Lanthanide(III)-based
coordination complexes have been explored
as a source of bifunctional molecular materials combining Single-Molecule
Magnet (SMM) behavior with visible-to-near-infrared photoluminescence.
In pursuit of more advanced multifunctionality, the next target is
to functionalize crystalline solids based on emissive molecular nanomagnets
toward high proton conductivity and an efficient luminescent thermometric
effect. Here, a unique multifunctional molecule-based material, (H5O2)2(H)[YbIII(hmpa)4][CoIII(CN)6]2·0.2H2O (1, hmpa = hexamethylphosphoramide), composed of molecular
{YbCo2}3– anions noncovalently bonded
to acidic H5O2
+ and H+ ions, is reported. The resulting YbIII complexes present
a slow magnetic relaxation below 6 K and room temperature NIR 4f-centered
photoluminescence sensitized by [Co(CN)6]3– ions. The microporous framework, built on these emissive magnetic
molecules, exhibits a high proton conductivity of the H-hopping mechanism
reaching σ of 1.7 × 10–4 S·cm–1 at 97% relative humidity, which classifies 1 as a superionic conductor. Moreover, the emission pattern
is strongly temperature-dependent which was utilized in achieving
a highly sensitive single-center luminescent thermometer with a relative
thermal sensitivity, S
r > 1% K–1 in the 50–175 K range. This work shows an
unprecedented combination
of magnetic, optical, and electrical functionalities in a single phase
working as a proton conductive NIR-emissive thermometer based on Single-Molecule
Magnets.
Microporous magnets
compose a class of multifunctional molecule-based
materials where desolvation-driven structural transformation leads
to the switching of magnetic properties. Herein, we present a special
type of microporous magnet where a dehydration–hydration process
within a bimetal coordination framework results in the switching of
emissive DyIII single-molecule magnets (SMMs). We report
a three-dimensional (3-D) cyanido-bridged coordination polymer, {[DyIII(H2O)2][CoIII(CN)6]}·2.2H2O (1), and its dehydrated form
of {DyIII[CoIII(CN)6]} (2), which was obtained through a reversible single-crystal-to-single-crystal
transformation. Both phases are composed of paramagnetic DyIII centers alternately arranged with diamagnetic hexacyanidocobaltates(III).
The hydrated phase contains eight-coordinated [DyIII(μ-NC)6(H2O)2]3– complexes
of a square antiprism geometry, while the dehydrated form contains
six-coordinated [DyIII(μ-NC)6]3– moieties of a trigonal prism geometry. This change in coordination
geometry results in the generation of DyIII single-molecule
magnets in 2, whereas slow magnetic relaxation effect
is not observed for DyIII sites in 1. The D
4d-to-D
3h symmetry
change of DyIII complexes produces also the shift of photoluminescent
color from nearly white to deep yellow thanks to the modulation of
emission bands of f–f electronic transitions. A combined approach
utilizing dc magnetic data and low-temperature emission
spectra confirmed an axial crystal field of trigonal prismatic DyIII complexes in 2, which produces an Orbach type
of slow magnetic relaxation. Therefore, we present a unique route
to the efficient switching of SMM behavior and photoluminescence of
DyIII complexes embedded in a 3-D cyanido-bridged framework.
Coordination complexes of lanthanide(3+) ions can combine Single-Molecule Magnetism (SMM) with thermally-modulated luminescence applicable in optical thermometry. We report an innovative approach towards high performance SMM-based optical thermometers which explores...
A two‐step hysteretic FeII spin crossover (SCO) effect was achieved in programmed layered Cs{[Fe(3‐CNpy)2][Re(CN)8]}⋅H2O (1) (3‐CNpy=3‐cyanopyridine) assembly consisting of cyanido‐bridged FeII‐ReV square grid sheets bonded by Cs+ ions. The presence of two non‐equivalent FeII sites and the conjunction of 2D bimetallic coordination network with non‐covalent interlayer interactions involving Cs+, [ReV(CN)8]3− ions, and 3‐CNpy ligands, leads to the occurrence of two steps of thermal SCO with strong cooperativity giving a double thermal hysteresis loop. The resulting spin‐transition phenomenon could be tuned by an external pressure giving the room‐temperature range of SCO, as well as by visible‐light irradiation, inducing an efficient recovery of the high‐spin FeII state at low temperatures. We prove that octacyanidorhenate(V) ion is an outstanding metalloligand for induction of a cooperative multistep, multiswitchable FeII SCO effect.
A cyanido-bridged layered {[Dy(III)(4-OHpy)2(H2O)3][Co(III)(CN)6]}·0.5H2O (1) (4-OHpy = 4-hydroxypyridine) framework with dual photo-luminescence and magnetic properties was prepared. 1 exhibits visible emission whose color, yellow to greenish-blue, is switchable by selected wavelengths of UV excitation light. Magnetic data revealed that 1 shows not only the slow magnetic relaxation of a typical Dy(III) single-ion origin but also the relaxation process caused by the magnetic dipole-magnetic dipole interactions between the neighbouring Dy(III) centers.
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