The Carbon 13 NMR Spectra and Electronic Structure of 3H-Phenothiazin-3-one and Its Methyl Derivatives

Article abstract of DOI:10.1246/bcsj.57.510

The 13C NMR chemical shifts of 3H-phenothiazin-3-one (1) and eleven of its methyl derivatives are reported.The effect of including sulfur 3d orbitals is discussed in relation to the 13C chemical shifts.The chemical shifts of 1 can be explained in terms of both the succesive polarization of the long ?-conjugated framework promoted by the carbonyl group and the contribution of the sulfur d-orbitals.The 13C chemical shifts gave a better correlation with the CNDO/2 ?- and total electron densities calculated by means of the sp-basis set than by means of the spd-basis set, but an improved correlation was obtained by reducing the extent of d-orbital participation on sulfur.From the correlation of the 13C chemical shifts with the CNDO/2 sp ?- and the total electron densities of all carbons of 1 and monomethyl derivatives, the proportionality constants of -300 and -180 ppm/e respectively were obtained.