Origin of the unusual ground-state spin S = 9 in a Cr10single-molecule magnet

Rubín, J. (Universidad de Zaragoza) ; Arauzo, A. (Universidad de Zaragoza) ; Bartolomé, E. ; Sedona, F. ; Rancan, M. ; Armelao, L. ; Luzón, J. ; Guidi, T. ; Wilhelm, F. ; Rogalev, A. ; Amann, A. ; Spagna, S. ; Bartolomé, J. (Universidad de Zaragoza) ; Bartolomé, F.

Resumen: The molecular wheel Cr10(OMe)20(O2CCMe3)10], abbreviated {Cr10}, with an unusual intermediate total spin S = 9 and non-negligible cluster anisotropy, D/kB= -0.045(2) K, is a rare case among wheels based on an even number of 3d-metals, which usually present an antiferromagnetic (AF) ground state (S = 0). Herein, we unveil the origin of such a behavior. Angular magnetometry measurements performed on a single crystal confirmed the axial anisotropic behavior of {Cr10}. For powder samples, the temperature dependence of the susceptibility plotted as ¿T(T) showed an overall ferromagnetic (FM) behavior down to 1.8 K, whereas the magnetization curve M(H) did not saturate at the expected 30 µB/fu for 10 FM coupled 3/2 spin Cr3+ions, but to a much lower value, corresponding to S = 9. In addition, the X-ray magnetic circular dichroism (XMCD) measured at high magnetic field (170 kOe) and 7.5 K showed the polarization of the cluster moment up to 23 µB/fu. The magnetic results can be rationalized within a model, including the cluster anisotropy, in which the {Cr10} wheel is formed by two semiwheels, each with four Cr3+spins FM coupled (JFM/kB= 2.0 K), separated by two Cr3+ions AF coupled asymmetrically (J23/kB= J78/kB= -2.0 K; J34/kB= J89/kB= -0.25 K). Inelastic neutron scattering and heat capacity allowed us to confirm this model leading to the S = 9 ground state and first excited S = 8. Single-molecule magnet behavior with an activation energy of U/kB= 4.0(5) K in the absence of applied field was observed through ac susceptibility measurements down to 0.1 K. The intriguing magnetic behavior of {Cr10} arises from the detailed asymmetry in the molecule interactions produced by small-angle distortions in the angles of the Cr-O-Cr alkoxy bridges coupling the Cr3+ions, as demonstrated by ab initio and density functional theory calculations, while the cluster anisotropy can be correlated to the single-ion anisotropies calculated for each Cr3+ion in the wheel.

Idioma: Inglés

DOI: 10.1021/jacs.2c05453

Año: 2022

Publicado en: Journal of the American Chemical Society 144, 27 (2022), 12520-12535
ISSN: 0002-7863

Factor impacto JCR: 15.0 (2022)

Categ. JCR: CHEMISTRY, MULTIDISCIPLINARY rank: 17 / 178 = 0.096 (2022) - Q1 - T1

Factor impacto CITESCORE: 25.7 - Biochemistry, Genetics and Molecular Biology (Q1) - Chemistry (Q1) - Chemical Engineering (Q1)

Factor impacto SCIMAGO: 5.945 - Biochemistry (Q1) - Colloid and Surface Chemistry (Q1) - Chemistry (miscellaneous) (Q1) - Catalysis (Q1)

Financiación: info:eu-repo/grantAgreement/ES/DGA/E12-20R
Financiación: info:eu-repo/grantAgreement/ES/AEI/PID2020-115159GB-I00/AEI/10.13039/501100011033
Financiación: info:eu-repo/grantAgreement/ES/MINECO/MAT2017-83468-R

Tipo y forma: Artículo (PostPrint)

Área (Departamento): Área Cienc.Mater. Ingen.Metal. (Dpto. Ciencia Tecnol.Mater.Fl.)
Área (Departamento): Área Física Materia Condensada (Dpto. Física Materia Condensa.)