Synthesis, structures and photophysical properties of two regioisomeric phenalenocarbazoles

Synthesis, Optical, and Redox Properties of Regioisomeric Benzoheterocycles-Fused Pyrene

“…At low energy, benzo­[b]­phosphole-fused pyrenes 3 / 6 exhibit well resolved S 1 ← S 0 absorption bands, which are mainly attributed to the short-axis-polarized 1 L b transition present in the pyrene unit . The intensity of these weak bands increases with respect to pyrene (Figure ), as a consequence of the reduced symmetry . The intense S 2 ← S 0 transition corresponds to the long-axis-polarized 1 L a transition of pyrene, which is basically a HOMO–LUMO transition ( vide infra ) as previously described on substituted pyrene derivatives .…”

“…Most of the pyrene derivatives described in the literature are synthesized through Friedel-Craft reactions . However, this strategy appeared unsuccessful for the incorporation of P and Si atoms in these systems.…”

“…This led to a creative molecular engineering involving the development of new synthetic approaches for the functionalization of pyrene, the tailoring of substituents or the use of heteroatoms (molecules A and B , Figure ), or extending the π-system with fused heterocycles yielding different electronic properties (molecules C and D , Figure ). For example, regioisomeric sulfur and sulfonyl bridged phenyl-pyrene (molecules C and D with Y = S or SO 2 , Figure ) have been synthesized by Liu, Li et al They showed that the physical properties are highly dependent on the position of the substitution on the pyrene skeleton. In this context, the synthesis and the study of optical and redox properties of pyrene-heterocycle analogues ( C and D with Y = PPh or SiMe 2 , Figure ) are of high interest since phosphole and silole rings have strongly different electronic behavior compared to their S-analogs due to their low-lying LUMO energy levels and the corresponding low aromaticity …”