Executive Summary : | Nowadays, various functionalities of dynamic metal organic frameworks (MOFs) and their structural-property relations are in the prime focus of MOF related research. Among many interesting properties of such flexible MOFs, photoluminescence has also been studied to some extent, either in terms of ligand based emission or for excited state intra molecular proton transfer (ESIPT). The ESIPT phenomenon is occur due to the transfer of the proton within the molecule and in case of MOFs this is very much dependent on the structural topology, supramolecular organization and possibility of temperature and/or solvent dependent reorganization of structure. Now if an ESIPT core present in an organic ligand be introduced in a MOF with proper blending of flexibility during its design, it can be suitable to create some unique features in the ESIPT behavior of the MOF. The ESIPT behavior of the organic building block in MOFs can be put on hold by suitable synthetic adoption and fine tuning of the flexibility of MOFs. Again if this flexibility imposed hold ESIPT behavior, can be reinitiated by the use of some polar solvent and/or gas; which can carry the proton for the required tautomerism for ESIPT. Thus, these classes of molecules where the ESIPT is solvent driven, can be useful to detect the traces of such solvents. The sensing ability can be extended to some gas molecules as well by tailoring such flexibility in such a way and by proper tuning of the ESIPT chromophore in the MOF. Therefore, the principal objective of the proposal is to design and synthesis of several flexible metal organic frameworks with ESIPT core and their structural and spectroscopic elucidation in order to achieve suitable MOF based material for solvent/gas sensing application. The methodology involved with the proposal in mainly synthesis oriented, considering the rational understanding whether it is the design of the ligand with ESIPT core or their corresponding MOFs. The X-ray diffraction analysis for structural elucidation and the detailed photoluminescence study in various conditions to understand the ESIPT behavior, are the most important aspects of the methodology adopted. As the ESIPT behavior shows excellent dual emission, the system could be very much suitable for doing sensing application. The extent of flexibility in the MOF can be tuned and tailored to have the calculated restriction of the ESIPT behavior of the building block and the extent of such release to reinitiate the ESIPT, can be done with the extent of polarity of the solvent/gas. Therefore, the systematic study for the design of such ESIPT driven flexible MOFs can create a library of polarity based sensor that are stable and reusable. The successful implementation of the project will not only give a specific guideline for the design of MOFs, suitable for ESIPT based sensing of; but also enlighten the area of design of functional flexible MOFs having specific spectroscopic properties. |