Controlling the Supramolecular Polymerization of Squaraine Dyes by a Molecular Chaperone Analogue.

Molecular chaperones are proteins that assist in the (un)folding and (dis)assembly of other macromolecular structures toward their biologically functional state in a non-covalent manner. Transferring this concept from nature to artificial self-assembly processes, here, we show a new strategy to control supramolecular polymerization via a chaperone-like two-component system. A new kinetic trapping method was developed that enables efficient retardation of the spontaneous self-assembly of a squaraine dye monomer.

"This Student Needs to Stay Back": To What Degree Would Instructors Rely on the Recommendation of Learning Analytics?

Learning analytics (LA) systems are becoming a new source of advice for instructors. Using LA provides new insights into learning behaviours and occurring problems about learners. Educational platforms collect a wide range of data while learners use them, for example, time spent on the platform, passed exams, and completed tasks and provide recommendations in terms of predicted learning success based on LA.

Control of self-assembly pathways toward conglomerate and racemic supramolecular polymers.

Homo- and heterochiral aggregation during crystallization of organic molecules has significance both for fundamental questions related to the origin of life as well as for the separation of homochiral compounds from their racemates in industrial processes. Herein, we analyse these phenomena at the lowest level of hierarchy - that is the self-assembly of a racemic mixture of (R,R)- and (S,S)-PBI into 1D supramolecular polymers. By a combination of UV/vis and NMR spectroscopy as well as atomic force microscopy, we demonstrate that homochiral aggregation of the racemic mixture leads to the formation of two types of supramolecular conglomerates under kinetic control, while under thermodynamic control heterochiral aggregation is preferred, affording a racemic supramolecular polymer.

Supramolecular Block Copolymers by Seeded Living Polymerization of Perylene Bisimides.

Living covalent polymerization has been a subject of intense research for many decades and has culminated in the synthesis of a large variety of block copolymers (BCPs) with structural and functional diversity. In contrast, the research on supramolecular BCPs is still in its infancy and their generation by living processes remains a challenge. Here we report the formation of supramolecular block copolymers by two-component seeded living polymerization of properly designed perylene bisimides (PBIs) under precise kinetic control.

Bis(merocyanine) Homo-Folda-Dimers: Evaluation of Electronic and Spectral Changes in Well-Defined Dye Aggregate Geometries.

A series of three bis(merocyanine) dyes comprising chromophores of different conjugation lengths has been synthesized and the intramolecular aggregation process was investigated by UV/Vis absorption spectroscopy. The spectral changes observed upon variation of the solvent polarity reveal a folding process resulting in a cofacial π-stack of two chromophores with a decrease of the aggregation tendency with increasing chromophore length and solvent polarity. Solvent-dependent UV/Vis studies of the monomeric reference dyes show a significant increase of the polyene-like character for dyes with longer polymethine chains in nonpolar solvents, which is reversed upon aggregation due to the polarizability effect of the adjacent chromophore within the dye stack.

Supramolecular Polymorphism in One-Dimensional Self-Assembly by Kinetic Pathway Control.

Controlling polymorphism in molecular solids is of great interest since the properties and performances of molecular materials depend on the molecules' mutual packing arrangements. Herein, we describe a perylene bisimide (PBI) organogelator molecule PBI-4 that self-assembles into three different one-dimensional supramolecular polymorphs (Agg 1-3) in the same solvent and at the same concentration at room temperature. The three supramolecular polymorphs were characterized by UV/vis, CD, fluorescence and IR spectroscopy, atomic force microscopy (AFM), and theoretical calculations, revealing that their packing arrangements are governed by distinct π-π-stacking modes and unique hydrogen-bonding patterns.

Living Supramolecular Polymerization of a Perylene Bisimide Dye into Fluorescent J-Aggregates.

The self-assembly of a new perylene bisimide (PBI) organogelator with 1,7-dimethoxy substituents in the bay position affords non-fluorescent H-aggregates at high cooling rates and fluorescent J-aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped "off-pathway" H-aggregates are transformed into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of π-π interactions and intra- and intermolecular hydrogen bonding for monomeric, H-, and J-aggregated PBIs.

Regioselective Catalytic and Stepwise Routes to Bulky, Functional-Group-Appended, and Luminescent 1,2-Azaborinines.

The regioselective syntheses of 1,2-azaborinines is achieved using an unsymmetrical iminoborane through both catalytic and stepwise modular routes. The 1,2-azaborinine ring can be selectively functionalized in the 4- and/or 6-position through control of the stepwise reaction sequence, allowing access to vinyl-functionalized and redox-active, luminescent, donor-functionalized 1,2-azaborinines. The electrochemistry and photochemistry of a tetraarylamine-substituted 1,2-azaborinine are studied.

Taming the beast: fluoromesityl groups induce a dramatic stability enhancement in boroles.

The electron-deficient pentaarylborole 1-(2',4',6'-tris(trifluoromethyl)phenyl)-2,3,4,5-tetraphenylborole () has been synthesised with the long-term aim of developing borole-based optoelectronic materials. The bulky 2,4,6-tris(trifluoromethyl)phenyl (FMes) group on the boron atom of significantly improves (>600 times) its air stability relative to its mesityl analogue. Moreover, shows good thermal stability without undergoing the dimerisation or isomerisation reactions reported for some other boroles.