Cyclohexylethynyl complexes of CoII and FeII

This paper deals with the synthesis of six σ-cyclohexylethynyl complexes of Co^II and Fe^II and their characterization by chemical analysis, infrared and ¹H NMR spectra, and magnetic measurements. Four of them are six-coordinate complexes, unsubstituted or substituted, namely K₄[M(C≡C—C₆H₁₁)₆] nNH₃(M = Co, n = 2; M = Fe, n = 0), K₂[Co(C≡C₆H₁₁)₄(NH₃)₂] and K₄[Fe(CN)₄-(C≡C—C₆H₁₁)₂]. Two are four-coordinate complexes of formula [(Ph₃P)₂M-(C≡C₆H₁₁)₂] (M = Co, Fe). All are low-spin complexes, the magnetic moment for the six-coordinate Co(II) complexes, measured at various temperatures, being intermediate between low- and high-spin values.     

Urea and thiourea complexes with trifluoromethanesulfonic acid and its derivatives

Urea and thiourea form complexes with trifluoromethanesulfonic acid, its monohydrate, and lithium salt CF₃SO₃Li. Urea complexes with trifluoromethanesulfonic acid are also formed as a result of hydrolysis in the reaction of N,N′-bis(trimethylsilyl)carbodiimide or cyanamide with trifluoromethanesulfonic acid in water.     

Infrared spectra of new Re(III) complexes with thiourea derivatives

Complexes of the type [Re(III)L6]X3, with L = thiourea, N-methylthiourea, N-ethylthiourea or N,N'-dimethytlthiourea and X = Cl- or PF6-, were prepared as suitable precursors for the synthesis of new rhenium complexes potentially useful in nuclear medicine. The infrared (IR) spectra of these complexes were recorded and analyzed and a general vibrational pattern for Re(III) complexes with thiourea derivatives could be established. Approximate assignments for N-allylthiourea and N-ethylthiourea are also proposed for the first time. The synthesis of the new complex [Re(III)(N-allylthiourea)6](PF6)3 is also reported, and information about its structural characteristics was obtained comparing its IR spectrum with those of the other complexes of the investigated series.     

Metal complexes with 1-hydroxyanthraquinone and its derivatives: Electronic absorption spectra and ligand structures

Reactions of metal salts with 1-hydroxyanthraquinone and its derivatives gave tautomeric 9,10-and 1,10-quinoid complexes and compounds containing no C=0 → M coordination bond. Each form is characterized by a single π₁,π*-band. The absorption bands were assigned by using correlations with the σ^A-constants of the hydroxy and oxido groups for tautomeric anthraquinones. Complexes with nonionized ligands have particularly the 9,10-anthraquinoid structures; complexes with ionized ligands can form both 9,10-and 1,10-quinoid structures.     

Spectra of tetragonally distorted tetrahedral NiII complexes

The optical spectra of four-coordinate Ni^II complexes of quasi-tetrahedral symmetry are discussed in terms of orbital splitting and the bands and band components occurring in the spectra of complexes of types MeX₂Y₂, MeX₃Y or MeXY₃ and MeX₄ or MeY₄ are explained in terms of a departure from the regular tetrahedral symmetry. The method for the calculation of characteristic parameters of the complexes is described.     

Problems connected with the melting of NiII, CoII and MnII cyclo-tetraphosphates

Differential thermal analysis has been used to follow the process of melting of Ni^II, Co^II and Mn^II cyclo-tetraphosphates. The melting is congruent in a dry atmosphere, being non-congruent in the presence of small amounts of water vapour: the tetraphosphate cycles are split and further condensed to chains of higher linear phosphates. Their end groups (and hence their stability) are provided by water molecules present in the atmosphere. After cooling the products have a glassy amorphous form. By repeated heating they are changed back into the cyclo-tetraphosphates with crystalline character, and the water molecules are released.     

Contrasting picosecond photokinetics of CoII and CoIII porphyrins verify excited-state predictions

Using picosecond transient absorption techniques, we have different low-lying excited states for several Co^II and Co^III porphyrins. These differences are interpreted in terms of theoretical calculations that predict the lowest-energy excited states to be ²(π·d) in Co^II and ³(d, d) in Co^III.     

Vibrational spectra of iodine and bromine thiourea complexes

The vibrational spectra of iodine and bromine thiourea charge transfer complexes in the solid state were obtained. The Raman spectrum shows a very strong band at 215 and 255 cm⁻¹, for the iodine and bromine complex respectively.In the case of iodine, the vibrational spectrum can be interpreted on the basis of the structure proposed by the X-ray study. The data obtained in the present investigation, strongly suggest that the bromine complex has a similar structure, albeit smaller stability.     

Die papier-chromatographische Trennung von CrIII, MnII, CoII, FeIII und NiII

Ohne Zusammenfassung     

Synthesis, characterization and chromotropic properties of MnII, CoII, NiII and CuII with bis (acesulfamato) bis ( 3 -methylpyridine) complexes

The novel 3- [M: Mn^II, Co^II, and Ni^II] and 3- complexes (acs: acesulfamate; 3-pic: 3-methylpyridine) have been synthesized and characterized using elemental analyses, magnetic moments, UV–Vis and FT-IR spectra. The thermal behaviour of the complexes was also studied by simultaneous TG, DTG and DTA methods in static air atmosphere. The chromotropic properties of all complexes have been studied using thermal and spectral analysis. While the complexes of Co^II and Ni^II show reversible continuous thermochromism, an irreversible discontinuous thermochromism is observed in the Mn^II and Cu^II) complexes in the solid state. The observed thermochromism in the Mn^II, Co^II and Ni^II complexes is due to the different ligand field strength associated with the deaquation reaction. The solvatochromic behaviour of the complexes is also studied and all anhydrous complexes (except Mn^II) exhibit solvatochromic properties depending on the donor number of the solvent.     

Electronic spectra of nitrobenzene derivatives

The gas and solution phase u.v. spectra of some nitrobenzene derivatives with substituents of different electron-donating power were analysed in terms of locally excited states and intramolecular charge transfer configurations in the MIM and PPP approximations. The spectral behaviour of the examined compounds is defined by the different electron-donating power of the substituents and by the degree of mixing of the excited states, following the substitution position.     

Determination of thiourea and its organic derivatives with iodine trichloride

Thiourea and its organic derivatives and thiosemicarbazide are determined in water, methanol or glacial acetic acid medium by reaction with an excess of iodine trichloride in the presence of mercuric chloride. The reaction is complete in 15 min. The excess of iodine trichloride is evaluated by adding potassium iodide and titrating the liberated iodine with thiosulphate. A variety of organic thioureas can be determined with an average accuracy and precision of 0.2%.     

Synthesis and electrochemical characterization of CoII, NiII, and CuII complexes with organic N2S2-type ligands derived from 2-thio-substituted benzaldehydes and aromatic amines

Transition metal complexes (Ni^II, Co^II, and Cu^II) with tetradentate N₂S₂-type ligands (L), which are reaction products of 2-thio-substituted benzaldehydes with aromatic amines (3-aminopyridine or 2-aminothiophenol), were synthesized for the first time. The complexes have the composition L·MX₂ or L·2MX₂ (X = Cl or ClO₄). The electrochemical behavior of the ligands and complexes was studied by cyclic voltammetry and rotating disk electrode voltammetry. Depending on the structure of the complexes, the metal atom in the latter is initially reduced in a one-or two-electron process. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2124, November, 2007.     

Electronic structure of anionic σ complexes of m-dinitrobenzene and its derivatives

It has been established as a result of calculations of the electronic structure of products of the addition of nucleophilic agents (H^– and CH ₃ ^– ) to m-dinitrobenzene and its derivatives by the CNDO/S method that the negative charge of these anions is delocalized over the system of the cyclohexadiene ring (50%) and the nitro groups (15–20% each), of which the nitro group in the para position (to the sp³-hybridized carbon atom) is more negatively charged. A certain fraction of the charge of the anion is distributed according to an induction mechanism to the hydrogen atoms and the geminal substituents. The data on the bond orders and the distribution of charges attest to the quinoidal structure of the carbon ring in the a complexes. The results of the calculations make it possible to predict the direction of the reactions of the anionic complexes with electrophilic and nucleophilic reagents. The calculated values of the total energies of the complexes correctly reflect their relative stability.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 1, pp. 27–33, January–February, 1989.     

Electronic structures and spectra of cyanoethylene derivatives

Results of two different types of molecular orbital calculations of severalπ-orbital systems containing nitrile groups are reported and compared. The bidentate ligandbis-(methylmercapto) maleonitrile and related molecules are included. Electronic spectra of these molecules are reported and assigned in terms of the calculated energies.     

Non-isothermal kinetic study of the solid-gas thermal decompositions of some coordination compounds of CoII and NiII

Using a method developed by us, a non-isothermal kinetic study of the thermal decomposition of some coordination compounds (CC) with the general formula Me^IIL_pX₂, where

, was performed.     

Die Zusammensetzung der Komplexe von ZnII, CoII, CuII, CaII und SrII mit 5,7-Dibrom-8-hydroxychinolin

Ohne Zusammenfassung     

Complexes of N, S donor ligands. CoII, CoIII, MnIII, FeIII and PdII complexes of 1, 2-di( o -aminophenylthio)ethane: Synthesis, characterisation and reactions

The ligand 1,2-di(o-aminophenylthio)ethane (abbreviated as H₂DAPTE) has been allowed to react with various metal salts and the complexes isolated and characterised. In these complexes, H₂ DAPTE behaves as a neutral quadridentate and also as a dibasic quadridentate ligand after losing two protons from the amine functions. Two complexes of this ligand, reported earlier, have been condensed with acetone to form macrocyclic complexes of TDDH where TDDH is 13, 13, 15-trimethy1-2,5-dithia-12, 16-diazatricyclo-[15,3,0,0,6,11]-docosa-1(17), 6(11), 7,9,15,18,20-heptene.     

Electronic absorption spectra of 3-β-carboxyethylrhodanine and its 5-arylidene derivatives

The UV spectra of 3--carboxyethylrhodanine and its 5-arylidene derivatives comprise four bands. The first absorption band with a peak at 239 m is not very characteristic of rhodanines. The second band, connected with the presence of the chromophore {\text{N}}{}^{\text{\_}}{\text{C = S}} \hfill \\ {\text{ |}} \hfill \\ \end{gathered} $$ " align="middle" border="0"> , is characterized by peaks in the 243–281 m region.The peak of the third absorption band at about 300 m, is connected with the presence of an amide chromophore, which shifts bathochromically on introduction of a benzylidene group; subsequent introduction of nitro groups results in its being displaced hyposochromically. The most characteristic feature of the 5-arylidene derivatives is formation of a very intense K absorption band in the 360–466 m region, superimposed on the corresponding low-intensity 3--carboxyethylrhodanine absorption band.     

Electronic and vibrational spectra of mixed-valence complexes with a metal--halide chain

The electronic and vibrational spectra of compounds with a M(II)---X—M(IV) (where M = Pt, Pd, Ni and X = Cl,Br,I) chain are briefly reviewed and some new results reported. Emphasis is given on the size effects. The interpretation of the optical absorption spectra is based on the assumption that the gap energy increases as the size of the particles decreases. A red shift predicted for the resonance Raman excitation profiles is in agreement with the experiments.