Dysprosium-based complexes with a flat pentadentate donor: a magnetic and ab initio study
The reactivity of the well-known pentadentate N 3 O 2 Schiff base H 2 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 c...
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| Published in | Dalton transactions : an international journal of inorganic chemistry Vol. 49; no. 24; pp. 8389 - 8401 |
|---|---|
| Main Authors | , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
Cambridge
Royal Society of Chemistry
28.06.2020
|
| Subjects | |
| Online Access | Get full text |
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| Summary: | The reactivity of the well-known pentadentate N
3
O
2
Schiff base H
2
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)(NO
3
)
2
]·H
2
O (
1
·H
2
O) and [Dy(L)(NO
3
)(EtOH)(H
2
O)]·2H
2
O (
2
·2H
2
O), could be isolated from dysprosium(
iii
) nitrate and H
2
L. In addition, reaction of H
2
L with dysprosium(
iii
) chloride in methanol yields [Dy(HL′)
2
][Dy(L)(Cl
2
)] (
3
), where H
2
L′ ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N
2
O
2
hemiacetal donor derived from the partial hydrolysis of the H
2
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·0.3CH
3
C
6
H
5
,
2
·2H
2
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·0.3CH
3
C
6
H
5
and
2
·2H
2
O show DyN
3
O
6
cores, with distorted geometries closer to spherical tricapped trigonal prism or spherical capped square antiprism for
1
·1.15Py·0.3CH
3
C
6
H
5
and
2
·2H
2
O, respectively. In the case of
3
, the [Dy(HL′)
2
]
+
cation shows a dysprosium ion in an N
4
O
4
triangular dodecahedron environment, while the [Dy(L)(Cl
2
)]
−
anion displays a DyN
3
O
2
Cl
2
core with distorted pentagonal bipyramidal geometry. Moreover, attempts to dilute
1
·H
2
O with yttrium yielded single crystals of (Et
3
NH)[Dy
0.09
Y
0.91
(L)(NO
3
)
2
] (
4
), where the Schiff base shows a similar pentadentate coordination mode. Dynamic magnetic studies of
1
·H
2
O,
2
·2H
2
O and
3
show that
2
·2H
2
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
·2H
2
O and
3
, respectively, while
1
·H
2
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. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/d0dt01293a |