title: Unraveling the crystal structure of lanthanide-murexide complexes: use of an ancient complexometry indicator as a near-infrared-emitting single-ion magnet.
abstract: Herein, we provide some structural evidence of the complexation color-change of murexide solutions in presence of lanthanide, which has been used for decades in complexometric studies. For Ln = Sm to Lu and Y, the compounds crystallize as monomeric [Ln(Murex)3]⋅11 H2O with an N3O6 tricapped square-antiprism environment, which are stable up to 250 °C. Single-ion magnet (SIM) behavior is then observed on the Yb(III) derivative in an original nine-coordinated environment. In-field slow relaxation (Δ = (15.6±1) K; τ0 = 2.73×10(-6) s) is observed with a very narrow distribution of the relaxation time (αmax = 0.09). Magnetic and photophysical properties can be correlated. On one hand the analysis of NIR emission spectrum permits to have access to crystal field parameters and to compare them with those extracted from dc measurements. On the other hand, magnetic measurements permit to identify the nature of the MJ states involved in the (2)F5/2 → (2)F7/2 luminescence spectrum. The gap between the low-lying states is in agreement with the energy barrier obtained from magnetic slow-relaxation measurement.
authors.affiliation: Université Européenne de Bretagne, France, INSA, ISCR, UMR 6226, 20 Avenuedes buttes de Coësmes CS70839, 35708 Rennes Cedex (France).
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Yi
authors.forename: Kevin
authors.initials: K
authors.lastname: Bernot
authors.forename: Vincent
authors.initials: V
authors.lastname: Le Corre
authors.forename: Guillaume
authors.initials: G
authors.lastname: Calvez
authors.forename: Fabrice
authors.initials: F
authors.lastname: Pointillart
authors.forename: Olivier
authors.initials: O
authors.lastname: Cador
authors.forename: Boris
authors.initials: B
authors.lastname: Le Guennic
authors.forename: Julie
authors.initials: J
authors.lastname: Jung
authors.forename: Olivier
authors.initials: O
authors.lastname: Maury
authors.forename: Virginie
authors.initials: V
authors.lastname: Placide
authors.forename: Yannick
authors.initials: Y
authors.lastname: Guyot
authors.forename: Thierry
authors.initials: T
authors.lastname: Roisnel
authors.forename: Carole
authors.initials: C
authors.lastname: Daiguebonne
authors.forename: Olivier
authors.initials: O
authors.lastname: Guillou
keywords: IR spectroscopy; X-ray diffraction; lanthanides; ligands; magnetic properties