title: Advantage of the N-alkylation strategy for retaining the molecular planarity for oligothiophene/imidazole/1,10-phenanthroline-based heterocyclic semiconducting and fluorescent compounds.
abstract: 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.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures Laboratory, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China), Fax: (+86) 2583314502.
authors.forename: Yu-Xin
authors.initials: YX
authors.lastname: Peng
authors.forename: Tao
authors.initials: T
authors.lastname: Tao
authors.forename: Xiao-Xu
authors.initials: XX
authors.lastname: Wang
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Ma
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
keywords: alkylation; crystal growth; fluorescence; molecular planarity; semiconductors