Crystal structure and Hirshfeld surface analysis of the anionic tetrakis-complex of lanthanum(III) NMe4LaL 4 with the CAPh-ligand dimethyl (2,2,2-trichloroacetyl)phosphoramidate

The anionic tetrakis-complex of lanthanum(III) NMe4LaL 4 with the CAPh-ligand dimethyl (2,2,2-trichloroacetyl)phosphoramidate (HL), namely, tetramethylammonium tetrakis{2,2,2-trichloro-1-[(dimethoxyphosphoryl)imino]ethanolato}lanthanum(III), (C4H12N)[La(C4H6Cl3NO4P)4], has been synthesized, crystallized and structurally characterized by X-ray diffraction. The lanthanide ion is surrounded by four anionic, bis-chelating CAPh ligands forming the complex anion with a coordination number of eight for La3+ and NMe4 + as the counter-ion. The coordination polyhedron of the La3+ ion was interpreted as a triangular dodecahedron.

A bis-chelate o-vanillin-2-ethanolamine copper(II) complex bearing both imine and amine forms of the ligand

The molecular bis-chelate complex (2-{[(2-hydroxyethyl-κO)amino-κN]methyl}-6-methoxyphenolato-κO)(2-{[(2-hydroxyethyl)imino-κN]methyl}-6-methoxyphenolato-κO)copper(II), [Cu(C10H14NO3)(C10H12NO3)] or [Cu(HL im)(HL am); HL im = C10H14NO3; HL am = C10H12NO3, represents the first compound containing a salicylidene-2-ethanolamine type ligand in both imino HL im (Schiff base) and amino HL am (reduced Schiff base) forms that has been structurally characterized on the basis of X-ray data. Two molecules of the monodeprotonated ligands coordinate the CuII ion in an (N,O phen)-bidentate and an (N,O phen,O alc)-tridentate fashion in the case of the imino and amino forms, respectively. The shape of the CuN2O3 coordination polyhedron is a distorted square-pyramid (geometry index τ5 = 0.26). Intermolecular N—H...O and O—H...O hydrogen bonds, involving H atoms of the amino and hydroxyethyl groups, create a two-dimensional supramolecular array extending parallel to (010).

catena-Poly[[bis(1H-indole-5-carboxylato-κ2 O,O′)zinc(II)]-μ-4,4′-azobipyridine-κ2 N 1:N 1′]

The asymmetric unit of the title coordination polymer [Zn(C9H6NO2)2(C10H8N4)] n , consists of one ZnII cation, one bidentate 1H-indole-5-carboxylate (I5C) anion and half of a 4,4′-azobipyridine (Abpy) neutral ligand. In the coordination polyhedron, the ZnII ion adopts a distorted octahedral geometry. The coordination polymer is stabilized by a combination of N—H...O and C—H...π interactions, which leads to the formation of wave-like two-dimensional coordination polymeric layers.

MONO- AND MIXED- LIGAND COMPLEXES OF Yb(III) WITH NEW β-DIKETONES

New ytterbium (III) compounds with β-diketones (2,7-dimethyl-octene-1-dione-3,5 and 2,6-dimethylheptene-1-dione-3,5) and their derivatives with phenanthroline have been synthesized. The composition and chemical structure of the obtained complexes have been determined by several Phy­sico-chemical investigations. It has been shown, that the Yb (III) ion coordinates three ligand molecules and the coordination sphere of the complexes is supplemented by two mole­cules of water or a molecule of phenanthroline. It has been shown that the СN of the ytterbium ion is 8, the coordination polyhedron is a square antiprism, and the complex is characte­rized by no cubic symmetry. All synthesized compounds exhibit intense IR luminescence. The significant increase in the relative emission intensity of mixed ligand complexes is due to the additional antenna effect of the phenanthroline molecule.

The maximum surface area polyhedron with five vertices inscribed in the sphere {\bb S}^{2}

This article focuses on the problem of analytically determining the optimal placement of five points on the unit sphere {\bb S}^{2} so that the surface area of the convex hull of the points is maximized. It is shown that the optimal polyhedron has a trigonal bipyramidal structure with two vertices placed at the north and south poles and the other three vertices forming an equilateral triangle inscribed in the equator. This result confirms a conjecture of Akkiraju, who conducted a numerical search for the maximizer. As an application to crystallography, the surface area discrepancy is considered as a measure of distortion between an observed coordination polyhedron and an ideal one. The main result yields a formula for the surface area discrepancy of any coordination polyhedron with five vertices.

Magnetic behavior of the novel pentagonal-bipyramidal Erbium(III) complex (Et3NH)[Er(H2DAPS)Cl2]: high-frequency EPR study and crystal-field analysis

We report the synthesis, crystal structure and magnetic properties of the new heptacoordinated mononuclear erbium(III) complex (Et3NH)[Er(H2DAPS)Cl2] (H4DAPS = 2,6-diacetylpyridine bis-(salicylhydrazone)) (1). The coordination polyhedron around the Er(III) ion figures...

SYNTHESIS AND RESEARCH OF LANTHANIDE-CONTAINING HYBRID MATERIALS BASED ON POLYHEDRAL OLIGOMERIC SILSESQUIOXANES

New hybrid materials were synthesized based on meteacroacetophenate neodymium (III) and erbium (III) and polyhedral oligomeric sissesquioxane POSS formula C24H72Cl8N8O12Si8. A warehouse has been put in place for a new synthesis. In the IR spectra of the synthesized hybrid materials in the range of 400–650 cm–1 there are oscillation bands that correspond to the valence oscillations of the bonds (Ln-O) and (Ln-N) and the deformation oscillations of the chelate ring. The decrease in intensity compared to the spectra of Ln(mphpd)3 complexes is due to the appearance of valence oscillations of the Ln-N bond and steric difficulties that arise when the complex coordinates to the sizable siloxane molecule. An additional intense broad band appears in the IR spectra, which is characterized by fluctuations in the valence of the Si-O-Si siloxane bond with a maximum of 1050 cm-1. The presence of a wide absorption band in the range of 1500–1700 cm-1, characterized by valence oscillations of ν (CO) and ν (CC), confirms the bidentate-cyclic coordination of β-diketonates. Thus, the shape and position of the bands in the IR spectra indicate the formation of a hybrid structure of the composition POSS- [Ln (mphpd)3]4. The shape, position, displacement and splitting of the spectral bands in the electronic spectra and diffuse reflectance spectra indicate the passage of the processes of complexation and the formation of complexes of non-cubic symmetry with coordination number 8. Thus, the presence of insignificant displacements of the absorption bands indicates the invariance of the coordination environment and the geometry of the coordination polyhedron for metal complexes and hydride systems based on them. The shift of the bands of supersensitive transitions in comparison with the spectra of metal complexes indicates both additional coordination of nitrogen atoms of the silsesquioxane molecule and some deformation of the coordination polyhedron, which is due to steric difficulties. According to the set of data from thermal and spectroscopic studies, the structure of the obtained hybrid material can be represented as follows. The results of EDX analysis, the method of dynamic light scattering and microphotographs are consistent and indicate the nanodispersity of the obtained systems.

Understanding the abnormal lack of spectral shift with cation substitution in highly efficient phosphor La3Si6N11:Ce3+

The abnormal lack of spectral shift in La3Si6N11:Ce3+ is caused by a special coordination polyhedron of the truncated square pyramid type.

Neodymium (III) and erbium (III) complexes with new unsaturated β-diketones

In this work, the new coordination compounds of Nd(III) and Er (III) with b-diketonate ligands containing an unsaturated substituent at the a-position of the chelate ring (dimethylheptendione and dimethyloctendione) were synthesized. The composition and structure of the synthesized compounds were studied using physicochemical methods of analysis such as the elemental, NMR, IR and electron spectroscopy and thermogravimetric analysis. Using IR spectroscopy, it was established that ligands are bidentate-cyclically coordinated to metals. The results of thermogravimetric analysis indicate that the complexes are nonvolatile and decompose to oxides of the corresponding metals, and their coordination sphere is supplemented with water molecules. From the shape and position of the bands in the electronic absorption spectra and diffuse reflection spectra, it was determined that for the complexes Ln (b-dik)3.nH2O (Ln =Nd, Er, b-dik = dmhpd, dmod, n = 2-3) the tetragonal symmetry of the nearest coordination environment; coordination polyhedron is a square antiprism. When comparing the diffuse reflectance spectra of dimethylheptendionate and dimethyloktendionate complexes among themselves and with the previously studied complexes with methacrylacetophenone, it was noted that the shape of the spectra and the spectral splitting of the bands for the corresponding metals are not significantly different. This allows to conclude, that the coordination environment of the studied b-diketonate compounds is close.Based on the band shifts in the electronic spectra, the covalence parameters of the Ln–O bond and the oscillator strength were calculated, from which it was also shown that the nature of the substituent affects the covalence parameters, but does not affect the symmetry and structure of the coordination polyhedron. Based on the studies conducted, the monomeric structure of the synthesized complexes was definitely confirmed. Accordingly, they can be used in further work as monomers in polymerization reactions and the preparation of precursors of luminescent materials.