Elucidating the superexchange mechanisms in magnetic coordination polymer [Co(HCOO)₂(H2O)₂]_∞ through chemical bonding analysis

TY - JOUR

T1 - Elucidating the superexchange mechanisms in magnetic coordination polymer [Co(HCOO)2(H2O)2]∞ through chemical bonding analysis

AU - Grønbech, Thomas Bjørn Egede

AU - Krause, Lennard

AU - Ceresoli, Davide

AU - Iversen, Bo Brummerstedt

PY - 2023/10

Y1 - 2023/10

N2 - Below 5 K the Co(ii) formate dihydrate (Co-formate) coordination polymer, [Co(HCOO) 2(H 2O) 2] ∞, obtains an antiferromagnetic planar structure intercalated by paramagnetic Co ions. Structurally, the magnetic planes are composed of Co(1)-sites coordinated to six formate ligands, whereas the paramagnetic Co(2) ions coordinated to two formate ligands and four water molecules do not exhibit a two-dimensional magnetic correlation. Signs of short-range ferromagnetic interaction between the magnetic planes and paramagnetic ions have been observed upon further cooling. Here we study the electron density and chemical bonding in the Co-formate system through single crystal synchrotron X-ray diffraction measurements at 25 K. Derived Laplacian maps indicate that the formate ligands can interact with the Co(1) d-orbitals of t 2g-symmetry through a π-symmetric interaction. This opens up the possibility of superexchange facilitated via π-symmetric interactions in addition to σ-symmetric interactions across the delocalised formate electron system. Application of superexchange symmetry rules in concert with the experimental d-orbital populations obtained from the experimental electron density allow for a mechanistic description of the antiferromagnetic two-dimensional structure as well as the short-range ferromagnetic interactions, where the former is facilitated by σ-symmetric interactions and the latter by π-symmetric interactions.

AB - Below 5 K the Co(ii) formate dihydrate (Co-formate) coordination polymer, [Co(HCOO) 2(H 2O) 2] ∞, obtains an antiferromagnetic planar structure intercalated by paramagnetic Co ions. Structurally, the magnetic planes are composed of Co(1)-sites coordinated to six formate ligands, whereas the paramagnetic Co(2) ions coordinated to two formate ligands and four water molecules do not exhibit a two-dimensional magnetic correlation. Signs of short-range ferromagnetic interaction between the magnetic planes and paramagnetic ions have been observed upon further cooling. Here we study the electron density and chemical bonding in the Co-formate system through single crystal synchrotron X-ray diffraction measurements at 25 K. Derived Laplacian maps indicate that the formate ligands can interact with the Co(1) d-orbitals of t 2g-symmetry through a π-symmetric interaction. This opens up the possibility of superexchange facilitated via π-symmetric interactions in addition to σ-symmetric interactions across the delocalised formate electron system. Application of superexchange symmetry rules in concert with the experimental d-orbital populations obtained from the experimental electron density allow for a mechanistic description of the antiferromagnetic two-dimensional structure as well as the short-range ferromagnetic interactions, where the former is facilitated by σ-symmetric interactions and the latter by π-symmetric interactions.

U2 - 10.1039/D3TC01191G

DO - 10.1039/D3TC01191G

M3 - Journal article

SN - 2050-7526

VL - 11

SP - 12922

EP - 12932

JO - Journal of Materials Chemistry C

JF - Journal of Materials Chemistry C

IS - 38

ER -