High‐Nuclearity, High‐Symmetry, High‐Spin Molecules: A Mixed‐Valence Mn₁₀ Cage Possessing Rare T symmetry and an S=22 Ground State

Abstract

Hoch, höher, am höchsten: Die Kombination von Azid‐ und hmp−‐Liganden (hmpH=2‐(Hydroxymethyl)pyridin) ermöglichte die Synthese zweier Salze eines neuen Mn10‐Kations mit hoch symmetrischer Struktur (siehe Strukturausschnitt; MnII gelb, MnIII blau, O rot, N grün, C grau). Das Kation ist vollständig ferromagnetisch gekoppelt und hat einen S=22‐Grundzustand – einer der höchsten je beschriebenen Werte.

Structural Effects of Sodium Cations in Polynuclear, Multicubane‐Type Mixed Na–Ni Complexes

“…The diversity of compositions and structures results from the remarkable structural effects of the cations present and subtle changes in the reaction conditions. This work further demonstrates that the cluster self-assembly approach, [17] based on ligands capable of both chelating and bridging transition metals, such as HL, is very powerful because of its versatility and the resulting diversity of structures observed in dinuclear, [18] polynuclear complexes [4,10] and coordination polymers. [5e, 19] Received: March 9, 2010 Published online: May 7, 2010 .…”

“…[1] Studies of dinuclear Ni II complexes with N,OH chelates as precatalysts for ethylene oligomerization [2] triggered our interest in comparing complexes with (pyridine-2-yl)methanol (HL) and those containing the corresponding anionic chelate, partly because N,O À ligands may lead to systems that do not require any cocatalyst. [3] Furthermore, L À is well known to promote the formation of polynuclear complexes with exciting physical properties, [4] paralleling the rich chemistry of 2-pyridones. [5] We have now obtained unusual mixed nickel/sodium polynuclear complexes and identified remarkable structural effects of the sodium cations associated with the reagent used to deprotonate the alcohol function.…”

“Spin Tweaking” of a High‐Spin Molecule: An Mn25 Single‐Molecule Magnet with an S=61/2 Ground State

“…[5] Nevertheless, it is difficult to achieve a rational synthesis of a high-spin species from simple reagents, [6] and even then there is the danger that the anisotropy will be too low to either give an SMM or to give one with a reasonable barrier. Recent examples of such situations include Mn 10 , Mn 25 , and Mn 19 complexes with S = 44/2, [7] 51/2, [8] and 83/2 [9] ground states, respectively, but with minimal anisotropies (i.e. D values).…”

“…However, we knew from extensive past experience with pyridine-based alkoxide ligands that the anion of 2-(hydroxymethyl)pyridine (hmp À ) usually adopts an h 1 :h 2 :m 2 chelating/bridging mode that usually yields ferromagnetic coupling between Mn atoms. [7,13] We thus targeted replacement of the six pairs of bridging and terminal azide ions by six h 1 :h 2 :m 2 hmp À groups, which proved successful.…”

Supertetrahedral and Bi‐supertetrahedral Cages: Synthesis, Structures, and Magnetic Properties of Deca‐ and Enneadecametallic Cobalt(II) Clusters

“…However, in the model proposed for {Ni 10 }, the existence of 81 levels within the lowest-energy band makes it much more probable that the phonons are reabsorbed by a neighboring molecule, and hence trapped, leading to slow relaxation at relatively high temperatures compared with SMMs. This mechanism was initially proposed by Anderson for relaxation in paramagnetic salts at low temperature, [6] but not at high temperatures, as in {Ni 10 }.To test this theory, we required new materials, perhaps with the same topology [7] but with different values for either the local spin s or the exchange J. Although such isomorphous high-nuclearity structures are very rare, a limited number of examples, incorporating nickel or cobalt, are known [8][9][10] and, therefore, this target seemed achievable.…”