M. I. Rakhmanova

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

Luminescent CuI thiocyanate complexes based on tris(2-pyridyl)phosphine and its oxide: from mono-, di- and trinuclear species to coordination polymers

Tris(2-pyridyl)phosphine oxide reacts with CuSCN to form a variety of luminescent complexes, depending on the specified metal-to-ligand ratio and the solvent used, viz. mononuclear [Cu(N,N′,N′′-Py3PO)(NCS)], dinuclear (N,N′-Py3PO)Cu(SCNNCS)Cu[(N,N′-Py3PO)], their co-crystal (2:1, correspondingly) and trinuclear {Cu(NCS)[SCNCu(N,N′,N′′-Py3PO)]2}. In the solid state, these complexes feature red-orange emission upon UV photoexcitation. The reaction of tris(2-pyridyl)phosphine with CuSCN quantitatively produces an almost insoluble coordination polymer, [Cu(Py3P)NCS]n, which exhibits bright green emission. The synthesized compounds are the first members of the hitherto unknown family of Cu(I) thiocyanate complexes supported by tripodal ligands.

Structure of [Dy(Phen)(C4H8NCS2)3]·3CH2Cl2 solvate. Magnetic properties and photoluminiscence of [Ln(Phen)(C4H8NCS2)3] (Ln = Sm, Eu, Tb, Dy, Tm) complexes

It is found that diffraction patterns of complexes I–V of the composition [Ln(Phen)(C4H8NCS2)3] (Ln = Sm, Eu, Tb, Dy, and Tm respectively) are similar. Single crystals of [Dy(Phen)(C4H8NCS2)3]·3CH2Cl2 (VI) obtained are. According to the X-ray crystallographic data, in the structure of VI the unit cell contains two crystallographically independent molecules of the [Dy(Phen)(C4H8NCS2)3] complex and six CH2Cl2 molecules. The N2S6 coordination polyhedron of the Dy atom is a distorted square antiprism. In the range of 2–300 K the magnetic properties of complexes I–V are studied. It is found that complex III passes to the magnetically ordered state; the spontaneous magnetization at 2 K is 24 600 G·cm3/mol. At 300 K compounds I–IV exhibit photoluminescence in the visible spectral range. It is found that the photoluminescence intensity of complex I is several times higher than the photoluminescence intensity of complexes II–IV.

Luminescent zinc(II) and cadmium(II) complexes based on 2-(4,5-dimethyl-1H-imidazol-2-yl)pyridine and 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine

Complexes ZnL1Cl2, CdL1Cl2, ZnL21Cl2·1.5H2O, CdL21Cl2·2H2O, CdL21Cl2·MeOH·H2O [L1 = 2-(4,5-dimethyl-1H-imidazol-2-yl)pyridine] and inner-complex compounds ZnL22·2H2O, CdL22 [HL2 = 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine] were synthesized. The complexes exhibit bright photoluminescence in the blue region of the spectrum, with the intensity exceeding this characteristic of the compounds L1 and HL2. Compound L1 in aqueous solution is a potential chemosensor for the determination of zinc and cadmium.

Copper(II) and silver(I) complexes with chiral N-substituted aminoacetic acid derivatives containing the natural monoterpenes (+)-3-carene and (–)-α-pinene: Synthesis and structures

The complexes [Cu(HL)Cl] · 0.25H2O (I), [Cu(HL1)Cl] · 0.5H2O (II), [Ag(HL)] · 0.5H2O (III) were obtained; HL– and (HL1)– are the anions of the chiral N-substituted aminoacetic acid derivatives containing the natural monoterpenes (+)-3-carene and (–)-α-pinene, respectively. The µeff values for paramagnetic complexes I and II are 1.92 and 1.81 µB, respectively. Single crystals of the coordination 1D polymer [Cu(HL)Cl · 2H2O]n (IV) were grown. According to the X-ray diffraction data (CIF file CCDC No. 1035219), the crystal structure of complex IV is made up of the zigzag chains [Cu(HL)Cl]n and water molecules. The coordination polyhedron of the Cu atom is a distorted square pyramid (ClN2O2). The anion HL– acts as a chelating and bridging tetradentate ligand coordinated through the N atoms of the NH and NOH groups as well as through the O atoms of the COO–groups linking two adjacent Cu atoms together. The IR spectra of complexes I and II also provide evidence for the coordination of the functional COO–, NOH, and NH groups. In complex III, the coordination sphere of the Ag atom is made up of the O atoms of the COO–group. Complex III shows weak green photoluminescence (λmax = 530 nm).

The phase composition and physicochemical properties of transparent nanocomposite films of silicon oxycarbonitride

Films of hydrogenated SiCxNyOz:H obtained by plasma-enhanced chemical vapor deposition from a mixture of 1,1,3,3-tetramethyldisilazane with oxygen and nitrogen (TMDS+ O2+xN2) in the temperature range 373-973 K are nanocomposites in whose amorphous part nanocrystals belonging to phases of the Si–C–N: α-Si3–xCxN4 system and graphite are distributed. A change in the chemical composition of gas mixtures enables the preparation of SiCxNyOz:H films with a broad variation range of functional properties, such as the 1.45-2.15 variation of the refractive index; the controlled transparency (T ~ 92-99.7%) in the UV, visible, and IR spectral ranges; tunable characteristics of the band gap (3.5-5.4 eV), and dielectric constants (5.2-5.8).

New red-luminescent cadmium coordination polymers with 4-amino-2,1,3-benzothiadiazole

Abstract New polymeric cadmium complexes, α-[CdLCl2]n (1), [CdL2Cl2]n (2) and β-[CdLCl2]n (3) (L = 4-amino-2,1,3-benzothiadiazole), were obtained as products of the reaction of CdCl2 with L. The synthetic procedures allowing isolation of pure 1–3 were optimized. The structures of 1–3 were established by single-crystal X-ray diffraction and the compounds were characterized by UV–Vis and IR spectroscopy. In these compounds, L is either μ-bridging (1) or terminal (2 and 3). The UV–Vis spectra of the complexes in the solid state resemble that of free L. However, coordination of L leads to a significant shift of emission in photoluminescence spectra from yellow (free L) to red (1–3).

Mechanism of Formation of Cadmium Sulfide Nanoparticles on Polystyrene Supports from Ammonia—Thiourea Solutions

The nucleation of CdS particles on the surface of polystyrene supports from aqueous ammonia—thiourea solutions was studied. The increment in the mass of nanoparticles on the support with time was determined. The degree of binding of Cd(II) ions into sulfide on the surface (support area 14 cm2, solution volume 3.7 cm3) after 3 h at 50°C was 2.2% of their total amount. The results agreed well with those of model calculations for spherical (for small times) and ellipsoid particles at a constant surface concentration. The nanoparticles that formed in solution were not involved in the formation of surface films on polystyrene supports. The photoluminescent properties of the obtained films were studied.

Syntheses, structures, magnetic properties, and photoluminescence of compounds Ln(2,2′-Bipy)(C4H8NCS2)3 · 0.5CH2Cl2 (Ln = Sm, Eu, Tb, Dy, and Tm)

Five compounds of the composition Ln(2,2′-Bipy)(C4H8NCS2)3 · 0.5CH2Cl2 (Ln = Sm (I), Eu (II), Tb (III), Dy (IV), and Tm (V); 2,2′-Bipy = 2,2′-bipyridine) are synthesized. According to the X-ray diffraction data (CIF file CCDC 986259), the crystal structure of compound I consists of molecules of the mononuclear complex [Sm(2,2′-Bipy)(C4H8NCS2)3] and solvate molecules CH2Cl2 (2 : 1). The coordination polyhedron N2S6 of the Sm atom is a distorted tetragonal antiprism. The X-ray diffraction analysis shows that compounds I–V are isostructural. The magnetic properties of compounds I–V are analyzed in the temperature range from 2 to 300 K. At 300 K compounds I and III are photoluminescent in the visible spectral range. The photoluminescence intensity of compound I considerably exceeds that of complex III.

Synthesis and photoluminescence of Eu(III) and Tb(III) complex compounds containing anions of 4-CF3C6F4COOH and 4-(CF3)2CFC6F4COOH acids

Hydrates of Eu(III) and Tb(III) salts with anions (L) 4-CF3C6F4COO− and 4-(CF3)2CFC6F4COO−, and also mixed-ligand complexes Ln(phen)(L)3 were obtained. The compounds show red and green photoluminescence characteristic of Eu3+ and Tb3+ ions, respectively, in the visible region of spectrum. The intensity of the photoluminescence of the complexes containing 1,10-phenanthroline is much higher than that of compounds containing water. It is connected with sensitizing properties of phen in relation to Eu3+ and Tb3+ ions.