CYCLIC ARYLENEAZACHALCOGENES .10. SYNTHESIS, MOLECULAR-STRUCTURE AND PHOTOELECTRON-SPECTRUM OF 6,7,8,9-TETRAFLUORO-1,3,5,2,4-BENZOTRITHIAZEPINE AND ATTEMPTED SYNTHESES OF RELATED LARGER SIZE HETEROCYCLES

The 14 pi-electron title compound 7 has been synthesized by two differ ent ring-closure approaches. Its structure has been determined by X-ra y diffraction to be planar within +/-0.018 Angstrom. The He(I) photoel ectron spectrum of the title compound is assigned by Koopmans' correla tion with PM3 eigenvalues based on the structural data, and by the pi- perfluoro effect observed. The pi-system can be rationalized by hetero atom first-order perturbation, which reduces the cyclic pi-delocalizat ion. Replacement of the four fluorine substituents by hydrogen affects neither the long-wavelength absorption band in the UV/Vis spectrum no r the delta(15)N Shift in the N-15-NMR spectrum. The synthesis of 20 p i-electron heterocycles related to the title compound has been attempt ed.