Growth Behavior of Monohydrocalcite (CaCO₃·H₂O) in Silica-Rich Alkaline Solution

Monohydrocalcite (CaCO₃·H₂O) has been crystallized in silica-rich alkaline water solution. The crystallization proceeds by a counterdiffusion method without the presence of any other additive except dissolved silica. The crystallization has been followed in situ by optical microscopy and Raman microspectroscopy, while the time evolution of the pH and the concentration of calcium and silica species in solution have also been followed either by in situ (pH) or ex-situ (calcium and silica) time-lapse analysis. The growth of monohydrocalcite particles occurs by different mechanisms that are related to the pH and the rate of pH change with time. The initial peanut-like crystal converts into an onion-like multilayered texture, which is built up by the alternation of loose layers and compact layers as a result of different levels of silica incorporation. A final silica-rich skin covers the hemisphere inhibiting the further growth of monohydrocalcite. When the silica skin fails to cover the whole surface of the hemisphere, a bulge of monohydrocalcite grows from the uncovered area until a new silica skin inhibits its growth except from a small uncovered area from which a new bulge forms. The iteration of this mechanism creates particles with caterpillar-like morphology. Our results show that silica plays a key role in the morphogenesis and texture of monohydrocalcite crystallization due to the coupled interaction between the reverse solubility of silica and carbonate versus pH

<i>m</i>‑Carboranylphosphinate as Versatile Building Blocks To Design all Inorganic Coordination Polymers

The first examples of coordination polymers of manganese­(II) and a nickel­(II) complex with a purely inorganic carboranylphosphinate ligand are reported, together with its exhaustive characterization. X-ray analysis revealed 1D polymeric chains with carboranylphosphinate ligands bridging two manganese­(II) centers. The reactivity of polymer <b>1</b> with water and Lewis bases has also been studied

Highest Reported Denticity of a Synthetic Nucleoside in the Unprecedented Tetradentate Mode of Acyclovir

The unprecedented tetradentate, chelating, and μ₃-bridging mode of acyclovir (acv) drives to a 1D-polymeric ribbon in [{Cu₂(acv)­(μ₃-acv)­(SO₄)­(μ₂-SO₄)­(H₂O)₄}·H₂O·MeOH]_<i>n</i>, stabilized by μ₂-SO₄ ligands, interligand H-bonds, and anion/π-(SO₄/acv) interactions. Stacking π,π-(acv/μ₃-acv) interactions play a key role in the crystal packing

Chelating Ligand Conformation Driving the Hypoxanthine Metal Binding Patterns

The X-ray diffraction structural results of 23 ternary compounds, type M^II(iminodiacetate-like)(hypoxanthine) [M = Co, Ni, Cu, or Zn], show that the iminodiacetate moiety conformation (<i>mer</i>-NO₂ or <i>fac</i>-NO₂) is able to drive the M-hypoxanthine binding patterns displaying the M–N9 or M–N3 bond, cooperating with a N9–H···O intramolecular interaction, respectively

Metal complexes with N-(trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands). Part I. Copper(II) chelates of p-3F, m-3F, and o-3F with or without imidazole-like ligands

<div><p>Eight Cu(II) complexes with N-(p-, m- or o-trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands) have been synthesized to promote C–F/H interligand interactions involving the F₃C-group: {[Cu(μ₂-p-3F)(H₂O)]·3H₂O]}_n (<b>1</b>), [Cu(m-3F)(H₂O)₂] (<b>2</b>), [Cu(p-3F)(Him)(H₂O)] (<b>3</b>), [Cu(m-3F)(Him)(H₂O)] (<b>4</b>), [Cu(o-3F)(Him)(H₂O)] (<b>5</b>), [Cu₂(p-3F)₂(H5Meim)₂(H₂O)₂] (<b>6</b>), [Cu(m-3F)(H5Meim)(H₂O)] (<b>7</b>), and [Cu(o-3F)(H5Meim)(H₂O)] (<b>8</b>) [Him and H5Meim = imidazole and the “remote” tautomer 5-methylimidazole, respectively]. The compounds were studied by single-crystal X-ray diffraction, FT-IR, electronic spectra and coupled thermogravimetric + FT-IR methods. The conformation of the iminodiacetate chelating moiety (IDA group) is <i>fac</i>-NO + O(apical) in <b>1</b> and <i>mer</i>-NO₂ in <b>2–8</b>. The <i>fac</i>-IDA conformation observed in <b>1</b> is related to its polymeric structure and the coordination of a O’-carboxylate donor, from an adjacent complex unit, <i>trans</i> to the Cu–N(IDA) bond. The <i>mer</i>-IDA conformation in <b>2</b> is in agreement with similar compounds with an aqua ligand <i>trans</i> to the corresponding Cu–N(IDA) bond. As expected, the ternary complexes <b>3–8</b> feature a <i>mer</i>-IDA conformation. Some of the studied complexes exhibit disorder in the –CF₃ group and C–H⋯F interligand interactions along with conventional N–H⋯O and O–H⋯O interactions. The thermal decomposition of all studied compounds under air flow produces variable amounts of trifluorotoluene.</p></div

Cocrystallization of Mononuclear and Trinuclear Metallacycle Molecules from an Aqueous Mixed-Ligand Copper(II) Solution

The compound [Cu­(μ₂-NamIDA)­(2,4-dapyd)]₃·3­[Cu­(NamIDA)­(2,4-dapyd)­(H₂O)]·21H₂O (NamIDA = <i>N</i>-(1-naphtylmethyl)­iminodiacetate­(2-) and 2,4-dapyd = 2,4-diaminopyrimidine) is a spontaneous cocrystal with mononuclear and trinuclear metallacycle complex molecules, where extensive intermolecular H bonds play a key role

Cocrystallization of Mononuclear and Trinuclear Metallacycle Molecules from an Aqueous Mixed-Ligand Copper(II) Solution

The compound [Cu­(μ₂-NamIDA)­(2,4-dapyd)]₃·3­[Cu­(NamIDA)­(2,4-dapyd)­(H₂O)]·21H₂O (NamIDA = <i>N</i>-(1-naphtylmethyl)­iminodiacetate­(2-) and 2,4-dapyd = 2,4-diaminopyrimidine) is a spontaneous cocrystal with mononuclear and trinuclear metallacycle complex molecules, where extensive intermolecular H bonds play a key role

Ti(III)-Catalyzed Cyclizations of Ketoepoxypolyprenes: Control over the Number of Rings and Unexpected Stereoselectivities

We describe a new strategy to control the number of cyclization steps in bioinspired radical (poly)­cyclizations involving epoxypolyenes containing keto units positioned along the polyene chain. This approach provides an unprecedentedly straightforward access to natural terpenoids with pendant unsaturated side chains. Additionally, in the case of bi- and tricyclizations, decalins with <i>cis</i> stereochemistry have been obtained as a consequence of the presence of the ketone. The preferential formation of <i>cis</i>-fused adducts was rationalized using DFT calculations. This result is completely unprecedented in biomimetic cyclizations and permits the access to natural terpenoids with this stereochemistry, as well as to non-natural analogues

Synthesis and Crystallographic Studies of Disubstituted Carboranyl Alcohol Derivatives: Prevailing Chiral Recognition?

The syntheses of new <i>o</i>-carboranyldiols bearing aromatic rings bis-[R­(hydroxy)­methyl]-1,2-dicarba-<i>closo</i>-dodecaborane (R = 2-pyridyl <b>1a</b>, 3-pyridyl <b>1b</b>, 4-pyridyl <b>1c</b>, 2-quinolyl <b>1d</b>, 4-quinolyl <b>1e</b>, phenyl <b>1f</b>) are reported. The compounds are obtained as mixtures of meso (<i>syn</i>) and racemic (<i>anti</i>) stereoisomers with a slight diastereomeric excess (<i>syn</i>:<i>anti</i> ratio of 0.7:1) in all cases but in <b>1b</b>. The crystal structures of the meso compounds <i>syn</i><b>-1a</b>·2MeOH, <i>syn</i><b>-1b</b>, <i>syn</i><b>-1f</b>·0.25H₂O and racemic <i>anti</i><b>-1a</b>·MeOH, <i>anti</i><b>-1a</b>·EtOH, and <i>anti</i><b>-1d</b>·2H₂O are reported. We provide an analysis of these compounds by means of NMR and X-ray crystallography, in the context of crystal engineering and chiral recognition. The results show that the crystal packings for these alcohols are dominated by the supramolecular O–H···N and/or O–H···O hydrogen bonds. Supramolecular analysis of all compounds in this work reveals that homochiral self-assembly, that is, formation of homochiral hydrogen bonded complexes, prevails over heterochiral self-assembly (formation of heterochiral hydrogen bonded complexes)

Synthesis and Crystallographic Studies of Disubstituted Carboranyl Alcohol Derivatives: Prevailing Chiral Recognition?

The syntheses of new <i>o</i>-carboranyldiols bearing aromatic rings bis-[R­(hydroxy)­methyl]-1,2-dicarba-<i>closo</i>-dodecaborane (R = 2-pyridyl <b>1a</b>, 3-pyridyl <b>1b</b>, 4-pyridyl <b>1c</b>, 2-quinolyl <b>1d</b>, 4-quinolyl <b>1e</b>, phenyl <b>1f</b>) are reported. The compounds are obtained as mixtures of meso (<i>syn</i>) and racemic (<i>anti</i>) stereoisomers with a slight diastereomeric excess (<i>syn</i>:<i>anti</i> ratio of 0.7:1) in all cases but in <b>1b</b>. The crystal structures of the meso compounds <i>syn</i><b>-1a</b>·2MeOH, <i>syn</i><b>-1b</b>, <i>syn</i><b>-1f</b>·0.25H₂O and racemic <i>anti</i><b>-1a</b>·MeOH, <i>anti</i><b>-1a</b>·EtOH, and <i>anti</i><b>-1d</b>·2H₂O are reported. We provide an analysis of these compounds by means of NMR and X-ray crystallography, in the context of crystal engineering and chiral recognition. The results show that the crystal packings for these alcohols are dominated by the supramolecular O–H···N and/or O–H···O hydrogen bonds. Supramolecular analysis of all compounds in this work reveals that homochiral self-assembly, that is, formation of homochiral hydrogen bonded complexes, prevails over heterochiral self-assembly (formation of heterochiral hydrogen bonded complexes)