title: Luminescent organoboron ladder compounds via directed electrophilic aromatic C-H borylation.
abstract: Luminescent B-N containing conjugated ladder compounds are prepared by directed electrophilic aromatic substitution. Negishi cross-coupling reaction of 2,7-dibromo-9,9-dihexylfluorene with 6-methylpyridin-2-yl(pivaloyloxy)zinc furnishes the dipyridylfluorene precursor (1) in 44% yield. Compound 1 is then subjected to electrophilic borylation with BBr3 in the presence of iPr2NEt as a bulky base to give the tetra-coordinate ladder-type organoboron species 2-Br. Arylation of 2-Br is accomplished by addition of Ph2Zn or C6F5Cu in toluene furnishing the targeted bis(pentafluorophenyl)borane and diphenylborane species 2-Ar (Ar = Ph, C6F5) in 53 and 44% yield respectively. The products show a strong blue emission and undergo multi-step reversible reduction and oxidation processes. The effect of fluorination of the pendant aryl groups on the electronic structure is further examined by DFT methods.
authors: Department of Chemistry, Rutgers University-Newark, 73 Warren Street, Newark, NJ 07102, USA. fjaekle@rutgers.edu.
authors: Mayyadah
authors: M
authors: Yusuf
authors: Kanglei
authors: K
authors: Liu
authors: Fang
authors: F
authors: Guo
authors: Roger A
authors: RA
authors: Lalancette
authors: Frieder
authors: F
authors: Jäkle