Synthesis, crystal structure and photophysical properties of pyrene-helicene hybrids.

Synthesis of helically chiral aromatics resulting from fusion of pyrene and [4]- or [5]helicene has been accomplished using photoredox catalysis employing a Cu-based sensitizer as the key step. Photocyclisation experiments for the synthesis of the target compounds were carried out in batch and using continuous flow strategies. The solid-state structures, UV/Vis absorption spectra and fluorescence spectra of the pyrene-helicene hybrids were investigated and compared to that of the parent [5]helicene to discern the effects of merging a pyrene moiety within a helicene skeleton.

Double diels-alder strategies to soluble 2,9- and 2,9,6,13-tetraethynylpentacenes, photolytic [4 + 4] cycloadditions, and pentacene crystal packing.

Four new classes of organic solvent soluble ethynylpentacene derivatives (2,9-, 2,10-, 2,6,9,13-, 2,6,10,13-) have been prepared by complementary, versatile, double Diels-Alder strategies. Functional groups on the A, C, and E rings can be manipulated to increase the solubility, modulate the electronics, and alter the solid-state packing. Cycloaddition reactions with diene 2 and 1,4,5,8-anthradiquinone (3) or ortho-quinodimethane 19 with 1-butyl-3-methylimidazolim iodide (18) as the iodide source (a significant improvement over NaI) and benzoquinone (20) followed by in situ aromatization afforded the quinones 4, 5, 21, and 22, respectively.

Molecular folding of C60 acetylenic cyclophanes: pi-stacking of superimposed aromatic rings.

[structure: see text] The syntheses of two distinct families of phenylyne helical cyclophanes with potential for organic materials are described. The meta-bonded atropisomers afford interesting bowtie-like and butterfly-like conformers from a palladium(0), copper-mediated coupling sequence. Molecular modeling revealed the contrasting stereochemistry in these systems from differential molecular folding pathways during cyclization.