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Copper(II) and Iron(III) Complexation by the Carboxylate Group of Humic Acid
Author(s) -
Boyd Stephen A.,
Sommers Lee E.,
Nelson Darrell W.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500060048x
Subject(s) - carboxylate , chemistry , denticity , copper , metal , humic acid , infrared spectroscopy , carboxylic acid , inorganic chemistry , infrared , crystallography , stereochemistry , polymer chemistry , organic chemistry , fertilizer , physics , optics
Infrared (IR) spectroscopy, between 2,000 and 1,000 cm −1 , was used to identify the mode by which carboxylates of a soil humic acid (HA) complexed Cu 2+ and Fe 3+ . Carboxylic acid groups of HA (R‐COOH) were converted to carboxylates (R‐COO ‐ ) by forming coordinate bonds with Cu 2+ and Fe 3+ . The separation Δ of the antisymmetrical and symmetrical stretching vibrations of R‐COO ‐ was obtained from the IR spectra of the metal‐HA complexes. The Δ values for the metal‐HA complexes were significantly larger than the corresponding reference value of Δ for uncomplexed ‐COO ‐ , demonstrating that R‐COO ‐ formed a unidentate complex (i.e., a single M‐O bond) with Cu 2+ and Fe 3+ . The formation of bidentate or bridging complexes between R‐COO ‐ of HA and Cu 2+ or Fe 3+ was not observed.