PHOTOINDUCED ELECTRON TRANSFER FLUOROMETRIC HgII€ CHEMOSENSOR BASED ON A BODIPY ARMED WITH A TETRAPOD RECEPTOR

MUÑOZ DE LA PEÑA, A; MACHUCA A; BABIANO R; CULZONI; BRASCA R; GOICOECHEA

Congreso; Euroanalysios; 2013

From the great variety of BODIPY based-chemosensors able to determine Hg2+, only a small portion has been applied to its determination in environmental and/or biological samples. !e lack of studies on the analytical performance of the latter sensors makes interesting the development of investigations oriented to their possible analytical applications (1). In the present Communication, the synthesis of a BODIPY derivative armed with a tetrapod receptor is described. !e procedure is based on a previous publication (2), and the modi"cations performed to improve the synthesis include alternative procedures with di#erent objectives, as the consecution of a multigram synthesis, improving the low yields of some of the previously proposed procedure steps, simplifying the experimental steps, achieving the desired purity requirements for use with analytical purposes, and enriching the characterization of the implied structures. !e characteristics of its selectivity towards Hg2+ have been investigated, and the OFF-ON $uorometric response, based on a photo electron transfer (PET) mechanism, served as the base for the development of a method able to determine Hg2+ in environmental waters at ng mL?1 levels. !e intrinsic $uorescence of the BODIPY core is inhibited and the probe exhibits a weak $uorescence (i.e. ?OFF? state due to the deactivating PET e#ect). Upon complexation, Hg2+ interacts with the lone-pair electrons on the nitrogen atoms of the receptor moiety so that the electronic transfer from the receptor to the photo-excited $uorophore is slowed down or switched o# (i.e. ?ON? state due to the suppression of the deactivating PET e#ect by coordination of the analyte to the probe) (1). Regarding the complex photostability in aqueous solution, it is mandatory to conduct the experiments at darkness due to its photodegradation. !e stoichiometry studies indicated a 1:2 relationship for the BODIPY?Hg2+ complex. !e high selectivity towards mercuric ions is considerably in$uenced by pH, being necessary to conduct the experiments in a pH value higher than 6. Calibration samples were prepared by adding appropriate amounts of Hg2+ between 20.0?120.0 ng mL?1, at a constant BODIPY concentration of 1 μmol L?1. A&er agitating for 5 min at darkness, phosphate bu#er (pH=7.50) was added, and it was diluted to the mark with water. Fluorescence measurements were carried out at 18°C, exciting at 515 nm, and obtaining $uorescence emission at 538 nm. !e method has been satisfactory applied to Hg2+ determination in several environmental waters.