3-(2-Chloro­ethyl)-2-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidinium 2,4,6-trinitro­phenolate

In the cation of the title salt, C11H12ClN2O+·C6H2N3O7 −, the chloro­ethyl side chain is in a syn conformation, nearly orthogonal to the pyrimidine ring, with a dihedral angle of 78.9 (6)° between the plane of the chloro­ethyl chain and the pyrimidine ring. The dihedral angle between the fused rings is 4.3 (3)°. In the picrate anion, the benzene mean plane makes dihedral angles of 26.7 (1), 33.6 (2) and 5.3 (6)° with the two o-NO2 groups and the p-NO2 group, respectively. Extensive hydrogen-bond inter­actions occur between the cation–anion pair which help to establish the crystal packing. A three-center O⋯(H,H)—(N,C) acceptor hydrogen bond is observed between the phenolate O atom of the picrate anion and the amine and methyl groups of the cation. An N—H⋯(O,O) bifurcated hydrogen bond is observed between the amine group and two O atoms from the phenolate and o-NO2 groups

Gabapentin-lactum–chloranilic acid (1/1)

In the title compound, C9H15NO·C6H2Cl2O4 [sytematic name: 2-aza­spiro­[4.5]decan-3-one–chloranilic acid (1/1)], the cyclo­hexane ring of the lactam molecule adopts a slightly distorted normal chair conformation and the five-membered 3-aza­spiro ring is in a slightly distorted chair conformation. The dihedral angle between the least-squares planes of the cyclohexane and 3-azaspiro rings is 84.0 (3)°. In the crystal, the chloranilic acid mol­ecule and the gabapentin-lactum mol­ecules are held together by strong inter­molecular N—H⋯O and O—H⋯O hydrogen bonds with two bifurcated O acceptor atoms on the chloranilic acid mol­ecule and one on the gabapentin-lactum mol­ecule, each bonding with an inter- and intra­molecular hydrogen bond. The molecules are linked into chains parallel to (011) and propagating along the b axis

4-(4-Chloro­phen­yl)-1-[3-(4-fluoro­benzo­yl)prop­yl]-4-hydroxy­piperidin-1-ium 2,4,6-trinitro­phenolate (haloperidol picrate)

In the title salt, C21H24ClFNO2 +·C6H2N3O7 −, the dihedral angle between the aromatic rings in the cation is 16.5 (1)°. The piperidium ring adopts a slightly distorted chair conformation. Strong hydrogen-bonding inter­actions occur between the N—H and O—H functions of the 4-hydroxy­piperidin-1-ium ring and the phenolate and p-NO2 O atoms of the picrate anion. In addition, a variety of weak C—H⋯O and π–π ring inter­actions between cations and cation–anion neighbors [centroid–centroid distances = 3.597 (1) and 3.848 (10) Å] further consolidate the packing

Redetermination of 5α-androstane-3,17-dione

The structure of the title compound, C19H28O2, has been redermined at 295 (2) K, with much improved precision. The structure and mol­ecular packing of the title compound was first reported by Coiro et al. [Acta Cryst. (1973). B29, 1404–1409] by means of potential-energy calculations. The cell parameters in this study differ considerably in space group C2. It is a derivative of testosterone and consists of a cyclo­penta­none ring (A) fused to to successive cyclo­hexane (B and C) and cyclo­hexa­none (D) rings. The three cyclo­hexa­none rings are in slightly distorted boat configurations and the cyclo­penta­none ring is a distorted half-chair. The crystal packing is stabilized by weak inter­molecular C—H⋯O inter­actions involving O atoms from each of the cyclo­hexa­none and cyclo­penta­none rings and H atoms from each of their respective rings

Lomefloxacinium picrate

In the cation of the title compound [systematic name: (RS)-4-(3-carb­oxy-1-ethyl-6,8-difluoro-4-oxo-1,4-dihydro­quinolin-7-yl)-2-methyl­piperazin-1-ium 2,4,6-trinitro­phenolate], C17H20F2N3O3 +·C6H2N3O7 −, the piper­azine ring adopts a slightly distorted chair conformation and contains a protonated N atom. An intra­molecular O—H⋯O hydrogen bond occurs in the cation. The dihedral angles between the mean planes of the six-atom piperazine ring and the 10-atom fused ring system is 43.3 (5)°. The picrate anion inter­acts with the protonated N atom of an adjacent cation through a bifurcated N—H⋯(O,O) three-center hydrogen bond. Strong N—H⋯O hydrogen bonds in concert with weak π–π stacking inter­actions [centroid–centroid distance = 3.6460 (14) Å] dominate the crystal packing, creating a two-dimensional network structure along [011]

2-Bromo-1,3-bis­(4-chloro­phen­yl)prop-2-en-1-one

In the title compound, C15H9BrCl2O, the two benzene rings are twisted from each other with a dihedral angle of 47.33 (8)°. The crystal structure is stabilized by aromatic π–π inter­actions between the benzene rings of neighbouring mol­ecules [centroid–centroid distance = 3.680 (2) Å], and by weak inter­molecular C—H⋯O and C—H⋯Cl inter­actions. Additionally, the crystal structure exhibits a short intra­molecular C—H⋯Br contact (H⋯Br = 2.69 Å)

4-(4-Carb­oxy­benz­yl)-1-methyl­piperazin-1-ium picrate

The title compound, C13H19N2O2+·C6H2N3O7−, is a salt obtained by cocrystallization of 4-[(4-methyl­piperazin-1-yl)meth­yl]benzoic acid and picric acid. The cations adopt an `L-shaped' conformation and are linked into chains along [010] by O—H⋯N hydrogen bonds. The NH group of each piperazinium ring forms a hydrogen bond to the phenolate O atom of a picrate anion, and the picrate anions form face-to-face contacts with an inter­planar separation of 3.023 (1) Å

Dibenzo[b,e]thiepin-11(6H)-one

In the title compound, C14H10OS, the seven-membered thiepin ring adopts a distorted boat conformation with the dihedral angle between the mean planes of the two fused benzene rings being 56.5 (1)°

1-(1,3-Benzodioxol-5-yl)ethanone

In the title compound, C9H8O3, the dihedral angle between the mean planes of the benzene and dioxole rings is 1.4 (8)°, with the dioxole group in a slightly distorted envelope configuration with the flap C atom displaced by 0.0645 Å from the plane through the other four atoms. In the crystal, weak inter­molecular C—H⋯O hydrogen-bond inter­actions link the mol­ecules into chains propagating in [011]. The crystal packing exhibits weak π–π inter­actions as evidenced by the relatively short distances [3.801 (9) Å] between the centroids of adjacent benzene rings

N,N′-Bis­[(E)-2-fluoro­benzyl­idene]-1-(2-fluoro­phen­yl)methane­diamine

In the title compound, C21H15F3N2, the benzene ring bonded to the central C atom forms dihedral angles of 77.5 (7) and 89.0 (5)°, respectively, with the remaining two benzene rings. Weak inter­molecular C—H⋯F hydrogen bonds link the mol­ecules into chains propagated in [101]. The crystal packing exhibits weak π–π inter­actions as evidenced by relatively short distances between the centroids of the aromatic rings [3.820 (7) and 3.971 (5) Å]. A MOPAC PM3 optimization of the mol­ecular geometry in vacuo supports a suggestion that inter­molecular forces have a significnt influence on the mol­ecular conformation in the crystal