The First Series of Heterometallic LnIII-VIV Complexes Based on Substituted Malonic Acid Anions: Synthesis, Structure and Magnetic Propertiesстатья
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Аннотация:The reaction of VOSO4 with K2cbdc (cbdc2– is cyclobutane-
1,1-dicarboxylate anion) and Ln(NO3)3 (Ln = La, Ce, Pr,
Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu) yielded 17 novel
heterometallic LnIII-VIV compounds comprising stable bischelate
units {VIVO(cbdc)2(H2O)}. Three structural types of compounds
are formed depending on the nature of the rare-earth
metal: 1D polymers {[Ln(VO)(cbdc)2(H2O)7]·0.5[VO(cbdc)2]}n
(structural type I) [Ln = La (1), Ce (2)], 3D polymers
{[KLn(VO)2(cbdc)4(H2O)9]·3.5H2O}n (structural type II) [Ln = La
(3), Ce (4), Pr (5), Nd (6), Sm (7), Eu (8), Gd (9), Tb (10), Dy (11),
Ho (12)] comprising trinuclear units {LnV2}, and octanuclear
complexes {[KLn(VO)2(cbdc)4(H2O)11]·2H2O}2 (structural type III) [Ln = Y (13), Er (14), Tm (15), Yb (16), Lu (17)] containing dinuclear
units {LnV}. Magnetic properties were investigated for
all isolated compounds. The GdIII-VIV compound has ferromagnetic
and antiferromagnetic exchange interactions between isotropic
VIV and GdIII ions. Calculations using the DFT method at
the UB3LYP/6-31G(d,p)/SDD level of theory were performed in
order to explain the different nature of exchange interactions
in two GdIII-VIV pairs. The YbIII-VIV complex displays single-molecule
magnet properties; the effective energy barrier was estimated
at ΔEeff/kB = 26 K. The magnetic properties of LnIII-VIV
compounds with heavy lanthanide ions (LnIII = Er, Tm, Yb) were
rationalized in terms of crystal-field calculations for LnIII ions.