Related Experiment Video
Updated: Jan 13, 2026
Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
Chemical Speciation and Coordination Behavior of 8‑Hydroxyquinoline-2-carboxylic Acid with Divalent Cations in
Anna Baryłka1, Rafał Bukrym2, Izabela Ryza1
1Doctoral School, University of Bialystok, K. Ciolkowskiego 1K, 15-245 Bialystok, Poland.
Abstract:
In this work, the coordination properties of 8-hydroxyquinoline-2-carboxylic acid (8-HQA, LH2) toward Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ are discussed. Stability constants for Mn2+, Co2+, and Ni2+/8-HQA systems were determined by ISE-H+ (glass electrode) potentiometry, and those of Cu2+ and Zn2+/8-HQA by ultraviolet-visible (UV-vis) spectrophotometry, in KCl(aq) at I = 0.2 mol dm-3 and T = 298.2 K. For all systems, three species are formed: MLH+, ML, and ML2 2-. 8-HQA proved a good sequestering agent of M2+ over a wide pH range, as also shown by the calculated pL0.5 values. The stability of the formed metal complexes follows the expected Irving-Williams trend, especially concerning the ML2 2- species, with log β120: 12.45 ± 0.01 (Mn2+) < 13.45 (Fe2+) < 15.90 ± 0.04 (Co2+) < 17.17 ± 0.05 (Ni2+) < 20.64 ± 0.03 (Cu2+) > 18.78 ± 0.02 (Zn2+). This trend is inversely correlated to the M-N bond length determined by quantum mechanical calculations. These studies, together with voltammetry and electron paramagnetic resonance spectroscopy, allowed us to derive information about the coordination modes, structure, and nature of the formed species. Results support the formation of ML2 2- complexes over possible ML-(OH)-, with 8-HQA acting as tridentate in all formed species, including the protonated MLH+.
More Related Videos
11:04Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides
Published on: September 7, 2019
05:59Author Spotlight: Advancing Antimicrobial Resistance Research with Innovative Approaches and Synthetic Compounds
Published on: September 27, 2024
Related Concept Videos
03:45Formation of Complex Ions
02:42Valence Bond Theory
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
00:56Extraction: Advanced Methods
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:54Coordination Compounds and Nomenclature