A new series of star‐shaped bipolar host molecules, tris(4′‐(1‐phenyl‐1H‐benzimidazol‐2‐yl)biphen‐yl‐4‐yl) amine (TIBN), tris(2′‐methyl‐4′‐(1‐phenyl‐1H‐benzimida zol‐2‐yl)biphenyl‐4‐yl)amine (Me‐TIBN), and tris(2,2′‐dimethyl‐4′‐(1‐phenyl‐1H‐benzimidazol‐2‐yl)biphenyl‐4‐yl)amine (DM‐TIBN), that contain hole‐transporting triphenylamine and electron‐transporting benzimidazole moieties are designed based on calculations using density functional theory and successfully prepared. The theoretical calculation of energy levels of TIBN derivatives affords helpful ideas to design molecules with a favorable localization of highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) levels and a predefined enhancement of the triplet energy gap. The TIBN derivatives are employed as hosts to fabricate phosphorescent organic light‐emitting diodes (OLEDs) by the two methods of spin‐coating and vacuum deposition. Notably, the spin‐coated Me‐TIBN and DM‐TIBN devices exhibit a much better performance than the vacuum‐deposited ones, in which the spin‐coated DM‐TIBN device (47 500 cd m−2, 27.3 cd A−1, 7.3 lm W−1) is outstanding with respect to other seminal work for solution‐processed OLEDs. More importantly, the new concept of localizing HOMO and LUMO levels for bipolar molecules is illustrated, and a facile strategy to tailor the energy levels by breaking the conjugation of hole‐ and electron‐transporting moieties is demonstrated.

Two solution-processible bipolar molecules, tris(3′-(1-phenyl-1H-benzimidazol-2-yl)biphenyl-4-yl)amine (TBBI) and tris(2-methyl-3′-(1-phenyl-1H-benzimidazol-2-yl)biphenyl-4-yl)amine (Me-TBBI), bearing both hole-transporting triphenylamine and electron-transporting benzimidazole moieties were newly prepared. TBBI and Me-TBBI possess excellent thermal stability with high glass-transition temperature (T g ) of 148 and 144 °C, and the decomposition temperatures (T d ) of 552 and 515 °C in nitrogen, respectively. They exhibit good solubility in common solvents due to the metastructured and star-shaped configuration allowing a solution processing. TBBI and Me-TBBI were employed to fabricate phosphorescent organic light-emitting diodes (OLEDs) as the host materials doped with the guest of Ir(ppy) 3 by spin coating with a single-layer structure. The solution-processed Me-TBBI device exhibited an improved performance relative to TBBI arising from the complete charge localization of HOMO and LUMO and an increase in the singlet-triplet (S 0 -T 1 ) energy gap. The performance of spin-coated Me-TBBI device (16400 cd m -2 , 27.4 cd A -1 , 4.5 lm W -1 ) is outstanding with respect to other work for fully solution-processed OLEDs with the similar single-layer structure.

The electronic structures of eight bathophenanthroline derivatives were elucidated by DFT calculations, and four representatives of which CZBP, m-CZBP, m-TPAP, and BPABP were synthesized and employed as the hosts to afford highly efficient phosphorescent OLEDs. The calculated molecular orbital energies agree well with the experimental results, which further demonstrates that the localization of HOMO and LUMO at the respective hole- and electron-transporting moieties is desirable in bipolar molecular designs.

We successfully prepared a series of thermally stable polyimides (PIs) with low dielectric constant (k) by introducing bulky diphenyl fluorenylidene moieties in backbone. The lowest k was found to be 2.77 among non‐fluorinated PIs and 2.35 among fluorinated ones. In order to prove the lowest limit of k in PIs, we prepared soluble and thermally stable polyarylenes (PArs) without polar imide linkage with the same aromatic moieties by coupling polymerization. The lowest k was 2.7 without fluorine (F) and 2.2 with F atom, which showed also promising for low k materials. From these results, PIs we prepared were estimated to the lowest k values among PIs. On the basis of statistics on these results, we could express contour lines of k as a function of imide concentration and F content with high correlation factor (r= 0.96) in PIs and PArs.

Novel imidazole-appended coupled β-cyclodextrin (6) was prepared by the condensation of 6-deoxy-6-(l-histidylamino)-β-cyclodextrin and 6-(carboxymethylthio)-6-deoxy-β-cyclodextrin with dicyclohexylcarbodiimide. The enzyme-like activities of 6 were studied by measuring the rates for the hydrolysis reaction of some kinds of p-nitrophenyl alkanoates (C2, C3, C6, and C12). 6 showed large acceleration ability and substrate specificity for only p-nitrophenyl C6 ester.