Remarkable Sensing Behavior of Pyrazole-based Chemosensor Towards Cu(II) Ion Detection: Synthesis, Characterization and Theoretical Investigations

We report the synthesis of a new imine based ligand, 3-((3-methoxybenzylidene)amino)-1H-pyrazol-5-ol (<b>HL</b>) and its Cu(II) complexes in 2:1 (<b>HL</b>:metal) and 1:1:1 (<b>HL</b>:metal:<b>HQ</b>) stoichiometric ratio using 8-hyroxyquinoline (<b>HQ</b>) as an additional bidentate ligand. The synthesized ligand (<b>HL</b>) and its Cu(II) complexes (<b>1</b> and <b>2</b>) are structurally characterized using FT-IR, electronic absorption and emission, NMR, MS and TGA techniques. Furthermore, the complexation of Cu²⁺ with <b>HL</b> leads to the immediate formation of brown colored solution which indicates that <b>HL</b> can act as simple colorimetric sensor for Cu²⁺ions. We further investigated that the sensor could selectively bind to the Cu²⁺ions even in the presence of competitive ions such as Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺ and Na⁺ions in aqueous solutions which was studied by electronic absorption spectroscopy. The <b>HL</b> ligand and corresponding Cu(II) complexes have been investigated for their reactive properties by density functional theory (DFT) calculations. Quantum molecular descriptors describing local reactive properties have been calculated in order to identify the most reactive molecule sites of title compounds. DFT calculations encompassed <a></a><a></a><a>molecular electrostatic potential (MEP), local average ionization energies (ALIE), Fukui functions and bond dissociation energies for hydrogen abstraction (H-BDE)</a>

Pyridoxylidene aminoguanidine and its copper(II) complexes – Syntheses, structure, and DFT calculations

<p>Two nitrate salts of the well-known, and due to its significant biological activity very important, compound pyridoxylidene aminoguanidine (PLAG) were obtained in the form of single crystals. Thus this ligand is structurally characterized for the first time. In addition, the first data on the structure of a Schiff base of aminoguanidine with the active form of vitamin B₆, i.e. pyridoxal-phosphate, of the formula PLPAG·HCl·2H₂O, are presented. Two new square-pyramidal Cu(II) complexes of PLAG were synthesized and their physicochemical and structural properties analyzed. In these complexes, PLAG is coordinated as a zwitter-ion, in a tridentate <i>ONN</i> manner, via the oxygen atom of the deprotonated phenolic OH-group and nitrogen atoms of the azomethine and imino group of the aminoguanidine moiety. For the first time it was possible to make a comparative analysis of the structural properties of ligand salts and the coordinated ligand, so the effects of coordination could be unequivocally pointed out. Common fragments encountered in ligand structures were compared by half-normal probability plots. Density functional theory calculations have been conducted in order to gain insight into reactive properties of the investigated molecules. Molecular electrostatic potential, average local ionization energy surfaces, and Fukui functions have been calculated in order to obtain further information on the reactive properties.</p