resumo
The design of molecule-based systems with tuneable optical and/or magnetic properties has attracted considerable attention because of their potential applications in high-performance molecule-based electronic devices, switches, sensors and displays. In this regard, a large number of valence tautomeric tetraoxolene-bridged dinuclear cobalt complexes with tetradentate ancillary ligands have been reported, but none of these complexes contained a bidentate terminal ligand. In order to increase the scope in this field, the present report describes the synthesis, structures, electrochemical and magnetic studies of two dinuclear cobalt-tetraoxolene complexes, [Co-2(dhbq)(bpy)(4)](PF6)(3) (1(PF6)(3)) and [Co-2(dhbq)(bpa)(4)] (PF6)(3)center dot 6H(2)O (2(PF6)(3)center dot 6H(2)O), where H(2)dhbq is 2,5-dihydroxy-1,4-benzoquinone, with the bidentate terminal ligands 2,2'-bipyridine (bpy) and 2,2'-bipyridyl amine (bpa), respectively. An X-ray diffraction study reveals that the dianionic form of the redox active tetraoxolene ligand bridges the metal centers in these complexes, and one metal center is in the high spin cobalt(II) state while the other one is in the low spin cobalt(III) state. The present report will increase knowledge on the synthesis of such systems using bidentate terminal ligands. Variable temperature magnetic susceptibility measurements show no indication for valence tautomerism (VT) in either complex. Further attempts could be made to synthesize similar complexes from different solvents and/or using different counter ions to check whether such variations can bring VT in these systems. (C) 2018 Elsevier Ltd. All rights reserved.
palavras-chave
INTRAMOLECULAR ELECTRON-TRANSFER; VALENCE TAUTOMERIC TRANSITIONS; SPIN-CROSSOVER; MOLECULAR SPINTRONICS; THERMAL HYSTERESIS; ROOM-TEMPERATURE; METAL-COMPLEXES; IRON COMPLEXES; MIXED-VALENCE; TRIS(2-PYRIDYLMETHYL)AMINE
categoria
Chemistry; Crystallography
autores
Jana, NC; Brandao, P; Mathoniere, C; Panja, A
nossos autores
Paula Cristina Ferreira da Silva Brandão
Investigador Auxiliaragradecimentos
A.P. would like to thank the Department of Science and Technology (DST), New Delhi under the FAST Track Scheme (Order No. SB/FT/CS-016/2012, dated 20/12/2013) for financial support. CM would like to thank to the University of Bordeaux, the CNRS and the Region Aquitaine for funding.