Synthesis, structural analysis and design of coordination polymers of zinc(II) and cadmium(II) with photoluminiscente properties

The study of coordination polymers (CPs) is at the forefront of modern inorganic chemistry due to their remarkable properties, such as high porosity, thermal and chemical stability, as well as specific behaviors, such as photoluminescence, electrical conductivity and selective adsorption capacity. Through an adequate selection of their building blocks, CPs can be designed to enhance a particular property.
The nature of metal ions and coordination agents used in the process of obtaining CPs is an important factor. CPs of metals such as zinc and cadmium are intensively studied, due to the fact that they are distinguished by their nuclearity and diverse coordination polyhedra, which depending on the variation of steric, electronic, packing factors, etc., can exhibit luminescent activity.
Owning to their diverse activities, nitrogen heterocyclic compounds have always been attractive targets to develop new coordination compounds. The 2,6-diacetylpyridine (dap) is a suitable dialdehyde for preparation of dihydrazone Schiff bases with multiple coordination sites, giving rise to metal complex compounds with exclusive geometries. The opportunities for generating of new molecular architectures can be possible by condensation of dap with izoniazid and by suitable substitution of their pyridine rings in order to provide additional donor atoms.
he CPs based on these ligands may present interesting photoluminescence (PL) properties due to its aromatic nature and the presence of carbonylic and azometinic groups. When in the crystal structure of a CP this ligand is coordinated to metals of Zn(II) or Cd(II), the PL tends to be enhanced by means of the well-known crystal-induced luminescence effect. These ions can promote charge transfer from ligand-to-metal and, therefore the photoluminescence emission can be modulated depending on the ligand emissions. Regardless of the luminescence mechanism, that occurs in such systems, these compounds represent the  interest for applications as luminescence-based molecular detectors for ionic species, toxic molecules, environmental pollutants, LEDs, fluorescent tubes and thermometers etc. In the framework of this project, taking into account the aforementioned, the reaction conditions will be established and new CPs of Zn(II) and Cd(II) will be obtained based on isoniazid and dap. The influence of the nature of the metal ion, the coordinating agent and the solvent on formation of CPs will be studied. 
New CPs will be synthesized and characterized by elemental analysis, IR, UV-Vis and NMR spectroscopy, X-ray single crystal and powder diffraction analyze.
The photoluminescence properties of these complexes will be also studied, using the fluorescence spectroscopy. Their emission characteristics will be evaluated from the theoretical and experimental points of view, involving the measurements in the solid and liquid states.
The theoretical calculations will be performed to study the optical properties of Zn(II) and Cd(II) coordination polymers to analyze the nature of luminescence in CPs , which may lead to rational design and synthesis of desired CPs.
The influence of ligand and nature of the metal ion on the photoluminescent properties of coordinative polymers will be evaluated. A comprehensive study of relation ”structure-photoluminescent properties” will be carried out depending on the nuclearity of the compounds, condition of synthesis, nature of metal, coordination agent and solvent.