Sizes and fluorescence of cadmium sulfide quantum dots

Cadmium sulfide quantum dots have been synthesized by wet chemical deposition from an aqueous solution. The sizes of the quantum dots determined by dynamic light scattering directly in the colloidal solution and by intermittent-contact atomic force microscopy in the dry sediment agree with each other. It has been found that splitting of the fluorescence peaks of the quantum dots can be affected by the disorder of the atomic structure of cadmium sulfide quantum dots.     

Molecular and crystal structures of 4′-hydroxy derivative of (3<Emphasis Type="Italic">R</Emphasis>,6<Emphasis Type="Italic">R</Emphasis>)-3-methyl-6-isopropyl-2-(4-phenylbenzylidene)cyclohexanone

The molecular and crystal structures of the 4-hydroxy derivative of (3R,6R)-3-methyl-6-isopropyl-2-(4-phenylbenzylidene)cyclohexanone are determined by X-ray diffraction analysis. Single crystals are orthorhombic, a = 9.147(2) Å, b = 12.959(2) Å, c = 15.695(5) Å, V = 1860.4(7) ų, Z = 4, and space group P2₁2₁2₁. The cyclohexanone ring in the crystal structure has an asymmetric chair conformation. The puckering parameters are as follows: the puckering amplitude S is 0.91, and the puckering angles θ and ψ are equal to 20.2° and 10.4°, respectively. It is established that the enone fragment and the cyclohexanone ring in molecules are flattened considerably. In the crystal structure, the molecules are linked by the

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hydrogen bonds (bond length, 1.85 Å). The structural features and the strength of the hydrogen bonds for the compound under investigation and its analogue with one benzene ring are compared using the X-ray diffraction and IR spectroscopic data.

     

Synthesis and Structure of Different-Metal Different-Ligand Germanium(IV) and Cobalt(II) or Copper(II) Complexes with 1-Hydroxyethylidenediphosphonic Acid and 1,10-Phenanthroline

Different-metal different-ligand complexes [{Co(Phen)₃}₂{Co(Phen)(H₂O)₄}₂][{Ge(μ-OH)(μ- Hedp)}₆Cl₂] (I), [{Cu(Phen)₂(H₂O)}₂(HPhen)₂][Ge(μ-OH)(μ-Hedp)]₆ · 20H₂O (II) (H₄Hedp = 1-hydroxyethylidenediphosphonic acid, Phen = 1,10-phenanthroline) were synthesized and studied by X-ray diffraction. According to X-ray diffraction data (CIF files CCDC nos. 1573112 (I), 1573113 (II)), compounds I and II are cation–anion type complexes in which the anions are represented by {[Ge(μ-OH)(μ-Hedp)]⁶}^6– and, in the case of I, two additional Cl^– ions, while the cations are [Co(Phen)₃]²⁺, [Co(Phen)(H₂O)₄]²⁺ in I and [Cu(Phen)₂(H₂O)]²⁺, HPhen⁺ in II. In the crystals of compounds I and II, the cations, anions, and water molecules are combined by numerous intermolecular hydrogen bonds, giving rise to a 3D network.     

Stereoselective synthesis of 1,3-disubstituted phthalans by cyclization of (1<Emphasis Type="Italic">S</Emphasis>)-1-{2-[hydroxy(diaryl)methyl]phenyl}ethanols

Cyclization of pure enantiomers of 1-{2-[hydroxy(diaryl)methyl]phenyl}ethanol proceeds stereoselectively and affords 1,3-disubstituted 1,3-dihydroisobenzofurans (phthalans) in moderate-to-high enantiomeric (81.7% ee) or diastereomeric (72% de) purity.     

Two pseudo‐enantiomeric forms of N‐benzyl‐4‐hydroxy‐1‐methyl‐2,2‐dioxo‐1H‐2λ6,1‐benzothiazine‐3‐carboxamide and their analgesic properties

The fact that molecular crystals exist as different polymorphic modifications and the identification of as many polymorphs as possible are important considerations for the pharmaceutic industry. The molecule of N‐benzyl‐4‐hydroxy‐1‐methyl‐2,2‐dioxo‐1H‐2λ⁶,1‐benzothiazine‐3‐carboxamide, C₁₇H₁₆N₂O₄S, does not contain a stereogenic atom, but intramolecular hydrogen‐bonding interactions engender enantiomeric chiral conformations as a labile racemic mixture. The title compound crystallized in a solvent‐dependent single chiral conformation within one of two conformationally polymorphic P2₁2₁2₁ orthorhombic chiral crystals (denoted forms A and B). Each of these pseudo‐enantiomorphic crystals contains one of two pseudo‐enantiomeric diastereomers. Form A was obtained from methylene chloride and form B can be crystallized from N,N‐dimethylformamide, ethanol, ethyl acetate or xylene. Pharmacological studies with solid–particulate suspensions have shown that crystalline form A exhibits an almost fourfold higher antinociceptive activity compared to form B.     

Ultrasonic-promoted three-component synthesis of some biologically active 1,2,5,6-tetrahydropyrimidines

Multicomponent reactions and organic synthesis with ultrasonic activation have been used as key methods for the synthesis of tetrahydropyrimidine derivatives. The three-component condensation of 1,3-diarylprop-2-en-1-one with ammonia and aldehydes/acetone or N-substituted gamma-pyridones under ultrasonic irradiation was developed as a rapid and efficient solution-phase method for the high-yielding preparation of 2-aryl(hetaryl)-4,6-diaryl-1,2,5,6-tetrahydropyrimidines and 2,4-diaryl-1,5,9-triazaspiro[5.5]undec-1-enes. The described synthetic protocol provides rapid access to novel and diversely substituted tetrahydropyrimidines libraries. The simple, primary biological screening showed 98% of inhibitory activity against Mycobacterium tuberculosis for one of tetrahydropyrimidines synthesized.     

Novel heteroligand complexes of Co(II), Cu(II), Ni(II) and Mn(II) formed by 2,2′-dipyridyl or 1,10-phenanthroline and phosphortriamide ligands: Synthesis and structure

This paper presents examples of mixed-ligand Co(II), Cu(II), Ni(II) and Mn(II) complexes, with a distorted octahedral coordination geometry, with 2,2′-dipyridyl or 1,10-phenanthroline and phosphortriamide ligands. The complexes of the general type ML₂·Lig (where M = Co(II), Cu(II), Ni(II), Mn(II); L⁻ = {Cl₃C(O)NP(O)R₂}⁻ (R = NHBz, NHCH₂CHCH₂, NEt₂); Lig = 2,2′-dipyridyl or 1,10-phenanthroline) were synthesised and characterised by means of X-ray diffraction, IR and UV–Vis spectroscopy. The phosphortriamide ligands are coordinated via oxygen atoms of phosphoryl and carbonyl groups involved in six-membered metal cycles. The additional ligands 2,2′-dipyridyl or 1,10-phenanthroline are coordinated to the central atom, forming five-membered cycles.     

Proximal heteroalkylation of monoalkoxycalix[4]arenes in synthesis of inherently chiral molecules

Proximal heteroalkylation of monoalkyl ethers of calix[4]arenes or p-tert-butylcalix[4]arenes in NaH/CH₃CN or NaOH/DMSO, respectively, was applied for synthesis of inherently chiral calixarenes with ABHH substitution pattern. The introduction by the method of (R)- or (S)-N-(α-phenylethyl)acetamide chiral auxiliary group gives mixtures of diastereomeric derivatives of inherently chiral calixarenes, which were separated by column chromatography. The chiral calixarenes were thoroughly characterized by ¹H, ¹³C NMR, and X-ray diffraction methods.     

Reactions of 3-amino-1,2,4-triazoles with cinnamic aldehydes

The reaction of 3-amino- and 3-amino-5-methylthio-1,2,4-triazoles with cinnamaldehyde takes two directions to form mixtures of 5-[N-(3-phenylpropenylideneamino)]-1H-1,2,4-triazoles and 5-phenyl-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-7-ols.