title: Copper(II) complexes of tetradentate pyridyl ligands supported on Keggin polyoxometalates: single-crystal to single-crystal transformations promoted by reversible dehydration processes.
abstract: Two new hybrid compounds constructed from Keggin type polyoxometalates and copper(II) complexes of tetradentate ligands containing amine and pyridyl groups, namely [Cu(bpmen)(H2O)][SiW12O40{Cu(bpmen)}] (1) and [SiW12O40{Cu(bpmpn)(H2O)}2]·3H2O (2) (bpmen, N,N'-dimethyl-N,N'-bis-(pyridin-2-ylmethyl)-1,2-diaminoethane; bpmpn, N,N'-dimethyl-N,N'-bis(pyridin-2-ylmethyl)-1,3-diaminopropane), have been synthesized under hydrothermal conditions and characterized by elemental analyses and infrared and Raman spectroscopy. Thermal stability of 1 and 2 has been studied by means of thermogravimetric analyses and variable temperature powder X-ray diffraction. Both compounds undergo single-crystal to single-crystal transformations promoted by reversible dehydration processes that have been followed by single-crystal X-ray diffraction. Structures of 1 and 2, and also of their corresponding anhydrous phases 1a and 2a, have been established. The layered structure of 1 shows rows of monodecorated polyanions with complex cations occupying intralamellar spaces, whereas trans-didecorated species in 2 lead to stacked honeycomb-like metal-organic layers forming channels where Keggin clusters are accommodated. Structural differences relate to changes in the complex geometry and ligand conformation when going from bpmen to bpmpn. Dehydration of 1 promotes coordination of the complex countercation and consequent formation of a cis-didecorated species in 1a, whereas changes in the structure of 2a are more subtle. Structural variations upon dehydration are reflected in the electron paramagnetic resonance spectra.
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, P.O. Box 644, 48080 Bilbao, Spain.
authors.forename: Amaia
authors.initials: A
authors.lastname: Iturrospe
authors.forename: Beñat
authors.initials: B
authors.lastname: Artetxe
authors.forename: Santiago
authors.initials: S
authors.lastname: Reinoso
authors.forename: Leire
authors.initials: L
authors.lastname: San Felices
authors.forename: Pablo
authors.initials: P
authors.lastname: Vitoria
authors.forename: Luis
authors.initials: L
authors.lastname: Lezama
authors.forename: Juan M
authors.initials: JM
authors.lastname: Gutiérrez-Zorrilla