Charge-transfer complexes of cobaltocene and nickelocene with tetrachloromethane

The photochemical properties of the systems cobaltocene—tetrachloromethane and nickelocene—tetrachloromethane in ethanol and cyclohexane were investigated; the equilibrium constants and molar extinction coefficients of the donor—acceptor complexes in these systems were determined.

---

Charge-Transfer Komplexe von Kobaltocen und Nickelocen mit Tetrachlorkohlenstoff

Zusammenfassung Es wurden die photochemischen Eigenschaften der Systeme Kobaltocen–CCl₄ und Nickelocen–CCl₄ in Ethanol und Cyclohexen als Lösungsmittel untersucht. Die Gleichgewichtskonstanten und die molaren Extinctionskoeffizienten der Donor—Acceptor-Komplexe in diesen Systemen wurden bestimmt.

     

Redetermination of the cobaltocene crystal structure at 100 K and 297 K: Comparison with ferrocene and nickelocene

The molecular and crystal structures of the monoclinic modification of cobaltocene Cp₂Co (P2₁/n, Z=2) was determined at 100 K and 297 K with new sets of X-ray diffraction data (MoK radiation, 3995 and 6534 reflections, refinement toR = 0.026 and 0.030 using 1061 and 1299 independent observable reflections, respectively). At 297 K the structure is disordered (similar to the isomorphous ferrocene and nickelocene) with two distinct orientations of the ring, differing in occupancy factors (80% and 20%) and by a rotation angle in the ring plane of approximately 34°. Just as for nickelocene but in contrast to ferrocene, no sharp phase transition was found on cooling Cp₂Co to 100 K, but an essential ordering of the Cp-ring position was detected with a decrease of the contribution of the second minor orientation to nearly 10%. On the basis of a careful analysis of the molecular geometry, crystal packing, and anisotropic atomic displacement parameters, a dynamic temperature-dependent nature of the disorder in Cp₂Co is assumed.     

Structure and magnetic properties of Saturn-shaped fullerenol complexes with ferrocene and nickelocene dicarboxylic acids: DFT simulation

Structural Chemistry - DFT simulations of the electron and spin structure of fullerenol derivatives C60(OH)24·2Fe(C5H4COOH)2 and C60(OH)24·2Ni(C5H4COOH)2 have shown that these compounds...     

Solvation of ferrocene,cobaltocene, and their ions by the data of quantum-chemical calculations

Quantum-chemical calculations of solvation energy for ferrocene and cobaltocene molecules and their ionic forms in water, acetonitrile, methanol, acetone, and dimethylsulfoxide are performed in terms of the density functional method of the B3LYP type, taking into account the effect of solvent and using the Polarized Continuum Model (PCM). It is shown that the optimization of metallocene structure in liquid introduces only slight quantitative changes as compared with the data calculated for the structures optimized in the gas phase. It is shown that earlier observed deviation of experimental redox potentials of cobaltocene system in dimethylsulfoxide from the regularities of continuum electrostatics is caused by a stronger effect of this solvent on the distribution of electron density over the molecule of dissolved substance.     

Vibrational spectra and normal coordinate analysis of 2,2,2-trichloroethanol and 2,2,2-trifluoroethanol

The vibrational spectra of 2,2,2-trichloroethanol and 2,2,2-trichloroethanol and their OD deuterated analogues have been studied in argon, nitrogen and mixed argon—nitrogen matrices. The matrix spectra of the CD₂ deuterated and totally deuterated trifluoroethanol and the Raman and i.r. spectra of the liquid alcohols have also been recorded. A vibrational assignment, supported by normal coordinate analysis, is proposed for both alcohols.     

Synthesis of liquid crystal ferrocene derivatives and their complexes with Cu2+

A series of liquid crystal ferrocene-containing Schiff bases of general formula C₅H₅FeC₅H₄-C₆H₄-N=CN-(X)C₆H₃-O(O)-C₆H₄-OC_nH_2n+1 (X=H, OH, n=3–12) was obtained, together with several analogs, 1,1-bis-substituted at the ferrocene fragment, having a thermotropic nematic mesophases. Derivatives with X=OH were used to obtain Cu²⁺ chelate complexes, of which the compounds with n=10 and n=12 displayed nematic liquid crystalline properties.Physicotechnical Institute, Kazan Scientific Center, Russian Academy of Sciences, 420083 Kazan. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 402–407, February, 1992.     

Quantum chemical model of solvation for calculation of electrode potentials of redox processes involving ferrocene,cobaltocene, and their ions

Quantum chemical calculations of solvation energy for ferrocene and cobaltocene molecules and their ionic forms in water, acetonitrile, methanol, and acetone are performed in terms of the B3LYP density functional method by taking into account solvation effects and using the polarized continuum model (PCM). Standard electrode potentials of the corresponding redox pairs, the effect of solvent on them, and the overall energy of the transfer of cobaltocene cation and anion between two solvents are calculated. The calculation results well agree with the available experimental data. The present study provides sufficiently reliable grounds for the application of an ion—metallocene molecule redox pair as a pilot system for the comparison of electrode potentials and solvation energies in different solvents.     

The vibrational spectra of molecular crystals of ferrocene,ruthenocene, osmocene and nickelocene

Studies are presented of the infrared spectra (3200–400 cm^?1) of monocrystal films of Fe (C₅H₅)₂ Ru(C₅H₅)₂, Os(C₅H₅)₂ using polarized radiation, and of the laser-Raman spectra of solid samples of these compounds in the temperature range +20° to ?190°C. The samples were prepared by slow cooling of the melts. The infrared spectra of solid films of Ni(C₅H₅)₂ made by deposition on a cold window, were also recorded. Assignments of the fundamental vibrational frequencies of these molecules are given. The fundamental modes of vibrations which are forbidden by symmetry appear in the spectra of the solid state. The vibrations of species E_1u and E_2u showed definite site group splitting. At the point of phase transition in the IR spectrum of Fe(C₅H₅)₂ factor-group splitting to give 3–4 components for bands of species A_1u and A_2u and 6–8 components for bands of species e_1u and E_2u was observed. Factor-group analysis is more consistent with C₁ site symmetry of the low-temperature phase of the crystal of ferrocene than C_i, as was proposed earlier.     

Photochemical and photophysical properties ofmeso-tetraferrocenylporphyrin. Quenching ofmeso-tetraphenylporphyrin by ferrocene

It was found that the quantum yield of the fluorescence ofmeso-tetraferrocenylporphyrin (TFcP) is at most 3.0·10⁻⁵, and that of the triplet state of FTcP is at least 200 times lower than the quantum yield ofmeso-tetraphenylporphyrin (TPP). Excitation of TFcP in CCl₄ by light with λ>410 nm results in the oxidation of TFcP. The singlet and triplet excited states of TPP in toluene and acetonitrile are quenched by ferrocene with rate constants of 1.2·10¹⁰ and 1.7·10¹⁰, (4.6±0.5)·10⁸ and (1.37±0.21)·10⁹ L mol⁻¹ s⁻¹, respectively. The quenching mechanisms are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1924–1927, October, 1999.     

Photochemical properties of mixed-metal supramolecular complexes

We have prepared a series of mixed-metal trimetallic complexes of the form {[(bpy)₂Ru(BL)]₂MCl₂}ⁿ⁺(bpy 2,2′-bipyridine; BL 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq) or 2,3-bis(2-pyridyl)-benzoquinozaline (dpb); M Ir(III), Rh(III) or Os(II). This new class of trimetallic complexes can be prepared with a good yield, often as high as 95%, using our building block strategy. The central rhodium and iridium fragments of these trimetallic, namely [M(BL)₂Cl₂]⁺, have been shown in our laboratory to be capable of delivering multiple electrons, “stored” on the bridging ligand π* orbitals, to a substrate as they functioned as electrocatalysts for the reduction of carbon dioxide to formate. The two terminal ruthenium metals are good light absorbers designed to give rise to photochemical activity. These bichromophoric systems should be capable of absorbing two photons of light, each giving rise to a desired photochemical reaction, namely excited-state electron transfer. Thus these systems form the basis of a molecular device for photoinitiated electron collection. The properties of these supramolecular complexes have been tuned by variation in the central metal and bridging ligand. Comparison of this array of nine complexes is described herein.     

The dynamics of ring rotation in ferrocene,nickelocene and ruthenocene by incoherent quadi-elastic neutron scattering

Incoherent quasi-elastic neutron scattering has been used to study the reorientational motions of the cyclopentadienyl rings in ferrocene, nickelocene and ruthenocene. The results for ferrocene show that the activation energy for ring rotation drops above the 164 K phase transition to 4.4 ± 0.5 kJ mol^?1 (which is approximately half its low temperature value) but the rings still appear to jump between only five orientations on the observable time scale. At room temperature, the rings in nickelocene appear to behave the same as in ferrocene but in ruthenocene they reorientate much less frequently and resemble those in ferrocene below 164 K.     

Synthesis, characterization and liquid–liquid extraction properties of new methoxyaminobiphenylglyoxime derivatives and their complexes with some transition metals

In this study, three new aminobiphenylglyoximes, [L¹H₂] N-(2-methoxy)aminobiphenylglyoxime, [L²H₂] N-(3-methoxy)aminobiphenylglyoxime and L[³H₂] N-(4-methoxy)aminobiphenylglyoxime have been synthesized by the reaction of (E,E)-4′-biphenylchloroglyoxime with 2-Methoxyaniline, 3-Methoxyaniline and 4-Methoxyaniline in absolute ethanol. The preparation Ni^II, Co^II and Cu^II complexes of these ligands are described. The ligands and their complexes were characterized by elemental analyses, IR, mass, H¹ and ¹³C NMR spectra, thermogravimetric analyses (t.g.a) and magnetic susceptibility measurements. Ligands complexing properties were studied by the liquid–liquid extraction of selected alkali (Li⁺, Na⁺, K⁺, Cs⁺) and transition metals (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺). It has been observed that all ligands show a high affinity to Cu²⁺ ions, whereas almost no affinity to alkali metals. The extraction equilibrium constants (K _ex) for complexes of ligands with Cu²⁺ metal picrates between dichloromethane and water have been determined at 25°C.     

Photochemical properties of mixed-ligand complexes europium carboxylates

The photochemical behavior of mixed-ligand complexes of europium carboxylates with nitrogen-and phosphorus-containing neutral ligands of island and dimer types, Eu(L)₃ · xD · nH₂O and [Eu(L)₃ · xD]₂ · nH₂O (L is the trifluoroacetate, toluate, or cinnamate anion), was studied. During UV irradiation of the complexes of europium carboxylates with 1,10-phenanthroline and 2,2′-dipyridyl, a luminescence buildup was observed. EPR measurements demonstrated that the observed buildup of luminescence from europium occurs in parallel with the increase of the concentration of radical anions formed from neutral ligands.     

Photochemical properties of hypocrellin A,B and their oxides

Hypocrellin A and B in methanol were autosensitized and photooxygenated to 1, 4, 6, 7 and 2, 5, 8, 9 respectively. 1 in methanol was photooxygenated to 6 and 7 under the sensitization by HB. 1 in methanol was photooxygenated to 7 under the sensitization by Rose bengal. 1 in benzene irradiated with medium-pressure-mercury lamp was photolyzed to 3 in the presence of iodine.     

Synthesis,crystal structures and electrochemical properties of two new metal-centered ferrocene complexes

Two new metal-centered ferrocene complexes Ni(SCN)2(L)4 (1) and Cu(OAc)2(L)2 (2) (L = 1-[1-ferro- cenylmethyl]imidazole) have been synthesized and characterized by elemental analysis, single crystal X-ray diffraction analysis, spectroscopic and cyclic voltammetric measurements. The geometry of Ni(Ⅱ) in 1 is octahedral, with four ligands in the equatorial plan and two thiocyanate anions at the axial site, while that of Cu(Ⅱ) in 2 is a distorted octahedron formed by two chealted OAc- and two ligands. Single c...     

Photochemical properties of meso-substituted thiacarbocyanine dyes in solutions and in complexes with DNA

The processes of cis-trans photoisomerization and thermal back isomerization as well as the effect of DNA on the spectral and kinetic characteristics of the triplet state of a number of meso-substituted thiacarbocyanine dyes: 3,3’-diethyl-9-methoxythiacarbocyanine iodide (K1), 3,3’,9-triethylthiacarbocyanine iodide (K2), 3,3’-diethyl-9-methylthiacarbocyanine iodide (K3), and 3,3’-diethyl-9-chlorothiacarbocyanine perchlorate (K4), were studied by the flash photolysis method. Upon flash photoexcitation, the processes of trans-cis and cis-trans photoisomerization were observed for dye K1; the data on the structure of the absorption bands of the photoisomers were obtained. Complexation with DNA leads to an increase in the quantum yield of the triplet state of the dyes, which is explained by growing rigidity of the bound molecules. In the presence of DNA, triplet state deactivation follows the two-exponential law, thus showing that the dyes form complexes of two different types. The processes of quenching of the dye triplet state by oxygen were studied in solutions and in complexes with DNA. The rate constants for oxygen quenching of the triplet state of the dyes in complexes with DNA were found to be much lower than the values expected for the diffusion-controlled reactions (with allowance for the spin statistical factor, $k_{qO_2 } < 1/9k_{dif} $ ), which is explained by the steric factor of the complexation.     

Enthalpies of sublimation of ferrocene and nickelocene measured by calorimetry and the method of Langmuir

A quick and accurate methodology that is based on Langmuir’s equation and that is developed by utilising a DSC7 device is proposed for the measurement of the enthalpies of sublimation of substances characterised by vapour pressures of approximately 1.0 Pa at room temperature. The procedure was applied to ferrocene and nickelocene; the accuracy and uncertainty associated with the experimental results show that the reliability of the developed indirect method is comparable to the direct calorimetric measurements also performed in this work. Furthermore, the melting data and crystal-phase heat capacities for both metallocenes were calorimetrically measured, whereas the gas-phase heat capacity for each metallic bis(cyclopentadienyl) was theoretically estimated by DFT calculations.     

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris(β -diketonato)lanthanide(III) complexes were prepared, where the β -diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β -diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.     

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris( β-diketonato)lanthanide(III) complexes were prepared, where the β-diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β-diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.