The synthesis, crystal structures and photophysical properties of a series of novel 4,6-diphenyl-1,9-anthrazolines

The synthesis and properties of a series of nine new 4,6-diphenyl-1,9-anthrazolines molecules 1a–1i are reported. Compounds 1a–1i were synthesized by Friedländer condensation of 4,6-dibenzoyl-1,3-phenylenediamines and acetyl-functionalized compounds in the presence of polyphosphoric acid as catalyst, in yields ranging from 60% to 94%. The 4,6-diphenyl-1,9-anthrazolines are thermally robust with high decomposition temperatures (>371.0 °C) and high melt transitions (215.1–322.8 °C). Compounds 1a and 1f crystallized in the triclinic system with the space groups P-1. All of them show the lowest energy absorption bands (λmaxAbs: 397–454 nm), revealing low optical band gaps (2.55–3.00 eV). The compounds emit blue fluorescence with λmaxEm ranging from 432 to 493 nm in dilute toluene solution. 4,6-Diphenyl-1,9-anthrazolines 1a–1i have a formal reduction potential in the range −1.02 to −1.19 V (versus SCE) and estimated electron affinities (LUMO levels) of 3.21–3.38 eV. These results demonstrate that the new 4,6-diphenyl-1,9-anthrazolines are promising thermally stable n-type semiconductors for organic electronics.

► 4,6-Diphenyl-1,9-anthrazolines are thermostable with Tg >371 °C, Tm (215–322 °C).
► They show λAbsmax from 397 to 454 nm, revealing low optical band gaps (2.5–3.0 eV).
► The compounds emit blue fluorescence with λEmmax (432–493 nm) in solution.
► 4,6-Diphenyl-1,9-anthrazolines are promising n-type organic semiconductors.