Rapid syntheses of oligo( p -phenyleneethynylene)s via iterative convergent approach

Carbonyl-to-Alkyne Electron Donation Effects in up to 10-nm-Long, Unimolecular Oligo(p-phenylene ethynylenes)

We synthesized some of the longest unimolecular oligo(p-phenylene ethynylenes) (OPEs), which are fully substituted with electron-withdrawing ester groups. An iterative convergent/divergent (a.k.a. iterative exponential growth - IEG) strategy based on Sonogashira couplings was utilized to access these sequence-defined macromolecules with up to 16 repeating units and 32 ester substituents. The carbonyl groups of the ester substituents interact with the triple bonds of the OPEs, leading to (i) unusual, angled triple bonds with increased rotational barrier, (ii) enhanced conformational disorder, and (iii) associated broadening of the UV/Vis absorption spectrum. Our results demonstrate that fully air-stable, unimolecular OPEs with ester groups can readily be accessed with IEG chemistry, providing new macromolecular backbones with unique geometrical, conformational, and photophysical properties.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Polymerization of a divalent/tetravalent metal-storing atom-mimicking dendrimer

The phenylazomethine dendrimer (DPA) has a layer-by-layer electron density gradient that is an analog of the Bohr atom (atom mimicry). In combination with electron pair mimicry, the polymerization of this atom-mimicking dendrimer was achieved. The valency of the mimicked atom was controlled by changing the chemical structure of the dendrimer. By mimicking a divalent atom, a one-dimensional (1D) polymer was obtained, and by using a planar tetravalent atom mimic, a 2D polymer was obtained. These poly(dendrimer) polymers could store Lewis acids (SnCl₂) in their unoccupied orbitals, thus indicating that these poly(dendrimer) polymers consist of a series of nanocontainers.

Synthesis and 2D self-assembly at the liquid–solid interface of novel H-bonding linear π-conjugated oligomers terminated by uracil and melamine units

2D self-assembly of a novel π-conjugated oligomer terminated by two uracil units is solvent dependent and involves multiple intermolecular H-bonds.

Oligospiroketals as novel molecular rods

A modular approach for the synthesis of molecular rods based on oligospiroketals has been developed. The strategy relies on different terminal and intermediate segments, which are joined by ketal formation between ketones and diols. For this purpose it was necessary to develop a new ketalization method to circumvent some problems related with the established methods. The terminal segments are either derived from 4-piperidinone or from 4-oxocyclohexane carboxylic acid whereas the intermediate segments rest on pentaerythritol and cyclohexane-1,4-dione. A series of trispiro (14-18), hexaspiro (19) and nonaspiro (20) compounds have been prepared and characterized. From these we realized that it is imperative to use solubility enhancing groups if more than seven rings are joined.