Charge-Transfer Interaction and Molecular Arrangement in the Crystals of 2-(p-Nitrophenoxy)ethyl Ethers and Amines

Article abstract of DOI:10.1246/bcsj.68.3247

X-Ray crystallographic analysis of the Acceptor- (CH2)2-Donor type compounds, p-O2NC6H4OCH2CH2OAr (Ar=m- and p-Me2NC6H4, and m-Et2NC6H4) and p-O2NC6H4OCH2CH2N(CH3)C6H4OMe-p, has been carried out.Among these, only m-dimethylamino derivative (1) gives dark red prisms in which a close arrangement of the electron-donor and acceptor groups is observed.With regard to the central C-C bond in ArO-C-C-OAr' or ArO-C-C-NAr', three of the above-mentioned four compounds show gauche conformation: 1 is the exception.The preference of the gauche, probably characteristic of O-C-C-O (or -N) group, is suggested to be due to a small energy difference between the trans and gauche forms by using the MM2 and the PM3 approximation.Charge-transfer interaction energy in 1 as an intermolecular force is estimated to be barely large enough to make the trans conformation favorable over the gauche.