Experimental insights on the coordination modes of coumarin-3-carboxilic acid towards Cr(III)-, Co(II)-, Ni(II)-, Cu(II)- and Zn(II): A detailed potentiometric and spectroscopic investigation in aqueous media

Here complexation of coumarin-3-carboxilic acid (HCCA) with Cr(III), Co(II), Ni(II), Cu(II) and Zn(II) at 37 degrees C and in 0.16 M NaClO4 is discussed. Speciation profiles obtained by potentiometric titrations show that in aqueous solution a complexation occurs at a ligand-to-Cr(III), -Ni(II) and -Cu(II) ratio of 1:1, and at a ligand-to-Co(II) and -Zn(II) ratio of 1:1, 2:1 and 3:1. For Co(II)-HCCA system also a polynuclear species is formed (i.e., Co-2(OH)(CCA)(2)(+)). The coordination sites of HCCA to the different metal ions were determined with the aid of UV-Vis, IR and X-ray diffraction. Solid state chemistry of HCCA was enriched of two new X-ray resolved structures for cobalt and nickel metal cations, which are also reported and discussed. From crystal packing analysis results the intricate motif of weak interactions that leads to a supramolecular interesting arrangement, not yet disclosed and argued in the previous literature about coumarin-3-carboxilic acid isostructural coordination compounds. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study discusses the complexation of HCCA (coumarin-3-carboxilic acid) with Cr(III), Co(II), Ni(II), Cu(II), and Zn(II) in 0.16 M NaClO4 at 37 degrees C. Potentiometric titrations reveal that complexation occurs in aqueous solution with a ligand-to-metal ion ratio of 1:1 for Cr(III), Ni(II), and Cu(II), and a ratio of 1:1, 2:1, and 3:1 for Co(II) and Zn(II). The coordination sites of HCCA with different metal ions were determined using UV-Vis, IR, and X-ray diffraction. Additionally, new crystal structures for cobalt and nickel metal cations in the HCCA system were reported and discussed. Crystal packing analysis demonstrates the presence of intricate weak interactions that contribute to a novel supramolecular arrangement not previously observed or discussed in the literature on isostructural coordination compounds of coumarin-3-carboxilic acid.