Syntheses, X‐ray crystal structures, and emission properties of diprotonated tetrapyridylpyrazine and triprotonated terpyridine. (23rd December 2015)

• Record Type: Journal Article
• Authors: Yoshikawa, Naokazu; Yamabe, Shinichi; Kanehisa, Nobuko; Inoue, Tsuyoshi; Takashima, Hiroshi
• Is Part Of: Journal of physical organic chemistry. Volume 29:Number 6(2016)
• Page Start: 269
• Page End: 275
• Publication Date: 2015-12-23
• Subjects: blue emission -- DFT calculation -- tetra‐2‐pyridylpyrazine -- triprotonated terpyridine; Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3527
• Languages: English
• ISSNs: 0894-3230

Abstract

Abstract: A series of metal‐free compounds, that is, planar diprotonated tetraH2 (PF6 )2 (1 ), planar monoprotonated bppzHPF6 (2 ), nonplanar diprotonated bppzH2 (PF6 )2 (3 ), and planar triprotonated terpyH3 Cl(PF6 )2 (4 ), were prepared and characterized by electrospray ionizationmass spectrometry, Ultraviolet–visible spectroscopy and cyclic voltammetry. Abbreviations used are tetra = tetra‐2‐pyridylpyrazine, bppz = 2, 3‐bis(2‐pyridyl)pyrazine, and terpy = 2, 2′:6′, 2″‐terpyridine. The X‐ray crystal structures of the four compounds1, 2, 3, and4 were determined. Both protonated pyridine rings are hydrogen bonded intramolecularly to the adjacent pyridine ring in compounds1 and3 . The π–π* absorption bands in the ultraviolet region for1, 2, 3, and4 in acetonitrile were red‐shifted relative to those of the corresponding neutral unprotonated compounds. All the cyclic voltammetry for the protonated species, 1, 2, 3, and4, showed the first reduction waves from −0.37 to −1.18 V, that were more positive than those of the neutral ones. Density functional theory was applied to interpret the planarity in1 . The attachment of two protons to the two terminal tetra nitrogens in1 leads to the remarkable emission ( Φ = 0.031). The attachment of three protons to the three terpy nitrogens in4 also gives the large quantum yield ( Φ = 0.48). Copyright © 2015 John Wiley & Sons, Ltd. Abstract : Planar diprotonated tetraH2 (PF6 )2 was prepared. The attachment of two protons to the two terminal tetra nitrogens leads to the remarkable emission ( Φ = 0.031). Density functional theory was applied to interpret the planarity.