Cyanide clusters of ReII with 3d metal ions and their magnetic properties: incorporating anisotropic ions into metal-cyanide clusters with high spin magnetic ground states

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Title: Cyanide clusters of ReII with 3d metal ions and their magnetic properties: incorporating anisotropic ions into metal-cyanide clusters with high spin magnetic ground states
Author: Schelter, Eric John
Abstract: Clusters of metal ions that possess large numbers of magnetically coupled unpaired electrons have attracted much interest in recent years due to their fascinating magnetic behavior . With an appreciable component of magnetic anisotropy , these large -spin paramagnetic molecules can exhibit an energy barrier to inversion of their magnetic dipole , leading to spontaneous magnetization and magnetic hysteresis below a critical temperature . Since this behavior is a property of an individual clusters rather than a collection of molecules , this phenomenon has been dubbed ? ?Single Molecule Magnetism ? ? . Our approach to the study of new high -spin systems has been to exert a measure of synthetic control in the preparation of clusters . Specifically we are employing highly anisotropic metal ions with the anticipation that these ions would engender large overall magnetic anisotropy in the resulting clusters . The first step in this process was the development of the chemistry of two new d5 ReII (S = ? ? ) complexes , namely [ReII (triphos ) (CH3CN )3][PF6]2 and [Et4N][ReII (triphos ) (CN )3] . The magnetic , optical and electrochemical properties were studied and theoretical models were developed to describe the origin of the large temperature independent paramagnetism that was observed . Next , we successfully employed transition metal cyanide chemistry using the ReII building blocks to prepare a family of isostructural , cubic clusters of the general formula {[MCl]4[Re (triphos ) (CN )3]4} M = Mn , Fe , Co , Ni , Cu , Zn whose 3d ions adopt local tetrahedral geometries . Within the clusters , magnetic exchange is observed between the paramagnetic ions , which has been modeled using an Ising exchange model to account for the dominating anisotropy of the ReII ion . Despite the high pseudo -symmetry of the clusters (Td ) , this work has yielded a rare example of a metal -cyanide single molecule magnet , {[MCl]4[Re (triphos ) (CN )3]4} with an S = 8 ground state , D = -0 .39 cm -1 and an effective energy barrier for magnetization reversal of Ueff = 8 .8 cm -1 . The elucidation of this family of isostructural clusters has also allowed us to pursue fundamental work on the structure /property relationships of the exotic , paramagnetic ReII ion . As the clusters are soluble , stable compounds , the future of this chemistry lies in the development of a true building -block approach to ? ?super -clusters ? ? that exhibit very high ground state spin values .
URI: http : / /hdl .handle .net /1969 .1 /2205
Date: 2005-08-29

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Cyanide clusters of ReII with 3d metal ions and their magnetic properties: incorporating anisotropic ions into metal-cyanide clusters with high spin magnetic ground states. Available electronically from http : / /hdl .handle .net /1969 .1 /2205 .

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