Remarkable π–π stacking of dipyrido[f,h]quinoxaline‐6,7‐dicarbonitrile in its ethanol solvate

The title compound, C₁₆H₆N₆·C₂H₆O, is an ethanol solvate of an aromatic phenanthroline‐based flat ligand. The latter exhibits a remarkable π–π stacking in the crystal structure, with interplanar distances of 3.27 and 3.40 Å, which directs the columnar organization of the ligands. The ethanol solvent molecule is located in channels between these columns, being hydrogen bonded to one of the N‐atom sites of the phenanthroline fragment.     

Hydrogen‐bonding versusπ–π stacking interactions in dipyrido[f,h]quinoxaline‐6,7‐dicarbonitrile and 6,7‐dicyanodipyrido[f,h]quinoxalin‐1‐ium chloride dihydrate

The solvent‐free title compound, C₁₆H₆N₆, is an aromatic derivative of phenanthroline with an extended π system. It exhibits a remarkable π–π columnar stacking in the crystal structure, with interplanar distances of 3.229 (3) and 3.380 (3) Å, the shorter spacing being between the two molecules within the asymmetric unit. Adjacent units along the stacked arrays are rotated in‐plane with respect to one another by approximately 120°. The hydrochloride derivative, C₁₆H₇N₆⁺·Cl⁻·2H₂O, in which one of the phenanthroline N atoms has been protonated, crystallized as a dihydrate. The supramolecular organization in this compound is characterized by continuous hydrogen bonding between the component species, yielding two‐dimensional hydrogen‐bonded networks. This study demonstrates the high significance of the π–π stacking interactions in the solvent‐free aromatic system and how they can be undermined by introducing hydrogen‐bonding capacity into the ligand.     

2,5‐Dimethyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline and 2‐tert‐butyl‐5‐methyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline

In both 2,5‐dimethyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline, C₁₆H₁₅N₃, (I), and 2‐tert‐butyl‐5‐methyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline, C₁₉H₂₁N₃, (II), which crystallizes with Z′ = 2 in the space group P, the non‐aromatic carbocyclic rings adopt screw‐boat conformations. The molecules of (I) are linked into chains of rings by a combination of C—H...N and C—H...π(arene) hydrogen bonds, while in (II) there are no hydrogen bonds of any kind.     

Synthesis and biological evaluation of new benzo[f]furo[2,3‐h]‐and benzo[f]pyrano[2,3‐h]coumarin derivatives.

Furocoumarins 3,5 and pyranocoumarin 7 were synthesized from the reaction of furonaphthalenediones 2,4 and pyranonaphthalenedione 6 respectively with carbethoxymethylene(triphenyl)phosphorane in refluxing DCM for 3‐6 hours or under microwave irradiation in toluene for a few minutes. Compounds 3,5,7 and their precursors were tested as anti‐inflammatory/antioxidant agents. They were found to compete significantly high DMSO for OH radicals, to scavenge O₂^? and to inhibit lipoxygenase to a high extent.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 22 Dibenzo[f,h]benzothieno[2,3‐c]quinoline,dibenzo[f,h]benzothieno[2,3‐c][1,2,4]triazolo[4,3‐a]quinoline and dibenzo[f,h]naphtho[2′,1′:4,5]thieno[2,3‐c]quinoline

Photocyclization of 3‐chloro‐N‐(9‐phenanthryl)benzo[b]‐thiophene‐2‐carboxamide ( 3 ) and 3‐chloro‐N‐(9‐phenanthryl)‐naphtho[1,2‐b]thiophene‐2‐carboxamide ( 10 ) yielded dibenzo[f,h]benzothieno[2,3‐c]‐quinolin‐10(9H)‐one ( 4 ) and dibenzo[f,h]naphtho[2′,1′:4,5]thieno[2,3‐c]quinolin‐10(9H)‐one ( 11 ), respectively. Further elaboration of the lactams provided three novel unsubstituted new ring systems.     

Synthesis of new benzo[h]‐ and benzo[f]chromeno[2,3‐b]‐pyridine‐5‐ones

A number of new benzo[h]‐ and benzo[f]chromeno[2,3‐b] pyridine‐5‐ones derivatives were synthesized from benzo[h]‐ and benzo[f]‐chromone‐carbonitriles and amino‐benzo[h]‐ and benzo[f]chromone‐carbaldehydes. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:2–7, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20152     

Hydrogen bonding in dibromo[2‐(dimethyl­aminomethyl)phenyl][2‐(dimethylammoniomethyl)phenyl]tin(IV) tetra­bromo­[2‐(dimethyl­aminomethyl)phenyl]­tin(IV)

The mol­ecular structure of the title compound, [SnBr₂(C₉H₁₂N)(C₉H₁₃N)][SnBr₄(C₉H₁₂N)], consists of a dibromo­bis[2‐(dimethyl­aminomethyl)phenyl][2‐dimethylammoniomethyl)phenyl]tin(IV) cation and a tetra­bromo­[2‐(dimethyl­aminomethyl)phenyl]tin(IV) anion. As a result of strong intra­molecular N→Sn inter­actions, distorted trigonal–bipy­ramidal and octa­hedral coordination geometries are established for the metal centres of the diorganotin(IV) and monoorganotin(IV) fragments, respectively. The cation and anion are linked together by two Br⋯H contacts, while three additional similar contacts result in a dimeric fragment which repeats in a two‐dimensional supra­molecular arrangement.     

Crystallographic report: Crystal structure of bis[dipyrido[3,2,‐a:2′,3′‐c]phenazine]lead(II)diiodide

The mononuclear lead(II) complex of formula [PbI₂(DPPZ)₂] (DPPZ = dipyrido[3,2,‐a:2′,3′‐c]phenazine) has two‐fold symmetry and features a distorted octahedral geometry for lead defined by an N₄I₂ donor set. Copyright © 2004 John Wiley & Sons, Ltd.     

Hydrogen‐bonding patterns in bis[2,4,6‐triazaniumylcyclohexane‐1,3,5‐tris(olate)‐κ3O,O′,O′′]germanium(IV) tetrachloride hexahydrate

A first preliminary report on the crystal structure of a hydrated salt formulated as [Ge(taci)₂]Cl₄·13H₂O (taci is 1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol) appeared more than 20 years ago [Ghisletta (1994). PhD thesis, ETH Zürich. Switzerland]. At that time it was not possible to discriminate unambiguously between the positions of some of the chloride ions and water O atoms, and disorder was thus postulated. In a new determination, a conclusive scheme of hydrogen bonding proves to be a particularly appealing aspect of the structure. Single crystals of the title compound, C₁₂H₃₀GeN₆O₆⁴⁺·4Cl⁻·6H₂O or [Ge(taci)₂]₂Cl₈·12H₂O, were grown from an aqueous solution by slow evaporation of the solvent. The two [Ge(taci)₂]⁴⁺ cations exhibit a double‐adamantane‐type structure with exclusive O‐atom coordination and approximate D_3d symmetry. The taci ligands adopt a zwitterionic form with deprotonated hydroxy groups and protonated amino groups. Both cations are hydrogen bonded to six water molecules. The structure of the hydration shell of the two cations is, however, slightly different. The {[Ge(taci)₂]·6H₂O}⁴⁺ aggregates are interlinked in all three dimensions by further hydrogen bonds of the types N—H...Cl...H—N, N—H...O(H)₂...H—N, (Ge)O...H—O(H)...H—N, N—H...O(H)—H...Cl...H—N, (Ge)O...H—O—H...Cl...H—N, N—H...O(H)—H...Cl...H—(H)O...H—N, (Ge)O...H—O—H...Cl...H—(H)O...H—N and Ge(O)...H—O—H...Cl...H—O—H...O(Ge).     

Reactions of collman complex with tin(IV) and germanium(IV) porphyris,formation of [tin(II) and germanium(II) porphyrins] tetracarbonyliron and crystal structure of [2,3,7,8,12,13,17,18-octaethylporphinato tin(II)] tetracarbonyliron

The action of Na₂Fe(CO)₄ with tin(IV) and germanium(IV) porphyrins affords metal(II) porphyrin complexes [(por)M(II)Fe(CO)₄] (por = porphyrinate, M - Sn(II) or Ge(II)). The molecular structure of [(oep)Sn(II)Fe(CO)₄] was solved by X-ray diffraction techniques. The molecular structure of [(oep)Sn(II)Fe(CO)₄] was solved by X-ray diffraction techniques : the Sn coordination is square pyramidal with the iron in axial position (Sn-Fe = 2.492(1)Å) whereas the Fe coordination is trigonal bipyramidal. Mössbauer parameters provide convincing evidence for the formal zero oxidation state of the iron atom.     

Diiodobis(4‐methylpentan‐2‐onato‐C4,O)tin(IV): a comparison with diiodobis(3‐methoxy‐3‐oxopropyl‐C,O)tin(IV)

The title compound, [SnI₂(C₆H₁₁O)₂], contains a six‐coordinate tin centre as a consequence of intramolecular Sn—O interactions. The Sn—O bond lengths range between 2.428 (4) and 2.439 (4) Å.     

Dibenzo[b,f]oxepin‐10(11H)‐one and dibenzo[b,f]thiepin‐10(11H)‐one as useful synthons in the synthesis of various dibenzo[e,h]azulenes

The present review focuses on dibenzo[b,f]oxepin‐10(11H)‐one ( I , X = O) and dibenzo[b,f]thiepin‐10(11H)‐one ( I , X = S) as common synthons in the efficient synthesis of various dibenzoxepino[4,5‐ and dibenzothiepino[4,5]‐fused five‐membered heterocycles: [2,3] fused thiophene ( II ), [3,4] fused thiophene ( III ), furan ( IV ), pyrrole ( V ), imidazole ( VI ), pyrazole ( VII ), oxazole ( VIII ), and thiazole ( IX ). The potential of I to be converted into reactive intermediates that readily undergo heteroaromatic annulation reactions by cyclocondensation with proper binucleophiles allows formation of a range of enumerated functionalized dibenzo[e,h]azulene [4] structures ( II , III , IV , V , VI , VII , VIII , IX ). Dibenzo[e,h]azulenes as heterotetracyclic scaffold can be exploited in further modifications to obtain compounds with altered physicochemical and biological profile. J. Heterocyclic Chem., (2012).     

Bis(μ‐benzene‐1,2‐dicarboxylato)bis{aqua[2‐(2‐chloro‐6‐fluorophenyl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline]cadmium(II)} and its zinc(II) analogue

In the isomorphous title compounds, [Cd₂(C₈H₄O₄)₂(C₁₉H₁₀ClFN₄)₂(H₂O)₂] and [Zn₂(C₈H₄O₄)₂(C₁₉H₁₀ClFN₄)₂(H₂O)₂], the Cd^II centre is seven‐coordinated by two N atoms from one [2‐(2‐chloro‐6‐fluorophenyl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline (L) ligand, one water O atom and four carboxylate O atoms from two different benzene‐1,2‐dicarboxylate (1,2‐bdc) ligands in a distorted pentagonal–bipyramidal coordination, while the Zn^II centre is six‐coordinated by two N atoms from one L ligand, one water O atom and three carboxylate O atoms from two different 1,2‐bdc ligands in a distorted octahedral coordination. Each pair of adjacent metal centres is bridged by two 1,2‐bdc ligands to form a dimeric structure. In the dimer, each L ligand coordinates one metal centre. The dimer is centrosymmetric, with a crystallographic inversion centre midway between the two metal centres. The aromatic interactions lead the dimers to form a two‐dimensional supramolecular architecture. Finally, O—H...O and N—H...O hydrogen bonds reinforce the two‐dimensional structures of the two compounds.     

Ethyl[tris(3‐tert‐butyl‐5‐methylpyrazol‐1‐yl)hydridoborato]zinc(II)

The X‐ray crystal structure of the title compound, [Zn(C₂H₅)(C₂₄H₄₀BN₆)], or Tp^tBu,MeZnEt [Tp^tBu,Me is tris(3‐tert‐butyl‐5‐methylpyrazolyl)hydridoborate], reveals a distorted tetrahedral geometry around the Zn atom. The Zn center is coordinated by three N atoms of the borate ligand and by one C atom of the ethyl group. The present structure and other tetrahedral Tp zinc alkyl complexes are compared with similar Ttz ligands (Ttz is 1,2,4‐triazolylborate), but no major differences in the structures are noted, and it can be assumed that variation of the substitution pattern of Tp or Ttz ligands has little or no influence on the geometry of alkylzinc complexes. Refinement of the structure is complicated by a combination of metric pseudosymmetry and twinning. The metrics of the structure could also be represented in a double‐volume C‐centered orthorhombic unit cell, and the structure is twinned by one of the orthorhombic symmetry operators not present in the actual structure. The twinning lies on the borderline between pseudomerohedral and nonmerohedral. The data were refined as being nonmerohedrally twinned, pseudomerohedrally twinned and untwinned. None of the approaches yielded results that were unambiguously better than any of the others: the best fit between structural model and data was observed using the nonmerohedral approach which also yielded the best structure quality indicators, but the data set is less than 80% complete due to rejected data. The pseudomerohedral and the untwinned structures are complete, but relatively large residual electron densities that are not close to the metal center are found with values up to three times higher than in the nonmerohedral approach.     

Crystallographic report: Dichloro[bis(1‐methylimidazole‐2)disulfide]zinc(II)

The Zn center in [ZnCl₂(L‐S‐S‐L)], where L‐S‐S‐L = bis(1‐methylimidazole‐2)disulfide, adopts a tetrahedral configuration defined by two Cl atoms and two N atoms from L‐S‐S‐L, which was obtained by in situ oxidation of 1‐methylimidazole‐2‐thione. Copyright © 2005 John Wiley & Sons, Ltd.     

Spirane—II Spiro[dibenzo[f.h]-[1.5]-dioxacyclononan-3,1′-cyclopropan]

The title spiran has not been reported. The conformation of this spiran also been determined by NMR spectroscopy and X-ray crystallography. In this conformation the chiral spiran molecule has a twofold axis of symmetry.     

Diaquabis(quinoxaline‐2‐carboxylato‐κ2N1,O)copper(II)

In the title compound, [Cu(C₉H₅N₂O₂)₂(H₂O)₂], the Cu^II ion lies on an inversion centre and has an elongated centrosymmetric octahedral environment, equatorially trans‐coordinated by two N,O‐bidentate quinoxaline‐2‐carboxylate ligands and axially coordinated by two water O atoms. Symmetry‐related molecules are linked by strong O—H...O hydrogen bonds, involving the uncoordinated carboxyl O atom of the carboxylate group and the coordinated water molecules, to form a two‐dimensional network. Weak intermolecular C—H...N interactions also stabilize the crystal structure.     

Poly[aqua[μ4‐3,3′‐(diazenediyl)dibenzoato]zinc]

The solvothermal reaction of Zn(OAc)₂·2H₂O with 3,3′‐(diazenediyl)dibenzoic acid (H₂ADB) in H₂O at 393 K afforded the title complex, [Zn(C₁₄H₈N₂O₄)(H₂O)]_n. The asymmetric unit contains half a Zn^II cation, half an ADB ligand and half a water molecule. Each Zn^II centre lies on a crystallographic twofold rotation axis and is five‐coordinated by four O atoms of bridging carboxylate groups from four ADB ligands and one O atom from a water molecule, forming a distorted trigonal–bipyramidal coordination geometry. The [Zn(H₂O)] subunits are bridged by carboxylate groups to give one‐dimensional [Zn(μ‐COO)₄(H₂O)]_n chains. The chains are linked by ADB ligands into two‐dimensional sheets, and these sheets are further connected to neighbouring sheets via hydrogen bonds (OW—HW...O), forming a three‐dimensional hydrogen‐bond‐stabilized structure with an unprecedented 3⁷4¹⁷5²6² topology.     

Solid-substrate room-temperature phosphorescence study on zinc(II) and tin(IV) protoporphyrins and their interaction with DNA

The solid-substrate room-temperature phosphorescence (SS-RTP) of two commercially available metalloporphyrin compounds, zinc(II) protoporphyrin (ZnPP) and tin(IV) protoporphyrin (SnPP) has been studied. Strong and stable RTP signals of the two metalloporphyrins in neutral to weakly basic solutions can be simply induced on filter paper without addition of external heavy atom perturbers. Their emission bands appeared at 723 nm for ZnPP and 718 nm for SnPP at an excitation wavelength of 417 nm. Compared with SnPP, ZnPP is a better RTP probe for DNA because its RTP enhancement effect is much higher under the same experimental conditions. The interaction of ZnPP with DNA at pH 8.5 gives an apparent binding constant of 9.1 x 10(3) which is similar to that of the cationic porphyrin absorption probe CuTMPyP (copper (II)- tetrakis(4-N-methylpyridyl)porphine complex). Hydrogen bonding between the monocarboxylic acid substituent of ZnPP and the base pairs of DNA plays a crucial role in the binding.