Crystallometrics: a proficient multivariate approach for modelling and prediction of metal complexes properties in the solid state Lorenzo Marchi 1 , Serena Maria Fantasia, 2 Marina Cocchi, 1 Luca Rigamonti 1 Università degli studi di Modena e Reggio Emilia, Italy, 2 F. Hoffmann-La Roche Ltd, Switzerland Iron(II) and cobalt(II) complexes of general formula [M(bpp-R) 2 ](X) 2 ×solv with R-substituted bis -pyrazolilpyridyl (bpp-R) ligands (M = Fe, Co; X − = anion; solv = co-crystallized solvent) possess magnetic properties of interest. Iron(II) derivatives have been deeply studied for their ability to undergo spin transition from high spin ( S = 2, HS) to low spin ( S = 0, LS) state, showing the spin crossover (SCO) phenomenon. 1,2 Cobalt(II) compounds, much less studied, can behave as single-molecule magnets (SMMs) with consequent slow relaxation of the magnetization at low temperature. 3 Thanks to the fact that HS iron(II) complexes can be isostructural to the analogue cobalt(II) complexes, 2,3 it is possible to take advantage of the structural data available on iron(II) derivatives for harnessing non-covalent interactions and use the extracted information for the synthesis of new cobalt(II) complexes with desired modulated structures. The intermolecular interactions and the crystal packing among the substituent R of the bpp ligands, the anion X − and the co-crystallized solvent, if present, which govern the distortion of the octahedral coordination environment around the metal centre and hence their magnetic behaviour, are here studied with an innovative multivariate approach through the help of chemometrics tools. At first, an exploratory Principal Component Analysis (PCA) was conducted using coordination bond distances, angles and selected torsional angles of the available X-ray structures of HS iron(II) complexes as probes of the intermolecular contacts in the solid state. This leads to a model able to distinguish among the SCO complexes and the HS-blocked ones, justifying the validity of our multivariate approach to study non-covalent interactions in the solid state. 4 In this model cobalt(II) known structures were projected, finding a close-fitting connection with the corresponding iron(II) structure. This points out which new cobalt complexes should be synthetically pursued to explore the PCA space and the most diverse complexes. This general chemometrics approach can be easily extended to other complexes and other properties such as catalysis. References
1. M. Halcrow et al., Inorg. Chem. , 2019, 58 (15), 9811–9821. 2. N. Bridonneau et al., Dalton Trans. , 2017, 46 (12), 4075– 4085. 3. L. Rigamonti et al., Chem. Eur. J. , 2018, 24 (35), 8857–8868. 4. L. Marchi et al., Inorg. Chem. Front. , 2023, submitted .
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© The Author(s), 2023
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