2 research outputs found
Synthesis and Mesomorphic Properties of Novel Dibenz[<i>a</i>,<i>c</i>]anthracenedicarboximides
The
synthesis and characterization of a novel series of dibenz[<i>a</i>,<i>c</i>]anthracenedicarboximides
is reported. Incorporating electron-withdrawing imides bearing flexible
alkyl chains allowed for the production of materials that self-assemble
into hexagonal columnar mesophases featuring broad temperature ranges.
Furthermore, longer <i>N</i>-alkyl chains or branched <i>N</i>-alkyl chains broaden the mesophase temperature range by
lowering the melting transition without greatly influencing the clearing
point
Pi-Extended Ethynyl 21,23-Dithiaporphyrins: A Synthesis and Comparative Study of Electrochemical, Optical, and Self-Assembling Properties
21,23-Dithiaporphyrins were synthesized
containing pi-extending
ethynyl substituents at the meso positions. These porphyrins displayed
highly bathochromic and broadened absorbance profiles spanning 400–900
nm with molar absorptivities ranging from 2500 to 300,000 M<sup>–1</sup> cm<sup>–1</sup>. Electrochemically, these ethynyl dithiaporphyrins
undergo a single oxidation at 0.44 or 0.57 V and reduction at −1.17
or −1.08 V versus a ferrocene/ferrocenium internal standard
depending on the type of functionalization appended to the ethynyl
group. DFT calculations predict that the delocalization of the frontier
molecular orbitals should expand onto the meso positions of the ethynyl
21,23-dithiaporphyrins; shrinking the HOMO–LUMO energy gap
by destabilizing the HOMO energy. Indeed, the DFT results agree with
our optical and electrochemical assessments. Finally, differential
scanning calorimetry combined with cross-polarized optical microscopy
and powder X-ray diffraction was used to assess the ability of these
porphyrins for long-range order. For the ethynylphenyl alkoxy 21,23-dithiaporphyin,
birefringent, soft-crystalline-like domains were observed by polarized
microscopy, which are marginally sustained by a low-level of crystallinity
detected in the XRD, suggesting that long-range ordering is possible.
Overall, ethynyl 21,23-dithiaporphyrins are able to harvest much lower
energy light and possess lower oxidation and reduction potentials
compared to their pyrrolic analogues, which are desirable properties
for applications in organic electronics