The components of the blood stain, eosin and methylene blue, were introduced by Baeyer and Caro, respectively. Methylene blue was used primarily for detecting Mycobacterium tuberculosis until Ehrlich in 1880 mixed methylene blue with acid fuchsin to produce what he termed a "neutral stain," which allowed differentiation of blood cells. Eight years later, Chęciń ski changed the acidic component of the dye to eosin. Plehn subsequently altered the proportions of eosin and methylene blue to produce a greater range of red and blue hues. In 1891, Malachowski and Romanowsky independently developed stains composed of eosin and "ripened" methylene blue that not only differentiated blood cells, but also demonstrated the nuclei of malarial parasites. A number of "ripening" or "polychroming" techniques were investigated by different groups, but the aqueous dye solutions produced were unstable and precipitated rapidly. Subsequently, methanol was introduced as a solvent for the dye precipitate and techniques were developed that utilized the fixative properties of the methanolic solution prior to aqueous dilution for staining. This avoided the troublesome process of heat fixation of blood films. Giemsa further improved these techniques by using more controlled methods of methylene blue demethylation. In addition, he used measured amounts of known dyes and increased dye stability by adding glycerol to the methanol solvent. With the outbreak of World War I, it became difficult to obtain German dyes outside of Germany; during the World War II, it became impossible. In their effort to improve the inferior American versions of Giemsa's stain, Lillie, Roe, and Wilcox discovered that the best staining results were obtained using pure methylene blue, one of its breakdown products (azure B) and eosin. These three substituents remain the major components of the stain to this day.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Three new acid salts of two monocarboxylic acids were obtained and their crystal structure analysis performed using experimental data collected with KM-4 diffractometer. The crystal structures of hydrogen bis(sulfosalicylates) of sodium and potassium contain hydrogen-bonded acid-anion dimers of very similar geometry and are classified to type A and pseudo A of hydrogen bis(monocarboxylates). Crystalline sodium hydrogen bis(3,5-dinitrobenzoate) contains a trimer acid-anion-acid. Its structure, which differs from that of potassium salt determined earlier, is classified as type B. The role of cations and anions in the investigated structures is discussed.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

2-[(2,5-dichloro-4-nitro-phenylamino)-methoxy-methyl]-8-hydroxy-quinoline 1 and 2-methyl-quinoline-5,8-dione-5-oxime 2 were obtained as potential HIV-1 integrase inhibitors and analyzed by X-ray crystallography. Semiempirical theoretical calculations of energy preferred conformations were also carried out. The crystal structures of both compounds are stabilized via hydrogen bonds and pi-pi stacking interactions. The planarity of compound 1 is caused by intramolecular hydrogen bonds.

The crystal structures of mefloquine base, [C17H16F6N2O], and two salts of mefloquine: hydrochloride [(C17H17F6N2O)+]3[Cl-]3.3H2O and hydrochloride tetrachlorocobaltate [(C17H17F6N2O)+]3Cl-[CoCl4]2-.C2H6O.H2O, were determined by X-ray diffraction measurements. A comparison of the crystal structures of mefloquine in three different crystalline environments shows that their conformations are stable regardless of mefloquine being a base or a salt. In addition, the conformation of mefloquine is similar to those of crystalline Cinchona alkaloids. The CF3 substituents in the quinoline moiety affect the packing of molecules.

The crystal structure of (C19H24N2O2+)2(CdCl4)2−(Cd0.5Cu0.5Cl4)2− has been determined by X-ray diffraction at 295K. The compound crystallises in orthorhombic P212121 space group with unit cell parameters: a=12.7381(10), b=13.5394(10), c=25.6520(10)Å, and Z=4. Packing of molecules in the unit cell is determined by single and bifurcated hydrogen bonds between cinchoninium cation, (cinchonineH2)2+, CuCl42− and CdCl42− tetrahedral anions. Specific feature of the packing is a partial stacking of the quinoline rings of adjacent cinchoninium cations. There are eight sites for M=Cd or Cu in the crystal unit cell. In the four of them the CdCl4 tetrahedra are located. In the others Cd or Cu can be located and an average geometry (Cd/CuCl4) is described by the X-ray diffraction data. EPR allows to observe only the CuCl4 complexes and we have proved that there is not a random distribution of individual Cd and Cu among the (Cd/CuCl4) sites but they are coupled in dimers, so that asymmetric unit can be identified as (cinchonineH2·MeCl4)2 moiety. Specific feature of the structure is that CuCl4 tetrahedra are relatively weakly deformed from ideal tetrahedral geometry Td towards the D2d symmetry (flattening angle 123.3°) and have relatively long Cu–Cl bonds (2.338Å) at 295K. Reflectance optical absorption band at 8700cm−1 with a shoulder at 6200cm−1 are assigned to (x2−y2)→(z2) and (x2−y2)→(xy) transitions, and they follow the well-known relationship between band positions and geometry of tetrachlorocuprates. EPR shows that the exchange coupling between Cu2+ ions is very weak and an individual CuCl4 gives separate lines in EPR spectrum. The spectrum below 200K is characterised with parameters gx=2.047, gy=2.127, and gz=2.404 and above this temperature becomes dynamically averaged to g∥=2.299 and g⊥=2.065. This continuous type transition to the dynamic phase, without a thermal effect, is accompanied by the change in the crystal colour from green to yellow which is characteristic for thermochromic transitions observed in tetrachlorocuprates. The dynamics is related to the Jahn–Teller effect operating in the triplet ground state T2 of Cu2+in weakly deformed tetrahedra. It is described as reorientations of the CuCl4 between two Jahn–Teller distorted configurations, across the energy barrier of about 80cm−1, resulting in dynamically averaged geometry of the CuCl4-tetrahedra observed at room temperature.

The crystal structure of 2-[(N,N-dimethylamino)methyl]benzenetellurenyl chloride (2), a compound previously formulated as bis[[2-(N,Ndimethylamino)methyl]phenyl] ditelluride bis hydrochloride (1a), was determined. In the molecule 2, tellurium is bonded to the carbon of the phenyl group [2.120(3) Angstrom], the nitrogen of the ortho dimethylamino substituent [2.362(3) Angstrom], and the chlorine atom [2.536(1) Angstrom]. There also is an intermolecular interaction of the tellurium atom with the phenyl ring of a neighbouring molecule [3.655(1) Angstrom], resulting in the formation of zigzag chains along the b axis. The noncentrosymmetric space group of the crystal can be explained by the chiral surrounding of tellurium.

X-ray crystal structure analysis was performed on single crystals of two diastereomeric enantiopure quinuclidines, (3R,8R)-3-vinyl-8-hydroxymethyl-quinuclidine (quincoridine, QCD) and (3R,8S)-3-vinyl-8-hydroxymethyl-quinuclidine (quincorine, QCI) as their salts with tartaric and p-toluenesulphonate anions, respectively. The molecules of these quinuclidine derivatives are considered here as fragments of the Cinchona alkaloids, quinidine and quinine. A comparison of the conformational features of QCD, QCI, and Cinchona alkaloids in the crystalline state shows that the molecular geometry of the title compounds is similar to that of threo-alkaloids (e.g., R,R isomer of epicinchonine) rather than to quinidine and quinine. The packing of the molecules in both structures is dominated by intermolecular hydrogen bonds.

The structures of two single crystal modifications, orange and yellow, of 7,16-dibenzoyl-6,8,15,17-tetramethyl-5,14-dihydrodibenzo [b,i][1,4,8,11]tetraazacyclotetradecine were determined in room and low temperatures. The aromaticity of the 14-membered macrocyclic ring system was studied with the use of HOMA index and compared to the values calculated for the structures found in the Cambridge Structural Database System. The nature of the polymorphism of the investigated molecules was elucidated. The molecules of the orange and yellow modifications differ in the mutual orientation of the benzoyl groups. The molecular conformation in the yellow crystals is stabilized by two intramolecular hydrogen bonds, C–H⋯OC, which do not occur in the orange modification. Weak, but numerous, intermolecular bonds of this type occur in both modifications, but in the orange polymorph a π–π interaction is also observed, while in the yellow modification a C–H⋯N intermolecular bond is formed.

The X-ray structure analysis of a single crystal of 3-methyl-5-p-methylbenzylidene-2-selenohydantoin was carried out. The crystals are monoclinic, space group P2 1 /c, with a = 5.244(1) Å, b = 19.402(2) Å, c = 11.606(1) Å, g = 94.64(1)°;, Z = 4. The molecule is a Z-isomer. The overall conformation is not exactly planar, the angle between the hydantoin and p-methylphenyl planes is 11.8(1)°;. The packing of the molecules in the unit cell can be described as an arrangement of molecular chains which interact with each other via weak-hydrogen bonds, C--H·;·;·;O. The chains consist of dimers in which molecules are linked together by two symmetry-equivalent hydrogen bonds, N--H·;·;·;Se, that form accros inversion centres. The dimers interact also via weak hydrogen bonds, C--H·;·;·;O, between methyl groups and carbonyls of molecules related by another inversion centres.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The X-ray crystal structure analysis was performed for single crystals of bis (4-aminophenyl) telluride (1), bis [4-(N,N-dimethylamino)phenyl] telluride (2) and his 4-hydroxyphenyl telluride hemihydrate (3). The molecules of the diaryl tellurides 1-3 display two types of non-planar conformations: 'butterfly' and 'T-shaped'. They differ in the torsion angles around Te-C bonds. Intermolecular hydrogen bonds occur between water molecules and hydroxyl groups in compound 3 and also between phenyl rings and proton donors in compounds 2 and 3 with -H(...)pi distances 2.56(8)-2.95(6) A. Also, in compounds 1 and 2 short -H(...)pi contacts (3.02(4)-3.29(5) Angstrom) were observed. (C) 2002 Elsevier Science B.V. All rights reserved.

Two crystalline modifications of cinchonine cobalt complex, C19H23Cl3CoN2O, were obtained from mixture of saturated alcohol solutions of CoCl3 x 6H2O and cinchonine. The X-ray structure analysis revealed that the asymmetric unit of one modification, CoCn1, contains only zwitterionic molecules of the complex. In the asymmetric unit of the other, CoCn2, there are two molecules of the title compound and two molecules of ethanol. The influence of the absolute configuration, the CoCl3 coordination with quinoline, and the presence of alcohol molecules on the studied structures was established by comparison of the crystal and molecular structures of both cobalt complexes with the analogous quinine complex and zinc complex of cinchonine. The interactions that dominate in the packing of the molecules in both structures are intermolecular hydrogen bonds. They form characteristic ring systems, depending on the presence of the alcohol molecules. The ring features are also related to the absolute configuration of the alkaloid.

A new complex of diastereoisomeric pair, quinine and quinidine (QQd), was obtained from a mixture of saturated ethanol solutions of quinine and quinidine (0.5:1). The complex crystallises in the triclinic system, space group P1, and contains two molecules of quinine, two molecules of quinidine and four water molecules in the asymmetric unit. The X-ray structure analysis of a single crystal revealed that quinine and quinidine molecules occur in the so-called open conformation, characteristic for Cinchona alkaloids, whenever they are engaged in intermolecular hydrogen bonds. Quinine and quinidine molecules are organized in two very similar kinds of chains. In each chain the links that contain 14-membered rings can be distinguished. Within these rings quinine and quinidine molecules interact via intermolecular hydrogen bonds between the quinuclidine nitrogens and hydroxyl groups, mediated by water molecules. The links are connected with each other by hydrogen bonds between water molecules and nitrogens of the quinoline moieties, which interact via pi-pi stacking. The architecture of the hydrogen bond system in QQd, compared to those observed in the crystal structures of nonhydrated quinidine, cinchonine and cinchonidine, reveals the effect of the co-crystallizing water on the molecular packing. In nonhydrated alkaloid structures the hydrogen-bonded molecules form helical chains, different from those observed in the hydrated QQd complex and hydrated quinine toluene solvate (QTol). Comparison of QQd structure with that of QTol suggests that while the intermolecular hydrogen bonds in the system quinine-water-quinidine-water are very similar to those in quinine-water-quinine-water system, the mode of pi-pi interaction between their quinoline moieties depends on the absolute configuration of the interacting alkaloid molecules.

Marmesinine -C20H24O9, coumarin β-D-glucoside derivative -appears in several plants -e.g.Ruta graveolens, playing role of biocontrolling, antipathogenic compound.Marmesinine was first isolated by Reisch in 1970.Its molecular structure was assigned using NMR spectroscopy by Duddeck and coworkers (1993).In spite of development in separation techniquesmarmesinine is difficult to crystallize, appearing as 'amorphous powder' (Kitayama, 2001).The crystal structure of marmesinine was determined from single microcrystal diffraction and, independently, from powder diffractionwith the aim of comparing the conformations and precision of both structural models.The single crystal experiment ( CAD-4 diffractometer, copper radiation), yielded lattice parameters a = 7.8503, b = 5.9850, c = 40.579Å, α = β = γ = 90°, in P212121 space group.The structure was solved and refined to R = 0.035, and could serve as good reference for powder methods.The powder diffraction experiments (Grochowski, Serda, Baehtz, Knapp, 2001), were done on the B2 beamline of DESY-HASYLAB (Hamburg) using wavelength 1.3572 Å and a channel-cut type analyzer crystal.The pattern was indexed with TREOR90 giving lattice parameters a = 7.8449( 3), b = 5.9903(2), c = 40.598(2)Å, α = β = γ = 90° with figure of merit M20=158, F20=506.The effective resolution of the data (d = 1.75 Å) was limited by the sample, hence structure solution was attempted by global optimization rather than direct methods.Structure solution was carried out by simulated annealing, using the program DASH ver.2.0.Several simulated annealing runs were tried to achieve the global minimum.

Crystal structure of bis[cinchoninium tetrachlorocuprate(II)] trihydrate, [(C19H24N2O)CuCl4]2-3H2O, has been determined by X-ray diffraction at 100 K and reexamined at 293 K. The compound crystallizes in orthorhombic system with a P2(1)2(1)2(1) space group and unit cell parameters a = 15.3031(14), b = 36.415(3), and c = 7.8341(5) A at 100 K, and Z = 4. The asymmetric unit consists of two (CuCl4)(2-) tetrahedral anions linked by hydrogen bonds to two doubly protonated cinchonine molecules and three water molecules. The tetrahedra are strongly flattened, to approximately D(2d) symmetry, with different deformation for two inequivalent (CuCl4)(2-) -ions in the asymmetric unit. The deformation of (CuCl4)(2-) and cinchoninium cations varies with temperature due to a rearrangement of the bifurcated hydrogen bond network. This is a continuous process observed as a monotonic variation of the EPR spectral parameters and the unit cell dimensions. EPR spectra show that very weak exchange coupling J(12) = 0.0030 cm(-1) operates between Cu(2+) ions within asymmetric units, corresponding to the general formula of the compound, as well as between equivalent Cu(2+) sites of different molecules, whereas the coupling is negligible between inequivalent sites. The intermolecular J(12) coupling is temperature-independent indicating that the whole asymmetric unit behaves as a magnetic unit (pseudodimer) in the whole temperature range.