Slow Magnetic Relaxation and Luminescent Properties of Mononuclear Lanthanide-Substituted Keggin-Type Polyoxotungstates with Compartmental Organic Ligands

Abstract

The reaction of mid to late lanthanide ions with the N , N ′-dimethyl- N , N ′-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylene-diamine organic ligand and monolacunary Keggin type [α-SiW 11 O 39 ] 8– anion affords a series of isostructural compounds, namely, K 5 [Ln III (α-SiW 11 O 39 )(C 20 H 22 Br 2 N 2 O 4 )]·14H 2 O ( 1 -Ln, Ln = Sm to Lu). The molecular structure of these sandwich-type complexes is formed by the Ln III ion in a biaugmented trigonal prismatic geometry, which occupies the external O 4 site of the organic ligand and the vacant site of the lacunary polyoxometalate (POM) unit. The empty N 2 O 2 coordination site of the organic ligand allows its unprecedented folding, which displays a relative perpendicular arrangement of aromatic groups. Weak Br···Br and π–π interactions established between adjacent molecular units govern the crystal packing, which results in the formation of assemblies containing six hybrid species assembled in a chairlike conformation. 1 -Gd and 1 -Yb display slow relaxation of the magnetization after the application of an external magnetic field with maxima in the out-of-phase magnetic susceptibility plots below ∼5–6 K, which is ascribed to the presence of various relaxation mechanisms. Moreover, photoluminescent emission is sensitized for 1 -Sm and 1 -Eu in the visible region and 1 -Er and 1 -Yb in the NIR. In contrast, the quenching of metal-centered luminescence in the 1 -Tb derivative has been attributed to the out-of-pocket coordination mode of the lanthanide center within the POM fragment. It is demonstrated that the 1 -Yb dual magneto-luminescent material represents the first lanthanide-containing POM reported to date with simultaneous slow magnetic relaxation and NIR emission. Solution stability of the hybrid molecular species in water is also confirmed by ESI-mass spectrometry experiments carried out for 1 -Tb and 1 -Tm.

Mono- and Rare Trinuclear Zn(II) Complexes with Near-Infrared Emissive Ligands: Anion-Responsive Nuclearity Control, Interconversion, Solid-State NIR Emission, and Latent Fingerprint Imaging

“…All these bond distances and angles agree with the literature reports. The degree of distortion of the Zn coordination polyhedra in M1–M3 was analyzed by continuous shape measures (CShM) using the SHAPE program. − The calculated CShM values for M1–M3 are in the range of 17.89–29.15 and 1.30–12.86 for the reference geometries square planar and tetrahedral, respectively (Table S11, Supporting Information). These values further confirmed that the Zn polyhedra in M1–M3 are closer to tetrahedral geometry than the square-planar geometry.…”

“…These bond distances and angles are in agreement with the literature reports. , Similar bond lengths and bond angles are also exhibited by T2 and T3 , which are given in Tables S5 and S6, Supporting Information. The degree of distortion of the Zn coordination polyhedra in T1–T3 was also calculated using the SHAPE program. − The CShM values obtained for the six coordinated Zn centers using the reference shapes octahedron and trigonal prism were in the range of 0.45–0.56 for the octahedron and 13.87–15.02 for the trigonal prism. These values suggest that the polyhedra around the six coordinated Zn centers in these complexes are closer to the octahedron than the trigonal prism.…”

Multifunctional LnIII complexes with SMM, luminescence and MCE properties constructed using selected phosphine oxide and diketonate

“…S15, ESI†). 44 An exponent equal to 2 is theoretically expected for this phonon-bottleneck phenomenon, 42 suggesting that this mechanism could be responsible for the slow magnetic relaxation observed in 4 .…”

“…While this is not unexpected for the Gd III congeners, there have been similar reports related to this phenomenon. 41,42 In this case, the analysis of the temperature dependence of the relaxation time was performed assuming a t À1 = CT n dependence. The slow relaxation is not attributed to an anisotropy barrier, but to the phonon-bottleneck effect originated by the trapping of resonant phonons that are unable to release the energy of the spin bath to the thermal.…”

Heteropoly Blue/Carbon Nanotubes Nanocomposites as High‐Performance Photothermal Conversion Materials

“…Some works have been reported on the application of heteropoly blue (HPB) in the field of photothermal conversion, such as photothermal therapy [14][15][16][17] and photothermal catalysis. [18] In 2019, Wang et al applied the prepared CuOÀ PMo 12 ultrathin nanosheets for the first time to study the performance of photothermal water evaporation.…”