2 research outputs found
Probing Intramolecular CH−π Interactions in <i>o</i>-Quinodimethane Adducts of [60]Fullerene Using Variable Temperature NMR
Several <i>o</i>-quinodimethane adducts of
[60]Âfullerene
were synthesized and their intramolecular aryl CH–fullerene
Ï€ interactions were studied using variable temperature-NMR (VT-NMR).
Evaluation of the rate constants associated with the first-order transition
states for cyclohexene boat-to-boat inversions enables quantification
of Δ<i>G</i><sup>⧧</sup> values for each inversion.
A comparison between two constitutional isomers, only one of which
is capable of intramolecular CH−π interactions, provides
a lower limit of 0.95 kcal/mol for each aryl CH–fullerene π
interaction
A Robust, High-Temperature Organic Semiconductor
We introduce a new pentacene-based
organic semiconductor, 5,6,7-trithiapentacene-13-one (TTPO). TTPO
is a small-molecule organic semiconductor that is simple to synthesize
and purify, readily crystallizes, melts in air from 386–388
°C without decomposition, and is indefinitely stable against
degradation in acid-free solution. TTPO has a high molar absorptivity,
optical and electrochemical HOMO–LUMO gaps of 1.90 and 1.71
eV, respectively, and can be thermally evaporated to produce highly
uniform thin films. Its cyclic voltammogram reveals one reversible
oxidation and two reversible reductions between +1.5 and −1.5
V. The crystal structure for TTPO has been solved and its unique parallel
displaced, and head-to-tail packing arrangement has been examined
and explained using high-level density functional theory. High-resolution
scanning tunneling microscopy (STM) was used to image individual TTPO
molecules upon assembly on a pristine Au(111) surface in ultrahigh
vacuum. STM images reveal that vapor-deposited TTPO molecules nucleate
in a unique stacked geometry with a small acute angle with respect
to Au(111) surface. Preliminary TTPO-based bilayer photovoltaic devices
show increases in short circuit current density upon heating from
25 to 80 °C with a concomitant 4–160-fold increase in
power conversion efficiencies. TTPO has the potential to be used in
thin-film electronic devices that require operation over a wide range
of temperatures such as thin-film transistors, sensors, switches,
and solar cells