Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Main Authors: Vadim A. Soloshonok, José Luis Aceña, Hisanori Ueki, Jianlin Han
• Format: Article
• Language: English
• Published: Beilstein-Institut 2012-11-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: axial chirality; central chirality; chiral switches; coordination bonds; functional materials; helical chirality; modular structural design; molecular devices
• Online Access: https://doi.org/10.3762/bjoc.8.223
• ISSN: 1860-5397

We describe herein the design and synthesis of asymmetric, pentadentate ligands, which are able to coordinate to Ni(II) cations leading to quasi-diastereomeric complexes displaying two new elements of chirality: stereogenic axis and helix along with configurational stabilization of the stereogenic center on the nitrogen. Due to the stereocongested structural characteristics of the corresponding Ni(II) complexes, the formation of quasi-diastereomeric products is highly stereoselective providing formation of only two, (Ra*,Mh*,Rc*) and (Ra*,Ph*,Rc*), out of the four possible stereochemical combinations. The reversible quasi-diastereomeric transformation between the products (Ra*,Mh*,Rc*) and (Ra*,Ph*,Rc*) occurs by intramolecular trans-coordination of Ni–NH and Ni–O bonds providing a basis for a chiral switch model.