posted on 2005-01-12, 00:00authored byAna B. Descalzo, Knut Rurack, Hardy Weisshoff, Ramón Martínez-Máñez, M. Dolores Marcos, Pedro Amorós, Katrin Hoffmann, Juan Soto
A strategy for the rational design of a new optical sensor material for the selective recognition
of long-chain carboxylates in water is presented. The approach relies on the combination of structure−property relationships to single out the optimal molecular sensor unit and the tuning of the sensing
characteristics of an inorganic support material. A spacer-substituted 7-urea-phenoxazin-3-one was
employed as the signaling moiety and a mesoporous trimethylsilylated UVM-7 (MCM-41 type) material
served as the solid support. The sensor material shows the advantageous features of both modules that
is absorption and emission in the visible spectral range, a fluorescence red-shift and enhancement upon
analyte coordination, and the amplification of noncovalent (binding) and hydrogen-bonding (recognition)
interactions in the detection event. Besides these basic results that are related to the design and performance
of the sensor material, the paper discusses general aspects of amido-substituted phenoxazinone
photophysics and addresses some general features of molecular anion recognition chemistry in aqueous
vs nonaqueous media, utilizing steady-state and time-resolved optical as well as NMR spectroscopies.
Detailed studies on potentially competing biochemical species and a first access to the schematic model
of the response of the sensor material as obtained by a combination of fluorescence lifetime distribution
analysis and Langmuir-type fitting of the gross binding constants complement the key issues of the paper.