Synthesis and Crystal Structure of Heptyl 3-(3,4-dihydroxyphenyl)-2-propenoate

Abstract  The title compound, C₁₆H₂₂O₄, synthesized by modified Knoevenagel condensation of protocatechualdehyde with monoheptyl-malonate and recrystallized from benzene, was confirmed by single-crystal X-ray diffraction (CCDC 272827). The compound crystallizes in triclinic space group Pī with cell parameters a = 5.296(3) ?, b = 10.711(13) ?, c = 13.870(4) ?, α = 98.84(7)°, β = 90.97(4)°, γ = 96.77(7)° and Z = 2. The structure is the E isomer and its packing is stabilized by intermolecular O–H···O and C–H···O hydrogen bonds. Index Abstract  The title compound, C₁₆H₂₂O₄, synthesized by modified Knoevenagel condensation, was confirmed by single-crystal X-ray diffraction showing its structure is in E isomer and its packing is stabilized by hydrogen bonds.      

Crystal Structure of 1,7-Bis(4-chlorophenyl)-4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-3,5-dione

Abstract  The synthesis and crystal structure of 1,7-bis(4-chlorophenyl)-4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-3,5-dione is described. This compound is a curcuminoid analogue, configurationally symmetric about the C4–C5 atoms and also retains the two fold axis in the crystal phase. This compound crystallizes in the space group C2/c with unit cell parameters a = 19.203(1) ?, b = 13.147(1) ?, c = 8.801(1) ?, β = 112.99(1)°, with half a molecule in the asymmetric unit. The ketenedithioacetal functionality present between the carbonyl groups prevents the possibility of keto-enol tautomerization in this compound. The push-pull nature of the ketenedithioacetal functionality organizes the cinnamoyl groups parallel to each other. Index Abstract  The details regarding synthesis and crystal structure of the title compound which is a curcuminoid analogue is reported in this paper.      

Crystal Structure of Meso-tetrakis[4-(pentyloxy)phenyl]porphyrin

Abstract  The crystal structure of the title compound, C₆₄H₇₀N₄O₄, has been determined by single crystal X-ray diffraction methods. The title compound crystallizes in the monoclinic space group P2(1)/c with cell dimensions a = 13.8946(3) ?, b = 16.1069(3) ?, c = 12.1974(2) ?, β = 93.4050(10)°, Z = 2. The porphyrin core to be composed of four pyrrole rings linked through methane carbon bridges. Each molecule lies across a crystallographic inversion center. The porphyrin core is planar, which facilitates π-electron delocalization. The inner nitrogen H atoms are found localized on opposite pyrrole rings and these rings differ structurally from the other two pyrrole rings. The imino H atoms form bifurcated intramolecular hydrogen bonds with the adjacent unprotonated N atoms due to the contract porphyrin core. Graphical Abstract  The crystal structure of meso-tetrakis[4-(pentyloxy)phenyl]porphyrin is reported in this paper.      

Spectroscopic Studies and Crystal Structure of (<Emphasis Type="Italic">Z</Emphasis>)-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone

Abstract  The Schiff base (Z)-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone has been synthesized from the reaction of 2-aminophenol with 2-hydroxy-3-methoxybenzaldehyde. The title compound has been characterized by elemental analysis, FT-IR, ¹H-NMR, ¹³C-NMR and UV–Visible techniques. The structure of the title compound also was determined crystallographically. The crystal structure has been solved by direct methods and refined by full-matrix least squares. The title compound crystallize in the monoclinic space group P2₁/c with a = 10.438(1), b = 8.851(1), c = 12.746(1) ?, β = 95.72(1)°, V = 1171.7(2) ?³, D _x  = 1.379 g cm⁻³, respectively (R1 = 0.0522 and wR2 = 0.126 for 1442 reflections [I > 2σ(I)]). Index Abstract   N-salicylideneaniline derivatives have been shown to exist as tautomeric forms due to intramolecular proton shifts between the phenol-oxygen and the imine-nitrogen, via intramolecular hydrogen bonding O–H···N or O···H–N.      

Synthesis,Crystal Structure and Fluorescent Study of Bis(2-(2-hydroxyphenyl)benzimidazolate)zinc with Ethanol Solvate

Abstract  The zinc(II) complex with 2-(2-hydroxyphenyl)benzimidazole, namely [Zn(2-(2-hydroxyphenyl)benzimidazolate)₂]·C₂H₅OH (1 · C₂H₅OH) has been synthesized and characterized by X-ray crystallography and photoluminescent analysis. The complex crystallizes in monoclinic space group P2₁/c with cell parameters a = 10.156(1) ?, b = 25.771(3) ?, c = 9.674(1) ?, α = 90°, β = 103.641(2)°, γ = 90°, Z = 4, V = 2460.4(4) ?³. The central Zn(II) is four-coordinate and has a tetrahedral geometry. The steady-state and time-resolved photoluminescent spectra for the title compound have also been studied. The emission property can be ascribed to ligand-centered charge-transfer transition (LCCT) with π → π* property. Index Abstract   A new co-crystal of Zn(II) complex of 2-(2-hydroxylphenyl)benzimidazole with ethanol solvate has been prepared, characterized by X-ray crystallography and fluorescent studies.      

Crystallographic and Conformational Analysis of [(<Emphasis Type="Italic">E</Emphasis>)-2-[(3-Chlorophenylimino)methy])-4-methoxyphenol]

Abstract  The crystal structure of C₁₄H₁₂ClNO₂ was determined by X-ray analysis. It crystallizes in the triclinic space group Pc with a = 12.5346(10) ?, b = 4.5101(3) ?, c = 12.0534(11) ?, α = 90.00o, β = 113.669(6)o, γ = 90.00o, Z = 2, Dx = 1.393 mg/m³, μ (MoK_α) = 0.298 mm⁻¹. The title compound is photochromic and molecule is non-planar. It adopts a phenol–imine tautomeric form with a strong intramolecular O–H···N hydrogen bond and a strong intermolecular C–H···O hydrogen bond. Minimum energy conformations AM1 were calculated as a function of the three torsion angles θ1(C10–C9–N1–C8), θ2(C9–N1–C8–C1) and θ3(N1–C8–C1–C6), varied every 10°. As in the X-ray experiment results, molecule has an angle that makes it non-planar between two aromatic rings in AM1 optimized geometry. Graphical Abstract  Molecular and crystal structure of [(E)-2-[(3-chlorophenylimino)methy])-4-methoxyphenol], C₁₄H₁₂ClNO₂, have been determined by single crystal X-ray diffraction study, and conformational analysis of the title molecule with respect to the selected torsion angle has been achieved by AM1 semi-empirical calculations.      

Structures of Bis(1-ethylbenzimidazol-2-yl)alkyl Copper(II) Dichlorides: An Unusual Cocrystallization

Abstract  Two structures containing pseudo-tetrahedral Cu(II)N₂Cl₂ coordination complexes are reported. The first molecular structure (A) of the compound, 1,1′bis(1-ethylbenzimidazol-2-yl)propane copper(II) dichloride (triEtBBIM)Cu(II)Cl₂, 1, is reported. The complex crystallized in the triclinic space group P-1 with a = 8.616(3) ?, b = 9.302(3) ?, c = 14.314(4) ?, α = 85.613(6)°, β = 85.170(6)°, γ = 66.117(6)° and V = 1044.1(5) ?³ with Z = 2. The second structure (B) contains 1 and (3,3′bis(1-ethylbenzimidazol-2-yl)pentane) copper(II) dichloride (tetEtBBIM)Cu(II)Cl₂, 2, both of which, cocrystallize in an equal molar ratio with a nitromethane solvate molecule. The complex crystallized in the monoclinic space group P2₁/c with a = 18.876(4) ?, b = 14.975(3) ?, c = 18.344(4) ?, β = 116.75(3)°, and V = 4630.3(16) ?³ with Z = 4. The cocrystallization of such discrete complexes has been coined a chemical Janus. Graphical Abstract  The title complexes contain pseudo-tetrahedral Cu(II)N₂Cl₂ coordination. One of the structures is the result of an unusual cocrystallization, in which two different discrete Cu(II) molecules cocrystallize in an equimolar ratio with a nitromethane solvate molecule.      

Synthesis and Crystal Structure Studies of Novel Bioactive Heterocycle: 7-Chloro-5-Cyclopropyl-9-Methyl-10-(2-Piperidin-1-yl-Ethyl)-5,10-Dihydro-4,5,6,10-Tetraaza-Dibenzo[a,d] Cyclohepten-11-One

Abstract  The compound, 7-chloro-5-cyclopropyl-9-methyl-10-(2-piperidin-1-yl-ethyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo[a, d] cyclohepten-11-one, C₂₂H₂₆N₅ClO, crystallizes in the triclinic space group Pī with cell parameters a = 8.918(7) ?, b = 9.297(7) ?, c = 14.184(8) ?, V = 1095.98(1) ?³ and Z = 2. The final residual factor R ₁ = 0.0451. The structure exhibits intermolecular hydrogen bonds. The 2-piperidin-1-yl-ethyl ring adopts a chair conformation. The starting material used to synthesize the title compound is the intermediate compound of well known anti-HIV drug Nevirapine hence the title compound is having biological importance and hence this crystal structure will helps to structural characterization of the molecule and also for the molecular modeling it will helps for biological study. Graphical Abstract  The title compound 7-chloro-5-cyclopropyl-9-methyl-10-(2-piperidin-1-yl-ethyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo[a, d] cyclohepten-11-one was synthesized by condensation of 7-chloro-5-cyclopropyl-9-methyl-5,10-dihydro-4,5,6,10-tetraaza-dibenzo[a, d] cyclohepten-11-one with 1-(2-chloro-ethyl)-piperidine hydrochloride in presence of anhydrous powdered potassium carbonate as base using N,N-dimethyl formamide as solvent and its crystal structure determined. The title compound derived from bioactive molecule and it is also having biological importance hence this crystal structure will helps for the structural characterization and the biological study of the novel molecule.      

1,3-Bis(4-Pyridinylcarbonyl)-2-Imidazolidinethione and Its First Cluster Complex: Synthesis,Crystal Structure and Luminescence Properties

Abstract  The first cluster complex of 1,3-bis(4-pyridinylcarbonyl)-2-imidazolidinethione (4-bpit) with CuI was prepared and characterized. Single crystal X-ray diffraction analysis established that the compound crystallizes in the monoclinic system, space group C2/m, with a = 15.601(3), b = 12.438(3), c = 12.570(3)?, β = 110.02(3), Z = 4, V = 2291.8(8)?³. This compound is also a coordination polymer with one-dimensional double-ribbon structure containing the adaptable rhomboid Cu₂I₂ cluster unit. The solution-state luminescence spectra showed that the high-energy emission may be associated with a ligand-to-ligand charge-transfer excited state. Graphical Abstract  The first cluster complex of 1,3-bis(4-pyridinylcarbonyl)-2-imidazolidinethione (4-bpit) with CuI was prepared and characterized. This compound is also a coordination polymer with one-dimensional double-ribbon structure containing the adaptable rhomboid Cu₂I₂ cluster unit. The solution-state luminescence spectra showed that the high-energy emission may be associated with a ligand-to-ligand charge-transfer excited state.     

Crystal Structure of 4,7-Dichloro-1,2,3,5,6,8-hexakis-(4-methoxy-phenylsulfanyl)-acenaphthylene

Abstract  The title compound was prepared from the reaction of perchloroacenaphthylene with an excess of sodium salt of 4-methyloxythiophenol in toluene/ethanol (1:1) solvent and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the Monoclinic space group P2(1) with the parameters: a = 10.351(1) ?, b = 20.453(3) ?, c = 12.1837(16) ?, β = 105.584(3)°, V = 2484.5(6) ?³, with Z = 2 formula units. Graphical Abstract   The title compound 4,7-dichloro-1,2,3,5,6,8-hexakis-(4-methoxy-phenylsulfanyl)-acenaphthylene was synthesized from perchloroacenaphthylene C ₁₂ Cl ₈ with an excess of 4-methoxybenzene thiolate in toluene/ethanol (1:1) .     

The Structure and Characterization of [1,11-Bis(2-Hydroxybenzyl)-1,4,8,11-Tetraazaundecane]Iron(III) Perchlorate

Abstract  The structure of an Fe(III) complex of reduced Schiff base is reported. The title compound, C₂₁H₃₀ClFeN₄O₆ (I), crystallizes in the monoclinic space group P2₁/n with cell constants: a = 9.988(2) ?, b = 20.430(5) ?, c = 11.415(3) ?, β = 105.480(4)°. It contains a six-coordinate FeN₄O₂ cation where the ligand is a reduced Schiff base resulting from the NaBH₄ reduction of the condensation product between salicylaldehyde and 1,4,8,11-tetraazaundecane. Due to the increased flexibility of the saturated backbone of the ligand compared to the Schiff base from which it was synthesized, the complex adopts a trans-FeN₄O₂ conformation. There is extensive hydrogen bonding between the amine H atoms and the anion O atoms. Index Abstract  The structure of an Fe(III) complex of reduced Schiff base is reported which adopts a trans-FeN₄O₂ conformation where the ligand is a reduced hexadentate Schiff base resulting from the NaBH₄ reduction of the condensation product between salicylaldehyde and 1,4,8,11-tetraazaundecane.      

New Toluene Hemi Solvate of the Proton Pump Inhibitor Piperazinium Esomeprazolate

Abstract  The new toluene hemisolvate of the piperazinium salt of esomeprazole, ((S)-5-methoxy-2-[(4-methoxy-3,5-dimethyl-pyridin-2-yl)methylsulfinyl]-3H-benzimidazole, C₁₇H₁₉N₃O₃S) has the composition piperazinium esomeprazolate 0.5 toluene. The unit cell has monoclinic P2₁ symmetry with the cell parameters a = 10.0903(16) ?, b = 16.234(3) ?, c = 15.316(2) ?, β = 92.746(12)°, V = 2,506.0(7) ?³. It contains four piperazinium, four esomeprazolate and two toluene molecules. The crystal structure exhibits intermolecular hydrogens bonds within the layers and Van der Waals contacts between the layers. Additionally, three new crystal phases of solvent-free piperazinium esomeprazolate were found. Index Abstract  The title compound is a toluene hemisolvate of the piperazinium salt of esomeprazole, ((S)-5-methoxy-2-[(4-methoxy-3,5-dimethyl-pyridin-2-yl)methylsulfinyl]-3H-benzimidazole. Single crystal X-ray diffraction analysis reveals that the molecules crystallize in layers. In a layer the molecules are held together by classical hydrogen bonds whereas the layers on the other hand are connected by vdW contacts.      

Crystal Structure of bis(18-Crown-6)-bis(formato-O) dicaesium dihydrate

Abstract  The crystal structure of the title compound, [2Cs⁺(C₁₂H₂₄O₆)₂(CHO₂ ⁻)₂(H₂O)₂], was determined by an X-ray diffraction analysis. The compound crystallizes in the monoclinic space group P2₁ /n with cell parameters a = 10.4278(7) ?, b = 10.0183(5) ?, c = 18.2383(12) ?, β = 93.723(5)°, V = 1910.3(2) ?³ and Z = 2. The Cs cations are bonded to each of the six O atoms of a crown ether ring, two water molecules, and one O atom of a formato anion. As a result of that, a centrosymmetric dimeric dinuclear complex is formed. The two halves of the dimer are connected by a ring of formato anions and water molecules which are linked by O–H···O hydrogen bonds. Index Abstract  The title compound, bis(18-crown-6)-bis(formato-O), caesium dihydrate, features a centrosymmetric dimeric dinuclear complex where two Cs cations are coordinated by six O atoms of a crown ether ring. The two halves of this complex are held together by a ring of formato anions and water molecules which are linked by hydrogen bonds.      

The Synthesis and Crystal Structure of New Bis(3-chlorophenyl)-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-methanol

Abstract  The title compound bis(3-chlorophenyl)-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-methanol 8 has been synthesized and established by H NMR, IR and MS spectra and X-ray diffraction crystallography. Compound 8, C₂₃H₂₉Cl₂N₃O, Mr = 424.31, crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 14.5402(6) ?, b = 12.5888(5) ?, c = 11.6510(5) ?, α = 90o, β = 100.183o(2), γ = 90o, V = 2099.05(15) ?³, D_x = 1.343 mg m⁻³ and Z = 4. The final R was 0.0514. The molecular conformation and packing is stabilized by interactions of intermolecular O1–H1···N3′. Index Abstract  The structure of bis(3-chlorophenyl)-[5-methyl-1-(4-methylphenyl)-1,2,3-triazol-4-yl]-methanol by the reaction of compound 4 and Grignard regent is studied.      

Synthesis,Characterization and Crystal Structure of Iridium(III)bis(2-<Emphasis Type="Italic">p</Emphasis>-tolyl-benzothiazolato-N,C<Superscript>2</Superscript>)(acetylacetonate)

Abstract  A novel thiazole-based iridium (III) complex (iridium(III)bis(2-p-tolyl-benzothiazolato-N,C²)(acetylacetonate)) has been prepared and fully characterized by EA, IR, ¹H-NMR and MS. The molecular structure of the complex has been determined by single crystal X-ray diffraction analysis. The iridium (III) center adopts a distorted octahedral geometry with cis-O–O, cis-C–C, and trans-N–N chelate disposition. The complex crystallizes in the orthorhombic Pbca space group with cell parameters a = 10.1388(7) ?, b = 18.3565(12) ?, c = 31.021(2) ?, α = β = γ = 90 ° and Z = 8. The electronic absorption and emission spectra of this complex have been investigated. Index Abstract  A novel thiazole-based phosphorescent iridium (III) complex (iridium(III) bis (2-p-tolyl-benzothiazolato-N,C²)(acetylacetonate)) has been prepared and fully characterized by EA, IR, ¹H-NMR, MS and X-ray diffraction analysis.     

3-Methyl-3a,4-Dihydro-3H-Thiochromeno[4,3-c]isoxazol

Abstract  The crystal structure of the title compound, C₁₁H₁₁NOS, was determined by an X-ray diffraction analysis. The compound crystallizes in the monoclinic space group P2₁/c with cell parameters a = 10.533(2) ?, b = 12.7826(19) ?, c = 7.6491(17) ?, β = 107.997(17)^°, V = 979.5(3) ?³ and Z = 4. The S containing heterocycle adopts a sofa conformation, whereas the 5-membered ring adopts an envelope conformation. The crystal packing is characterized by weak C–H···N contacts and π-stacking interactions. Graphical Abstract  The title compound, 3-methyl-3a,4-dihydro-3H-thiochromeno[4,3-c]isoxazol was synthesized by an 1,3 dipolar cycloaddition reaction and its crystal structure determined. Single crystal X-ray diffraction analysis reveals that the aromatic 6-membered ring is planar, whereas the ring containing the S atom adopts a sofa conformation and the 5-membered ring an envelope conformation. The methyl group is in an equatorial position.      

Synthesis and Crystal Structure of a Novel Mixed Ligand Cadmium(II) Complex of Benz-1,3-Thiazoline-2-Thione and 1,10-Phenanthroline

Abstract  A novel cadmium complex [Cd(C₇H₄NS₂)₂(phen)] was synthesized by the reaction of a polymeric complex, [Cd(C₇H₄NS₂)₂] _n , with 1,10-phenanthroline (phen) as a ligand. The crystal structure was determined by single-crystal X-ray diffraction. The crystallographic data are: triclinic , a = 8.3670(6) ?, b = 10.9898(8) ?, c = 17.1404(13) ?, α = 95.567(2)o, β = 95.881(2)o, γ = 109.034(1)o, V = 1471.26(19) ?³ and Z = 2. The final R value is 0.0375 for 7154 reflections. The compound [Cd(C₇H₄NS₂)₂(phen)] is monomeric revealing a coordination sphere of N₄S₂ type. The Cd atom is surrounded by two thiazole N atoms, two exocyclic S atoms from two bidentate 1,3-benzothiazole-2-thiolate anions and two 1,10-phenanthroline N atoms. The Cd cation is six-coordinate with a distorted octahedral geometry. Graphical Abstract  The synthesis and crystal structure of a novel monomeric complex ‘[Cd(C₇H₄NS₂)₂(phen)]’ obtained by the reaction of polymeric complex, [Cd(C₇H₄NS₂)₂] _n , with 1,10-phenanthroline is reported.      

Crystallographic and Conformational Analysis of [(Z)-2-ethoxy-6-[(2-hydroxyphenylamino)methylene]cyclohexa-2,4-dienone]

Abstract  The single crystal X-ray diffraction analysis of the title compound, C₁₅H₁₅NO₃, shows that the structure is adopted to its NH tautomeric form and crystallizes in the orthorhombic space group P bcn with a = 21.2424(15) ?, b = 12.7696(9) ?, c = 9.3605(10) ?, Z = 8, V = 2539.1(4) ?³, D _c  = 1.346 g/cm³. The molecular conformation in the crystal is stabilized by an intramolecular H-bond and the crystal structure is stabilized by the bifurcated O–H···O type intermolecular H-bonds. In order to understand the effects on conformational flexibility of the title molecule, molecular energy profile was calculated as a function of the selected torsion angle by means of AM1 semi-empirical method. Index Abstract  Molecular and crystal structure of [(Z)-2-ethoxy-6-[(2-hydroxyphenylamino)methylene]cyclohexa-2,4-dienone], C₁₅H₁₅NO₃, have been determined by single crystal X-ray diffraction study, and conformational analysis of the title molecule with respect to the selected torsion angle has been achieved by AM1 semi-empirical calculations.      

Crystal and Molecular Structure of the 1:2 Salt Formed Between 1,2-(4-Pyridyl)Ethane and 2-(4-Hydroxyphenylazo)Benzoic Acid

Abstract  Proton transfer occurred during co-crystallization of 1,2-(4-pyridyl)ethane with 2-(4-hydroxyphenylazo)benzoic acid to yield a salt comprising a 1:2 ratio of 1,2-bis(4-pyridinium)ethane dications and 2-(4-hydroxyphenylazo)benzoate anions. Centrosymmetrically related anions associate by charge-assisted O–H···O hydrogen bonds to form 24-membered {···OC₃N₂C₄OH}₂ synthons. These are connected into a supramolecular polymer via charge-assisted N–H···O hydrogen bonds involving the 1,2-bis(4-pyridinium)ethane dications. The compound crystallizes in the triclinic space group P−1 with a = 8.517(4) ?, b = 9.110(5) ?, c = 10.477(5) ?, α = 96.850(13)°, β = 94.446(12)°, γ = 104.946(10)° and Z = 1 {two anions and a dication}. Index Abstract  Supramolecular chains mediated by charge-assisted O–H···O and N–H···O hydrogen bonding are found in the salt containing a 1:2 ratio of 1,2-bis(4-pyridinium)ethane dications and 2-(4-hydroxyphenylazo)benzoate anions.      

Crystal Structure of 2-{1-[(1-(2-Pyridinio)ethylidene)hydrazono]ethyl}pyridinium diperchlorate,the Product of Template Condensation in the Presence of Cr(III)

Abstract  In an attempt to synthesize a Cr(III) complex of 2′-[1-(2-pyridinyl)ethylidene]oxamohydrazide an azine product 2-{1-[(1-(2-pyridinio)ethylidene)hydrazono]ethyl}pyridinium diperchlorate was obtained by an electrophilic acyl substitution catalyzed by Cr(III). Its structure was determined by X-ray crystal analysis and showed significant changes in comparison to the corresponding unprotonated compound. The 2-{1-[(1-(2-pyridinio)ethylidene)hydrazono]ethyl}pyridinium diperchlorate crystallizes in the space group P2₁/n of the monoclinic crystal system with unit cell parameters a = 14.3809(3) ?, b = 24.1516(5) ?, c = 15.4471(3) ?, β = 99.930(2)°, V = 5284.74(19) ?³ and Z = 12, i.e. three molecules per asymmetric unit. Graphical Abstract  In the template condensation of the 2′-[1-(2-pyridinyl)ethylidene]oxamohydrazide in presence of the chromium(III) ion the 2-{1-[(1-(2-pyridinio)ethylidene)hydrazono]ethyl}pyridinium diperchlorate was obtained and characterized by NMR spectroscopy and X-ray crystallography. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.