Single-Molecule Magnets: From Mn12-ac to dysprosium metallocenes, a travel in time

The discovery of the first Single-Molecule Magnet, Mn12-ac, in 1993 changed the perspective of how information can be stored. The current bit, occupying few hundreds of nanometers in present devices, would be minimized to tens of angstroms at molecular level. However, until a couple of years these materials could only operate at temperatures near to the absolute zero. From 1993 to date, the field of Single-Molecule Magnets (SMMs) has continuously evolved thanks to the close collaboration of chemists and physicists obtaining materials already operating above the liquid nitrogen temperature. This long journey, however, has involved the study of many different routes towards high performance SMMs, being each of them essential in order to deeply understand the quantum dynamics behind these molecules. An era of high spin 3d metal clusters was the beginning of everything, but it went through highly anisotropic low coordinate 3d compounds, lanthanide based magnets, radical bridged compounds and 3d-4f mixed systems, among others, to end up in the current state of the art dysprosium metallocenes. Furthermore, after the magnetic studies in bulk, SMM based hybrid systems are emerging for future application devices, which also involve very interesting multifunctionalities. All in all, this work aims to explain how these materials work and show the trajectory and some of the major advances that have been made during recent years in this fieldThis work was supported by the Spanish Ministerio de Innovación, Ciencia y Universidades (PGC2018 102052-B-C21) and by the University of the Basque Country (GIU 17/13). E.C. is gratefully acknowledged to the Junta de Andalucía (FQM-195 and the Project financed by FEDER funds A-FQM-172-UGR18). A.Z.-L. is grateful for his predoctoral fellowship from GV/EJ

Magnetic and Luminescent Properties of Isostructural 2D Coordination Polymers Based on 2-Pyrimidinecarboxylate and Lanthanide Ions

A couple of isostructural coordination polymers with the general formula [Ln4(pymca)4(AcO)8]n have been obtained from reactions between pyrimidine-2-carboxylate (pymca) ligand and rare-earth ions (Ln = Dy (1), Nd (2)). These two-dimensional compounds have been characterized and the crystal structures have been solved by single-crystal X-ray diffraction technique, resulting in layers along the bc plane based on pymca and acetate anions that act as bridging ligands between metal atoms. Given that pymca and acetate anions possess carboxylate and hetero-nitrogen groups, it is possible to build a coordination polymer whose metal centers have a nine coordination. Furthermore, static and dynamic magnetic measurements of compound 1 reveal the lack of single molecule-magnet (SMM) behavior in this system due to the following two effects: (i) the ligand field does not stabilize magnetic ground states well separated from excited states, and (ii) anisotropy axes are not collinear, according to results with Magellan software. On another level, luminescent properties of compounds 1 and 2 are attributed to singlet π-π* transitions centered on pymca ligand as corroborated by time-dependent density functional theory (TD-DFT) calculations.Junta de Andalucia FQM-394Red Guipuzcoana de Ciencia, Tecnologia e Innovacion OF218/2018University of Basque Country GIU 17/13Basque Government IT1005-16Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE) PGC2018-102052-A-C22 PGC2018-102052-B-C21 PGC2018-102047-B-I00European funding (ERDF)European funding (ESF)Government of the Basque Countr

Iman Molekularrak: informazio unitate txikienaren bila

Nowadays, storing the highest possible amount of information in size re-duced devices is one of important concerns of society. Even though this kind of tech-nology is quite developed, the discovery of the Mn12-ac coordination compound in 1993 was considered a huge step. This is because Single Molecule Magnets (SMMs) represent the smallest information units. Therefore, new devices based on this kind of materials would enhance information storage capacity. In the present work, the most important and representative discoveries since 1993 have been summarized.; Ahalik eta informazio gehien ahalik eta espazio murritzenean gorde-tzea gizartearen gaur egungo beharra eta nahia da, aldi berean. Zentzu honetan teknolo-gia dezente aurreratua badago ere, 1993. urtean Mn12-ac koordinazio konposatua aur-kitu zenean sekulako aurrerapausoa eman zen. Izan ere, Iman Molekular (SMM, Single Molecule Magnet) deituriko konposatu hauek informazio unitatea molekula bakar ba-tera murriztea ahalbidetzen dute. Ondorioz, material hauekin sortutako gailuek askoz ere potentzial handiagoa izango lukete. Lan honetan 1993. urtetik gaur arte emandako aurrerapauso garrantzitsuenak laburbiltzen dira

Combined experimental and theoretical investigation on the magnetic properties derived from the coordination of 6-methyl-2-oxonicotinate to 3d-metal ions

Five new compounds are reported herein starting from 2-hydroxy-6-methylnicotinic acid (H2h6mnic) and first-row transition metal ions, although H2h6mnic shows a prototropy in solution to lead to the 6-methyl-2-oxonicotinate (6m2onic) ligand that is the molecule eventually present in the compounds. The structural and chemical characterization reveals the following chemical formulae: {[MnNa(μ-6m2onic)(μ-6m2onic)(MeOH)]·HO·MeOH} (1Mn), {[MNa(μ-6m2onic)(μ-6m2onic)(μ-HO)(HO)](NO)} [M = Co (2Co) and Ni (3Ni)], 2[Cu(6m2onic)(μ-6m2onic)(MeOH)]·[Cu(6m2onic)(μ-6m2onic)]·2[Cu(6m2onic)(MeOH)]·32HO (4Cu) and {[Cu(μ-6m2onic)]·6HO} (5Cu) (where 6m2onic = 6-methyl-2-oxonicotinate). An unusual structural diversity is observed for the compounds, ranging from isolated complexes (in 4Cu), 1D arrays (in 1Mn and 5Cu) and 3D frameworks (in 2Co and 3Ni). Magnetic properties have been studied for all compounds. Analysis of the magnetic dc susceptibility and magnetization data for 4Cu and 5Cu suggests the occurrence of ferromagnetic exchange, which is well explained by broken-symmetry and CASSCF calculations. The sizeable easy-plane magnetic anisotropy present in compound 2Co allows for a field-induced magnet behaviour with an experimental effective energy barrier of 16.2 cm, although the slow relaxation seems to be best described through Raman and direct processes in agreement with the results of ab initio calculations.This work has been funded by the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-B-C21), University of the Basque Country (GIU20/028), Gobierno Vasco/Eusko Jaurlaritza (IT1005-16, IT1291-19), and Junta de Andalucía (FQM-394 and B-FQM-734-UGR2). OPC thanks his predoctoral fellowship to UPV/EHU. The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF)

Dilution effect on the slow relaxation of a luminescent dysprosium Metal-Organic Framework based on 2,5-dihydroxyterephthalic acid

A new dysprosium based Metal-Organic Framework with {[Dy(dhbdc)(DMF)]·DMF} formula has been obtained from solvothermal reaction with 2,5-dihydroxyterephthalic acid ligand and dysprosium chloride. This coordination polymer has been characterized and its crystal structure has been solved by X-ray diffraction methods elucidating a three-dimensional network. Magnetic studies of this compound reveal the existence of weak antiferromagnetic interactions among the metal ions with θ value of −0.26 K. Dynamic ac magnetic susceptibility measurements were carried out under an external dc field of 1 kOe, highlighting that at high frequencies two relaxation processes can be observed. However, when studying the diamagnetically diluted analogue 1, a single relaxation process was detected highlighting the effect of the weak but not negligible exchange interactions. Finally, photoluminescence measurements were performed at different temperatures with the aim of getting a more representative characterization of the emissive performance of the material for potential applications in lighting and thermometry.Financial support was given by Junta de Andalucía (Spain) (project number FQM-394 and FQM-1484), University of the Basque Country (GIU 17/13), Gobierno Vasco/Eusko Jaurlaritza (IT1005-16) and the Spanish Ministry of Economy and Competitiveness (MCIU/AEI/FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-B-C21 and CTQ-2015-64049-C3-3R). The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). A.Z.-L. is grateful to the Government of the Basque Country for the predoctoral fellowshi