Abstract
A series of heterometallic GdIII-VIV compounds were synthesized by the reaction of VOSO4·3H2O with cyclobutane-1,1-dicarboxylic acid salts M2(cbdc) (M = Na, Rb, Cs). The new compounds were formed by [Gd(VO)2(cbdc)4(H2O)8]− trinuclear anionic units that were similar in composition but differed in structure, depending on the nature of the alkali metal cation incorporated in the crystal structure of the compound. In the case of Na+, the {GdV2}− units were characterized by identical V···Gd distances and were linked into the 1D-polymeric chain [NaGd(VO)2(cbdc)4(H2O)10]n (1). In the systems with Rb+ and Cs+, the V···Gd distances were different, and the {GdV2}− units were linked into the 3D-framework {[RbGd(VO)2(cbdc)4(H2O)10]·2.5H2O}n (2) and the octanuclear molecule {[CsGd(VO)2(cbdc)4(H2O)11]·5H2O}2 (3), respectively. According to dc-magnetic measurements, the VIV and GdIII ions were ferromagnetically coupled in compound 1 (JVGd = 0.163 ± 0.008 cm−1), while in compounds 2 and 3, ferro- and weak antiferromagnetic exchange interactions were observed (JVGd = 0.989 ± 0.028 and −0.089 ± 0.008 cm−1 for 2, 0.656 ± 0.009 and −0.050 ± 0.004 cm−1 for 3). Analysis of the EPR spectra of 1 revealed the presence of weak magnetic anisotropy of GdIII ions (D ~ 0.08 cm−1 and E/D ~ 0.1–0.15). Ac-susceptibility measurements showed an occurrence the field-induced slow relaxation of magnetization in 1–3.
Highlights
The interest in the directed synthesis of heterometallic compounds where 3d and 4f metal ions are combined in a single molecule is caused by the wide range of physicochemical properties they exhibit, including luminescent properties [1,2], molecular magnetism [3,4], magnetocaloric effect [5,6,7,8,9], and catalytic activity [10,11,12]
Studies on such heterometallic compounds are of fundamental concern in order to elucidate the exchange interactions between paramagnetic centers of different nature, 3d and 4f metal ions, and the effect of these interactions on the dynamic characteristics of a single-molecule magnet (SMM), for example, the magnitude of the energy barrier to magnetization reversal ∆eff
This work aimed at varying the alkali metal cation MI (MI = Na, Rb, Cs) in the MI -GdIII -VIV system and studying its effect on the composition, structure, and magnetic properties of the resulting compounds
Summary
Introduction published maps and institutional affilThe interest in the directed synthesis of heterometallic compounds where 3d and 4f metal ions are combined in a single molecule is caused by the wide range of physicochemical properties they exhibit, including luminescent properties [1,2], molecular magnetism [3,4], magnetocaloric effect [5,6,7,8,9], and catalytic activity [10,11,12]. Studies on such heterometallic compounds are of fundamental concern in order to elucidate the exchange interactions between paramagnetic centers of different nature, 3d and 4f metal ions, and the effect of these interactions on the dynamic characteristics of a single-molecule magnet (SMM), for example, the magnitude of the energy barrier to magnetization reversal ∆eff. From this point of view, the most convenient objects for studies by physicochemical methods include systems with a 3d center containing one unpaired electron (S = 1/2, quantum spin), namely a CuII (3d9 ) or VIV (3d1 ) ion. A number of CuII –4f systems, from molecular complexes to coordination polymers, have already been well iations.
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