Roman Klička

Complexes of iron(III) salen and saloph Schiff bases with bridging dicarboxylic and tricarboxylic acids

Six new dinuclear or trinuclear FeIII complexes involving tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine (salenH2) or bis(salicylidene)-o-phenylenediamine (salophH2) with 2,5-pyridinedicarboxylic acid, acetylenedicarboxylic acid or 1,3,5-benzenetricarboxylic acid have been synthesized and characterized by means of elemental analysis, i.r. spectroscopy, thermal analyses, conductivity measurements and variable-temperature magnetochemical measurements to the temperature of liquid nitrogen. The complexes can be characterized as high-spin distorted octahedral FeIII bridged by carboxylic acids. The dicarboxylic or tricarboxylic acids play a role as bridges for weak antiferromagnetic intramolecular exchange. The antiferromagnetic coupling parameters J vary in the -1.99 to -5.47cm-1 range for the dimers, whilst the values are -2.35 and -1.42cm-1 for the salen and saloph trimers, respectively. One complex, namely [{Fe(saloph)}2(2,5-dicarpy)]middot H2O, obeys the Curie-Weiss law.

Statistical properties of linearization of the Arrhenius equation via the logarithmic transformation

Abstract The temperature dependence of a rate constant is usually described by the Arrhenius equation. It can be transformed into a linear model by the logarithmic transformation of the dependent variable. The parameter vector in the linearized model is then often estimated by the ordinary least squares estimator. Theoretical bias and the covariance matrix of the parameter vector in the linearized model are given for this method if the original errors are normally distributed, independent and have a constant variance. The expressions are verified by computer simulation of a numerical example. This true covariance matrix of the parameter vector is compared with that if the change of distribution of errors is neglected. The results are also compared with those obtained by the generalized least squares estimator.

Binuclear iron(III)-iron(III) complexes with the tetradentate Schiff base N,N′-bis(salicylidene)ethylenediamine and dicarboxylic acids or dithiooxamide as bridging ligands

SummaryComplexes of the type [(Fe(salen))2L]·xH2O (L = glutarate, adipate, pimelate or suberate dianion, x = 0 or L = dithio oxamidate dianion, x = 2) have been prepared and studied by elemental analyses, i.r. and electronic spectra, and magnetic measurements. A dimeric structure with an octahedral arrangement of FeIII (S = 5/2) is proposed. Some of the complexes have been characterized by temperature-dependent magnetic susceptibilities, but an antiferromagnetic exchange interaction was found only for [(Fe(salen))2dta]·2H2O (H2dta = dithio-oxamide).

Synthesis and characterization of (μ-oxalato) copper(II) and nickel(II) complexes

Four new binuclear complexes of the type [(u(L)x)2ox](ClO4)2 (L = 1,3-diaminopropane (1,3-pn), x = 1.5 (1); L = 1,3-diaminopropane, x = 1 (2)l; L = N-(2-aminoethyl)-1,3-propanediamine (ept), x = 1 (3)) or [(Ni(L)2)2ox](ClO4)2 (L = 1,2-diaminopropane (1,2-pn) (4)) have been prepared and studied by elemental analysis, IR and electronic spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between five-coordinate (N3O2) Cu(II) (compounds 1 and 3), four coordinate (N2O2) Cu(II) (2) and six-coordinate (N4O2) Ni(II) (4). Magnetochemical measurements (72–300 K) show (2) and (4) are antiferromagnetic (J = −254 and −33 cm−1 respectively (H = −JS1S2)).

Adsorption in semi-differential voltammetry

The function for the time semi-derivative of the reversible current response of a thin layer of adsorbed electroactive species in linear scan voltammetry is derived. Its properties are compared with the original current response, its semi-integral, and integral. This series is compared with the analogous series of reversible semi-infinite linear diffusion current response and its differintegrations.

INVESTIGATION OF 1,2-BIS(DIPHENYLPHOSPHINO)ETHANE-P, P'-(DITHIOCARBONATO-S, S')-NICKEL(II)

SummaryThe reaction of bis(iso-propylxanthato)nickel(II) with 1,2-bis(diphenylphosphino)ethane (dppe) in a 1∶1 molar ratio affords [Ni(S2CO)(dppe)], which, on the basis of its magneto-chemical and spectral properties, has been characterized as a square-planar Ni complex. The complex was one-electron irreversibly oxidized at a potential of 0.673 V versus s.c.e. The crystal and molecular structure of a twinned crystal of the complex has been elucidated, and consists of two crystallographically independent molecules in which each Ni atom is coordinated by two S atoms from the dithiocarbonate ligand and two P atoms from the dppe ligand in an approximately square-planar arrangement.

Mononuclear and binuclear complexes of iron(III) with the tetradentate Schiff base derived from salicylaldehyde and 1,2 diaminopropane

Abstract The complexes of type [Fe(salpn)L]ClO4 [L = bpy (2,2′-bipyridyl) or phen (o-phenanthroline), H2salpn = N,N′-bis(salicylidene)propylenediamine] and type [(Fe (salpn))2L] (L = terephthalate or fumarate dianion) have been prepared and studied by elemental analyses, IR and electronic spectroscopies and magnetochemical measurements. An octahedral arrangement of iron(III) (S = 5/2) is proposed. The complexes with dicarboxylic acids are probably binuclear and magnetically diluted at room temperature. The compounds with bpy or phen are probably mononuclear. Regarding their anomalous μeff values (5.52 or 4.25 B.M.), the temperature dependence of magnetic susceptibility was measured, but antiferromagnetic exchange interaction or spin equilibrium were not found.

The Polynuclear Complexes of Iron(II,III) and Copper(II) with Cyanide as Bridging Ligand

Abstract Five novel complexes of the type [CuL2][Fe(CN)5NO]. xH2O (L = ethylenediamine (en), x = 0; L = o-phenanthroline (phen) or 2,2′-bipyridine (bpy), x = 2), [CuL2]3[Fe(CN)6]2. xH2O (L = bpy, x = 6; L = phen, x = 9) have been prepared and studied by elemental analyses, thermal analyses, IR and UV-vis. spectra and magnetic measurements. The structures are proposed with cyanide bridges between Fe(II) and Cu(II) (nitroprusside complexes) or between Fe(III) and Cu(II) (hexacyanoferrate(III) complexes). The temperature dependence of the magnetic susceptibility of the complex [Cu(bpy)2]3[Fe(CN)6]2. 6H2O was measured in the range 94.4–293.5 K but no exchange interaction was found. The product of the thermal decomposition of the complex [Cu(bpy)2]3[Fe(CN)6]2. 6H2O is a mixture of CuO and CuFe2O4, as determined by X-ray powder diffraction.

MONO- AND BINUCLEAR COMPLEXES OF IRON(III) WITH 1,2-BIS(2-HYDROXYBENZAMIDO)ETHANE

Summary. Complexes of the type [(Fe(L))2O]ċH2O (H2L=1,2-bis(2-hydroxybenzamido)ethane), [(Fe(L))2ter]ċ5H2O H2ter=terephthalic acid), [Fe(L)bpy]BPh4 (bpy=2,2′-bipyridyl), and [Fe(L)phen]ClO4ċH2O (phen=o-phenanthroline) were prepared and studied by elemental analysis, magnetochemical measurements, and spectroscopic methods. [(Fe(L))2O]ċH2O and [(Fe(L))2ter]ċ 5H2O are probably binuclear, and the weak antiferromagnetic exchange interaction, (μeff per one atom of iron(III) was found to be 3.59 BM/77 K−4.91 BM/290 K (J=−7 cm−1, H=−2JS1S2, S1=S2=5/2) for the μ-oxo complex and 4.21 BM/82 K−5.35 BM/297 K (J=−5 cm−1) for the μ-terephthalato complex. The iron(III) complexes with bpy or phen are probably mononuclear; their anomalous μeff values (3.51 BM/80 K−3.68 BM/297 K for (Fe(L)bpy]BPh4 and 4.93 BM/259 K for [Fe(L)phen]ClO4ċH2O, respectively) agree neither with high spin (5.7–6.1 BM) nor with low spin (2.1–2.5 BM) configurations.Zusammenfassung. Komplexe des Typs [(Fe(L))2O]ċH2O (H2L=1,2-Bis(2-hydroxybenzamido)ethan), [(Fe(L))2ter]ċ5H2O (H2ter=Terephthalsäure), [Fe(L)bpy]BPh4 (bpy=2,2′-Bipyridyl) und [Fe(L)phen]ClO4ċH2O (phen=o-Phenanthrolin) wurden hergestellt und mittels Elementaranalyse, magnetochemischer Messungen und spektroskopischer Methoden untersucht. [(Fe(L))2O]ċH2O und [(Fe(L))2ter]ċ5H2O sind wahrscheinlich binuklear, und die schwache antiferromagnetische Austauschwechselwirkung (μeff pro Eisen(III)-Atom) wurde für den μ-oxo-Komplex zu 3.59 BM/77 K−4.91 BM/290 K (J=−7 cm−1, H=−2JS1S2, S1=S2=5/2) und für den μ-terephthalato-Komplex zu 4.21 BM/82 K−5.35 BM/297 K (J=−5 cm−1) ermittelt. Die Eisen(III)-Komplexe mit bpy bzw. phen sind wahrscheinlich mononuklear; ihre anomalen μeff-Werte (3.41 BM/80 K−3.68 BM/297 K für [Fe(L)bpy]BPh4 und 4.93 BM/259 K für [Fe(L)phen]ClO4ċH2O sind weder mit high-spin- (5.7–6.1 BM) noch mit low-spin-Zuständen (2.1–2.5 BM) in Einklang zu bringen.