Calix[4]arene-Based Single-Molecule Magnets Karotsis, Georgios; Teat, Simon J.; Wernsdorfer, Wolfgang ...
Angewandte Chemie (International ed.),
October 19, 2009, Letnik:
48, Številka:
44
Journal Article
Recenzirano
Odprti dostop
Protective skin: Single‐molecule magnets (SMMs) that are protected by two calix4arenes have been synthesized (see picture: Mn purple, O red, N blue, C gray). The calixarene allows supramolecular ...isolation of the SMM, and alteration of its upper rim provides control over the orientation in the solid state by altering the distances between layers.
Tetranuclear Mn(III)2Ln(III)2 complexes formed using tripodal ligands display frequency dependent out-of-phase ac susceptibility signals and temperature and sweep rate dependent hysteresis loops.
Ultrafast transient absorption spectra were recorded for Mn(terpy)X
, where X = Cl, F, and N
, to explore photoinduced switching from axial to equatorial Jahn-Teller (JT) distortion. Strong ...oscillations were observed in the transients, corresponding to a wavepacket on the excited-state potential energy surface with oscillation frequency around 115 cm
for all three complexes. Multireference quantum chemistry calculations indicate that the reaction coordinate is a pincer-like motion of the terpyridine ligand arising from bond length changes in the excited state due to the JT switch. We observed long dephasing times of the wavepacket, with times of 620 fs for Mn(terpy)Cl
, 450 fs for Mn(terpy)F
, and 370 fs for Mn(terpy)(N
)
. The dephasing time of these coherences decreases with an increasing number of vibrational modes at lower energy than the mode dominating the reaction coordinate, suggesting they act as an effective bath to dissipate the excess energy obtained from photoexcitation.
[Fe]: a frustrated, centred tetrakis hexahedron Cutler, Daniel J; Singh, Mukesh K; Nichol, Gary S ...
Chemical communications (Cambridge, England),
09/2021, Letnik:
57, Številka:
71
Journal Article
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The combination of two different Fe
III
salts in a solvothermal reaction with triethanolamine results in the formation of a high symmetry Fe
III
15
cluster whose structure conforms to a centred, ...tetrakis hexahedron.
The combination of two different Fe
III
salts in a solvothermal reaction with triethanolamine results in the formation of a high symmetry Fe
III
15
cluster whose structure conforms to a centred, tetrakis hexahedron.
The use of derivatised salicylaldoximes in Mn chemistry has led to the isolation of a plethora of beautiful new SMMs ranging in nuclearity from three to eight and with spin ground states as large as ...S = 12-including a Mn6 complex with the largest energy barrier to magnetisation reversal yet reported. The deliberate chemically-induced structural distortion of the Mn6 molecule allows the isolation of analogous family members displaying remarkably different magnetic properties and this in turn allows for a rare semi-quantitative magneto-structural correlation which enables prediction of the magnetic properties of new family members.
The reaction between MnCl 2 ·4H 2 O, 2,2′-bis- p - t Bu-calix4arene (H 8 L1) and 2-(hydroxymethyl)pyridine (hmpH) in a basic dmf/MeOH solution results in the formation of the complex MnIII10MnII4(L1) ...3 (hmp) 4 (μ 3 -O) 4 (μ 3 -OH) 2 (MeOH) 4 (dmf) 6 (dmf) 4 ( 6 ) upon vapour diffusion of petroleum ether into the mother liquor. The crystals are in the monoclinic space group C 2/ c , with the asymmetric unit (ASU) comprising one half of the molecule. The structure describes a large S -shaped cluster (∼40 Å top to tail) where the unusual syn and anti conformations of the calixarene ligands results in two binding pockets each containing a MnIII5MnII2 moiety comprised of two perpendicular, vertex-sharing Mn 4 butterflies. One butterfly possesses a MnIII4O 4 core and the second a MnIII2MnII2O 3 unit with the Mn II ions in the central body positions. Magnetic susceptibility and magnetisation measurements reveal weak exchange interactions between the metal centres.
A [Mn] wheel-of-wheels Coletta, Marco; Tziotzi, Thomais G; Gray, Mark ...
Chemical communications (Cambridge, England),
04/2021, Letnik:
57, Številka:
34
Journal Article
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Odprti dostop
A Mn
18
wheel of wheels is obtained from the reaction of MnBr
2
·4H
2
O and LH
3
in MeOH. The metallic skeleton reveals two asymmetric Mn
III
6
Mn
II
2
square wheels connected into a larger wheel
...via
two Mn
II
ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies.
A Mn
18
wheel of wheels is constructed from a simple reaction incorporating a triazatriol ligand.
Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal ...oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the 'transformation' from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with T
controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, 'squeezing' the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of T
with pressure.
A [Mn32] Double-Decker Wheel Manoli, Maria; Inglis, Ross; Manos, Manolis J. ...
Angewandte Chemie (International ed.),
May 2, 2011, Letnik:
50, Številka:
19
Journal Article
Recenzirano
Odprti dostop
Inventing the double wheel: A mixed–valent Mn32 cluster with a very rare “double‐decker” wheel topology (see its metal–oxygen core: MnIII blue, MnII pink, O red) is reported. It is by far the ...highest‐nuclearity example of its type, and it displays SMM behavior with the largest effective barrier to magnetization relaxation (Ueff≈44.5 K) for any molecular wheel.
Fridge magnet: A decametallic mixed‐valent Mn supertetrahedron (see picture; M purple, O red, N blue, Br brown, C gray) displays dominant ferromagnetic exchange and a spin ground state of S=22. The ...magnetic behavior of the cluster makes it suitable for use as a low‐temperature magnetic refrigerant.
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