Protonation behaviour of 2-phenyl-1, 3-diazaazulene derivatives. Issue 7 (15th February 2018)

• Record Type: Journal Article
• Authors: Sun, Peili; Rao, Danling; Zhang, Pu; Qin, Yujun; Guo, Zhi-Xin
• Is Part Of: Tetrahedron. Volume 74:Issue 7(2018)
• Page Start: 731
• Page End: 739
• Publication Date: 2018-02-15
• Subjects: 1, 3-diazaazulene derivatives -- Protonation -- Response mechanism -- π-conjugation; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2017.12.051
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: Three 2-phenyl-1, 3-diazaazulene derivatives were synthesized and their protonation behaviours were investigated systematically via UV–vis absorption titration and 1 H NMR titration, as well as theoretical calculations. One of them exhibited a monoprotonation process while the others displayed prominent halochromic diprotonation responses. Interestingly, upon protonation of 2-phenyl-1, 3-diazaazulene derivatives, the coplanarity and conjugation of the 16-π-conjugated backbones were well kept, while the electronic structures were controllably adjusted. The response mechanism of 1, 3-diazaazulene derivatives towards acid is through the attachment of acid proton to the nitrogen atom in the diazaazulene ring, resulting in the change of the hybridization of protonated-N from sp 2 to sp 3, which differed from that of the well-known azulene (analogue of 1, 3-diazaazulene, protonation at carbon atom). This work would provide a new insight into the protonation research of the organic functional molecules. Graphical abstract: