Abstract
One of the pathways toward luminescent single-molecule magnets (SMMs) is realized by the self-assembly of lanthanide(3+) ions with cyanido transition metal complexes. We report a novel family of emissive SMMs, {YbIII(4-pyridone)4[FeII(phen)2(CN)2]2}(CF3SO3)3·solv (solv = 2MeCN, 1·MeCN; 2AcrCN, 1·AcrCN; 2PrCN, 1·PrCN; 2MalCN·1MeOH; 1·MalCN; MeCN = acetonitrile, AcrCN = acrylonitrile, PrCN = propionitrile, MalCN = malononitrile). They are based on paramagnetic YbIII centers coordinating diamagnetic [FeII(phen)2(CN)2] metalloligands but differ in the nitrile solvents of crystallization. They exhibit a field-induced slow magnetic relaxation dominated by a Raman process, without an Orbach relaxation as indicated by AC magnetic data and the ab initio calculations. The Raman relaxation is solvent-dependent as represented by the power “n” of the BRamanTn contribution varying from 3.07(1), to 2.61(1), 2.37(1), and 1.68(4) for 1·MeCN, 1·PrCN, 1·AcrCN, and 1·MalCN, respectively, while the BRaman parameter adopts the opposite trend. This was correlated with the variation of phonon modes schemes, including the number of available vibrational modes and their energies, dependent on the increasing complexity of the applied nitrile. 1·MeCN and 1·MalCN show the additional T-independent relaxation assignable to dipole-dipole interactions as confirmed by its suppression in 1·AcrCN and 1·PrCN revealing longer Yb–Yb distances and the disappearance in the LuIII-diluted 1·MeCN@Lu. All compounds exhibit YbIII–centered near-infrared photoluminescence sensitized by organic ligands.
Highlights
Extensive scientific interest in novel functional materials is driven by the necessity of ensuring the development of hi-tech magnetic, optical, or electronic devices [1,2,3,4,5]
They combine sensitized NIR YbIII emission with slow magnetic relaxation characterized by a Raman relaxation process sensitive to the type of nitrile solvent which was investigated by structural X-ray diffraction methods, AC magnetic data supported by the ab initio calculations, and solid-state photoluminescence experiments
The composition of {YbIII (4-pyridone)4 [FeII2 (CN)2 ]2 }(CF3 SO3 )3 ·2MeCN was determined by a single-crystal X-ray diffraction (SC-XRD) experiment, while the phase purity was proven by a powder X-ray diffraction (P-XRD) method (Figure S13), all supported by the results of CHNS elemental analysis, IR spectroscopy, and thermo- gravimetric (TG)
Summary
Extensive scientific interest in novel functional materials is driven by the necessity of ensuring the development of hi-tech magnetic, optical, or electronic devices [1,2,3,4,5]. Cyanido transition metal complexes, that can efficiently transfer the energy to NIR–emissive lanthanides [49,50], can be used as advanced metalloligands for NIR-emissive SMMs [51,52,53,54] In this context, we are continuously developing the idea of luminescent molecular magnets that can be achieved by inserting lanthanide ions into polycyanidometallate-based coordination systems. We report the structures as well as the magnetic and optical properties of novel molecular materials ({YbIII (4-pyridone)4 [FeII (phen) (CN)2 ]2 }(CF3 SO3 )3 ·solv (solv = 2MeCN in 1·MeCN, 2AcrCN in 1·AcrCN, 2PrCN in 1·PrCN, and 2MalCN·1MeOH in 1·MalCN, where MeCN = acetonitrile, AcrCN = acrylonitrile, PrCN = propionitrile, MalCN = malononitrile, and MeOH = methanol), composed on trinuclear {YbFe2 } molecules crystallized with four different nitrile solvents of crystallization They are the first examples of NIR-emissive lanthanide-based molecular nanomagnets exploring the metalloligand application of dicyanido iron(II) complexes. They combine sensitized NIR YbIII emission with slow magnetic relaxation characterized by a Raman relaxation process sensitive to the type of nitrile solvent which was investigated by structural X-ray diffraction methods, AC magnetic data supported by the ab initio calculations, and solid-state photoluminescence experiments
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