Synthesis,spectroscopic and structural studies of tris(3-methyl-pyridinium)(3-ethylpyridinium)β-octamolybdate monohydrate

Summary Three isostructural compounds of general formula (3-MepyH) _x (3-EtpyH)_4–x [Mo₈O₂₆] (x=0, 2, 4) crystallize in the monoclinic system, space group P2₁/n, Z=2. Previously determined parameters for the compoundx=4 area=13.652(2),b=10.887(1),c=13.759(1) Å, =90.87(1)°,V=2044.8(4) ų,Dx=2.53,Do=2.54(1) mg m^–3,F(000)=1496. Slight differences in cell dimensions have been observed whenx=0 or 2. A nonisomorphous compound of formula (3-MepyH)₃(3-EtpyH)[Mo₈O₂₆]·H₂O crystallizes in the triclinic system, space group P2₁/n,Z=2,a=10.918(1),b=10.985(3),c=18.991(2) Å, =97.19(2), =91.45(2), =107.30(2)⁰,V=2152.8(7) ų,Dx=2.456,Do=2.456(5) mg m^–3,F(000)=1532. The distinguishing features of tris(3-methylpyridinium)(3-ethylpyridinium) -octamolybdate monohydrate are its non-centrosymmetric polyanion and its extensive hydrogen bonding. The asymmetric unit contains three independent 3-methylpyridinium and one 3-ethylpyridinium cations, one water molecule and the -octamolybdate anion. The planar cations are oriented to permit hydrogen bonds with either molybdate oxygen atoms or water oxygen atoms. Four different types of hydrogen bonds have been found: N–H...O (mono- and bifurcated); N–H...Ow (monofurcated); Ow–Hw...O (monofurcated); and C–H...O (monofurcated). The proposed hydrogen bonding interactions appear to stabilize the structure.     

Structural studies on 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazan chelates with cerium(III), thorium(IV) and uranium(VI)

Summary Solid complexes of 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazans were prepared and characterized by elemental analysis, IR, NMR, TGA and DTA analyses. Based on these studies, the suggested general formula for the complexes is [M(HL) _m (OH^–) _n or (NO ₃ ^– or Cl^–) _x ·(H₂O) _y or (C₂H₅OH orDMSO) _z , where HL=formazanM=Ce³⁺, Th⁴⁺, and UO ₂ ²⁺ ,m=1–2,n=0–3,x=0–3,y=0–4 andz=0–3. The metal ions are expected to have coordination numbers 6–8.

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Strukturuntersuchungen an 3-Acetyl-1,5-diaryl- und 3-Cyan-1,5-diaryl-formazan-Chelaten mit Cer(III), Thorium(IV) und Uran(VI)

Zusammenfassung Die hergestellten Chelate wurden mittels Elementaranalyse, IR, NMR, TGA und DTA charakterisiert. Darauf basierend wird die generelle Formel [M(HL) _m (OH^–) _n bzw. (NO ₃ ^– oder Cl^–) _x ·(H₂O) _y oder (C₂H₅OH bzw.DMSO) _z ] vorgeschlagen, wobei HL=Formazan,M=Ce³⁺, Th⁴⁺ oder UO ₂ ²⁺ ,m=1–2,n=0–3,x=0–3,y=0–4 undz=0–3. Die Metallionen haben Koordinationszahlen von 6–8.

     

Kristallstruktur von Trimethylisocyanursäure, (CH3NCO)3, und von Trichlorisocyanursäure-1/2-Ethylenchlorid, (ClNCO)3·1/2C2H4Cl2

X-ray crystal structure analyses of (CH₃NCO)₃ (M) and (ClNCO)₃·1/2C₂H₄Cl₂ (C) were carried out at room temperature (MoK, graphite monochromator, =0.71069 Å): 1.M=171.16, monochlinic, P2₁/c,a=14.848 (1) Å,b=13.400 (2) Å,c=8.149 (1) Å, =100.87 (1)°,V=1 592.3 ų,Z=8,F(000)=720,d _x =1.428 Mgm^–3, =76m^–1,R=6.51%,R _w =7.01% (964 reflections, 218 parameters). 2.M=281.89, monochlinic, P 2₁/c,a=9.416 (3) Å,b=5.728 (1) Å,c=18.199 (8) Å, =98.64 (2)°,V=970.4 Å₃,Z=4,F(000)=556,d _x =1.929 Mgm^–3, =1.11 mm^–1,R=3.96%,R _w =3.44% (605 reflections, 132 parameters). The ring systems together with the C atoms of the methyl groups in (M) and with the Cl atoms in (C) are planar and have D_3h-symmetry. Bond lengths and bond angles are discussed with regard to¹⁴N-NQR,³⁵Cl-NQR and vibrational spectroscopic data.

     

Measurement of inter- and intramolecular charge transfer in the complex N2ICl from analysis of halogen nuclear quadrupole hyperfine structure in the rotational spectrum

The ground-state rotational spectra of two isotopomers ¹⁵N₂I³⁵Cl and ¹⁵N₂I³⁷Cl of a complex formed between dinitrogen and iodine monochloride were observed by pulsed-jet, Fourier-transform microwave spectroscopy. The spectra were interpreted on the basis of a linear equilibrium geometry with the weak bond formed between N and I. The spectroscopic constants B₀, D_J, χ_aa(I), χ_aa(Cl) and M_bb(I) were determined for each isotopomer and various models for the complex were employed to yield the distance r(NI)=3.180(2)Å, the intermolecular stretching force constant k_σ=5.37(3) Nm⁻¹, and the inter- and intramolecular electronic transfers δ_i=0.004(3) and δ_p(Cl)=0.018(2).     

The structure of astatine azide, AtN3—A theoretical study

For the first time theoretical evidence for the experimentally hitherto unknown astatine azide, AtN₃, the heaviest of all halogen azides, is presented. The structure and the vibrational data of AtN₃ were computedab initio at RHF and electron-correlated MP2 levels of theory using a quasirelativistic (MWB) pseudopotential for astatine, where the basis functions for the valences andp electrons consist of the standard double- basis set. For nitrogen a standard 6-31G(d) basis was used. The molecule represents a true minimum (NIMAG=0) at all levels of theory applied and is predicted to exist in a planartrans bentC _s structure. Since hybrid functionals, which define the exchange functional as a linear combination of Hartree-Fock, local, and gradient-corrected exchange terms, are known to predict the experimental parameters best, we also computed astatine azide (At-N1-N2-N3) at the B3-LYP level; the results are as follows:d(At-N1)=2.267,d(N1–N2)=1.239,d(N2–N3)=1.146 å; (A1-N1-N2)=111.6, (N1-N2-N3)=171.9;v ₁,=157.4,v ₂=366.6,v ₃=559.0,v ₄=659.6,v ₅=1264.7,v ₆=2165.1 cm^–1 (unscaled). The heat of formation was computed at B3-LYP level to be H _f ^o (AtN₃)=+80 kcal mol^–1.     

Luminescence Spectral Properties of Europium(III) and Terbium(III) Complexes with Cinnamic Acid

Europium and terbium mixed-ligand complexes with cinnamic acid of composition Ln(Cin)₃· nD · xH₂O, where Ln = Eu³⁺or Tb³⁺, Cin is a cinnamate ion (C₆H₅CH=CHCOO^–), D = 1,10-phenantroline, 2,2"-dipyridyl, benzotriazole (n= 2, x= 0), triphenylphosphine oxide (n= 1, x= 2), or H₂O (n= 0 or 1, x= 0), were synthesized. The compounds were characterized by elemental analysis, IR and luminescence spectroscopy. The Stark structure of the ⁵ D ₀–⁷ F _j(j= 0, 1, 2) electronic transitions in the low-temperature luminescence spectra of europium complexes was analyzed. IR study has revealed a bidentate coordination of the cinnamate ion in the compounds.     

Kristallstruktur von Sulfamid,SO2(NH2)2

X-ray crystal structure analyses of sulfamide were carried out at 293 K and at 100 K:M=96.10, orthorhombic, Fdd2,Z=8,F(000)=400, Mo K, =0.71069 Å (graphite monochromator). A) 293 K:a=9.127 (1) Å,b=16.857 (5) Å,c=4.579 (1) Å,V=704.50 ų,d _x =1.812 Mgm^–3, =0.648 mm^–1,R=1.77%,R _w =1.94% (384 reflections, 33 parameters). B) 100K:a=9.059 (1) Å,b=16.780 (8) Å,c=4.517 (1) Å,V=686.63 ų,d _x =1.859 Mgm^–3, =0.665 mm^–1,R=1.78%,R _w =1.95% (404 reflections, 33 parameters). The sulfamide molecule shows at 293 K S-O and S-N distances of 1.429 (1) Å and 1.620 (1) Å, respectively, which are in agreement with IR data. Hydrogen positions could be determined from differenceFourier syntheses. Strong weakening of some intense low order reflections by extinction was observed, their anisotropy depends on the crystal and on temperature.

     

Structural and magnetic properties of the solid solution () YMn1−x(Cu3/4Mo1/4)xO3

Recently, the ferroelectromagnet YMnO₃ has been the focus of interest because it exhibits both antiferromagnetism (Néel temperature 80 K) and ferroelectricity (Curie temperature 914 K). There have been no reports of complete YMn_1−xM_xO₃ solid solutions in which substitution of the foreign M cation preserves the hexagonal P6₃cm structure. In contrast there exist several homeotypic phases with the general formula, Ln_1+nCu_nMO_3+3n (n=1 (M=Ti), 2 (M=V) and 3 (M=Mo); Ln: lanthanide). Several YMn_1−x(Cu_3/4Mo_1/4)_xO₃ compounds have been synthesized. The solid solution, from YMnO₃ (x=0) to YCu_3/4Mo_1/4O₃ (x=1) has been characterized by X-ray diffraction and transmission electron microscopy study. For 0<x<0.9, the compounds are found to crystallize in the non-centrosymmetric structure, space group P6₃cm, of YMnO₃. The Mn-free end member, x=1, crystallizes in a complex multiple cell, the superstructure being associated to Cu³⁺/Mo⁶⁺ cationic ordering. Dilution of the Mn³⁺ magnetic array by the paramagnetic (Cu²⁺) and diamagnetic (Mo⁶⁺) cations is found to decrease the antiferromagnetic ordering temperature and it becomes undetectable for x0.5 compositions.     

Properties of the perovskites, SrMn1−xFexO3−δ (x=1/3, 1/2, 2/3)

The SrMn_1−xFe_xO_3−δ (x=1/3, 1/2, 2/3) phases have been prepared and are shown by powder X-ray and neutron (for x=1/2) diffraction to adopt an ideal cubic perovskite structure with a disordered distribution of transition-metal cations over the six-coordinate B-site. Due to synthesis in air, the phases are oxygen deficient and formally contain both Fe³⁺ and Fe⁴⁺. Magnetic susceptibility data show an antiferromagnetic transition at 180 and 140 K for x=1/3 and 1/2, respectively and a spin-glass transition at 5, 25, 45 K for x=1/3, 1/2 and 2/3, respectively. The magnetic properties are explained in terms of super-exchange interactions between Mn⁴⁺, Fe^(4+δ)+ and Fe⁽³⁺⁾⁺. The XAS results for the Mn-sites in these compounds indicate small Mn-valence changes, however, the Mn-pre-edge spectra indicate increased localization of the Mn-e_g orbitals with Fe substitution. The Mössbauer results show the distinct two-site Fe⁽³⁺⁾+/Fe^(4+δ)+ disproportionation in the Mn- substituted materials with strong covalency effects at both sites. This disproportionation is a very concrete reflection of a localization of the Fe-d states due to the Mn-substitution.     

Electrical Conductance and Volumetric Studies in Aqueous Solutions of Nicotinic Acid

Conductivity measurements of nicotinic acid and sodium nicotinate in dilute aqueous solutions were performed in the (288.15 to 323.15) K temperature range. The limiting equivalent conductances of the nicotinate anion, λ⁰(Nic⁻, T), and the dissociation constants of nicotinic acid, K(T), were derived by the use of the Onsager and the Quint and Viallard conductivity equations. Densities of aqueous solutions with molalities lower than 0.2 mol-kg⁻¹ were determined at 5 K temperature intervals, from T = (288.15 to 333.15) K. The measured densities were used to evaluate the apparent molar volumes, V_{2, φ}(m, T), the cubic expansion coefficients, α(m, T), and the changes of isobaric heat capacities with respect to pressure, (∂C_P/∂p)_{T, m}. They were qualitatively correlated with the changes in the structure of water when nicotinic acid is dissolved in it.     

Kristallstruktur von Monosilber(I)amidosulfat,AgSO3NH2

A crystal structure analysis of the colourless AgSO₃NH₂ was carried out at room temperature:M=203.95, orthorhombic, Pcab,a=7.809 (2) Å,b=8.067 (2) Å,c=11.682 (3) Å,V=735.9 ų,Z=8,d _x=3.681 Mgm^–3,F(000)=760, Mo K, =0.71069 Å (graphite monochromator), =5.77 mm^–1,R=4.36% (509 reflections, 56 parameters). The ionic structure shows approximate trigonal bipyramidal coordination around the Ag⁺-ions.

     

An equilibrium and calorimetric investigation of the hydrolysis of L-tryptophan to (indole + pyruvate + ammonia)

Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the reaction L-tryptophan(aq) + H₂O(l) = indole(aq) + pyruvate(aq) + ammonia(aq) which is catalyzed by L-tryptophanase. High-pressure liquid-chromatography and microcalorimetery were used to perform these measurements. The equilibrium measurements were performed as a function of pH, temperature, and ionic strength. The results have been interpreted with a chemical equilibrium model to obtain thermodynamic quantities for the reference reaction: L-tryptophan(aq) + H₂O(l) = indole(aq) + pyruvate^–(aq) + NH ₄ ⁺ (aq). At T=25°C and I_m=O the results for this reaction are: K^o=(1.05±0.13)×10^–4, G°=(22.71±0.33) kJ-mol^–1, H°=(62.0±2.3) kJ-mol^–1, and S°=(132±8) J-K^–1-mol^–1. These results have been used together with thermodynamic results from the literature to calculate standard Gibbs energies of formation, standard enthalpies of formation, standard molar entropies, standard molar heat capacities, and standard transformed formation properties for the substances participating in this reaction.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

An X-ray study of the complex anionbis(N-hydroxy-iminodiacetate) vanadate(IV), a model for a vanadium-containing biologic compound

The structure of ammonium tetramethylammoniumbis(N-hydroxy-iminodiacetate)vanadate(IV) was determined by x-ray analysis. One independent anion and two cations were found in the asymetric unit. The crystal is monoclinic, space group C2/c, with a=15.820(9), b=16.450(6), c=16.311(4) å,=118.92(3) deg., V=3715(3) å³, Z=8, D_x=1.56g cm^–3,(M_o-K_a)=5.59 cm^–1, F(OOO)=2028, M=434.9 for C₁₂H₂₄N₄O₁₀V. The structure was solved and refined to R(F)=0.029 and R_w(F)=0.040.The complex anion does not contain the oxovanadium(IV) group, but contains vanadium(IV) as the central atom. This is the first example of a vanadium(IV) complex octacoordinated to nitrogen and oxygen atoms exhibiting a highly distorted dodecahedral geometry. The chelation is along twoa and fourg edges. As the angles ones are bonding distances (N—O, 1.381(3), 1.382(4) å) the angles around the central atom are very different from those usually observed in the dodecahedral complexes. The V—O distances range from 1.973(3) to 2.071(3) å and the V—N distances range from 2.002(3) to 2.003(4) å.     

Die Kristallstruktur von Ca9(Ca x Mg1−x )(AsO4)6(AsO3OH) mitx ∼ 0,5

The crystal structure of Ca₉(Ca _x Mg_1–x )(AsO₄)₆(AsO₃OH) withx 0.5 (a=10.73,c=37.74 Å; space group R3c-C _3v ⁶ ;Z=6) was solved from 985 independent X-ray intensities collected on a 4-circle diffractometer, and refined toR=5.7% for all data. This compound is isotypic to Ca₉Mg(PO₄)₆(PO₃OH), a structure of the whitlockite-type.

     

Crystal structure and IR spectrum of 1-O-α- -glucopyranosyl- -mannitol–ethanol (2/1)

1-O-α- -Glucopyranosyl- -mannitol–ethanol (2/1), (C₁₂H₂₄O₁₁)₂–C₂H₅OH, crystallizes in the monoclinic space group P2₁ with unit cell dimensions a=11.4230(8) Å, b=9.525(4) Å, c=15.854(2) Å, β=102.751(7)° and V=1682.4(7) ų, Z=2, D_x=1.45 Mg m⁻³, λ (Mo-K_α)=0.71069 Å, μ=0.128 mm⁻¹, F(000)=788 and T=293(2) K. The structure was solved by direct methods and refined by least-squares calculations on F² to R₁=0.0371[I>2σ(I)], and 0.0930 (all data, 3542 independent reflections, R_int=0.021). There are two molecules of glucopyranosylmannitol (GPM) and one ethanol molecule in the asymmetric unit, and the glucopyranosyl ring adopts a chair conformation in both GPM molecules. Bond lengths and angles accord well with the mean values of related structures. The conformation along the mannitol side chain for one of the GPM molecules was the same as for the known polymorphs of -mannitol, while the conformation of the other molecule was different, indicating different conformational arrangements in the terminal carbon atoms of the mannitol side chains of the two GPM molecules. The structure in 1-O-α- -glucopyranosyl- -mannitol–ethanol (2/1) is held together by a very complex hydrogen bonding system, which consists of an infinte chain propagating along the b-axis and a discontinuous chain, which binds the ethanol molecule to the structure. The FTIR spectra for anhydrous GPM, GPM dihydrate and GPM–ethanol (2/1) were recorded. Both IR and X-ray results indicate the extensive hydrogen bonding in crystalline state.     

Dielectric proprieties of ferroelectric ceramics derived from the system BaTiO3NaNbO3-based solid solutions

Dielectric studies performed on the solid solution Ba_1−xNa_xTi_1−xNb_xO₃ (BNTN) show that all compositions (x= 0.1, 0.15, 0.2, 0.4, 0.5 and 0.025, 0.05, 0.6, 0.7, 0.8) exhibit a ferroelectric–paraelectric phase transition where the Curie temperature is a function of the composition. The specimens with composition BNTN (x= 0.05, 0.1, 0.15, 0.2) have been refined by the Celref method from X-ray powder diffraction data. The evolution of dielectric constant as a function of temperature and frequency in the range 77–500 K and 20–2 × 10⁵ Hz, respectively, show that these ceramics present the classical ferroelectric character when 0x<0.075 and 0.55<x1 and relaxor character when 0.075x0.55.     

The ternary system cerium–palladium–silicon

Phase relations in the ternary system Ce–Pd–Si have been established for the isothermal section at 800 °C based on X-ray powder diffraction and EMPA techniques on about 130 alloys, which were prepared by arc-melting under argon or powder reaction sintering. Eighteen ternary compounds have been observed to participate in the phase equilibria at 800 °C. Atom order was determined by direct methods from X-ray single-crystal counter data for the crystal structures of τ₈—Ce₃Pd₄Si₄ (U₃Ni₄Si₄-type, Immm; a=0.41618(1), b=0.42640(1), c=2.45744(7) nm), τ₁₆—Ce₂Pd₁₄Si (own structure type, P4/nmm; a=0.88832(2), c=0.69600(2) nm) and also for τ₁₈—CePd_1−xSi_x (x=0.07; FeB-type, Pnma; a=0.74422(5), b=0.45548(3), c=0.58569(4) nm). Rietveld refinements established the atom arrangement in the structures of τ₅—Ce₃PdSi₃ (Ba₃Al₂Ge₂-type, Immm; a=0.41207(1), b=0.43026(1), c=1.84069(4) nm) and τ₁₃—Ce_3−xPd_20+xSi₆ (0≤x≤1, Co₂₀Al₃B₆-type, Fm3¯m; a=1.21527(2) nm). The ternary compound Ce₂Pd₃Si₃ (structure-type Ce₂Rh_1.35Ge_4.65, Pmmn; a=0.42040(1), b=0.42247(1), c=1.72444(3) nm) was detected as a high-temperature compound, however, does not participate in the equilibria at 800 °C. Phase equilibria in Ce–Pd–Si are characterized by the absence of cerium solubility in palladium silicides. Mutual solubility among cerium silicides and cerium–palladium compounds are significant whereby random substitution of the almost equally sized atom species palladium and silicon is reflected in extended homogeneous regions at constant Ce-content such as for τ₂—Ce(Pd_xSi_1−x)₂ (AlB₂-derivative type), τ₆—Ce(Pd_xSi_1−x)₂ (ThSi₂-type) and τ₇—CePd_2−xSi_2+x. The crystal structures of compounds τ₄—Ce_~8Pd_~46Si_~46, τ₁₂—Ce_~29Pd_~49Si_~22, τ₁₅—Ce_~22Pd_~67Si_~11, τ₁₇—Ce_~5Pd_~77Si_~18 and τ₁₈—CePd_1−xSi_x (x~0.1) are still unknown.     

Phases in the Al–Yb–Zn system between 25 and 50 at% ytterbium

Phases YbZn_1−xAl_x, YbZn_2−xAl_x and YbZn_3−xAl_x were studied by electron microprobe analysis and X-ray single crystal and powder methods. The compound YbZn_0.8Al_0.2 crystallizes with the CsCl-type, a=3.635(2) Å. Four phases were investigated by single crystal X-ray diffraction: YbZn_0.996(6)Al_1.004(6), MgNi₂-type, P6₃/mmc, a=5.573(1), c=18.051(3) Å, Z=8, wR2=0.040 and YbZn_0.88(3)Al_1.12(3), MgCu₂-type, , a=7.860(2) Å, Z=8, wR2=0.060, both showing mixed Zn/Al occupancy; YbZn_2.50(1)Al_0.50(1), CeNi₃-type, P6₃/mmc, a=5.496(1), c=17.336(2) Å, Z=6, wR2=0.036 and YbZn_1.92(2)Al_1.08(2), PuNi₃- or NbBe₃-type, , a=5.499(1), c=26.134(5) Å, Z=9, wR2=0.053, where the zinc atoms are ordered in the CaCu₅ segment, while share the sites with aluminium in the Laves phase segment. In the pseudobinary section YbZn_2−xAl_x four structures occur in sequence with increasing the electron concentration: CeCu₂ or KHg₂ (x=0–0.3), MgZn₂ (x=0.33–0.54), MgNi₂ (x=0.68–1.01) and MgCu₂ (x=1.12–2). This sequence agrees with the results of first-principles calculations, already reported in the literature for other similar series. In the YbZn_3−xAl_x section CeNi₃-type compounds occur with x=0.40–0.88 followed by PuNi₃-type compounds with x=0.92–1.10. The stability ranges of these phases are related to the valence electron concentration.     

Mechanosynthesis of nanopowders of the proton-conducting electrolyte material Ba(Zr, Y)O3−δ

The formation of perovskite nanopowders of the common proton-conducting, electrolyte material Ba(Zr_1−xY_x)O_3−δ is demonstrated by room temperature mechanosynthesis for the compositional range x=0, 0.058 and 0.148. This is achieved with a planetary ball mill at 650 rpm in zirconia vials, starting from BaO₂ with ZrO₂, (ZrO₂)_0.97(Y₂O₃)_0.03 or (ZrO₂)_0.92(Y₂O₃)_0.08 precursors, respectively. Powder X-ray diffraction (XRD) reveals the formation of the perovskite phase in the early stages of milling with phase purity being achieved after milling times of 240 min for composition x=0.058 whereas 420 min is necessary for composition x=0.148. In contrast, traces of ZrO₂ are apparent in composition x=0 even after milling times of 420 min. The use of BaCO₃ as precursor does not allow the formation of the perovskite phase for any composition. The perovskite crystallites are spherical in shape with an average size determined from XRD of ca. 30 nm in agreement with transmission electron microscopy observations. FTIR spectra demonstrate that contamination levels of BaCO₃ in the mechanosynthesized powders are very low. The spherical shape and nanoscale of the crystallites allow densification levels that are highly competitive when compared to BaZrO₃-based materials formed by alternative synthesis techniques documented in the literature.     

Insulator–metal transition in Nd0.8Na0.2Mn(1−x)CoxO3 perovskites

The electric and magnetic properties of the perovskites Nd_0.8Na_0.2Mn_(1−x)Co_xO₃ (0x0.2) prepared by the usual ceramic procedure were investigated. The insulator-to-metal-like (IM) transition, closely related to a ferromagnetic arrangement, was revealed for the composition of x=0.04 and a similar tendency was detected for x=0. The insulating behavior persists down to low temperatures for higher contents of cobalt ions in spite of the transition to the bulk ferromagnetism. The properties are interpreted in terms of the steric distortion, tilting of the Mn(Co)O₆ octahedra and the double-exchange interactions of the type Mn³⁺–O²⁻–Mn⁴⁺and Mn^3.5+δ–O²⁻–Co²⁺, respectively. Presence of antiferromagnetic domains in the ferromagnetic matrix for the most of cobalt-substituted samples is supposed.