| Autor: |
Chattopadhyay K; Department of Chemistry , Indian Institute of Technology Kharagpur , Kharagpur 721 302 , India.; School of Chemical Sciences , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India., Heras Ojea MJ; WestCHEM, School of Chemistry , University of Glasgow , University Avenue , Glasgow G12 8QQ , U.K., Sarkar A; Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400 076 , India., Murrie M; WestCHEM, School of Chemistry , University of Glasgow , University Avenue , Glasgow G12 8QQ , U.K., Rajaraman G; Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400 076 , India., Ray D; Department of Chemistry , Indian Institute of Technology Kharagpur , Kharagpur 721 302 , India. |
| Abstrakt: |
A systematic one-step one-pot multicomponent reaction of Co(ClO 4 ) 2 ·6H 2 O, H 3 L (2,6-bis((2-(2-hydroxyethylamino)ethylimino)methyl)-4-methylphenol), and readily available carboxylate salts (RCO 2 Na; R = CH 3 , C 2 H 5 ) resulted in the two structurally novel coordination aggregates [Co II Co III 4 L 2 (μ 1,3 -O 2 CCH 3 ) 2 (μ-OH) 2 ](ClO 4 ) 4 ·4H 2 O (1) and [Co II Co III 4 L 2 (μ 1,3 -O 2 CC 2 H 5 ) 2 (μ-OH)(μ-OMe)](ClO 4 ) 4 ·5H 2 O (2). At room temperature, reactions of H 3 L in MeOH with cobalt(II) perchlorate salts led to coassembly of initially formed ligand-bound {Co II 2 } fragments following aerial oxidation of metal centers and bridging by in situ generated hydroxido/alkoxido groups and added carboxylate anions. Available alkoxido arms of the initially formed {L(μ 1,3 -O 2 CCH 3 )(μ-OH/OMe)Co 2 } + fragments were utilized to trap a central Co II ion during the formation of [Co 5 ] aggregates. In the solid state, both complexes have been characterized by X-ray crystallography, variable-temperature magnetic measurements, and theoretical studies. Both 1 and 2 show field-induced slow magnetic relaxation that arises from the single pseudo- T d Co II ion present. The structural distortion leads to an easy-axis magnetic anisotropy ( D = -31.31 cm -1 for 1 and -21.88 cm -1 for 2) and a small but non-negligible transverse component ( E/ D = 0.11 for 1 and 0.08 for 2). The theoretical studies also reveal how the O-Co-O bond angles and the interplanar angles control D and E values in 1 and 2. The presence of two diamagnetic {Co 2 (μ-L)} hosts controls the distortion of the central {CoO 4 } unit, highlighting a strategy to control single-ion magnetic anisotropy by trapping single ions within a diamagnetic coordination environment. |
