title: Influence of peripheral substitution on the magnetic behavior of single-ion magnets based on homo- and heteroleptic Tb(III) bis(phthalocyaninate).
abstract: A series of homoleptic ([Tb(III)(Pc)(2) ]) and heteroleptic ([Tb(III)(Pc)(Pc')]) Tb(III) bis(phthalocyaninate) complexes that contain different peripheral substitution patterns (i.e., tert-butyl or tert-butylphenoxy groups) have been synthesized in their neutral radical forms and then reduced into their corresponding anionic forms as stable tetramethylammonium/tetrabutylammonium salts. All of these compounds were spectroscopically characterized and their magnetic susceptibility properties were investigated. As a general trend, the radical forms exhibited larger energy barriers for spin reversal than their corresponding reduced compounds. Remarkably, heteroleptic complexes that contain electron-donor moieties on one of the two Pc ligands show higher effective barriers and blocking temperatures than their homoleptic derivatives. This result is assigned to the elongation of the N-Tb distances in the substituted macrocycle, which brings the terbium(III) ion closer to the unsubstituted Pc, thus enhancing the ligand-field effect. In particular, heteroleptic [Tb(III) (Pc)(Pc')] complex 4, which contains one octa(tert-butylphenoxy)-substituted Pc ring and one bare Pc ring, exhibits the highest effective barrier and blocking temperature for a single-molecule magnet reported to date.
authors.affiliation: Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Carolina R
authors.initials: CR
authors.lastname: Ganivet
authors.forename: Beatriz
authors.initials: B
authors.lastname: Ballesteros
authors.forename: Gema
authors.initials: G
authors.lastname: de la Torre
authors.forename: Juan M
authors.initials: JM
authors.lastname: Clemente-Juan
authors.forename: Eugenio
authors.initials: E
authors.lastname: Coronado
authors.forename: Tomás
authors.initials: T
authors.lastname: Torres