hexadentate ("six-toothed")
ligand and
chelating agent,
Anyone who's got a good grasp of what's going on here, please feel free to elaborate.
Looks like a significant pathway to the formations of plant ligands, and interact with humates, fluvics to enhance flavor. regulating metals, ie. potassium, magnesium, iron, copper, zinc, sodium, molybdenum among others.
A means to store in soil/medium without creating toxicity.
Aminopolycarboxylic acid
The solubilisation of
Fe3+ ions at or below near neutral
pH can be accomplished using EDTA. This property is useful in
agriculture including hydroponics. However, given the pH dependence of ligand formation, EDTA is not helpful for improving iron solubility in above neutral soils.
[8] Otherwise, at near-neutral pH and above, iron(III) forms insoluble salts, which are less
bioavailable to susceptible plant species.
An
aminopolycarboxylic acid (sometimes abbreviated
APCA) is a
chemical compound containing one or more
nitrogen atoms connected through
carbon atoms to two or more
carboxyl groups. Aminopolycarboxylates that have
lost acidic protons form strong
complexes with
metal ions. This property makes aminopolycarboxylic acids useful complexone in a wide variety of chemical, medical, and environmental applications.
[1]
Structure
The parent of this family of ligands is the
amino acid glycine, H2NCH2COOH, in which the amino group, NH2, is separated from the carboxyl group, COO>H by a single methylene group, CH2. When the carboxyl group is deprotonated the glycinate ion can function as a bidentate
ligand, binding the metal centre through the nitrogen and one of two carboxylate oxygen atoms, to form
chelate complexes of metal ions.
[2]
Replacement of a hydrogen atom on the nitrogen of glycine by another acetate residue, –CH2COOH gives
iminodiacetic acid, IDA, which is a tridentate ligand. Further substitution gives
nitrilotriacetic acid, NTA, which is a tetradentate ligand.
[3] These compounds can be described as aminopolycarboxylates. Related ligands can be derived from other amino acids other than glycine, notably
aspartic acid.
a metal complex with the iminodiacetate anion
Higher dentacity is achieved by linking two or more glycinate or IDA units together.
EDTA contains two IDA units with the nitrogen atoms linked by two methylene groups and is hexadentate.
DTPA has two CH2CH2 bridges linking three nitrogen atoms and is octadentate. TTHA
[1] has ten potential donor atoms.
Applications
The
chelating properties of aminopolycarboxylates can be engineered by varying the groups linking the nitrogen atoms so as to increase selectivity for a particular metal ion. The number of carbon atoms between the nitrogen and carboxyl group can also be varied and substituents can be placed on these carbon atoms. Altogether this allows for a vast range of possibilities.
Fura-2 is noteworthy as it combines two functionalities: it has high selectivity for
calcium over
magnesium and it has a substituent which makes the complex
fluorescent when it binds calcium. This reagent provides a means of determining the calcium content in intra-cellular fluid. Details concerning applications of the following examples can be found in the individual articles and/or reference. The aminopolycarboxylate
nicotianamine is widespread in plants, where it is used to transport iron.