Inclusion compounds of nitrosobenzenes with cholic acid and deoxycholic acid

The crystalline inclusion compounds of cholic acid (CA) and deoxycholic aci d (DCA) with several nitrosobenzenes were prepared. The IR spectra and crys tal structures of these compounds confirmed inclusion of the monomeric form of the C-nitroso compounds. The DCA compounds have 2: 1 host:guest stoichi ometry and P2(1) symmetry. Guest molecules are enclosed in channels and dis ordered. In the CA-nitrobenzene inclusion compound (1-CA) the host:guest st oichiometry is I : 1. The host molecules form typical CA bilayer aggregates and guest molecules are accommodated in helicoidal channels. The guest nit roso group is not coplanar with the phenyl ring; the torsion angle on the C -N bond is 8.6(8)degrees. The solid-state circular dichroism spectrum of 1- CA shows the negative Cotton effect at 780 nm corresponding to the n-pi* el ectronic transition that can be associated with the P helicity of the guest molecule. The extremely weak magnitude of the Cotton effects exhibited by the DCA complexes points to a nearly planar arrangement of the NO group and the phenyl ring in the guest molecules.