Existence of aromatic sp(2) C-H center dot center dot center dot O=C intramolecular interaction similar to hydrogen bond

A H-1 NMR signal shifted drastically to down field (delta similar to 10.0) at the bay area and in close proximity to C=O group for H-1 was observed through complete assignments of H-1 NMR spectra for pyridino- and benzobenzanthrones. It is concluded that this phenomenon is due not only to the anisotropy effect of C=O plus aromatic ring current effect, but also to the electrostatic attraction of C-H (delta+).. O(delta-)=C interaction. The evidence for the sp(2)C-H ... O=C intramolecular interaction similar to hydrogen bond has also been given by EI-MS and MS/MS (CID) spectroscopy and IR spectroscopy, as well as MNDO-PM3 calculations. This new kind of interaction might be oiled 'quasi-hydrogen bond'.