Heterometallic 3d-4f Single Molecule Magnets: Experiment and Theory
Kuduva R Vignesh, Stuart K Langley, Keith S Murray and G Rajaraman Email: [email protected]
Department of Chemistry, IITB-Monash Research Academy, IIT Bombay, Mumbai-400076
References:
Acknowledgement IITB-Monash Research Academy
1) R. Sessoli, D.Gatteschi, A. Caneshi, M. A. Novak, Nature 1993, 365, 141. 2) D. Gatteschi, Angew. Chem., Int. Ed. 2003, 42, 246. 3) D. Gatteschi, R. Sessoli, J. Villain, Molecular Nanomagnets, Oxford University Press, Oxford, 2006. 4) Bagoni, L, Wernsdorfer, W. Nature Materials, 2008, 7, 179-186. 5) Murray et. al. Chem. Commun. 2010, 46, 7787. 7) Powell et. al. Coor. Chem. Rev. 2009, 232, 8) Rajraman et. al. Chem. Eur. J. 2015, accepted. 9) Aquilante et.al. WIREs Comput. Mol. Sci. 2013, 3, 143-149. 10) Cirera et.al. Chem. Eur. J., 2006, 12, 3162.11) Chibotaru et.al. Angew. Chem. Int. Ed., 2008, 47, 4126-4129. 12) Gaussian 09, Revision A.02, Gaussian,Inc., Wallingford CT, 2009.
Generic Mechanism of {Co2Ln2} based SMMs
Co(NO3)2.6H2O
+
Ln(NO3)3.6H2O
+ N
HO
HO
+
COOH
Et3N
MeCN8
8
Ueff=87K
τQTM =0.16s
1
Single Molecule Magnets Ueff = S
2D
Magnetic Refrigerants
Information Storage Devices
Spintronics
Q-bits
Mn(NO3)2.6H2O
+
Ln(NO3)3.6H2O
+ N
HO
HO
+
COOH
REt3N
MeCN
1
Red block
crystals
Computational Details MOLCAS 7.8 Code, Gaussian 09
CASSCF+RASSI calculations
Active Space (9,7) for DyIII
ANO…RCC TZVP Dy & ANO…RCC VDZP (C, N,O)
DFT calculation CSDZ Basis Set for Y & TZVP for rest
𝐻 = −2𝐽 𝑆𝑀𝑛1 𝑆𝑀𝑛2
S=16 & J = 0.43 cm-1
Ln= Dy(1), Ho(2&5), Y(3&6) , Yb(4) and Er(7)
R= -H or –CH3
1
zig-zag
arrangement of
two ions up
and two ions
down.
The MnIII centres →Jahn-Teller octahedral distortions
with a {NO5} sphere & The DyIII ions → distorted
triangular dodecahedron geometries.
Overall void volume of approximately 43% of
the unit cell.
No uptake of N2 at 77K in the range 0 – 0.99 atm.
Similarly, the uptake of CO2 at 273K was lower.
0 50 100 150 200 250 300
2
4
6
8
10
12
14
16
18
20
22
24
26
T / K
MT
/ c
m3 K
mo
l-1
Exp data
DFT-sim
1 2 3 4 5 6 7 8
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
50Hz
100Hz
250Hz
500 Hz
997 Hz
M"
/ cm
3 K
mo
l-1
T / K
a) b)
From room T to
1.8 K is
indicative of the
depopulation of
the excited mJ
Stark levels of
the LnIII ions. Dy1 Dy2 Dy3 Dy4 Dy5 Dy6 Dy7 Dy8
gx 0.3101 0.1414 0.3236 0.1636 0.3624 0.1482 0.3442 0.1480
gy 0.8721 0.3421 0.9181 0.4073 1.0564 0.3628 0.9942 0.3624
gz 18.5386 19.1346 18.4936 19.0719 18.4212 19.1533 18.4683 19.1282
No SMM behavior was observed for
{MnIII8HoIII
8} (2), {MnIII8YbIII
8} (4),
{MnIII8HoIII
8} (5) and {MnIII8ErIII
8} (7).
3
8
9
10
zJ= -0.01 cm-1
The S = 16 GS & very small J explains
the fast magnetic relaxation rate and
weak SMM behaviour observed for 3. POLY_ANISO
Mn(III)-Dy(III) interactions.
0 50 100 150 200 250 30010
20
30
40
50
60
70
80
T/K
MT
/cm
3 K
mo
l-1
J = - 0.1 cm-1
Poly-aniso fit
Exp data
The fast QTM and
weak SMM behaviour
in {Mn8Dy8} wheel → very weak Mn(III)-
Dy(III) coupling &
unfavourable
Dy(III)/Mn(III)
anisotropy.
Green Crystals
{Ln= Dy(8), Tb(9),Ho(10)}
9
10
A planar butterfly motif, with the LnIII ions occupying the body positions and the CoIII ions the outer wing.
At 2 K the relaxation becomes
independent of T, indicating a
QTM of relaxation.
Tb & Ho analogues showed
susceptibility peaks in 5000 Oe and
2000 Oe dc field respectively. This
behavior is due to very fast QTM at
zero field.
Poly_Aniso Fit
Origin of Anisotropic Exchange
For {MnIII8DyIII
8} (1)
& {MnIII8Y
III8}(3&6),
indicating SMM
behavior but with fast
QTM.
SHAPE Analysis → Two type of Dy ions
8 9 10
Computational Details Active Space (9,7) for DyIII,(8,7) for TbIII, (10,7) for HoIII
ANO…RCC TZVP for Dy, Tb & Ho
gx gy gz Ueff
{Dy2Co2}(8) 0.0 0.0 39.8612 112.2 K
{Tb2Co2}(9) 0.0 0.0 34.4534 4.8 K
{Ho2Co2}(10) 0.0 0.0 21.1565 8.7 K
The QTM is lower in the {Co2Dy2} because of weak
AF coupling.
The nonmagnetic KDs are a fingerprint of
polynuclear complexes of strongly anisotropic
Ln’s. KDs → the design of qubits for
quantum computation.
8
The decrease of
the χMT product
(at H = 1 T) for 8-
10 from room
temperature to 1.8
K is indicative of
the presence of
AF interactions.
