Ligand field and intermolecular interactions tuning the magnetic properties of spin-crossover Fe(II) polymer with 4,4′-bipyridine

●A new member of Fe(||)-4,4′-bipy family has been prepared.●It displays half spin transitions tuned by ligand field and intermolecular interactions.●We have made a detailed comparison of this new member with two other analogous complexes.

A new spin crossover coordination polymer (SCO-CPs) of Fe(II)-4,4′-bipyridine (4,4′-bipy) family: {Fe(4,4′-bipy)2(H2O)2}·(4,4′-bipy)· 8(H2O)·2(ClO4) (3), which displays half spin transitions between 100 and 300 K, has been synthesized and structurally characterized. Compound 3 featured with two-dimensional (2-D) grids connected by hydrogen bonds and π…π packing between one-dimensional (1-D) chains, the 2-D grids expand to three-dimensional (3-D) architecture supported by a “S-shaped holder” involving lattice 4-4′-bipy, water molecules and perchlorate anion. We compared 3 with the other two analogous complexes: ({Fe(4,4′-bipy) (H2O)2 (NCS)2}·4,4′-bipy, 1 and {Fe(4,4′-bipy)2(NCS)2}·mSolv, 2) through Hirshfeld surfaces analysis, which revealed that the low ligand field strength (NCS−) and lone-pair…H contacts contribute to the stabilization of HS (high-spin) state of the Fe(II) ion, while the high ligand field strength (4,4′-bipy) and strong intermolecular contacts (hydrogen bonds and π…π packing interactions) make for the LS (low-spin) state.

Figure optionsDownload as PowerPoint slide