Zdirad Žák

Trinuclear magnetic clusters based on cyanide metal complexes: synthesis, crystal structures, and magnetic properties of four new [MnII2MIII] complexes (M = Cr, Fe, Co)

Four new cyano-bridged [MnIIMIIIMnII] heterotrinuclear complexes (MIII = Cr, Fe, Co) have been synthesized and crystallographically characterized: {[(H2O)L1Mn–NC–Cr(CN)4–CN–MnL1(H2O)]}3[Cr(CN)6]·10H2O 1, [(H2O)L2Mn–NC–M(CN)4–CN–MnL2(NCS)]·2H2O 2, [(H2O)L2Mn–NC–Fe(CN)4–CN–MnL2(H2O)](NCS)·1.5H2O 3, and [(H2O)L2Mn–NC–Co(CN)4–CN–MnL2(H2O)](NCS)·1.5H2O 4 (L1 = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, L2 = 2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene). The crystal structure of 1 consists of independent [MnCrMn] monocations whose charges are counterbalanced by [Cr(CN)6]3− anions. The crystal structure of 2 consists of neutral heterotrinuclear [MnCrMn] species, with the isothiocyanato ion coordinated to one of the manganese atoms. Compounds 3 and 4 are isomorphous. Their crystal structure consists of centrosymmetric [MnMMn] entities, uncoordinated NCS− ions, and solvent molecules. The magnetic properties of the four complexes have been investigated. Compounds 1 and 2 are new examples of systems with an irregular spin state structure, exhibiting the characteristic minimum on the the χMTversusT curves. The exchange interaction between the chromium(III) and the manganese(II) ions is antiferromagnetic (1: J = −9.8 cm−1; 2: J = −6.52 cm−1). For compound 3, the exchange interaction between manganese(II) and iron(III) was found to be ferromagnetic.

Syntheses and crystal structures of some new rare earth basic nitrates II: [Ln6O(OH)8(H2O)12(NO3)6](NO3)2·xH2O, Ln=Sm, Dy, Er; x(Sm)=6, x(Dy)=5, x(Er)=4

Abstract The title compounds were synthesized and their structures determined. The samarium compound crystallizes with a new structure type: P-1, a=11.595(2), b=11.697(2), c=16.720(3)A, α=91.05(2), β=90.00(1), γ=112.97(2)°, V=2087.5(6) A3, Z=2. The dysprosium compound is isotypic with the previously reported structure of the gadolinium compound: C2/c, a=12.623(3), b=18.798(4), c=17.465(4)A, β=106.70(2)°, V=3969.4(16) A3, Z=4. The erbium compound has the same structure as the earlier reported structure of the ytterbium compound: P-1, a=10.056(2), b=10.064(2), c=11.397(2)A, α=96.49(1), β=108.81(1), γ=110.90(2)°, V=985.5(3) A3, Z=1. The structures, which are closely related, are built up of [Ln6O(OH)8(H2O)12(NO3)6]2+ clusters with additional (NO3)1− and H2O groups in between.

Preparation, structure and magnetic properties of two tetracyanonickellates: one-dimensional Ni(dien)(mea)Ni(CN)4 and ionic [Ni(aepn)2][Ni(CN)4].H2O

Two new homobimetallic compounds Ni(dien)(mea)Ni(CN) 4 (NDMC) and [Ni(aepn) 2 ][Ni(CN) 4 ].H 2 O (NANCH) were prepared and characterised for the first time (dien = diethylenetriamine, mea = 2-aminoethanole, aepn = N-(2-aminoethyl)-1,3-propanediamine). NDMC exhibits a novel type of one-dimensional structure which is formed of [Ni(dien)(mea)] 2 + cations (C) and planar [Ni(CN) 4 ] 2 - anions (A) linked by bridging cyano groups. The anion utilises cis-positioned cyano groups for bridging to two different cations and these complete a distorted square bipyramid of the cation. The crystal structure consists of 1D chains {...- 3 C 6 - 1 A 4 - 3 C 6 - 1 A 4 -...} x where the spin multiplicity is marked as a superscript and the coordination number as a subscript. A considerable local magnetic anisotropy was found (D/hc = -7.0 cm - 1 ) owing to the synergy effect of the ligand sphere asymmetry around the cation. NANCH is formed of isolated [Ni(aepn) 2 ] 2 + cations ( 3 C 6 ), which are hexacoordinate (S=1), and planar diamagnetic [Ni(CN) 4 ] 2 - anions ( 1 A 4 ) which are linked by water molecules via hydrogen bonds forming chain of the type {... 1 A 4 ...HOH...} x . The magnetic anisotropy dropped significantly owing to a nearly octahedral {NiN 6 } chromophore.

Novel thermal tetracyclization by intramolecular azine criss-cross addition

An easy, thermally initiated reaction of homoallenylazine 1 affords the new fused heterocyclic system 2 consisting of four five-membered rings in ten-membered carbocycle around the hydrazine moiety.

Synthesis, properties and crystal structures of R[MIII(bdt)2] complexes (M = Ni, Co, Cu)

New nickel, cobalt and copper complexes with benzene-1,2-dithiole (bdt), of general formula R[M(bdt)2]: M = Ni, Co and Cu; R = Me4N, Et4N, Pr4N, Me3PhN, MePh3P, Ph4P have been synthesized and characterized by standard physico-chemical methods (elemental analyses, magnetochemical and conductivity measurements, i.r. and u.v.–;vis. spectroscopy). X-ray structural analysis of (MePh3P)[M(bdt)2], M = Ni, Co and Cu, confirms that the MS4 chromophore lies in a slightly distorted square coordination arrangement around the central atom. The three complexes have also been studied by cyclic voltammetry.

Novel polymeric metal complexes of calix[4]arene-11,23-diphosphonic acid: synthesis and structure determination

New calixarene derivatives bearing two phosphonic acid groups, 25,27-dimethoxy-26,28-dihydroxycalix[4]arene-11,23-diphosphonic acid 3 and its tetraethyl ester 2 were synthesized. Their X-ray structures confirmed cone conformation of the molecules, more deformed for the ester due to bulky ethyl groups. Complexes [CaH 2 L(MeOH) 2 ]·4 MeOH ( 4 ) and [LnH 2 L(NO 3 )(H 2 O) 2 ]·2 H 2 O 2 MeOH (Ln=La(III), Pr(III), Nd(III), H 4 L=26,28-dihydroxy-25,27-dimethoxycalix[4]arene-11,23-diphosphonic acid) were also prepared. Structures of the Ca(II) complex 4 and Nd(III) complex 5 were determined by X-ray analysis. The structural motif of 4 is similar to that found for the free acid 3 . The calixarenes are linked by coordination of phosphonates to Ca(II) in a polymeric structure instead of a network of hydrogen bonds in 3 . Structure of 5 is different: four calixarene molecules are linked through coordination to Nd(III) in a supramolecular macroring, which forms a pore (approximately 17 A in diameter) penetrating through the structure.

Oxalato complexes of copper(II) with chelating diamines. Crystal structure of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2

Abstract Four new oxalato complexes of copper(II) of composition [Cu(dmen)ox(H2O)]2 [Cu(dmen)2](ClO4)2 (1) (dmen=N,N-dimethylethylenediamine, H2ox=oxalic acid), [(Cu(dmen)H2O)2ox](ClO4)2·H2O (2), [Cu(tmen)(H2O)(ox)Cu(aep)(H2O)](ClO4)2 (3) (tmen=N,N,N′,N′-tetramethylethylenediamine, aep=2-(2-aminoethyl)pyridine) and [(Cu(dben)NO3)2ox] (4) (dben=N,N′-dibenzylethylenediamine) have been prepared and characterised by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dmen)ox(H2O)]2[Cu(dmen)2](ClO4)2 (1) has been determined by single-crystal X-ray analysis. The structure of 1 contains a neutral [Cu(dmen)ox(H2O)] complex, a cationic [Cu(dmen)2]2+ complex and perchlorate anions. The copper(II) atom of the neutral [Cu(dmen)ox(H2O)] unit possesses a distorted square-pyramidal environment with two oxygen atoms of oxalate and two nitrogen atoms of dmen in the basal plane and an oxygen atom of a water molecule in the apical position. The copper(II) atom of the cationic [Cu(dmen)2] unit shows a square-planar environment with four donor nitrogen atoms of two molecules of dmen. The temperature dependence of magnetic susceptibility for compounds 2–4 was measured. Magnetochemical measurements show that copper(II) ions in compounds 2–4 are antiferromagnetically coupled through the oxalate bridge, J=−157, −175 and −167 cm−1 (H=−2JS1S2, S1=S2=1/2) for 2, 3 and 4, respectively.

Configurations and conformations of sanguinarine and chelerythrine free bases stereoisomers

Abstract The configurations and conformations of bimolecular aminoacetals of benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine were investigated by NMR spectroscopy, quantum chemical calculations, and X-ray analysis. The results of the complete computational conformational analysis, the calculation of the chemical shielding of the considerably populated conformers, the determination of averaged chemical shifts and comparison with experimental NMR chemical shifts observed in solution are reported. Based on these results, the relative configurations at the stereogenic centers of two diastereomers of bis(dihydrosanguinarinyl) ether were determined. The structure of the major diastereomer of bis(dihydrosanguinarinyl) ether was confirmed by X-ray analysis and specified for the solid state.

Molecular and Crystal Structures of Three Berberine Derivatives

Berberine azide, berberine thiocyanate, and 8-cyano-8H-berberine were prepared from berberine chloride, a quaternary protoberberine alkaloid. The molecular and crystal structures of all compounds are reported and discussed.

Hexakis[3-(aminocarbonyl)pyridinium] decavanadate(V) dihydrate.

The structure of the title compound, (C(6)H(7)N(2)O)(6)[V(10)O(28)].2H2O, at 120 (2) K has monoclinic (C2/c) symmetry. The asymmetric unit consists of one half-decavanadate anion of Ci symmetry, three cations and one water molecule. Each water molecule is hydrogen bonded to two decavanadate anions, thus forming a one-dimensional chain of anions. The three-dimensional supramolecular structure is formed by a network of N-H...O, O-H...O and C-H...O hydrogen bonds, in which the cations, anions and water molecules are involved, and by nonparallel-displaced pi-stacking interactions between pyridine rings. As a result of hydrogen bonding, the carboxamide groups of the cations are somewhat twisted from the pyridine ring plane.