In search of magneto‐optic materials, the mononuclear compounds LnIII(depma)(NO3)3(hmpa)2 (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo 4+4 dimerization when irradiated at 365 nm ...without loss of crystallinity. The Dy compound switches from a single‐ion to a single‐molecule magnet with doubling of the spin reversal barrier energy and from yellow‐green to blue‐white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto‐optic property.
Pairing up: The mononuclear compound DyIII(depma)(NO3)3(hmpa)2 (depma= 9‐diethylphosphono‐methylanthracene, hmpa=hexamethylphosphoramide) undergoes reversible 4+4 photodimerization in a single‐crystal‐to‐single‐crystal manner. This process is accompanied by a change from a single‐ion to a single‐molecule magnet and from yellow‐green to blue‐white emission.
Photo‐responsive lanthanide‐based single‐molecule magnets (SMM) hold great promise for future switching and memory devices. Herein, we report a dysprosium phosphonate DyIII(SCN)2(NO3)(depma)2(4‐hpy)2 ...(1Dy), which features a supramolecular framework containing layers of hydrogen‐bonding network and pillars of π–π interacted anthracene units. The photocycloaddition reaction of anthracene pairs led to a rapid and reversible single‐crystal‐to‐single‐crystal (SC–SC) structural transition to form the 1D coordination polymer DyIII(SCN)2(NO3)(depma2)(4‐hpy)2n (2Dy), accompanied by photoswitchable SMM properties with the reduction of effective energy barrier by half and the narrowing of the butterfly‐like hysteresis loop. The diluted sample showed a photo‐induced switch of the blocking temperature (TB) from 3.8 K for 1Dy@Y to 2.6 K for 2Dy@Y. This work may inspire the construction of lanthanide‐based molecular materials with targeted photo‐responsive magnetic properties.
A reversible photo‐induced single‐crystal‐to‐single‐crystal structural transformation was achieved for a mononuclear dysprosium‐anthracene compound to form a 1D coordination polymer. This compound displays photoswitchable SMM properties with reduced effective spin‐reversal energy barrier, narrowed butterfly‐like hysteresis loop, and decreased blocking temperature.
Artificial smart materials with switchable multifunctionality are of immense interest owing to their wide application in sensors, displays and memory devices. Lanthanide complexes are promising ...multifunctional materials integrating optical and magnetic characteristics. However, synergistic manipulation of different physical properties in lanthanide systems is still challenging. Herein we designed and synthesized a mononuclear complex Dy
III
(SCN)
3
(depma)
2
(4-hpy)
2
(
1
), which incorporates 9-diethylphosphonomethylanthracene (depma) as a photo-active component and 4-hydroxypyridine (4-hpy) as a polar component. This compound shows several unusual features: (a) reversible thermo-responsive phase transition associated with the order-disorder transition of 4-hpy and SCN
−
, which leads to thermochromic behavior and dielectric anomaly; (b) reversible photo-induced dimerization of anthracene groups, which leads to synergistic switching of luminescence, magnetic and dielectric properties. To our knowledge, compound
1
is the first example of lanthanide complexes that show stimuli-triggered synergistic and reversible switching of luminescence, magnetic and dielectric properties.
Dy
III
(SCN)
3
(depma)
2
(4-hpy)
2
(
1
) shows reversible thermo-induced phase transition associated with thermochromism and dielectric anomaly and photo-induced dimerization with synergistic switching of luminescence, magnetic and dielectric properties.
Dianthracene ligands obtained through photocycloaddition reaction can undergo de‐dimerization upon heating. Here we report the first examples of lanthanide‐dianthracene coordination polymers with ...chain structures, namely, LnL(depma2)Br ⋅ xH2O 1‐Ln, Ln=Dy (x=5), Gd (x=4); H2L=N1,N3‐bis(salicylideneimino)diethylenetriamine, depma2=photodimerized 9‐diethylphosphonomethylanthracene. The lanthanide ions possess pseudo‐D5h geometries with five equatorial positions occupied by three N and two O atoms from L2− and two axial positions by the phosphonate oxygen atoms from bridging depma2 ligands. Thermo‐induced structural transformation is observed for both compounds between 120 and 140 °C, which involves de‐dimerization of depma2 and elimination of bromoethane. The structural transformation is accompanied with the switch‐on of photoluminescence and, in the case of 1‐Dy, also changes of magnetic dynamics.
Lanthanide coordination polymers LnL(depma2)Br ⋅ xH2O (1‐Ln, Ln=Dy, Gd) are reported to show chain structures in which the Ln atoms are bridged by dianthracene‐phosphonate ligands. They undergo thermo‐induced structural transformations associated with the dehydration, de‐dimerization of dianthracene and elimination of bromoethane. The latter two occur simultaneously, accompanied with the switch‐on of photoluminescence and also changes of magnetic dynamics for 1‐Dy.
{Dy
(EDDC)
(μ
-AcO)
(μ
-C
H
PO
)(μ
-C
H
PO
)(μ
-AcO)
(AcO)
(H
O)(CH
OH)
}
(μ
-C
O
)·
H
O (
), where H
EDDC is
',
'',
,
',
'',
',
''-(ethane-1,2-diylidene)dipyrazine-2-carbohydrazide and C
H
PO
H
is ...9-anthrylmethylphosphonic acid, is found to undergo two consecutive single-crystal-to-single-crystal transformations. The first is under UV irradiation (
= 365 nm for 3 d in air) to {Dy
(EDDC)
(μ
-AcO)
(μ
-C
H
PO
)
(μ
-AcO)
(AcO)
(H
O)
}
(μ
-C
O
)·
H
O (
) where the two CH
OH are replaced by two H
O and the second by annealing under N
at 100 °C on a diffractometer or under Ar in a glovebox to {Dy
(EDDC)
(μ
-AcO)
(μ
-C
H
PO
)
(μ
-AcO)
(H
O)}
(μ
-C
O
) (
or
) where it has lost two H
O molecules. The second transformation is reversible by exposure to air at room temperature (
). While the overall structures are the same (retaining the space group
2
/
), there is a considerable expansion of the unit cell from
(8171 Å
) to
(8609 Å
) and
(8610 Å
) and the coordinations of the Dy atoms undergo major reconstructions. This is associated with switching the single-molecule-magnetism (SMM) from OFF for
to ON for
and to OFF again for
in air. Such a switching mechanism associated with the retention of crystallinity is unique in the chemistry of dysprosium. The structure of the molecule is formed from two symmetry related pentamers joined by an oxalate. A related compound containing two isolated neutral pentamers {Dy
(EDDC)
(μ
-AcO)
(μ
-C
H
PO
)
(μ
-AcO)
(AcO)
(H
O)
}{Dy
(EDDC)
(μ
-AcO)
(μ
-C
H
PO
)(μ
-C
H
PO
)(μ
-AcO)
(AcO)
(CH
OH)
}·2CHCl
(
) has also been isolated with closely related Dy coordination and it exhibits similar SMM behaviour in zero field.
Helical architectures with controllable helical sense bias have recently attracted considerable interest for mimicking biological helices and developing novel chiral materials. Coordination polymers ...(CPs), composed of metal ion nodes and organic linkers, are intriguing systems showing tunable structures and functions. However, CPs with helical morphologies have rarely been explored so far. Particularly, chirality inversion through external stimulus has not been achieved in helical CPs. In this work, we carried out an in‐depth investigation on the self‐assembly of 1D gadolinium(III) phosphonate CPs using GdX3 (X=Cl, Br, I) and Gd(RSO3) (R=CH3, C6H5, CF3) as metal sources and R‐(1‐phenylethylamino)methyl phosphonic acid (R‐pempH2) as ligand. Superhelices were formed by precise control of the interchain interactions through different intercalated anions. Furthermore, the twisting direction of superhelices could be controlled by synergistic effect of anions and pH. This study may provide a new route to fabricate helical nanostructures of CPs with a desirable chiral sense and help understand the inner mechanism of the self‐assembly process of macroscopic helical structures of molecular systems.
The morphologies of 1D coordination polymers of GdIII(R‐pempHx)3(anion)(3‐3x) can be controlled by the combined effect of pH and anions. Superhelices were formed when anions with larger sizes and enhanced anion‐chain interactions, such as I− (and I3−), C6H5SO3− and CF3SO3−, were present in the systems. When the anion is CF3SO3−, a complete chirality inversion from left‐ to right‐handedness was observed by raising the pH of the reaction mixture.
Multifunctional molecular materials combining magnetic, luminescent and dielectric properties are attractive for potential applications in spintronics and molecular devices. Herein we report three ...isostructural mononuclear lanthanide phosphonates, namely, Ln(NO3)3(2‐deap)3 Ln=Dy (1Dy), Er (2Er), Yb (3Yb), 2‐deap=diethyl anthrancen‐2‐ylphosphonate which crystallize in polar space group Pna21. Magnetic studies revealed field‐induced slow magnetization relaxation for 1Dy and 3Yb, but not for 2Er down to 1.8 K. Theoretical calculations were conducted to rationalize the magneto‐structural relationship. The photoluminescent properties are also dependent on the lanthanide ion. For 1Dy, luminescence was observed only in the visible region mainly originating from the ligand. For 2Er, luminescence was observed only in the near‐infrared (NIR) region due to a complete energy transfer from the ligand to the ErIII ion. Regarding to 3Yb, luminescence was observed in both visible and NIR regions suggesting a partial energy transfer from the ligand to YbIII ion. Dielectric and piezoelectric measurements were performed on single crystals of 3Yb, which confirmed the presence of high dielectric anisotropy and weak piezoelectric response.
By incorporating achiral anthracene phosphonate ligand, polar complexes Ln(NO3)3(2‐deap)3 Ln=Dy (1Dy), Er (2Er), Yb (3Yb); 2‐deap=diethyl anthracen‐2‐ylphosphonate were obtained showing multifunctionalities such as photoluminescence in the visible and/or NIR regions, field‐induced slow magnetization relaxation, high dielectric anisotropy and weak piezoelectric response.
Layered heterometallic 5f–3d uranyl phosphonates can exhibit unique luminescent and/or magnetic properties, but the fabrication and properties of their 2D counterparts have not been investigated. ...Herein we report three heterobimetallic uranyl phosphonates, namely, (UO2)3M(2‐pmbH)4(H2O)4 ⋅ 2H2O MU, M=Co(II), CoU; Mn(II), MnU; Zn(II), ZnU; 2‐pmbH3=2‐(phosphonomethyl)benzoic acid. They are isostructural and display two‐dimensional layered structures where the M(II) centers are encapsulated inside the windows generated by the diamagnetic uranyl phosphonate layer. Each M(II) has an octahedral geometry filled with four water molecules in the equatorial positions and two phosphonate oxygen atoms in the axial positions. The uranium atoms adopt UO7 pentagonal bipyramidal and UO6 square bipyramidal geometries. The lattice and coordination water molecules can be released by thermal treatment and reabsorbed in a reversible manner, accompanied with changes of magnetic dynamics. Interestingly, the bulk samples of MU can be exfoliated in acetone via freezing and thawing processes forming nanosheets with single‐layer or two‐layer thickness (MU‐ns). Magnetic studies revealed that the CoU and MnU systems exhibited field‐induced slow magnetization relaxation at low temperature. Compared with crystalline CoU, the magnetic relaxation of the CoU‐ns aggregates is significantly accelerated. Moreover, photoluminescence measured at 77 K showed slight red‐shift of the five characteristic uranyl emission bands for ZnU‐ns in comparison with those of the crystalline ZnU. This work gives the first examples of 2D materials based on 5f–3d heterometallic uranyl phosphonates and illustrates the impact of dimension reduction on their magnetic/optical properties.
Layered heterometallic uranyl phosphonates (UO2)3M(2‐pmbH)4(H2O)4 ⋅ 2H2O MU, M=Co(II), CoU; Mn(II), MnU; Zn(II), ZnU can be exfoliated into nanosheets with single/two‐layer thickness (MU‐ns). Comparing to the bulk crystalline samples, the aggregates of nanosheets exhibited significant differences in magnetic dynamics (for CoU) and photoluminescence (for ZnU).
Metal-organic framework (MOF)-based heterostructures are attractive because they can provide versatile platforms for various applications but are limited by complex liquid epitaxial growth methods. ...Here, we employ photolithography to fabricate and control MOF-based heterostructured crystals
4 + 4 photocycloaddition. A layered dysprosium-dianthracene framework, Dy(NO
)
(depma
)
·(depma
)
(2) depma
= pre-photodimerized 9-diethylphosphonomethylanthracene (depma) underwent a single-crystal-to-single-crystal transition at 140 °C to form Dy(NO
)
(depma)(depma
)·(depma
)
(3). The dissociated anthracene moieties are face-to-face π-π interacted allowing a reversible photocycloaddition between 2 and 3. This structural transformation causes a luminescence switch between blue and yellow-green and thus can be used to fabricate erasable 2 + 3 heterostructured crystals for rewritable photonic barcodes. The internal strain at the heterostructure interface leads to photobending and straightening of the crystal, a photomechanical response that is fast, reversible and durable, even operating at 140 °C, making it promising for photoactuation. This work may inspire the development of intelligent MOF-based heterostructures for photonic applications.
In the aerospace industry, milling of the thin-wall multi-framed work-piece (TMW) is a critical challenging task due to the mutually coupling dynamics of adjacent frames and side plates. Evaluation ...of the effect of fixture layout on the dynamic response of thin-walled work-piece is a critical measure to determine whether the designed fixture can meet the requirements for the tightly specified tolerance of the part. A new analytical technique is proposed to determine the effect of fixture layout on the dynamic response of TMW during machining. In this modeling process, a workpiece-fixture system may be equivalent as a thin-multi-span plate (TMSP) with intermediate line and point supports. And then, double functions of Euler-Bernoulli beam can be utilized to describe mode shape of a TMW on basis of a span-by-span approach. Further, a dynamic equation of work-piece-fixture system can be modeled by the Lagrangian method in terms of new mode shape functions. Implementation of this technique is simple, enables avoidance of cumbersome mathematical calculations. Finally, the feasibility of the proposed approach is validated by a machining case.
•The objective of this paper predicts dynamic responses of thin-wall multi-framed workpiece (TMW) with fixture constraints during machining.•This workpiece-fixture system may be equivalent as a thin-multi-span plate (TMSP) with line and point supports.•Double functions of Euler-Bernoulli beam can be utilized to describe mode shape of a TMSP•The Lagrangian method is used to build an equation of dynamics of workpiece-fixture system by new mode shape functions.
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