Rigid Molecular Architectures That Comprise a 1,3,5-Trisubstituted Benzene Core and Three Oligoaryleneethynylene Arms:Light-Emitting Characteristics and pi Conjugation between the Arms

摘要

Rigid molecular architectures which consist of a trivalent core and three pi extended arms (so-called star-shaped molecules) are currently attracting considerable attention because of potential application as devices,such as light-emitting diodes (LEDs),field effect transistors (FETs),and nonlinear optics (NLO).However,with respect to the light-emitting characteristics associated with LEDs,only a few papers (dealing with the light-emitters with PHI_f < 0.86) appear in the literature.Apart from this,it should be interesting to examine if pi conjugation occurs between the arms across the 1,3,5-trisubstituted benzene core of star-shaped molecules,though such an interaction is reported for condensed polycyclic systems.Thus we have investigated the light-emitting characteristics and occurrence of pi conjugation between the arms of star-shaped rigid molecules that comprise a 1,3,5-triethynylben-zene core and methoxy group-substituted oligo(p-phenyleneethy-nylene) arms.Consequently,we achieved the ultimate goal (PHI_f approx = 1.0,log epsilon > 5) for organic molecules with respect to light-emitting ability by integrating the dimethoxyphenylacetylene unit with low PHI_f (0.29 in cyclohexane),not the fluorene unit with high PHI_f (0.74 in cyclohexane).Furthermore,we have found that pi conjugation occurs between the arms.