A family of unprecedented tellurotungstate-based organotin-rare-earth (RE) heterometallic hybrids [HN(CH)]HNa {[Sn(CH)WO(IN)][(B-α-TeWO)RE(HO) (Ac)]}·25HO [RE = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7); HIN = isonicotinic acid, HAc = acetic acid] were synthesized and characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. The polyoxoanionic skeletons {[Sn(CH)WO(IN)][(B-α-TeWO)RE(HO) (Ac)]} of 1-7 are constructed from two symmetrical units {[Sn(CH)WO(IN)][(B-α-TeWO)RE(HO) (Ac)]} linked by two acetate connectors, which not only represent the first inorganic-organic hybrid RE-substituted tellurotungstates involving three different organic ligands, but also stand for the first samples of organotin-RE heterometallic polyoxometalate derivatives. The solid-state luminescent emission properties of 2-5 mainly display the characteristic emission bands of RE cations, whereas during the emission procedure of 7, [B-α-TeWO] segments make a nonignorable contribution to the PL behavior of 7 accompanying by the occurrence of the intramolecular energy transfer from O→W LMCT energy to Tb centers. Furthermore, 4@CTAB composites with peanutlike and honeycombed morphologies were prepared by a surfactant cetyltrimethylammonium bromide (CTAB). The time-resolved emission spectra of the 4@CTAB composite with CTAB/4 = 0.033/0.05 consolidate the energy transfer from CTAB to RE centers. Variable-temperature magnetic susceptibility measurements for 2, 3, and 4 were performed.
A series of organic-inorganic rare-earth-incorporated tellurotungstate hybrids, Na[RE(HO)(pica)WO][(RE(HO)W(Hpica)O)(B-β-TeWOH)]·38HO (RE = La (1), Ce (2), Nd (3), Sm (4), Eu (5); Hpica = 2-picolinic acid), were prepared via a one-step assembly reaction of NaWO·2HO, RE(NO)·6HO, KTeO, Hpica, and triethylamine (tea). Notably, the solubilization of tea toward Hpica and the solubilization of Hpica toward RE cations in the reaction system play an important role in the formation of 1-5. The most significant feature of 1-5 consists of an intriguing tetrameric [RE(HO)(pica)WO][(RE(HO)W(Hpica)O)(B-β-TeWOH)] polyoxoanion constructed from two tetravacant Keggin sandwich-type [(RE(HO)W(Hpica)O)(B-β-TeWOH)] entities linked by a RE-W-Hpica {RE(HO)(pica)WO} cluster, in which Hpica ligands not only play a key bridging role in linking RE and W centers by carboxylic groups in an irregular N-O-RE-O-W-O six-membered-ring motif but also can directly chelate with W centers via N and O atoms in a stable N-O-C-O-W five-membered-ring fashion. 1-5 represent rare organic-inorganic hybrid RE-substituted tellurotungstates. Moreover, the solid-state photoluminescence properties of 3-5 have been deeply investigated, and these compounds exhibit the characteristic emission stemming from intra-4f transitions of RE ions. The energy transfer of the O → W transitions sensitizing the emission of Sm centers in 4 is convincingly proved by time-resolved emission spectra (TRES); the increase in the strongest typical emission of Sm ions at a decay time of 17 μs is accompanied by the decline of O → W emission, and the CIE 1931 diagram was obtained from the corresponding TRES. Furthermore, a comparison of the luminescence behaviors of 5 in the solid state and in solution reveals the structural skeletal integrity of 5 in solution and a shorter decay lifetime in the solution caused by the high-frequency O-H oscillators.
A class of novel organic-inorganic hybrid lanthanide (Ln)-substituted Keggin-type borotungstates KNaH[Ln(gly)(α-BWO)]·23HO [Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Tm (6); gly = glycine] have been synthesized from the reaction of K[BWOH]·13HO, NaAc·6HO and Ln(NO)·6HO by employing gly ligands as structure-stabilizing agents in the conventional aqueous solution system and structurally characterized by elemental analyses, IR spectroscopy, thermogravimetric (TG) analyses, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. The common prominent structural feature of isomorphic 1-6 is that all of them consist of two mono-Ln-substituted Keggin [Ln(α-BWO)] fragments linked by four gly ligands, furnishing an intriguing dimeric assembly of the quadruple-gly-connective mono-Ln-substituted borotungstate, in which each carboxylic oxygen atom from gly ligands is bound to Ln cations in the μ-O or μ-O mode. To the best of our knowledge, 1-6 represent the first examples of inorganic-organic hybrid Ln-substituted borotungstates functionalized by quadruple amino acid bridges. The solid-state photoluminescence properties of 3-5 have been determined at ambient temperature and the photoluminescence emission spectra exhibit the characteristic emission bands derived from Ln centers. The thermostability of 1-6 has been studied and the thermal decomposition procedure of 3 has been comprehensively investigated with the assistance of variable-temperature PXRD patterns and variable-temperature IR spectra. Furthermore, magnetic susceptibility measurements of 1, 2 and 4 have been conducted.
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