Studies of the electronic structure of 4-N-cytosine derivatives by NMR-NQRdouble resonance spectroscopy

Results concerning the electronic structure of five cytosine derivatives ob tained by the NMR-NQR double resonance technique on nitrogen nuclei are rep orted. NMR-NQR spectra of the five cytosine derivatives were taken at 120 K . The influence of substitution at the 4-N position of the cytosine ring wa s analysed by NMR-NQR. According to the results of the study, the amine gro up, which acts as a pi electron acceptor in most molecular systems, in phen ylcytosine and naphthylcytosine becomes an electron donor, while the aromat ic rings, which usually compensate for electron density changes in cytosine , act as electron accepters. When the aromatic substituents of 4-N-cytosine are separated by a -CH2CH2- chain, the density redistribution is reduced. Copyright (C) 1999 John Wiley & Sons, Ltd.