A novel topological strategy is described for designing amorphous molecular solids suitable for optoelectronic applications. In this approach, chromophores are attached to a tetrahdral point of convergence. Stilbenoid units were covalently linked to tetraphenylmethane, tetraphenyladamantane, or tetraphenylsilane cores using palladium catalyzed coupling methodology. Thus, reaction of E(C 6 H 5 X) 4 (E ) C and adamantane, X ) I; E ) Si, X ) Br) with styrene or 4,4′-tert-butylvinylstilbene under Heck coupling conditions yields the corresponding tetrakis(stilbenyl) (E(STB) 4 ) and tetrakis(4-tert-butylstyrylstilbenyl) (E( t BuSSB) 4 ) compounds. Similarly, reaction of 1,1-diphenyl-2-(4-dihydroxyboronphenyl)ethene or 2-(4-pinacolatoboronphenyl)-3,3diphenylacrylonitrile with tetrakis(4-bromophenyl)methane using Suzuki coupling methodology gives tetrakis-), respectively, in good yields. Compounds with more extended conjugation can also be prepared. Thus, reaction of excess 1-(4′-tert-butylstyryl)-4-(4′-vinylstyryl)benzene with C(C 6 H 4 I) 4 provides tetrakis(4-(4′-(4′′-tert-butylstyryl)styryl)stilbenyl)methane (C(4R-t Bu) 4 ) in low yield (∼20%). The more soluble analogue, tetrakis(4-(4′-(3′′,5′′-di-tert-butylstyryl)styryl)stilbenyl)methane (C(4R-2 t Bu) 4 ) is prepared similarly using 1-(3′,5′-di-tert-butylstyryl)-4-(4′-vinylstyryl)benzene and in better yield (∼80%). Alkoxy substituents can also be used to increase solubility. Tetrakis((4-(2′,5′-dioctyloxy-4′-styryl)styryl)stilbenyl)methane, C(4R-(OC 8 H 17 ) 2 ) 4 , was prepared by treatment of C(C 6 H 4 I) 4 with excess 2,5-dioctyloxy-1-styryl-4-(4′-vinylstyryl)benzene (yield ∼ 73%). The simple stilbenyl-derivatives were found by DSC measurements and powder diffraction experiments to be crystalline compounds. Comparison of single-crystal X-ray diffraction data shows that C(STB) 4 and Si(STB) 4 form isomorphous crystals. The larger E( t BuSSB) 4 , C(DPVBi) 4 , and C(DPAB) 4 compounds readily form amorphous glasses with elevated glass transition temperatures (T g ) 142-190 °C) in the absence of solvent. Extending the conjugation length of the arm leads to more stable glasses. For example, the glass transition temperature of C(4R-t Bu) 4 was measured at 230 °C. Solution phase optical spectroscopic data of E( t BuSSB) 4 (E ) C, adamantane, and Si) are characteristic of the parent distyrylbenzene chromophore. Films, however, show broad and significantly red-shifted emission spectra. In contrast, C(DPVBi) 4 gives absorption and emission spectra which are nearly identical between dilute solution phase samples and neat solid films. The emission of C(DPAB) 4 is broad and structureless, reminiscent of exciplex or excimer emission. Films of the tetramers with longer arms (C(4R-t Bu) 4 , C(4R-2 t Bu) 4 , and C(4R-(OC 8 H 17 ) 2 ) 4 ) show emission properties which are dependent on sample history. Annealing the sample at elevated temperature leads to red-shifted emission as a result of better interdigitation between the optically active fragments.
