TY  - JOUR
A1  - Haubitz, Toni
A1  - Fudickar, Werner
A1  - Linker, Torsten
A1  - Kumke, Michael Uwe
T1  - pH-sensitive fluorescence switching of pyridylanthracenes
BT  - the effect of the isomeric pattern
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - 9,10-substituted anthracenes are known for their useful optical properties like fluorescence, which makes them frequently used probes in sensing applications. In this article, we investigate the fundamental photophysical properties of three pyridyl-substituted variants. The nitrogen atoms in the pyridinium six-membered rings are located in the ortho-, meta-, and para-positions in relation to the anthracene core. Absorption, fluorescence, and transient absorption measurements were carried out and were complemented by theoretical calculations. We monitored the photophysics of the anthracene derivatives in chloroform and water investigating the protonated as well as their nonprotonated forms. We found that the optical properties of the nonprotonated forms are strongly determined by the anthracene chromophore, with only small differences to other 9,10-substituted anthracenes, for example diphenyl anthracene. In contrast, protonation leads to a strong decrease in fluorescence intensity and lifetime. Transient absorption measurements and theoretical calculations revealed the formation of a charge-transfer state in the protonated chromophores, where electron density is shifted from the anthracene moiety toward the protonated pyridyl substituents. While the para- and ortho-derivatives' charge transfer is still moderately fluorescent, the meta-derivative is affected much stronger and shows nearly no fluorescence. This nitrogen-atom-position-dependent sensitivity to hydronium activity makes a combination of these fluorophores very attractive for pH-sensing applications covering a broadened pH range.
KW  - Absorption
KW  - Aromatic compounds
KW  - Fluorescence
KW  - Hydrocarbons
KW  - Reaction mechanisms
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpca.0c09911
SN  - 1089-5639
SN  - 1520-5215
VL  - 124
IS  - 52
SP  - 11017
EP  - 11024
PB  - American Chemical Society
CY  - Washington
ER  -