The Rational Design and Preparation of Cyanometalate-Based Single-Molecule Magnets

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The aim of the proposal is to combine the synthesis of novel single-molecule magnetic materials (SMMs) and their detailed characterization with the accurate prediction of the corresponding molecular and crystal structures, based on molecular modeling approaches, and with quantum-chemical methods, which will allow to reliably computing the crucial electronic parameters of SMMs on the basis of the optimized structures. This novel combined approach for a rational design of SMMs, followed by their preparation and characterization, is in sharp contrast to the usual serendipity-based developments in this area, and it relies on our long tradition to combine high-level theory with empirical modeling and experimental work. It is hoped that it will allow us to produce novel tailor-made materials for applications such as high density magnetic information storage. This project follows our earlier work on the detailed analysis of the electronic properties of a series of hexacyanometalate-based oligonuclear complexes with a combination of ligand field and DFT methods, and involving a vector coupling approach to thoroughly study larger systems. The experimental work was based on hexacyanometalates of Cr3+, Fe3+, Mn3+ and Co3+, which were used to form linear and bent cyano-bridged trinuclear complexes with the mononuclear [NiII(L)]2+ and [CuII(L)]2+ complexes (L is a penta- or tetradentate bispidine ligand) as terminal fragments. The preliminary theoretical studies have resulted in a set of rules for the synthesis of novel SMMs, and these have largely been confirmed by the experimental data. However, it became clear that subtle distortions of the complex geometries generally lead to a reduction of the magnetic anisotropy and a decrease of the blocking temperature. Therefore, there is a need to accurately predict the structural properties and, apart from the experimental work, this is one of the focal points of the present grant proposal.