X-Ray structures and physical properties of tropone-annelated p-benzoquinones substituted with X-Ar groups α to tropone carbonyls and first examples of the trione substituted with an electron-withdrawing group

Abstract

6,8-Dibenzyl-, 6,8-bis(p-dimethylaminobenzyl)- and 6,8-diphenoxy-benzocycloheptene-1,4,7-triones have been synthesized and their physical properties (IR, UV, NMR spectra and redox potentials) compared with those of 6,8-bis(phenylthio)benzocycloheptene-1,4,7-trione. The first redox potentials fall in the order OPh > CH₂Ph > SPh > CH₂C₆H₄NMe₂-(p) but the second fall in the order OPh > SPh > CH₂Ph > CH₂C₆H₄NMe₂-(p), the latter order is in accord with that of their σ_I values. The molecular structures of the first three compounds, determined by the single crystal X-ray analyses, were found to be very similar, except for the bond angle at the atom connecting tropone with the phenyl rings. The crystal structures of compounds 4 and 5 were almost identical, but were quite different from that of the SPh analogue 3. Success in the synthesis of benzocycloheptene-1,4,7-triones substituted with an electron withdrawing group on C-6 is also described. Electron transfer was not appreciable in a crystal of the complex of benzo[1,2;4,5]dicycloheptene-3,6,9,12-tetrone with TTF according to the crystal structure analysis.