Further studies on the properties and effect of high energetic ionizing radiation on copper(II) complexes: 1H NMR,electronic absorption,ESR spectra and solid electrical conductivity

The effect of energetic γ-radiation on ¹H NMR, electronic absorption, ESR spectra, differential thermal analysis (DTA) and solid state dc electrical conductivity of the ligand N-phenyl-2-(2-(phenylamino)acetyl)hydrazine carbothioamide (H₂L) and its copper(II) complexes; Cu(HL)(OAc)H₂O, Cu(HL)BrH₂O and Cu(H₂L)₂(NO₃)₂?3H₂O before and after γ-irradiation (hereafter referred to as (B), (B ₁ ), (B ₂ ), (B ₃ ) and (A), (A ₁ ), (A ₂ ), (A ₃ ), respectively) has been studied. Electronic spectral bands of the complexes after irradiation exhibited some better resolved shapes with a remarkably higher absorbance, ESR spectrum of complex Cu(HL)BrH₂O (B ₂ ) before irradiation showed isotropic spectrum with g _iso = 2.075 however, after irradiation (A ₂ ) displayed axial ESR spectrum with g _∥ > g _⊥ > 2.0023 and d _(x2?y2) ground state. DTA of the compounds reveals that γ-irradiation induced generation of new peaks as well as changes in the peak intensities. Solid state dc electrical conductivity for complexes was investigated before and after γ-irradiation. Complexes were found to be semiconductors, the activation energies (E _a) were calculated for the complexes by using the Arrhenius plot.     

Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid?Cbase equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(??⁶-p-cymene)Ru (L^1?3)Cl₂] where L¹?=?3-acetylpyridine (1), L²?=?4-acetylpyridine (2) and L³?=?2-amino-5-chloropyridine (3), then [(??⁶-p-cymene)Ru(HL⁴)Cl₂] with HL⁴?=?isonicotinic acid (4); [(??⁶-p-cymene)Ru(HL^5?8)Cl] where H₂L⁵?=?2,3-pyridine dicarboxylic acid (5), H₂L⁶?=?2,4-pyridine dicarboxylic acid (6), H₂L⁷?=?2,5-pyridine dicarboxylic acid (7) and H₂L⁸?=?2,6-pyridine dicarboxylic acid (8) have been studied. pK _a values were determined by potentiometry at 25?°C and constant ionic strength of 0.1?M NaNO₃. The assumed equilibria were confirmed by UV and ¹H-NMR spectroscopy.     

Synthesis and properties of ZnII and CdII complexes with chiral N-derivatives of aminoacetic acid based on natural monoterpenes (+)-3-carene and (?)-��-pinene. Crystal structure of coordination polymer [Zn(HL)Cl��2H2O] n

Chiral sodium salts of N-derivatives of aminoacetic acid based on (+)-3-carene (HLNa) and (?)-??-pinene (HLNa) were synthesized. Complexes Zn(HL)Cl (1), Cd(HL)Cl·0.5H₂O (3), Zn(HL??)Cl·0.5H₂O (4), and Cd(HL??)Cl·0.5H₂O (5) were obtained. The single crystals of the coordination polymer [Zn(HL)Cl·2H₂O] _n (2) were grown. According to the X-ray diffraction analysis, the crystal structure of 2 consists of 1D chains built of Zn(HL)Cl and water molecules. The coordination polyhedron ClN₂O₂ is a distorted square pyramid. The HL^? ligand performs the chelating tetradentate-bridging function, and the COO^? group binds two adjacent Zn atoms. The IR spectroscopy data for compounds 1 and 3?C5 indicate the coordination of the COO^?, NOH, and NH functional groups. The excitation and photoluminescence (PLM) spectra of the solid samples of compounds HLNa, HL??Na, 1, and 3?C5 were recorded at room temperature. The compounds exhibit blue PLM. The intensity of PLM of the CdII complexes is higher than that of the ZnII complexes, which is a characteristic feature of PLM of the studied compounds.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

Characterization, crystal structures and solution studies of Zn(II), Cd(II) and Mg(II) complexes obtained from a proton transfer compound including pyridine-2-carboxylic acid and piperazine

The three complexes [Zn(pyc)₂(H₂O)₂]·H₂O (1), (pipH₂)[Cd(pyc)₃]·3H₂O (2) and [Mg(pyc)₂(H₂O)₂]·H₂O (3) (pycH: pyridine-2-carboxylic acid, pip: piperazine) were prepared using a proton transfer compound (pipH₂)(pyc)₂ and corresponding metallic salts. The characterization was carried out using IR and NMR spectroscopies and single crystal X-ray diffraction. These complexes crystallize in the space group P2₁/n of the monoclinic system. Cell parameters of the complexes are a?=?9.769(2)?, b?=?5.157(1)?, c?=?14.539(3)? and ???=?90.205(3)° for (1); a?=?8.436(2)?, b?=?14.616(4)?, c?=?19.050(6)? and ???=?96.830(5)° for (2); a?=?11.639(6)?, b?=?8.796(5)?, c?=?14.936(8)? and ???=?107.221(1)° for (3). The crystal structures of (1) and (3) complexes illustrate that the metal ions are coordinated by two pyridine-2-carboxylate but in crystal structure (2) the metal ion is coordinated by three pyridine-2-carboxylate. The protonation constants of the building blocks of the pyridine-2-carboxylic acid?Cpiperazine adduct and the equilibrium constants for the reaction of pyridine-2-carboxylate with piperazine and the stoichiometry and stability of the Zn²⁺, Cd²⁺ and Mg²⁺ complexes with pycH in aqueous solution were accomplished by potentiometric pH titration. The corresponding stability constants, stoichiometry and distribution of the species were determined with program BEST. The solution studies strongly support the self-association and stoichiometry similar to that observed for the isolated crystalline complexes.     

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

Synthesis and molecular and crystal structures of binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione

Binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione (C₁₁H₂₀N₄O₂, SC)—[Sm(NO₃)₃(SC)(H₂O)]₂(I), [Eu(NO₃)₃(SC)(H₂O)]₂ (II), [Gd(NO₃)₂(SC)(H₂O)₃)]₂(NO₃)₂ (III), [Tb(NO₃)₃(SC)(H₂O)]₂ (IV), [Dy(NO₃)₃(SC)(H₂O)]₂ (V), are synthesized, and their X-ray diffraction analyses are carried out. The crystals of complexes I–V are monoclinic: space group P2₁/n for III and P2₁/c for I, II, IV, and V. In centrosymmetric coordination complexes II, III, IV, and V, the Ln atoms are coordinated by two O(1) and O(2) atoms of two molecules of the SC ligands bound by a symmetry procedure (1 ? x, ?y, 1 ? z), three bidentate nitrate anions, and a water molecule. The coordination numbers of the metal atoms are equal to 9, and the coordination polyhedra are considerably distorted three-capped trigonal prisms, whose bases include the O(1), O(2), O(12) and O(3), O(7), O(9) atoms. The dihedral angle between the bases of the prism is 18°, and that between the mean planes of the side faces is 55°–71° for I, 17° and 55°–71° for II, 16° and 55°–70° for IV, and 16° and 55°–70° for V. The Sm...Sm distance in complex I is 9.44 Å, Eu...Eu in II is 9.42 Å, Tb...Tb in IV is 9.36Å, and Dy...Dy in V is 9.36Å. The gadolinium atom in complex III is coordinated by two oxygen atoms of two ligand molecules bound by a symmetry procedure (?x, ?y + 1, ?z + 1), two bidentate nitrate anions, and three water molecules. One of the nitro groups in compound III is localized in the external coordination sphere of the metal. The coordination number of gadolinium is 9, and the coordination polyhedron is a significantly distorted three-capped trigonal prism, whose base includes the O(1), O(2), O(7) and O(4), O(5), O(9) atoms. The dihedral angle between the bases of the prism is 22.8°, and that between the mean planes of the side faces is 53°–72°. The Gd...Gd distance in complex III is 9.17 Å.     

Dinuclear nickel(II) complexes with Schiff base ligands: syntheses, structures and bio-relevant catalytic activities

Three Ni(II) complexes of cresol-based Schiff-base ligands, namely [Ni₂(L¹)(NCS)₃(H₂O)₂], (1) [Ni₂(L²)(CH₃COO)(NCS)₂(H₂O)] (2) and [Ni₂(L³)(NCS)₃] (3), (where L¹ = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L² = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L³ = 2,6-bis{N-ethyl-N-(3-hydroxypropyl iminomethyl)}-4-methylphenolato), have been synthesized and structurally characterized by X-ray single-crystal diffraction in addition to routine physicochemical techniques. Density functional theory calculations have been performed to understand the nature of the electronic spectra of the complexes. Complexes 1?C3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile?Cwater medium promote the cleavage of the O?CP bond to form p-nitrophenol and smoothly convert 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) either in MeOH or in MeCN medium. Phosphatase- and catecholase-like activities were monitored by UV?Cvis spectrophotometry and the Michaelis?CMenten equation was applied to rationalize all the kinetic parameters. Upon treatment with urea, complexes 1 and 2 give rise to [Ni₂(L¹)(NCS)₂(NCO)(H₂O)₂] (1??) and [Ni₂(L²)(CH₃COO)(NCO)(NCS)(H₂O)] (2??) derivatives, respectively, whereas 3 remains unaltered under same reaction conditions.     

Synthesis, structures, and photoluminescence of heteroligand complexes Ln(L)(iso-Bu2PS2)2(NO3) (Ln = Sm, Tb, Dy; L = Phen, 2,2′-Bipy)

Heteroligand complexes Ln(L)(iso-Bu₂PS₂)₂(NO₃) (Ln = Sm, Tb, Dy; L = Phen, 2,2??-Bipy) (I?CVI) are synthesized. The structure of Dy(Phen)(iso-Bu₂PS₂)₂(NO₃) (III) is determined from the data of X-ray structure analysis. The crystal structure of complex III is based on discrete mononuclear molecules in which the Dy atom has distorted dodecahedral coordination (polyhedron N₂O₂S₄). The ligands Phen, iso-Bu₂PS ₂ ^? and NO ₃ ^? are bidentate-cyclic. According to the X-ray diffraction analysis data, complexes I and II are isostructural to compound III. Complexes I?CVI have photoluminescence in the visible spectral range. The photoluminescence spectra of solid samples of compounds I?CVI exhibit bands corresponding to the radiative electron transitions of the Sm³⁺, Tb³⁺, and Dy³⁺ ions. Among the studied compounds I?CVI, the Tb(III) complexes are characterized by the most intense photoluminescence.     

Syntheses and X-ray structures of some pyrrolylaldiminate metal complexes

Several pyrrolylaldiminate complexes of Group 1, 4 and 13 metals are reported. The reaction of 5-tert-butyl-2-[(2,6-diisopropylphenyl)aldimino]pyrrole (HL) with NaH produced LNa(THF) (1). In situ lithiation of HL followed by addition of one equivalent of MCl_x (M=Zr, x=4; M=Hf, x=4, M=Al, x=3) afforded the corresponding pyrrolylaldiminate complexes, MLCl₂(μ-Cl)₂Li(OEt₂)₂ (M=Zr, 3; Hf, 4) and AlLCl₂ (5). Alkylation of 5 with MeMgBr generated AlLMe₂ (6). In addition to the spectroscopic data, complexes 3-6 were characterized by X-ray crystallography.     

Synthesis and characterization of palladium(II) complexes [PdX2(p-diben)] (X = Cl,Br, I,N3, or NCO; p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine): crystal structure of [Pd(N3)2(p-diben)]

Five new complexes of general formula [PdX₂(p-diben)], where p-diben = N,N′-bis(4-dimethylaminobenzylidene)ethane-1,2-diamine) (1) and X = Cl (2), Br (3), I (4), N₃ (5), or CNO (6), were synthesized and characterized by physicochemical and spectroscopic methods. The crystal structure of compound (5) was determined by single-crystal X-ray diffraction. Complexes 2–6 were characterized as N,N-chelated products. The crystal structure confirmed this formulation for [Pd(N₃)₂(p-diben)], besides showing the isomerism inversion of one of the C=N bonds, caused by Pd(II) coordination.     

fac-Cobalt(III)-azido complexes derived from substituted pyridyl-based tridentate amines

Four new mononuclear triazido-cobalt(III) complexes [Co(L ^1/2/4 )(N₃)₃] and [Co(L ³ )(N₃)₃]·CH₃CN where L ¹  = [(2-pyridyl)-2-ethyl]-(2-pyridylmethyl)-N-methylamine, L ²  = [(2-pyridyl)-2-ethyl]-[6-methyl-(2-pyridylmethyl)]-N-methylamine, L ³  = [(2-pyridyl)-2-ethyl]-[3,5-dimethyl-4-methoxy-(2-pyridylmethyl)]-N-methylamine, and L ⁴  = [(2-pyridyl)-2-ethyl]-[3,4-dimethoxy-(2-pyridylmethyl)]-N-methylamine, respectively, were synthesized and structurally characterized. The four complexes were characterized by elemental microanalyses, IR and UV–VIS spectroscopy and X-ray single crystal crystallography. The complexes display two strong IR bands over the frequency region 2,020–2,050 cm^?1 assigned for the asymmetric stretching frequency, ν_a(N₃) of the coordinated azides indicating facial geometry. The molecular structure determinations of the complexes were in complete agreement with fac-[Co(L)(N₃)₃] conformation in distorted octahedral Co(III) environment.     

On the stability of single-walled carbon nanotubes and their binding strengths

The series of rhenium (I) tricarbonyl mixed-ligand complexes ReCl(CO)₃(H_nbpydt) (n?=?2, 1; n?=?4, 2; bpy?=?bispyridine, dt?=?1,3-dithiole) and ReCl(CO)₃(H_nbpyTTF) (n?=?2, 3; n?=?3, 4; TTF?=?Tetrathiafulvalene) have been investigated theoretically to explore the effect of COOH functional group on their electronic structures, spectroscopic properties and their properties as dye in a solar cell. The calculated geometry structure and absorption spectrum of 1 and 3 are generally consistent with the experimental results. By attaching the COOH groups on both bpy and dt (TTF in 4) moiety in 2, the nature of LUMO is also contributed by both π*(bpy) and π*(dt) (π*(TTF) in 4), and the absorptions have an obvious red shift compared with 1 and 3. In addition, it can be found that the transition terminates at the orbital populated by the COOH-appended moieties, and the performance of 2 and 4 in the dye-sensitized solar cell can be enhanced as compared with 1 and 3.     

Kinetics of hydrolysis of the geminal alkoxy-NNO-azoxy compounds in sulfuric acid

The kinetics of hydrolysis of two alkoxy-NNO-azoxy compounds with geminal position of N₂O₂ groups, di(methoxy-NNO-azoxy)methane (I) and di(methyl-NON-azoxy)formal (II), as well as isomeric geminal nitramine, 2,4-dinitro-2,4-diazapentane (III) in 64.16% H₂SO₄ were studied by a manometric method. The relative rates of the hydrolysis at 80°C of compounds I?CIII and methoxy-NNO-azoxymethane (IV) were found to be equal to 4.2:77:??50000:1. The limiting stage of hydrolysis of compound I is the attack of the nucleophile on the carbon atom of the MeO group of the protonated molecule I by S _N2 mechanism. According to the parameters of the Arrhenius equation the hydrolysis of compound II proceeds more probably by the S _N1     

New N-nicotinyl and N-isonicotinyl, N′,N″-diaryl phosphorictriamides with new Er(III) complex: synthesis, spectroscopic study and crystal structures

Ten new N-nicotinyl and N-isonicotinyl phosphoramidates with formula XP(O)R₂, X?=?Nicotinamide(nia), R?=?NHCH₂Ph (1), N(CH₃)CH₂Ph (2), NHCH(CH₃)Ph (3), NH-CH₂C₄H₃O (4), NHCH₂(C₅H₄N) (5), 3-NH-C₅H₄N (6), and YP(O)R₂, Y?=?isonicotinamide(iso), R?=?NHCH₂Ph (7), N(CH₃)CH₂Ph (8), NHCH(CH₃)Ph (9), NH-CH₂C₄H₃O (10) plus one new Er(III) complex with formula Er(L)₂(NO₃)₃ (11), L?=?(iso)PO(NHCH₂C₄H₃O)₂ (10), were synthesized and characterized by elemental analysis and ¹H, ¹³C, ³¹P NMR, IR, UV?Cvis spectroscopy. Crystal structures of compounds 10 and 11 were also determined by X-ray crystallography. Interestingly, the ¹H NMR spectra of compounds 1, 2, 6, 7, 9 indicated long-range ⁿ J _P,H (n?=?5,6,7) coupling constants, in the range of 1.4?C1.9?Hz, for the splitting of pyridine ring protons with phosphorus atom. IR results showed that the ??(C=O) values of compounds 7?C10 are greater than those of compounds 1?C5 which means that isonicotinyl moiety is more electron withdrawing than nicotinyl group. X-ray outcomes revealed that in complex 11 three phosphoric triamide ligands have been connected to each Er(III); one from N_pyridine and two from P=O donor sites. One of the P=O donor ligands is mono dentate while the other one acts as a bidentate ligand and coordinates to another Er atom via its N_pyridine site. By forming complex 11 the P=O and C?CN_amide bond lengths of ligand is increased in both, mono and bi dentate, ligands while the C=O bond length is decreased to lower values. These variations are in good agreement with IR results. All H-bonds and electrostatic interactions lead to form a three-dimensional polymeric cluster in the crystal lattice of 10 and 11.     

Synthesis,crystal structure,and electrochemical properties of Ni(II) and Cu(II) complexes with two unsymmetrical N2O2 Schiff base ligands

Nickel(II) and copper(II) complexes of two unsymmetrical tetradentate Schiff base ligands [Ni(Me-salabza)] (1), [Cu(Me-salabza)] (2) and [Ni(salabza)] (3), {H₂salabza = N,N′-bis[(salicylidene)-2-aminobenzylamine] and H₂Me-salabza = N,N′-bis[(methylsalicylidene)-2-aminobenzylamine]}, have been synthesized and characterized by elemental analysis and spectroscopic methods. The crystal structures of 2 and 3 complexes have been determined by single crystal X-ray diffraction. Both copper(II) and nickel(II) ions adopt a distorted square planar geometry in [Cu(Me-salabza)] and [Ni(salabza)] complexes. The cyclic voltammetric studies of these complexes in dichloromethane indicate the electronic effects of the methyl groups on redox potential.     

Imidazole,pyrimidine and diazepine containing heteroaryl-substituted heterocyclic salts as efficient ligand precursors for Mizoroki–Heck coupling reaction: synthesis,structural characterization and catalytic activities

The nine new heteroaryl-substituted imidazolidinium (1a–c), pyrimidinium (2a–c) and diazepinium (3a–c) salts as N-heterocyclic carbene (NHC) precursors were synthesized in good yields and entirely characterized using elemental analyses and conventional spectroscopic methods. In situ formed complexes from heterocyclic salts (1–3), Pd(OAc)₂ and in the presence of KOBu ^t as a base were tested as catalysts for the Mizoroki–Heck coupling reaction in an aqueous media and very high yields were achieved. 1,3-Di(5-methylthiophen-2-ylmethyl)pyrimidinium hexafluorophosphate salt (2b) was structurally characterized by single-crystal X-ray diffraction. In the 2b compound (C₁₆H₂₁N₂S₂)⁺[PF₆]^?, the terminal thiophene rings are twisted with a dihedral angle of 72.8(3)°. In the pyrimidine ring, the three successive C atoms between the N atoms are disordered over two positions [occupancy ratio 0.753(12):0.247(12)]. In the crystal, neighboring molecules are linked by C–H…F hydrogen bonds, running along the b axis.     

Ferromagnetic interactions in EO-azido-bridged binuclear transition metal(II) systems: Syntheses, crystal structures and magnetostructural correlations

Three new isostructural binuclear transition metal complexes with azido ion and 1,2-bis(3-(pyridin-2-yl)-1H-pyrazol-1-yl)ethane (bppe), formulated as [M 2 (N 3 ) 2 (bppe) 2 ](ClO 4 ) 2 (M = Co, 1; Ni, 2; Cu, 3), were successfully synthesized. They were structurally and magnetically characterized. In 1-3, the double azido ions link two adjacent octahedral metal centers together in the end-to-on mode (EO), with the M-N EO -M angles of 99.41°, 100.24° and 99.80°, respectively. The co-ligand bppe acts as terminal ligand to saturate the remaining coordination sites. The magnetic properties of 1-3 have been investigated in the temperature range of 2-300 K. Fitting of the magnetic susceptibility data revealed the occurrence of the strong ferromagnetic interactions [J = 26.32 cm-1 (1), J = 38.23 cm-1 (2) and J = 139.83 cm-1 (3)]. Density functional theory calculations have been performed on 1-3 to provide a magneto-structural correlation of the ferromagnetic behavior.     

Magnesium sulphate complexes with hexamethylenetetramine and 1,10-phenanthroline

The magnesium sulphate complex compounds of general formulae [Mg(H₂O)₆]²⁺·2(C₆H₁₂N₄)·SO₄ ^2?·5(H₂O) (1) and Mg(C₁₂H₈N₂)(H₂O)₃SO₄ (2) have been synthesized, characterised by elemental and thermal analysis, IR, UV?CVIS and fluorescence spectroscopy, and X-ray crystallography. The obtained compounds are air stable at room temperature and well soluble in water. In the structures of the investigated complex compounds the O?CH?O, O?CH?N, and C?CH?O hydrogen bonds exist, and they create N₂C ₂ ² (8), R ₂ ² (8) (compound 1) and N₁C ₁ ¹ (6), N₁R ₂ ² (12) (compound 2) patterns. Their thermal decomposition processes in the investigated atmospheres (air and helium) are different. After the slightly similar dehydratation, the observed transitions and the obtained final products are different (in helium atmosphere the sulphate ion of studied compounds undergoes decomposing what does not take place in air atmosphere). The UV?CVIS spectrum of 2 shows maxima that are typical for ????????* and n??????* transitions, and fluorescence spectrum of the same compound displays its great fluoresce properties. The 1 does not exhibit absorption in the investigated region of electromagnetic spectrum due to the absence of respect chromophore groups. The IR spectrum of 2 shows typical vibrations for chelating amine molecule. An interesting fact is that in 1 the SO stretching vibrations (existing at 1119 and 1182?cm^?1) are doubled in comparison to the magnesium sulphate whilst in 2 these vibrations are absent.     

Thermal behavior of manganese(II) complexes with pyridine-2,3-dicarboxylic acid

In this study, we analyzed influence of the type of the syntheses used: hydrothermal and non-hydrothermal on pyridine-2,3-dicarboxylic acid (2,3pydcH₂) coordination fashion. Two manganese(II) complexes: [Mn(H₂O)₃(2,3pydc)] _n (1) and [Mn(H₂O)₆][Mn(2,3pydcH)₃]₂ (2) were successfully synthesized from the non-hydrothermal reaction system containing organic ligand and different Mn(II) salts. The received complexes have been prepared and characterized by spectroscopic (IR, Raman), structural (X-ray single crystal), and thermogravimetric methods. The results of the crystal study give some evidence that ligand exhibits various topological structures and interesting properties. Pyridine-2,3-dicarboxylic acid acts as monodicarboxylate N,O-chelating anion (complex 2) or a doubly deprotonated three-dentate-N,O,O?? dicarboxylate ion (complex 1). In the [Mn(H₂O)₆][Mn(2,3pydcH)₃]₂ the coordination geometry around Mn(1) ion can be considered as being distorted octahedron {MnN₃O₃}. The Mn(2) cation possesses the same coordination polyhedron (octahedral). We have also analyzed influence of furnace atmosphere on the thermal behavior and the kind of final product. The sample of (1) decomposes in four stages in N₂ (368?C1073?K) and the final residue is MnO₂. The thermogram of (2) exhibits three main distinct decomposition steps (383?C973?K). A residue of MnO is remained. In both air and nitrogen atmosphere, Mn(II) complexes (1) and (2) keep unchanged over all steps of decomposition. Only the final residues are different (Mn₂O₃ are formed). The course of pyrolysis and molecular structure of the complexes lead to the same conclusion about the strength of metal?Cligand bonds. On the basis of the above results, it is concluded that the thermal stability of the manganese(II) compounds is slightly different.