Two Families of Rare-Earth-Substituted Dawson-type Monomeric and Dimeric Phosphotungstates Functionalized by Carboxylic Ligands

Abstract

Two series of novel organic–inorganic hybrid carboxylated rare-earth-substituted monolacunary Dawson-type phosphotungstate monomers [Hdap] ­[RE­(H2O)­(Hpic)3]­[RE­(Hpic)2 (α2-P2W17O61)]­·21H2O [RE = GdIII (1), TbIII (2), DyIII (3), HoIII (4), ErIII (5), TmIII (6), YbIII (7), YIII (8); Hpic = 2-picolinic acid, dap = 1,2-diaminopropane] and dimers [H2dap]8­[RE2(H2ox)2­(ox)­(α2-P2W17O61)2]­·25H2O [RE = HoIII (9), ErIII (10), TmIII (11), YbIII (12), YIII (13); H2ox = oxalic acid] have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, thermogravimetric measurements, and X-ray single-crystal diffraction. The monomeric polyoxoanion skeleton of isomorphic 1–8 is constructed from a monolacunary Dawson-type phosphotungstate implanted by a [RE1­(Hpic)2]3+ cation in the polar position and supported by the other [RE2(H2O)­(Hpic)3]3+ cation on the equatorial belt. Interestingly, two kinds of RE cations separately coordinate to two or three Hpic ligands in the form of N–C–C–O–RE containing five-membered ring fashion. The dimeric polyoxoanion backbone of isomorphic 9–13 is built by two mono-RE substituted Dawson-type phosphotungstate fragments [RE­(H2ox)­(α2-P2W17O61)]7– joined together by an ox2– linker. The visible photoluminescence spectra of solid-state 2, 3, 5, and 10 and the NIR photoluminescence properties for solid-state 5, 10, 7, and 12 at ambient temperature have been carried out, which are mainly derived from the RE3+ f–f electron transitions. Magnetic susceptibility measurements and fitting results of 3 demonstrate that 3 is a single-molecule magnet.

CeIII-Functionalized Polyoxotungstates: Discrete vs Extended Architectures

“…Both POT precursors, trilacunary [α-P 2 W 15 O 56 ] 12– and hexalacunary [α-P 2 W 12 O 48 ] 14– derivatives of the Wells-Dawson-type phosphotungstate [α-P 2 W 18 O 62 ] 6– , are not stable in aqueous solutions and in reactions with Ce III under the used conditions transform into the architectures based on the more stable monolacunary Wells-Dawson-type derivative [α 2 -P 2 W 17 O 61 ] 10– . This type of rearrangement is not unusual and was already observed several times during the synthesis of the previously reported Ln III complexes of {α 2 -P 2 W 17 }; ,,, however it is interesting to note that such transformation occurs in a rather wide pH range, from 2.5 to 6.0. Phenylphosphonic acid, PhPO 3 H 2 , was initially added to the reaction mixtures for preparation of 1 – 4 as a potential coligand to the POT precursors; however, it did not participate directly in formation of the complexes.…”

“…Other attempts to crystallize 1:1 complexes without organic coligands led to isolation of dimeric 2:2 − or cyclic trimeric 3:3 structures, where the Ln III ion of the {(H 2 O) n Ln III (α 1/2 -P 2 W 17 O 61 )} monomer binds to four oxygen atoms of the vacant site of the {P 2 W 17 } unit, to terminal aqua ligands as well as to a single terminal O center of a neighboring {(H 2 O) n Ln III (α 1/2 -P 2 W 17 O 61 )} moiety; this O site can belong either to the W VI from the {PW 6 } “belt” or to the W VI from the {LnW 2 } or {W 3 } “cap” of the {P 2 W 17 } unit. Other types of oligomerized 1:1 units comprise either acetate bridging ligands, as observed in the only dimeric derivative [{La­(CH 3 COO)­(H 2 O) 2 (α 2 -P 2 W 17 O 61 )} 2 ] 16– , or an oxalate bridge (ox 2– ), as reported for [Ln 2 (H 2 ox) 2 (ox)­(α 2 -P 2 W 17 O 61 ) 2 ] 8– (Ln = Ho III , Er III , Tm III , Yb III as well as Y III ) and [{Yb­(α 2 -P 2 W 17 O 61 )} 4 (ox) 3 (H 2 O) 4 ] 34– polyanions . Recently it was also shown that picolinic acid (Hpic) can stabilize 1:1 {α 2 -LnP 2 W 17 } species within the hybrid [Ln­(Hpic) 2 (α 2 -P 2 W 17 O 61 )] 7– polyanions decorated with an additional [Ln­(H 2 O)­(Hpic) 3 ] 3+ cation (Ln = Gd III , Tb III , Dy III , Ho III , Er III , Tm III , Yb III and Y III ) .…”

“…Other types of oligomerized 1:1 units comprise either acetate bridging ligands, as observed in the only dimeric derivative [{La­(CH 3 COO)­(H 2 O) 2 (α 2 -P 2 W 17 O 61 )} 2 ] 16– , or an oxalate bridge (ox 2– ), as reported for [Ln 2 (H 2 ox) 2 (ox)­(α 2 -P 2 W 17 O 61 ) 2 ] 8– (Ln = Ho III , Er III , Tm III , Yb III as well as Y III ) and [{Yb­(α 2 -P 2 W 17 O 61 )} 4 (ox) 3 (H 2 O) 4 ] 34– polyanions . Recently it was also shown that picolinic acid (Hpic) can stabilize 1:1 {α 2 -LnP 2 W 17 } species within the hybrid [Ln­(Hpic) 2 (α 2 -P 2 W 17 O 61 )] 7– polyanions decorated with an additional [Ln­(H 2 O)­(Hpic) 3 ] 3+ cation (Ln = Gd III , Tb III , Dy III , Ho III , Er III , Tm III , Yb III and Y III ) . In the other known hybrid, [{Ce­(η 1 -C 6 H 5 NO 2 ) 2 (H 2 O) 6 [Ce­(H 2 O) 3 (α 2 -P 2 W 17 O 61 )]} 2 {Ce­(η 2 -C 6 H 5 NO 2 ) 2 (H 2 O) 5 [Ce­(H 2 O)­(α 2 -P 2 W 17 O 61 )]} 2 ] 24– , isonicotinate groups help to stabilize a discrete tetramer built by the above-mentioned 2:2 dimer of {α 2 -LnP 2 W 17 } units each of which is decorated by an additional {α 2 -LnP 2 W 17 } moiety as well as Ce III centers with coordinated isonicotinate and aqua ligands …”

Nicotinic-Acid-Ornamented Tetrameric Rare-Earth-Substituted Phospho(III)tungstates with the Coexistence of Mixed Keggin/Dawson Building Blocks and Its Honeycomb Nanofilm for Detecting Toxins

“…Polyoxometalates (POMs) have aroused tremendous impetus, not only because of their fascinating structures but also on account of their multitudinous applications in medicine, magnetics, conductivity, photoluminescence, electrochemistry, and catalysis. − Phosphotungstates (PTs), a significant subset of POMs, have been an exciting and rapidly expanding area ascribed to their various types of derived precursors including [PW 9 O 34 ] 9– , [PW 11 O 39 ] 7– , [P 2 W 12 O 18 ] 14– , [P 2 W 15 O 56 ] 12– , [P 2 W 17 O 61 ] 10– , [P 5 W 30 O 110 ] 15– , and [P 8 W 48 O 184 ] 40– , which all could be readily obtained and could coordinate with rare-earth (RE) elements to form RE-substituted phosphotungstates (RESPTs). − One focus of RESPTs is the controlled fabrication of gigantic RESPT clusters with exquisite structures and physicochemical properties by making use of multiple coordination requirements and strong oxophilicity of RE cations. During the past two decades, some poly­(RESPT) clusters have been obtained via the preprepared phospho­(V)­tungstate precursors (Figure ).…”

Three Types of Distinguishing l-Alanine-Decorated and Rare-Earth-Incorporated Arsenotungstate Hybrids Prepared in a Facile One-Step Assembly Strategy

“…More importantly, these lacunary AT aggregates can serve as multidentate inorganic ligands and incorporate diverse transition-metal (TM) cations, giving rise to rapidly growing TM-substituted ATs (Figure S1c–d). − It should be pointed out that the flexible coordination ability and oxophilicity of rare-earth (RE) cations can make RE cations easily combine with different AT precursors to design and synthesize novel RE-containing ATs (RECATs). , Over the past two decades, great progress on RECATs has been made due to the versatile and ingenious assembly between AT fragments and RE linkers. − Some representative RECATs (Figure S1e–f) are demonstrated in the Supporting Information. − Obviously, most of those previously reported RECATs principally are purely inorganic; however, related reports on organic–inorganic RECAT hybrids remain underdeveloped. Recently, organic–inorganic hybrid RECATs have come to attract incremental attention because of the special functions that organic ligands can readily coordinate with RE or W atoms, bridge AT building blocks and RE centers together, and transfer their properties to the resulting compounds.…”