Structural investigation of 1-amino-2,4,6-trinitrobenzenes in the solid state and in solution

The crystal structure of 1-pyrrolidino-2,4,6-trinitrobenzene3, 1-morpholino-2,4,6-trinitrobenzene4 and 1-piperidino-2,4,6-trinitrobenzene5 have been determined by single-crystal X-ray diffraction data and the structure in solution was investigated by UV-visible spectrophotometry and13C nmr. The three compounds are monoclinic, space groupP2i/n. Unit cell dimensions area=6.6660(1),b=8.612(1),c=20.696(3) Å, β=90.73(1)o, andDc=1.58 g cm−3 for compound3;a=7.090(2),b=21.493(9),c=8.298(3) Å, β=101.27(1)o, andDc 1.60 g cm−3 for compound4 anda=10.426(1),b=10.038(1),c=12.291(1) Å, β=90.04(1)o withDc=1.53 g cm−3 for compound5 forZ=4. In the solid state, differences regarding the planarity of the aromatic ring in the three substrates were found. Rotation of theortho-nitro groups and of the amino group out of the aromatic plane was observed both in the solid state and in the solution. Greater coplanarity of the two rings was found in3 than in4 and5.