Quantentunneln der Magnetisierung und verwandte Phänomene in molekularen Materialien

Abstract

Moleküle mit einer großen Zahl gekoppelter paramagnetischer Zentren werden gegenwärtig intensiv erforscht. Man hofft auf Eigenschaften zu treffen, die zwischen denen isolierter Paramagnete und klassischer Magnete liegen, und damit einen eindeutigen Nachweis für das Auftreten von Größenquantisierungseffekten in Magneten zu erhalten. Als Prüfsteine für neue Theorien dienten bislang die beiden Clusterfamilien Mn12 und Fe8. Man darf jedoch davon ausgehen, dass die Synthesechemie in naher Zukunft weitere Klassen mit ähnlichen oder gar besseren Eigenschaften hervorbringt. Als eine Voraussetzung hierfür müssen die Beziehungen zwischen Struktur und Eigenschaften des Moleküls klar verstanden und Konzepte wie Quantentunneln, Quantenkohärenz oder Quantenoszillation gut bekannt sein. Ziel dieses Aufsatzes ist es, die notwendigen Grundlagen zum Verständnis der Größenquantisierungseffekte zusammenzufassen und einen kritischen Überblick über die Entwicklung dieses jungen Forschungsgebietes zu geben.

Designed Topology and Site‐Selective Metal Composition in Tetranuclear [MM′⋅⋅⋅M′M] Linear Complexes

“…The numerous aromatic rings present in 2 help the packing of its molecules through van der Waals and p-stacking interactions; along the a axis, chains of complexes are connected through bonds between aromatic moieties of the L 4À ligands, whereas in the a direction the molecules pack with the help of p-p interactions between pyridine ligands. Although almost two hundred [Co 4 ] clusters have been reported, we have only found three examples consisting of linear strings of four cobalt ions, [31][32][33] thus confirming the rarity of discrete linear clusters in coordination chemistry.…”

“…For example, in the arenas of molecular magnetism and spintronics, efforts are being directed towards the implementation of single-molecule magnets as information storage devices, [1][2][3][4] the use of spin-crossover materials as robust addressable and readable bi-stable materials [5,6] or the realisation of quantum computing by means of spin clusters as qbit quantum gates. [7,8] These challenges demand great deftness by chemists in their choice and exploitation of new or existing synthetic tools for the design and preparation of functional materials with the desired properties.…”

“…A research effort has therefore been undertaken to understand the peculiarities of this system and explore their potential application for the purpose of designed synthesis. We report here a series of complexes that result from exploiting the chemical and structural features of H 4 6 ] (1), [17] attempts to reproduce similar assembly processes with other metals of interest were carried out. Thus, the reaction of H 4 L with CoA C H T U N G T R E N N U N G (AcO) 2 and NaH (1:2:6 molar ratio) in pyridine heated at reflux yielded the tetranuclear complex [Co 4 L 2 (py) 6 ] (2; Figure 1, top and Figure S1 in the Supporting Information).…”

Enhancing the Blocking Temperature in Single‐Molecule Magnets by Incorporating 3d–5d Exchange Interactions

“…X-ray crystallographic experiments reveal that 1 is isostructural with the Mn III -Fe III -Mn III analogue (2). Both compounds exhibit a frequencydependent out-of-phase c''(T) alternating current (ac) susceptibility signal that is suggestive of SMM behaviour.…”

New Members of the Editorial Board and International Advisory Board

“…Her publications in Angewandte Chemie include a Review in which quantum tunneling of magnetization and related phenomena in molecular materials are discussed, and a Communication outlining how coupling of two Dy 3 triangles enhances the barrier height of magnetization reversal. [6] A Highlight on chilling with magnetic molecules appears in this issue. [7] Retiring Members…”