Smart Ligands for Efficient 3d-, 4d- and 5d-Metal Single-Molecule Magnets and Single-Ion Magnets

Abstract

There has been a renaissance in the interdisciplinary field of Molecular Magnetism since ~2000, due to the discovery of the impressive properties and potential applications of d- and f-metal Single-Molecule Magnets (SMMs) and Single-Ion Magnets (SIMs) or Monometallic Single-Molecule Magnets. One of the consequences of this discovery has been an explosive growth in synthetic molecular inorganic and organometallic chemistry. In SMM and SIM chemistry, inorganic and organic ligands play a decisive role, sometimes equally important to that of the magnetic metal ion(s). In SMM chemistry, bridging ligands that propagate strong ferromagnetic exchange interactions between the metal ions resulting in large spin ground states, well isolated from excited states, are preferable; however, antiferromagnetic coupling can also lead to SMM behavior. In SIM chemistry, ligands that create a strong axial crystal field are highly desirable for metal ions with oblate electron density, e.g., TbIII and DyIII, whereas equatorial crystal fields lead to SMM behavior in complexes based on metal ions with prolate electron density, e.g., ErIII. In this review, we have attempted to highlight the use of few, efficient ligands in the chemistry of transition-metal SMMs and SIMs, through selected examples. The content of the review is purely chemical and it is assumed that the reader has a good knowledge of synthetic, structural and physical inorganic chemistry, as well as of the properties of SIMs and SMMs and the techniques of their study. The ligands that will be discussed are the azide ion, the cyanido group, the tris(trimethylsilyl)methanide, the cyclopentanienido group, soft (based on the Hard-Soft Acid-Base model) ligands, metallacrowns combined with click chemistry, deprotonated aliphatic diols, and the family of 2-pyridyl ketoximes, including some of its elaborate derivatives. The rationale behind the selection of the ligands will be emphasized.

Single Molecule Magnetism in Linear Fe(I) Complexes with Aufbau and non-Aufbau ground-state

“…[7][8][9][10][11][12] Transition metal (TM) complexes have also entered the spotlight in recent years, offering tantalizing alternatives to be utilized in prospective applications. [13][14][15] In this regard, in mononuclear complexes containing 3d-metal ions, it is essential to maintain the first-order orbital angular momentum to accomplish large magnetic anisotropy on a level comparable with Ln based complexes. 16,17 Controlling various chemical modifications in the coordination environment, such as the coordination number, geometry of the complex and nature of ligand atoms directly bonded to the metal center, assists in the conservation of the first-order orbital angular momentum.…”

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic, Structural, and Physical Studies

“…One of the first uses of oximes in metal chemistry was the gravimetric determination of Ni(II) in the form of the red bis(dimethylglyoximato)nickel(II) [ 2 ], an experiment performed by undergraduate Chemistry students in most universities. Today, oxime and oximato metal complexes are central “players” in several aspects of coordination [ 3 , 4 , 5 ] and bioinorganic [ 6 , 7 ] chemistry, molecular magnetism [ 8 , 9 , 10 , 11 ], catalysis [ 12 , 13 ], and in the area of the reactivity of coordinated ligands [ 14 , 15 , 16 ].…”

Field-induced single-ion magnet based on a quasi-octahedral Co(ii) complex with mixed sulfur–oxygen coordination environment

“…On the contrary, tetrahedral high-spin (S=3/2) Co(II) complexes in purely sulfuric or mixed environments are quite numerous and often exhibit SIM properties [20][21][22]. Although Co(II) complexes with only one thiodiacetate (TDA) ligand were previously known [23,24], until 2010 such mononuclear 3dmetal complexes were not considered as SIMs [25][26][27].…”