The structure of the title compound, pentoxifylline, C(13)H(18)N(4)O(3), has been previously characterized as a triclinic polymorph [Pavelčík et al. (1989 ▶). Acta Cryst. C45, 836-837]. We have discovered the monoclinic form. There are no strong hydrogen bonds in the crystal structure, rather, moderate C-H⋯O hydrogen bonds are present, which serve to stabilize the three-dimensional architecture.

Tetartohedral crystal twinning is discussed as a particular case of (pseudo)merohedral twinning when the number of twinned domains is four. Tetartohedrally twinned crystals often possess pseudosymmetry, with the rotational part of the pseudosymmetry operators coinciding with the twinning operators. Tetartohedrally twinned structures from the literature are reviewed and the recent structure dete...

An organic intermolecular charge transfer complex salt of 8-Hydroxy quinolinium 4-nitrobenzoate 4-nitrobenzoic acid (OPNB) has been synthesized. Single crystals of OPNB were grown by slow solvent evaporation solution growth technique at room temperature. The (1)H and (13)C NMR spectra were recorded to confirm the molecular structure of the complex salt. The crystal structure of OPNB has been de...

THE TITLE COMPOUND (SYSTEMATIC NAME 11-cyclo-propyl-4-methyl-5,11-dihydro-6H-dipyrido[3,2-b:2',3'-e][1,4]diazepin-6-one butanol 0.3-solvate), C(15)H(14)N(4)O·0.3C(4)H(9)OH, was crystallized in a new triclinic pseudopolymorphic form, a butanol solvate, and the crystal structure determined at 150 K. The mol-ecular conformation of this new form differs from that reported previously, although the m...

A force field of the triclinic framework of AlPO(4)-34, important in methanol-hydrocarbon conversion reactions, was developed using an empirical potential function. Molecular dynamics simulation of an AlPO(4)-34 triclinic framework segment of 1216 atoms, containing the template molecules isopropylamine and water, was performed with explicit consideration of atomic charges. The average RMS diffe...

In addition to its metal-insulator transition (MIT), VO2 exhibits a rich phase behavior of insulating monoclinic (M1,M2) and triclinic (T) phases. By using micro-Raman spectroscopy and independent control of temperature and uniaxial strain in individual single-crystal microbeams, we map these insulating phases with their associated structural changes as represented by their respective phonon fr...

The title compound, C2H3N3OS, is a monoclinic (P21/c) polymorph of the previously reported triclinic structure [Kang et al. (2012 ▶). Acta Cryst. E68, o1198]. The asymmetric unit contains two independent mol-ecules which are essentially planar, with r.m.s. deviations of 0.001 and 0.032 Å from the mean plane defined by the seven non-H atoms. In the crystal, N-H⋯N and N-H⋯O hydrogen bonds link th...

A 3-hydro-4-pyridinone compound derived from maltol and dopamine has been prepared using a microwave reactor. The molecular structure of the protonated product was confirmed by single crystal X-ray diffraction. Crystals were obtained from a saturated solution of methanol and belong to the triclinic space group P-1 with unit cell parameters a = 8.3801(11) Å; b = 9.2583(12) Å; c = 11.5671(15) Å; ...

In the title compound, C(10)H(9)NO(5)S, the fused ring system and the planar (r.m.s. deviation = 0.0037 Å) methoxy-carbonyl-methyl side chain form a dihedral angle of 84.67 (10)°. The crystal structure is stabilized by inter-molecular C-H⋯O hydrogen bonds. A triclinic polymorph of the title compound is already known [Siddiqui et al. (2008 ▶). Acta Cryst. E64, o859].