کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1306015 | 1499195 | 2012 | 9 صفحه PDF | دانلود رایگان |
5-Acetyl-substituted pyrazole-3-carboxylic acid (H2L) forms [2×2] grid-like tetranuclear Cu(II) complexes with four five-coordinated copper(II) ions bridged by pyrazolate groups. Despite a significant dissociation of [Cu4L4(H2O)4]·4H2O (1) in aqueous solution1, it was possible to substitute the coordinated water molecules by pyridine ligands or azide anions. The resulting tetranuclear complexes [Cu4L4Py4]·2H2O (2) and Na4[Cu4L4(N3)4]·7MeOH (3) were isolated and studied by X-ray diffraction analysis. In 2 and 3 the azide anions or pyridine molecules complete the distorted square-pyramidal coordination of each copper(II) center. Magnetic susceptibilities of the obtained compounds have been measured by SQUID techniques. Simulation of the data using a Heisenberg spin Hamiltonian approach showed that the bridges between the metals mediate weak intramolecular antiferromagnetic coupling (J in the range −13.3 to −17.1 cm−1) and lead to a singlet ground state in all cases.
In the present work, new grid-type coordination compounds were synthesized by subsequent reactions, using one equivalent of 1 and four equivalents of either pyridine or NaN3 to produce complexes 2 and 3, respectively. Solution behavior, structural features and magnetic properties of obtained complexes were studied.Figure optionsDownload as PowerPoint slideHighlights
► Novel tetranuclear complexes with asymmetric pyrazolate ligand have been synthesized.
► The [2×2] grid copper(II) complex is used as a precursor.
► We report the X-ray crystal structures of the tetranuclear grid-like complexes.
► The nature of additional ligands and substituents explain the differences in J values.
Journal: Inorganica Chimica Acta - Volume 392, 30 September 2012, Pages 322–330