Characterization of recognition sites for diethyl 4-nitrobenzylphosphonate, an organophosphate pesticide analogue

In a first step towards chemical sensors using molecular imprinted materials, the complexing characteristics of diethyl 4-nitrobenzylphosphonate, an organophosphate pesticide analogue, have been studied. Two molecules have been assessed as potential interacting moieties, specifically a fluoroalcohol and an aromatic acid. The interactions have been first characterized by regular methods, such as H-1, P-31 NMR and IR spectroscopy These showed a stoichiometry 1/1 for both complexes and association constants, respectively, close to 40 +/- 10 and 12 +/- 2 M-1. In a second step isothermal titration calorimetry was used and a method was developed to obtain low-association constants. The association constant could be obtained for the fluoroalcohol ligand and was found equal to 63 +/- 0.7 M-1. For the acidic molecule, an appropriate model could not be found, preventing the evaluation of this constant. (C) 2008 Elsevier B.V. All rights reserved.