Résumé
The syntheses of the two new single molecule magnets, [Mn
12
O
12
(O
2
CR)
16
(H
2
O)
4
]S (R = CHCHCH
3
, S = H
2
O (
2
) and R = C
6
H
4
C
6
H
5
, S = 2C
6
H
5
C
6
H
4
COOH (
3
)) and X-ray crystal structure of the first are described. Complex
2
crystallizes in the orthorhombic space group
Ibca
, which at 198 K has
a
= 21.2208(4),
b
= 21.2265(4),
c
= 42.2475(6) Å, and
Z
= 8. Frequency-dependent out-of-phase ac signals are seen for both complexes, which indicates that these two complexes function as single-molecule magnets. Dc magnetization measurements for both complexes also exhibit hysteresis in the magnetization
vs.
external magnetic field plots with regular steps characteristic of quantum mechanical tunnelling of the direction of magnetization. The techniques of LDI- and MALDI-TOF mass spectrometry have been investigated to prospect their utility for the chemical characterization of Mn
12
clusters. The technique is applied to known clusters as well as to two new compounds, and characteristic signals are found, especially predominant being that of the [Mn
12
O
12
(O
2
CR)
14
] cation or anion, showing the potential interest of this technique for those preparing this type of compounds.