest complexes) with a very wide range of solid, liquid and gaseous compounds by a molecular complexation. During the last decade, a considerable number of research papers has been focused on the use of CDs to enhance fluorescence intensity of different analytes and to develop CD-induced spectrofluorimetric method. In this review, the various spectrofluorimetric methods based on host-inclusion complex are presented.

A direct tetraalkylation of thiacalix[4]arenes using procedures well established in ÔclassicalÕ calixarene chemistry usually gives the 1,3-alternate conformers as the main product (n-PrI/K 2 CO 3 /acetone) while the cone conformers are obtained only in very poor yields (n-PrI/NaH/DMF). Surprisingly, the so far almost inaccessible cone conformers can be prepared in high yields using the two-step procedure: dialkylation-dialkylation, opening the way for their further utilisation in supramolecular chemistry.

Abstract Solution and solid state studies of the complexation of Hg 2+ and Pb 2+ by the homologous bis-tridentate ligands 1 and 2H 2 obtained by condensation of bis (methylhydrazino) phenylpyrimidine and bis (hydrazino) phenylpyrimidine, respectively, ...

ABSTRACT In spite of its impressive record in medicinal chemistry, the role of barbituric acid H3BA (pyrimidine-2,4,6(1H,3H,5H)-trione) in coordination, organometallic and supramolecular chemistries has not yet been analyzed and reviewed. However, H3BA can be readily functionalized and provides rich opportunities to create coordination bonds and non-covalent interactions. Thus, derivatives of H3BA (barbituric acids, BAs) are widely used for the preparation of a wide range of complexes with various metals of almost all groups of the periodic table. The review systematizes information on the synthesis, tautomerism, acid-base properties of BAs and their use for the construction of organometallic and coordination compounds, as well as coordination polymers and supramolecular assemblies. The role of different metal ions and the structure of BAs in directing the preparative pathways and tuning particular structural properties of the resulting compounds are discussed. Some valuable applications of BAs, in particular in the construction of molecular receptors, magnetic and nonlinear optic materials, bioactive compounds, drug cocrystal design, catalysis and photochemistry are also envisaged.

A new 3-alkylpiperidine compound (À)-acanthocyclamine A (1) has been obtained from the methanolic extract of Acanthostrongylophora ingens (order Haplosclerida, family Petrosiidae) collected from Wakatobi Marine National Park in South East Sulawesi, Indonesia. The structure of 1 was investigated by extensive 1D-and 2D-NMR experiments. The absolute configuration of 1 was established by X-ray crystallography from anomalous dispersion effects using Cu radiation as C2 (R), C3 (R), C7 (R), and C9 (R). A plausible biosynthetic scheme leading to 1 is presented, and compared with the biosynthetic pathway proposed for the manzamine alkaloids.

Intermolecular hydrogen bonds between 2,6-bis(acylamino)pyridines and dipyridin-2-ylamine as well as 4,4- dimethylpiperidine-2,6-dione are responsible for relatively strong interactions between these species. Association has been found to be significantly affected by the size of acyl substituent (chemical shift of the NH proton was used as the main probe in determination of the association constants). Calculations at the DFT level of theory are in line with the experimentally observed results. Calculated energies of the interactions between the complex congeners also show the size of the substituent to affect the association. Conformational changes in the dipyridin-2-ylamine molecule are shown to adapt a geometry suitable for formation of efficient hydrogen bonding.

A new technology to form nanoparticles of hydrophobic organic actives at high concentration and yield, as well as methods to characterize the process, are presented. In Flash NanoPrecipitation, an organic active and an amphiphilic diblock copolymer are molecularly dissolved in an organic phase and mixed rapidly with a miscible anti-solvent to afford precipitation of the active with a tunable, narrow submicron particle size distribution from 1 µm to 80 nm. The enabling components are a novel 'analytical' (quantified mixing time) confined impinging jets (CIJ) mixer for millisecond stream homogenization and amphiphilic diblock copolymers which alter the organic nucleation and growth, provide steric stabilization for the particles, and offer a functional surface for the particle. Applications in enhanced pharmaceutical delivery, dye preparation, and pesticide formulation are specifically targeted.

A fragile and non-thixotropic biocompatible low molecular weight gel is printed in 3D structures by a solvent exchange process. The 3D printing process is based on the continuous extrusion of a solution of a small amphiphile molecule, N-heptyl-D-galactonamide, in dimethylsulfoxide, that forms a gel in contact with water. The diffusion of water in the dimethylsulfoxide / N-heptyl-D-galactonamide solution triggers the self-assembly of the molecule into supramolecular fibers and the setting of the ink. The conditions for getting a well-defined pattern and the dimensions of the constructs have been determined. The resulting constructs can be easily dissolved, orienting its application as a sacrificial ink or a temporary support. This method opens the way to the injection and the 3D printing of other fragile and non-thixotropic supramolecular hydrogels.

In an effort to explore [trans-Co(en) 2 Cl 2 ] C as anion receptor for tetrabromocadmate and tetraiodocadmate ion, green coloured single crystals of [trans-Co(en) 2 Cl 2 ]CdBr 4 I and [trans-Co(en) 2 Cl 2 ]CdI 4 II have been obtained by slowly mixing the separately dissolved transdichlorobis(ethylenediamine)cobalt(III) chloride with potassium tetrabromocadmate and tetraiodocadmate in aqueous medium in 2:1 molar ratio. The newly synthesized complex salt was characterized on the basis of elemental analysis and spectroscopic techniques (IR, UV/visible, 1 H and 13 C NMR). Single crystal X-ray structure determination of [trans-Co(en) 2 Cl 2 ] 2 CdBr 4 revealed that it crystallizes in the orthorhombic space group Pbca with aZ18.6201(10), bZ12.0872(6), cZ24.0877(12) Å , VZ5421.3(5) Å 3 , ZZ8, RZ0.0727. Supramolecular hydrogen bonding networks between ionic groups: bromide ions of tetrabromocadmate group and NH groups of coordinated ethylenediamine molecules, i.e. N-H/Br K interactions by second sphere coordination besides electrostatic forces of attraction have been observed. This suggests that [trans-Co(en) 2 Cl 2 ] C is a promising anion receptor for the tetrabromocadmate. q

Figure 10. UV-vis spectra (A) and TEM images and size distributions (B) of (a) [AuCl 4 ]before reduction; dodecanethiol-AuNPs (b) as prepared and after heat treatment at (c) 150, (d) 190, and (e) 230°C; and (f) octadecanethiol-AuNPs heat-treated at 250°C. Reprinted with permission from ref 188b (Miyake's group).

ABSTRACT The rheological and adhesive properties of bis-urea functionalized low-molecular-weight polyisobutylenes (PIBUT) are investigated. The polymers, which can interact through supramolecular hydrogen bonds, can self-organize over times of the order of days at room temperature. This organized structure has been identified by small angle X-ray scattering (SAXS) and its rheological properties indicate the behaviour of a soft viscoelastic gel. The ordered structure can be disrupted by temperature and shear so that at 80 °C, the material behaves as a highly viscoelastic fluid and no SAXS peak is observed. When cooled back at room temperature, the PIBUT retrieves its ordered structure and gel properties after 20 h of annealing. This very slow molecular dynamics gives PIBUT a highly dissipative nature upon deformation, which combined with strongly interacting moieties results in very interesting adhesive properties both on steel surfaces but more importantly on typical low adhesion surfaces such as silicone. A strategy based on the controlled incorporation of supramolecular bonds in a covalently crosslinked network appears promising for the development of a new generation of highly interacting and dissipative soft adhesives.

This review will cover the developments in the chemistry of phenanthroline-based ligands in the last 10-15 years. 1,10-Phenanthroline (phen) is a classic ligand in coordination chemistry, which couples versatility in metal ion binding with peculiar properties of its complexes. For instance, metal complexes with phenanthroline can be featured by an intense luminescence or can interact with DNA in an intercalative fashion inducing, in some cases, DNA cleavage. For this reason a number of phenanthroline-containing ligands has been recently synthesized by inserting phenanthroline within open-chain or macrocyclic backbone, in order to develop new molecular chemosensors for metal cations and anions, ionophores as well as new intercalating agents for polynucleotides. Furthermore, phenanthroline is rigid and its insertion within cyclic or acyclic structures can impart to the resulting ligand a high degree of pre-organization, affording selective complexing agents. This review will discuss on the coordination, luminescence and intercalating and/or DNA cleaving properties as well as on analytical applications of metal complexes with phenanthroline-based ligands. Particular attention will be devoted to macrocyclic receptors or openchain ligands that, beside the phenanthroline nitrogen atoms, contain other donor atoms able to interact with the metal cations or anions.

Introduction Pharmaceutical co-crystals have established a new paradigm in the solid-state modification. The formation of API co-crystal offers a wide range of physical and chemical enhancements to the properties of drugs without altering their chemical nature, thereby maintaining its pharmaceutical importance as such. 1 This is evident from the fact that regulatory bodies like United States Food and Drug Administration (USFDA) and European Medicines Agency (EMA) have published regulatory guidelines to clarify the status of co-crystals in their respective regions. Pharmaceutical and Biotechnology companies rely upon intellectual protection for safeguarding their products. In order to maintain revenues generated through these products as a means to recover the resources and money spent on research and development, the presence of proper regulatory guidelines is expected to significantly affect the development and quality control as well as intellectual properties aspects of pharmaceutical cocrystals and their formulations. 2 However, the concern that remains unanswered is whether the standard development and manufacturing processes that were initially designed for salt-based formulations can also be used for co-crystal based formulations in order to achieve the desired product quality that is required to ensure the safety and efficacy. 3 Moreover, from regulatory perspective the addition of another component to the drug formulation could mandate additional bioequivalence, clinical and toxicity studies.

The control of chirality in synthetic self-assembled systems remains challenging because of their lower stability and their higher susceptibility to racemization when compared to covalent systems. In this review the supramolecular chirality of noncovalent hydrogen-bonded assemblies formed by multiple cooperative hydrogenbonds between calix[4]arene dimelamines and cyanurates or barbiturates derivatives (rosette assemblies) are described. It is shown that the amplification of chirality (a high enantiomeric or diastereomeric excess induced by a small initial amount of chiral bias) of double and tetrarosette assemblies is influenced by bulky substitution on their components and electronic properties of the substituents as well as their proximity to the rosette core. In the absence of chiral centers in their components, the assemblies form as a racemic mixture of both enantiomers (P and M). The synthesis of enantiomerically pure rosette assemblies is conducted via induction of chirality ...

Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

The interrelationships between cooperativity and the chelate, macrocyclic, and cryptate effects are described in this chapter. The chapter begins by defining and providing a brief historical background of these four closely related effects as they pertain to both transition metal coordination chemistry and supramolecular chemistry. The second section provides an overview of bonding for supramolecular chemistry with a comparison illustrating similarities with and differences from transition metal coordination. Sections 3 and 4 describe the chemistry of the chelate, macrocyclic, and cryptate effects and the important role that cooperativity plays in each for transition metals coordination and supramolecular chemistry, respectively. Thermodynamic aspects and structural foundations for the increasing stability of complexes as they evolve from chelates through cryptates are also described. Section 4 on supramolecular chemistry is further divided into sections on the chemistry of cations, followed by anions. A short conclusion is provided at the end of the chapter. Throughout the chapter, examples are provided that illustrate the manner in which these important chemical effects are manifested. Keywords: cooperativity; chelate effect; macrocyclic effect; cryptate effect; supramolecular; thermodynamics; anion coordination; crown ethers

The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly(tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved longterm biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.

The kinetics and mechanism of the oxidation of the biologically important molecule, cysteamine, by acidic bromate and molecular bromine have been studied. In excess acidic bromate conditions, cysteamine is oxidized to Nbrominated derivatives, and in excess cysteamine the oxidation product is taurine according to the following stoichiometry: BrO 3 -+ H 2 NCH 2 CH 2 SH ÷ H 2 NCH 2 CH 2 SO 3 H + Br -. There is quantitative formation of taurine before N-bromination commences. Excess aqueous bromine oxidizes cysteamine to give dibromotaurine: 5Br 2 + H 2 NCH 2 CH 2 SH + 3H 2 O ÷ Br 2 NCH 2 CH 2 SO 3 H + 8Br -+ 8H + , while excess cysteamine conditions gave monobromotaurine. The oxidation of cysteamine by aqueous bromine is effectively diffusion-controlled all the way to the formation of monobromotaurine. Further formation of dibromotaurine is dependent on acid concentrations, with highly acidic conditions inhibiting further reaction towards formation of dibromotaurine. The formation of the N-brominated derivatives of taurine is reversible, with taurine regenerated in the presence of a reducing agent such as iodide. This feature makes it possible for taurine to moderate hypobromous acid toxicity in the physiological environment.

Figure 10. UV-vis spectra (A) and TEM images and size distributions (B) of (a) [AuCl 4 ]before reduction; dodecanethiol-AuNPs (b) as prepared and after heat treatment at (c) 150, (d) 190, and (e) 230°C; and (f) octadecanethiol-AuNPs heat-treated at 250°C. Reprinted with permission from ref 188b (Miyake's group).

The core objective of nanoparticles is to control and manipulate biomacromolecular constructs and supramolecular assemblies that are critical to living cells in order to improve the quality of human health. By definition, these constructs and assemblies are nanoscale and include entities such as drugs, proteins, DNA/RNA, viruses, cellular lipid bilayers, cellular receptor sites and antibody variable regions critical for immunology and are involved in events of nanoscale proportions. The emergence of such nanotherapeutics/diagnostics will allow a deeper understanding of human longevity and human ills that include cancer, cardiovascular disease and genetic disorders. A technology platform that provides a wide range of synthetic nanostructures that may be controlled as a function of size, shape and surface chemistry and scale to these nanotechnical dimensions will be a critical first step in developing appropriate tools and a scientific basis for understanding nanoparticles.

In 1758 Roger Boscovich (1711-1787) published "A Theory of natural philosophy reduced to one unique law of forces that exist in nature". The Theory has had a major impact on Boscovich's contemporaries and resulted in many followers in the 19th and at the beginning of the 20th century. His life, scientific activity, and philosophical views, as well as his influence on contemporaries and followers, are dealt with in this monograph. The theory is actually the very first quantum theory. He was the first one to draw the orbitals by which some particle moves around particles located in a center and explain that by a transition from one orbital to another a particle either gains or loses a certain amount (quantum) of energy. His primary contribution was to the discovery of the structure of atoms of chemical elements. He anticipated the possibility of the existence of macromolecules (i.e. polymers), nano-tubes neutrino, quarks, gluons, and also the structure of diamond and graphite.

A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex ) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate.

When working in the field of host–guest chemistry, the binding constants have to be determined on many occasions. Here is
a detailed document of how to determine the binding constants which covers both the basic principle and the practical issue:
a practical experimental guideline, a representativemethod for the determination of stoichiometry and for the evaluation of a
complex concentration, precautions to be taken on setting up concentration conditions of the titration experiment, practical
data-treatment methods and estimation of statistical errors. This document is described in detail using the basic level of
mathematics, statistics, and programs of spreadsheet software. Especially, the titration experiments by means of UV-visible
and NMR spectroscopy are carried out and described.