β-Polymorph of phenazepam: a powder study

The title compound [systematic name: 7-bromo-5-(2-chloro­phen­yl)-1H-1,4-benzodiazepin-2(3H)-one] (β-polymorph), C15H10BrClN2O, has been obtained via cryomodification of the known α-polymorph of phenazepam [Karapetyan et al. (1979 ▶). Bioorg. Khim. 5, 1684–1690]. In both polymorphs, the mol­ecules, which differ only in the dihedral angles between the aromatic rings [75.4 (2)° and 86.2 (3)° in the α- and β-polymorphs, respectively], are linked into centrosymmetric dimers via N—H⋯O hydrogen bonds. In the crystal structure of the β-polymorph, weak inter­molecular C—H⋯O hydrogen bonds further link these dimers into layers parallel to bc plane

New Polymorph of Dehydroepiandrosterone Obtained via Cryomodification

A new anhydrous polymorph of dehydroepiandrosterone (DHEA) is detected in cryomodified powder samples and designated as form VII. The crystal structure of form VII is determined from multiphase X-ray powder diffraction (XRPD) data. Additionally, the unknown crystal structures of anhydrous form III and the new monohydrated DHEA form designated as form S5 are also determined from multiphase XRPD data. To validate the crystal structures III, VII, and S5, energy minimization with dispersion-corrected density functional theory is performed in VASP. An extended list of the DHEA forms with the known crystal structures, which now covers anhydrous forms I, II, III, VI, and VII and solvated forms S1, S2, S4 and S5, allows quantification of DHEA solid-state transformations to be carried out

Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation

Codeposition of a monatomic lanthanide vapour (Sm, Eu, Tm or Yb) and tri-tert-butylbenzene C6H3-tBu 3-1,3,5 onto a cold (77 K) surface affords matrices that contain zerovalent bis(¿-arene)lanthanide complexes of the form [Ln(¿6-C6H3-tBu 3-1,3,5)2] as formed in macroscale co-condensation reactions using metal vapour synthetic (MVS) techniques. The reproduction of the experiments in the 77 K matrix allows the detailed characterization of thermally unstable members of the series that were previously not possible. The bis(arene) sandwich complexes [Ln(¿6-C6H3-tBu 3-1,3,5)2] (Ln=Sm, Eu) are stable at low temperatures, but may not be the only products of the cocondensation reactions, while the analogues [Ln(¿6-C6 H3-tBu3-1,3,5)2] (Ln=Tm or Yb) cannot be made at liquid nitrogen temperatures. By replacement of tri-tert-butylbenzene with N- and P-substituted heteroarenes NC5H2-tBu3-2,4,6 and PC5H2-tBu3-2,4,6, the relative stabilities of these zerovalent complexes have been determined. Lanthanum vapour was also cocondensed with the arenes using MVS techniques, and the crude product extracted directly from the machine was analysed in solution at -78 °C. There is very little difference in thermal stability between carbocyclic and heteroaromatic sandwich derivatives of an individual metal. © 2003 Elsevier B.V. All rights reserved