Configurationally Stable Longitudinally Twisted Polycyclic Aromatic Compounds

Abstract

Two strategies for the synthesis of configurationally stable twisted polycyclic aromatic compounds (PACs) were pursued. The first approach employed dissymmetrically positioned 1-naphthyl substituents to bias the direction of twist in highly substituted PACs. 2,3-Bis(1-naphthyl)-1,4-diphenyltriphenylene (7) was prepared, and its meso cis-dinaphthyl and enantiomeric trans-dinaphthyl isomers were resolved by preparative supercritical fluid chromatography (SFC) on chiral supports. Similarly, several naphthyl-substituted derivatives of the more highly twisted 9,10,11,12,13,14-hexaphenylbenzo[b]triphenylene (2) were prepared. Of these, 10-(1-naphthyl)-9,11,12,14-tetraphenylbenzo[b]triphenylene (13) was resolved by SFC on a chiral support. The pure enantiomers of trans-7 showed moderately large specific rotations ([alpha]D(25) = -330 and +320 degrees), but the specific rotations for the enantiomers of 13 were unexpectedly small ([alpha]D(25) = -23 and +23 degrees). Computational studies suggest that the latter result is due to presence of a minor conformation of 13 possessing a larger rotation of opposite sign than the major conformation. Both 7 and 13 showed strong circular dichroism and moderately strong circularly polarized luminescence. A byproduct of these syntheses was 9,10,19,21-tetraphenyldiphenanthro[9,10-b:9,10-h]carbazole (15), a very crowded carbazole that exhibits an 81 degree end-to-end twist but is not resolvable. In the second approach, the large, twisted, polycyclic aromatic ligand 9,10,11,12,13,14-hexaphenylbenzo[h]naphtho[2,3-f]quinoline (21, an aza-2) was used to prepare the chiral, cyclometallated iridium(III) complex 4. The ligand 21 was prepared via an unusually stable benzannulated norbornadienone, for which the free energy of activation for decarbonylation was a remarkable 33.5 kcal/mol. The iridium complex 4 proved to be configurationally stable and resolvable by analytical HPLC on chiral supports, but the low solubility of 4 prevented its resolution on a preparative scale. A much more soluble dibutyl analogue of 4 (complex 28) was then prepared, but it was not resolvable on any of the available media.

Intense Optical Activity from Three‐Dimensional Chiral Ordering of Plasmonic Nanoantennas

“…[5][6][7][8][9][10] In the present study, we obtained outstanding SP-CDs from NRs in fluid suspensions with g-factors as high as 0.022 covering a wide Vis-NIR range. [29] This value is comparable with the highest g-factors reported for molecules such as polyaromatic compounds (0.05), [30] alleno-acetylenic macrocycles (0.01), [31] and protein complexes (0.06). [32] The potential of localized plasmons in generating strong SP-CD signal is expected to be most fully realized for nanostructures with sizes in the hundred-nanometer range (such as a dimer of NRs presented herein), where the dimensions are commensurate with the intrinsic helicity of incident light.…”

From individual to collective chirality in metal nanoparticles

“…However, outstanding SP-CD values were recently reported for assemblies of anisotropic gold nanorods (NRs) with g-factors as high as 0.02 covering a wide range of the vis/NIR spectrum [34]. This value is comparable with the highest g-factor reported for organic molecules such as polyaromatic compounds (0.05) [42], alleno-acetylenic macrocycles and oligomers (0.01) [43,44], and protein complexes (0.06) [45].…”

Synthesis, Optoelectronic and Self‐Assembly Properties of Diazadioxaacene Derivatives

“…The as-formed twistacenes and their derivatives with the peripheralp henyl groups can enhance the molecular stability and optimize the optical properties. [8] For example, Zhang and Wudl groups reported af amily of twistacenes that presented promising electroluminescent properties. [9] Xiao and co-workerss ynthesized al ibrary of small twistacene-functionalized dendrons and hyperbranched polymers where these three-dimensional architecture can suppress the intramolecular and intermolecular p-p stacking interactions in large part.…”