(2Z,4Z,6Z,8Z)-Thionine or Thionine is an unsaturated heterocycle of nine atoms, with a sulfur replacing a carbon at one position. Thionine is a partially aromatic compound.12.27 Nine-Membered Rings, D. O. Tymoshenko

See also Azonine Thiepine Cyclononatetraene Thiophene Oxonine References