From Mesocates to Helicates: Structural, Magnetic and Chiro‐Optical Studies on Nickel(II) Supramolecular Assemblies Derived from Tetradentate Schiff Bases. Issue 30 (27th April 2018)

• Record Type: Journal Article
• Authors: Mayans, Júlia; Font‐Bardia, Mercè; Di Bari, Lorenzo; Arrico, Lorenzo; Zinna, Francesco; Pescitelli, Gennaro; Escuer, Albert
• Is Part Of: Chemistry. Volume 24:Issue 30(2018)
• Page Start: 7653
• Page End: 7663
• Publication Date: 2018-04-27
• Subjects: chirality -- circular dichroism -- solid-state structures -- helicate -- mesocate -- nickel; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201800323
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The systematic reactions of a family of tetradentate pyridyl/imine and quinolyl/imine racemic or enantiopure Schiff bases with Ni(NO3 )2 or Ni(ClO4 )2 in the presence of sodium azide yielded, as a function of the starting racemic, chiral or achiral base, a set of chiral, meso or achiral complexes. In all cases, the compounds consist of two Ni II cations linked by a double azido bridge in its end‐on coordination mode. All the dimers exhibit a mesocate supramolecular structure and one of them, the unprecedented mix of helicate and mesocate in 2:1 ratio. The transition from mesocate to helicate conformation has been reached by tuning the flexibility of the central spacers of the Schiff bases and the size of the substituents. Electronic circular dichroism (ECD) studies have been performed for two pairs of enantiomers and interpreted by means of DFT calculations. Susceptibility measurements show a ferromagnetic coupling between the Ni II cations mediated by the end‐on azido bridges. Abstract : A chiral sleight of hand : The transition from mesocate to helicate conformations in a series of dinuclear nickel(II) complexes has been reached by tailoring the flexibility and size of the ligands (see figure). Chiral mesocates have been achieved.