Luminescent organoboron ladder compounds via directed electrophilic aromatic C–H borylation. Issue 11 (5th February 2016)

• Record Type: Journal Article
• Authors: Yusuf, Mayyadah; Liu, Kanglei; Guo, Fang; Lalancette, Roger A.; Jäkle, Frieder
• Is Part Of: Dalton transactions. Volume 45:Issue 11(2016)
• Page Start: 4580
• Page End: 4587
• Publication Date: 2016-02-05
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt05077d
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Regioselective electrophilic borylation of a pyridyl-flanked fluorene provides highly luminescent, air-stable boron-bridged ladder species. 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. Compound1 is then subjected to electrophilic borylation with BBr3 in the presence of iPr2 NEt as a bulky base to give the tetra-coordinate ladder-type organoboron species2-Br . Arylation of2-Br is accomplished by addition of Ph2 Zn or C6 F5 Cu in toluene furnishing the targeted bis(pentafluorophenyl)borane and diphenylborane species2-Ar (Ar = Ph, C6 F5 ) 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.