Building 1D lanthanide chains and non-symmetrical [Ln2] "triple-decker" clusters using salen-type ligands: magnetic cooling and relaxation phenomena.
A solvothermal reaction between Ln(NO3)3·6H2O (Ln: Gd, Tb and Dy), 2-hydroxy-1-naphthaldehyde, 2-OH-naphth, and ethylenediamine, en, in MeOH in the presence of a base, NEt3, led to the formation of the 1D coordination polymers [Ln(L)(MeO)(MeOH)0.5]n·MeOH (Ln = Gd (1·MeOH), Tb(2), Dy (3·MeOH); H2L = 1,1'-((1E,1'E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol), the Schiff-base ligand derived from the condensation of 2-OH-naphth and en), while a similar reaction in an excess of NaN3yielded 1D coordination polymers [Ln(L)(N3)0.75(MeO)0.25(MeOH)]n(Ln = Gd (4), Tb (5), Dy (6)). Finally, upon replacing ethylenediamine with o-phenylenediamine, o-phen, we managed to isolate the discrete dimers [Dy2(L')3(MeOH)]·2MeOH (7·2MeOH) and [Gd2(L')3(MeOH)]·2MeOH (8·2MeOH) (H2L' = 1,1'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis (naphthalen-2-ol), the Schiff-base ligand from the condensation of 2-OH-naphth and o-phen). Polymers 1-3 describe one-dimensional chains, containing alternating seven- and eight-coordinate LnIIImetal centers, polymers 4-6 contain eight-coordinate lanthanide ions, while in both 7 and 8 the two LnIIIcenters are eight- and seven-coordinate, adopting square antiprismatic and "piano-stool" geometry, respectively. The magnetocaloric properties of the three GdIIIanalogues were determined from magnetic measurements, yielding the magnetic entropy change -ΔSm= 21.8, 23.0 and 16.0 J kg-1K-1at T = 3.0 K on demagnetization of 7 T to 0, for 1, 4 and 8, respectively. The study of the magnetic properties also revealed that all three DyIIIanalogues (3, 6 and 7) display out-of-phase signals, therefore suggesting slow magnetic relaxation, while such behaviour was not established in the TbIIIanalogues.
Department Of Chemistry, University of Crete, Voutes 71003, Herakleion, Greece. komil@uoc.gr.
Angelos B
AB
Canaj
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, Wroclaw 50-383, Poland.
Milosz
M
Siczek
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, Wroclaw 50-383, Poland.
Marta
M
Otręba
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, Wroclaw 50-383, Poland.
Tadeusz
T
Lis
Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC - Universidad de Zaragoza, 50009 Zaragoza, Spain.
Giulia
G
Lorusso
Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC - Universidad de Zaragoza, 50009 Zaragoza, Spain.
Marco
http://orcid.org/0000-0002-8028-9064
M
Evangelisti
Department Of Chemistry, University of Crete, Voutes 71003, Herakleion, Greece. komil@uoc.gr.
Constantinos J
CJ
Milios