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Polyoxometalates (POM), as inorganic polydentate oxygen donors, provide binding opportunities for oxophilic lanthanide metal centers to construct novel Ln-substituted POM materials with exciting structures and attractive properties. Herein, we have reported four arsenotungstate [α-AsW9O33]9− based lanthanide-containing polyoxometalates [CsxK36–x{Ln6(H2O)12(α-AsW9O33)6}]·yH2O (Ln = Er (1), Gd (2), Ho (3), and Tb (4)), which are synthesized in an alkaline medium. Complexes 1–3 are the dimeric structures of [Ln3(H2O)6(α-AsW9O33)3]18− polyanions, whereas complex 4 is a hexamer of the polyanion [Tb (H2O)2(α-AsW9O33)]6− as a building unit. In all the complexes, [α-AsW9O33]9− units are staggered up and down and give rise to the chair conformation, where one [α-AsW9O33]9− unit bridges two Ln(III) centers through four μ2-oxygen and two terminal oxygen atoms, resulting in the hexagonal arrangement of lanthanides. The dynamic magnetic measurement indicates that only complex 1 exhibits slow relaxation of magnetization with an applied dc field (1500 Oe). To gain insight into the slow relaxation of magnetization in complex 1, the ligand-field parameters and the splitting of the ground-state multiplet of the Er(III) ions have been estimated. The ab initio calculation results confirm that the ground state wave function of these molecules (1, 3, and 4) is mainly composed of a mixture of mJ states, and the non-axial crystal field (CF) terms are more predominant than the axial CF term. The solid-state fluorescence spectra of 1–4 reveal that the photoexcitation O → M ligand-to-metal charge-transfer (LMCT) of arsenotungstate fragments is effectively quenched due to the spatial coordination environment around the Ln(III) ion. [ABSTRACT FROM AUTHOR]

Two polynuclear, mixed-valence, sandwich dodecanuclear manganese clusters [MnII4MnIII4MnII4(μ4-O)2(μ3-O2CH)2(thme)4(MeCO2)10(H2O)4]·4H2O (1) and [MnII4MnIII4MnII4(μ4-O)2(μ3-O)2(thmp)4(MeCO2)10(H2O)4]·10H2O (2) are reported by the reaction of 1,1,1-tris(hydroxymethyl)ethane (H3thme) or 1,1,1-tris(hydroxymethyl)propane (H3thmp) with manganese(II) salts in methanol under reflux conditions. 1 and 2 were characterized by single-crystal X-ray diffraction, PXRD, cyclic voltammetry (CV), and variable temperature magnetic studies. 1 and 2 crystallize in the monoclinic (P21/n) and triclinic (P-1) systems, respectively, and each structure consists of a dodecanuclear mixed-valent sandwich core. Magnetic data confirmed that both complexes show dominant antiferromagnetic interactions between metal centers. The fascinating features of the non-covalent supramolecular contacts have been explored. The interplay of O⋯H interactions (i.e. O-H⋯O and C-H⋯O contacts) gives rise to the consolidation of discrete units of 1 and 2 into supramolecular architecture. Catecholase activity data show that the present clusters catalyze the oxidation of 3,5-DTBC to 3,5-DTBQ with efficient Kcat values. [ABSTRACT FROM AUTHOR]

Apart from traditional metal–organic frameworks as sensory materials, materials incorporating discrete cages or clusters to sense hazardous species are uncommon. Keeping this view in mind, a new hybrid discrete material comprising a decavanadate anion and copper complex cations was designed for such a purpose. Consequently, a novel polyoxovanadate (POV)-based inorganic–organic hybrid compound showing a unique combination of first anagostic (V…H) interactions was synthesized. Single-crystal X-ray data ascertained the bonding modes and geometry of the complex along with the novel anagostic weak intermolecular interactions in the complex material. X-ray crystallography confirmed the composition of the cluster as {Cu(Pyno)4}{NEt3H}2[H2V10O28] (1), containing a decavanadate unit as the anion with a square planar copper(ii) complex and triethylaminium as the cations. The complex was further characterized by FT-IR, time decay and magnetic studies. The magnetic studies confirmed the presence of the Cu2+ state in the complex at room temperature as well as at low temperature. The cluster displayed rare intermolecular V…H, lp…π, V–O…H, π…π and C–H…H interactions, which generated a supramolecular framework. These interactions were verified by Hirshfeld surface analyses. The hybrid material is reported herein as the first aqueous-phase sensor for picric acid (PA) as well as for Pd2+. The complex showed a highly sensitive, discriminative and selective sensing behaviour for the said species and is the first reported example of its type in this discrete molecular category. The sensing pathways were investigated by spectral titrations, and by time decay and DFT (B3LYP/def2-SVP) studies. The lowest detection limit was discovered for the present POV towards the sensing of both PA and Pd2+ ions with values of ∼0.18 and ∼0.80 ppb, respectively. [ABSTRACT FROM AUTHOR]

Two new trinuclear Cu(ii) and dinuclear Zn(ii) clusters are crystallized out by reacting the metal salts with the triethanolamine (H3tea) ligand in the presence of benzoic acid (Hba). The complexes are characterized by elemental, thermal, magnetic, spectral (FTIR, UV-Visible, EPR, and photoluminescence) and single crystal X-ray studies. Single crystal X-ray crystallography reveals the composition of the complexes to be [Cu3(H2tea)2(ba)2(NO3)2] (1) and [Zn2(H2tea)(ba)3]H2O (2). FTIR ascertains the binding modes of H2tea−, ba− and NO3−. Triethanolamine binds in both the complexes in the monoanionic (H2tea−) mode. ba− is present as an anchoring auxiliary to generate di- and trinuclear clusters. The Cu(ii) ion is present as a distorted octahedral center in the Cu3 cluster (1), while the two Zn(ii) ions in 2 have been reported for the first time to possess distorted octahedral as well as tetrahedral geometry in the same molecule. The intriguing features of the non-covalent supramolecular interactions have been investigated and supported theoretically by using Hirshfeld surface analysis and ab initio methods. The solid state photoluminescence (PL) spectra of 1 and 2 disclose the luminescence property of the complexes. Due to the closed or nearly closed shell configuration (d9 or d10), the present complexes are screened for catalytic properties in the hydrocarboxylation of alkanes and cycloalkanes. The catalytic activity data are indicative of the potential catalytic properties of 1 and 2. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POM), as inorganic polydentate oxygen donors, provide binding opportunities for oxophilic lanthanide metal centers to construct novel Ln-substituted POM materials with exciting structures and attractive properties. Herein, we have reported four arsenotungstate [α-AsW 9 O 33 ] 9- based lanthanide-containing polyoxometalates [Cs x K 36- x {Ln 6 (H 2 O) 12 (α-AsW 9 O 33 ) 6 }]· y H 2 O (Ln = Er (1), Gd (2), Ho (3), and Tb (4)), which are synthesized in an alkaline medium. Complexes 1-3 are the dimeric structures of [Ln 3 (H 2 O) 6 (α-AsW 9 O 33 ) 3 ] 18- polyanions, whereas complex 4 is a hexamer of the polyanion [Tb (H 2 O) 2 (α-AsW 9 O 33 )] 6- as a building unit. In all the complexes, [α-AsW 9 O 33 ] 9- units are staggered up and down and give rise to the chair conformation, where one [α-AsW 9 O 33 ] 9- unit bridges two Ln(III) centers through four μ 2 -oxygen and two terminal oxygen atoms, resulting in the hexagonal arrangement of lanthanides. The dynamic magnetic measurement indicates that only complex 1 exhibits slow relaxation of magnetization with an applied dc field (1500 Oe). To gain insight into the slow relaxation of magnetization in complex 1, the ligand-field parameters and the splitting of the ground-state multiplet of the Er(III) ions have been estimated. The ab initio calculation results confirm that the ground state wave function of these molecules (1, 3, and 4) is mainly composed of a mixture of m J states, and the non-axial crystal field (CF) terms are more predominant than the axial CF term. The solid-state fluorescence spectra of 1-4 reveal that the photoexcitation O → M ligand-to-metal charge-transfer (LMCT) of arsenotungstate fragments is effectively quenched due to the spatial coordination environment around the Ln(III) ion.

Design, synthesis, and applications of metal-organic frameworks (MOFs) are among the most salient fields of research in modern inorganic and materials chemistry. As the structure and physical properties of MOFs are mostly dependent on the organic linkers or ligands, the choice of ligand system is of utmost importance in the design of MOFs. One such crucial organic linker/ligand is terpyridine (tpy), which can adopt various coordination modes to generate an enormous number of metal-organic frameworks. These frameworks generally carry physicochemical characteristics induced by the π-electron-rich (basically N-electron-rich moiety) terpyridines. In this minireview, the construction of 3D MOFs associated with symmetrical terpyridines is discussed. These ligands can be easily derivatized at the lateral phenyl (4'-phenyl) position and incorporate additional organic functionalities. These functionalities lead to some different binding modes and form higher dimensional (3D) frameworks. Therefore, these 3D MOFs can carry multiple features along with the characteristics of terpyridines. Some properties of these MOFs, like photophysical, chemical selectivity, photocatalytic degradation, proton conductivity, and magnetism, etc. have also been discussed and correlated with their frameworks., (© 2020 Wiley-VCH GmbH.)