spccira were obscrvcd lor the rxhcal nnlon of 1.8d~phenylnaphthalcnc (I), wth rclatcd nd~c.d ~ntons of l.8dldcutenophenylnaplithalene and 1,8-bt&~-tolyl)-naphthalcne. Observed hypcrlinc coupbng conswtts were tnterprctcd tn terms of transannulttr tnlcrachon bctwccn rr systems bclongtng to the two bcnzcnc rings of anton I. Recently, transannular electron mteractions in radical anions and cations of cyclophane derivatives [l-7] and aromatic dlmer cations [8-131 have been studied in detail using the ESR techmque. In these radicals, the two n systems he parallel and are super-Imposed on each other. According to the results of an X-ray crystallographic analysis of 1,8-diphenylnaphthalene (I), ths molecule eslsts prlmardy in the conformation Illustratcd in fig. I with the phenyl rings approximately parallel to one another and approximately perpendlcular to the plane of the naphthalene rmg [ 141.
Consequently, electron exchange interactlon may be expected to exist between the two benzene rings and, furthermore, the conventlonal a-orbital overlap (I.e. resonance interaction) between each benzene ring and the naphthalene system may be prevented. In 1, therefore, not only transannular interaction between the two phenyl rings but also two mutually perpendicular n-electronic systems could be expected. Hence, the physical and chenucal properties of compound I have been extensively studied usmg several