Ludwig Jannis, Moje Tobias, Röhricht Fynn, Herges Rainer
Otto Diels Institute of Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel, Germany.
Beilstein J Org Chem. 2020 Oct 21;16:2589-2597. doi: 10.3762/bjoc.16.210. eCollection 2020.
We present the synthesis and the spin switching efficiencies of Ni(II)-porphyrins substituted with azopyridines as covalently attached photoswitchable ligands. The molecules are designed in such a way that the azopyridines coordinate to the Ni ion if the azo unit is in configuration. For steric reasons no intramolecular coordination is possible if the azopyridine unit adopts the configuration. Photoisomerization of the azo unit between and is achieved upon irradiation with 505 nm (→) and 435 nm (→). Concurrently with the isomerization and coordination/decoordination, the spin state of the Ni ion switches between singlet (low-spin) and triplet (high-spin). Previous studies have shown that the spin switching efficiency is strongly dependent on the solvent and on the substituent at the 4-position of the pyridine unit. We now introduced thiol, disulfide, thioethers, nitrile and carboxylic acid groups and investigated their spin switching efficiency.
我们展示了用偶氮吡啶作为共价连接的光开关配体取代的镍（II）-卟啉的合成及其自旋开关效率。这些分子的设计方式是，如果偶氮单元处于反式构型，偶氮吡啶就会与镍离子配位。由于空间位阻原因，如果偶氮吡啶单元采用顺式构型，则不可能发生分子内配位。在用505 nm（反式→顺式）和435 nm（顺式→反式）照射时，偶氮单元在反式和顺式之间实现光异构化。与异构化以及配位/去配位同时发生的是，镍离子的自旋态在单重态（低自旋）和三重态（高自旋）之间切换。先前的研究表明，自旋开关效率强烈依赖于溶剂以及吡啶单元4位上的取代基。我们现在引入了硫醇、二硫化物、硫醚、腈和羧酸基团，并研究了它们的自旋开关效率。
