Diol-type ligands as central ‘players’ in the chemistry of high-spin molecules and single-molecule magnets

Abstract

The combination of diol-type ligands with paramagnetic transition metal ions has led to the isolation of a host of new homometallic and heterometallic clusters, high-spin molecules and single molecule magnets ranging in nuclearity from two to forty four and with spin ground states as large as S = 61/2. The ligands, whose cluster coordination chemistry is discussed in this article, are 1,3-propanediol and its derivatives, diethanolamine and its derivatives, pyridine-2,6-dimethanol and the gem-diol form of di-2-pyridyl ketone. The structural diversity of the complexes stems from the ability of the ligands to adopt a variety of bridging coordination modes depending on the positions of the two hydroxyl groups in the molecule, the presence/absence of extra donor groups and on the reaction conditions. Examples of 'true' reactivity chemistry involving clusters of diol-type ligands are also given. The activation of pyridine-2,6-dimethanol and di-2-pyridyl ketone by 3d-metal centres towards further reactions seems to be an emergent area of synthetic chemistry.

A [Mn32] Double‐Decker Wheel

“…The reaction of MnBr 2 ·4 H 2 O, NaO 2 CMe, 2-phenyl-1,2-propanediol (Ph-pdH 2 ), and 2-hydroxyacetophenone oxime (Me-saoH 2 ) in a 1:1:1:1 molar ratio in MeCN leads to the isolation of [Mn 32 (m 4 -O) 8 (m 3 -OH) 6 (Me-sao) 14 [18] charge-balance considerations, and inspection of metric parameters.…”

“…[1][2][3]6] The latter of these have always attracted intense interest, partly because of their inherent structural beauty, but also because they represent model systems for the study of one-dimensional magnetism, spin frustration, and quantum effects and are promising candidates for use as qubits in quantum computation.…”

Unprecedented chemical transformation: crystallographic evidence for 1,1,2,2-tetrahydroxyethane captured within an Fe6Dy3 single molecule magnet

“…Thus, interesting results, which could never be predicted or expected, can be obtained, indicating that more systematic studies are required in order to understand the factors operating for a given reaction system. In this context and choosing triethanolamine as the organic ligand we have described the synthesis of a homometallic heptanuclear Fe 7 13 In this communication we report the synthesis, structure, magnetic properties and Mössbauer studies of a new heterometallic nonanuclear iron-dysprosium cluster displaying SMM behaviour and a U eff barrier of 65.1 K which is the highest so far observed for Fe-Ln systems. Furthermore, the unprecedented chemical transformation of part of the triethanolamine ligand to give a deprotonated 1,1,2,2-tetrahydroxyethane tetraanion has taken place and this is captured within the metallic core.…”

“…For example, sustained water oxidation photocatalysis can be achieved by a bioinspired molecular cluster, 1 lanthanide-based clusters are employed in optics as lasers and light-emitting diodes, 2 and polyoxometalates show in vivo antiviral activity 3 while many polymetallic compounds can be considered as molecule-based magnets. 4 In the field of molecular magnetism, the selection of the appropriate organic ligand to bridge metal centres for the synthesis of coordination clusters is a vital component, which has led to the investigation by a number of research groups into the coordination capabilities of organic molecules such as calixarenes, 5 phosphonates, 6 diols, 7 and triethanolamine-based ligands. 8 In selecting flexible or semi-flexible organic molecules a rational design of a desirable product is not feasible because a slight change in the synthetic parameters (mole ratios, counterions and so on) may, and often does, result in different products.…”

Molecular Copper(II) Complexes Derived from Phosphonoacetic Acid: Crystal Structures and Magnetic Behavior

“…As far as we know, only one dinuclear transition-metal compound with a hydrogenphosphonoacetate bridging ligand has been published, but no magnetic measurements were reported. [15] In contrast, di-2-pyridyl ketone (dpk; Scheme 2, A) has been extensively employed as a templating ligand for the synthesis of polynuclear compounds with variable nuclearities, [28][29][30] because of its ability to undergo metal-mediated nucleophilic addition of small molecules such as water and Scheme 2. alcohols (ROH) to the carbonyl group, which results in the formation of gem-diols and hemiketals, respectively (Scheme 2, B and C, respectively). Usually, the mono-and dianion derivatives of the gem-diols and the monoanion of the hemiketals can bridge two or more metal ions.…”