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The double-eight-ring (D8R), an elusive secondary building unit of zeolites, has been stabilized for the first time, both in solution and solid-state. The present study further establishes that any of the three double-ring building blocks of zeolites, viz. D4R, D6R and D8R ([ArPO3Zn(L)]n (n = 4, 6 or 8)), can be preferentially isolated (over the other two) through a careful choice of metal source, aryl phosphate and ancillary ligand, apart from maintaining a meticulous control on the reaction conditions. [ABSTRACT FROM AUTHOR]

Four new alkaline-earth metal-based metal–organic frameworks, [Mg4(TCMTB)2(OAc)2(DMA)2(H2O)3]n (Mg-TCMTB), {[Ca4(TCMTB)2(OH)(DMF)2(H2O)5]·Cl}n (Ca-TCMTB), [Sr4(TCMTB)2(OH)(OAc)(DMA)6(H2O)]n (Sr-TCMTB) and [Ba9(TCMTB)4(NO3)6(DMA)14]n (Ba-TCMTB) (H3TCMTB = 2,4,6-tris[(4′-carboxyphenoxy)methyl]-1,3,5-trimethylbenzene), have been synthesized and structurally characterized. Structural analysis of the MOFs reveals the presence of diverse structures and topologies in these systems due to the conformational flexibility and multiple coordination sites in H3TCMTB. Coordination polymers Mg-TCMTB, Ca-TCMTB and Ba-TCMTB MOFs are three-dimensional frameworks exhibiting 2-fold interpenetration and one-dimensional hexagonal channels, while Sr-TCMTB is a 2-fold interpenetrated layered MOF. The 2D layers in Sr-TCMTB are interconnected through H–O…H hydrogen bonds. Increasing ionic radii and coordination number on moving down the group results in the formation of bi-, tetra- and nona-nuclear M–O–M connected inorganic building units. Owing to its smaller size and lower coordination number, framework Mg-TCMTB gives rise to a moderate surface area of 33.0 m2 g−1 (SABET) and 93.8 m2 g−1 (SALang) which is the highest observed among all the four MOFs. Emission studies of the new MOFs reveal the presence of strong photoluminescence at 380 nm. [ABSTRACT FROM AUTHOR]

The reaction of Zn(OAc)2 ·2H2O with tert-butyl phosphonic acid ( tBuPO3H2) yields the zinc phosphonate [Zn( tBuPO3)(H2O)] ·H2O ( 1). X-ray diffraction studies reveals that compound 1 has a novel layered structural arrangement with the central zinc atoms in a tetrahedral coordination environment. This observation emphasizes the crucial role played by organic substituents on the coordination chemistry of phosphonic acid with transition metal ions. [ABSTRACT FROM AUTHOR]

Abstract: Titanocene dichloride reacts with 2,6-diisopropylphenyl phosphate (dippH2) in tetrahydrofuran to yield a functionalized mononuclear titanium phosphate molecule [Cp2Ti(dippH)2] (1) in 70% yield. A similar reaction with titanium bis(acetylacetonate)diisopropoxide [Ti(acac)2(O i Pr)2] yields a tetranuclear cluster [Ti4(μ 2-OH)2(O i Pr)2(dipp)4(dippH)4(THF)2] (2) in 70% yield. Owing to the presence of free P–OH groups in 1, its reactivity towards aluminum alkyls has been investigated. Compounds 1 and 2 have been characterized with the aid of elemental analysis, mass, IR and NMR (1H and 31P) spectroscopy. In spite of the poor quality of the crystals obtained, the solid-state structures of compounds 1 and 2 have been determined by single crystal X-ray diffraction studies to a satisfactory level. Compound 1 crystallizes as hydrogen bonded chiral helical superstructures in the monoclinic non-centrosymmetric P21 space group. Compound 2 is a discrete tetranuclear titanophosphate cluster which is held together by eight phosphate ligands. [Copyright &y& Elsevier]

The geometries and electronic structure of molecular ions containing helium (He) atoms complexed to sodium (Na), magnesium (Mg) and aluminium (Al) cations have been studied computationally using density functional and wavefunction-based methods. The complexation of He atoms depends on the charge on the metal centre. While complexation with Na+ and Mg2+ is very weak, that with Al3+ is found to be strong. The highest coordination number (N) for AlHe3+N is found to be 11, which is a true minimum in the potential energy surface. Topological analysis within the realm of quantum theory of atoms in molecules reveals closed-shell interaction in these systems. [ABSTRACT FROM AUTHOR]

Double-4-ring zinc phosphate (D4R), [Zn(dipp)(4-Py-CHO)] 4 (2) (dipp=diiminopyridine), bearing four formyl groups, has been utilized as a building block (SBU) for the synthesis of a new class of imine-linked [4+2] COF-like polycrystalline zinc phosphate frameworks. Reactions of 2 with a series of linear aromatic diamines results in the formation of polycrystalline frameworks [Zn 4 (dipp) 4 (L) 2 ] n (3-6) (L=L 1 to L 4 , diimines formed by condensation of 4-pyridine carboxaldehyde with diamines). Employing an alternative synthetic strategy, through a diffusion-controlled slow reaction of 2 with the pre-synthesized 4,4'-bispyridyl bisimine (L 3 ), [Zn 4 (dipp) 4 (L 3 ) 2 ] n (5') has been obtained as single crystals. Complex 5' is a 3D-framework, exhibiting a rare eightfold interpenetrated diamondoid network. The long spacer length (19.6 Å) results in extensive entanglement in 5'. Powder diffraction data suggest that these compounds are isoreticular 3D-frameworks. To study the effect of the relative position of pyridyl donors with respect to the central benzidine moiety, 3,3'-bispyridyl bisimine (L 5 ) was investigated as the spacer. A slow reaction of 1 b with L 5 leads to the isolation of a 2D-boxed-sheet coordination polymer [Zn 4 (dipp) 4 (L 5 ) 2 ] n (7). Selective formation of 3D-framework 5' from L 3 and the 2D-framework 7 from L 5 is due to the angles created by the coordination of para- and meta-pyridyl nitrogen centers at the zinc centers of the D4R cubane. Compound 5' has been utilized as a catalyst for Knoevenagel condensation., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

[Ti(acac) 2 (O i Pr) 2 ] reacts with tert-butylphosphonic acid to yield a series of titanium organophosphonates such as tetranuclear [Ti 4 (acac) 4 (μ-O) 2 (μ- t BuPO 3 ) 2 (μ- t BuPO 3 H) 4 ]·2CH 3 CN (1), pentanuclear [Ti 5 (acac) 5 (μ-O) 2 (O i Pr)(μ- t BuPO 3 ) 4 (μ- t BuPO 3 H) 2 ] (2), hexanuclear [Ti 6 (acac) 6 (μ-O) 2 (O i Pr) 2 (μ- t BuPO 3 ) 6 ] (3), or [Ti 6 (acac) 6 (μ-O) 3 (O i Pr)(μ- t BuPO 3 ) 5 (μ- t BuPO 3 H)]·2CH 3 CN (4). The isolation of each of these products in pure form depends on the molar ratio of the reactants or the solvent medium. Among these, 3 is obtained as the only product when the reaction is conducted in CH 2 Cl 2 . The structural analysis reveals that a simple cluster growth route relates the clusters 1-4 to each other and that a reactive cyclic single-4-ring titanophosphonate [Ti(acac)(O i Pr) 2 ( t BuPO 3 H)] 2 is the fundamental building block. While the tetranuclear 1 has structural resemblance to the D4R building block of zeolites, the hexanuclear clusters 3 and 4 have the shape of zeolitic D6R building blocks. The presence of adventitious water in the phosphonic acid (arising from small quantities of hydrogen-bonded water) results in the formation of μ-O 2- bridges across an adjacent pair of titanium centers in clusters 1-4. To further verify the stability of the hexanuclear cluster over other structural forms, the reaction of t BuPO 3 H 2 was performed with [Ti(acac) 2 (O)], instead of Ti(acac) 2 (O i Pr) 2 , in CH 3 CN to yield [Ti 6 (acac) 6 (μ-O) 4 (μ- t BuPO 3 ) 4 (μ- t BuPO 3 H) 2 ]·2CH 3 CN (5). Compound 5 exhibits a core structure similar to those of 3 and 4 with small variations in the intracluster Ti-O-Ti linkage. Compound 3 is an efficient and selective catalyst for olefin epoxidation under both homogeneous and heterogeneous conditions.

Reaction of Zn(OAc)2 ⋅2 H2 O with 2,6-diisopropylphenyl phosphate (dippH2 ) in the presence of pyridine-4-carboxaldehyde (Py-4-CHO) in methanol resulted in the isolation of a tetrameric zinc phosphate cluster [Zn(dipp)(Py-4-CH(OH)(OMe))]4 ⋅4 MeOH (1) with four hemiacetal moieties stabilized on the double-4-ring inorganic cubane cluster. The change of solvent from methanol to acetonitrile leads to the formation of [Zn(dipp)(Py-4-CHO)]4 (2), in which the coordinated Py-4-CHO retains its aldehydic form. Dissolution of 1 in CD3 CN readily converts it to the aldehydic form and yields 2. Similarly 2, which exists in the aldehyde form in CD3 CN, readily converts to the hemiacetal form in CD3 OD/CH3 OH. Compound 1 is an unprecedented example in which four hemiacetals have been stabilized on a single molecule in the solid state retaining its stability in solution as revealed by its (1) H NMR spectrum in CD3 OD. The solution stability of 1 and 2 has further been confirmed by ESI-MS studies. To generalize the stabilization of multiple hemiacetals on a single double-four-ring platform, pyridine-2-carboxaldehyde (Py-2-CHO) was used as the auxiliary ligand in the reaction between zinc acetate and dippH2 , leading to isolation of [Zn(dipp)(Py-2-CH(OH)(OMe))]4 (3). Understandably, recrystallization of 3 from acetonitrile yields the parent aldehydic form, [Zn(dipp)(Py-2-CHO)]4 (4). Single-crystal X-ray diffraction studies reveal that supramolecular bonding, aided by hydrogen-bonding interactions involving the hemiacetal functionalities (C-OH, C-OMe, and C-H), are responsible for the observed stabilization. The hemiacetal/aldehyde groups in 1 and 2 readily react with p-toluidine, 2,6-dimethylaniline, and 4-bromoaniline to yield the corresponding tetra-Schiff base ligands, [Zn(dipp)(L)]4 (L=4-methyl-N-(pyridin-4-ylmethylidene)aniline (5), 2,6-dimethyl-N-(pyridin-4-ylmethylene)-aniline (6), and 4-bromo-N-(pyridin-4-ylmethylene)aniline (7)). Isolation of 5-7 opens up further possibilities of using 1 and 2 as new supramolecular synthons and ligands., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)