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Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
Like Alk and H+-Acy, the quantities OH–-Alk and Acy have units of eq/L. OH–-Alk gives the total eq/L of all bases in the solution that are at least as basic as OH–. Acy gives the total eq/L of all protons in the solution that are at least as acidic as HCO3−. In water, in fact, there cannot be bases stronger than OH–because if a base stronger than OH– were placed in water, call it Z–, then Z– would react essentially stoichiometrically with water to yield OH–. The reaction would be Z– + H2O = HZ + OH–. This is the base version of the “acid/base leveling effect” of water. (For the acid version of that effect, there is no acid in water stronger than water-solvated H+ because if an acid stronger than water-solvated H+ were placed in water, it would virtually completely give up its protons to water to form water-solvated H+; that is what happens when molecular HCl dissolves in water.)
Co(II), Ni(II), and Cu(II) metal complexes based on thiourea ligand: synthesis, characterization, thermal behaviors, anticancer, and antioxidant activities
Published in Inorganic and Nano-Metal Chemistry, 2023
Tuncay Yeşilkaynak, Ruken Esra Demirdöğen, Harun Muslu, Fatih Mehmet Emen
The selected IR bands are presented in Table 1. The broad stretching vibration of N–H is observed at 3163 cm−1. The intense stretching band of C = O group was observed at 1682 cm−1. The stretching vibration observed at 1162 cm−1can be due to the C = S group in HL. It is also expected that upon complexation this vibration band would also shift to a lower wavelength. However, it can hardly be observed as it overlaps with other bands in that region. Due to deprotonation of HL upon complexing with the metal atoms the stretching vibration band of N–H in the complexes could not be observed. Despite being present, the N–H band cannot be observed and the C = O and C = S vibration bands shift. In the thiourea derivative there is only one dissociable proton and it comes from the –NH in the ligand. The ligand is reacted with the metal in non-aqueous media due to the leveling effect of the solvent the H is removed from the –NH in the ligand. Thus, there will be no enol or keto form left behind and hence complexation of the metal with the ligand cannot be said to proceed over enol or keto forms. The leaving –H will cause the structure to attain a delocalization of the double bond on C = O and C = S. Hence the ligand will chelate with the metal. This also verified with the IR spectra. While in the FT-IR spectra of the complexes the –NH stretching vibrations are not observed the C = O and C = S bonds are observed to shift to lower wavenumber. This indicates that the double bond in the C = O has opened due to delocalization and yield a 1.5 bond character. These findings confirm formation of complexes and are in accordance with previous reports.[40–47]