Spin Crossover and Field‐Induced Single‐Molecule Magnet Behaviour in Co(II) Complexes Based on Terpyridine with Tetrathiafulvalene Analogues
Siham Tiaouinine, Jessica Flores González, Bertrand Lefeuvre, Thierry Guizouarn, Marie Cordier≈, Vincent Dorcet, Lakehmici Kaboub, Olivier Cador, Fabrice Pointillart
Abstract
Abstract Two new TTF‐based ligands involving terpyridine moiety (L 1 =4‐(4′‐Methyl‐phenyl‐2,2 : 6’,2’’‐terpyridine −4‐ylmethylthio)‐5‐(2‐cyanoethylthio)‐4′,5′‐bis(methylthio)tetrathiafulvene and L 2 =4‐(4′‐Methyl‐phenyl‐2,2 : 6’,2’’‐terpyridine −4‐ylmethylthio)‐5‐(2‐cyanoethylthio)‐4′,5′‐bis(propylthio)tetrathiafulvene) have been synthesized and seven related mononuclear complexes were isolated as single crystals. The 2 : 1 (ligand : metal) complexes of formula [Co(L 1 ) 2 ](NO 3 ) 2 ( 2 ) and [Co(L 1 ) 2 ](BF 4 ) 2 ( 3 ) displayed thermal spin crossover transition while the 1 : 1 complexes of formula [CoCl 2 ( L 1 )](DMF) 2 ( 4 ), [CoBr 2 (L 1 )] ⋅ (DMF) ( 5 ), [CoCl 2 ( L 2 )] ⋅ (DMF) ⋅ 0.5(Et 2 O) ( 6 ) and [CoBr 2 (L 2 )] ⋅ (DMF) ( 7 ) displayed slow magnetic relaxation through either Raman or Raman/Direct combination processes. A relationship between the structure and the nature of the magnetic relaxation processes is proposed.