Coordination Compounds of Fe^3+, Co^2+, Ni^2+, Dy^3+, and Gd^3+ with
(1-Amino-1-methyl-ethyl)phosphonic Acid and a New Schiff Base Ligand

I. Doroshenko,^a^b M. Babiak,^ab A. Bucholz,^c H. Görls,^c W. Plass,^c J. Pinkas^ab*


         ^a Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2,

                                   CZ-61137 Brno, Czech Republic

  ^b Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, CZ-62500
                                       Brno, Czech Republic

     ^c Institut für Anorganische und Analytische Chemie, Friedrich-Schiller-Universität Jena,
                              Humboldtstraße 8, D-07743 Jena, Germany

jpinkas@chemi.muni.cz

In the last decade, there has been a great interest in the phosphonic acid-based molecular
complexes and coordination polymers. Because the M-O-P bonds are 1.5 times stronger then M-O-C
bonds in carboxylates, phosphonates were used in the role of molecular precursors for the synthesis
of new materials, such as polynuclear metal phosphonates, layered compounds, and porous
metal-organic frameworks, with a wide range of properties and different applications. Phosphonate
mononuclear complexes or molecular clusters with paramagnetic metal cations are very interesting
objects because of their magnetic properties. We synthesized and isolated new molecular complexes
and coordination polymers of AIPA ((1-amino-1-methyl-ethyl)phosphonic acid) and Na[x]SAA, x = 1, 2
(sodium hydrogen (2-{[(E)-(2-hydroxyphenyl)methylidene]amino}propan-2-yl)phosphonate, disodium
hydrogen (2-{[(E)-(2-oxidophenyl)methylidene]amino}propan-2-yl)phosphonate) ligands with Fe^3+,
Ni^2+, Co^2+, Dy^3+, and Gd^3+. Their properties were studied by a variety of physicochemical
methods including structural analyses by single-crystal X-ray diffraction methods. Their magnetic
properties were studied on a SQUID magnetometer. Among the most interesting results obtained in
this study are isolation and characterization of hexanuclear iron(III) phosphonate
Fe[6](NH[3](CH[3])[2]CPO[3])[12](OH)[6]].31H[2]O, a 1D coordination polymer of Fe with the SAA
ligand, a series of heptanuclear Co^2+ phosphonates with a Star-of-David structural motif, and a
coordination polymer of Ni^2+ with SAA ligands. Beside that, mononuclear isostructural complexes of
Ni^2+ and Co^2+ with AIPA were obtained and characterized. The presence of non-coordinated amino
groups in the complexes with AIPA makes these compounds potentional precursors for the synthesis of
new extended structures.