Bin-Bin Ma

Asymmetrical/Symmetrical D−π–A/D−π–D Thiazole-Containing Aromatic Heterocyclic Fluorescent Compounds Having the Same Triphenylamino Chromophores

A family of linear asymmetrical D-π-A and symmetrical D-π-D types of thiazole-based aromatic heterocyclic fluorescent compounds bearing various electron-donating and electron-withdrawing tails (bromo, triphenylamino, pyridyl, thienyl and benzoic acid) have been designed and prepared successfully. Synthetic, structural, thermal, spectral and computational comparisons have been carried out for related compounds because of their adjustable electronic properties. It is interesting to mention that compound 2 can be prepared from 5-bromothiazole by one-pot Suzuki-Miyaura coupling and subsequent C-H activation reactions via a 5-TPA-substituted thiazole intermediate 1. X-ray single-crystal structures of six compounds indicate that they all crystallize in the triclinic P1 space group and the thiazole core exhibits different dihedral angles with its adjacent benzene ring of the triphenylamino group (3.6(3)-40.8(3)°). The photophysical and electrochemical results demonstrate that compound 7 exhibits high electrochemical activity with a green fluorescence emission. Meanwhile, compounds 1, 2, and 6 show high luminescence quantum yields, and compound 8 exhibits excellent thermal stability (T(d(10)) = 503 °C).

Synthesis, Crystal Structure, and Physical Property of Sterically Unprotected Thiophene/Phenylene Co‐Oligomer Radical Cations: A Conductive π–π Bonded Supermolecular meso‐Helix

Sterically unprotected thiophene/phenylene co-oligomer radical cation salts BPnT(·+) [Al(OR(F))(4)](-) (OR(F)=OC(CF(3))(3), n=1-3) have been successfully synthesized. These newly synthesized salts have been characterized by UV/Vis-NIR absorption and EPR spectroscopy, and single-crystal X-ray diffraction analysis. Their conductivity increases with chain length. The formed meso-helical stacking by cross-overlapping radical cations of BP2T(·+) is distinct from previously reported face-to-face overlaps of sterically protected (co-)oligomer radical cations.

Advantage of the N-Alkylation Strategy for Retaining the Molecular Planarity for Oligothiophene/Imidazole/1,10-Phenanthroline-Based Heterocyclic Semiconducting and Fluorescent Compounds

A family of planar oligothiophene/imidazole/1,10-phenanthroline (OTIP)-based heterocyclic, aromatic, semiconducting, and fluorescent compounds with N-substituted alkyl chains (allyl, n-butyl, n-octyl, n-dodecyl, and n-cetyl) have been designed and synthesized. They all have specific N-coordination sites, various donor-acceptor spacers, good molecular planarity, suitable solubility, and high thermal stability. In comparison with conventional double β-alkylation of the thiophene ring, our results reveal that the single imidazole N-alkylation strategy for OTIPs has the advantage of maintaining the planarity of the whole molecule, in addition to improving the solubility, which can be clearly verified by the small dihedral angles between adjacent thiophene/imidazole/1,10-phenanthroline (TIP) rings in eight X-ray single-crystal structures. In particular, n-dodecyl- and n-cetyl-substituted OTIPs (7 and 8) with the same molecular length of 2.37 nm (MW =939 and 1052), show good molecular planarity with the aforementioned dihedral angles of 8.9(5) and 10.4(5)°. Furthermore, special attention has been paid to the physicochemical properties of seven symmetrical OTIPs (6-8, 13-15, and 19), including two to six thiophene rings in the middle of their molecular structures. To the best of our knowledge, this is the first synthetic, structural, and spectral investigation into the N-alkylation of OTIP-based compounds.

Visualized acid–base discoloration and optoelectronic investigations of azines and azomethines having double 4-[N,N-di(4-methoxyphenyl)amino]phenyl terminals

Two small molecular chromogenic sensors (azine MS-1 and azomethine MS-2) were synthesized for acid–base discoloration and optoelectronic investigations. It was found that the color of both sensors in solution and in the solid state changed obviously from yellow to purple and blue after treatment with acid, which could be easily detected by the naked eye. Furthermore, single-crystal conductance of MS-1 and MS-2 could be significantly enhanced after treatment with HCl gas flow. On the other hand, MS-2 showed relatively good film-forming ability and could be used as a hole transport material (HTM) in perovskite solar cells, exhibiting a power conversion efficiency (PCE) of 6.68%. To the best of our knowledge, this is the first demonstration of perovskite solar cells including a HTM based on a low-cost Schiff-base.

Simultaneous enhancement of fluorescence and solubility by N-alkylation and functionalization of 2-(2-thienyl)imidazo[4,5-f][1,10]-phenanthroline with heterocyclic bridges

A family of 2-(2-thienyl)imidazo[4,5-f][1,10]-phenanthroline (TIP) based compounds with large delocalized π systems has been designed and synthesized following the strategy of introducing alkyl chains and extending different S-, N- and O-containing aromatic heterocyclic tails. Simultaneous enhancements of the fluorescence emission and solubility in organic solvents for the resultant aromatic heterocyclic compounds 1–13 have been achieved. Analyses on twelve X-ray single-crystal structures indicate that the thiophene ring of the TIP unit in this series of compounds shows the same trans configuration with its imidazo[4,5-f][1,10]-phenanthroline core but different dihedral angles with the adjacent aromatic heterocycles. Thermal gravimetric analyses for ten imidazole N-substituted TIP derivatives reveal that they still retain good thermal stability with decomposition temperatures higher than 300 °C originating from their common TIP core, even with the introduction of the n-butyl radical in their molecular structure. Moreover, TPA and carbazole substituted compounds 2 and 9 were used as the ancillary ligands to prepare their corresponding ruthenium(II) sensitizers, BM3 and BM4, and their dye-sensitized solar cell performance was evaluated.