Three [(9-anthryl)vinyl][(9-phenanthryl)vinyl]benzene (APB) position isomers were synthesized and compared. The molecular configuration exhibits an extraordinary ability to affect polymorphism probability, unexpected solvatochromism, and aggregation-induced emission property. With the substitution changing from para-, ortho-, to meta-position, the polymorph number changes from 1, 2, to 3. Both 1,2-APB and 1,3-APB display a temperature-induced crystal-to-crystal phase transition. Furthermore, a pair of concomitant conformational polymorphs were obtained for 1,3-APB. Crystal structure analyses reveal that the steric hindrance between the two substituents leads to different molecular conformation and packing pattern. The unexpected solvatochromism is attributed to the strong electron-withdrawing ability of anthracene against phenanthrene, which produces permanent dipole moment. The solvatochromic degree is determined by the conjugative effect which varies with substitution position. 1,4-APB displays the most remarkable solvatochromic effect. Furthermore, it shows a totally different emission decay dynamics from 1,2-APB and 1,3-APB in polar solvents. Interestingly, the solution fluorescence quantum yields of these three isomers all increase with increased solvent polarity, displaying a negative solvatokinetic effect. Both 1,2-APB and 1,4-APB display an aggregation-induced emission enhancement. Though 1,3-APB is quenched in the solid state, it emits most efficiently amongst these three isomers either in solution or in solid state. The effect of the medium environment on the radiative process plays a vital role in determining their different aggregation-induced emission behaviours.

The molecular shape exerts remarkable effects on solubility, polymorphism, crystal packing and optoelectronic properties – searching for 3D organic semiconductors.

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The different combinations of five benzene rings and two CC double bonds yield four isomers: 4,4″-bistyryl-p-terphenyl (BSTP), and 1 ,4-bis[2-(p-biphenyl)vinyl]benzene (BBVB). The position variations of two CC double bonds affect aggregate microstructures, as well as thermal and optoelectronic properties. Except BBVB, the other three isomers all have a phase transition upon heating. X-ray diffraction and optical absorption analyses reveal that the molecules of four isomers all take an H-aggregation in the crystalline solid. However, the microstructures are different for orientation disorder exists in STVB crystals. Both the absorption and emission spectra of these four isomers display a bathochromic shift when the position interval between two double bonds ranges from three, two, to one benzene rings. The CH 2 Cl 2 solutions of these four isomers are highly emissive with quantum yields ranging from 83% to 96%. Intriguingly, though the molecules crystallize into an H aggregation, the quantum yields of polycrystalline samples are also extraordinarily high, from 73% to 94%. All the isomers display moderate hole-transport ability. Different-oriented grains coexist in the vacuum-deposited films, which play different roles in the carrier transport.