Iridium(III)-3-hydroxy-2-(3′-methyl-2′-thienyl)-4-oxo-4H-1-benzopyran complex: The analytical, in-vitro antibacterial and DFT studies

Abstract

The trace determination of iridium(III) has been established using an aqueous phase spectrophotometric approach based upon its tendency to form a complex with the colour generating reagent, 3-hydroxy-2-(3-́methyl-2́-thienyl)-4-oxo-4H-1-benzopyran (HMTB) at pH 4.71–5.11. From 0.005 to 0.05 mol L -1 H3PO4 medium, 1:2 (M:L) light yellow complex between Ir(III) and HMTB has been formed with maximal colour intensity in the wavelength range of 417–425 nm. To optimize the conditions, the effect of several physical parameters such as medium choice and concentration, pH and ligand concentration on the micro level determination of iridium (III) had been examined in depth so as to make the proposed method simple, selective, sensitive and reproducible. Under the ideal set of conditions, the absorbance is linearly proportional to the concentration of Ir(III) in the range 0–1.5 µg mL−1, the correlation coefficient being 0.9954. The molar annihilation coefficient has been evaluated to be 8.458 × 104 L mol−1 cm−1 whereas Sandell’s sensitivity is 0.0023 µg Ir(III) cm−2. The detection limit of the method under the optimal set of conditions is 0.0281 µg mL−1 and relative standard deviation being 0.0296%. The proposed method satisfactorily permits determination of Ir(III) in a variety of synthetic mixtures without any interference. The novelty and advantage of the proposed method is in its high sensitivity in aqueous phase conditions compared to most of the previously cited methods. The molecular structure of the ligand (HMTB) and its complex with Iridium has been investigated using density functional theory calculations at the DFT level of theory. Ionization potential (IP) and Eletron Affinities (EA), Hardness (η), Softness (S), Electronegativity (μ), Electrophilic Index (ω), Electron Donating Power (ω-), Electron Accepting Power (ω+) and Energy Gap (Eg) are some of the molecular characteristics of the title compound that have been calculated. The Ir(III)-HMTB complex is finally tested for its in- vitro antibacterial activity and is found to show significant antibacterial application allowing its use as an antibacterial agent.