Gransbury Gemma K, Corner Sophie C, Kragskow Jon G C, Evans Peter, Yeung Hing Man, Blackmore William J A, Whitehead George F S, Vitorica-Yrezabal Iñigo J, Oakley Meagan S, Chilton Nicholas F, Mills David P
Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
J Am Chem Soc. 2023 Oct 18;145(41):22814-22825. doi: 10.1021/jacs.3c08841. Epub 2023 Oct 5.
Isolated dysprosocenium cations, [Dy(Cp)] (Cp = substituted cyclopentadienyl), have recently been shown to exhibit superior single-molecule magnet (SMM) properties over closely related complexes with equatorially bound ligands. However, gauging the crossover point at which the Cp substituents are large enough to prevent equatorial ligand binding, but small enough to approach the metal closely and generate strong crystal field splitting has required laborious synthetic optimization. We therefore created the computer program AtomAccess to predict the accessibility of a metal binding site and its ability to accommodate additional ligands. Here, we apply AtomAccess to identify the crossover point for equatorial coordination in [Dy(Cp)] cations in silico and hence predict a cation that is at the cusp of stability without equatorial interactions, viz., [Dy(Cp)(Cp*)] (Cp = CHBu-1,2,4, Cp* = CMe). Upon synthesizing this cation, we found that it crystallizes as either a contact ion-pair, [Dy(Cp)(Cp*){Al[OC(CF)]-κ-F}], or separated ion-pair polymorph, [Dy(Cp)(Cp*)][Al{OC(CF)}]·CH. Upon characterizing these complexes, together with their precursors, yttrium and yttrium-doped analogues, we find that the contact ion-pair shows inferior SMM properties to the separated ion-pair, as expected, due to faster Raman and quantum tunneling of magnetization relaxation processes, while the Orbach region is relatively unaffected. The experimental verification of the predicted crossover point for equatorial coordination in this work tests the limitations of the use of AtomAccess as a predictive tool and also indicates that the application of this type of program shows considerable potential to boost efficiency in exploratory synthetic chemistry.
最近研究表明，孤立的镝阳离子[Dy(Cp)]（Cp = 取代环戊二烯基）相较于具有赤道配位配体的密切相关配合物，展现出更优异的单分子磁体（SMM）性质。然而，要确定Cp取代基大到足以阻止赤道配位配体结合，但又小到足以接近金属并产生强晶体场分裂的交叉点，需要进行繁琐的合成优化。因此，我们开发了计算机程序AtomAccess，以预测金属结合位点的可及性及其容纳额外配体的能力。在此，我们应用AtomAccess在计算机模拟中确定[Dy(Cp)]阳离子赤道配位的交叉点，从而预测一种在没有赤道相互作用时处于稳定性临界点的阳离子，即[Dy(Cp)(Cp*)]（Cp = CHBu-1,2,4，Cp* = CMe）。合成该阳离子后发现，它结晶为接触离子对[Dy(Cp)(Cp*){Al[OC(CF)]-κ-F}]或分离离子对多晶型物[Dy(Cp)(Cp*)][Al{OC(CF)}]·CH。对这些配合物及其前体、钇和掺钇类似物进行表征后，我们发现，正如预期的那样，接触离子对的SMM性质不如分离离子对，这是由于拉曼散射和磁化弛豫过程的量子隧穿更快，而奥巴赫区域相对不受影响。这项工作中对预测的赤道配位交叉点的实验验证，检验了AtomAccess作为预测工具的局限性，同时也表明这类程序的应用在提高探索性合成化学效率方面具有巨大潜力。
