Magnetic resonance and structural study of the cluster fluoride Nb6F15

In this work, we report updated structural data, obtained by single-crystal X-ray diffraction, on the binary fluoride Nb6F15 as well as measurements of F-19 NMR over the temperature range 100-300K, and EMR measurements over the temperature range 4-300K. Nb6F15 is built up from (Nb6F12F6a)-F-i octahedral cluster units sharing all apical fluorine ligands to form linear Nb-F-a-Nb interunit bridges (F-i: inner fluorine located in edge-bridging position, F-a : apical fluorine located in terminal position). The F-19 NMR results showed two resonance lines. One line corresponds to the inner fluorine F-i in the (Nb6F12)(-3) cluster core. The second F-19 NMR line corresponds to the apical F a. The shift of the NMR signal from P depends on the temperature and exhibits a Curie type behavior, while the position of the NMR signal from P is temperature independent. EMR measurements show a single Lorentzian line. The temperature dependence of the inverse of the intensity of the EMR line shows a Curie-Weiss behavior and an onset to an antiferromagnetic (AF) order at 5 K. (c) 2006 Elsevier B.V. All rights reserved.