The crystal and molecular structure of phenothiazine-10-propionic acid

The crystal structure of phenothiazine-10-propionic acid, C₁₂H₈SNC₂H₄COOH, was determined from three-dimensional X-ray diffraction data collected with a manual diffractomer using MoKα (λ 0.71069 Å) radiation. The space group is P2₁/c with a = 7.888 (2)Å, b = 8.703 (2)Å, c = 19.700 (8)Å, β = 101.42 (1)°, Z = 4, D_meas = 1.35(2) g. cm^?3 and D_calc = 1.36 g. cm^?3 at 23°. The structure was determined by the direct method and refined with 500 observed reflections by full-matrix least squares to an R of 0.072. The molecule is folded along the S-N axis and the dihedral angle is 136.5°. The C-S-C angle is 98.5(7)° and the average C-S bond is 1.77(2)Å. The shortening of the C-S bond, the small value of the C-S-C angle and the folding of the molecule are typical of the phenothiazine class of compounds and are assumed to be due to sulfur d orbital participation in ring bonding.