Dysprosium-based complexes with a flat pentadentate donor: a magnetic and ab initio study. Issue 24 (10th June 2020)

• Record Type: Journal Article
• Authors: Fondo, Matilde; Corredoira-Vázquez, Julio; García-Deibe, Ana M.; Gómez-Coca, Silvia; Ruiz, Eliseo; Sanmartín-Matalobos, Jesús
• Is Part Of: Dalton transactions. Volume 49:Issue 24(2020)
• Page Start: 8389
• Page End: 8401
• Publication Date: 2020-06-10
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt01293a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Hitherto unknown dysprosium(iii ) complexes of a related flat N3 O2 donor show ac susceptibility frequency-dependence, (Et3 NH)[Dy0.09 Y0.91 (L)(NO3 )2 ] being a SIM at zero field. Abstract : The reactivity of the well-known pentadentate N3 O2 Schiff base H2 L (2, 6-bis(2-hydroxyphenyliminomethyl)pyridine) towards a lanthanoid metal, in this case Dy III, has been investigated for the first time. This reactivity markedly depends on the pH of the medium and, accordingly, two different complexes, [Dy(HL)(NO3 )2 ]·H2 O (1 ·H2 O) and [Dy(L)(NO3 )(EtOH)(H2 O)]·2H2 O (2 ·2H2 O), could be isolated from dysprosium(iii ) nitrate and H2 L. In addition, reaction of H2 L with dysprosium(iii ) chloride in methanol yields [Dy(HL′)2 ][Dy(L)(Cl2 )] (3 ), where H2 L′ ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N2 O2 hemiacetal donor derived from the partial hydrolysis of the H2 L ligand, and subsequent addition of the methanol solvent to the carbonyl group. This latter reaction has been firstly observed for a lanthanoid metal. Single crystal X-ray diffraction studies of 1 ·1.15Py·0.3CH3 C6 H5, 2 ·2H2 O and 3 show that the Schiff base is acting as a nearly flat pentadentate donor in all the cases, this behaviour being independent of the deprotonation degree of the phenolic oxygen atoms, both mono- or bisdeprotonated. Complexes 1 ·1.15Py·0.3CH3 C6 H5 and 2 ·2H2 O show DyN3 O6 cores, with distorted geometries closer to spherical tricapped trigonal prism or spherical capped square antiprism for 1 ·1.15Py·0.3CH3 C6 H5 and 2 ·2H2 O, respectively. In the case of 3, the [Dy(HL′)2 ] + cation shows a dysprosium ion in an N4 O4 triangular dodecahedron environment, while the [Dy(L)(Cl2 )] − anion displays a DyN3 O2 Cl2 core with distorted pentagonal bipyramidal geometry. Moreover, attempts to dilute 1 ·H2 O with yttrium yielded single crystals of (Et3 NH)[Dy0.09 Y0.91 (L)(NO3 )2 ] (4 ), where the Schiff base shows a similar pentadentate coordination mode. Dynamic magnetic studies of 1 ·H2 O, 2 ·2H2 O and 3 show that 2 ·2H2 O and 3 present field-induced slow relaxation of the magnetisation, with U eff barriers of 46.1(9) and 31.0(7) K for 2 ·2H2 O and 3, respectively, while 1 ·H2 O does not exhibit frequency-dependent peaks of the out of phase susceptibility, even in the presence of an external dc magnetic field. By contrast, the dilute sample 4 behaves as a SIM at zero dc field, with an energy barrier of ca . 49 K. Ab initio calculations using CASSCF methods including spin–orbit effects qualitatively support the obtained magnetic results, indicating that axiality is not the only factor that should be taken into account in order to increase effective energy barriers.