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oai:mountainscholar.org:10217/2383272025-12-30T03:37:28Zcom_10217_100532com_10217_100000com_10217_100367com_10217_100303col_10217_100536col_10217_100368

Schauer, Cynthia Karen, author Anderson, Oren, advisor Elliott, C. Michael, committee member 2024-05-13T21:28:40Z 2024-05-13T21:28:40Z 1985 https://hdl.handle.net/10217/238327 https://doi.org/10.25675/3.024710 Structural studies of several metal ion complexes with the tetraanion of the octadentate ligand, H^4EGTA (3,12-bis(carboxymethyl)-6, 9-dioxa-3, 12-diazatetradecanedioic acid), as well as the structure of H^4EGTA, have been performed by single crystal X-ray diffraction. Of particular interest was the structural basis for the large preference for EGTA^4- to bind calcium ion rather than (K(CaL^2-) ~= 10^6 magnesium ion = 10^6 (K(MgL^2-)), a preference which is similar to that exhibited by intracellular calcium binding proteins. The alkaline earth compounds, Ca[Ca(EGTA)]·(22/3)H2o, Sr[Ca(EGTA)] ·6H2O, Mg[Sr(EGTA)(OH2 )]·7H2o, Mg(Ba-(EGTA)]·(8/3)H2O·(1/3) (CH3) 2CO, and (Mg2(EGTA)(OH2 )6]·5H2O, have been structurally characterized. [Ca(EGTA)]2- is eight-coordinate and utilizes the full octadentate chelating capability of the EGTA^4- ligand. The ether oxygen atoms are bound at a shorter distance than the amine nitrogen atoms. EGTA^4 - is octadentate toward both the strontium and barium ions, which are nine- and ten-coordinate, respectively. The magnesium complex is dinuclear, utilizing each end of the EGTA^4- ligand as a tridentate iminodiacetate ligand; the ether oxygen atoms are not involved in coordination to the metal ion. Structures of EGTA^4 - chelates of metal ions that are commonly used as spectroscopic probes for calcium ion binding sites have also been determined. The cadmium chelate in Sr[Cd(EGTA)]·7H2 o is eight-coordinate, li k e [Ca(EGTA)]^2 -, but the amine nitrogen atoms are bound at shorter distances than the ether oxygen atoms. The metal ions in the structures of tripositive lanthanide ion complexes, Ca[Er(EGTA)(OH2)]2·12H2O and Ca[Nd(EGTA)- (OH 2 )]2·9H2O, are nine- and ten-coordinate, respectively. To further explore coordination modes of the EGTA^4 - ligand with smaller metal ions, where the ligand is not likely to be octadentate, structures of manganese and copper complexes of were determined. Sr[Mn(EGTA)] ·7H2O is isomorphous with the cadmium compound. As a result, the Mn(II) ion is eight-coordinate. The copper complex crystallizes as a dinuclear species, [CU2(EGTA)(OH2)2] ·2H2O, in which each end of the EGTA^4- ligand binds a copper(II) ion in a tetradentate fashion; the ether oxygen atom is bound in the apical position of the square pyramidal coordination sphere. doctoral dissertations English eng Colorado State University. Libraries Catalog record number (MMS ID): 991007645489703361 QP531 .S34 1985 1980-1999 Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. Metal ions Ligands Ion exchange Structural variations in metal ion complexes of the ligand EGTA⁴- Text Doctor of Philosophy (Ph.D.) Doctoral Chemistry Colorado State University This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). open.access