An inorganic–organic hybrid supramolecular framework based on the γ-[Mo8O26]4− cluster and cobalt complex of aspartic acid: X-ray structure and DFT study

Supramolecular network of a framework material supported by the anion-π linkage of Keggin-type heteropolyoxotungstates: experimental and theoretical insights

A novel inorganic-organic hybrid, {Na[Tb(L)(H2O)4]3(SiW12O40)}·4H2O, in which L = 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid), was prepared and characterized by elemental analyses, Fourier transform infrared spectroscopy, and single-crystal X-ray diffraction. It consists of a trinuclear terbium cluster bonded to a Keggin-type polyoxotungstate. In the terbium cluster three crystallographically equivalent Tb3+ ions are bridged by carboxylate oxygen atoms belonging to three chelidamic acid units to form an equilateral triangle. These triangle units connect to each other through hydrogen-bonding and anion-π interactions. A CSD survey was carried out focusing on the cation and the ligand roles in the structure formation of this type of compounds. Finally, DFT calculations were used to analyse the role of the anion-π interactions that are important in the formation of 1D supramolecular assemblies in the solid state. The noncovalent interaction plot (NCIplot) computational tool has been used to characterize the anion-π interaction.

Crystal structure and photophysical properties of a novel polyoxomolybdate porphyrin

A novel polyoxomolybdate with a diprotonated porphyrin as counter-cation, namely, 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,22H,23H,24H-porphine(2+) hexamolybdate(VI) pentahydrate, (C₄₈H₃₂N₄O₈)[Mo₆O₁₉]·5H₂O or (H₂TCPP)[Mo₆O₁₉]·5H₂O, I, was prepared via the hydrothermal reaction of MoCl₅, 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,23H-porphine (TCPP) and distilled water. The crystal structure of hydrated polyoxometalate (POM) salt I was characterized by single-crystal X-ray diffraction. The compound is characterized by an isolated (zero-dimensional, 0D) structure, because it cannot extend via covalent bonds. The structure contains one [Mo₆O₁₉]^2- anion, one (H₂TCPP)²⁺ cation and five lattice water molecules. Each of the Mo⁶⁺ ions is six-coordinated and displays a distorted octahedral motif. The (H₂TCPP)²⁺ cation displays a distorted saddle motif. A three-dimensional (3D) supramolecular framework is formed via hydrogen-bonding interactions. The compound shows a red photoluminescence emission.

A redetermination of the crystal structure of the mannitol complex NH4[Mo2O5(C6H11O6)]·H2O: hydrogen-bonding scheme and Hirshfeld surface analysis

The redetermined structure [for the previous study, see: Godfrey & Waters (1975 ▸). Cryst. Struct. Commun. 4, 5-8] of ammonium μ-oxido-μ-[1,5,6-tri-hydroxy-hexane-2,3,4-tris-(olato)]bis-[dioxidomolybdenum(V)] monohydrate, NH4[Mo2(C6H11O6)O5]·H2O, was obtained from an attempt to prepare a glutamic acid complex from the [Co2Mo10H4O38]6- anion. Subsequent study indicated the complex arose from a substantial impurity of mannitol in the glutamic acid sample used. All hydrogen atoms have been located in the present study and the packing displays N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds. A Hirshfeld surface analysis was also performed.

Histidinium-Driven Chirality Control of Self-Assembled Hybrid Molybdenum Oxyfluorides

Exploring macroscopic chiral materials with extended structures has become an important and fundamental topic in chemistry. To systematically control the chirality of novel organic-inorganic frameworks, histidinium-based cationic structure-directing agents containing specific chiral information are introduced. In this way, two chiral compounds, [(l-hisH₂ )MoO₂ F₄ ]₃ ⋅H₂ O (L) and [(d-hisH₂ )MoO₂ F₄ ]₃ ⋅H₂ O (D), and an achiral oxyfluoride, (l/d-hisH₂ )MoO₂ F₄ (LD) (his=histidine, C₆ H₉ N₃ O₂ ) have been successfully self-assembled by a slow evaporation method. The structures of these compounds are composed of histidinium cations and distorted [MoO₂ F₄ ]^2- octahedra. Surprisingly, the histidinium cations not only control macroscopic chirality, but also induce O/F ordering in MoO₂ F₄ octahedra through hydrogen-bonding interactions. Compounds L and D crystallize in the extremely rare polar space group P1, and exhibit positive second harmonic generation (SHG) signals attributable to a net moment originating from the MoO₂ F₄ groups. Solid-state circular dichroism (CD) spectra indicate that the MoO₂ F₄ units templated by histidinium cations are chirally aligned through ionic interactions. Crystallization processes influenced by the chirality of the reported materials are also discussed herein.