1,3-Diphenyl-8-trifluoromethyl-1H-pyrazolo[3,4-b]quinoline

The 1H-pyrazolo­[3,4-b]quinoline (PQ) core of the title mol­ecule, C23H14F3N3, is aromatic and essentially planar (r.m.s. deviation = 0.015 Å) and the two phenyl substituents at positions 1 and 3 are twisted relative to this fragment by 29.74 (7) and 25.63 (7)°, respectively. In the crystal, mol­ecules are arranged along the b axis into stacks via [pi]-[pi] inter­actions, with an inter­planar distance of the PQ core of 3.489 (4) Å

3-Methyl-1,4-diphenyl-1H-pyrazolo­[3,4-b]quinoline

In the title mol­ecule, C23H17N3, the phenyl substituents at positions 1 and 4 are twisted relative to the central core by 27.09 (5) and 66.62 (4)°, respectively. In the crystal, mol­ecules are assembled into centrosymmetric dimers via π–π stacking inter­actions between the 1H-pyrazolo­[3,4-b]quinoline ­units, with an inter­planar distance of 3.601 (2) Å and by weak inter­molecular C—H⋯N inter­actions

(2Z)-2-Anilino-2-[oxido(phen­yl)iminio]-N-(2-pyrid­yl)acetamide methanol 0.425-solvate

The title compound, C19H16N4O2·0.425CH4O, crystallizes with two formula units per asymmetric unit. Researching its crystal structure constitutes part of a study of the nature of inter­actions between the N+—O− group and the vicinal NH group. The nitrone group and methanol solvent mol­ecules are linked via four N—H⋯O and one O—H⋯O hydrogen bonds, with donor–acceptor distances of 2.603 (3)–2.730 (3) and 2.770 (3) Å, respectively. The crystal structure also involves two intermolecular N—H⋯N hydrogen bonds

Lattice deformation of blue halite from Zechstein evaporite basin : Kłodawa Salt Mine, Central Poland

Outcrops of natural blue and purple halite crystals have been found in K ł odawa (Poland) salt deposit originating from the Permian (Zechstein) salt formation within tectonic zones. Field works carried out on various levels of K ł odawa Salt Mine indicated differencesbothinintensity ofthe hue and in the size of the outcrops. Their occurrence was connected with the presence of epigenetic sediments rich in potassium. For the samples of blue ha lite, an optical anisotropy (birefringence) was observed for both standard mineralogical thin sections and thick plates, indicating a deviation from cubic symmetry. The blue colouration of the halites, described by ultraviolet – visible spectroscopy, is due to the presence of colour centres. The colour centres have been recently identi- fied as: F, R 1 (F 3 ), R 2 (F 3 ), M and plasmons (Wese ł ucha- Birczy ń ska et al., Vib Spectrosc 60:124 – 128, 2012 ). The trace amount of impurities detected in the blue halites by means of scanning electron microscopy – energy dispersive X-ray spec- troscopy and micro-X-ray fluorescence techniques were con- nected mainly with solid inclusions such as K x Na (1 − x ) Cl, KMgCl 3 ·6H 2 O, KCl, orthorhombic sulphur, quartz and some other phases like pyrite. Crystallographic data obtained by X- ray diffraction experiments for the single crystals of the halite from K ł odawa with different saturation of blue or purple colours, as well as for natural colourless halite, revealed lowering of space-group symmetry to monoclinic, orthorhom- bic, trigonal, tetragonal or even triclinic systems while the space group typical for pure NaCl is Fm -3 m

Spectroscopic properties of halite from Kłodawa salt mine, central Poland

The dynamics of colour centre transformation was investigated in blue halite single crystals from Kłodawa Salt Mine, Central Poland, using UV-vis spectroscopy. The following colour centres were considered: F, R_{1}, R_{2}, as well as plasmons and M centres. The R_{2} centres predominated in navy blue (A) and pale blue (B) halites. Other relatively large populations were plasmons found in all examined samples. In purple (C) halite samples the plasmon population is the highest one among others and R_{1} centres appeared to be equally significant, whereas M centres were almost absent. For A and C samples unidentified bands were observed at 26,500 to 26,200 cm^{-1}, respectively. The bleaching process of the blue halites was investigated using temperature dependent UV-vis and micro-Raman spectroscopies. In micro-Raman 300-100 cm^{-1} region three very intense sharp bands were attributed to the colour centres and colloidal Na precipitation in A and B halites. The one broad band in the range 3,500 to 500 cm^{-1}, which was characteristic even for the colourless sample D but absent in the spectra of colourless NaCl obtained after recrystallization of sample A, requires further study

6-Fluoro-1,3,4-triphenyl-1H-pyrazolo[3,4-b]quinoline benzene hemisolvate

In the title compound, C28H18FN3·0.5C6H6, the 1H-pyrazolo[3,4-b]quinoline core is almost planar (r.m.s = 0.0371 Å, maximum deviation = 0.0571 Å) and aromatic. The solvent benzene mol­ecules are located around inversion centres. In the crystal, mol­ecules related by centres of symmetry form dimers, with distances of 3.932 (3) Å between best planes through the fused core due to π⋯π stacking. The phenyl substituents at positions 1, 3 and 4, are twisted away from the core, making dihedral angles of 29.66 (7), 44.59 (7) and 67.94 (6)°, respectively