Affinity of two highly preorganized ligands for the base metal ions Co(II), Ni(II) and Cu(II): A thermodynamic, crystallographic and fluorometric study

作者：Williams Neil J; Gephart Raymond T III; Hames Ashley E; Reibenspies Joseph H; Luckay Robert C^*; de Sousa Alvaro S; Hancock Robert D

来源：Polyhedron, 2012, 46(1): 139-148.

DOI：10.1016/j.poly.2012.08.013

• Preorganized ligands
• Base metal ions
• Formation constants
• Ni(II) and Co(II) crystal structures
• Fluorescence

The metal ion complexing properties of 1,10-phenanthroline-2,9-dicarboxylic acid (PDA), with cobalt(II) and nickel(II) are reported. These were determined by UV-Vis spectroscopy in 0.1 M NaClO4 at 25 degrees C and the logK values are 12.6 +/- 0.05 and 13.6 +/- 0.05 respectively. These two values are compared to that of the previously reported value of copper(II), as well as the previously reported values of the ligand 2,9-bis(hydroxymethyl)-1.10-Phenanthroline (PDALC). Crystal structures of {[Ni(PDALC)(2)]Cl-2}(2)center dot 5H(2)O, ([Co(PDALC)(2)]Cl-2)(2)center dot 5H(2)O and {[Ni(PDAMOD)(2)](H2O)(2)}(2) are reported, all showing distorted octahedral geometry around the metal centre. Furthermore, all three structures have four nitrogens and two oxygen atoms from alternate ligands coordinated to the metal ion. The crystal structure of the free ligand PDALC is also reported showing pi-pi stacking, hydrogen bonding with the solvent and also the extent of its preorganization. Lastly, a fluorescence study of divalent metal ions with these two ligands was carried out which included the three metal ions of interest. These results illustrate that Ca(II) produces the largest CHEF (chelation enhanced fluorescence) effects, followed by Mg(II) and Ba(II) in the PDA complexes. Metal ions with non-filled d-subshells produce very large quenching of the fluorescence. For the PDALC complexes, the largest CHEF was with Zn(II), followed by Ca(II), then Mg(II) which is the same as that of Ba(II), then closely followed by Cd(II). Both ligands show quenching effects with Co(II). Ni(II) and Cu(II) which are in the order: Co(II) %26gt; Ni(II) %26gt; Cu(II) for both ligands.

• 出版日期2012-10-9