Slow magnetic relaxation in octahedral low-spin Ni(iii) complexesElectronic supplementary information (ESI) available: Details of complex syntheses and spectroscopic characterizations, structural and magnetic data, and results of electronic structure calculations, including computed atomic coordinates and animations of key vibrational modes. CCDC 1579276, 1579279-1579281. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04482h

• Main Authors: Bhowmick, Indrani, Roehl, Andrew J, Neilson, James R, Rappé, Anthony K, Shores, Matthew P
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c7sc04482h

Herein we report the first examples of single-molecule magnet (SMM) behaviour in S = 1/2 Ni( iii ) complexes. We find that low-spin 3d 7 trans -[Ni III (cyclam)(X) 2 ]Y complexes (cyclam = 1,4,8,11-tetraazacyclotetradecane; X and Y are singly charged anions) exhibit field-induced slow relaxation of magnetization for O-donor axial ligands (nitrate) but not for N-donor variants (isothiocyanate). Experimental and electronic structure computational investigations indicate that intrinsic spin polarisation of low-spin Ni( iii ) is modulated significantly by local coordination geometry and supramolecular interactions. Solid state dilution of Ni( iii ) with diamagnetic Co( iii ) ions forms a related complex salt, [Ni x Co 1− x (cyclam)(NO 3 ) 2 ](NO 3 )·2HNO 3 (0.1 < x < 1), which preserves slow magnetic dynamics, thus supporting a molecular component to slow relaxation. An initial analysis of magnetic relaxation lifetime fits best to a combination of Raman and direct relaxation processes. Low-spin ( S = 1/2) Ni( iii ) cyclam complex salts can show SMM-type properties depending on the axial ligand donor atom identity.