Ring-closing olefin metathesis of 2,2′-divinylbiphenyls: A novel and general approach to phenanthrenes
(Chemical Equation Presented) The ring-closing olefin metathesis (RCM) of 2,2′-divinylbiphenyls, using a second-generation RCM ruthenium-based catalyst, leads to differently substituted phenanthrenes in quantitative yield under very mild reaction conditions, independent of both nature and position of the groups present on the biphenyl moiety.
Iuliano, Anna,Piccioli, Paolo,Fabbri, Davide
p. 3711 - 3714
(2007/10/03)
Effects of additional linkers in biphenyl-4,4′-dinitrene on the low-lying singlet-triplet energy gap and zero-field splitting
Perturbation effects of additional linkers on the spin-spin coupling in biphenyl-4,4′-dinitrene (1) were examined by introducing a linking group between 2- and 2′-positions of 1. Five different doubly linked systems showed triplet ESR spectra corresponding to quinonoid dinitrenes. Curie law analyses suggested that all those triplet states were thermally excited triplet states. In addition, the singlet-triplet energy gaps, which were determined by the Curie law analyses, were well correlated with their corresponding zero-field-splitting (zfs) D values. The result could be explained by the stability of dinitrene character which is estimated from the resonance energy of the intervening π-system. Our semiempirical molecular orbital calculations supported the experimental correlation between the singlet-triplet energy gap and the zfs D value.
Nimura,Kikuchi,Ohana,Yabe,Kondo,Kaise
p. 2083 - 2088
(2007/10/03)
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