Desolvaton of Zinc(II)tetra-tert-butylphthalocyanine Crystal Solvates as Probed by Thermogravimetry

Kinetic analysis of the thermal destruction of complexes of zinc(II)tetra-tert-butylphthalocyanine Zn(t-Bu)₄Pc with organic solvent molecules has been carried out. For ligands having high ionization potentials, long refluxing of solution is required for preparing biligand complexes. For molecular ligands whose ionization potentials do not exceed 9.2 eV, the composition of complexes with Zn(t-Bu)₄Pc is independent of the preparation parameters. The destruction of the Zn(t-Bu)₄Pc complexes with n-propylamine, diethylaniline, piperidine (1: 1, cold synthesis), diethylamine, morpholine, quinoline, or cyclopentanone (1: 2, hot synthesis; 1: 2, cold synthesis) obeys fist-order equations; for complexes with pyridine, 1,4-dioxane, DMF, cyclopentanone (1: 1, hot synthesis), 3-dimethylaminopropionitrile, or piperidine (1: 2, hot synthesis), destruction obeys second-order equations. The activation energies of thermal destruction for the first group of molecular complexes fall in the range from 89 to 370 kJ/mol; the rate-controlling stage is nucleation and growth. For the second group, the activation energies fall in the range from 160 to 640 kJ/mol; the rate-controlling stage is a chemical reaction.     

Interaction of zinc(II) tetra-<Emphasis Type="Italic">tert</Emphasis>-butyl-phthalocyaninate with organic ligands in solution

Calorimetric titration was used to obtain standard thermodynamic characteristics of zinc(II) tetra-tert-butyl-phthalocyaninate interaction with electron-donor ligands in benzene. The formation of molecular complexes of Zn(t-Bu)₄Pc with ligands (hexamethylphosphoramide, pyridine, piperidine, and morpholine) was found to be greatly affected both by the electron-donor and polarization properties of the coordinated ligands, as well as by the solvation effect of a medium. It was shown that the formation of thermodynamically stable molecular complexes of zinc(II) tetra-tert-butyl-phthalocyaninate with the electron-donor solvents (with stability constant K_s > 10⁴) favors the formation of -polymorphic modification of a metal phthalocyaninate during its crystallization from a given solvent.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 915–918.Original Russian Text Copyright © 2004 by Lebedeva, Malkova, Pavlycheva, Vugin.     

Reactions of Chelate Complexes with Macrocyclic Ligands. Tetra-tert-butylphthalocyanine

Complexation reactions of tetra-tert-butylphthalocyanine (I) with Cu(II) acetate, acetylacetonate, 8-hydroxyquinolate, glycinate, valinate or dithizonate, as well as with Zn(II), Co(II), and Ni(II) 8-hydroxy-quinolates, valinates, and dithizonates were studied. Unlike porphyrins themselves and porphyrins with planar distortions, compound I was found to form metal phthalocyanines with all indicated chelate salts in common solvents. It was established that compound I exhibits more equalized dependences of the coordination rate on the nature of the salt anion and cation as compared to the majority of the other porphyrins.     

Thermodynamic properties for intermolecular complexes of zinc(II)tetra-tert-butyl-phthalocyanine with ligands

The enthalpy, entropy and stability constant for the interaction of zinc(II)tetra-tert-butyl-phthalocyanine with 3-dimethylaminopropionitrile, diethylamine, hexamethylendiamine and DMF in a benzene solvent have been determined by titration calorimetric.     

Thermogravimetry of heteroleptic zinc tri-tert-butoxysilanethiolates: synthesis and crystal structure of bis(tri-tert-butoxysilanethiolato)(pyridine) zinc(II)

Thermal behaviour of three silanethiolate zinc complexes i.e., bis(tri-tert-butoxysilanethiolato)bis(pyridine) zinc(II), bis(tri-tert-butoxysilanethiolato)bis(N-methylimidazole) zinc(II) and bis(tri-tert-butoxysilanethiolato) (2-methylpyridine) zinc(II) was studied. In order to determine the steps involved in thermal decay, decomposition intermediates were identified by means of IR spectroscopy and solid residues were analysed. Enthalpies of undergoing processes were estimated on the basis of DTA curves. The results of the study were applied to the synthesis of a new complex - bis(tri-tert-butoxysilanethiolato)(pyridine) zinc(II). NMR and IR spectra of this complex were measured and crystal and molecular structures were determined.     

Interaction of porphyrins with adenine and adenosine complexes. Effect of a metal nature

Reactions of complex formation of 5,10,15,20-tetraphenylporphine (H₂TPP) and tetra-tert-butylphthalocyanine (H₂(t-Bu)₄Pc) with adenine and adenosine complexes of d-metals in DMSO and ethanol are studied. It was found that H₂TPP reacts with Cu(II) and Hg(II) adeninates and adenosinates in DMSO, but does not react with Zn(II), Co(II), and Cd(II) adeninates and adenosinates (with both bridging and monodentate type of the ligand coordination). H₂(t-Bu)₄Pc enters the complex formation reaction with adeninates and adenosinates of all studied metals in DMSO at almost equal rates. The states of adenine and adenosine complexes of different d-metals in DMSO and ethanol are proposed on the basis of kinetic data obtained.     

Mixed-ligand complexes of zinc(II), cobalt(II) and cadmium(II) with sulfur, nitrogen and oxygen ligands. Analysis of the solid state structure and solution behavior. Implications for metal ion substitution in alcohol dehydrogenase

In this paper we characterize new, mixed ligand complexes of zinc(II), cobalt(II) and cadmium(II) with tri-tert-butoxysilanethiolate and 2-(2′-hydroxyethyl)pyridine ligands. Due to the chelating versus non-chelating behavior of 2-(2′-hydroxyethyl)pyridine ligand we have obtained an interesting structural variety in the studied system. The presented coordination patterns together with the results of NMR studies have been used to illustrate a rapid chemical exchange undergoing in methanolic solutions of zinc(II) and cadmium(II) complexes. UV-Vis spectra of cobalt(II) species have also evidenced an exchange in the case of cobalt(II) complex. The relative strength of hydrogen bond formed by hydroxyl group bonded to Zn(II), Co(II) or Cd(II) was evaluated by analysis of structural parameters and position of the OH stretching vibrations in the FT-IR spectra of the complexes in solid state. The data were compared with the activity of zinc (native) alcohol dehydrogenase and alcohol dehydrogenase substituted with cobalt and cadmium ions. The enthalpies of proton abstraction in zinc and cobalt complexes were calculated and found to be very similar. The attempt to apply zinc tri-tert-butoxysilanethiolate as a catalyst in the biomimetic reaction of reduction of N-benzylnicotinamide chloride by ethanol was unsuccessful.     

Synthesis and coordination properties of the zinc complex of dimeric porphyrin in reactions with imidazole, 2-methylimidazole, and the pyridine in benzene

Dimeric porphyrin(2,6-bis[15′-(3″,5″-di-tert-butylphenol)-3′,7′,13′,17′-tetramethyl-2′,8′,12′,18-tetraethylporphin-5′-yl]-4-tert-buthylphenol) and its binuclear zinc complex were obtained from 4,4′-dimethyl-3,3′-diethyldipyrrolylmethane, 2,6-diformyl-4-tert-butylphenol and 3,5-di-tert-buthylbenzaldehyde. Coordina-tion properties of dimeric zincporphyrin in the intermolecular reaction with nitrogen-containing bases (imidazole, 2-methylimidazole, and pyridine) in benzene were studied. Geometry and electronic structure of the zincporphyrin and its molecular complexes were calculated by a quantum-chemical method. Energy characteristics of the intermolecular reaction of the dimeric zincporphyrin with bases were determined. The calculated energies of the central metal atom interaction with the nitrogen atom of an extra-ligand agree well with the stability of the Zn-porphyrin molecular complexes. The influence of the deformation distortions of the porphyrin ligand on the strength of the metal-extra-ligand σ-bond was established.     

Group II metal complexes with the N-(2-oxy-3,5-di-tert-butylphenyl)-4,6-di-tert-butyl-o-iminobenzoquinone ligand: an ESR study

The Group II metal (Mg, Ca, Sr, Ba, Zn, Cd) complexes based on the paramagnetic N-(2-oxy-3,5-di-tert-butylphenyl)-4,6-di-tert-butyl-o-iminobenzoquinone ligand were generated in solutions and studied by ESR spectroscopy. The magnesium, zinc, and cadmium complexes with trialkylphosphine ligands were prepared. Their molecular structures and electron density distribution were studied by ESR spectroscopy and DFT calculations.     

Synthesis and Complexation Properties of a New Class of Receptors based on a cone-configurated tetra-p-(tert-butyl)calix[4]arene and bipyridyl subunits

0The bipyridyl-armed tetra-p-(tert-butyl)calix[4]arenes 1 – 5 were synthesized from tetra-p-(tert-butyl)-calix[4]arene A and 6-(bromomethyl)-6′-methyl-2,2′-bipyridine ( B ) by direct base-strength-driven regioselective O-alkylation or by stepwise procedures. Preliminary complexation studies of the ligands 1 – 3 with Cu^I affording the complexes 6 – 8 are described.     

Geometry and energy of tetra-tert-butylethylene

The geometry and energy of tetra-tert-butylethylene have been determined by the molecular mechanics method. A twisting of the double bond by 45.5° was found. The ground state of the molecule should be a singlet. The calculated strain energy is higher than those of tri-tert-butylmethane and tetra-iso-propylethylene, but the possibility of synthesis of the compound is not excluded.     

Coordination properties of (chloro)aluminum-5,15-diphenyloctaalkylporphyrin in the reactions with small organic molecules

The reactions of aluminum porphyrinate ((Cl)AIP) with organic molecules L (imidazole, pyridine, pyrimidine, and pyrazine) in benzene were studied using spectral and quantum-chemical methods. The structures and stabilities of the molecular complexes (Cl)Al(L) _n P in solutions were determined. The influence of the nature of the macrocyclic ligand and organic base on the coordination properties of aluminum porphyrinate was observed. The degree of deformation of the metalloporphyrin and its molecular complexes was estimated. A good correlation between the experimental and calculated characteristics     

Titration Calorimetric Investigation of Interactions of Zinc(II), Nickel(II), and Copper(II) Tetraphenylporphine Complexes with Pyridine in Three Solvents

Titration calorimetry was used in a thermodynamic study on the interactions of pyridine (Py) with zinc(II)-tetraphenylporphine (ZnTPP), nickel(II)-tetraphenyl-porphine (NiTPP), and copper(II)-tetraphenylporphine (CuTPP) in benzene, chloroform, and carbon tetrachloride solutions. The coordinating properties of the metalloporphyrins in relation to pyridine were found to diminish in the order ZnTPP > CuTPP > NiTPP. Solvation effects were estimated from the interactions between metalloporphyrins (MP) and Py. The more negative values of the enthalpy and entropy of reaction of ZnTPP with Py, following the order of solvents CCl₄ > C₆H₆ > CHCl₃, was found to be related to the different types of (MP–solvent) and (Py–solvent) interactions. The NiTPP and CuTPP complexes showed the opposite trend.     

Isotopic Study of the Formation of Phenoxazine Derivatives in the Transformations of 3,5-Di-tert-Butylcatechol Adsorbed in Thin SiO2-nTiO2 Layers in the Air

A study was carried out on the isotopic composition of the tetra-tert-butylphenoxazine derivatives formed in the heterophase transformations of 3,5-di-tert-butylcatechol adsorbed on thin SiO2 layers with microscopic traces of Ti and Mn in a nitrogen-oxygen atmosphere enriched with ¹⁵N₂. The formation of isotopically-labeled tetra-tert-butylphenoxazinyl and hydroxytetra-tert-butylphenoxazinyl radicals and tetra-tert-butylphenoxazinone indicated the participation of atmospheric nitrogen in the heterophase catalytic reaction.     

Synthesis and physicochemical properties of highly soluble tetra-tert-butyl-2,3-naphthalocyanine complexes of lanthanides

Tetra-tert-butyl-2,3-naphthalocyanine complexes of lanthanides were obtained by the reaction of tetra-tert-butyl-2,3-nap hthalocyanine with lanthanide salts. Oxidation and aggregation of these complexes were studied by electronic and ESR spectroscopies.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 99-102, January, 1996.     

Titration Calorimetric Investigations on the Interactions of Zn(II) Porphyrin Complexes with Pyridine in Benzene and Chloroform at 298.15 K

Titration calorimetry was used in a thermodynamic study on the interactions of pyridine with natural zinc(II) porphyrin derivatives in benzene and chloroform at 298.15 K. The ability of zinc porphyrins to coordinate to pyridine is higher in benzene than in chloroform and also depends on the molecular structure of the metalloporphyrin.This revised version was published online in November 2005 with corrections to the Cover Date.     

The kinetics of proton transfer from octaphenylsubstituted tetraazaporphyrin to organic bases in benzene

The acid-base interaction of octa(m-trifluoromethylphenyl)tetraazaporphin with pyridine, 2-methylpiridine, morpholine, benzylamine, piperidine, n-butylamine, diethylamine, tert-butylamine, and triethylamine in benzene was studied. It was found that intermolecular transfer of spatially screened NH-group protons from octa(m-trifluoromethylphenyl)tetraazaporphin to morpholine, benzylamine, piperidine, n-butylamine, and tert-butylamine is characterized by unusually low values of rate constants. The effect of the structure of octa(m-trifluoromethylphenyl)tetraazaporphin, octa(n-bromophenyl)tetraazaporphin, octa(n-bromophenyl)tetraazaporphin, and octa(n-nitrophenyl)tetraazaporphin, and the nature of a base on the kinetic parameters of acid-base equilibrium is shown. A structure for complexes with proton transfer of octaphenylsubstituted tetraazaporphirins is suggested. It is revealed that they are subject to decomposition over time with the formation of low molecular colorless products.     

Synthesis,characterization, and crystal structures of cobalt(II), copper(II), and zinc(II) complexes of a bidentate iminophenol

A bidentate iminophenol (HL = 2-((4-methoxyphenylimino)methyl)-4,6-di-tert-butylphenol derived from condensation of 4-methoxyaniline and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) was mixed with divalent metal salts to form the corresponding mononuclear metal complexes [M^II(L)₂] (M = Co (1), Cu (2), and Zn (3)). The complexes are characterized by different spectroscopic and analytical tools. X-ray crystal structures of the complexes revealed homoleptic mononuclear complexes with MN₂O₂ coordination. The cobalt(II) (1) and zinc(II) (3) complexes display a pseudo-tetrahedral coordination geometry, whereas the copper(II) complex (2) exhibits a distorted square-planar coordination. The zinc(II) complex (3) emits at 460 nm with a twofold enhancement of emission with respect to the free iminophenol.     

3,5-di-tert-butyl-1,4-benzoquinone ferrocenoylhydrazone and its zinc(II), palladium(II), and mercury(II) complexes: Structure and properties

A new ligand system, 3,5-di-tert-butyl-1,4-benzoquinone ferrocenoylhydrazone, was synthesized and its complexes with zinc(II), Hg(II), and palladium(II) were prepared. The compounds were studied by IR, electron absorption, and ¹H NMR spectroscopy. Structure of the compounds obtained is discussed.     

Synthesis,Crystal Structures,and Thermal Properties of New Zinc(II) Thiocyanato Coordination Compounds

Reaction of zinc(II) thiocyanate with pyrazine, pyrimidine, pyridazine, and pyridine leads to the formation of new zinc(II) thiocyanato coordination compounds. In bis(isothiocyanato‐N)‐bis(μ₂‐pyrazine‐N,N) zinc(II) ( 1 ) and bis(isothiocyanato‐N)‐bis(μ₂‐pyrimidine‐N,N) zinc(II) ( 2 ) the zinc atoms are coordinated by four nitrogen atoms of the diazine ligands and two nitrogen atoms of the isothiocyanato anions within slightly distorted octahedra. The zinc atoms are connected by the diazine ligands into layers, which are further linked by weak intermolecular S ··· S interactions in 1 and by weak intermolecular C–H ··· S hydrogen bonding in 2 . In bis(isothiocyanato‐N)‐bis(pyridazine‐N) ( 3 ) discrete complexes are found, in which the zinc atoms are coordinated by two nitrogen atoms of the isothiocyanato ligands and two nitrogen atoms of the pyridazine ligands. The crystal structure of bis(isothiocyanato‐N)‐tetrakis(pyridine‐N) ( 4 ) is known and consists of discrete complexes, in which the zinc atoms are octahedrally coordinated by two thiocyanato anions and four pyridine molecules. Investigations using simultaneous differential thermoanalysis and thermogravimetry, X‐ray powder diffraction and IR spectroscopy prove that on heating, the ligand‐rich compounds 1 , 2 , and 3 decompose without the formation of ligand‐deficient intermediate phases. In contrast, compound 4 looses the pyridine ligands in two different steps, leading to the formation of the literature known ligand‐deficient compound bis(isothiocyanato‐N)‐bis(pyridine‐N) ( 5 ) as an intermediate. The crystal structure of compound 5 consists of tetrahedrally coordinated zinc atoms which are surrounded by two isothiocyanato anions and two pyridine ligands. The structures and the thermal reactivity are discussed and compared with this of related transition metal isothiocyanates with pyrazine, pyrimidine, pyridazine, and pyridine.