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1.
The reaction of the dithioether ligand, 2,3-bis(5-methyl-1,3,4-thiadiazole-2-thiomethyl) quinoxaline (L) with AgBF4, leads to the formation of a novel complex {[AgL](BF4)} 1, which has been characterized by single-crystal X-ray diffraction analysis: monoclinic, space group C2/c, with a = 20.316(7) ?, b = 12.401(4) ?, c = 18.039(6) ?, β = 108.404(6)° and V = 4312(3) ?3. The crystal structure of the complex consists of 1D {[AgL]+} cation chain and BF4 anions. In 1, the coordination geometry of AgI center can be best described as trigonal planar coordinated by three N from two distinct L ligands. The ligand is polydentate with one end adopting a bidentate conformation to chelate an AgI atom and the other end monodentate to bridge another AgI resulting in an infinite chain along b axis. There exist Ag⋯N weak coordination, π–π stacking and F⋯S weak interactions in the complex, and these weak interactions link the 1D complex into 3D supramolecular structure and further stabilize the crystal structure in the solid state.  相似文献   

2.
Two new manganese(II)-1,10-phenanthroline-nitroprusside complexes, [Mn(phen)3][Fe (CN)5(NO)]⋯2H2O⋯0.25CH3OH (1) and [Mn(phen)2(H2O)2][Fe(CN)5(NO)]⋯H2O (2) (where phen is 1,10-phenanthroline) have been synthesized and characterized by X-ray diffraction, electronic paramagnetic resonance (E.P.R.) and IR analyses. Complex 1 crystallizes in the monoclinic space group P21/n, with lattice parameters a = 10.0441(15) Å, b = 19.668(2) Å, c = 19.938(3) Å,  β =100.427(14)°, V = 3873.7(10) Å3, Z = 4; complex (2) crystallizes in the monoclinic space group C2/c, with a = 17.120(2) Å, b = 13.7925(19) Å, c = 14.4362(17) Å, β = 107.962(12)°, V = 3242.6(7) Å3, Z = 4. In the two compounds, three phen ligands 1, or two phen ligands and two cis-related aqua molecules 2, are in a distorted octahedral arrangement around the Mn(II) ion. The nitroprusside anion, [Fe(CN)5(NO)]2−, acts as a counterion. It is intriguing that in complex 2 no cyano bridges are present with two water molecules coordinated to the Mn(II) ion considering that usually the cyano nitrogen atoms are strong donors and could readily replace the coordinating solvent water molecules. Abundant hydrogen bond interactions and π–π stacking between the phen rings in two complexes lead to three-dimensional supramolecular networks.  相似文献   

3.
The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C19H20O5, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 1 with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.  相似文献   

4.
The title compound, cis-[Rh(biq)2Cl2]Cl·3H2O (biq = 2,2′-biquinoline) crystallized in the monoclinic space group P2 1 /n with a = 11.231(2) Å, b = 20.895(4) Å, c = 14.081(3) Å, β = 94.76(3)°, V = 3293.0(11) Å3, D c = 1.565 g cm−3, μ = 0.806 mm−1, F(000) = 1576 and Z = 4. It contains a monomeric [Rh(biq)2Cl2]+ cation, a chloride ion and three molecules of H2O. The rhodium(III) ion is hexa coordinated forming a distorted octahedral arrangement. The mean Rh(III)–N distance for the four Rh(III)–N bonds is 2.0625 Å. The two chloride atoms are bonded in a cis configuration [Rh(III)–Cl bond distances are 2.329(3) and 2.341(4) Å]. The structure shows a curling stacks of cationic complexes interacting via offset-face-to-face (OFF) π–π aryl interaction motif. Water molecules and chloride ions are hydrogen bonded (H2O···H–OH and Cl···H–OH) and links the curling stacks by hydrogen bonding via Rh–Cl···H–OH interactions.  相似文献   

5.

Abstract  

The compounds methyl 3-(benzoylamino)-6-methyl-2-oxo-2H-pyran-5-carboxylate (1), C15H13NO5, and N-[5-(3,4-dimethoxyphenyl)-6-methyl-2-oxo-2H-pyran-3-yl]benzamide (2), C21H19NO5, crystallize as a centrosymmetric hydrogen-bonded dimer facilitated by N–H···O interactions involving the amide and carbonyl moiety of the lactone group of adjacent molecules. Supramolecular aggregation in 1 is controlled by a combination of π–π interactions [centroid–centroid distance = 4.0745(11) ?] and weak C–H···O hydrogen bonding between the phenyl ring of the benzoylamino group and the carbonyl atom of the methoxycarbonyl group and in 2 by a combination of π–π interactions [centroid–centroid distance = 4.0699(8) and 4.1556(10) ?], weak C–H···O interactions between the methoxy substituents of the adjacent dimethoxyphenyl group and weak C–H··· π interactions.  相似文献   

6.
The dinuclear copper(II) complex {[Cu(pmea)Cl][Cu(H2O)3Cl]}(Cl)·H2O (1) (pmea =bis(2-pyridylmethyl)amino-2-ethanoic acid) has been synthesized and characterized. It crystallizes in the monoclinic system P21/c, a = 9.0057(11), b = 28.031(3), c = 8.5669(10) Å, β = 104.267(2)°, V = 2095.9(4) Å3, Z = 4. Crystal structure of 1 reveals a syn-anti carboxylate-bridged dinuclear complex, in which the coordination environment around each copper atom exhibits a distorted square-pyramid. Magnetic susceptibility measurement for 1 exhibits a weak intermolecular antiferromagnetic exchange interaction with 2J = −1.17(9) cm−1. The cyclic voltammogram of 1 gives one oxidation and two reduction processes.  相似文献   

7.
Abstract  The Ni(II) complex, [Ni(H2biim)2(PABA)2]Cl2·2H2O, H2biim being 2,2′-biimidazole, PABA being 4-aminobenzoic acid has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P − 1 with unit cell parameters a = 8.3920(9) ?, b = 9.8436(11) ?, c = 9.8874(11) ?, α = 94.862(2)°, β = 109.142(2)°, γ = 90.992(2)°, V = 767.95(15) ?3 and Z = 1. The molecules of the complex in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure. Index Abstract  Synthesis and Crystal Structure of Nickel(II) Complex with 2,2′-Biimidazole and 4-Aminobenzoic Acid Yanping Li and Pin Yang* The molecules of the title complex [Ni(H2biim)2(PABA)2]Cl2·2H2O in the crystal assemble by way of N–H⋯Cl, O–H⋯Cl, O–H⋯O hydrogen bonds as well as π–π stacking interactions to provide a two-dimensional supramolecular structure.   相似文献   

8.
The substitution chemistry of the activated clusters Os3(CO)10(MeCN)2 (1) and Os3(CO)10(1,5-cod) (2) has been investigated with the bidentate ligand 1,2-bis(dimethylphosphino)ethane (dmpe). Both starting clusters react rapidly with dmpe at room temperature to give the corresponding substitution product Os3(CO)10(dmpe) (3), whose isomeric composition is shown to depend on the nature of the starting cluster. Whereas the bridged cluster 1,2-Os3(CO)10(dmpe) (3b) was formed almost exclusively upon reaction with Os3(CO)10(MeCN)2, a near statistical mixture of bridging (3b) and chelating (3c) isomers of Os3(CO)10(dmpe) was found in the reaction employing Os3(CO)10(1,5-cod). Both dmpe isomers have been characterized in solution by 3iP NMR spectroscopy and their solid-state structures established by X-ray crystallography. The bridged cluster 1,2-Os3(CO)10(dmpe) crystallizes in the monoclinic space group P21/n, a = 9.867(2) Å, b = 17.081(3) Å, c = 14.198(2) Å, β = 95.902(3)°, V = 2380.4(6) Å3, Z = 4, and d calc = 2.793 Mg/m3; R = 0.0435, R w = 0.0466 for 3519 reflections with I > 2σ(I). The chelated cluster 1,1-Os3(CO)10(dmpe) crystallizes in the orthorhombic space group C222(1), a = 8.329(3) Å, b = 19.028(6) Å, c = 15.008(5) Å, V = 2379(1) Å3, Z = 4, and d calc = 2.795 Mg/m3; R = 0.0390, R w = 0.0718 for 2360 reflections with I > 2σ(I).  相似文献   

9.

Abstract  

Three new polymeric frameworks, [Ni(bbbm)(L1)2] n (1), [Ni(bbbm)(L2)2] n (2), and {[Co(bbbm)(L3)]·H2O} n (3) (bbbm = 1,4-bis(N-benzimidazolyl) butane, HL1 = 4-bromobenzoic acid, HL2 = 3-methylbenzoic acid, and H2L3 = glutaric acid) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 features a one-dimensional (1D) linear chain structure bridged by bbbm ligands, which is further connected into a supramolecular double chain structure through intermolecular π–π stacking interactions. Complex 2 contains 1D zigzag chain, which is further arranged into a 2D supramolecular architecture by hydrogen bonding and π–π stacking interactions. In the structure of 3, there are infinite 1D zigzag Co(II)-bbbm chains linked together by L3 ligands to generate an undulated 2D (4,4) sheet, which is further connected by intermolecular π–π stacking interactions to form a 3D supramolecular network. Furthermore, thermal stability and luminescent property of 13 were investigated.  相似文献   

10.
The molecular and crystal structures of the title compound, C19H22N2O4S, were determined by single crystal X-ray diffraction technique. The title compound crystallizes in space group F d d 2, with a = 30.785(3) ?, b = 10.6455(9) ?, c = 11.0036(8) ?, Z = 8, D calc = 1.379(2) g cm−3, μ(Mo-Kα) = 0.207 mm−1, and its crystal system is orthorhombic. The structure was solved by direct methods and refined to a final R = 0.042 for 1530 reflections with I > 2σ (I). There is a half-independent molecule in the asymmetric unit. The title molecule has twofold rotational symmetry along with the C–S bond. Classically no hydrogen bond is found in the crystal structure. The crystal structure is stabilized by π–π stacking and edge to face (C–H…π-ring) interactions. To elucidate conformational features and steric hindrances of the title molecule, selected torsion angle is varied from −180° to +180° in every 10° and thus molecular energy profile is calculated by PM3 semi-empirical method.Supplementary materials CCDC 261789 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: $+$44 1223 336033.  相似文献   

11.
Reaction and crystallization of 1,2-bis(2,6-dicarboxypyridin-4-yl)ethyne with Co(II) produces crystals containing monomers of 4-(2,6-dicarboxypyridin-4-yl)ethynylpyridine-2,6-dicarboxylatotriaqua cobalt(II) monohydrate complex (1), [Co(C16H6N2O8)(H2O)3]·H2O, instead of a rigid 1-D metal–organic framework consisting of a linear coordination polymer. This complex crystallizes in the monoclinic space group C2/c with a=6.8028(9) ?, b=36.781(5) ?, c=7.5135(9) 2.474(2)° and Z=4. The complex sits on a symmetry axis such that the two halves of the molecule are related by two-fold rotation symmetry. The molecules form layers in which the molecules are joined by intermolecular O–H⋯O interactions involving hydrogen bonds between CO2H⋯CO2 , H2O⋯CO2 , H2O⋯CO2H and H2O⋯H2O groups.Supplementary material CCDC-289569 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data request/cif, by e-mailing data request@ccdc.cam.ac.uk or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 IEZ, UK; fax: +44(0)1223-336033.  相似文献   

12.

Abstract  

The molecule in 4-cyclopropyl-4,5-dihydro-1H-1,2,3-triazole (I) is disposed about a mirror plane with the triazole ring lying in the plane and being orthogonal to the cyclopropyl ring. Considerable delocalization of π-electron density within the triazole ring is indicated by the pattern of bond distances in (I). The molecule of methyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate (II) adopts a curved shape with the dihedral angle formed between the triazole and benzene rings being 63.23(8)°. By contrast to (I), localization of π-electron density within the triazole ring in (II) is indicated. Both (I), via N–H···N hydrogen bonding, and (II), via C–H···O and C–H···N interactions, associate in the solid state to form supramolecular chains. In (I), the chain is a zigzag with a flat topology, whereas in (II) the linear chain has a curved topology. Compound (I) crystallizes in the orthorhombic space group Pnma with a = 5.6470(2) ?, b = 7.3359(4) ?, c = 13.4404(7) ?, and Z = 4. Compound (II) crystallizes in the monoclinic space group P21/c with a = 12.1314(5) ?, b = 5.5951(2) ?, c = 16.4339(7) ?, β = 111.269(2)°, and Z = 4.  相似文献   

13.
An X-ray diffraction study of the scandium iodide complex with antipyrine [Sc(AP)6]I3 (AP is antipyrine, i.e., 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) (I), which is not isostructural to the analogous compounds of Y, La, and Eu (II), is performed. Crystals I are trigonal; a = 24.911 ? and c = 10.140 ?; Z = 3, space group P $ \bar 3 $ \bar 3 . Crystal I is built of [Sc(AP)6]3+ complex cations of two types and I anions. In both cations, the Sc atom is octahedrally coordinated by six O atoms of six AP ligands (Sc-O, 2.054–2.078 ?). Complexes I differ from II by the absence of π-π stacking interactions between AP molecules, resulting in a supramolecular cation. Complex cations I of both types form combined layers. All I anions are located in the interlayer space, being statistically disordered within a flat area limited by eight complex cations of Sc1 and Sc2.  相似文献   

14.

Abstract  

Two new 1,3,3-trimethyl-2-methylene-2,3-dyhidro-1H-indole derivatives, (E)-2,3-dihydro-2-(4-cyanophenylacylidene)-1,3,3-trimethyl-1H-indole, (I), and (E)-2,3-dihydro-2-(4-chlorophenylacylidene)-1,3,3-trimethyl-1H-indole, (II), have been synthesized and their crystal structure determined by single crystal X-ray diffraction. (I), C20H18N2O, crystallizes in a monoclinic space group, P21/c, with unit cell parameters a = 9.882 (3), b = 15.614(4), c = 11.181(3) ?, β = 106.691(4)°, Z = 4. (II), C19H18Cl N O, crystallizes in a monoclinic space group, P21/n, with unit cell parameters a = 14.6722(19), b = 7.2597(9), c = 16.304(2) ?, β = 111.249 (2)°, Z = 4. The molecules consist of a enaminoketone group formed by a Fischer base 1,3,3-trimethyl-2-methylene-2,3-dihydro-1H-indole bonded, at the exocyclic electron-rich β-carbon atom of the indole moiety, with the benzoyl chloride derivatives substituted at para-positions with cyano and chloro groups. The molecules adopt a s-cis conformation with respect to the C=O bond towards the C=C bond, and a E configuration about the latter indole exocyclic alkene C–C bond. Intermolecular arrangement of the crystals show, for (I) an antiparallel stacking mode favored by the formation of weak C–H···π interactions involving the phenyl ring attached to the carbonyl group and the phenyl of the indole fragment in a head-to-tail mode, whereas, (II) present an weak C–H···Hal interaction.  相似文献   

15.
Abstract  Two metal complexes of 1H-triazo-4,5-f-1,10-phenanthroline (HL), CoL(SO4)0.5 · 4H2O (1) and MnL 2 · 2H2O (2) have been synthesized on hydrothermal conditions and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. Complex 1 was further assembled into a three-dimensional (3D) supramolecular network through the hydrogen-bonding interactions and inter-molecular π···π stacking interaction, 2 further assembled into a two-dimensional (2D) layer structure. This result shows that hydrogen-bonding interactions and π···π stacking interaction play important roles in the formation of coordination networks, especially in the aspect of linking the multinuclear discrete subunits or low-dimensional entities into high-dimensional supramolecular frameworks. Index abstract  Two metal complexes of 1H-triazo-4,5-f-1,10-phenanthroline (HL), CoL(SO4)0.5 · 4H2O (1) and MnL2 · 2H2O (2) have been synthesized on hydrothermal conditions. Complex 1 was further assembled into a three-dimensional (3D) supramolecular network through the hydrogen-bonding interactions and inter-molecular π···π stacking interaction, 2 further assembled into a two-dimensional (2D) layer structure.   相似文献   

16.
Abstract  The reaction of the dithioether ligand, 2,3-bis(pyrimidine-2-thiomethyl)quinoxaline (L) with AgNO3, leads to the formation of a novel complex {[Ag5(L)2(NO3)4](NO3)(CHCl3)2}n 1, which has been characterized by single-crystal X-ray diffraction analysis: monoclinic, space group C2/c, with a = 34.741(7), b = 9.930(2), c = 17.004(4) ?, β = 106.497(6)° and V = 5625(2) ?3.Complex 1 consists of 2D {[Ag5(L)2(NO3)4]+}n cations, uncoordinated anions and CHCl3 solvent molecules. In 1, there exist three crystallographic independent AgI centers, which adopt different coordination geometries. There exist ππ stacking interactions in the complex and these weak interactions further stabilize the crystal structure in the solid state. The coordination feature of the ligand has been investigated by DFT calculations. Index Abstract  Synthesis and Structure of a Silver(I) Complex {[Ag5(L)2(NO3)4](NO3)(CHCl3)2}n [L = 2,3-bis(pyrimidine-2-thiomethyl)quinoxaline] Chao-Yan Zhang, Qian Gao, Ya-Bo Xie*, and Jian-Bo Feng The crystal structure of complex {[Ag5(L)2(NO3)4](NO3)(CHCl3)2}n (L = 2,3-bis(pyrimidine-2-thiomethyl)quinoxaline) consists of 2D {[Ag5(L)2(NO3)4]+}n cations, uncoordinated anions and CHCl3 solvent molecules. There exist three crystallographic independent AgI centers, which adopt different coordination geometries. The coordination feature of the ligand has been investigated by DFT calculations.   相似文献   

17.
The salt bis 4-benzyl piperidinium bis dihydrogenmonophosphate trihydrogenmonophosphate (bis 4-BPP bis DPT) is monoclinic with the following unit cell dimensions: a = 13.132(2) Å, b = 8.755(2) Å, c = 13.643(2) Å, β = 92.40(2)°, space group P21 with Z = 2. The structure was solved by the Patterson method and refined to final R value of 0.0430. The structure consists of infinite parallel two-dimensional planes built of mutually H2PO4 , H3PO4 tetrahedra and cations connected by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers.  相似文献   

18.
The title compound crystallizes in the monoclinic space group P21/c with unit cell parameters a = 15.6239(15) ?, b = 14.0537(14) ?, c = 5.8396(5) ?, β = 92.666(3)°, V = 1280.8 (2) ?3, and Z = 4. The final reliability index is 0.0538 for 2921 observed reflections. Two phenyl rings of the title molecule are not coplanar, with a dihedral angle of 46.3(0)°. The molecular planarity of this substituted chalcone is strongly affected by the 4′-bromo group. The crystal cohesion is accentuated by π···π, C–H···Br interactions and R3 1 (11) hydrogen bond.  相似文献   

19.

Abstract  

Three saccharinate salts (2-aminopyrimidine): (saccharin) (1), (4-phenylthiazol-2-amine): (saccharin) (2), and (2-methylquinoline): (saccharin) (3) were prepared and structurally characterized by X-ray crystallography. Salt 1 crystallizes in the monoclinic, space group P2(1)/c, with a = 7.1782(9) ?, b = 13.5105(16) ?, c = 12.2251(12) ?, β = 93.3410(10)°, V = 1183.6(2) ?3, Z = 4. Compound 2 crystallizes in the triclinic, space group P-1, with a = 7.4584(7) ?, b = 8.6930(9) ?, c = 12.9179(14) ?, α = 108.952(2)°, β = 91.7510(10)°, γ = 97.2280(10)°, V = 783.57(14) ?3, Z = 2. Compound 3 crystallizes in the monoclinic, space group P2(1)/c, with a = 7.781(8) ?, b = 19.4209(19) ?, c = 10.9719(12) ?, β = 107.7390(10)°, V = 1579.2(16) ?3, Z = 4. The different hydrogen bonding interaction modes of the saccharinate anions and the cations lead to 3D network structure, 3D staircase structure, and 3D ABAB layer structure for 1, 2, and 3 respectively. Despite variations in the cation shape on the aromatic N–heterocyclic compounds, there all existed strong intermolecular N–H⋯O(carbonyl) hydrogen bonds. In compounds 1, and 3 the N+–H⋯O interaction between the N+–H group of the cation and the C=O group of the saccharinate anion is the most important interaction in this family of salts. However, in 2, there was a N–H⋯O interaction between the amino proton and the C=O group of the saccharinate anion. At the next level, the aromatic C–H proton interacts with the sulfonyl O atom. There are also π–π interactions in compounds 12, there is CH3–π interaction in 3. Under these interactions the three compounds exhibit synthons I–III respectively. These interactions are responsible for the high-yielding supramolecular assembly of N-containing aromatic bases and the saccharinate into salts.  相似文献   

20.
Abstract  In the molecular structures of three new structurally related chalcone derivatives, namely (2E)-1-(2-hydroxyphenyl)-3-(6-methoxy-2-naphthyl)prop-2-en-1-one, C20H16O3, I, (2E)-1-(2-chloropyridin-4-yl)-3-(6-methoxy-2-naphthyl)prop-2-en-1-one, C19H14ClNO2, II, and (2E)-3-(6-methoxy-2-naphthyl)-1-pyridin-4-ylprop-2-en-1-one, III, C19H15NO2, the configuration of the keto group is syn with respect to the olefinic double bond. In all three structures the molecules pack with weak intermolecular C–H···O interactions utilizing both the methoxy and keto oxygen’s in I, the methoxy oxygen in II and the keto oxygen in III. These interactions link the molecules into chains diagonally along the (011) plane of the unit cell in I and III and along the (010) plane in II. The dihedral angle between the phenyl and 2-napthyl rings in I is 31.7(3)°. In II and III the dihedral angle between the pyridyl and 2-naphthyl rings is 14.4(9)° and 1.8(9)°, respectively. C–H···O hydrogen bonding interactions influence these twist angles of these rings in IIII while weak π–π stacking interactions between naphthyl rings in I and III and also between pyridyl and naphthyl rings in II help stabilize crystal packing. [I: P2 1 /c, a = 7.6635(4) ?, b = 11.8047(6) ?, c = 16.7584(7) ?, β = 99.271(5)°, V = 1496.25(13) ?3; II: Pbca, a = 14.1424(4) ?, b = 6.0957(2) ?, c = 33.1458(11) ?, V = 2857.43(16) ?3; III: P2 1 /c, a = 11.5155(4) ?, b = 6.0020(2) ?, c = 22.4645(8) ?, β = 103.002(4)°, V = 1512.85(9) ?3]. Index Abstract  Crystal structures from three Chalcones derived from 6-methoxy-2-naphthaldehyde are reported and their geometric and packing parameters described.  相似文献   

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