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.

In view of increasing interest in light-emitting materials, we have investigated the light-emitting characteristics and occurrence of conjugation between arms of star-shaped rigid molecules that comprise a 1,3,5-triethynylbenzene core and methoxy group-substituted oligo(p-phenylethynylene) arms. Consequently, we achieved the ultimate goal (Phif approximately 1.0, log epsilon > 5) for organic molecules with respect to light-emitting ability by creating very intense violet-blue (8, Phif = 0.97, log epsilon = 5.11) and blue (9, Phif = 0.98, log epsilon = 5.29) bright light-emitters. Also, pi conjugation was found to occur between the arms of 9 despite the meta-substituted system. We found a linear relationship of kr (with positive slope) and kd (with negative slope) with the number of dimethoxyphenyleneethynylene units for MMPT (4, 6, 8) and DMPT (5, 7, 9) homologues and the contrasting solvent effect on lambdaem of 8 and 9. It is also interesting that lambdaabs, epsilon, lambdaem, and Phif of 9 are greater than those of the corresponding banana- and rod-shaped molecules.