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Syntheses, X‐ray crystal structures, and emission properties of diprotonated tetrapyridylpyrazine and triprotonated terpyridine
Author(s) -
Yoshikawa Naokazu,
Yamabe Shinichi,
Kanehisa Nobuko,
Inoue Tsuyoshi,
Takashima Hiroshi
Publication year - 2016
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3527
Subject(s) - chemistry , terpyridine , protonation , pyridine , cyclic voltammetry , acetonitrile , crystallography , pyrazine , crystal structure , deprotonation , quantum yield , electrospray ionization , photochemistry , stereochemistry , mass spectrometry , metal , medicinal chemistry , ion , fluorescence , electrochemistry , organic chemistry , electrode , physics , quantum mechanics , chromatography
A series of metal‐free compounds, that is, planar diprotonated tetraH 2 (PF 6 ) 2 ( 1 ), planar monoprotonated bppzHPF 6 ( 2 ), nonplanar diprotonated bppzH 2 (PF 6 ) 2 ( 3 ), and planar triprotonated terpyH 3 Cl(PF 6 ) 2 ( 4 ), were prepared and characterized by electrospray ionization mass 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 compounds 1 , 2 , 3 , and 4 were determined. Both protonated pyridine rings are hydrogen bonded intramolecularly to the adjacent pyridine ring in compounds 1 and 3 . The π–π* absorption bands in the ultraviolet region for 1 , 2 , 3 , and 4 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 , and 4 , 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 in 1 . The attachment of two protons to the two terminal tetra nitrogens in 1 leads to the remarkable emission ( Φ = 0.031). The attachment of three protons to the three terpy nitrogens in 4 also gives the large quantum yield ( Φ = 0.48). Copyright © 2015 John Wiley & Sons, Ltd.