The structural and spectroscopic properties of 2,4,6-trinitro-diphenylamine and 2,4,6-trinitro-N-methyl-diphenylamine

The structural properties of 2,4,6-trinitro-diphenylamine (I) and 2,4,6-trinitro-N-methyl-diphenylamine (II) are determined by single crystal diffractometry and refined toR factors of 0.0282 for (I) and 0.04213 for (II). (I) crystallizes in the monoclinic space groupP21/n,Z=4, witha=11.436(5),b=7.674(2),c=15.083(4) Å,β=106.47(2)°, and (II) inP21/c,Z=4, witha=12.654(5),b=7.371(1),c=15.083(4) Å,β=101.76(2)°. The amino nitrogens show in both cases bond distances and angles typical of an sp2 character. The presence of the proton on the amino nitrogen constrains ano-nitro group into a more planar geometry than that of the methyl derivative, uv/visible spectral data of both compounds are discussed. The methyl group on the amino nitrogen, of derivative (II) compared with that of (I) produces a relevant red shift which cannot be related to the simple differences in the geometry of the two molecules