Synthesis of chromo fluorogenic sensors for molecular recognition

Abstract

This work aims to explore the possibility of design, synthesize and test capabilities, firstly in solution and then into the solid state later on in the form of monolayer new molecules, that present the ability to recognize a substrate and to transform this recognition event into a detectable signal or into a real reaction. What we expect is a change of the optical properties of these compounds, for instance expressed by a colour switching or a fluorescence alteration both in solution and on the solid state. During the first two year we synthesized a series of molecule in order to recognize nerve agent simulant like DMMP (dimethylmethyphosphonate) by using firstly simple molecules as oximes that is well known are used in the detoxification therapy after nerve agents exposure. Unfortunately the change of the behaviour of these molecule was not as we expected into the solid state because the detectable signal (that was expected to be a weak interaction) was too low in order to think to transform this monolayer into a device, so we decided to move our research into another class of compounds at last to achieve a higher detectable signal by using aza-compounds with the same oxime moiety, but in this case we used as recognition event a reaction by using another nerve agent simulant DCP (diethylchlorophosphate). The solution measurements are promising and we are going to perform the same test on solid state. Another aim of our research was to selectively recognize biological important metal transition ions as copper both in solution and into solid state by colorimetric or fluorescent essay; for this purpose we employed organic scaffolds that show a change of one of the properties mentioned above, for instance aromatic rings that bear chromophoric groups or napthyl amide derivates, covalently bonded with functional groups, such as di-picolyl amine, that as it is well known have not only a great change in their photochemical behaviour but also they present great selectivity. We synthesized a novel N-tyramine-di[2(dipicolyl)amino]1,8 naphtalimide that showed the ability to selectively recognise Cu2+ as we expected, and then we try to synthesized another derivate of this compound that bear in order three and four picolyl groups but we stopped our synthesis at the three armed derivate (that showed a good sensibility but not a great sensitivity); the four armed was too difficult to obtain (very low yields and difficulties in purification). During the third year we focused our attention into the recognition of transition metal ions, specifically copper, in biological environment that is very important for in vivo and in vitro studies for many associated diseases related to the change of their homeostasis. Firstly we focused our attention on a bodipy derivate presented in literature, we embody this molecule into silica-doped-nanoparticles in collaboration with other research groups obtaining very promising results in the recognition of copper. Secondly we synthesized a derivate of di[2(dipicolyl)amino]1,8 naphtalimide linked with a disaccharide (threalose, that shown to be very effective in inhibiting aggregation of the Alzheimer s related beta-amyloid peptide alpha-betha and in reducing its cytotoxicity) in order to obtain a water soluble chemosensor; also this work is in partnership with another research group and the first results are promising. We also studied the possibilities of selectively transfer oxygen onto a specific substrate for instance unfunctionalized alkenes by using salen-Mn(III) complexes as catalysts, both in solution and on solid support, in order to obtain a reusable device.