Dušan Valigura

Bio: Dušan Valigura is an academic researcher from Slovak University of Technology in Bratislava. The author has contributed to research in topics: Crystal structure & Copper. The author has an hindex of 17, co-authored 86 publications receiving 1113 citations.

A mononuclear Ni(II) complex: a field induced single-molecule magnet showing two slow relaxation processes

Abstract: The mononuclear complex [Ni(pydc)(pydm)]·H2O, pyridine-2,6-dicarboxylato-2,6-bis(hydroxymethyl)pyridine nickel(II) monohydrate, features a highly axially compressed pseudo-octahedral chromophore with significant rhombic contribution that is responsible for the sizable magnetic anisotropy of the Ni(II) ion, D/hc ≈ −14 cm−1. This complex displays superparamagnetic behaviour in an applied external field that culminates at BDC = 0.2 T. Two relaxation processes are evidenced; the faster can be analyzed in terms of the Orbach, direct, and Raman processes yielding U/kB = 21.2 (±1.3) K and τ0 = 3.83 (±1.21) × 10−7 s. This is the first example of a field-induced single-molecule magnet in the class of hexacoordinate Ni(II) complexes.

FUROPYRIDINES AND FUROPYRIDINE-Ni(II) COMPLEXES Synthesis, thermal and spectral characterization

Abstract: The thermal decomposition of the complexes Ni(SCN)2(fp)4·2H2O (I), Ni(SCN)2(mfp)4 (II) and Ni(SCN)2(dmfp)3 (III) (where fp=furo[3,2-c]pyridine, mfp=2-methylfuro[3,2-c]pyridine and dmfp=2,3-dimethylfuro[3,2-c]pyridine) have been investigated in dynamic air from room temperature to 1000°C by means of TG, DTG and DTA. The chemical composition of the complexes, solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. The results revealed that NiO was left as residue at the end of the thermal degradation experiments. IR data suggested that fp, mfp and dmfp were coordinated to Ni(II) through the N atom of the respective heterocyclic ring.

Field Supported Slow Magnetic Relaxation in a Mononuclear Cu(II) Complex

Abstract: A mononuclear hexacoordinate Cu(II) complex shows a field induced slow magnetic relaxation that is not facilitated by an energy barrier to spin reversal due to the zero-field splitting. Two relaxation channels were found: the magnetic field strongly supports the low-frequency relaxation path with a relaxation time as long as τ = 0.8 s at T = 1.9 K and B = 1.5 T. The mechanism of the relaxation at low temperature involves the dominant Raman process for this S = 1/2 spin system along with a temperature-independent term belonging to a quantum tunneling.

New dimeric copper(II) complex [Cu(5-MeOsal)2(μ-nia)(H2O)]2 with magnetic exchange interactions through H-bonds

Abstract: The synthesis and characterization (elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 18 K–300 K) of solid complex [Cu(5-MeOsal)2(μ-nia)(H2O)]2 (1; 5-MeOsal = 5-methoxysalicylate, nia = nicotinamide) is reported together with the crystal structure In blue–green complex 1, two Cu(5-MeOsal)2(H2O) units are held together by a pair of bidentate nonchelating nicotinamide ligands, which form a (CuNC3O)2 ring Each Cu atom adopts a distorted square-pyramidal geometry The oxygen atoms from two unidentate 5-MeOsal anions occupy the trans position, a water molecule and the pyridine N atom of nicotinamide build the basal plane and a carboxamide O atom occupies the apical position The separation between two Cu atoms within the centrosymmetric dimer is 6940(2) A The dimeric units are self-assembled across a centre of symmetry by the formation of two pairs of strong hydrogen bonds, which create a one-dimensional polymeric structure with the interdimer Cu···Cu separation 4901(2) A It is believed that these hydrogen bonds between the copper(II) atoms are responsible for the unique magnetic properties of compound 1 The magnetic susceptibility of complex 1 exhibits a maximum at 6 K A satisfactory explanation was found with the Bleaney–Bowers equation for Cu–Cu interaction through carboxylato groups and H-bond bridges (2J = –683 cm–1) An additional molecular field correction that was used to characterize the interaction across the nia bridges is assumed to be extremely weak (zJ′ = –028 cm–1) (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2006)

The rise of 3-d single-ion magnets in molecular magnetism: towards materials from molecules?

Abstract: Single-molecule magnets (SMMs) that contain one spin centre (so-called single-ion magnets) theoretically represent the smallest possible unit for spin-based electronic devices. The realisation of this and related technologies, depends on first being able to design systems with sufficiently large energy barriers to magnetisation reversal, Ueff, and secondly, on being able to organise these molecules into addressable arrays. In recent years, significant progress has been made towards the former goal - principally as a result of efforts which have been directed towards studying complexes based on highly anisotropic lanthanide ions, such as Tb(iii) and Dy(iii). Since 2013 however, and the remarkable report by Long and co-workers of a linear Fe(i) system exhibiting Ueff = 325 K, single-ion systems of transition metals have undergone something of a renaissance in the literature. Not only do they have important lessons to teach us about anisotropy and relaxation dynamics in the quest to enhance Ueff, the ability to create strongly coupled spin systems potentially offers access to a whole of host of 1, 2 and 3-dimensional materials with interesting structural and physical properties. This perspective summarises recent progress in this rapidly expanding sub-genre of molecular magnetism from the viewpoint of the synthetic chemist, with a particular focus on the lessons that have so far been learned from single-ion magnets of the d-block, and, the future research directions which we feel are likely to emerge in the coming years.

Understanding the Magnetic Anisotropy toward Single-Ion Magnets.

Abstract: ConspectusSingle-molecule magnets (SMMs) can retain their magnetization status preferentially after removal of the magnetic field below a certain temperature. The unique property, magnetic bistable status, enables the molecule-scale SMM to become the next-generation high-density information storage medium. SMMs’ new applications are also involved in high-speed quantum computation and molecular spintronics. The development of coordination chemistry, especially in transition metal (3d) and lanthanide (4f) complexes, diversifies SMMs by introducing new ones. In both 3d and 4f SMMs, the ligands play a fundamental role in determining the SMMs’ magnetic properties. The strategies for rationally designing and synthesizing high-performance SMMs require a comprehensive understanding of the effects of a crystal field.In this Account, we focus mainly on the magneto-structural correlations of 4f or 3d single-ion magnets (SIMs), within which there is only one spin carrier. These one-spin carrier complexes benefit from...

Single Ion Magnets from 3d to 5f: Developments and Strategies.

Abstract: Single-ion magnets (SIMs), exhibiting slow magnetization relaxation in the absence of the magnetic field, originate from their single spin-carrier centre. In pursuit of high-performance magnetic properties, such as high spin-reversal barrier and high blocking temperature, various metal centres were investigated to establish SIMs, including 3d and 5d transition metal ions, 4f lanthanide ions, and 5f actinide ions, which possess unique zero-field splitting and magnetic properties. Therefore, proper ligand field is of great importance to different types of metals. In the given great breakthroughs since the first SIM, [Pc2 Tb]- (Pc=dianion of phthalocyanine), was reported, strategies of ligand field design have emerged. In this review, the developments of SIMs with different metal centres are summarized, as well as the possible strategies.