Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

Trinuclear ruthenium core-containing polyoxometalate-based hybrids: preparation, characterization and catalytic behavior

Two ruthenium-containing polyoxometalate-based hybrids (Ru-POMs), KH8[Ru3O(Trz)6Cl3]2[(NaO6)W6(H2O)6(AsW9O33)4]·28H2O (1) and H3[Ru3O(Trz)6Cl3]2[(WO)2W(OH)(AsW9O33)2]·6H2O (2), (Trz = 1,2,4-triazole), were successfully isolated by a one-step hydrothermal method under different acidic conditions and further characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectroscopy, electrospray ionization and mass spectrometry (ESI-MS), thermogravimetric (TG) analyses and elemental analyses. Single-crystal X-ray diffraction analyses reveal two polyanions comprised of four/two identical trivacant Keggin-type polyanion building blocks, leading to the formation of tetrameric/dimeric assembly stabilized by additional metal-oxo cores, respectively. ESI-MS shows that the polyanion units [(NaO6)W6(H2O)6(AsW9O33)4]11- and [(WO)2W(OH)(AsW9O33)2]5- are intact in mixed solvent. Moreover, the two heterogeneous catalysts with trinuclear ruthenium cations were further investigated, and 1 was found to exhibit much higher yield (94.1%)/conversion (95.1%) and better selectivity (>99%) towards the oxidation of thioanisole to sulfoxide than 2.

Tellurotungstate-Based Organotin-Rare-Earth Heterometallic Hybrids with Four Organic Components

A family of unprecedented tellurotungstate-based organotin-rare-earth (RE) heterometallic hybrids [H₂N(CH₃)₂]₆H₁₂Na₂ {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂·25H₂O [RE = Ce^III (1), Pr^III (2), Nd^III (3), Sm^III (4), Eu^III (5), Gd^III (6), Tb^III (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(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂^20- of 1-7 are constructed from two symmetrical units {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}^10- 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^III cations, whereas during the emission procedure of 7, [B-α-TeW₈O₃₁]^10- 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 Tb³⁺ 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^III centers. Variable-temperature magnetic susceptibility measurements for 2, 3, and 4 were performed.

Synthesis and photo-/electro-catalytic properties of a 3D POMOF material based on an interpenetrated copper coordination polymer linked by in situ dual ligands and Dawson-type phosphotungstates

A 3D Keggin POMOF based on a unique Cu/pz/pzc MOF was prepared and employed to degradation of typical dyes.

19-Tungstodiarsenate(III) Functionalized by Organoantimony(III) Groups: Tuning the Structure-Bioactivity Relationship

A family of three discrete organoantimony(III)-functionalized heteropolyanions-[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)](10-) (1), [{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)](8-) (2), and [{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2](14-) (3)-have been prepared by one-pot reactions of the 19-tungstodiarsenate(III) precursor [As(III)2W19O67(H2O)](14-) with 2-(Me2NCH2)C6H4SbCl2. The three novel polyanions crystallized as the hydrated mixed-alkali salts Cs3KNa6[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)]·43H2O (CsKNa-1), Rb2.5K5.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)]·18H2O·Me2NCH2C6H5 (RbK-2), and Rb2.5K11.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2]·52H2O (RbK-3), respectively. The number of incorporated {2-(Me2HN(+)CH2)C6H4Sb(III)} units could be tuned by careful control of the experimental parameters. Polyanions 1 and 2 possess a dimeric sandwich-type topology, whereas 3 features a trimeric, wheel-shaped structure, representing the largest organoantimony-containing polyanion. All three compounds were fully characterized in the solid state via single-crystal X-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis, and their aqueous solution stability was validated by ultraviolet-visible light (UV-vis) and multinuclear ((1)H, (13)C, and (183)W) nuclear magnetic resonance (NMR) spectroscopy. Effective inhibition against six different types of bacteria was observed for 1 and 2, and we could extract a structure-bioactivity relationship for these polyanions.