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Coordination‐Induced Spin‐State Switching with Nickel(II) salpn Complexes: Electronic versus Steric Effects and Influence of Intermolecular Interactions
Author(s) -
Brandenburg Hannah,
Krahmer Jan,
Fischer Kim,
Schwager Bettina,
Flöser Benedikt,
Näther Christian,
Tuczek Felix
Publication year - 2018
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201701281
Subject(s) - chemistry , nickel , steric effects , porphyrin , pyridine , coordination complex , intermolecular force , crystallography , stacking , spectroscopy , titration , coordination sphere , photochemistry , stereochemistry , inorganic chemistry , crystal structure , molecule , metal , organic chemistry , physics , quantum mechanics
Four nickel(II) salpn (salicylidenepropylene iminate) complexes are investigated concerning their capability to perform CISSS (coordination‐induced spin‐state switching). To this end, pyridine titration experiments are performed with the nickel salpn complexes [Ni(salpn)], [Ni(salpn t BuCF 3 )], [Ni(salpnCF 3 )] and [Ni(salpnSbenz)]. The electronic‐structural changes are monitored by UV/Vis spectroscopy and Evans NMR spectroscopy. Association constants ( K 1s and K 2 ), as well as thermodynamic parameters (Δ H , Δ S , and Δ G ), for the binding of pyridine are determined. In comparison with porphyrins and porphyrin‐derived systems investigated earlier, the salpn systems exhibit quite different coordination properties. In particular, the fluorinated systems show the formation of dimers due to CH–π and π–π stacking. On the other hand, the investigated compounds coordinate axial ligands with affinities comparable with those of the porphyrin‐based analogs. This renders them eligible for the preparation of LD‐CISSS (light‐driven CISSS) systems, which, in turn, may be applied as functional MRI contrast agents.