N‐Heteropolycycles are among the most promising candidates for applications in organic devices. For this purpose, a profound understanding of the low‐energy electronic absorbance and emission characteristics is of crucial importance. Herein, we report high‐resolution absorbance and fluorescence spectra of pentacene (PEN) and 6,13‐diazapentacene (DAP) in solid neon obtained using the matrix‐isolation technique. Accompanying DFT calculations allow the assignment of specific vibrationally resolved signals to corresponding modes. Furthermore, we present for the first time evidence for the formation of van der Waals dimers of both substances. These dimers exhibit significantly different optical characteristics resulting from the change of electronic properties evoked by the incorporation of sp2 nitrogen into the molecular backbone.
The synthesis, property evaluation,a nd single crystal X-ray structures of four 5,7,12,14-tetrafunctionalized diazapentacenes are presented. The synthesis of these compounds either starts from tetrabromo-N,N-dihydrodiazapentacene or from ad iazapentacene tetraketone.P dcatalyzed coupling or addition of al ithiuma cetylide gave the precursors that furnish, after furtherr edox reactions, the diazapentacenes as stable crystalline materials. The performance of the tetraphenyl-substituted compoundas n-channel semiconductor was evaluated in organic field effect transistors.
Naphthothiadiazoles
are promising electron acceptors for applications
in organic semiconductor-based (opto)electronic devices. Here, we
studied the structural and electronic properties of naphthothiadiazole
(NTD) derivatives adsorbed on Au(111) in the monolayer and thin films
using temperature-programmed desorption as well as vibrational and
electronic high-resolution electron energy loss spectroscopy. In addition,
we performed state-of-the-art quantum chemical calculations to further
illuminate electronic properties. In the monolayer and multilayer
coverage regime, the NTD derivatives adsorbed in a planar fashion
with the molecular backbone oriented parallel to the gold surface.
Several singlet and the first triplet transition energies are determined.
The optical gap (S0 → S1 transition)
in the nonhalogenated parent NTD is found to be 2.6 eV, whereas it
is reduced by 200 meV in the chlorinated and brominated NTD. All experimentally
observed singlet and triplet transition energies are reduced due to
halogenation, which is underlined by theory.
We efficiently synthesized otherwise difficult to obtain 2,3-and 2,3,6,7-halogenated anthracenes with diverse east/ west substituents. Key steps involve the (i) Vollhardt cyclization of bis(propargyl)benzenes with bis(trimethylsilyl)acetylene, (ii) halodesilylation introducing chlorine, bromine, or iodine substituents, and (iii) dehydrogenation. Pd catalysis allows selective functionalization at the anthracenes' east/west positions. A tetrahydropentacene is synthesized and derivatized via the same strategy, employing tetrapropargylbenzene.
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