Chiral self-assembly of enantiomerically pure (4S,7R)-campho[2,3-c]pyrazole in the solid state: a vibrational circular dichroism (VCD) and computational study

NH-Indazoles in solid phase usually form NH⋯N hydrogen bonds between positions 1 and 2, which determine the secondary structure, forming dimers, trimers, or catemers (chains). Thus, the difficulty of the experimental analysis of the structure of the family of 1H-indazoles is clear. We have outlined a complete strategy by using different techniques of vibrational spectroscopy that are sensitive (VCD) and not sensitive (IR, FarIR, and Raman) to the chirality together with quantum chemical calculations. We have studied the chiral structure of (4S,7R)-campho[2,3-c]pyrazole both in solution (CCl₄) and in the solid phase (crystal). This compound crystallizes as a chiral trimer (LABHEB), with the monomer also being chiral. Herein, Far-IR, IR, and Raman spectra in solution and in the solid state are assigned using the support of B3LYP/6-31G(d) and B97D/6-31+G(d,p) calculations of (4S,7R)-campho[2,3-c]pyrazole monomers, dimers, and trimers, these last cyclamers being partially and fully optimized. Later, analysis of the vibrational circular dichroism (VCD) spectra allowed us to determine the chiral self-assembly of (4S,7R)-campho[2,3-c]pyrazole crystals (LABHEB). In the crystal, only the trimers are present while in solution, the monomer predominates. We have highlighted the importance of the analysis of the low frequency region (700–25 cm⁻¹) in the FT-Raman and Far-IR spectra, because it provides relevant information in order to confirm the presence of the trimers in the solid phase.     

cis-trans photoisomerization in [Ru(DIP)2(MeOH)2][OTf]2: synthesis, NMR, X-ray structure of the trans-isomer and photophysical properties

The first trans-ruthenium complex trans-[Ru(DIP)2(MeOH)2][OTf]2 (1b, where DIP = 4,7-diphenyl-1,10-phenanthroline) incorporating a pi-extended ligand was prepared via two methods: either photolysis of cis-[Ru(DIP)2(OTf)2] in MeOH-Et(2)O or via crystallization from MeOH-Et(2)O in direct sunlight. The X-ray molecular structure of is reported and confirmed the trans geometry of the title compound. The cis-trans isomerization process was monitored by 1H-NMR and showed that 1b reverts back to cis-[Ru(DIP)2(MeOH)2][OTf]2 (1a) in methanol-d4 after 15 h at 55 degrees C or several days at room temperature. The absorption spectra recorded in MeOH showed a bathochromic shift of the MLCT band of the trans-isomer 1b relative to that of the cis complex 1a. Interestingly at 77 K the emission spectrum of 1b is red shifted compared to the cis analog 1a. A rational explanation in terms of the energy of the excited states in the cis- and trans-isomers is proposed to explain this behavior.     

Chiral molecular magnets: synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = Mn(II), Fe(II), Co(II), Ni(II); L-tart = (2R,3R)-(+)-tartrate)

A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K, the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show antiferromagnetic interactions between spin carriers, but do not order above 2 K.     

Trialkyltetrathiafulvalene-sigma-tetracyanoanthraquinodimethane [R(3)TTF-sigma-TCNAQ] diads: synthesis, intramolecular charge-transfer properties, and X-ray crystal structure.

We report the use of the electron-donating 4,5-dipentyl-4'-methyl-TTF (TTF = tetrathiafulvalene) moiety in combination with the electron acceptor 11,11,12,12-tetracyanoanthraquinodimethane (TCNAQ) unit in the novel D-sigma-A diad molecules 11, 17, and 18. These compounds display a weak, broad, low-energy intramolecular charge-transfer (ICT) band in the UV-vis spectra (lambda(max) 430-450 nm). Cyclic voltammetric studies show two reversible one-electron oxidation processes for the R(3)TTF moiety, and a reversible two-electron reduction process for the TCNAQ moiety. The electron affinity of TCNAQ is significantly enhanced by the electron-withdrawing sulfonamide and sulfonic ester groups (compounds 17 and 18, respectively). Simultaneous electrochemistry and EPR (SEEPR) experiments show no significant intramolecular interaction between the R(3)TTF and TCNAQ moieties in compounds 11 and 18. X-ray crystallographic data are presented for 5, 11, and 20. The structure of 5 reveals hydrogen-bonded dimers. In molecule 11 the bond lengths and conformations of both donor and acceptor moieties are typical for neutral species. Compound 20 is an unusual calcium complex of TCNAQ derivative obtained by dicyanomethylation of anthraquinone-2-carboxylic acid.     

A controlled NO-releasing compound: synthesis,molecular structure,spectroscopy, electrochemistry,and chemical reactivity of R,R,S,S-trans-[RuCl(NO)(cyclam)]2+(1,4,8,11-tetraazacyclotetradecane)

The synthesis of trans-[RuCl(NO)(cyclam)]2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) can be accomplished by either the addition of cyclam to K2[RuCl5NO] or by the addition of NO to trans-[RuCl(CF3SO3)(cyclam)](CF3-SO3). Crystals of trans-[RuCl(NO)(cyclam)](ClO4)2 form in the monoclinic space group P2(1)/c, with unit cell parameters of a = 7.66500(2) A, b = 24.7244(1) A, c = 16.2871(2) A, beta = 95.2550(10) degrees, and Z = 4. One of the two independent molecules in the unit cell lies disordered on a center of symmetry. For the ion in the general position, the Ru-N and N-O bond distances and the [Ru-N-O]3+ bond angle are 1.747(4) A, 1.128(5) A, 178.0(4) degrees, respectively. In both ions, cyclam adopts the (R,R,S,S) configuration, which is also consistent with 2D COSY 1H NMR studies in aqueous solution. Reduction (E degree = -0.1 V) results in the rapid loss of Cl- by first-order kinetics with k = 1.5 s-1 and the slower loss of NO (k = 6.10 x 10(-4) s-1, delta H++ = 15.3 kcal mol-1, delta S++ = -21.8 cal mol-1 K-1). The slow release of NO following reduction causes trans-[RuCl(NO)(cyclam)]2+ to be a promising controlled-release NO prodrug for vasodilation and other purposes. Unlike the related complex trans-[Ru(NO)(NH3)4(P(OEt)3)](PF6)2, trans-[RuCl(NO)(cyclam)]Cl2 is inactive in modulating evoked potentials recorded from mice hippocampal slices probably because of the slower dissociation of NO following reduction.     

Synthesis,Characterization,X-ray Crystal Structure and Safener Activity of Chiral 2-(3-Methyl-2,3-dihydrobenzo[b][1,4]oxazin-4-yl)-2-oxoethyl Acetate

The new title compound, chiral 2-(3-methyl-2,3-dihydrobenzo[b][1,4]oxazin-4-yl)-2-oxoethyl acetate, has been synthesized via reduction, cyclization and acylation reaction. The structure of the product has been confirmed by IR, 1H NMR, 13 C NMR, LC-MS(ESI) and single-crystal X-ray diffraction.(R)-2-(3-methyl-2,3-dihydrobenzo[b][1,4]oxazin-4-yl)-2-oxoethyl acetate crystallizes in monoclinic, space group P21/c with a = 11.867(2), b = 8.4087(2), c = 14.325(6) ?, β = 117.59(2)o, Z = 4, V = 1266.9(6) ?3, Dc = 1.307 g/cm3, F(000) = 528, μ(MoK α) = 0.097 mm-1, R = 0.0453 and w R = 0.1237;(S)-2-(3-methyl-2,3-dihydrobenzo[b][1,4]oxazin-4-yl)-2-oxoethyl acetate belongs to the triclinic system, space group P1 with a = 8.2647(17), b = 8.7034(17), c = 9.5479(19) ?, α = 105.33(3), β = 100.95(3), γ = 105.14(3)o, Z = 2, V = 614.1(2) ?~3, Dc = 1.348 g/cm3, F(000) = 264, μ(MoK α) = 0.10 mm-1, R = 0.0613 and w R = 0.1037. Both of the molecules prefer to form crystal packing through C–H···O hydrogen bonds.     

Tetrachloro- and tetrabromoarsonium(V) cations: raman and 75As, 19F NMR spectroscopic characterization and X-ray crystal structures of [AsCl4][As(OTeF5)6] and [AsBr4][AsF(OTeF5)5]

The salts [AsX4][As(OTeF5)6] and [AsBr4][AsF(OTeF5)5] (X = Cl, Br) have been prepared by oxidation of AsX3 with XOTeF5 in the presence of the OTeF5 acceptors As(OTeF5)5 and AsF(OTeF5)4. The mixed salts [AsCl4][Sb(OTeF5)6-nCl(n-2)] and [AsCl4][Sb(OTeF5)6-nCl(n)] (n > or = 2) have also been prepared. The AsBr4+ cation has been fully structurally characterized for the first time in SO2ClF solution by 75As NMR spectroscopy and in the solid state by a single-crystal X-ray diffraction study of [AsBr4][AsF(OTeFs)5]: P1, a = 9.778(4) A, b = 17.731(7) A, c = 18.870(8) A, alpha = 103.53(4)degrees, beta = 103.53(4) degrees, gamma = 105.10(4) degrees, V = 2915(2) A3, Z = 4, and R1 = 0.0368 at -183 degrees C. The crystal structure determination and solution 75As NMR study of the related [AsCl4][As(OTeF5)6] salt have also been carried out: [AsCl4][As(OTeF5)6], R3, a = 9.8741(14) A, c = 55.301(11) A, V= 4669(1) A3, Z = 6, and R1 = 0.0438 at -123 degrees C; and R3, a = 19.688(3) A, c = 55.264(11) A, V= 18552(5) A3, Z = 24, and R1 = 0.1341 at -183 degrees C. The crystal structure of the As(OTeF5)6- salt reveals weaker interactions between the anion and cation than in the previously known AsF6- salt. The AsF(OTeF5)5- anion is reported for the first time and is also weakly coordinating with respect to the AsBr4+ cation. Both cations are undistorted tetrahedra with bond lengths of 2.041(5)-2.056(3) A for AsCl4+ and 2.225(2)-2.236(2) A for AsBr4+. The Raman spectra are consistent with undistorted AsX4+ tetrahedra and have been assigned under Td point symmetry. The 35Cl/37Cl isotope shifts have been observed and assigned for AsCl4+, and the geometrical parameters and vibrational frequencies of all known and presently unknown PnX4+ (Pn = P, As, Sb, Bi; X = F, Cl, Br, I) cations have been calculated using density functional theory methods.     

Determination of molecular structure using vibrational circular dichroism spectroscopy: the keto-lactone product of Baeyer-Villiger oxidation of (+)-(1R,5S)-bicyclo[3.3.1]nonane-2,7-dione

[reaction: see text] The Baeyer-Villiger oxidation of (+)-(1R,5S)-bicyclo[3.3.1]nonane-2,7-dione, 1, can lead to four keto-lactone products, 2a-d. A single isomer is obtained experimentally. We have used IR and VCD spectroscopies to identify the structure of this product. DFT calculations of the IR and VCD spectra of 2a-d show unambiguously that the experimental product is (+)-(1R,6R)-2a, and not the expected product 2b. NMR studies, including comparison of DFT and experimental 1H and 13C spectra, support this conclusion. This work provides the first example of the use of VCD spectroscopy to discriminate between structural isomers of a chiral molecule. The specific rotation of (+)-(1R,6R)-2a, predicted using TDDFT methods, is negative demonstrating that absolute configurations determined from TDDFT calculations of specific rotations are not 100% reliable.     

X-ray structure and circular dichroism of pure rotamers of bis[guanosine-5'-monophosphate(-1)](N,N,N',N'-tetramethylcyclohexyl-1,2-diamine)platinum(II) complexes that have R,R and S,S configurations at the asymmetric diamine

The use of a sterically hindered diamine ligand (Me(4)DACH) has allowed for the first time, the isolation and characterization, both in the solid state (X-ray crystallography) and in solution (circular dichroism), of pure DeltaHT rotamers of [Pt(Me(4)dach)(5'-GMP)(2)] (compounds 1 and 2 for R,R and S,S configurations of the Me(4)DACH ligand, respectively). Comparison of the CD spectra obtained for each rotamer, which differ only in the chirality of the Me(4)DACH ligand (R,R or S,S) or in the chirality of the HT conformation (Delta or Lambda), allowed us to conclude that, in the 200-350 nm range, the contributions to the overall CD spectrum that stem from diamine chirality and diamine-induced chirality of platinum d--d transitions or from sugar chirality are negligible relative to the exciton chiral coupling that occurs for pi-pi* transitions of the cis guanines. Accurate molecular structures of 1.10 D(2)O and 2.14 D(2)O (conventional crystallographic agreement indexes R(1) convergent to 2.07 % and 2.18 %, respectively) revealed that the crystallized rotamers have a DeltaHT conformation that is in agreement with all previously reported X-ray structures of [Pt(diamine)(nucleos(t)ide)(2)] complexes. This conformation allows the 5'-phosphate to be located in proximity to the Me(4)DACH ligand so that (P)O...HC(N) hydrogen-bond interactions exists in both complexes. For both structures, the canting of the guanine planes on the coordination plane is right-handed (R; canting angle (Phi) of 80.9 degrees and 73.2 degrees, respectively); this indicates that the canting direction is driven by the HT conformation chirality (Delta for both compounds) and not by the chirality of the carrier ligand (different for the two compounds). Density functional theory analysis of the conformational space as a function of Phi indicated a good agreement between the computed and experimental structures. The increase in energy for Phi values below 65 degrees and 55 degrees (for 1 and 2, respectively) is mainly due to the short intramolecular contacts between C(8)H and the cis N-Me groups on the same side of the platinum coordination plane.     

A new family of mono- and dicarboxylic ruthenium complexes [Ru(DIP)2(L2)]2+ (DIP = 4,7-diphenyl-1,10-phenanthroline): synthesis, solution behavior, and X-ray molecular structure of trans-[Ru(DIP)2(MeOH)2][OTf]2

A new family of ruthenium complexes of general formula [Ru(DIP)2(L2)]2+, where DIP = 4,7-diphenyl-1,10-phenanthroline, a bidentate ligand with an extended aromatic system, was prepared and fully characterized. When L is a monodentate ligand, the following complexes were obtained: L = CF3SO3(-1) (2), CH3CN (3), and MeOH (4). When L2 is a bidentate ligand, the compounds [Ru(DIP)2(Hcmbpy)][Cl]2 (5) and [Ru(DIP)2(H2dcbpy)][Cl]2 (6) were prepared (Hcmbpy = 4-carboxy-4'-methyl-2,2-bipyridine, H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine). Complex [Ru(DIP)2(MeOH)2][OTf]2 (4) displayed a trans configuration of the DIP ligands, which is rare for octahedral complexes featuring DIP bidentate ligands. DFT calculations carried out on 4 showed that the cis isomer is more stable by 12.2 kcal/mol relative to the trans species. The solution behaviors of monocarboxylic complex [Ru(DIP)2(Hcmbpy)][Cl]2 (5) and dicarboxylic complex [Ru(DIP)2(H2dcbpy)][Cl]2 (6) were investigated by 1H NMR spectroscopy. VT-NMR, concentration dependence, and reaction with NaOD allowed us to suggest that aggregation of the cationic species in solution, especially for 6, originates mainly from hydrogen bonding interactions.     

X-ray supramolecular structure, NMR spectroscopy and synthesis of 3-methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones formed by the unexpected cyclization of 3-[1-(phenyl-hydrazono)ethyl]-chromen-2-ones

The molecular structures of nine 3-methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-one isomers, obtained by the oxidative cyclization of the corresponding 1-phenylhydrazono chromen-2-ones with copper acetate as catalyst, are reported. The molecular and supramolecular structures of the 8-chloro, 8-bromo- and 8-nitro isomers 2b-d, were established by X-ray diffraction. The halogenated isomers 2b and 2c are isomorphs, they crystallize as a triclinic system, space group P-1 with two molecules in the asymmetric unit. Compound 2d crystallizes as a monoclinic system, space group P2?/m with two molecules in the unit cell. The 1-phenyl ring [Cg(4)] is almost perpendicularly positioned to the chromene-pyrazole ring system. This conformation is in agreement with the anisotropic NMR shielding effect exerted by the phenyl ring over H-9 in solution. The supramolecular architecture is almost controlled by C-H···A (A = O, p) and face to face p-stacking interactions. The observed p-stacking trend between chromene and pyrazole rings is given by the overlapping between the best donor and acceptor rings in each compound.     

Halide abstraction reactions of tin(IV) chloride and the group 3 chlorides MCl3 (M = Sc,Y, La) in thf: crystal and molecular structure of [ScCl2(thf)4][SnCl5(thf)]

Direct treatment (1:1) of MCl₃ (M = Sc, Y or La) with SnCl4 in thf provides colourless compounds of the type ScSnCl₇(thf)₅ and MSnCl₇(thf)₆ (M = Y, La), which have been characterised by elemental analysis and spectroscopic studies. An X-ray determination of ScSnCl₇(thf)₅ reveals an ionic structure comprising individual six-coordinate [ScCl₂(thf)₄]⁺ cations and [SnCl₅(thf)]^-anions. The cations feature an octahedral metal geometry in which a linear Cl-Sc-Cl unit is surrounded by an equatorial girdle of four solvent (thf) molecules.     

Novel polyoxometalate-templated, 3-D supramolecular networks based on lanthanide dimers: synthesis,structure, and fluorescent properties of [Ln2(DNBA)4(DMF)8][Mo6O19] (DNBA = 3,5-dinitrobenzoate)

The spherical Lindquist type polyoxometalate, Mo(6)O(19)(2)(-), has been used as a noncoordinating anionic template for the construction of novel three-dimensional lanthanide-aromatic monocarboxylate dimer supramolecular networks [Ln(2)(DNBA)(4)(DMF)(8)][Mo(6)O(19)] (Ln = La 1, Ce 2, and Eu 3, DNBA = 3,5-dinitrobenzoate, DMF = dimethylformamide). The title compounds are characterized by elemental analyses, IR, and single-crystal X-ray diffractions. X-ray diffraction experiments reveal that two Ln(III) ions are bridged by four 3,5-dinitrobenzoate anions as asymmetrically bridging ligands, leading to dimeric cores, [Ln(2)(DNBA)(4)(DMF)(8)](2+); [Ln(2)(DNBA)(4)(DMF)(8)](2+) groups are joined together by pi-pi stacking interactions between the aromatic groups to form a two-dimensional grid-like network; the 2-D supramolecular layers are further extended into 3-D supramolecular networks with 1-D box-like channels by hydrogen-bonding interactions, in which hexamolybdate polyanions reside. The compounds represent the first examples of 3-D carboxylate-bridged lanthanide dimer supramolecular "host" networks formed by pi-pi stacking and hydrogen-bonding interactions encapsulating noncoordinating "guest" polyoxoanion species. The fluorescent activity of compound 3 is reported.     

Structure, stability, and interconversion barriers of the rotamers of cis-[Pt(II)Cl(2)(quinoline)2] and cis-[Pt(II)Cl(2)(3-bromoquinoline)(quinoline)] from X-ray crystallography, NMR spectroscopy and molecular mechanics evidence

Reported are the preparations of cis-[PtCl(2)(quinoline)(2)] and cis-[PtCl(2)(3-bromoquinoline)(quinoline)] and an investigation of the stabilities and interconversion of the rotamer forms of these complexes. Both head-to-head (HTH) and head-to-tail (HTT) rotamer forms are found in the crystal structure of cis-[PtCl(2)(quinoline)(2)]. The NOESY NMR spectrum of cis-[PtCl(2)(quinoline)(2)] in dmf-d(7) at 300 K is consistent with conformational exchange brought about by rotation about the Pt-N(quinoline) bonds. H.H nonbonded distances between H atoms of the two different quinoline ligands were determined from NOESY data, and these distances are in accord with those observed in the crystal structure and derived from molecular mechanics models. cis-[PtCl(2)(3-bromoquinoline)(quinoline)] was prepared to alleviate the symmetry-imposed absence of inter-ring H2/H2 and H8/H8 NOESY cross-peaks for cis-[PtCl(2)(quinoline)(2)]. Molecular mechanics calculations on the complexes show the HTT rotamers to be 1-2 kJ mol(-)(1) more stable than the HTH forms, consistent with the (1)H spectra where the intensities of resonances for the two forms are approximately equal. Variable-temperature (1)H NMR spectra of cis-[PtCl(2)(quinoline)(2)] in dmf-d(7) indicate a rotational energy barrier of 82 +/- 4 kJ mol(-)(1). Variable-temperature (1)H NMR spectra indicate that the Br substituent on the quinoline ring does not affect the energy barrier to interconversion between the HTT and HTH forms (79 +/- 5 kJ mol(-)(1)). The steric contribution to the rotation barrier was calculated using molecular mechanics calculations and was found to be approximately 40 kJ mol(-)(1), pointing to a possible need for an electronic component to be included in future models.     

A chiral molecular conductor: synthesis, structure, and physical properties of [ET]3[Sb2(L-tart)2].CH3CN (ET = bis(ethylendithio)tetrathiafulvalene; L-tart = (2R,3R)-(+)-tartrate)

The salt [ET](3)[Sb(2)(L-tart)(2)].CH(3)CN (1) has been obtained by electrocrystallization of the organic donor bis(ethylendithio)tetrathiafulvalene (ET or BEDT-TTF) in the presence of the chiral anionic complex [Sb(2)(L-tart)(2)](2-) (L-tart = (2R,3R)-(+)-tartrate). This salt crystallizes in the chiral space group P2(1)2(1)2(1) (a = 11.145(2) angstroms, b = 12.848(2) angstroms, c = 40.159(14) angstroms, V = 5750.4(14) angstroms(3), Z = 4) and is formed by alternating layers of the anions and of the organic radicals in a noncentrosymmetric alpha-type packing. This compound shows a room temperature electrical conductivity of approximately 1 S.cm(-1) and semiconducting behavior with an activation energy of approximately 85 meV. Analysis of the magnetic susceptibility and band structure, however, suggests that this compound should be a narrow band gap semiconductor.     

Facile synthesis of pyridinium aryltetrachlorotellurates: crystal and molecular structure of [C5H6N][RTeCl4] (R = m‐O2NC6H4, p‐NCC6H4)

Arylation of TeCl₄ with arylboroxine–pyridine complexes [(RBO)₃·C₅H₅N, where R = m‐O₂NC₆H₄ ( 1 ), p‐O₂NC₆H₄ ( 2 ), m‐NCC₆H₄ ( 3 ), p‐NCC₆H₄ ( 4 )] and advantageous moisture provided good yields of the pyridinium aryltetrachlorotellurates [C₅H₆N][RTeCl₄] [R = m‐O₂NC₆H₄ ( 5 ), p‐O₂NC₆H₄ ( 6 ), m‐NCC₆H₄ ( 7 ), p‐NCC₆H₄ ( 8 )]. Compounds 5 and 8 have been investigated by X‐ray crystallography. Key features of both crystal structures are intermolecular secondary Te???Cl interactions between the aryltetrachlorotellurate anions and weak association of the cations and anions. Electrospray mass spectra of compound 5 reveal that the associative interactions also play a role in solution. Copyright © 2005 John Wiley & Sons, Ltd.     

High-temperature synthesis, single-crystal X-ray structure determination and solid-state NMR investigations of Ba7[SiO4][BO3]3CN and Sr7[SiO4][BO3]3CN

The novel alkaline earth silicate borate cyanides Ba₇[SiO₄][BO₃]₃CN and Sr₇[SiO₄][BO₃]₃CN have been obtained by the reaction of the respective alkaline earth metals M=Sr, Ba, the carbonates M^IICO₃, BN, and SiO₂ using a radiofrequency furnace at a maximum reaction temperature of 1350°C and 1450°C, respectively. The crystal structures of the isotypic compounds M^II₇[SiO₄][BO₃]₃CN have been determined by single-crystal X-ray crystallography (P6₃mc (no. 186), Z=2, a=1129.9(1) pm, c=733.4(2) pm, R₁=0.0336, wR₂=0.0743 for M^II=Ba and a=1081.3(1) pm, c=695.2(1) pm, R₁=0.0457, wR₂=0.0838 for M^II=Sr). Both ionic compounds represent a new structure type, and they are the first examples of silicate borate cyanides. The cyanide ions are disordered and they are surrounded by Ba²⁺/Sr²⁺ octahedra, respectively. These octahedra share common faces building chains along [001]. The [BO₃]³⁻ ions are arranged around these chains. The [SiO₄]⁴⁻ units are surrounded by Ba²⁺/Sr²⁺ tetrahedra, respectively. The title compounds additionally have been investigated by ¹¹B, ¹³C, ²⁹Si, and ¹H MAS-NMR as well as IR and Raman spectroscopy confirming the presence of [SiO₄]⁴⁻, [BO₃]³⁻, and CN⁻ ions.     

Examination of the structure in solid state of amino analogs of 4,4′-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, C CP/MAS NMR, and theoretical calculations

A single crystal of X-ray diffraction structures is presented for 4,4′-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4′-[1,5-(N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/gauche conformation, whereas in 3 – a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of NH···N in 2 and of CH···N in 3. Various conformations of both molecules were reflected in ¹³C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.