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Mecanismo de acoplamiento ferromagnético en los complejos de cobre (II) - gadolinio (III)
Jozef Paulovic1, Fanica Cimpoesu, Marilena Ferbinteanu
1Department of Applied Chemistry, School of Engineering University of Tokyo, Tokyo, Japan.
Journal of the American Chemical Society
|March 12, 2004
Resumen
Los cálculos químicos cuánticos de última generación revelan el mecanismo detrás del acoplamiento ferromagnético en los complejos de cobre-gadolinio. El acoplamiento ferromagnético se observa generalmente debido a las interacciones electrónicas específicas y la simetría pseudo-C.
Área de la Ciencia:
- Química cuántica es la química cuántica.
- Ciencia de los materiales Ciencia de los materiales.
- Magnetoquímica es la Magnetoquímica.
Sus antecedentes:
- Los complejos de cobre-gadolinio son conocidos por su acoplamiento ferromagnético.
- Comprender los mecanismos electrónicos subyacentes es crucial para el diseño de nuevos materiales magnéticos.
Objetivo del estudio:
- Investigar el acoplamiento ferromagnético casi general en complejos de cobre-gadolinio utilizando cálculos químicos cuánticos avanzados.
- Para dilucidar las vías electrónicas responsables de las interacciones ferromagnéticas.
Principales métodos:
- Cálculos químicos cuánticos de última generación que incluyen el campo autoconsistente de espacio activo completo (CASSCF), CAS apoyado por la teoría de la perturbación de segundo orden (CASPT2) y CASPT2 de varios estados (MS-CASPT2).
- Modelos analíticos y optimización de la geometría para la simetría C.
- Procedimientos de cálculo no estándar para hacer frente a las configuraciones de suelo no-aufbau.
Principales resultados:
- Las constantes de acoplamiento magnético calculadas reproducen con precisión los valores experimentales a nivel CASSCF.
- El mecanismo de Kahn que implica la transferencia de electrones de Cu(II) 3d a Gd(III) 5d orbitales, cuando se utilizan orbitales moleculares CASPT2, explica efectivamente el acoplamiento ferromagnético.
- Los efectos de polarización de espín sobre el ligando, que involucran un orbital atómico de tipo Gd(III) 5d, magnifican el acoplamiento ferromagnético, apoyando y refinando el mecanismo de Gatteschi.
- El acoplamiento ferromagnético es favorecido por la ortogonalidad orbital en la simetría C(2)(v), mientras que la asimetría molecular conduce a excepciones antiferromagnéticas.
Conclusiones:
- La generalidad del acoplamiento ferromagnético Cu (II) -Gd (III) se atribuye a la prevalencia de la geometría aproximada del pseudo-C (II) -Gd (v).
- Tanto los mecanismos de Kahn como los de Gatteschi contribuyen al acoplamiento ferromagnético y son interconvertibles.
- La simetría molecular juega un papel crítico en la determinación del tipo y la fuerza del acoplamiento magnético.
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