Is It Conjugated or Not? The Theoretical and Experimental Electron Density Map of Bonding in -CHCHCOCH-C≡C-C≡C--CHCOCHCH.

The electron density of -CHCHCOCH-C≡CC≡C--CHCOCHCH has been investigated on the basis of single-crystal X-ray diffraction data collected to high resolution at 100 K and from theoretical calculations. An analysis of the X-ray data of the diyne showed interesting "liquidity" of electron distribution along the carbon chain compared to 1,2-diphenylacetylene. These findings are compatible with the results of topological analysis of Electron Localization Function (ELF), which has also revealed a larger (than expected) concentration of the electron density at the single bonds.

Analysis of charge density in nonaaquagadolinium(III) trifluoromethanesulfonate - insight into Gd-OH bonding.

The experimental charge-density distribution in [Gd(HO)](CFSO) has been analysed and compared with the theoretical density functional theory calculations. Although the Gd-OH bonds are mainly ionic, a covalent contribution is detectable when inspecting both the topological parameters of these bonds and the natural bond orbital results. This contribution originates from small electron transfer from the lone pairs of oxygen atoms to empty 5d and 6s spin orbitals of Gd.

Advances and Property Investigations of an Organic-Inorganic Ferroelectric: (diisopropylammonium)[CdBr].

The preparation of materials featuring more than one ferroelectric phase represents a promising strategy for controlling electrical properties arising from spontaneous polarization, since it offers an added advantage of temperature-dependent toggling between two different ferroelectric states. Here, we report on the discovery of a unique ferroelectric-ferroelectric transition in diisopropylammonium tetrabromocadmate (, (CHN)[CdBr]) with a value of 244 K, which is continuous in nature. Both phases crystallize in the same polar orthorhombic space group, 2.

Symmetry breaking structural phase transitions, dielectric properties and molecular motions of formamidinium cations in 1D and 2D hybrid compounds: (NHCHNH)[BiCl] and (NHCHNH)[BiBr].

Two organic-inorganic hybrid halobismuthates(iii), (NH2CHNH2)3[Bi2Cl9] (FBC) and (NH2CHNH2)3[Bi2Br9] (FBB), have been prepared with their structures revealed by single-crystal X-ray diffraction at various temperatures. FBC is characterized by one-dimensional (1D) [Bi2Cl9]3-∞ anionic chains built by edge-sharing BiCl6 octahedra, whereas FBB adopts a layer structure (2D) [Bi2Br9]3-∞. Both materials were found to exhibit a rich polymorphism in the solid state.

Chirality transfer between hexaazamacrocycles in heterodinuclear rare earth complexes.

Both the chiral hexaazamacrocyle L1 based on trans-1,2-diaminocyclohexane and the achiral hexaazamacrocyle L2 based on ethylenediamine form lanthanide(iii) dinuclear μ-hydroxo bridged complexes which have been characterized by NMR and CD spectroscopy. The homodinuclear complexes of the type [Ln(L1)(μ-OH)](NO) (Ln = Nd, Eu, Tb and Yb) have been synthesized in the enantiopure form and the X-ray crystal structures of Nd, Eu and Yb derivatives have been determined. The heterodinuclear cationic complexes [Ln(L1)Ln'(L2)(μ-OH)X] have been generated and characterized in solution by using the mononuclear complexes of L1 and L2 as substrates.

Charge-density distribution in sodium bis(4-nitrophenyl)phosphate.

The electron-density distribution in sodium bis(4-nitrophenyl)phosphate has been analyzed using the multipole refinement of X-ray diffraction data and of theoretical density-functional theory (DFT) calculations. The ester P-O bonds are particularly long and their topological parameters (density at the bond critical point, Laplacian) are lower than for other P-O bonds. Some disagreement between the experimental and theoretical charges of atoms constituting the nitro groups has been observed and the possible reasons are discussed.

Electron density distribution in tetralithium hypodiphosphate hexahydrate, Li4P2O6·6H2O.

Tetralithium hypodiphosphate hexahydrate, Li4P2O6·6H2O, forms a highly symmetrical crystal structure, where hypodiphosphate anions have \bar 3m (D3d) symmetry. Analysis of the charge distribution (experimental and theoretically calculated) shows that the charges of the P atoms are lower than in phosphates and phosphonates, whereas the O charges are similar. Values of both ρc and ∇(2)ρc suggest that the P-P bond is a weak covalent one, while the P-O one is polarized covalent, with topological parameters similar to those of P-O bonds in phosphates or phosphonates.

Charge-density distribution in potassium dihydrogen phosphoglycolate--a comparison of phosphate and phosphonate groups.

Analysis of the experimental and theoretical charge-density distribution in potassium dihydrogen phosphoglycolate has been performed. The P-O bonds in the phosphate group are more polarized and the P atom is more positively charged than in phosphonate groups. The P-O bonds belong to a transit closed-shell (or polar covalent) class, while the ester C-O bond is a covalent (or shared-shell) bond.

Controlling the macrocycle size by the stoichiometry of the applied template ion.

Reaction of 4-tert-butyl-2,6-diformylphenol with (1R,2R)- or (1S,2S)-1,2-diaminocyclohexane in the presence of 1 equivalent of Zn(2+) ions leads to selective formation of a chiral 2+2 macrocycle. Application of 0.5 equivalent of Zn(2+) ions under the same conditions leads to selective formation of a chiral 3+3 macrocycle, which forms a cavitand-shaped trinuclear double-decker complex with Zn(II).

Charge-density distribution in hydrogen methylphosphonates of calcium and lithium.

Two new crystal structures, calcium bis(hydrogen methylphosphonate), Ca(CH(3)PO(3)H)(2), and lithium hydrogen methylphosphonate, Li(CH(3)PO(3)H), have been obtained, and the experimental and theoretical charge densities, as well as their topological properties, are reported. Both compounds display layered structures. Each hydrogen methylphosphonate anion coordinates three metal cations in the calcium compound and four in the lithium one.

Charge density distribution in aminomethylphosphonic acid.

The experimental charge density distribution in aminomethylphosphonic acid has been determined from X-ray diffraction and its topological features have been analyzed. The results have shown that the P-O bonds are highly polarized, moreover the P-OH bond is weaker than the bonds to unprotonated O atoms. These facts have been confirmed by theoretical density functional theory (DFT) calculations, which have shown that the single, strongly polarized bonds within the phosphonate group are modified by hyperconjugation effects.

Helical lanthanide(III) complexes with chiral nonaaza macrocycle.

The chiral nonaazamacrocyclic amine L, which is a reduction product of the 3 + 3 Schiff base macrocycle, wraps around the lanthanide(III) ions to form enantiopure helical complexes. These Ce(III), Pr(III), Nd(III), Eu(III), Gd(III), Tb(III), Er(III), Yb(III) and Lu(III) complexes have been isolated in enantiopure form and have been characterized by spectroscopic methods. X-ray crystal structures of the Ln(III) complexes with L show that the thermodynamic product of the complexation of the RRRRRR-isomer of the macrocycle is the (M)-helical complex in the case of Ce(III), Pr(III), Nd(III) and Eu(III).

An ytterbium(II) complex with dimethyl ester of oxydiacetic acid.

An Yb(II) complex with dimethyl ester of oxydiacetic acid, [Yb(CH(3)OOCCH(2)OCH(2)COOCH(3))3](ClO4)2, has been obtained by electrochemical reduction and its crystal structure has been determined. The complex cations have the D3 (32) crystallographic symmetry. The compound shows a very broad absorption band, starting from 500 nm towards the UV region, and traces of luminescence with a maximum at 545 nm.

Two complexes of Sm(II) with crown ethers-electrochemical synthesis, structure and spectroscopy.

Two complexes of divalent samarium have been synthesized by electrochemical reduction in methanol-tetrahydrofuran solutions: [Sm(18-crown-6)(ClO4)2] and [Sm(15-crown-5)2](ClO4)2. In [Sm(18-crown-6)(ClO4)2] the metal cation is ten-coordinate and its coordination sphere comprises six oxygen atoms of the crown ligand and four oxygen atoms from two perchlorate anions. [Sm(15-crown-5)2](ClO4)2 shows a sandwich structure with decacoordinate samarium located between two 15-crown-5 molecules.

Crystal Structure and Absorption Spectroscopy of a Neodymium(III) Complex with Triethylenetetraaminehexaacetic Acid, Na(3)[Nd(TTHA)].2.5NaClO(4).7.617H(2)O.

The crystal structure and absorption spectroscopy results of the Na(3)[Nd(TTHA)].2.5NaClO(4).