Designing Stimuli-Responsive Supramolecular Gels by Tuning the Non-Covalent Interactions of the Functional Groups.

The physical characteristics of a supramolecular gel are greatly influenced by the nature and arrangement of functional groups in the gelator. This work focuses on the impact of the functional groups, specifically the hydroxyl group, on the stimuli-responsive properties of a gel. We used a -symmetric benzene-1,3,5-tricarboxamide (BTA) platform, which was attached to the methyl ester of phenylalanine (MPBTA) and tyrosine (MTBTA).

Single Crystal to Single Crystal Transformation of Porous Materials Based on Zinc Nodes and Mercaptobenzoic Acid.

Porous coordination polymers (PCPs) are an excellent class of porous crystalline materials with tunable properties and intriguing potential applications spanning multiple disciplines. In this work, we report the synthesis and characterization of a PCP (HI-103) based on 4,4'-dithiodibenzoic acid ligand and zinc nitrate with two DMF molecules residing in the porous network. The stability of the porous network was analyzed by heating the compound at 60.

Supramolecular Gels Based on -Symmetric Amides: Application in Anion-Sensing and Removal of Dyes from Water.

We modified -symmetric benzene-1,3,5--amide (BTA) by introducing flexible linkers in order to generate an N-centered BTA (N-BTA) molecule. The N-BTA compound formed gels in alcohols and aqueous mixtures of high-polar solvents. Rheological studies showed that the DMSO/water (1:1, /) gels were mechanically stronger compared to other gels, and a similar trend was observed for thermal stability.

Nanoscale assembly of enantiomeric supramolecular gels driven by the nature of solvents.

Understanding the key parameters that control the self-assembly process is critical to predict self-assembly modes in multi-component systems, which will lead to the development of nanofibrous materials with tuneable properties. Enantiomeric amino acid-based low-molecular-weight gelators (LMWGs) were mixed in polar (polar protic) and aromatic apolar (aromatic) solvents and compared to their individual counterparts to probe the effect of solvent polarity on the self-assembly process. Scanning electron microscopy (SEM) reveals that xerogels of individual components display hollow needles in polar protic solvents, while chiral coils are observed in aromatic solvents.

AsymPol-TEKs as efficient polarizing agents for MAS-DNP in glass matrices of non-aqueous solvents.

Two polarizing agents from the AsymPol family, AsymPol-TEK and cAsymPol-TEK (methyl-free version) are introduced for MAS-DNP applications in non-aqueous solvents. The performance of these new biradicals is rationalized in detail using a combination of electron paramagnetic resonance spectroscopy, density functional theory, molecular dynamics and quantitative MAS-DNP spin dynamics simulations. By slightly modifying the experimental protocol to keep the sample temperature low at insertion, we are able to obtain reproducable DNP-NMR data with 1,1,2,2-tetrachloroethane (TCE) at 100 K, which facilitates optimization and comparison of different polarizing agents.

The Role of Functional Groups in Tuning the Self-Assembly Modes and Physical Properties of Multicomponent Gels.

We have analyzed the nature and role of functional groups on the self-assembly modes and the physical properties of multicomponent gels with structurally similar individual components. The gelation properties of individual and mixed enantiomeric compounds of biphenyl bis-(amides) of alanine (BPA) or phenylalanine (BPP) methyl ester were analyzed in various solvent/solvent mixtures. Multicomponent gels were formed by mixing the enantiomeric BPP compounds at a lower concentration, but a higher concentration was required for mixed alanine-based BPA gels.

Stimuli-Responsive Properties of Supramolecular Gels Based on Pyridyl--oxide Amides.

The nature of functional groups and their relative position and orientation play an important role in tuning the gelation properties of stimuli-responsive supramolecular gels. In this work, we synthesized and characterized mono-/bis-pyridyl--oxide compounds of -(4-pyridyl)nicotinamide (-). The gelation properties of these -oxide compounds were compared with the reported isomeric counterpart mono-/bis-pyridyl--oxide compounds of -(4-pyridyl)isonicotinamide.

Analysing the role of anions in the synthesis of catalytically active urea-based MOFs.

The synthesis of catalytically active metal-organic frameworks (MOFs) with copper(II) paddle-wheel clusters and urea-carboxylate linkers was achieved at room temperature in the presence of sulphate anions. The role of various anions in determining the MOF structure was analysed using X-ray diffraction. Structural analysis of the MOFs indicated that a two-fold interpenetrated rhombus grid (HI-101) was formed in the presence of sulphate anions, but a three-fold interpenetrated square grid network (HI-102) was obtained with nitrate and perchlorate anions.

Cytotoxic effects of halogenated tin phosphinoyldithioformate complexes against several cancer cell lines.

Organotin complexes are studied as promising alternatives to the anticancer drug cisplatin. We report two monoorganotin(IV) complexes based on a dibenzyl phosphinoyldithioformate (H-DBPTF) ligand, containing either bromide (Sn-DBPTF-1) or chloride (Sn-DBPTF-2) anions. The complexes were characterized by standard analytical techniques and the structural details of these complexes were elucidated by single crystal X-ray diffraction.

Towards a selective synthetic route for cobalt amino acid complexes and their application in ring opening polymerization of -lactide.

Catalysts based on cobalt amino acids and 2,2 bipyridine (bipy) present an attractive and cost-effective alternative as ring opening polymerization catalysts, yet this system remains underexplored despite the advantageous coordination properties of amino acids and bipy as ligands combined with the variety of accessible oxidation states and coordination geometries of cobalt. Here, metal complexes of type [Co(aa)(bipy)] with amino acids (aa: glycine, leucine and threonine) as ligands are reported. The complexes were characterized spectroscopically (IR, UV-vis and H, C NMR for diamagnetic species), and by MS spectrometry and elemental analysis.

Highly Efficient Polarizing Agents for MAS-DNP of Proton-Dense Molecular Solids.

Efficiently hyperpolarizing proton-dense molecular solids through dynamic nuclear polarization (DNP) solid-state NMR is still an unmet challenge. Polarizing agents (PAs) developed so far do not perform well on proton-rich systems, such as organic microcrystals and biomolecular assemblies. Herein we introduce a new PA, cAsymPol-POK, and report outstanding hyperpolarization efficiency on 12.

Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl--oxide Urea) Gelators.

The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl--oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl--oxides induced hydrogelation.

Enantioselective Gel Phase Synthesis of Metal-Organic Materials.

We report the asymmetric synthesis of homochiral metal-organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates.

Role of -Oxide Moieties in Tuning Supramolecular Gel-State Properties.

The role of specific interactions in the self-assembly process of low molecular weight gelators (LMWGs) was studied by altering the nonbonding interactions responsible for gel formation via structural modification of the gelator/nongelator. This was achieved by modifying pyridyl moieties of bis(pyridyl) urea-based hydrogelator () and the isomer () to pyridyl -oxide compounds ( and , respectively). The modification of the functional groups resulted in the tuning of the gelation properties of the parent gelator, which induced/enhanced the gelation properties.

Reaction Chemistry of the -[MoO(μ-S)(S)(DMF)] Complex with Cyanide and Catalytic Thiocyanate Formation.

Removal of cyanide as nontoxic thiocyanate under physiological conditions may serve as a catalytic detoxification route . Aqueous catalytic reaction conditions were explored where at the conditions employed the reaction proceeded to exhaustion in 1 h. The complex, -[MoO(μ-S)(S)(DMF)] , participates in a ligand exchange reaction of the dimethylformamide ligands and cyanide.

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification.

The factors affecting the self-assembly process in low molecular weight gelators (LMWGs) were investigated by tuning the gelation properties of a well-known gelator -(4-pyridyl)isonicotinamide (). The N-H∙∙∙N interactions responsible for gel formation in were disrupted by altering the functional groups of , which was achieved by modifying pyridyl moieties of the gelator to pyridyl -oxides. We synthesized two mono--oxides ( and ) and a di--oxide () and the gelation studies revealed selective gelation of in water, but the two mono--oxides formed crystals.

Enhanced Mechanical and Thermal Strength in Mixed-Enantiomers-Based Supramolecular Gel.

Mixing supramolecular gels based on enantiomers leads to re-arrangement of gel fibers at the molecular level, which results in more favorable packing and tunable properties. Bis(urea) compounds tagged with a phenylalanine methyl ester in racemic and enantiopure forms were synthesized. Both enantiopure and racemate compounds formed gels in a wide range of solvents and the racemate (1-rac) formed a stronger gel network compared with the enantiomers.

Stuffing the nail: A simple technique for the extraction of a broken femoral nail.

The extraction of broken femoral nails can be a challenging procedure and surgeons should be familiar with many different techniques. This paper demonstrates a case study and new, simple and cost effective technique for the removal of broken cannulated femoral nails. Our technique uses two guide wires of variable diameter and had several key points of differentiation from previous methods.

Electron beam induced deposition of silacyclohexane and dichlorosilacyclohexane: the role of dissociative ionization and dissociative electron attachment in the deposition process.

We present first experiments on electron beam induced deposition of silacyclohexane (SCH) and dichlorosilacyclohexane (DCSCH) under a focused high-energy electron beam (FEBID). We compare the deposition dynamics observed when growing pillars of high aspect ratio from these compounds and we compare the proximity effect observed for these compounds. The two precursors show similar behaviour with regards to fragmentation through dissociative ionization in the gas phase under single-collision conditions.

Pharmaceutical polymorph control in a drug-mimetic supramolecular gel.

We report the synthesis of a bis(urea) gelator designed to specifically mimic the chemical structure of the highly polymorphic drug substance ROY. Crystallization of ROY from toluene gels of this gelator results in the formation of the metastable red form instead of the thermodynamic yellow polymorph. In contrast, all other gels and solution control experiments give the yellow form.

Fluorous 'ponytails' lead to strong gelators showing thermally induced structure evolution.

Appending perfluoroalkyl substituents to bis(urea) gelators results in significantly decreased inter-chain interactions with markedly thinner fibres and hence more cross-linked and more transparent gels with potential applications in the crystallisation of fluorinated pharmaceuticals. Gel structure has been probed by detailed SANS measurements which indicate a surprising structure evolution on thermal cycling, not seen for hydrocarbon analogues. The SANS data are complemented by the single crystal X-ray structure of one fluorinated gelator.