Sally Brooker

The coordination chemistry of 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles and related ligands

The coordination chemistry of 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles, as well as of the related ligands 2,5-di(2-pyridyl)-1,3,4-oxadiazole and 2,5-di(2-pyridyl)-1,3,4-thiadiazole, is comprehensively reviewed. Literature surveys of the known 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles and their complexes are provided, selected representative examples are presented and the various coordination modes that have been observed in complexes of these potentially dinucleating ligands are discussed.

Cobalt(II) complexes of pyridazine or triazole containing ligands: spin-state control

Abstract Structurally characterised cobalt(II) complexes containing pyridazine, triazole or triazolate ligands are the subject of this review. Firstly a brief introduction to Schiff-base macrocyclic chemistry is given and then the crystal structures and magnetic properties of pyridazine-containing cobalt(II) complexes are discussed, focussing on macrocyclic complexes. There follows a discussion of the crystal structures, as well as the magnetic behaviour where known, of cobalt(II) complexes containing the triazole moiety in a N 1 , N 2 -bridging fashion. Finally an overview of reported complexes where the triazole unit has been incorporated into a Schiff-base macrocyclic framework is provided. None of these triazole-containing macrocyclic complexes has been structurally characterised.

Complexes of thiophenolate-containing Schiff-base macrocycles and their amine analogues

Abstract The complexes of thiophenolate-containing Schiff-base macrocycles, and of their amine analogues, are the subject of this review. In addition to discussing the structures and properties of these nickel, copper and zinc complexes, the routes to the required thiophenolate precursors are also reviewed.

A Tetranuclear, Macrocyclic 3d-4f Complex Showing Single-Molecule Magnet Behavior

[Cu(II)(3)Tb(III)(L(Pr))(NO(3))(2)(MeOH)(H(2)O)(2)](NO(3))·3H(2)O is a rare example of a 3d-4f single-molecule magnet prepared using a macrocyclic ligand: at low T, it exhibits frequency-dependent alternating-current susceptibility, indicative of slow relaxation of the magnetization.

The first X-ray crystal structure determination of a dinuclear complex trapped in the [low spin–high spin] state: [FeII2(PMAT)2](BF4)4·DMF

The two metal centres in the doubly 1,2,4-triazole-bridged spin crossover complex [Fe(II)2(PMAT)2](BF4)4.DMF (1.DMF) are trapped in different spin states below ca. 200 K, with no evidence that this particular [LS-HS] species can be converted into the [LS-LS] form at ambient pressure.

Nano-magnetic materials: spin crossover compounds vs. single molecule magnets vs. single chain magnets

Brief introductions to spin crossover (SCO), single molecule magnetism (SMM) and single chain magnetism (SCM) are provided. Each section is illustrated by selected examples that have contributed significantly to the development of these fields, including recent efforts to produce materials (films, attachment to surfaces etc.). The advantages and disadvantages of each class of magnetically interesting compound are considered, along with the key challenges that remain to be overcome before such compounds can be used commercially as nanocomponents. This invited perspective article is intended to be easily comprehensible to non-specialists in the field.

COII2L(NCS)2(SCN)2 : THE FIRST COBALT COMPLEX TO EXHIBIT BOTH EXCHANGE COUPLING AND SPIN CROSSOVER EFFECTS

A spin crossover transition (350 K, μeff =3.15 μB per Co atom; 4.5 K, μeff =0.70 μB per Co atom) and weak antiferromagnetic exchange (2 J=-11.7 cm-1 ) between the octahedral, doubly pyridazine bridged cobalt(II) ions are features of the structurally characterized complex [CoII2 L(NCS)2 (SCN)2 ] (the ligand L is shown).

Reversible Switching of a Cobalt Complex by Thermal, Pressure, and Electrochemical Stimuli: Abrupt, Complete, Hysteretic Spin Crossover

Triply switchable [Co(II)(dpzca)(2)] shows an abrupt, reversible, and hysteretic spin crossover (T(1/2)↓ = 168 K, T(1/2)↑ = 179 K, and ΔT(1/2) = 11 K) between the high-spin (HS) and low-spin (LS) states of cobalt(II), both of which have been structurally characterized. The spin transition is also reversibly triggered by pressure changes. Moreover, in a third reversible switching mechanism for this complex, the magnetic properties can be switched between HS cobalt(II) and LS cobalt(III) by redox.

Some Copper and Cobalt Complexes of Schiff-Base Macrocycles Containing Pyridazine Head Units

The Schiff-base macrocycle L14, formed by the [2+2] condensation of 3,6-diformylpyridazine and 1,3-diaminopropane, has facilitated the preparation of the first extensive family of pyridazine-bridged macrocyclic complexes. The structural, magnetic and electrochemical behaviour of these complexes is of considerable interest. This microreview provides an overview of prior relevant studies and then describes some of the recent copper and cobalt chemistry of the macrocyclic ligand L14. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Mixed Spin‐State [HS‐LS] Pairs in a Dinuclear Spin‐Transition Complex: Confirmation by Variable‐Temperature 57Fe Mössbauer Spectroscopy

Exquisite sensitivity of Mossbauer spectroscopy for tiny local molecular distortion is demonstrated in [FeII2(pmat)2](BF4)4?DMF: high-spin (HS) iron(II) in [HS-HS] and in [LS-HS] (low-spin–high-spin) pairs is clearly distinguished (see picture) for the first time without the need to apply a magnetic field. This dinuclear complex clearly shows that spin crossover via a [LS-HS] species is promoted by the use of a highly constrained bridging ligand (the bis-terdentate pmat).