Molecular fluorescent pH-probes based on 8-hydroxyquinoline.
Three 5,7-pi-extended 8-benzyloxyquinolines, namely 5,7-diphenyl-, 5,7-bis(biphenyl-4-yl)- and 5,7-bis(4-dibenzothiophenyl)-8-benzyloxyquinoline were prepared and investigated as fluorescent pH-probes in nonaqueous solution. Absorption and photoluminescence spectra of the introduced compounds also including the starting material 8-benzyloxy-5,7-dibromoquinoline as well as their N-protonated counterparts were recorded and the results were rationalized by quantum-chemical calculations. A pronounced red shift of the emission occurred upon protonation of the non halogenated derivatives, while the dibromo-derivative is hardly emissive and is virtually not protonated under the conditions used. The diphenyl- and the bis(biphenyl)-derivative especially show promising photoluminescence quantum yields both in the parent and the protonated state making them candidates for the active component in pH sensing applications.
Kappaun
Stefan
S
Institute of Chemistry and Technology of Organic Materials (ICTOS), Graz University of Technology, Stremayrgasse 16, A-8010, Graz, Austria.
Sović
Tanja
T
Stelzer
Franz
F
Pogantsch
Alexander
A
Zojer
Egbert
E
Slugovc
Christian
C