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oai:figshare.com:article/34033741 2026-09-30T16:07:19Z category_1 category_4 category_915 category_7 category_12 category_14 category_21 category_873 category_39 portal_63 item_type_6 month_year_09_2026

Quantifying Chemical Differences of Cl^– and Br^– Ligands: A Comparative X‑ray Electron Density Study of Two Isostructural Co(II) Single Molecule Magnets Frej S. Rattenborg (25144816) Sofie S. Leiszner (25144819) Hannah H. Slavensky (25144822) Ivan Šalitroš (1612372) Bo Brummerstedt Iversen (1288860) Biophysics Biochemistry Physical Sciences not elsewhere classified Medicine Cell Biology Molecular Biology Biotechnology Chemical Sciences not elsewhere classified Ecology yl )- pyridine typical structural entities subsequent multipole modeling single molecule magnets similar electron density orbital populations reveal bond critical points quantifying chemical differences equatorial cl compared sup >–</ sup two isostructural co ></ sub >, ></ sub >) 1 </ b 2 </ b differences affect chemical bonding ></ sub >< sup z </ yz </ xz </ xy </ x </ vice versa topological analysis sub >< The magnetic properties of single molecule magnets (SMMs) relate to details of the metal–ligand chemical bonding. Halide ligands are typical structural entities in SMMs and are often interchanged assuming chemical transferability. However, the chemical bonding of the halides is different, and it is of high interest to understand how these differences affect the properties of SMMs. Here, two isostructural pentacoordinate cobalt complexes, [Co(L)Cl₂] (<b>1</b>) and [Co(L)Br₂] (<b>2</b>) with L = 2,6-bis(1-dodecyl-1<i>H</i>-benzimidazol-2-yl)-pyridine, are investigated through 25 K single crystal synchrotron X-ray diffraction (XRD) measurements with subsequent multipole modeling to derive experimental electron densities. Topological analysis of the electron densities reveal closed-shell interactions between Co and the halides and the nitrogen donors of L. The Co–Cl bonding resembles the Co–N bonds, with very similar electron density and Laplacian in the bond critical points, while the Co–Br bonding is weaker and more ionic. Estimated experimental d-orbital populations reveal an ordering of (d_<i>xy</i>,d_<i>xz</i>) < d_<i>z</i>² < d_<i>yz</i> < d_{<i>x</i>²–<i>y</i>²} for <b>1</b> and d_<i>xy</i> < d_<i>xz</i> < d_{<i>x</i>²–<i>y</i>²} < d_<i>yz</i> < d_<i>z</i>² for <b>2</b>. The reversal of d_<i>z</i>² and d_{<i>x</i>²–<i>y</i>²} between <b>1</b> and <b>2</b> reflects a stronger interaction from Co to the equatorial Cl compared to the axial Cl in <b>1</b>, but vice versa in <b>2</b>. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.inorgchem.6c02288.s001 https://figshare.com/articles/journal_contribution/Quantifying_Chemical_Differences_of_Cl_sup_sup_and_Br_sup_sup_Ligands_A_Comparative_X_ray_Electron_Density_Study_of_Two_Isostructural_Co_II_Single_Molecule_Magnets/34033741 CC BY-NC 4.0