Exploiting coordination geometry to tune the dimensions and processability of metallosupramolecular polymers.

Achieving precise control over the morphology, dimensions and processability of functional materials is a key but challenging requirement for the fabrication of smart devices. To address this issue, we herein compare the self-assembly behavior of two new Pt(ii) complexes that differ in the molecular and coordination geometry through implementation of either a monodentate (pyridine) or bidentate (bipyridine) ligand. The molecular preorganization of the bipyridine-based complex enables effective self-assembly in solution involving Pt⋯Pt interactions, while preserving aggregate solubility.

Tuning energy landscapes and metal-metal interactions in supramolecular polymers regulated by coordination geometry.

Herein, we exploit coordination geometry as a new tool to regulate the non-covalent interactions, photophysical properties and energy landscape of supramolecular polymers. To this end, we have designed two self-assembled Pt(ii) complexes and that feature an identical aromatic surface, but differ in the coordination and molecular geometry (linear V-shaped) as a result of judicious ligand choice (monodentate pyridine bidentate bipyridine). Even though both complexes form cooperative supramolecular polymers in methylcyclohexane, their supramolecular and photophysical behaviour differ significantly: while the high preorganization of the bipyridine-based complex enables an H-type 1D stacking with short Pt⋯Pt contacts a two-step consecutive process, the existence of increased steric effects for the pyridyl-based derivative hinders the formation of metal-metal contacts and induces a single aggregation process into large bundles of fibers.

Solvent-controlled / isomerization [2 + 2] photocycloaddition mediated by supramolecular polymerization.

Control over the photochemical outcome of photochromic molecules in solution represents a major challenge, as photoexcitation often leads to multiple competing photochemical and/or supramolecular pathways resulting in complex product mixtures. Herein, we demonstrate precise and efficient control over the photochemical behaviour of cyanostilbenes in solution using a straightforward solvent-controlled approach based on supramolecular polymerization. To this end, we designed a π-extended cyanostilbene bolaamphiphile that exhibits tuneable solvent-dependent photochemical behaviour.

Understanding the role of conjugation length on the self-assembly behaviour of oligophenyleneethynylenes.

Oligophenyleneethynylenes (OPEs) are prominent building blocks with exciting optical and supramolecular properties. However, their generally small spectroscopic changes upon aggregation make the analysis of their self-assembly challenging, especially in the absence of additional hydrogen bonds. Herein, by investigating a series of OPEs of increasing size, we have unravelled the role of the conjugation length on the self-assembly properties of OPEs.

Dynamics of Meso-Chiral Interconversion in a Butterfly-Shape Overcrowded Alkene Rotor Tunable by Solvent Properties.

Elucidation of dynamics of molecular rotational motion is an essential part and challenging area of research. We demonstrate reversible diastereomeric interconversion of a molecular rotor composed of overcrowded butterfly-shape alkene (FDF). Its inherent dual rotatory motion (two rotors, one stator) with interconversion between two diastereomers, chiral trans-FDF and meso cis-FDF forms, has been examined in detail upon varying temperatures and solvents.

Tuning the mechanistic pathways of peptide self-assembly by aromatic interactions.

Herein, we have unravelled the key influence of aromatic interactions on the mechanistic pathways of peptide self-assembly by introducing suitable chromophores (pyrene vs. naphthalene). Although both self-assembled peptides are indistinguishable in their morphologies, this minor structural difference strongly affects the packing modes (parallel vs.

Introducing the Dihydro-1,3-azaboroles: Convenient Entry by a Three-Component Reaction, Synthetic and Photophysical Application.

The (Fmes)BH·SMe reagent () reacts sequentially with an acetylene and, e.g., xylylisonitrile in a convenient three-component reaction to give a series of unprecedented dihydro-1,3-azaborole derivatives .

Consequences of hidden kinetic pathways on supramolecular polymerization.

In recent years, the development of sophisticated analytical tools, kinetic models and sample preparation methods has significantly advanced the field of supramolecular polymerization, where the competition of kinetic thermodynamic processes has become commonplace for a wide range of building blocks. Typically, the kinetic pathways are identified in thermally controlled assembly experiments before they ultimately evolve to the thermodynamic minimum. However, there might be cases where the identification and thus the assessment of the influence of kinetic aggregates is not trivial, making the analysis of the self-assembly processes a hard task.

Synergistic repulsive interactions trigger pathway complexity.

Herein, we demonstrate the key impact of synergistic repulsive interactions on pathway complexity in aqueous media. To this end, we have examined the aqueous self-assembly of four new amphiphilic BODIPY dyes where the extent of repulsive interactions has been systematically varied.

Morphology control in metallosupramolecular assemblies through solvent-induced steric demand.

Controlling the supramolecular self-assembly of π-conjugated systems into defined morphologies is a prerequisite for the preparation of functional materials. In recent years, the development of sophisticated sample preparation protocols and modulation of various experimental conditions (solvent, concentration, temperature, etc.) have enabled precise control over aggregation pathways of different types of monomer units.

Inhibition of prostate cancer cell line (PC-3) by anhydrodihydroartemisinin (ADHA) through caspase-dependent pathway.

Cancer is a generic term for a large group of diseases characterized by the growth of abnormal cells, which is the second leading cause of death globally. To treat cancer, currently, a number of anticancer drugs belonging to various classes chemically are available. The discovery of artemisinin and its derivatives such as artesunate, arteether, and artemether became a milestone in the cure for malaria.

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media.

Pathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed.

pH-Responsive Side Chains as a Tool to Control Aqueous Self-Assembly Mechanisms.

pH-Tunable nanoscale morphology and self-assembly mechanism of a series of oligo(p-phenyleneethynylene) (OPE)-based bolaamphiphiles featuring poly(ethylene imine) (PEI) side chains of different length and degree of hydrolysis are described. Protonation and deprotonation of the PEI chains by changing the pH alters the hydrophilic/hydrophobic balance of the systems and, in turn, the strength of intermolecular interactions between the hydrophobic OPE moieties. Low pH values (3) lead to weak interaction between the OPEs and result in spherical nanoparticles, in which aggregation follows an isodesmic mechanism.

Exploiting Coordination Isomerism for Controlled Self-Assembly.

We exploited the inherent geometrical isomerism of a Pt complex as a new tool to control supramolecular assembly processes. UV irradiation and careful selection of solvent, temperature, and concentration leads to tunable coordination isomerism, which in turn allows fully reversible switching between two distinct aggregate species (1D fibers↔2D lamellae) with different photoresponsive behavior. Our findings not only broaden the scope of coordination isomerism, but also open up exciting possibilities for the development of novel stimuli-responsive nanomaterials.

Synthesis of novel S-linked dihydroartemisinin derivatives and evaluation of their anticancer activity.

We report herein the synthesis and anticancer activity of a set of novel S-linked artemisinins bearing an aliphatic/aromatic/heterocyclic nucleus as a substituent on the sulfur. The compounds were prepared from artemisinin via its lactol-form by an acid-catalyzed condensation of the desired thiol with the lactol. Both the C-10-α- and β-configured thiol ethers were synthesized with a view to making them available for the anticancer activity evaluation using a variety of cell lines.

Pathway Control in Cooperative vs. Anti-Cooperative Supramolecular Polymers.

Controlling the nanoscale morphology in assemblies of π-conjugated molecules is key to developing supramolecular functional materials. Here, we report an unsymmetrically substituted amphiphilic Pt complex 1 that shows unique self-assembly behavior in nonpolar media, providing two competing anti-cooperative and cooperative pathways with distinct molecular arrangement (long- vs. medium-slipped, respectively) and nanoscale morphology (discs vs.

Mechanistic Insights into the Self-Assembly of an Acid-Sensitive Photoresponsive Supramolecular Polymer.

The supramolecular polymerization of an acid-sensitive pyridyl-based ligand (L ) bearing a photoresponsive azobenzene moiety was elucidated by mechanistic studies. Addition of trifluoroacetic acid (TFA) led to the transformation of the antiparallel H-bonded fibers of L in methylcyclohexane into superhelical braid-like fibers stabilized by H-bonding of parallel-stacked monomer units. Interestingly, L dimers held together by unconventional pyridine-TFA N⋅⋅⋅H⋅⋅⋅O bridges represent the main structural elements of the assembly.

Unraveling Concomitant Packing Polymorphism in Metallosupramolecular Polymers.

The phenomenon of polymorphism is ubiquitous in biological systems and has also been observed in various types of self-assembled materials in solution and in the solid state. In the field of supramolecular polymers, different kinetic vs thermodynamic self-assembled species may exist in competition, a phenomenon termed as pathway complexity. In these examples, the transient kinetic species often has a very short lifetime and rapidly converts into the thermodynamic product.

Influence of metal coordination and light irradiation on hierarchical self-assembly processes.

Smart light-responsive supramolecular materials have been extensively investigated in the past decade, but so far the impact of metal coordination on hierarchical supramolecular structures of light-responsive building blocks has remained nearly unexplored. Herein, we unravel the hierarchical self-assembly of a small π-conjugated azo-containing pyridyl ligand that is able to respond to UV-light and metal complexation. The ligand self-assembles in an antiparallel fashion into long twisted fibers, which are then disassembled upon photoisomerization of the azobenzene groups, resulting in shorter rigid rods with a different packing motif.

Interplay between H-Bonding and Preorganization in the Evolution of Self-Assembled Systems.

Cooperative π-π interactions and H-bonding are frequently exploited in supramolecular polymerization; however, close scrutiny of their mutual interplay has been largely unexplored. Herein, we compare the self-assembly behavior of a series of C - and C -symmetrical oligophenyleneethynylenes differing in their amide topology (N- or C-centered). This subtle structural modification brings about drastic changes in their photophysical and supramolecular properties, highlighting the reciprocal impact of H-bonding vs.

Exploiting NH···Cl Hydrogen Bonding Interactions in Cooperative Metallosupramolecular Polymerization.

The self-assembly features of hydrophobic bispyridyldichlorido Pd(II) complexes, equipped with an extended aromatic surface derived from oligophenyleneethynylene (OPE) and polarizable amide functional groups, are reported. The cooperative supramolecular polymerization of these complexes results in bundles of thin fibers in which the monomer units are arranged in a translationally displaced or slipped fashion. Spectroscopic and microscopy studies reveal that these assemblies are held together by simultaneous π-stacking of the OPE moieties and NH···ClPd hydrogen bonds.

Reliability and diagnostic validity of a joint vibration analysis device.

Background: This observational study was designed to evaluate the reliability and diagnostic validity of Joint Vibration Analysis (JVA) in subjects with bilateral disc displacement with reduction and in subjects with bilateral normal disc position.

Methods: The reliability of selecting the traces was assessed by reading the same traces at an interval of 30 days. The reliability of the vibrations provided by the subjects was assessed by obtaining two tracings from each individual at an interval of 30 min.

Longitudinal Stability of Common TMJ Structural Disorders.

The longitudinal course of temporomandibular joint (TMJ) disc displacement (DD) and degenerative joint disease (DJD) has never been conclusively described with magnetic resonance imaging and computed tomography, respectively. This 8-y observational study's objective was to assess the longitudinal stability of DD and DJD among 401 subjects. The Validation Project provided baseline measures; follow-up was performed in the TMJ Impact Project.

Solvent-free bismuth oxycarbonate-mediated mechanochemical glycosylation: A simple greener alternative to access O-/S-glycosides efficiently.

Preparation of a variety of per-O-acylated O- and S-glycosides of a set of commonly encountered mono- and disaccharides has been achieved effectively by solvent-free grinding of the corresponding acetylated/benzoylated glycosyl bromide and the desired acceptor alcohol/thiol in the presence of bismuth carbonate in a planetary ball mill. The method is simple, requires short reaction time periods and is practical allowing it to be performed at a milligram-to multi-gram scale as required. In the cases where the product is crystalline, it was often obtained in practically pure form by crystallization (and without the need for chromatographic isolation).