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.
A heptacyclic carbocycle possessing three p-quinodimethane units conjugated in one plane has been synthesized and shown to exhibit distinct biradical characteristics. The molecule has a HOMO/LUMO band gap of ca. 1 eV and a S(0)-T(1) energy gap of 2.12 kcal/mol, and it absorbs and emits near-IR light at room temperature. It is air-stable under ambient light for several months and thermally stable up to 160 °C under nitrogen, and it undergoes reversible two-electron oxidation and reduction. The synthetic approach is such that a smaller and larger oligo-p-quinodimethane can be synthesized.
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...
The addition of chiral 2,2'-(2,6-pyridinediyl)bis(4-isopropyl-2-oxazoline) (iPr-Pybox) to a self-assembled Co(II)–[W(V)(CN)(8)] magnetic system gives two enantiomorphic cyano-bridged chains, {[Co(II)((S,S)-iPr-Pybox)(MeOH)](3)[W(V)(CN)(8)](2)·5.5MeOH·0.5H(2)O}(n) (1-SS) and {[Co(II)((R,R)-iPr-Pybox) (MeOH)](3)[W(V)(CN)(8)](2)·5.5MeOH·0.5H(2)O}(n) (1-RR). Both compounds crystallize with a structure containing a unique crossed arrangement of one-dimensional chains that form a microporous supramolecular network with large channels (14.9 Å × 15.1 Å × 15.3 Å) filled with methanol. The investigated materials exhibited optical chirality, as confirmed by natural circular dichroism and UV-vis absorption spectra. 1-(SS) and 1-(RR) are paramagnets with cyano-mediated Co(II)-W(V) magnetic couplings that lead to a specific spin arrangement with half of the W(V) ions coupled ferromagnetically with their Co(II) neighbors and the other half coupled antiferromagnetically. Significant magnetic anisotropy with the easy axis along the [101] direction was confirmed by single-crystal magnetic studies and can be explained by the single-ion anisotropy of elongated octahedral Co(II) sites. Below 3 K, the frequency-dependent χ(M)"(T) signal indicated slow magnetic relaxation characteristic of single-chain magnets.
A bimetallic pentadecanuclear cyanido-bridged {Fe9[W(CN)8]6 (MeOH)24}·xMeOH cluster of an Fe(II/III)-W(IV/V) mixed valence nature, reveals a reversible single-crystal-to-single-crystal transformation, concomitant with metal-to-metal charge transfer between Fe and W ions. The dominance of (HS)Fe(II)-NC-W(V) units at a high temperature, and (HS)Fe(III)-NC-W(IV) units at a low temperature, leads to an unprecedented reversed thermal hysteresis loop in magnetic measurements.
Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), (SS/RR)-iPr-Pybox (2,6-bis[4-isopropyl-2-oxazolin-2-yl]pyridine) and (SRSR/RSRS)-Ind-Pybox (2,6-bis[8H-indeno[1,2-d]oxazolin-2-yl]pyridine), have been combined with lanthanide ions (Gd(3+), Nd(3+)) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN(-)-bridged coordination chains: {[Ln(III)(SS/RR-iPr-Pybox)(dmf)4]3[W(V)(CN)8]3}n ⋅dmf⋅4 H2O (Ln = Gd, 1-SS and 1-RR; Ln = Nd, 2-SS and 2-RR) and {[Ln(III)(SRSR/RSRS-Ind-Pybox)(dmf)4][W(V)(CN)8]}n⋅5 MeCN⋅4 MeOH (Ln = Gd, 3-SRSR and 3-RSRS; Ln = Nd, 4-SRSR and 4-RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200-450 nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the Gd(III)-W(V) chains show dominant ligand-based red phosphorescence, with λmax ≈660 nm for 1-(SS/RR) and 680 nm for 3-(SRSR/RSRS). The Nd(III)-W(V) chains, 2-(SS/RR) and 4-(SRSR/RSRS), exhibit near-infrared luminescence with sharp lines at 986, 1066, and 1340 nm derived from intra-f (4)F3/2 → (4)I9/2,11/2,13/2 transitions of the Nd(III) centers. This emission is realized through efficient ligand-to-metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [W(V)(CN)8](3-) moieties connected by cyanide bridges, 1-(SS/RR) and 3-(SRSR/RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between Gd(III) (SGd = 7/2) and W(V) (SW = 1/2) centers with J1-(SS) = -0.96(1) cm(-1), J1-(RR) =-0.95(1) cm(-1), J3-(SRSR) = -0.91(1) cm(-1), and J3-(RSRS) =-0.94(1) cm(-1). 2-(SS/RR) and 4-(SRSR/RSRS) display ferromagnetic coupling within their Nd(III)-NC-W(V) linkages.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.