title: Giant spin-phonon bottleneck effects in evaporable vanadyl-based molecules with long spin coherence.
abstract: Vanadium(iv) complexes have recently shown record quantum spin coherence times that in several circumstances are limited by spin-lattice relaxation. The role of the environment and vibronic properties in the low temperature dynamics is here investigated by a comparative study of the magnetization dynamics as a function of crystallite size and the steric hindrance of the β-diketonate ligands in VO(acac)2(1), VO(dpm)2(2) and VO(dbm)2(3) evaporable complexes (acac-= acetylacetonate, dpm-= dipivaloylmethanate, and dbm-= dibenzoylmethanate). A pronounced crystallite size dependence of the relaxation time is observed at unusually high temperatures (up to 40 K), which is associated with a giant spin-phonon bottleneck effect. We model this behaviour by an ad hoc force field approach derived from density functional theory calculations, which evidences a correlation of the intensity of the phenomenon with ligand dimensions and the unit cell size.
authors.affiliation: Dipartimento di Chimica "U. Schiff" and INSTM UdR Firenze, Università degli Studi di Firenze, Via della Lastruccia 3, I50019 Sesto Fiorentino, Firenze, Italy. roberta.sessoli@unifi.it.
authors.forename: L
authors.initials: L
authors.lastname: Tesi
authors.forename: A
authors.initials: A
authors.lastname: Lunghi
authors.forename: M
authors.initials: M
authors.lastname: Atzori
authors.forename: E
authors.initials: E
authors.lastname: Lucaccini
authors.forename: L
authors.initials: L
authors.lastname: Sorace
authors.forename: F
authors.initials: F
authors.lastname: Totti
authors.forename: R
authors.initials: R
authors.lastname: Sessoli