| Abstract [eng] |
It is well known that heavy metals are able to complex with biological systems, especially those that include nitrogen, oxygen or sulfur atoms, and thus to change the structure of proteins or weaken the enzyme activity in human organism. Mercury is known as one of the most toxic heavy metals, which has neurotoxic, cancerogenic or mutagenic impact to live systems. As the mercury pollution is quite spread, there is a high demand to detect this harmful metal even in very small concentrations and the constant developments of selective and sensitive sensors are carried on. Recently, due to flexibility and possibility to easily tune properties, organic materials are being widely studied in order to apply them as chemosensors. In this work we present a series of electron accepting pyrimidine and pyrrole-pyrimidine based derivatives with strong electron donating dimethylamine group. The photophysical properties were studied in presence of different metal ions in the molecule and tetrahydrofuran systems. It was observed that upon complexation between dimethylamine group and mercury ions, the optical properties are dramatically change and can be tuned by varying the concentration of analyte. The main idea is that the presence of metal ions inhibits the twisting of the dimethylamine moiety, thus the intensity of the locally excited (LE) fluorescence band is enhanced up to 260 times, while the twisted intramolecular charge transfer (TICT) fluorescence band is quenched. Consequently, there is a clear possibility to create fluorescence sensors for detecting mercury both in tetrahydrofuran and in water. Besides, the selectivity for iron ions was also noticed, however, the rate of locally excited fluorescence intensity enhancement is significantly lower. In case of pyrrolo-pyrimidine derivative with two dimethylamine moieties connected by triple bonds, the presence of mercury or iron ions in the tetrahydrofuran solution led to dramatic changes in the absorption spectra with clear difference of the color seen by naked eye. These results indicate that stable metal complexes are already formed in the ground state. If metal ions are added to the molecular system together with water, it is possible to clearly extinguish mercury from iron as the dynamics of absorption spectra is not the same. All these results show the great potential to create sensitive and selective mercury ion chemosensors, having a great practical application in biological systems. |
