Remarkable emissions in diprotonated 2,2′:6′,2″‐terpyridine derivatives

Abstract

A series of new metal‐free blue emission compounds, i.e., diprotonated terpyH2ClPF6 (1), tterpyH2ClPF6 (2), ClterpyH2ClPF6 (3), and BterpyH2(PF6)2 (4), were prepared and characterized by electrospray ionization mass spectrometry, UV–vis spectroscopy, and cyclic voltammetry (CV). Abbreviations used are terpy = 2,2′:6′,2″‐terpyridine, tterpy = 4′‐(4‐tolyl)‐2,2′:6′,2″‐terpyridine, Clterpy = 4′‐chloro‐2,2′:6′,2″‐terpyridine, and Bterpy = 4,4′,4″‐tert‐butyl‐2,2′:6′,2″‐terpyridine. The X‐ray crystal structures of the three new compounds 1, 2, and 4 were determined. Both protonated pyridine rings of the terpyridine derivatives are hydrogen bonded intermolecularly to the adjacent Cl− ion in compounds 1, 2, and 3. The π–π* absorption bands in the UV region for 1, 2, 3, and 4 in acetonitrile were red‐shifted relative to those of the corresponding neutral compounds. All the compounds exhibited stronger emissions (around 400 nm) than their neutral counterparts. All the CVs for the diprotonated species, terpyH 22+, tterpyH 22+, ClterpyH 22+, and BterpyH 22+, showed the first reduction waves around −0.6 V, which were more positive than those of the neutral ones. Density functional theory was applied to interpret the remarkable differences in the interaction of the Cl− ion. The attachment of two protons to the two terminal Bterpy nitrogens in 4 elicits remarkable characteristics. Both positive charges on the nitrogens are delocalized over the conjugated pyridine systems and the tertiary carbonium ions are stabilized to lead to stronger emission (Φ = 0.35) than the corresponding neutral Bterpy (Φ = 0.045). CCDC 732045–732047 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif Copyright © 2010 John Wiley & Sons, Ltd.

Three‐in‐One Crystal: The Coordination Diversity of Zinc Polypyridine Complexes

“…The fluorescence of the ddpd ligand shifts to higher energy through protonation in CH 3 CN, whereas the protonation of tpy leads to a redshifted emission from λ = 340 to 412 nm (and to 395 nm upon further protonation) in this solvent . This opposite behavior can probably be attributed to the different protonation sites.…”

“…This opposite behavior can probably be attributed to the different protonation sites. Although tpy can only be protonated at the pyridine rings, which increases their acceptor strengths,[13c] the NR 3 moieties of ddpd should be more basic than the pyridine rings. For example, the p K a value of pyridinium ions [p K a (Hpy + ) = 5.3] is much lower than that of protonated 4‐dimethylaminopyridine [HDMAP + , p K a (HDMAP + ) = 9.6] .…”

Manipulating connecting nodes through remote alkoxy chain variation in coordination networks with 4′-alkoxy-4,2′:6′,4′′-terpyridine linkers

“…31 Diprotonation results in a further increase in QY. 31 Diprotonation results in a further increase in QY.…”

Anion Influence of Emission Properties and DFT Calculations of Diprotonated and Triprotonated Terpyridines

“…The blue fluorescent 4′‐(4‐methylphenyl)‐terpy is known as an electron transport and electroluminescent material to design emitting diode (OLED) applications . Recently, it has been reported that monoprotonated terpyridine cation ([terpyH] + ) indicates stronger emission in acetonitrile than that of the parent neutral species (terpy) . Preparation and investigation of the diprotonated terpyridine cation ([terpyH 2 ] 2+ ) has also been reported …”

“…[12,13] Preparation and investigation of the diprotonated terpyridine cation ([terpyH 2 ] 2 + ) has also been reported. [14][15][16][17][18][19][20] In this work, we report new intense emission compounds that possess hydrogen bond between [terpyH 2 ] 2 + and PF 6 À in the compounds. Eleven compounds and their structures were examined using DFT calculation: [(terpyH 3 )F](PF 6 ) 2 (1F), [(ter-pyH 3 )Cl](PF 6 (Figure 1).…”