Coordination Clusters of 3d-Metals That Behave as Single-Molecule Magnets (SMMs): Synthetic Routes and Strategies

Abstract

The area of 3d-metal coordination clusters that behave as Single-Molecule Magnets (SMMs) is now quite mature within the interdisciplinary field of Molecular Magnetism. This area has created a renaissance in Inorganic Chemistry. From the synthetic Inorganic Chemistry viewpoint, the early years of “try and see” exercises (1993–2000) have been followed by the development of strategies and strict approaches. Our review will first summarize the early synthetic efforts and routes for the preparation of polynuclear 3d-metal SMMs, and it will be then concentrated on the description of the existing strategies. The former involve the combination of appropriate 3d-metal-containing starting materials (simple salts with inorganic anions, metal cardoxylates, and pre-formed carboxylate clusters, metal phosphonates) and one or two primary organic ligands; the importance of the end-on azido group as a ferromagnetic coupler in 3d-metal SMM chemistry will be discussed. The utility of comproportionation reactions and the reductive aggregation route for the construction of manganese SMMs will also be described. Most of the existing strategies for the synthesis of SMMs concern manganese. These involve substitution of carboxylate ligands in pre-formed SMMs by other carboxylate or non-carboxylate groups, reduction procedures for the {Mn8IIIMn4IV} SMMs, spin “tweaking,” “switching on” SMM properties upon conversion of low-spin clusters into high-spin ones, ground-state spin switching and enhancing SMM properties via targeted structural distortions, the use of radical bridging ligands and supramolecular approaches. A very useful strategy is also the “switching on” of SMM behavior through replacement of bridging hydroxide groups by end-on azido or isocyanato ligands in clusters. Selected examples will be mentioned and critically discussed. Particular emphasis will be given on the criteria for the choice of ligands.

Diversity of Coordination Modes in a Flexible Ditopic Ligand Containing 2-Pyridyl, Carbonyl and Hydrazone Functionalities: Mononuclear and Dinuclear Cobalt(III) Complexes, and Tetranuclear Copper(II) and Nickel(II) Clusters

“…Magnetochemistry 2019, 5, x FOR PEER REVIEW 3 of 23 from the synthetic investigation of the CuBr2/LH, Ni(NO3)2•6H2O/LH and Co(ClO4)2•6H2O/LH reaction systems and the characterization of the products obtained. This paper can be considered as a continuation of our interest in the chemistry and magnetism of 3d-metal coordination clusters [9,22], and in the coordination and metal ion-meditated/promoted transformation properties of polydentate ligands containing two or more functionalities (including 2-pyridyl, carbonyl and hydrazone/azine groups, among others) [4,[23][24][25][26][27].…”

Chemical Assembling of Heterometallic {Cd–M} (M=Li, Mg, Eu, Tb) Molecules with 3,5‐Di‐tert‐butylbenzoate Bridges and N‐Donor Ligands

“…In contrast to this process, chemical self-assembly of a heteronuclear system from a mixture of Cd(NO 3 ) 2 , Mg(NO 3 ) 2 and K(bzo) (Cd:Mg : K = 2 : 1 : 6) in the presence of a 10-fold excess of lut or a stoichiometric amount of 1,10-phenanthroline (phen) resulted in trinuclear compounds with the composition [Cd 2 Mg(bzo) 6 (L) 2 ]⋅Solv (L = lut (III), phen (IV); Solv = 2EtOH (III), 6CH 2 Cl 2 (IV); Scheme 1) containing Cd(II) and Mg(II) ions, as well as lutidine or phenanthroline, respectively. The reactions of compound I obtained in situ, Eu(bzo) 3 O⋅MeCN (Ln = Eu (IX), Tb (X); Scheme 1) also containing an N-donor ligand. As a result, we created a scheme describing the formation of heteronuclear complexes with Cd(II) ions depending on the nature of the Ndonor ligands added and their amount (Scheme 1).…”

“…Carboxylate complexes of transition metals are unique starting compounds for synthesizing new types of molecular and polymeric compounds by reactions with N-donor ligands and/ or polycarboxylic acids. [1][2][3][4][5][6] The range of known compounds is also expanded by synthesizing heterometallic complexes where ions of 3d-metals and ions of alkali metals, alkaline-earth elements or lanthanides may be combined in a single molecule. [7][8][9][10][11] It is important that in many cases, the polynuclear structure of the metal moiety is preserved both upon replacement of N-donor ligands and carboxylate anions, which significantly expands the options for the chemical design of new heterometallic derivatives and allows one to manipulate the physical characteristics of molecules and even the crystals that are formed from them.…”

1D Copper(II)-Aroylhydrazone Coordination Polymers: Magnetic Properties and Microwave Assisted Oxidation of a Secondary Alcohol

“…Molecular magnetism is one of the significant domains determining magneto-structural correlations to design magnetic materials (Benelli and Gatteschi, 2002;Sutradhar et al, 2012Sutradhar et al, , 2013Sutradhar et al, , 2014bSutradhar et al, , 2015aSutradhar et al, , 2018Cho et al, 2016;Andruh, 2018). Single molecule magnets (SMMs) (Karotsis et al, 2010;Glaser et al, 2015;Maniaki et al, 2018) exhibit a large spin ground-state (S) value and large negative magnetic anisotropy and are used in potential high-density information storage devices and GRAPHICAL ABSTRACT | Two new aroylhydrazone Cu(II) 1D coordination polymers [Cu 3 (L 1 )(NO 3 ) 4 (H 2 O) 2 ] n (1) and [Cu 2 (H 2 L 2 )(NO 3 )(H 2 O) 2 ] n •(NO 3 ) n (2) (H 2 L 1 = N' 1 ,N' 2 -bis(pyridin-2-ylmethylene)oxalohydrazide and H 4 L 2 = N' 1 ,N' 3 -bis(2-hydroxybenzylidene)malonohydrazide) have been structurally characterized. Their magnetic properties and the catalytic activity toward the solvent-free microwave-assisted oxidation of 1-phenylethanol have been explored.…”

“…quantum computers (Leuenberger and Loss, 2001). Therefore, many efforts have been devoted to rationally establish polynuclear metal complexes and/or clusters elucidating molecular magnetism (Benelli and Gatteschi, 2002;Karotsis et al, 2010;Sutradhar et al, 2012Sutradhar et al, , 2013Sutradhar et al, , 2014bSutradhar et al, , 2015aSutradhar et al, , 2018Glaser et al, 2015;Cho et al, 2016;Andruh, 2018;Maniaki et al, 2018). Coordination polymers and molecular clusters are particular classes of compounds that can display novel magnetic properties including high ground-state spin values and single molecule magnetism behavior (Zheng et al, 2014;Journaux et al, 2018;Yue and Gao, 2019).…”