Lilia A. Sheludyakova

Zinc(II) complexes with an imidazolylpyridine ligand: luminescence and hydrogen bonding

ZnLCl and [H2L]2[ZnCl4], based on 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine (HL), have been synthesized. There is a short intraionic O–H···N hydrogen bond between the hydroxyimidazolyl and pyridyl of H2L+ cations (N···O 2.608(2) Å) in the structure of [H2L]2[ZnCl4]. The formation of this rather strong hydrogen bond is confirmed by IR spectroscopy through a broad band at 3200–2200 cm−1 and a band at 1655 cm−1. HL crystallizes in the form of a hemihydrate, HL·0.5H2O. HL assemble into infinite helical chains due to N–H···O intermolecular hydrogen bonds between the NH of imidazole and O of the N-oxide (O···N 2.623(2) Å). An unusual mid-IR pattern with three broad bands at 3373, 2530, and 1850 cm−1 is typical for strong hydrogen bonds, explained by resonance-assisted hydrogen bonding occurring in the helical chains. On cooling to 5 K, noticeable changes in the IR spectra of [H2L]2[ZnCl4] and HL·0.5H2O were observed. ZnLCl and [H2L]2[ZnCl4] exhibit bright photoluminescence with maxima of emission at 458 nm (for ZnLCl) and 490 nm (for [H2L]2[ZnCl4]). Graphical Abstract

Mononuclear coordination compounds based on a novel chelating triazole ligand : 1-vinyl-3-acetylamino-1,2,4-triazole

The synthesis, X-ray structure, magnetic and spectroscopic properties of new Co(II), Ni(II) and Cu(II) complexes with 1-vinyl-3-acetylamino-1,2,4-triazole (vaat) are reported. The crystal structures of [Ni(vaat)2(H2O)2](NO3)2 and [Cu(vaat)2(H2O)2]Cl2 have been determined by X-ray diffraction. In these mononuclear complexes, the metal ion is surrounded by two water molecules in axial positions and two oxygen and two nitrogen (N4) atoms coming from two trans-oriented chelating vaat molecules. Anions are noncoordinated and are involved in a hydrogen bonding network. The complex cations of [Cu(vaat)2(H2O)2]Cl2 are aligned within chains. In the structure of [Ni(vaat)2(H2O)2](NO3)2 the nitrate anions establish a bridge in the plane by hydrogen bonding giving a 2-D character for this compound. In addition, a colour change from pink to blue upon heating has been observed for [Co(vaat)2(H2O)2]Cl2, which is due to the removal of the two coordinated water molecules and the subsequent molecular reorganisation of the molecular structure. The synthesis, structure, magnetic and spectroscopic properties of new Co(II), Ni(II) and Cu(II) complexes with 1-vinyl-3-acetylamino-1,2,4-triazole (vaat) are reported. The crystal structures of [Ni(vaat)2(H2O)2](NO3)2 and [Cu(vaat)2(H2O)2]Cl2 have been determined by X-ray diffraction.

Spectral and structural analysis of sodium hydrophosphates and hydroarsenates

Anhydrous sodium hydrophosphates and arsenates and heptahxdrates were svnthesized and characterized by IR spectroscopy and X-ray diffractometry. Anhydrous sodium hxdrophosphate and hydroarsenate were found to be isostmctural. Unit cell parameters of Na2HAsO4 are calculated. Assignment of IR bands is given and comparative analysis of spectral and structural characteristics of the compounds is performed.

Preparation and reactivity of metal-containing monomers 53. Synthesis and stability of a cluster monomer (μ-H)Os3(μ-OCNMe2)(CO)9PPh2CH2CH=CH2 in solution

The stability of the complex (μ-H)Os3(μ-OCNMe2)(CO)9PPh2CH2CH=CH2 (1), which contains a free unsaturated functional group in the terminal ligand PPh2CH2CH=CH2, with respect to isomerization, chelation of the ligand, and other transformations in solutions was examined. No transformations of complex1 were observed in the course of synthesis from (μ-H)Os3(μ-OCNMe2)(CO)9NMe3 or upon heating in solution. Complex1 as well as complexes (μ-H)Os3(μ-OCNMe2)(CO)9PHPh2 and (μ-H)Os3(μ-OCNMe2)(CO)9PPh3, which were formed as admixtures, were isolated in the solid state and identified by1H,1H-{31P}, and1H-{1H} NMR, IR, and Raman spectroscopy and mass spectrometry.

Hexachlorocuprate(II) Anion: Vibration Spectra and Structure

For the complexes (CH8N4)2[CuCl6], (C2H9N5)2[CuCl6] · 2H2O, and (CH8N4O)4[CuCl6]Cl4, where (CH8N4)2+, (C2H9N5)2+, and (CH8N4O)2+ are the aminoguanidinium, biguanidium, and carbohydrazidium cations, respectively, IR and Raman spectra were taken and analyzed in the region of Cu—Cl vibrations. Polarization measurements of the Raman spectra of (CH8N4O)4[CuCl6]Cl4 single crystals were performed with the purpose of assigning the vibrations to symmetry types. Vibration spectra were calculated for the hexachlorocuprate ion in the given series of compounds, and the spectra of the examined complexes were compared with spectra of the previously known compounds incorporating the hexachlorocuprate(II) ion.

Isomerization and conformational transformations of theN-allyl-N-methylcarbamoyl bridging ligand in the (μ-H)Os3{μ-OCN(Me)CH2CH=CH2}(CO)10 complex

The (μ-H)Os3{μ-OCN(Me)CH2CH=CH2}(CO)10 complex containing an allylic fragment in theN,N-dialkylsubstituted carbamoyl briding ligand was synthesized. The stereo-chemical behavior of this complex in solution was investigated. As follows from the NMR spectral data, the complex undergoes reversible conformational (about the amide C−N bond) and irreversible allylic isomerization. Both conformers were isolated in the solid state by chromatography at a reduced temperature. The allylic isomerization occurs stereospecifically to produce the (μ-H)Os3{μ-OCN(Me)CH=CHMe}(CO)10 complex with thetrans-oriented olefinic hydrogen atoms.

Complexes of nickel(ii) and copper(ii) chlorides with a nitroxide radical derivative of 4-tetrazolyl-3-imidazolme-3-oxide

NiCl2 and CuCl2 complexes with a new stable nitroxyl radical, 2,2,5,5-tetramethyl-4-(tetrazol-5-yl)-3-imidazoline-3-oxide-1-oxyl (L), NiLCl2· H2O and CuLCl2, have been synthesized. The μeff values attest to a weak exchange interaction between the paramagnetic centers in the temperature interval of 78–300 K.