Synthesis, characterization and DFT studies of water stable Cd(II) metal-organic clusters with better adsorption property towards the organic pollutant in waste water

In this report, two water stable Cd(II) metal-organic clusters using slow evaporation method are designed and synthesized in order to explore for functional applications. The complexes are formulated as [Cd-2(pda)(2)(H2O)(6)]center dot(H(2)pda)(2) (1) and [Cd-4(Hpda)(4)(mu(2)-OH)(2)(Cl)(2)(H2O)(6)]center dot 2H(2)O (2) where H(2)pda = 2,6-pyridine dicarboxylic acid. The synthesized complexes show unusual hepta-coordinated geometry around the central metal ion. 1 is di nuclear while 2 is a tetranuclear discrete complex. The tetranuclear complex is the very first example of cadmium with H(2)pda ligand. The two complexes were characterized by various spectroscopic studies and with the help of single crystal technique the, structures of 1 and 2 was elucidated. Various non covalent interactions such as pi-pi and C-H center dot center dot center dot pi consolidate the network against water solubility. The metal-organic clusters exhibit various non-covalent interactions which were further verified by Hirshfeld surface analysis. The DFT calculations were also performed on both the complex which corroborate the electronic and spectral aspects of complexes. The stability of 1 and 2 was checked using the PXRD pattern of 1 and 2 after 10 hrs in water and it shows the identical pattern even after the 24 hrs. Further, the metal-organic clusters were checked for their adsorption property towards the cationic dye such as Rhodamine B. Out of the two complexes, only 2 shows better adsorption property due to its better stability in water. The mechanism of dye adsorption is also explored.