Synthesis, spectroscopic and thermal studies of the reactions of the donors piperazine and N,N′-dimethylpiperazine with σ- and π-acceptors

The interactions of the electron donors piperazine (PIP) and N,N′-dimethylpiperazine (DMPIP) with the σ-acceptor iodine and the π-acceptors tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were studied spectrophotometrically in chloroform at 25 °C. The electronic and infrared spectra of the resulting charge-transfer complexes were recorded, in addition to thermal analysis. The results obtained showed that the stoichiometries of the reactions are not fixed and depend on the nature of both the donor and the acceptor. The formed CT-complexes have the formulas of , [(PIP)(TCNE)₂], [(PIP)(DDQ)₂], , [(DMPIP)(TCNE)₂] and [(DMPIP)(DDQ)₂]. A general mechanism explaining the formation of triiodide complexes was suggested.     

Structural studies of new group 6 complexes of salicylidene-2-aminopyridine

Interaction of salicylidene-2-aminopyridine (Hsap) with [M(CO)₆], M = Cr, Mo and W, in THF under sunlight resulted in formation of dinuclear complexes [Cr₂O₄(sap)], 1, [Mo₂O₄(sap)], 2, and [W₂O₅(sap)₂], 3. Elemental analysis, spectroscopic and magnetic studies of the reported complexes revealed the proposed structures. Magnetic studies of 1 and 2 suggested that the two metal centers have +3 and +6 formal oxidation states, while the tungsten complex 3 has +6 formal oxidation state with d⁰ electron configuration. The thermal properties of the complexes were investigated by thermogravimetry.     

Synthesis,spectroscopic, thermal,crystal structure properties,and characterization of new Hofmann-Td-type complexes with 3-aminopyridine

In this study, synthesis of two new tetracyanocadmate(II) and tetracyanozincate(II) complexes based on 3-aminopyridine (3AP) and investigation of their structural properties were reported. These complexes were characterized by using vibration spectroscopy, elemental, thermal analysis and single crystal X-ray diffraction (SC-XRD) techniques. Investigation of the elemental, spectral and single crystal data of these complexes showed that the formulas [Cd(3AP)₂Zn(μ₄-CN)₄]_n (1) and [Cd(3AP)₂Cd(μ₄-CN)₄]_n (2) fully explained their crystal structure. General information about the structural and chemical properties of these complexes obtained in single crystal form was obtained by observing the changes in the characteristic peaks of the 3AP with the [Zn(μ₄-CN)₄]^2- and [Cd(μ₄-CN)₄]^2- structures that make up these complexes. The behaviors of these complexes against changes in temperature were obtained by examining the temperature-dependent changes of their mass. The asymmetric unit of the heterometallic complexes 1 and 2 consist of half Cd(II) ion, half M ion [M = Zn1 in 1 and Cd2 in 2], two cyanide ligands and one 3AP.     

Synthesis,spectroscopic and the biological activity studies of thiosemicarbazones containing ferrocene and their copper(II) complexes

Two Schiff bases, 1-acetylferrocene thiosemicarbazone (HL¹) and 1,1′-diacetyl-ferrocene dithiosemicarbazone (H₂L²) and their copper(II) complexes were prepared and characterized by elemental analysis, magnetic susceptibility, conductivity, and spectral (IR, UV–Vis, ESR) measurements The IR spectra showed that HL¹ acts as neutral or monobasic bidentate ligand, coordinating to copper(II) through either thiono- or thiolo-sulphur and azomethine-N atoms, whereas H₂L² is a neutral or dibasic mononucleating or binucleating quadridentate ligand coordinating through the same atoms. Other spectral measurements indicate that complexes [(L¹)₂Cu], [(L²)Cu] and [(HL¹)₂Cu]X₂, X?=?Cl, Br or ClO₄ have square-planar geometry around copper(II) while [(HL¹)CuX₂] and [(H₂L²)Cu₂X₄], X?=?Cl or Br, have distorted tetrahedral geometry. The biological activity studies of the complexes and the free ligands towards two gram positive and two gram negative bacteria and one fungal species have been studied and the potential is related to the nature and structure of the tested compounds.     

3-氯-2-氯甲基丙烯的合成

以季戊四醇为原料合成了3-氯-2-氯甲基丙烯,其结构经IR和1H NMR确认,总收率达45％,。     

Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives are formed on reaction between acetophenone, salicylaldehyde, benzophenone and/or 2-hydroxy-4-methoxybenzophenone and thiosemicarbazide or its N⁴H substituents (ethyl-, phenyl-, and p-chlorophenyl-). The ligands were investigated by elemental analysis and spectral (IR, ¹H?NMR and MS) studies. The formulas of the prepared complexes have been suggested by elemental analyses and confirmed by mass spectra. The coordination sites of each ligand were elucidated using IR spectra revealing bidentate and tridentate coordination. Different geometries for the complexes were proposed on the basis of electronic spectra and magnetic measurements. The complexes have been analyzed thermally (TG and DTG) and the kinetic parameters for some of their degradation steps were calculated.     

Novel 3d-metal complexes with 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole: Synthesis,spectroscopic and structural investigations

A series of new 3d-metal complexes have been prepared by the reaction of M(CH₃COO)₂ (M = Zn(II), Co(II), Ni(II)) and 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole (HL) in a methanol (3) or a methanol/dmf (1, 2) medium. All the complexes have been studied by elemental analyses, electronic and IR spectroscopies. The zinc(II) complex 1 and the ligand HL have been investigated using the method of ¹H NMR-spectroscopy at various temperatures. The disappearance of the signal from one proton of the amino group H(5) in the spectrum of complex 1 confirmed the existence of the ligand in the deprotonated form. According to the data of the ¹H NMR-spectroscopy, the ligand HL is coordinated to zinc(II) through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the benzothiazole substituent. These data are in agreement with X-ray structural studies for the ligand HL and the zinc(II) complex 1.     

Synthesis,structure and luminescence properties of new chalcogenide octahedral rhenium cluster complexes with 4-aminopyridine [{Re6Q8}(4-NH2-py)6]2+

Two new cationic octahedral rhenium cluster complexes [{Re₆Q₈}(4-NH₂-py)₆]²⁺ (Q=S, Se; 4-NH₂-py = 4-aminopyridine) were synthesized by reactions of cesium salts of cluster anions [{Re₆Q₈}Br₆]^4?/3? with molten 4-aminopyridine. Both complexes were separated as salts with Br^? as counterions and the structure of [{Re₆S₈}(4-NH₂-py)₆]Br₂·6DMF was revealed by X-ray single-crystal diffraction analysis. The compounds were characterized by elemental analysis, energy dispersive X-ray, IR, NMR, and luminescence spectroscopies.     

Crystal structure,spectroscopic and thermal studies of 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid sodium salt

The crystal structure, infrared spectrum and thermal stability of 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid sodium salt have been studied. The compound of general formula {[Na₂L₂?·?3H₂O]?·?H₂O} _n is a two-dimensional polymer, in which Na ions are bridged by one or two water molecules and additionally coordinated to oxygen atoms of carboxylate, hydroxy and methoxy groups. The structure is stabilized by a hydrogen bond network. The compound dehydrates at 75°C and then decomposes at 150°C. The IR spectra of the salt and free acid are discussed.     

Synthesis and spectroscopic studies of europium chelate complexes

The synthesis of the mixed complexes of the europium ion with 2-pyridylcarbinol-N-oxide, and 2,2′-dipyridyl and 1,10-phenanthroline were prepared. The compounds, were characterized by means of chemical analyses, vibrational spectra, molar conductivities, and electronic spectra. The emission of the [EuL₃, phen] complex at 10 K is very intense and an assignment of the point symmetry of the Eu(III) ion has been made.     

聚-2-氨基吡啶电化学合成及性质

报导了在 0.43 mol•dm－3 C6H6N2和0.01 mol•dm－3 NaOH中用循环伏安法合成聚-2-氨基吡啶. 聚-2-氨基吡啶在1.0 mol•dm－3 ZnCl2(pH=4.99)溶液中的循环伏安图上有三对氧化-还原峰.旋转环-盘实验的结果表明,在 2-氨基吡啶聚合的初期有中间体生成.由红外光谱可知，聚-2-氨基吡啶具有头-尾相接的结构.聚-2-氨基吡啶平均粒子大小约893 nm， 平均粒子间距约 255 nm. 由聚-2-氨基吡啶正极和锌负极及2.5 mol•dm－3 ZnCl2溶液和 3.0 mol•dm－3 NH4Cl (pH=5.5) 溶液构成的电池，其放电曲线类似于Li-SOCl2, 放电曲线的中间区域非常平稳.     

Synthesis and spectroscopic studies of charge transfer complex between dihydroxy-p-benzoquinone and 4-dimethylaminopyridine in different solvents

Charge transfer (CT) complex formation between 4-dimethylaminopyridine (4-DMAP) as the electron donor and 2,5-dihydroxy-p-benzoquinone (DHBQ) as the π-electron acceptor has been investigated spectrophotometrically in methanol (MeOH), ethanol (EtOH) and acetonitrile (AN). The stoichiometry of the complex has been identified by Job’s and photometric titration methods to be 1:1. The Benesi–Hildebrand equation has been applied to estimate the formation constant (K_CT) and molecular extinction coefficient (ε). It was found that the value of K_CT is larger in AN than in MeOH and EtOH. The thermodynamic parameters are in agreement with the K_CT values in that the enthalpy of formation (?ΔH) has a larger value both in EtOH and MeOH than in AN, suggesting higher stability of the complex in EtOH. The complex formed between 4-DMAP and DHBQ has been isolated as a solid and characterised using elemental analysis, FTIR and ¹H NMR measurements. Moreover, it has been found that the formed complex involves proton transfer in addition to CT.     

Reactions of (E)-1,2-di(3-guaiazulenyl)ethylene and 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene with tetracyanoethylene (TCNE) in benzene: comparative studies on the products and their spectroscopic properties

Reactions of the title ethylene derivatives, (E)-1,2-di(3-guaiazulenyl)ethylene (1) and 2-(3-guaiazulenyl)-1,1-bis(4-methoxyphenyl)ethylene (2), with a 2 M amount of TCNE in benzene at 25 °C for 24 h under argon give new cycloaddition compounds, 1,1,2,2,11,11,12,12-octacyano-3-(3-guaiazulenyl)-8-isopropyl-5,10-dimethyl-1,2,3,6,9,10a-hexahydro-6,9-ethanobenz[a]azulene (3) from 1 and 1,1,2,2,11,11,12,12-octacyano-8-isopropyl-3,3-bis(4-methoxyphenyl)-5,10-dimethyl-1,2,3,6,9,10a-hexahydro-6,9-ethanobenz[a]-azulene (4) from 2, respectively, in 66 and 87% isolated yields. Comparative studies on the above reactions as well as the spectroscopic properties of the unique products 3 and 4, possessing interesting molecular structures, are reported and, further, a plausible reaction pathway for the formation of these products is described.     

Vibrational spectroscopic and thermal studies of some 3-phenylpropylamine complexes

Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)₂Ni(CN)₄ (M = Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60 cm⁻¹. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)₄|_∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes.     

Kinetics of formation of charge transfer complexes of poly(vinyl pyridines) with iodine, 7,7′8,8′-tetracyanoquinodimethane and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone by electronic spectroscopic studies

The kinetics of formation of charge transfer complexes of poly(4-vinyl pyridine), poly(2-vinyl pyridine), and poly(2-vinyl pyridine-co-styrene) with iodine, 7,7′,8,8′-tetracyanoquinodimethane and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone has been studied using electronic absorption spectroscopy. The charge transfer complexes of analogous low molecular weight donors, namely 2- and 4-picolines with the same set of acceptors have also been investigated for comparison. The composition and the equilibrium constants of the charge transfer complexes have been obtained. The equilibrium constant of the polymeric complexes is found to be higher than that of analogous complexes of the low molecular weight donors. A new method for determining the rate constants of the association and dissociation of the equilibrium involving the charge transfer complex formation has been proposed. The rate constants vary with the concentration of the acceptor. It indicates that the charge transfer complexes undergo a further reaction and hence the observed rate constants are not true but apparent rate constants. The charge transfer complexes have also been investigated by electron paramagnetic resonance spectroscopy.     

Synthesis and spectroscopic properties of platinum(II) terpyridine complexes having an arylborane charge transfer unit

Synthesis, redox, spectroscopic, and photophysical properties of a new class of Pt(II) complexes of the type [PtLnCl]+ are reported, where Ln is 4'-phenyl(dimesitylboryl)-2,2':6',2"-terpyridine (L1) or 4'-duryl(dimesitylboryl)-2,2':6',2"-terpyridine (L2). The free L1 or L2 ligand in CH3CN shows the absorption band responsible for intramolecular charge transfer (CT) from the pi-orbital of the aryl group in L1 or L2 (pi(aryl)) to the vacant p-orbital on the boron atom (p(B)), in addition to pipi* absorption in the 2,2':6',2"-terpyridine (tpy) unit. In particular, the L1 ligand shows an intense CT absorption band as compared with L2. Such intramolecular pi(aryl)-p(B) CT interactions in L1 give rise to large influences on the redox, spectroscopic, and photophysical properties of [PtL1Cl]+. In practice, [PtL1Cl]+ shows strong room-temperature emission in CHCl3 with the quantum yield and lifetime of 0.011 and 0.6 micros, respectively, which has been explained by synergetic effects of Pt(II)-to-L1 MLCT and pi(aryl)-p(B) CT interactions on the electronic structures of the complex. In the case of [PtL2Cl]+, the dihedral angle between the planes produced by the tpy and duryl(dimesitylborane) groups is very large (84 degrees ) as compared with that between the tpy and phenyl(dimesitylborane) units in [PtL1Cl]+ (26-39 degrees ), which disturbs electron communication between the Pt(II)-tpy and arylborane units in [PtL2Cl]+. Thus, [PtL2Cl]+ is nonemissive at room temperature. The important roles of the synergetic CT interactions in the excited-state properties of the [PtL1Cl]+ complex are shown clearly by emission quenching of the complex by a fluoride ion. The X-ray crystal structure of [PtL1Cl]+ is also reported.     

Quantum-chemical and spectroscopic studies of structures of 1 : 2 complexes of carbonyl compounds with aluminum halides

Quantum-chemical calculations of model systems, namely, benzaldehyde and its 1 : 1 and 1 : 2 complexes with AlCl₃, were carried out by the MNDO method. In the 1 : 2 complex, a bridging Al-Cl-Al bond occurs. Apparently, this complex is stabilized through the Coulomb interaction between the positively charged C atom of the carbonyl group and the AlCl₃ fragment, which carries an excessive negative charge and which is not involved in donor-acceptor bonding with the carbonyl O atom. The IR spectra of the 1 : 1 and 1 : 2 complexes of benzophenone with AlBr₃ were recorded, and the differences in the low-frequency regions of these spectra, which are indicative of the presence of the Br₂Al-Br-AlBr₃ fragment in the 1 : 2 complex, are discussed.This article is dedicated to Academician M. G. Voronkov on the occasion of his 75th birthday.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2866–2871, December, 1996.     

Spectro- and electrochemical studies of some ruthenium and osmium complexes of 2-(2'-pyridyl)benzimidazole; complexes with intra-molecular charge transfer

Reaction of Ru3(CO)12, with 2-(2'-pyridyl)benzimidazole (HPBI) resulted in the formation of Ru(CO)3(HPBI) (I) complex. In presence of pyridine or dipyridine, the two derivatives [Ru(CO)3(HPBI)].Py (II) and [Ru(CO)3(HPBI)].dpy (III) were isolated. The corresponding reactions of Os3(CO)12 yielded only one single product; Os(CO)2(HPBI)2 (IV). Spectroscopic studies of these complexes revealed intramolecular metal to ligand CT interactions. Reactions of RuCl3 with HPBI gave three distinct products; [Ru(HPBI)2Cl2]Cl (V), [Ru(HPBI)(dipy)Cl2]C1 (VI) and [Ru(PBI)2(py)2]Cl (VII). The UV-vis studies indicated the presence of intramolecular ligand to metal CT interactions. Electrochemical investigation of the complexes showed some irreversible, reversible and quasi-reversible redox reactions due to tautomeric interconversions through electron transfer.