MS36-P22 Using pressure to enhance the magnetic exchange interactions within Cr(III) dimers Helen Duncan (School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom) Simon Parsons (School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom) Euan Brechin (School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom) Gopalan Rajaraman (Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, India) Hector Fraser (School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom)email: h.duncan@ed.ac.ukWe have investigated a large series of Cr(III) dimer complexes with general formula [Cr2(Me-deaH)2(O2CR)Cl2]2. In these materials, magnetic properties are determined by highly deformable intermolecular interactions. The carboxylate above the Cr2 moiety distorts the planarity of the [Cr2O2] unit, promoting a net ferromagnetic exchange between the metals.

Through substitution of R with eight organic groups, and DFT calculations the key structural contributions to the net exchange, which has both anti- and ferromagnetic contributions, have been identified. The key contributions are the out of plane angle, θ, the Cr—O—Cr angle, φ, and the distortion of the planarity of the [Cr2O2] unit, ψ (Figure 1a, b, c respectively). [1]

We now use pressure to drive these structural transformations in three dimers where R = Me (acetate), tBu (pivalate) and Ph (benzoate); a method which has previously successfully been used to enhance the magnetic exchange in Re(IV) molecular magnets. [2] Through applications of pressures up to 4.6 GPa, we have increased θ by up to 5.1(6) ° and ψ by up to 1.4(2) °, (Figure 1d) which was predicted to increase the ferromagnetic contribution and decreased φ by up to 2.0(4) ° which was predicted to increase the antiferromagnetic contribution.

Considering both the pressure-induced structural deformations, and the ambient pressure DFT we have predicted the optimum pressures to enhance the ferromagnetic exchange in these dimers, and compared the predictions against high-pressure magnetic susceptibility measurements.

 
References:

[1] Fraser, H. W. L. et al. (2018). In preparation

[2] Woodall, C. H. et al. (2016). Nat. Commun, 7, doi:10.1038/ncomms13870

Keywords: High-pressure, Magnetism, Chromium