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1.  Bis(2-carboxybenzo­ato-κO 1)bis­[1-cyclo­propyl-6-fluoro-4-oxo-7-(piperazin-4-ium-1-yl)-1,4-dihydro­quinoline-3-carboxyl­ato-κ2 O 3,O 4]manganese(II) dihydrate 
The title compound, [Mn(C17H18FN3O3)2(C8H5O4)2]·2H2O or [Mn(cfH)2(1,2-Hbdc)2]·2H2O (cfH = ciprofloxacin = 1-cyclo­propyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazin­yl)-3-quinoline carb­oxy­lic acid, 1,2-bdc = benzene-1,2-dicarboxyl­ate), has been prepared under hydro­thermal conditions. The Mn2+ atom, located on an inversion centre, exhibits a distorted octa­hedral geometry, coordinated by four O atoms from two symmetry-related zwitterionic ciprofloxacin ligands in the equatorial positions and two O atoms of two 1,2-Hbdc ligands in the axial positions. The complex mol­ecules are linked into a two-dimensional network through N—H⋯O and OW—H⋯O hydrogen bonds. A strong intramolecular hydrogen bond between the carboxyl/carboxylate groups of the 1,2-Hbdc anion is also present. The layers are further extended through off-set aromatic π–π stacking inter­actions of cfH groups [centroid–centroid distance of 3.657 (2) Å] into the final three-dimensional supra­molecular arrays.
PMCID: PMC3089319  PMID: 21754278
2.  7-{4-[(1,3-Benzodioxol-5-yl)meth­yl]piperazin-1-yl}-1-cyclo­propyl-6-fluoro-4-oxo-1,4-dihydro­quinoline-3-carb­oxy­lic acid 
In the title structure, C25H24FN3O5, a strong intra­molecular O—H⋯O hydrogen bond is present between the carb­oxy group at the 3-position and the carbonyl group at the 4-position. In the crystal, mol­ecules are held together by weak C—H⋯O, C—H⋯F and π–π [centroid–centroid distance 3.6080 (8) Å] inter­actions. The 1,4-dihydro­quinoline ring and cyclo­propyl group are not in the same plane, making an inter­planar angle of 57.52 (8)°.
PMCID: PMC3394047  PMID: 22798912
3.  2-(2-Chloro-6,7-dimethyl­quinolin-3-yl)-2,3-dihydro­quinolin-4(1H)-one 
In the title mol­ecule, C20H17ClN2O, the dihedral angle between the mean plane of the quinoline ring system and the benzene ring of the dihydro­quinolinone moiety is 57.84 (8)°. In the crystal, mol­ecules are linked into centrosymmetric dimers via pairs of inter­molecular N—H⋯N hydrogen bonds. These dimers are further stabilized by weak π–π stacking inter­actions between pyridine rings with a centroid–centroid distance of 3.9414 (12) Å.
PMCID: PMC3213526  PMID: 22091105
4.  1-Cyclo­propyl-6-fluoro-7-(4-nitro­so­piperazin-1-yl)-4-oxo-1,4-dihydro­quinoline-3-carboxylic acid 
The title compound, C17H17FN4O4, is a derivative of ciprofloxacin [1-cyclo­propyl-6-fluoro-4-oxo-7-(1-piperazin­yl)-1,4-dihydro­quinoline-3-carboxylic acid]. The crystal packing is stabilized by inter­molecular C—H⋯O hydrogen bonds together with π–π electron ring inter­actions [centroid–centroid separations between quinoline rings of 3.5864 (11) and 3.9339 (13) Å]. A strong intra­molecular O—H⋯O hydrogen bonds is present as well as an intra­molecular C—H⋯F inter­action.
PMCID: PMC2977261  PMID: 21583715
5.  Ethyl 1-(2,4-dichloro­benz­yl)-4-oxo-7-trifluoro­meth­yl-1,4-dihydro­quinoline-3-carboxyl­ate 
In the title compound, C20H14Cl2F3NO3, the trifluromethyl group is disordered over two sets of sites in a 0.784 (10):0.216 (10) ratio. The quinoline ring system is essentially planar with a maximum deviation of 0.058 (2) Å for the N atom and forms dihedral angles of 89.23 (11) and 8.13 (17)°, respectively with the mean planes of the benzene ring and the carboxyl­ate group. In the crystal, pairs of weak C—H⋯O and C—H⋯F hydrogen bonds link mol­ecules into centrosymmetric dimers. The crystal structure is further stabilized by weak π–π [centroid–centroid distance = 3.624 (2) Å] inter­actions.
PMCID: PMC3275192  PMID: 22347048
6.  Moxifloxacinium chloride monohydrate 
The title compound {systematic name: 7-[(1S,6S)-8-aza-2-azonia­bicyclo­[4.3.0]non-8-yl]-1-cyclo­propyl-6-fluoro-8-meth­oxy-4-oxo-1,4-dihydro­quinoline-3-carb­oxy­lic acid chloride monohydrate}, C21H25FN3O4 +·Cl−·H2O, crystallizes with two moxi­floxa­cinium cations, two chloride ions and two uncoordinated water mol­ecules in the unit cell. The crystal structure has a pseudo-inversion center except for the chloride ions. In both moxi­floxa­cinium cations, the quinoline rings are approximately planar, the maximum atomic deviations being 0.107 (3) and 0.118 (3) Å. The piperidine rings adopt a chair conformation while the pyrrolidine rings display a half-chair conformation. In the crystal, the carboxyl groups, the protonated piperidyl groups, the uncoordinated water mol­ecule and chloride anions participate in O—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonding; weak inter­molecular C—H⋯O and C—H⋯Cl hydrogen bonding is also present in the crystal structure.
PMCID: PMC3201314  PMID: 22058817
7.  Poly[[[(1-ethyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydro­quinoline-3-carboxyl­ato)manganese(II)]-μ3-4,4′-oxydibenzoato] monohydrate] 
In the title compound, {[Mn(C16H18N3O3)(C14H8O5)]·H2O}n, the unique MnII ion is coordinated by two O atoms from a chelating 1-ethyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydro­quinoline-3-carboxyl­ate ligand and three O atoms from three 4,4′-oxydibenzoate ligands, forming a distorted square-pyramidal coordination environment. In the crystal structure, centrosymmetric dinuclear manganese units are linked via 4,4′-oxydibenzoate ligands into one-dimensional chains; these chains are, in turn, connected via inter­molecular N—H⋯O and O—H⋯O hydrogen bonds to form a two-dimensional supra­molecular network. The O atom of the solvent water mol­ecule is disordered over two sites with equal occupancies; the attached H atoms are common to both sites.
PMCID: PMC2914913  PMID: 21200557
8.  2-(4-Chloro­phen­yl)-2,3-di­hydro­quinolin-4(1H)-one 
The title mol­ecule, C15H12ClNO, features a di­hydro­quinolin-4(1H)-one moiety attached to a chloro­benzene ring. The heterocyclic ring has a half-chair conformation with the methine C atom lying 0.574 (3) Å above the plane of the five remaining atoms (r.m.s. deviation = 0.0240 Å). The dihedral angles between the terminal benzene rings is 77.53 (9)°, indicating a significant twist in the mol­ecule. In the crystal, supra­molecular zigzag chains along the c-axis direction are sustained by N—H⋯O hydrogen bonds. These are connected into double chains by C—H⋯π inter­actions.
PMCID: PMC3998350  PMID: 24764911
9.  Ethyl 6-chloro-2-oxo-4-phenyl-1,2-dihydro­quinoline-3-carboxyl­ate 
In the title compound, C18H14ClNO3, the dihydro­quinolin-2-one ring system is almost planar (r.m.s. deviation = 0.033 Å). The carboxyl­ate plane and the phenyl group are twisted away from the dihydro­quinolin-2-one ring system by 50.3 (1) and 64.9 (1)°, respectively. In the crystal structure, inversion-related mol­ecules form R 2 2(8) dimers via pairs of N—H⋯O hydrogen bonds.
PMCID: PMC2972051  PMID: 21578727
10.  Enrofloxacin hydro­chloride dihydrate 
The asymmetric unit of the title compound, C19H23FN3O3 +·Cl−·2H2O [systematic name: 4-(3-carb­oxy-1-cyclo­propyl-6-fluoro-4-oxo-1,4-di­hydro­quin­o­lin-7-yl)-1-ethyl­piperazin-1-ium chloride dihydrate], consists of two independent monocations of the protonated enrofloxacin, two chloride anions and four water mol­ecules. In the cations, the piperazinium rings adopt chair conformations and the dihedral angles between the cyclo­propyl ring and the 10-membered quinoline ring system are 56.55 (2) and 51.11 (2)°. An intra­molecular O—H⋯O hydrogen bond is observed in each cation. In the crystal, the components are connected via O—H⋯Cl, N—H⋯Cl and O—H⋯O hydrogen bonds, and a π–π inter­action between the benzene rings [centroid–centroid distance = 3.6726 (13) Å], resulting in a three-dimensional array.
PMCID: PMC3998605  PMID: 24826167
11.  8-{1-[(4′-Fluoro-[1,1′-biphen­yl]-4-yl)meth­yl]piperidin-4-yl}-3,4-di­hydro­quinolin-2(1H)-one chloro­form 0.25-solvate 
In the asymmetric unit of the title compound, C27H27FN2O·0.25CHCl3, there are two independent mol­ecules (A and B) together with a partially disordered chloro­form mol­ecule situated about an inversion center. The conformation of the two mol­ecules is very similar. The bridging piperidine rings each have a chair conformation while the piperidin-2-one rings of the quinoline moiety have screw-boat conformations. The benzene rings of the biphenyl moiety are inclined to one another by 26.37 (4) and 23.75 (15)° in mol­ecules A and B, respectively. The mean plane of the central piperidine ring [r.m.s. deviation = 0.241 (2) Å in both mol­ecules A and B] is inclined to the benzene ring of the quinoline moiety by 80.06 (4) in A and 83.75 (15)° in B, while it is inclined to the adjacent benzene ring of the biphenyl group by 73.623 (15) in A and 75.65 (14)° in B. In the crystal, individual mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming A–A and B–B inversion dimers with R 2 2(8) ring motifs. The dimers are stabilized by C—H⋯O hydrogen bonds and linked via C—H⋯F and C—H⋯N hydrogen bonds into a three-dimensional network. Several C—H⋯π inter­actions are also present.
PMCID: PMC3998275  PMID: 24764836
12.  Ethyl 1-cyclo­propyl-6,7-difluoro-8-meth­oxy-4-oxo-1,4-dihydro­quinoline-3-carboxyl­ate 
In the title compound, C16H15F2NO4, the dihedral angle between the three-membered ring and the quinoline ring system is 64.3 (3)°. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules, forming a column running along [101].
PMCID: PMC2959496  PMID: 21581071
13.  Aqua­bis[1-ethyl-6-fluoro-7-(4-methyl­piperazin-1-yl)-4-oxo-1,4-dihydro­quinoline-3-carboxyl­ato]zinc(II) dihydrate 
The title compound, [Zn(C17H19FN3O3)2(H2O)]·2H2O or [Zn(pef)2(H2O)]·2H2O, where pef is 1-ethyl-6-fluoro-7-(4-methyl­piperazin-4-yl)-4-oxo-1,4-dihydro­quinoline-3-carb­oxyl­ate, was synthesized under hydro­thermal conditions. The ZnII atom exhibits a distorted ZnO5 square-pyramidal geometry defined by two bidentate O,O-bonded pef anions in the basal plane and one water mol­ecule in the apical position. A network of O—H⋯O and O—H⋯N hydrogen bonds is formed between the ZnII complexes and the uncoordinated water mol­ecules.
PMCID: PMC2960459  PMID: 21201277
14.  Tetra­aqua­bis(2-oxo-1,2-dihydro­quinoline-4-carboxyl­ato-κO 4)nickel(II) 
In the title compound, [Ni(C10H6NO3)2(H2O)4], the central NiII atom is located on an inversion center and coordinated in a slightly distorted octa­hedral geometry by two O atoms from two 2-oxo-1,2-dihydro­quinoline-4-carboxyl­ate ligands and four water mol­ecules, all of which act as monodentate ligands. The crystal structure features an extensive network of inter­molecular hydrogen-bonding inter­actions (O—H⋯O and N—H⋯O) and offset face-to-face π–π stacking inter­actions [centroid–centroid distances = 3.525 (3) and 3.281 (5) Å].
PMCID: PMC2960272  PMID: 21201341
15.  Diaqua­bis­[1-ethyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxyl­ato]magnesium(II) hexa­hydrate 
In the title compound, [Mg(C16H17FN3O3)2(H2O)2]·6H2O, the Mg2+ ion (site symmetry ) exhibits a distorted MgO6 octa­hedral geometry defined by two O,O-bidentate 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazin­yl)-3-quinoline-carb­oxyl­ate (norf) anions and two water mol­ecules. In the crystal, O—H⋯O and O—H⋯N hydrogen bonds help to establish the packing.
PMCID: PMC3009197  PMID: 21588825
16.  Poly[[[[1-ethyl-6,8-difluoro-7-(3-methyl­piperazin-1-yl)-4-oxo-1,4-dihydro­quinoline-3-carboxyl­ato]cadmium]-μ-benzene-1,4-dicarboxyl­ato] trihydrate] 
In the title layered coordination polymer, {[Cd(C17H18F2N3O3)(C8H4O4)]·3H2O}n, the CdII atom exhibits a very distorted CdO6 octa­hedral geometry defined by one O 3,O 4-bidentate 1-ethyl-6,8-difluoro-7-(3-methyl­piperazin-1-yl)-4-oxo-1,4-dihydro­quinoline-3-carboxyl­ate (lome) ligand, one O,O′-bidentate benzene-1,4-dicarboxyl­ate (bdc) dianion and two O-monodentate bdc dianions. Both the bdc species in the asymmetric unit are completed by crystallographic inversion symmetry. The bridging bdc dianions link the cadmium nodes into a recta­ngular grid lying parallel to (01). A network of N—H⋯O and O—H⋯O hydrogen bonds helps to establish the packing.
PMCID: PMC3009166  PMID: 21588904
17.  rac-2-(2-Chloro-6-methyl­quinolin-3-yl)-2,3-dihydro­quinolin-4(1H)-one 
In the title compound, C19H15ClN2O, the quinoline ring forms a dihedral angle of 43.24 (1)° with the benzene ring of the dihydroquinolinyl system. In the crystal, mol­ecules are linked through a single weak C—H⋯O hydrogen bond, forming ribbons which extend along (100), giving alternating zigzag mol­ecular layers which stack down the b-axis direction.
PMCID: PMC3379295  PMID: 22719493
18.  Ethyl 8-meth­oxy-4-oxo-1,4-di­hydro­quinoline-3-carboxyl­ate 
In the title compound, C13H13NO4, the asymmetric unit contains four independent mol­ecules, each exhibiting an intra­molecular N—H⋯O hydrogen bond. The ethyl group in one of the four mol­ecules is disordered, with a refined occupancy ratio of 0.295 (16):0.705 (16). A face-to-face stacking inter­action is found between the benzene rings of the quinoline units of two of the mol­ecules [centroid–centroid distance = 3.541 (2) Å], which are sandwiched by the other two mol­ecules through N—H⋯O hydrogen bonding. In the crystal, the sandwiched mol­ecules are assembled via stacking inter­actions along the b-axis direction with their translation-symmetry equivalents [centroid–centroid distance = 3.529 (2) Å], and are further linked through N—H⋯O hydrogen bonding. The other two mol­ecules are linked via stacking inter­actions with their inversion-symmetry equivalents [centroid–centroid distances = 3.512 (3) and 3.716 (4) Å] and via N—H⋯O hydrogen bonding.
PMCID: PMC4051033  PMID: 24940288
19.  Bis[(2R,6S)-4-(5-amino-3-carb­oxy-1-cyclo­propyl-6,8-difluoro-4-oxo-1,4-dihydro­quinolin-7-yl)-2,6-dimethyl­piperazin-1-ium] sulfate penta­hydrate 
The title compound, C19H23F2N4O3 +·0.5SO4 2−·2.5H2O, an anti­bacterial fluoro­quinolone, crystallized as a racemic twin (major twin component = 0.633) in the chiral space group P1. The asymmetric unit contains two sparfloxacinium cations, one sulfate anion and five mol­ecules of water of solvation. The bond lengths and angles of both cations are almost identical. The quinoline ring systems in the cations are essentially planar, the mean deviations from the best plane being 0.045 (2) and 0.054 (2) Å and make π–π inter­actions with each other [centroid–centroid distances of 3.692 (4) Å and 3.744 (4) Å]. The crystal structure features inter­molecular O—H⋯O, O—H⋯S, N+—H⋯O, N+—H⋯S and N—H⋯O hydrogen bonds together with intra­molecular O—H⋯O and N—H⋯O hydrogen bonds. As a result, a three-dimensional supra­molecular structure is observed.
PMCID: PMC3239011  PMID: 22199860
20.  Ethyl 4-oxo-8-trifluoro­methyl-1,4-dihydro­quinoline-3-carboxyl­ate 
The asymmetric unit of the title compound, C13H10F3NO3, contains two independent mol­ecules with similar conformations. In the crystal, N—H⋯O hydrogen bonds link alternating independent mol­ecules into chains in [-110]. In the chain, the quinoline planes of the independent mol­ecules are almost perpendicular to each other, forming a dihedral angle of 89.8 (1)°. π–π inter­actions between the aromatic rings of quinoline bicycles related by inversion centres [for two independent centrosymmetric dimers, the shortest centroid–centroid distances are 3.495 (1) and 3.603 (1) Å] link the hydrogen-bonded chains into layers parallel to (110). Weak C—H⋯F and C—H⋯O inter­actions further consolidate the crystal packing.
PMCID: PMC3588845  PMID: 23468810
21.  2-p-Tolyl-2,3-di­hydro­quinolin-4(1H)-one 
In the title mol­ecule, C16H15NO, the tetra­hydro­pyridine ring is in a sofa conformation with the methine C atom forming the flap. The dihedral angle between the benzene rings is 80.85 (8)°. In the crystal, mol­ecules are arranged in alternating double layers parallel to (100) and are connected along [001] by N—H⋯O hydrogen bonds. In addition, weak C—H⋯π inter­actions are observed.
PMCID: PMC3998357  PMID: 24764918
22.  7-[(7S)-7-Aza­niumyl-5-aza­spiro­[2.4]hept-5-yl]-8-chloro-6-fluoro-1-[(1S,2R)-2-fluoro­cyclo­prop­yl]-4-oxo-1,4-dihydroquinoline-3-carboxyl­ate methanol monosolvate 
Sitafloxacin is a newly developed fluoro­quinolone anti­bacterial drug. The crystal studied, C19H18ClF2N3O3·CH3OH, consists of one mol­ecule of sitafloxacin and one methanol solvent mol­ecule. The mol­ecule of sitafloxacin is a zwitterion with a protonated primary amine group and a deprotonated carboxylate group. The cyclopropane ring and the CO2 group make dihedral angles of 79.5 (3) and 35.4 (4)°, respectively, with the fused ring system. The supra­molecular structure is defined by N—H⋯O and O—H⋯O hydrogen bonds.
PMCID: PMC3435823  PMID: 22969669
23.  Enrofloxacinium picrate 
There is one cation–anion pair in the asymmetric unit of the title compound [systematic name: 4-(3-carb­oxy-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)-1-ethyl­piperazin-1-ium 2,4,6-tri­nitro­phenolate], C19H23FN3O3 +·C6H2N3O7 −. The six-membered piperazine group in the cation adopts a slightly distorted chair conformation and contains a protonated N atom. The dihedral angles between the mean planes of the cyclo­propyl and piperazine rings in the cation with the 10-atom ring system of the quinolone group are 48.1 (1) and 69.9 (5)°, respectively. The picrate anion inter­acts with the protonated N atom of an adjacent cation through a bifurcated N—H⋯O three-center hydrogen bond, forming an R 1 2(6) ring motif. Furthermore, there is an intra­molecular O—H⋯O hydrogen bond. The dihedral angle between the mean planes of the anion benzene and cation piperizine, quinoline and cyclo­propyl rings are 61.3 (6), 31.1 (4) and 70.4 (9)°, respectively. The mean planes of the two o-NO2 and single p-NO2 groups in the picrate anion are twisted by 6.7 (6), 38.3 (9) and 12.8 (7)° with respect to the mean plane of the benzene ring. Strong N—H⋯O and weak inter­molecular C—H⋯O hydrogen bonds in concert with weak π–π stacking inter­actions [centroid–centroid distances = 3.5785 (13), 3.7451 (12) and 3.6587 (13) Å] dominate the crystal packing.
PMCID: PMC3051675  PMID: 21523099
24.  Ethyl 6-(4-chloro­phen­yl)-4-(4-fluoro­phen­yl)-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate 
The asymmetric unit of the title compound, C21H18ClFO3, contains two independent mol­ecules. In one mol­ecule (A), the 4-chloro­phenyl, oxo­cyclo­hex-3-ene, carboxyl­ate, and ethyl groups were refined as disordered over two sets of sites with a 0.684 (5):0.316 (5) ratio. The cyclo­hexene ring in the disordered mol­ecule is in a slightly distorted envelope conformation for the major component (with the C atom bound to the carboxylate group being the flap atom) and in a screw-boat conformation for the minor component. In the ordered mol­ecule (B), the cyclo­hexene ring is in a half-chair conformation. The dihedral angles between the mean planes of the fluoro- and chloro-substituted benzene rings are 89.9 (7) (only the major component is considered for A) and 76.4 (7)° (B). In the crystal, inversion dimers are observed along with weak C—H⋯O hydrogen bonds, which form chains along [100].
PMCID: PMC3885083  PMID: 24454259
25.  catena-Poly[[aqua­bis­(3-chloro­benzoato-κ2 O,O′)cadmium]-μ-N,N-di­ethyl­nico­tin­amide-κ2 N 1:O] 
In the crystal of the title CdII polymeric complex, [Cd(C7H4ClO2)2(C10H14N2O)(H2O)]n, the CdII cation is chelated by two chloro­benzoate anions and coordinated by two N,N-di­­ethyl­nicotinamide (DENA) ligands and one water mol­ecule in a distorted NO6 penta­gonal–bipyramidal geometry. The CdII cations are bridged by the pyridine N atom and carbonyl O atom of the DENA ligand to form a polymeric chain running along the b axis. Inter­molecular O—H⋯O hydrogen bonds between coordinating water mol­ecules and carboxyl­ate groups link adjacent chains into layers parallel to the bc plane. π–π contacts between benzene rings [shortest centroid–centroid distance = 3.912 (2) Å] further stabilizes the crystal structure. In the mol­ecule, weak C—H⋯O hydrogen bonds occur between the pyridine ring and carboxyl­ate groups; the dihedral angles between the carboxyl­ate groups and adjacent benzene rings are 4.6 (3) and 12.8 (3)°, while the benzene rings are oriented at a dihedral angle of 1.89 (13)°.
PMCID: PMC3793697  PMID: 24109284

Results 1-25 (170796)