Ferromagnetic coupling in d1–d3 linear oxido-bridged heterometallic complexes: ground-state models of metal-to-metal charge transfer excited states. Issue 43 (15th October 2015)

• Record Type: Journal Article
• Authors: Huang, Tao; Wu, Xinyuan; Song, Xiao; Xu, Hao; Smirnova, Tatyana I.; Weare, Walter W.; Sommer, Roger D.
• Is Part Of: Dalton transactions. Volume 44:Issue 43(2015)
• Page Start: 18937
• Page End: 18944
• Publication Date: 2015-10-15
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt02719e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Linear heterobimetallic oxido-bridged d 1 –d 3 compounds are described which are proposed as models for magnetic coupling of MMCT excited states. Abstract : Convenient strategies have been developed to synthesize heterobi/trimetallic oxido complexes containing V(iv )–O–Cr(iii ), V(iv )–O–Cr(iii )–O–Ti(iv ) and V(iv )–O–Cr(iii )–O–V(iv ) cores. These compounds can serve as ground state models for probing the magnetic properties of metal-to-metal charge transfer excited states. Each of these complexes represents the first experimental demonstration of ferromagnetic coupling in a d 1 –d 3 oxido bridged compound, which confirms a long standing theoretical prediction for such a linkage. Structural characterization reveals a similar structure for each of the bi/trimetallic complexes with identical VO bond lengths (∼1.644 Å) and a linear V–O–Cr geometry. The Cr–O distances (1.943–1.964 Å) are significantly influenced by the ligands in the trans axial positions. Ferromagnetic coupling between the V(iv ) and Cr(iii ) of V–O–Cr is measured by temperature-dependent magnetic susceptibility, showing J = +42.5 to +50.7 cm −1 ( H = −2 JŜ V Ŝ Cr ). This is further supported by variable temperature X-band EPR. The values of J are found to be consistent with the function J = Ae βr ( A = 9.221 × 10 8 and β = 8.607 Å −1 ), where r is the Cr–O bond distance. We propose a model that links either ferromagnetic or antiferromagentic exchange coupling with long excited state lifetimes in metal-to-metal charge transfer (MMCT) chromophores.