Colorimetric and Fluorescent Changes for Transition Metal ions and Nitroaromatic Compounds Based on a Nano-Spongy Continuous Structure of LB-PANI-Amide-Py System

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On account of their nano-scale size, large aspect ratio and high conductivity, conducting polymer have emerged as an attractive choice for conducting composite materials. As part of drive towards finding applications, an examination of the charge transfer (CT) between the conducting polymers and metal species is needed. Morrow et al. have reported on the metal properties of cyclen-based ligand containing Npropionamide donor groups since acetamide oxygen donor is much stronger donor than the alcoholic oxygen. Amide donor is also of tremendous interest because peptide oxygen donors bind K in K-ion channels. However, there is no work related with chemosensor properties by metal or electronic interactions for amide-fluorophore-introduced conducting polymer. Among the conducting polymer, polyaniline (PANI) is a unique conjugated polymer in that it can be tailored for specific applications through acid/base doping process. PANI nanostructures are of great current interest since they have a reactive-NH group in the polymer chain flanked on either side by phenylene rings. We have recently shown that PANIs can provide a very high chemical flexibility for the complexation of metal ions. Mechanisms of chemical interactions between PANI and transition metals are also intensively discussed by T. Hirao et al. and relate to the importance of metal ion sensing in biology, medicine, and the environment. Most colorimetric or luminescent chemosensors for transition metal ions are designed by employing intramolecular charge transfer (ICT) or photoinduced electron transfer (PET) mechanism. One significant advantages of nanoporous polyaniline conducting particles is that appropriate design combined with reactive binding sites in EB or LB could allow efficient control of colorimetric and conducting changes by metal complexation. In order to demonstrate the above proposal, two structurally similar EB (two imine and two NH groups for four aromatic rings) and LB (four NH groups for four aromatic rings) type PANIs were designed on the basis of the terms of coordination via the nitrogen lone pairs. Meanwhile, fluorescent pyrene (Py)-fuctionalized copolymers has been evaluated as a sensor for embedded between PANI leucoemeraldine base (LB) and Py, which could display colorimetric change in the presence of the metal nitroaromatic explosive materials (NAC) to give fluorescence quenching by π-π-stacked complexes. In addition, the interest in these materials has been driven by the ability of the conjugated polymers to create large signal amplification relative to small molecule chemosensors due to the delocalization and rapid diffusion of excitons throughout the individual polymer chains, so-called molecular wire effect or one point contact and multipoint response effect, in solution. This encouraged us to develop multi-chemosensor based on amide bond ions as well as fluorescent quenching by electron poor NAC species.