Theoretical study of cyclazines

Abstract

Calculations are reported for cycl[3,3,3]azine (I), the perinaphthenium anion(II), and cycl[3,2,2]azine (III), using a recently developed semiempirical SCF MO method. These indicate that (I) should be antiaromatic, with alternating bond lengths, unlike (II) or (III), and that it should have a low ionization-potential. The calculated charge-densities for (I) and (II) account well for the proton n.m.r. spectrum. A simple PMO treatment of (I) also indicates that it should be antiaromatic.