Building 1D lanthanide chains and non-symmetrical [Ln2] “triple-decker” clusters using salen-type ligands: magnetic cooling and relaxation phenomena

et al.A solvothermal reaction between Ln(NO)·6HO (Ln: Gd, Tb and Dy), 2-hydroxy-1-naphthaldehyde, 2-OH-naphth, and ethylenediamine, en, in MeOH in the presence of a base, NEt, led to the formation of the 1D coordination polymers [Ln(L)(MeO)(MeOH)]·MeOH (Ln = Gd (1·MeOH), Tb(2), Dy (3·MeOH); HL = 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 NaN yielded 1D coordination polymers [Ln(L)(N)(MeO)(MeOH)] (Ln = Gd (4), Tb (5), Dy (6)). Finally, upon replacing ethylenediamine with o-phenylenediamine, o-phen, we managed to isolate the discrete dimers [Dy(L′)(MeOH)]·2MeOH (7·2MeOH) and [Gd(L′)(MeOH)]·2MeOH (8·2MeOH) (HL′ = 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 Ln metal centers, polymers 4-6 contain eight-coordinate lanthanide ions, while in both 7 and 8 the two Ln centers are eight- and seven-coordinate, adopting square antiprismatic and “piano-stool” geometry, respectively. The magnetocaloric properties of the three Gd analogues were determined from magnetic measurements, yielding the magnetic entropy change-ΔS = 21.8, 23.0 and 16.0 J kg K at 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 Dy analogues (3, 6 and 7) display out-of-phase signals, therefore suggesting slow magnetic relaxation, while such behaviour was not established in the Tb analogues.The research fund for CJM and ABC has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) – Research Funding Program: THALES. Investing in knowledge society through the European Social Fund. GL and ME thank Spanish MINECO (MAT2015-68204-R). MS, MO and TL: “Project partially supported by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014–2018”Peer Reviewe

Pseudopeptidic ligands: exploring the self-assembly of isopthaloylbisglycine (H2IBG) and divalent metal ions

No description supplie

A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2′-Pyridil

Reactions of 2,2′-pyridil (pyCOCOpy) with CuCl2 · 2H2O and CuBr2 in EtOH yielded the mononuclear complex [Cu(pyCOOEt)2Cl2] · H2O (1) and the one-dimensional, mixed-valence complex [Cu2ICuII(pyCOOEt)2Br4]n (2), respectively. Both complexes crystallize in the triclinic space group P 1¯. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2), α = 101.17(1), β = 114.55(1), γ = 94.14(1)° for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.78(1)° for 2. 2,2′-pyridil undergoes a metal-assisted alcoholysis and oxidation leading to decomposition and yielding the ethyl picolinate (pyCOOEt) ligand. The autoredox process associated with the reduction of copper(II) to copper(I) in the case of complex 2 is discussed in terms of the increased redox activity of the copper(II) bromide system relative to the copper(II) chloride system

Heterometallic lanthanide-centred [NiII6LnIII] rings

A [NiII6DyIII] heptanuclear complex featuring a rare six-membered {NiII6} metal ring surrounding the central Dy(III) ion is reported. Magnetic studies reveal single-molecule magnet behaviour for the complex under zero external dc field, while replacing the DyIII ion with ΥIII or GdIII ions allows for a comprehensive understanding of the magnetic behaviour

A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The reaction of Co(OAc)2·4H2O with LH (LH = 11H-indeno[1,2-b]quinoxalin-11-one oxime) in MeOH in the presence of NEt3 forms the complex [CoIII2CoIIO(OAc)3L3]·0.5MeOH·0.2H2O (1·0.5MeOH·0.2H2O), while repeating the reaction under solvothermal conditions yielded the heptanuclear cluster [CoII7L9 (OH)2(OAc)2.7(MeO)0.3(H2O)]·4.6MeOH·3.3H2O (2·4.6MeOH·3.3H2O). Changing the starting metal salt to Co(ClO4)2·6H2O and upon the reaction with LH in the presence of NEt3 under high temperature and pressure, we managed to isolate the decanuclear cluster [CoII10L14(OH)3.6(MeO)0.4](ClO4)2·8.5MeOH·5.75H2O (3·8.5MeOH·5.75H2O), while under normal bench conditions and upon employment of pivalates in the reaction mixture complex [CoII4L4(piv)4(MeOH)2]·MeOH·H2O (4·MeOH·H2O) was formed. Furthermore, the reaction of Co(ClO4)2·6H2O with LH and aibH (2-amino-isobutyric acid) in the presence of NEt3 in MeOH gave the mononuclear complex [CoIIIL(aib)2]·3H2O (5·3H2O), while upon increasing the metal–ligand ratio cluster [CoIII2CoIIL4(aib)2(OH)2]·7.9MeOH (6·7.9MeOH) was isolated. Finally, repeating the reaction that yielded the mononuclear complex 5·3H2O under solvothermal conditions, gave the octanuclear cluster [CoII8L10(aib)2(MeO)2](ClO4)2·6.8MeOH·7H2O (7·6.8MeOH·7H2O). Variable temperature dc magnetic susceptibility studies for complexes 2, 3, 4 and 7, reveal that all clusters display dominant antiferromagnetic interactions leading to small or diamagnetic ground-states,

Two unique star-like [MnIVMnIII2LnIII] clusters: magnetic relaxation phenomena

Synthesis and magnetic properties of two tetrametallic star-like [MnIVMnIII2Ln] (Ln: Gd, Dy) clusters.</p

Constructing CrIII-centered heterometallic complexes: [NiII6CrIII] and [CoII6CrIII] wheels

The solvothermal reaction between Cr(acac)3, MCl2.6H2O (M= Ni, Co) and 2-hydroxy-4-methyl-6-phenyl-pyridine-3-amidoxime (H2L), under basic conditions, led to the synthesis of the heterometallic heptanuclear clusters [MII6Cr(HLzw)6(HL)6].3Cl (M= Ni, 1; Co, 2), with the nickel analogue displaying an S= 9/2 spin ground-state

Twisted molecular magnets

Journal article (post-print)The use of derivatised salicylaldoximes in manganese chemistry has led to the synthesis of a family of approximately fifty hexanuclear ([MnIII6]) and thirty trinuclear ([MnIII3]) Single-Molecule Magnets (SMMs). Deliberate, targeted structural distortion of the metallic core afforded family members with increasingly puckered configurations, leading to a switch in the pairwise magnetic exchange from antiferromagnetic to ferromagnetic. Examination of both the structural and magnetic data revealed a semi-quantitative magneto-structural correlation, from which the factors governing the magnetic properties could be extracted and used for predicting the properties of new family members and even more complicated structures containing analogous building blocks. Herein we describe an overview of this extensive body of work and discuss its potential impact on similar systems.IRCSE