A Novel Correlation between Magnetism and Structural Parameters in Superexchange Coupled Chromium(III) Dimers.

A simple methodology for constructing ferromagnetically coupled Cr(iii) compounds

“…† An Oxford Cryosystems Cryostream 700+ low temperature device was used to maintain a crystal temperature of 120 K. The structures were solved using ShelXT or ShelXS by direct (2-7, 9) or intrinsic phasing solution methods (1,8) and refined with version 2016/6 of ShelXL interfaced with Olex2. 25,26 All non-hydrogen atoms were refined using anisotropic displacement parameters.…”

“…[1][2][3] Indeed, although more than 40 years have passed since the publication of the first ferromagnetically coupled complex in 1976, namely Na 4 [Cr(mal) 2 7 and the most recent example a di-hydroxo bridged species of formula (Ph 4 P) 4 [Cr(NCS) 4 OH] 2 published in 2014. 8 Larger Cr (III) clusters displaying ferromagnetic exchange are even more rare, with only two examples known.…”

Ferromagnetic exchange in a twisted, oxime-bridged [MnIII2] dimer

“…We note that, as the temperature is increased, many 10 more features emerge in the spectrum, especially as one approaches the isotropic g = 2.00 position. It is possible to assign many of these features to transitions within excited spin multiplet states (vide infra), e.g., z 3,3 . Finally, we note that the strongest peak in Fig.…”

“…1 For example, the relationship between the magnitude and sign of magnetic exchange in hydroxo-bridged Cu II dimers was shown to 20 be dependent on the Cu-O-Cu bridging angle, 2 while in complexes containing the [Cr III (OH)] 2 core the dominant structural factor was the variation of the angle between the O-H vector and the Cr 2 O 2 plane. 3 While more recent papers in molecular magnetism have concentrated on sub-topics such as 25 (amongst others) single-molecule magnetism, 4 quantum information processing 5 and magnetic cooling, 6 they still all fundamentally rely on a detailed understanding and exploitation of the structure-property relationship. However as these early studies showed, this is not a trivial process and it becomes 30 increasingly more difficult as the molecules increase in size, since the number of contributions to the exchange increases -this is particularly true for the 'giant' cluster compounds that have emerged in recent years containing tens, if not hundreds, of metal centres.…”

High-Spin Chains and Crowns from Double-Exchange Mechanism

“…The invoked reason for this ferromagnetic interaction is the delocalization of the copper unpaired electron into the unoccupied Gd 6s orbital, which forces all the unpaired electrons to align their spin according to Hund's rule. Ferromagnetism can also be imposed by symmetry, i.e., the magnetic orbitals of nearest neighbor metal ions are orthogonal (or close to be) [4][5][6][7][8]. As a consequence, there is no kinetic exchange and the only contributions to the exchange coupling are the direct exchange, which is always ferromagnetic, and the spin polarization, which may be either positive or negative.…”