A dinuclear cobalt(ii) complex of calix[8]arenes exibiting strong magnetic anisotropy

Sarah Petit, Guillaume Pilet, Dominique Luneau, Liviu F. Chibotaru, Liviu Ungur
2007 Dalton Transactions  
The solvothermal reaction of cobalt(II) acetate with p-tert-butylcalix [8] arene (calix) and triethylamine affords the compound (Et 3 NH) 2 [Co II 2 (calix) 2 ] (1·2Et 3 NH) that shows a hydrogen bond bridged dinuclear complex [Co II 2 (calix) 2 ] 2− (1) with cobalt(II) ions in a tetrahedral geometry. The compound crystallises in the monoclinic, space group P2 1 /n with cell parameters a = 14.89(1) Å , b = 20.90(2) Å , c = 30.87(4) Å , b = 102.57(7) • , V = 9376(16) Å 3 , Z = 2. The magnetic
more » ... 2. The magnetic studies together with ab initio calculations are evidence of an important role of the geometry of the second coordination sphere of carbon and hydrogen atoms around the CoO 4 core in quantifying the zero field splitting on cobalt sites. This results in strong magnetic anisotropies with a negative axial component on the cobalt fragments. Results and discussion The compound (1·2Et 3 NH) was obtained in the form of blue single crystals by solvothermal synthesis in methanol when reacting Co II acetate with p-tert-butylcalix[8]arene (calix) and triethylamine. Description of the structure of (Et 3 NH) 2 [Co II 2 (calix) 2 ] (1·2Et 3 NH) The crystal structure of the compound, was established from single crystal X-ray diffraction. It exhibits a centrosymmetrical anionic complex entity [Co II 2 (calix) 2 ] 2− (1) formed by two cobalt(II) ions coordinated to two calix[8]arene ligands (Fig. 1a) . The electronic neutrality of the compound is assumed by two triethylamonium cations (or Et 4 N + , depending on the base used during the synthesis). These cations are located on both sides of the complex in close vicinity of the non deprotonated and non coordinated 4582 | Dalton Trans., 2007, 4582-4588 This journal is
doi:10.1039/b708926k pmid:17928916 fatcat:tusbik65w5empjfqpixqpb7zea