Journal
INORGANIC CHEMISTRY
Volume 61, Issue 5, Pages 2428-2443Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.inorgchem.1c03214
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Funding
- Eusko Jaurlaritza/Gobierno Vasco (EJ/GV) [IT1291-19, KK-2020/00008]
- Ministerio de Ciencia e Innovacion (MCIN) [MAT2017-89553-P]
- EJ/GV [PRE_2018_1_0143]
- MCIN/AEI/FEDER Una manera de hacer Europa [PGC2018 102052-B-C21]
- I +D+i FEDER program 2018 of Junta de Andalucia [A-FQM-172-UGR18]
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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 [alpha-SiW11O39](8-) anion affords a series of isostructural compounds, which display sandwich-type molecular structure and chairlike crystal packing. 1-Gd and 1-Yb exhibit slow relaxation of the magnetization and near-infrared emission, while the metal-centered luminescence in 1-Tb is quenched.
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 [alpha-SiW11O39](8-) anion affords a series of isostructural compounds, namely, K-5[Ln(III)(alpha-SiW11O39)(C20H22Br2N2O4)]center dot 14H(2)O (1-Ln, Ln = Sm to Lu). The molecular structure of these sandwich-type complexes is formed by the LnIII 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 N2O2 coordination site of the organic ligand allows its unprecedented folding, which displays a relative perpendicular arrangement of aromatic groups. Weak Br center dot center dot center dot Br and pi-pi 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 similar to 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.
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