DOI: 10.1021/jp0628737

An ab Initio Study of 15N-11B Spin-Spin Coupling Constants for Borazine and Selected Derivatives

Ab initio equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations have been performed to investigate substituent effects on coupling constants for borazine and selected substituted borazines. For molecules in which F atoms are not bonded to adjacent atoms in the ring, F substitution increases the one-bond ¹¹B−¹⁵N coupling constants involving the atom at which substitution occurs but leaves the remaining one-bond B−N coupling constants essentially unchanged. For these molecules, the magnitudes of one-bond B−N coupling constants are only slightly dependent on the number of F atoms present. Fluorine substitution at adjacent B and N atoms in the borazine ring further increases the one-bond B−N coupling constant involving the substituted atoms and has the same effect on the other one-bond coupling constants as observed for corresponding molecules in which substitution occurs at alternate sites. In contrast to the effect of F substitution, substitution of Li at either N or B decreases one-bond B−N coupling constants relative to borazine. The effects of F and Li substitution on one-bond B−N coupling constants for borazine are similar to F and Li substitution effects on ¹³C−¹³C coupling constants for benzene.