Extended metal-organic solids based on benzenepolycarboxylic and aminobenzoic acids

This article describes the recent results obtained in our laboratory on the interaction of polyfunctional ligands with divalent alkaline earth metal ions and a few divalent transition metal ions. Treatment of MC12·nH2O (M = Mg, Ca, Sr or Ba) with 2-amino benzoic acid leads to the formation of complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]∞ (2), [{Sr(2-aba)2(OH2)2}2·H2O)]∞ (3), [Ba(2-aba)2(OH2)]∞ (4), respectively. While the calcium ions in 2 are hepta-coordinated, the strontium and barium ions in 3 and 4 reveal a coordination number of nine apart from additional metal-metal interactions. Apart from the carboxylate functionality, the amino group also binds to the metal centres in the case of strontium and barium complexes 3 and 4. Complexes [{Mg(H2O)6}(4-aba)2·2H2O] (5), [Ca(4-aba)2(H2O)2] (6) prepared from 4-aminobenzoic acid reveal more open or layered structures. Interaction of 2-mercaptobenzoic acid with MCl2·6H2O (M = Mg, Ca), however, leads to the oxidation of the thiol group resulting in the disulphide 2,2' -dithiobis(benzoic acid). New metal-organic framework based hydrogen-bonded porous solids [{M(btec) (OH2)4}n·n(C4H12N2)·4nH2O] (btec = 1,2,4,5-benzene tetracarboxylate) (M = Co9; Ni10; Zn11) have been synthesized from 1,2,4,5-benzene tetracarboxylic acid in the presence of piperazine. These compounds are made up of extensively hydrogen-bonded alternating layers of anionic M-btec co-ordination polymer and piperazinium cations. Compounds 2- 11 described herein form polymeric networks in the solid-state with the aid of different coordinating capabilities of the carboxylate anions hydrogen bonding interactions

Transposable element-mediated rearrangements are prevalent in human genomes.

Transposable elements constitute about half of human genomes, and their role in generating human variation through retrotransposition is broadly studied and appreciated. Structural variants mediated by transposons, which we call transposable element-mediated rearrangements (TEMRs), are less well studied, and the mechanisms leading to their formation as well as their broader impact on human diversity are poorly understood. Here, we identify 493 unique TEMRs across the genomes of three individuals. While homology directed repair is the dominant driver of TEMRs, our sequence-resolved TEMR resource allows us to identify complex inversion breakpoints, triplications or other high copy number polymorphisms, and additional complexities. TEMRs are enriched in genic loci and can create potentially important risk alleles such as a deletion in TRIM65, a known cancer biomarker and therapeutic target. These findings expand our understanding of this important class of structural variation, the mechanisms responsible for their formation, and establish them as an important driver of human diversity

Resolution of structural variation in diverse mouse genomes reveals chromatin remodeling due to transposable elements.

Diverse inbred mouse strains are important biomedical research models, yet genome characterization of many strains is fundamentally lacking in comparison with humans. In particular, catalogs of structural vari- ants (SVs) (variants R 50 bp) are incomplete, limiting the discovery of causative alleles for phenotypic vari- ation. Here, we resolve genome-wide SVs in 20 genetically distinct inbred mice with long-read sequencing. We report 413,758 site-specific SVs affecting 13% (356 Mbp) of the mouse reference assembly, including 510 previously unannotated coding variants. We substantially improve the Mus musculus transposable element (TE) callset, and we find that TEs comprise 39% of SVs and account for 75% of altered bases. We further utilize this callset to investigate how TE heterogeneity affects mouse embryonic stem cells and find multiple TE classes that influence chromatin accessibility. Our work provides a comprehensive analysis of SVs found in diverse mouse genomes and illustrates the role of TEs in epigenetic differences

Synthesis and characterization of new (chloro)aminosilanes: X-ray crystal structure of [(2,6-Me2C6H3NH)(2)SiCl2]

Starting from racemic alpha -methylbenzyl amine or alpha -methylbenzyl bromide, new (amino)trichlorosilanes (MePhC(H))(SiMe3)NSiCl3(1) and (MePhC(H))(2,6-Me2C6H3) NSiCl3 (2) have been synthesized in good yields. The products have been characterized by analytical and IR, mass, and NMR (H-1 and Si-29) spectroscopic techniques. The diamino-dichlorosilane (2,6-Me2C6H3NH)(2)SiCl2 (3) obtained as the side product during the synthesis of 2 has been characterized by a single crystal X-ray diffraction study

Stabilization of p-block organoelement terminal hydroxides, thiols, and selenols requires newer synthetic strategies

Metal hydroxides represent a very interesting and highly useful class of compounds that have been known to chemists for a very long time. While alkali and alkaline earth metal hydroxides (s-block) are commonplace chemicals in terms of their abundance and their use in a chemical laboratory as bases, the interest in Bronsted acidic molecular terminal hydroxides of p-block elements, such as aluminum and silicon, has been of recent origin, with respect to the variety of applications these compounds can offer both in materials science and catalysis. Moreover, these systems are environmentally friendly, relative to the metal halides, owing to their -OH functionality (resembling that of water). Design and conceptualization of the corresponding terminal thiols, selenols, and tellurols (M-SH, M-SeH, and M-TeH) offer even more challenging problems to synthetic inorganic chemists. This concept summarizes some of the recent strategies developed to stabilize these otherwise very unstable species. The successful preparation of a number of silicon trihydroxides a few years back resulted in the generation of several model compounds for meta I-silicates. The recent synthesis of unusual aluminum compounds such as RAl(OH)(2), RAl(SH)(2), and RAl(SeH)(2) with terminal EH (E=O, Se, or Se) groups is likely to change the ways in which some of the well-known catalytic conversions are being carried out. The need for very flexible and innovative synthetic strategies to achieve these unusual compounds is emphasized in this concept

Containment of Polynitroaromatic Compounds in a Hydrogen Bonded Triarylbenzene Host

Co-crystallization of energetic materials has emerged as an important technique to modify their critical properties such as stability, sensitivity, etc. Using 1,3,5-tris(4'-aminophenyl)benzene (TAPB) as a novel co-crystal former, we have prepared co-crystals of 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol (TNP), and m-dinitrobenzene (mDNB). Molecular structures of the co-crystals have been determined from single crystal X-ray diffraction data. The diffraction data analysis reveals that strong intermolecular pi-pi interaction directs the intercalation of polynitroaromatic explosives (PNACs) between the layers of TAPB molecules, which leads to the formation of vertically overlapped -A-B-A-B- types of p-stacks. Both TNT and TNP form p-interactions with the center of TAPB with 1:1 molar ratios, while mDNB forms a complex in a 1:3 stoichiometry through stacking between peripheral rings. The crystal lattices are further stabilized through interstack hydrogen bonds (NH...N and NH...O) between amino groups of TAPB and nitro groups of PNACs. NMR and Fourier transform infrared spectra further provide the information about the presence of various interactions in the crystal systems. Owing to the p electron-rich nature and ease of synthesis, triphenylbenzene systems are promising host candidates for co-crystallization of PNAC analytes

Di-tert-butyl phosphate complexes of cobalt(II) and zinc(II) as precursors for ceramic M(PO(3))(2) and M(2)P(2)O(7) materials: Synthesis, spectral characterization, structural studies, and role of auxiliary ligands

Reaction of the metal acetates M(OAc)(2). xH(2)O with di-tert-butyl phosphate (dtbp-H) (3) in a 4:6 molar ratio in methanol or tetrahydrofuran followed by slow evaporation of the solvent results in the formation of metal phosphate clusters [M(4)(mu (4)-O)(dtbp)(6)] (M = Co (4, blue); Zn (5, colorless)) in nearly quantitative yields. The same reaction, when carried out in the presence of a donor auxiliary ligand such as imidazole (imz) and ethylenediamine (en), results in the formation of octahedral complexes [M(dtbp)(2)(imz)(4)] (M = Co (6); Ni (7); Zn (8)) and [Co(dtbp)(2)-(en)(2)] (9). The tetrameric clusters 4 and 5 could also be converted into mononuclear 6 and 8, respectively, by treating them with a large excess of imidazole. The use of slightly bulkier auxiliary ligand 3,5-dimethylpyrazole (3,5-dmp) in the reaction between cobalt acetate and 3 results in the isolation of mononuclear tetrahedral complex [Co(dtbp)(2)(3,5-dmp)(2)] (10) in nearly quantitative yields. Perfectly air- and moisture-stable samples of 4-10 were characterized with the aid of analytical, thermoanalytical, and spectroscopic techniques. The molecular structures of the monomeric pale-pink compound 6, colorless 8, and deep-blue 10 were further established by single-crystal X-ray diffraction studies. Crystal data for 6: C(28)H(52)CoN(8)O(8)P(2), a = 8.525(1) Angstrom, b = 9.331(3) Angstrom, c = 12.697(2) Angstrom, alpha = 86.40(2)degrees, beta = 88.12(3)degrees, gamma = 67.12(2)degrees, triclinic, P (1) over bar, Z = 1. Crystal data for 8: C(28)H(52)N(8)O(8)P(2)Zn, a = 8.488(1) Angstrom, b = 9.333(1) Angstrom, c = 12.723(2) Angstrom, alpha = 86.55(1)degrees, beta = 88.04(1)degrees, gamma = 67.42(1)degrees, triclinic, P (1) over bar, Z = 1. Crystal data for 10: C(26)H(52)CON(4)O(8)P(2), a = b = 18.114(1) Angstrom, c = 10.862(1) Angstrom, tetragonal, P4(1), Z = 4. The Co(2+) ion in 6 is octahedrally coordinated by four imidazole nitrogens which occupy the equatorial positions and oxygens of two phosphate anions on the axial coordination sites. The zinc derivative 8 is isostructural to the cobalt derivative 6. The crystal structure of 10 reveals that the central cobalt atom is tetrahedrally coordinated by two phosphate and two 3,5-dmp ligands. In all structurally characterized monomeric compounds (6, 8, and 10), the dtbp ligand acts as a monodentate, terminal ligand with free P=O phosphoryl groups. Thermal studies indicate that heating the samples at 171 (for 4) or 93 degreesC (for 5) leads to the loss of twelve equivalents of isobutene gas yielding carbon-free [M(4)(mu (4)-O)(O(2)P(OH)(2))(6)], which undergoes further condensation by water elimination to yield a material of the composition Co(4)O(19)P(6) This sample of 4 when heated above 500 degreesC contains the crystalline metaphosphate Co(PO(3))(2) along with amorphous pyrophosphate M(2)P(2)O(7) in a 2:1 ratio. Similar heat treatment on samples 6-8 results in the exclusive formation of the respective metaphosphates Co(PO(3))(2), Ni(PO(3))(2), and Zn(PO(3))(2); the tetrahedral derivative 10 also cleanly converts into Co(PO(3))(2) On heating above 600 degreesC