Channel-dependent conformations of single-strand polymers in organic networks composed of tetrapodal adamantanes with N-heterocyclic moieties

Three tetrapodal adamantanes bearing imidazole (1), benzimidazole (2), and phenylimidazole (3) moieties were designed and synthesized. The co-crystallization of polyethylene glycol (PEG) and tetrapodal molecules provided polymer-inclusion organic crystals (1a–3a). Single crystal X-ray analysis revealed that organic networks possessing various channels were produced by CH/N and CH/π interactions. The PEG chain had zigzag, kink-type, and helical conformations.     

Two novel 3-D bismuth oxalates with organic amines protruding in channels

Two novel 3-D oxalate-containing bismuth compounds of formula (C₃N₂H₅)₂ [Bi₂(C₂O₄)₄(H₂O)₂]·2H₂O 1 and [NH(C₂H₅)₃][Bi₃(C₂O₄)₅] 2 were obtained by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic P2/n space group with , , , β=97.280(3)°, Z=4, R₁=0.0340 and wR₂=0.0766 for unique 4734 reflections I>2σ(I). Compound 2 belongs to the orthorhombic Pbcn space group with , , , Z=4, R₁=0.0222 and wR₂=0.0568 for unique 2472 reflections I>2σ(I). The Bi^III centers have nine-fold coordination for 1 and eight-fold for 2 with the Bi atoms in distorted monocapped square antiprism and distorted dodecahedron, respectively. And oxalate ligands adopt different coordination modes: bidentate for 1, bidentate and tricoordinate for 2. Compounds 1 and 2 are both 3-D open-framework structures containing channels with guest molecules. These two compounds exhibit intense blue luminescence with the emission peaks at 419 nm for 1 and 442 nm for 2, respectively, in the solid state at room temperature. These compounds with novel structural frameworks could be useful in the field of photoactive materials.     

The role of CH/pi interaction in the stabilization of less-soluble diastereomeric salt crystals

Enantiopure 2-naphthylglycolic acid (NGA) and cis-1-aminobenz[f]indan-2-ol (ABI) were rationally designed as new resolving agents on the model of mandelic acid (MA) and cis-1-aminoindan-2-ol (AI), respectively. As expected, NGA and ABI showed superior chiral recognition ability to racemates, compared with MA and AI. In order to clarify any factors governing the chiral recognition abilities of NGA and ABI, the crystal structures of their less- and more-soluble diastereomeric salts were determined by X-ray crystallographic analyses and revealed that CH/pi interactions play an intrinsic role in chiral recognitions. A theoretical investigation was also performed with the periodic ab initio method by using the X-ray crystal structures of the less-soluble salt crystals with AI and ABI to find the unique properties of CH/pi interaction in the crystalline state, which largely contributed to the stabilization of the crystals.     

Complexes of heteroscorpionate trispyrazolylborate ligands. Part XI. Weak CH/π interactions in crystals of hydrotris(3-phenylpyrazolyl)boratothallium(I) and hydrobis(5-methyl-3-phenylpyrazolyl)(3,5-dimethylpyrazol-yl)boratothallium(I) studied by X-ray crystallography

Thallium(I) complexes of heteroscorpionate hydrobis(3-phenyl-5-methylpyrazolyl)(3,5-dimethylpyrazol-yl)borate and hydrotris(3-phenylpyrazol-1-yl)borate were studied crystallographically. Both ligands were coordinated in κ³ fashion via N₂ atoms of pyrazol-1-yl moieties. Both compounds crystallize as centrosymmetric dimers in which weak CH/π intra- and interdimer interactions are responsible for arrangement in crystal structure.     

Synthesis and characterization of copper(II) and cobalt(II) complexes with two new potentially hexadentate Schiff base ligands. X-ray crystal structure determination of one copper(II) complex

Two new potentially hexadentate N₂O₄ Schiff base ligands 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy) phenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L¹] and 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy)-5-tert-butylphenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L²] were prepared from the reaction of 3,5-di-tert-butyl-2-hydroxy benzaldehyde with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. From the direct reaction of ligands [H₂L¹] and [H₂L²] with copper(II) and cobalt(II) salts in methanolic solution and in the presence of N(Et)₃ the neutral [CuL¹], [CuL²], [CoL¹] and [CoL²] complexes were prepared. All complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, mass spectra, molar conductance (Λ_m), UV-Vis spectra and in the case of [CuL²] with X-ray diffraction. X-ray crystal structure of [CuL²] showed that the complex contains copper(II) in a distorted square planar environment of N₂O₂ donors. Three CH/π interactions were observed in the molecular structure of latter complex.     

Pure through‐bond state in organic molecules for analysis of the relationship between intramolecular interactions and total energy

Ab initio configuration interaction through‐space/bond interaction analysis was proposed for the examination of specific intramolecular interactions including the effect of electron correlations. To test the effectiveness of our method, we applied it to rotational barrier in ethane. The results of our test suggest that the insensitivity of the ethane barrier to geometric relaxations is intimately connected with the cancellation of interactions through orbital overlaps and other factors. The orbital overlaps include exchange repulsion and hyperconjugation; other factors include classic Coulomb interaction and changes in bond orbital energy. The rotational state without the barrier (pure through‐bond state) can be achieved by deleting not only the “vicinal” interactions between the C? H bonds that belong to different methyl groups but also the “geminal” interactions within the methyl groups. Our mixing analysis of molecular orbitals supports the superiority of the staggered conformer by hyperconjugation. Moreover, it was demonstrated that our treatment could be applied to excited states as well as to the ground state, including electron correlation effects. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Syntheses and crystal structures of two new coordination polymers of Cd(II) using organic spacer and inorganic-bridging ligands

Two new cadmium (II) complexes [Cd(hmt)(dca)₂] _n (1) and [Cd₃(hmt)₂(SeCN)₆(H₂O)₂] _n (2) (hmt=hexamethylenetetramine, dca=dicyanamide) have been synthesized and characterized by X-ray single-crystal analysis. The complex 1 is a 2D rectangular grid of octahedral cadmium (II) with CdN₆ chromophore where cadmium centers are doubly bridged by dicyanamide and hmt along a-axis, which are interlinked by dicyanamide running along c-axis. Whereas, complex 2 is a 1D chain of octahedral cadmium (II) with a three-leg ladder topology running along a-axis. The Cd(II) centers are doubly bridged through SeCN (infinite rail) along a-axis and singly bridged by hmt (two-step rung) along c-axis, having cadmium centers with CdSe₂N₃O and CdSe₂N₄ chromophores. The adjacent chains through H-bonding between coordinated water and hmt, and SeSe interaction are extended to 2D supramolecular architecture.     

A characteristic ribbon-like supramolecular structure and intermolecular D–A interactions in the crystals of triptycenequinones, triptycene-TCNQs and their clathrates as studied by X-ray investigations

A common ribbon-like structure was found in the crystals of triptycenequinones (TPQs), triptycene-TCNQs (TP-TCNQs) and their clathrates. The characteristic structure can be regarded as a supramolecular unit the formation of which is aided by weak intermolecular D–A interactions. This view is supported by the host–guest D–A interactions appeared in the crystals of the clathrates of 5,8-dimethyl-TPQ and 5,8-dimethoxy-TP-TCNQ. Intermolecular C–HO hydrogen bonds seem to be present in TPQ derivatives.     

Intra‐ and intermolecular interactions in crystals of polar molecules. A study by the mixed quantum mechanical/molecular mechanical SCMP‐NDDO method

Stabilization energies of crystals of polar molecules were calculated with the recently developed NDDO‐SCMP method that determines the wave function of a subunit embedded in the symmetrical environment constituted by the copies of the subunit. The total stabilization energies were decomposed into four components. The deformation energy is the difference between the energy of the molecule in the geometries adopted in the crystal on the one hand, and in vacuo, on the other hand. Further energy components are derived from the molecular geometry found in the crystal phase. The electrostatic component is the interaction energy of the molecule with the crystal field, corresponding to the charge distribution obtained in vacuo. The polarization component is the energy lowering resulted in the self‐consistent optimization of the wave function in the crystal field. The rest of the stabilization energy is attributed to the dispersion–repulsion component, and is calculated from an empirical potential function. The major novelty of this decomposition scheme is the introduction of the deformation energy. It requires the optimization of the structural parameters, including the molecular geometry, the intermolecular coordinates, and the cell parameters of the crystal. The optimization is performed using the recently implemented forces in the SCMP‐NDDO method, and this new feature is discussed in detail. The calculation of the deformation energy is particularly important to obtain stabilization energies for crystals in which the molecular geometry differs considerably from that corresponding to the energy minimum of the isolated molecule. As an example, crystals of diastereoisomeric salts are investigated. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1679–1690, 2001     

Correlation between proton transfer and 35Cl NQR frequency as well as molecular geometry of chloranilic acid in co‐crystals with some organic bases

Proton transfer in hydrogen‐bonded organic co‐crystals of chloranilic acid with some organic bases was investigated by nuclear quadrupole resonance (NQR) spectroscopy. The ³⁵Cl NQR frequencies of chloranilic acid molecule as well as ¹⁴N NQR frequencies of the organic base molecule were measured with the conventional pulse methods as well as double‐resonance methods, respectively. The extent of proton transfer in the O···H···N hydrogen bond was estimated from Townes–Dailey analysis of the ¹⁴N NQR parameters. The ³⁵Cl NQR frequency and molecular geometry of chloranilic acid are correlated to the extent of proton transfer in the protonation process of the organic base molecule. It is shown that the hydrogen bond affects the π‐electron system of chloranilic acid. Geometry dependence of the O···H···N hydrogen bond, i.e. the H? N valence bond order versus the hydrogen‐bond geometry correlation is also discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

DNA/BSA‐binding property and in vitro anticancer activity of a new dicopper(II) complex with N‐(2‐hydroxy‐5‐nitrophenyl)‐N′‐[3‐(diethylamino)propyl]oxamide as bridging ligand: Synthesis and crystal structure

A new oxamido‐bridged dicopper(II) complex formulated as [Cu₂(ndpox)(bpy)(CH₃OH)₂]‐ (ClO₄), where H₃ndpox is N‐(2‐hydroxy‐5‐nitrophenyl)‐N′‐[3‐(diethylamino)propyl]oxamide; and bpy represents 2,2′‐bipyridine, was synthesized and structurally characterized using X‐ray single‐crystal diffraction and other methods. In the molecule, the endo‐ and the exo‐copper(II) ions bridged by the cis ‐ndpox³⁻ ligand are in {N₃O₂} and {N₂O₃} square‐ pyramidal environments, respectively. There is a three‐dimensional hydrogen bonding network dominated by O‐H···O and C‐H···O interactions in the crystal. The reactivity toward DNA/protein bovine serum albumin (BSA) revealed that the complex could interact with herring sperm DNA (HS‐DNA) through the intercalation mode, and effectively quench the intrinsic fluorescence of BSA via a static process. Cytotoxicity studies suggest that the complex displays selective cancer cell antiproliferative activity. The present investigation confirmed that the combined effects of both electron‐withdrawing and hydrophobic groups on the bridging ligand in the dicopper(II) complex systems can increase DNA/BSA‐binding ability and in vitro anticancer activity.     

Self-powdering and nonlinear optical domain structures in ferroelastic β′-Gd2(MoO4)3 crystals formed in glass

Ferroelastic β′-Gd₂(MoO₄)₃, (GMO), crystals are formed through the crystallization of 21.25Gd₂O₃–63.75MoO₃–15B₂O₃ glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50–500 μm spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called “self-powdering phenomenon during crystallization” in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO₄)²⁻ tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals.     

Control of aggregate formation in poly(3‐hexylthiophene) by solvent,molecular weight,and synthetic method

Aggregate formation in poly(3‐hexylthiophene) depends on molecular weight, solvent, and synthetic method. The interplay of these parameters thus largely controls device performance. In order to obtain a quantitative understanding on how these factors control the resulting electronic properties of P3HT, we measured absorption in solution and in thin films as well as the resulting field effect mobility in transistors. By a detailed analysis of the absorption spectra, we deduce the fraction of aggregates formed, the excitonic coupling within the aggregates, and the conjugation length within the aggregates, all as a function of solvent quality for molecular weights from 5 to 19 kDa. From this, we infer in which structure the aggregated chains pack. Although the 5 kDa samples form straight chains, the 11 and 19 kDa chains are kinked or folded, with conjugation lengths that increase as the solvent quality reduces. There is a maximum fraction of aggregated chains (about 55 ± 5%) that can be obtained, even for poor solvent quality. We show that inducing aggregation in solution leads to control of aggregate properties in thin films. As expected, the field‐effect mobility correlates with the propensity to aggregation. Correspondingly, we find that a well‐defined synthetic approach, tailored to give a narrow molecular weight distribution, is needed to obtain high field effect mobilities of up to 0.01 cm²/Vs for low molecular weight samples (=11 kDa), while the influence of synthetic method is negligible for samples of higher molecular weight, if low molecular weight fractions are removed by extraction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012