Syntheses and pH-responsive emissions of pyrid-2-yl-appended para-phenylene oligomers. Issue 49 (4th December 2020)

• Record Type: Journal Article
• Authors: He, Yan-Qin; Tang, Jian-Hong; Li, Zhong-Qiu; Zhong, Yu-Wu
• Is Part Of: Tetrahedron. Volume 76:Issue 49(2020)
• Publication Date: 2020-12-04
• Subjects: Luminescence -- pH sensitive materials -- Oligophenylene -- Pyridinium dyes -- C–H functionalization; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2020.131695
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: The synthesis of π-conjugated organic materials through C–H activation and functionalization has recently received increasing attention. In this work, four pyrid-2-yl-appended para -phenylene oligomers (1 –4 ) with two to five phenyl repeating units were synthesized via the Ru-catalyzed C–H activation of 2-phenylpyridine, followed by oxidative homocoupling or the arylation with a para -phenylene dibromide substrate. The single-crystal X-ray data and crystal packing of 1 and 3 are presented. In response to acid stimuli, the blue emissions of 1 –3 are replaced by red-shifted cyan emissions, which are associated with the charge transfer transition from the phenylene backbone to the protonated pyridinium units. However, the emission of the longest congener 4 is largely quenched upon protonation. This length-dependent emission property is rationalized by DFT and TDDFT calculations. Graphical abstract: Image 1