Enantioselective cyclopropanation reaction using a conformationally fixed pyridinium ylide through a cation-π interaction

Using a chiral pyridinium ylide with a fixed conformation through a cation-π interaction performs enantioselective cyclopropanation of electron-deficient olefins. ¹H NMR, X-ray structural analysis and DFT calculations elucidated the self-complexation and the face-to-face arrangement between the pyridinium and the phenyl rings. The absolute configuration of the product was determined after conversion into a bicyclic cyclopropane derivative.     

Synthesis and structure of vanadium (IV) single-stranded dihelicate involving multi-ring nitrogen-heterocyclic ligand

1 The single stranded-helicate Vanadium(IV) complex [V₂O₂Cl₄(L)(H₂O)₂] (1) involving heterocyclic bis-bidentate ligand viz. 3,3^/-dipyridine-2-yl-[1.1^/]bi[imidazo[1,5-a]pyridineyl] (L) with biological relevance is prepared and characterized by X-ray diffraction analysis. The compound lacks molecular center of symmetry where coordination environments around V(1) and V(2) centres are distorted octahedral (V···V# separation of 5.827 Å). Structure of the compound in the solid state structure shows anion?π interactions, classical and C_arene-H---anion non-classical H-bonding interactions. These interactions play significant roles in shaping the extended structure of this molecule.     

A unique twisted rod-like pattern due to π-π stacking induced host-guest self-assembly

Here, we reported a unique twisted rod-like nano-architecture of as-synthesized 4-fluorocinnmaoyl chloride derived polynorbornene (PNORCNF) on the addition of 1-pyrenemethanol (PM) as a sensing probe. A significant change in the PNORCNF/PM microenvironment's polarity was observed with increasing PM concentration keeping the solvent (THF) unaltered. The change in polarity could be well documented with the morphological changes of the PNORCNF/PM system. We proposed π-π interaction between PM and cinnamoyl moiety of PNORCNF for this type of well-controlled hierarchical self-aggregation.     

Substrate-induced adjustment of “slipped” π–π stacking: en route to obtain 1D sandwich chain and higher order self-assembly supramolecular structures in solid state

‘Slipped’ π?π stacking between flexible macrocycle 1⁴⁺ (cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylene benzene)) and neutral small molecules induce one-dimensional (1D) ‘sandwich’ chain self-assembly. Unlike most of the reported π?π stacking system, the 1D “sandwich” chain expands with the direction parallel to stacking π surfaces on 1⁴⁺ and that on molecule 2, 3, 4 or 5 (2 = p-xylene, 3 = benzene-1,4-diamine, 4 = 4,4′-bipyridine, 5 = [1,1′-biphenyl]-4,4′-diol). Moreover, the π?π stacking modes of 1D self-assembly are seriously small molecule adduct dependent. Combined with the other weak interactions (e.g. intermolecular hydrogen bonding), the new substrate design and control strategy can expand the 1D ‘sandwich’ chain (e.g. [1⁴⁺·4]_n) into higher order structure (e.g. two-dimensional (2D) network [1⁴⁺·4·6]_n, 6 = hydroquinone) even in large scale (~280 mg). This 2D network structure, which keeps stable under 423 K, shows highly selective gas absorption of CO₂ over N₂.     

Synthesis, Structure and Thermal Stability of [Tm(TBTA)1.5(bipy)(H2O)2]n

The complex [Tm(TBTA)1.5(bipy)(H2O)2]n (H2TBTA = 2,3,5,6-tetrabromoterephthalic acid, bipy = 2,2-bipyridyl) has been synthesized in water-methanol solution at ambient temperature and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum and thermogravimetric analysis. The crystal belongs to triclinic, space group P1 with a = 11.1429(2), b = 11.485(2), c = 12.872(2), V = 1498.1(5)3 , Z = 2, C22H14Br6N2O9Tm, Mr = 1098.74, Dc = 2.436 g/cm3 , μ(MoKα) = 11.013 mm-1 , F(000) = 1022, T = 296.15 K, the final R (I >2σ(I)) = 0.0494 and wR (all data) = 0.1246. The asymmetric unit of the complex is composed of one Tm ion, one and a half of coordinated TBTA 2-anions, one bipy, two coordinated and one lattice water molecules. The adjacent metal ions are bridged by TBTA 2- anions to form a 2D wave-like layer.     

Synthesis and Crystal Structure of a New Complex Zn(Ⅱ)L_2·2CH_3OH(H_2L = 4-Chloro-2-(2,3-dihydro-1H-benzoimidazol-2-yl)-phenol)

A new complex Zn(Ⅱ)L2·2CH3OH(H2L = 4-chloro-2-(2,3-dihydro-1H-ben-zoimi-dazol-2-yl)-phenol) has been prepared and characterized by single-crystal X-ray diffraction analysis and elemental analysis.The crystal is of triclinic system,space group P1 with a = 9.2905(10),b = 10.3555(13),c = 14.9590(14) ,α = 101.0340(10),β = 101.261(2),γ = 99.1660(10)o,V = 1356.1(3) 3,Z = 2,C28H24Cl2N4O4Zn,Mr = 616.78,Dc = 1.510 g/cm3,μ = 1.145 mm·1,F(000) = 632,the final R = 0.0379 and wR = 0.0830 for 3606 observed reflections with I 2σ(I).The Zn(Ⅱ) atom presents a distorted square pyramidal coordination involving two H2L ligands.The hydrogen bonds and π···π stacking interactions extend the complex into a two-dimensional framework.     

Syntheses and characterization of two copper pyridine-dicarboxylate compounds containing water clusters

A new homonuclear and heterodinuclear pyridine-2,6-dicarboxylate complexes, formulated as (enH₂)[Cu(dipic)₂]·2.5H₂O (1) and [Cu(μ-dipic)₂Zn(H₂O)₅]·2H₂O (2) (en = ethylenediamine, dipic = pyridine-2,6-dicarboxylate) were synthesized according the reactions between the three species of copper(II) and zinc(II) nitrate, ethylenediamine and pyridine-2,6-dicarboxylic acid. Complexes have been characterized by the methods of elemental, spectroscopic (IR and UV–Vis), thermal (TG/DTG, DTA) analysis, magnetic measurement and single crystal X-ray diffraction. Correlation coefficient, activation energies, E∗; pre-exponential factor, A; entropies, S∗; enthalpies, H∗ and Gibbs free energies, G∗ of the thermal decomposition reactions have been calculated under the derivations from thermogravimetric (TG) and differential thermogravimetric (DTG) curves, using the Coats–Redfern and Horowitz–Metzger methods. Complex 1 belonged to a six-coordinate behavior with a distorted octahedral geometry around Cu(II), that the structure contains two pyridine-2,6-dicarboxylate species as a tridentate ligands and ethylenediaminium cation as a counter ion as well as 2.5 uncoordinated water molecules. On the other hand complex 2 contains six-coordinated Cu(II) and Zn(II) ions, which are linked by two O atoms of the same carboxyl group from dipicolinic acid. The dipicolinate dianions again behave as tridentate ligands in 2. Two uncoordinated water molecules are also present in the structure. The structure units of 1 and 2 are mutually held by the hydrogen bonds and π?π interactions. There is also a C–O?π interaction in 2. The Cu(II) complexes are connected to one another via O–H?O hydrogen bonds, forming water clusters, which play an important role in the stabilization of the crystal structure. In the water clusters, the water molecules are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.     

Effect of Solvent on the Morphology and Microstructure of Light Emitting Organogels

Summary: Self assembly of oligo(phenylene vinylene) based gelator is studied in three different solvents namely, trans-decahydronaphthalene (trans-decalin), benzene and benzyl alcohol. The morphology as well as the thermal properties are different for benzyl alcohol gel as compared to those gels in trans-decalin or benzene. X-ray diffraction studies indicate that in case of benzyl alcohol gel, the molecular organization is highly ordered with respect to the fibrils grown in other two solvents.     

New triorganotin(IV) complexes of polyfunctional S,N,O-ligands: Supramolecular structures based on π?π and/or C-H?π interactions

A series of new triorganotin(IV) complexes with 4-hydroxy-2-mercapto-6-methylpyrimidine (L¹H₂), 4-hydroxy-2-mercapto-pyrimidine (L²H₂), 2,4(1H,3H)-pyrimidinedithione (L³H₂) (Scheme 1) of the type R₃SnLSnR₃ (R = Me 1, 4, 7; R = Ph 2, 5, 8; R = PhCH₂3, 6, 9) have been synthesized by reactions of triorganotin(IV) chloride and corresponding ligands. All complexes are characterized by elemental analyses, IR spectra and NMR spectra analyses. Among them, complexes 2, 5 and 8 are also characterized by X-ray crystallography diffraction analyses. Significant π?π stacking, C-H?π interactions and intramolecular hydrogen bonds stabilize these structures.     

Formations and structures of cobalt dithiolene complexes with nitrogen group-substituted cyclopentadienyl ligands

The cobalt dithiolene complex with the sulfonylamide-substituted Cp ligand [(C₅H₄-NHTs)Co{S₂C₂(COOMe)₂}] (1, Ts = p-SO₂C₆H₄Me) reacted with TsOH · H₂O to give [(C₅H₄-NH₂)Co{S₂C₂(COOMe)(H)}] (2), [(C₅H₄-NHTs)Co(S₂C₂H₂)] (3) and [(C₅H₄-NHTs)Co{S₂C₂(COOMe)(H)}] (4). Complex 1 was dissolved in a basic aqueous solution, and the anion reacted with Me₂SO₄ to form the N-methylated product [{C₅H₄-N(Me)Ts}Co{S₂C₂(COOMe)₂}] (5); the carboxylic acid complex [{C₅H₄-N(Me)Ts}Co{S₂C₂(COOMe)(COOH)}] (6) formed by a base hydrolysis. The X-ray crystal structures of complexes 4-6 and the methylsulfonylamide-substituted Cp complex [(C₅H₄-NHMs)Co{S₂C₂(COOMe)₂}] (7, Ms = SO₂Me) were determined. In the crystal structures of complexes 4 and 7, intermolecular hydrogen bondings of NH?O (ca. 2.1 Å) and NH?S (ca. 3.1 Å) were observed. Complex 6 showed the OH?O intermolecular hydrogen bonding (ca. 1.6 Å) of COOH moiety between two molecules, and these two molecules were assembling each other. Complexes 5 and 6 showed an intramolecular π-π interaction between the aromatic cobaltadithiolene and benzene rings, and complex 5 also has intermolecular π-π interactions between two benzene rings, and between two cobaltadithiolene rings.