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Updated: Aug 6, 2026
Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
Published on: April 14, 2020
Chiral Networks Assembled from Hexalanthanide Polyoxometalate Sandwich Building Units Showing Solid-State
Vanikrishna Ajithkumar Njayappallil1, Aravind Raveendranathan2, Senthil Kumar Kuppusamy3
1Institute of Inorganic Chemistry (AOC), Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, Karlsruhe76131, Germany.
Abstract:
A new series of all-inorganic lanthanide-containing polyoxometalate (Ln-POM) hybrid clusters, Na5[{Ln6(μ3-OH)3(H2O)9}{SiW9O34}2]·50H2O (1-Ln; Ln3+ = Pr, Nd, Sm, Eu, Gd), featuring a rare 6:2 lanthanide-to-POM motif, has been synthesized. The clusters consist of a hexanuclear {Ln6(μ3-OH)3(H2O)9}15+ unit sandwiched between two achiral trilacunary {A-α-SiW9O34}10- polyanions. Each unit is bridged to three neighboring clusters via Ln-O-W bonds, forming a robust three-dimensional chiral network with srs topology, crystallizing in the cubic I213 space group. Electrospray ionization mass spectrometry studies confirm intact polyanions in variable charge states. The solid-state temperature-dependent photoluminescence studies of 1-Eu reveal the characteristic Eu3+-centered 5D0 → 7FJ (J = 0-4) emissions sensitized via ligand-to-metal charge transfer (LMCT, O→W, 334 nm) transition and direct 4f-4f excitation (5L6 ← 7F0, 396 nm). At 300 K, the LMCT absorption is quenched, and the emission is induced upon direct 4f-4f excitation. The temperature-dependent evolution of the 5D0 → 7F0 transitions underscores the utility of Eu3+ emission as a sensitive probe of site symmetry and dynamic structural modulations. These results highlight the potential of the trilacunary POM {A-α-SiW9O34}10- as an all-inorganic achiral ligand for stabilizing high-nuclearity, light-emissive lanthanide-based sandwich clusters forming a chiral network.
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