6,6′-Diamino-1,1′,3,3′-tetra­methyl-5,5′-(4-chloro­benzyl­idene)bis­[pyrimidine-2,4(1H,3H)-dione]

The title compound, C19H21ClN6O4, is a 1:2 adduct of p-chloro­benzaldehyde and uracil. It crystallizes with two mol­ecules in the asymmetric unit. The two uracil units in the same mol­ecule are connected by a pair of strong N—H⋯O hydrogen bonds. The packing is stabilized by N—H⋯O, C—H⋯O and C—H⋯N inter­actions

{4-[(3-Formyl-4-hy­droxy­phen­yl)diazen­yl]benzoato}triphenyl­tin

In the title compound, [Sn(C6H5)3(C14H9N2O4)], the Sn atom has a distorted tetra­hedral geometry with one of the carboxyl­ate O atoms and the C atoms from three phenyl groups. The other carboxyl­ate O atom of the benzoate ligand inter­acts weakly with the Sn atom, with an Sn⋯O distance of 2.790 (2) Å, which causes a distortion of the tetra­hedral coordination geometry

Dicarbonylruthenium(II) complexes of diphosphine ligands and their catalytic activity

The hexa-coordinated chelate complexes of the type [Ru(CO)2Cl2(P-P)](1a,b) [where P-P = 9,9-dimethyl- 4,5-bis(diphenylphosphino)xanthene(a) and [bis(2-diphenylphosphinophenyl)ether(b)] have been synthesized by reacting the polymeric precursor [Ru(CO)2Cl2]n with the ligands in 1:1 molar ratio. The complexes 1a,b are characterized by elemental analyses, Mass, IR and NMR spectroscopy together with the single crystal X-ray structure determination of 1a. The compound 1a crystallizes in a monoclinic system with space group C2/c showing a slightly distorted octahedral geometry around the Ru centre. The complexes 1a and 1b are thermally stable up to 300 �C and exhibit high catalytic activity in transfer hydrogenation of aldehyde and ketones to corresponding alcohols. The complexes 1a and 1b show much higher catalytic activity for the hydrogenation of aldehyde than ketones. In general, the catalytic efficiency of 1b is higher compared with 1a

Supramolecular Synthons and Hydrates in Stabilization of Multicomponent Crystals of Nicotinamide and Isonicotinamide with N-Containing Aromatic Dicarboxylic Acids

Multicomponent crystals (either cocrystal or salt) of nicotinamide (nicotinic acid amide) and isonicotinamide with various nitrogen heterocycle-containing aromatic dicarboxylic acids, namely, 3,5-pyrazole dicarboxylic acid (pzdca), dipicolinic acid (dpa), and quinolinic acid (qna), have been synthesized and characterized by single-crystal diffraction and thermal studies. The nicotinamide (nic) and isonicotinamide (isonic) cocrystals with 3,5-pyrazole dicarboxylic acid (<b>1</b> and <b>2</b>, respectively) possess four different heteromeric supramolecular synthons in each cocrystal, which is rare. The nicotinamide dipicolinic acid cocrystal, <b>3</b>, showed formation of water-bridged assembly, whereas isonicotinamide-dipicolinic acid cocrystal, <b>4</b>, led to a six-component assembly through the isolated solvent water molecules occupying the interstitial positions. The salt formed from quinolinic acid with nicotinamide <b>5</b> has a hydrogen-bonded 1D water chain in its crystal lattice, whereas quinolinic acid with isonicotinamide resulted in formation of <b>6</b> with 2D sheets of multiple heterosynthons. Thermal studies show evaporation of various water molecules with a trend that has relevance to their hydrogen-bonding environment in the multicomponent crystal

Influence of the Local Chemical Environment in the Formation of Multicomponent Crystals of L‑Tryptophan with N‑Heterocyclic Carboxylic Acids: Unusual Formation of Double Zwitterions

Formation of multicomponent crystals (MCCs) of L-tryptophan (TRP) with <i>N</i>-heterocyclic carboxylic acids such as 2-picolinic acid (PA) and its 3- or 4-substituent isomers (nicotinic acid or isonicotinic acid), pyrazinecarboxylic acid (PZCA), 2,3-pyrazinedicarboxylic acid (2,3-PZDCA), 2-quinaldic acid (QA), and its 3-subsituent isomer (3-QA) is investigated in this manuscript. The investigation results in four multicomponent solid forms of the amino acid with coformers where the electron withdrawing functional group (−COOH) is present in the <i>ortho-</i>substituent to N-heterocyclic rings. The isomers of PA or QA having −COOH at the <i>meta-</i> or <i>para-</i> position failed to produce new phases. These solid phases were identified by powder X-ray diffraction results, and the MCCs derived from 2-picolinic acid (<b>1</b>) and 2,3-pyrazinedicarboxylic acids (<b>3</b>) were further characterized with single crystal X-ray diffraction. The crystal structure of TRP-PA (<b>1</b>) reveal a rare form of cocrystal where both the amino acid and the picolinic acid are in zwitterionic form. Further, in our surprise, the amino acid appears to undergo change in absolute configuration during cocrystallization. Crystal TRP-2,3-PZDCA (<b>3</b>) is observed as a salt where the amino acid exists in cationic form, and the carboxylic acid exists in anionic form. It is observed that the complementary H-bonding between the py-N/<i>ortho</i>- −COOH of the coformers with the α-NH₃⁺/α-COO^– group of L-tryptophan primarily drives the cocrystallization process. Density functional theory calculations support the experimental observations as lower total energy and higher interaction energy values are obtained for the successfully synthesized MCCs. The solid state fluorescence of TRP (known as intrinsic fluorescence probe) shows that 2,3-PZDCA is an effective quencher

Molecular and crystal structure of 6⍺-acetoxy azadirone

1879-1882The crystal structure of the title compound, 1 has been determined by X-ray crystallographic techniques. The compound crystallizes in orthorhombic space group P2₁2₁2₁ with unit cell parameters: a=10.699(3) Å, b=15.510(4) Å, c=16.626(4) Å, Z=4. The structure has been solved by direct methods and refined to R = 0.0585 for 6681 independent reflections