Synthesis, photophysical and electrochemical properties of 2,8-diaryl-dibenzothiophene derivatives for organic electronics

Dibenzothiophene-Containing Thiacarbaporphyrinoids

A new type of expanded dibenzothiophene-containing thiacarbaporphyrinoid containing one dibenzothiophene, two p-phenylene, one thiophene, and two pyrrole rings connected via four meso carbons and two direct bonds was synthesized over a sequence of six steps starting with commercially available dibenzothiophene. The X-ray structure obtained for one of the macrocycles revealed that the macrocycle was very nonplanar and the two p-phenylene rings and dibenzothiophene unit were deviated from the mean plane, whereas the thiophene ring attained inverted conformation and was facing toward outside the macrocyclic core. The X-ray structure also revealed that the dibenzothiophene unit of the macrocycle maintained its π-electron delocalization and did not extend the π-electron delocalization with the rest of the macrocycle, and the effective π-conjugation was present only in the lower part of the macrocyclic core, i.e., the thiatripyrrin moiety. The spectral and theoretical studies support the nonaromatic nature of the macrocycles. The macrocycles exhibit one strong absorption band at ∼430 nm and one broad absorption band in the 500-800 nm region, which were bathochromically shifted in diprotonated derivatives which absorb strongly in the visible-NIR region. The electrochemical studies indicated the electron-rich nature of the macrocycles and the theoretical studies corroborated the experimental observations.

Synthesis of Tellurium-Containing π-Extended Aromatics with Room-Temperature Phosphorescence

A synthesis of tellurium-embedded π-extended aromatics from tellurium powder and readily available cyclic diaryliodonium salts has been developed. The versatility of this method has been demonstrated by the synthesis of various functionalized dibenzotellurophenes (DBTe's), a ladder-type π-system, and a heterosumanene. These compounds demonstrated good air/moisture stability and high thermal stability. Remarkably, many DBTe's exhibited interesting tunable room-temperature phosphorescence (RTP) in the solid state.

Benzophenanthrothiophenes: Syntheses, Crystal Structures, and Properties

A new class of polycyclic heteroarenes based on benzo[3,4]phenanthro[1,2-b]benzo[3,4]phenanthro[2,1-d]thiophene (BPBPT) was prepared from polyaryl thiophenes via regioselective Scholl reactions. The molecular frameworks of these compounds exhibited twisted bridges and near-cofacial packing motifs with oppositely or parallel π-stacked structures depending on the substituents on the periphery. Theoretical calculation of electronic coupling and charge mobility was carried out on the basis of the single-crystal structures. Single crystals of selected benzophenanthrothiophenes were used in p-channel field-effect transistor device fabrication, from which the highest mobility was measured as 2.03 cm² V^-1 s^-1 from Flu-BPBPT.

Aromatic homologation by non-chelate-assisted Rh(III)-catalyzed C-H functionalization of arenes with alkynes

Larger condensed arenes are of interest owing to their electro- and photochemical properties. An efficient synthesis is the catalyzed aromatic annulation of a smaller arene with two alkyne molecules. Besides difunctionalized starting materials, directed C-H functionalization can be used for such aromatic homologation. However, thus far the requirement of either pre-functionalized substrates or suitable directing groups were limiting this approach. Herein, we describe a rhodium(III)-catalyzed method allowing the use of completely unbiased arenes and internal alkynes. The reaction works best with copper(II) 2-ethylhexanoate and decabromodiphenyl ether as the oxidant combination. This aromatic annulation tolerates a variety of functional groups and delivers homologated condensed arenes. Aside from simple benzenes, naphthalenes and higher condensed arenes provide access to highly substituted and highly soluble acenes structures having important electronic and photophysical properties.