Beata Cristóvão

Synthesis and characterization of CuII–LnIII (Ln = Ho, Tm, Yb, or Lu) complexes with N2O4-donor Schiff base ligand

The heterodinuclear complexes [CuLnL(NO3)2(H2O)3MeOH]NO3·MeOH (Ln = Ho (1), Tm (2), Yb (3), and Lu (4); L = N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine) have been synthesized and characterized by elemental analysis, FTIR, thermogravimetric (TG)/differential scanning calorimetry (DSC), TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The isostructural compounds crystallized in the monoclinic space group P21/n. The rare earth(III) cation is nine coordinate, whereas the coordination number for copper(II) is six. The complexes were stable at room temperature. The thermal decomposition products were mainly CH3OH, H2O, CH3Br, NOx (x = 1 or 2), CO2, and CO. The magnetic properties of 1–3 were dominated by the crystal field effect on the LnIII site, masking the magnetic interaction between the paramagnetic centers. The CuII–LuIII pair in 4 showed no significant interaction, which is in accord with the diamagnetic nature of the ground state for lutetium(III). Graphical Abstract The heterodinuclear compounds [CuLn(L)(NO3)2(H2O)3MeOH]NO3·MeOH (where Ln = Ho (1), Tm (2), Yb (3), and Lu (4)) have been synthesized and characterized by elemental analysis, FTIR, TG/DSC, TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The complexes are isostructural and crystallize in the monoclinic space group P21/n. The magnetic properties of 1, 2, and 3 are dominated by the crystal field effect on the LnIII site, masking the magnetic interaction between the paramagnetic centers.

Physico-chemical properties of 3-methoxy-2-nitrobenzoates of some rare earth elements(III)

The complexes of 3-methoxy-2-nitrobenzoates of Pr(Ⅲ),Nd(Ⅲ),Sm(Ⅲ),Eu(Ⅲ),Gd(Ⅲ),Tb(Ⅲ),Er(Ⅲ) and Tm(Ⅲ) with the formula:Ln(CsH6NO5)3·2H2O,where Ln=lanthanides(Ⅲ),were synthesized and characterized by elemental analysis,Forier transform irtrared (FTIR) spectroscopy,magnetic and thermogravimetric studies and also by X-ray diffraction (XRD) measurements.The complexes had colours typical for Ln(Ⅲ) ions.The carboxylate groups bound as bidentate chelating.On heating to 1173 K in air they decomposed in the same way,at first,dehydrated in one step to anhydrous salts,and then decomposed to the oxides of respective metals with intermediate formation of the oxycarbonates.The enthalpy values of the dehydration process changed from 133.72 to 44.50 kJ/mol.Their solubility in water at 293 K was of the order of 10-4 mol/dm3.The magnetic moments of analysed complexes were determined by Gouys method in the range of 76-303 K.

Asymmetry in propeller-like trinuclear diphenoxo-bridged CuII–LnIII–CuII (Ln = La, Pr, Nd) Schiff base complexes – synthesis, structure and magnetic properties

Neutral heterotrinuclear complexes 2{[Cu2Ln(H2L)2(NO3)3]}·6CH3OH (Ln = La (1), Nd (2)) and [Cu2Ln(H2L)2(NO3)3]·4CH3OH·2H2O (Ln = Pr (3)) were obtained in the reaction of N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane (H4L = C17H18N2O4) with the respective salts of LnIII and CuII. Compounds 1–3 have similar coordination units and display asymmetry in the degree of planarity of the bridging CuO2Ln fragments, which is unusual for CuII–LnIII–CuII complexes. The geometry of the obtained complexes has been compared to the structural data of other 3d–4f–3d trinuclear diphenoxo-bridged complexes. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate that the interaction between CuII and LnIII ions is antiferromagnetic for Ln = Pr (2) and Nd (3), whereas in 1 the CuII–LaIII pairs show no significant interaction, which is in accord with the non-magnetic nature of the ground state for lanthanum(III).

INVESTIGATION OF SOME PHYSICOCHEMICAL PROPERTIES OF 4-NITROCINNAMATES OF LANTHANIDES(III)

ABSTRACT Lanthanide(III) 4-nitrocinnamates were synthesized as polycrystalline hydrated solids with the general formulae: Ln(C 9 H 6 NO 4 ) 3 ·nH 2 O (where Ln = lanthanons (without Ce(III)), n=1 for La, Pr-Tb and n=2 for Dy-Lu). The complexes were characterized by elemental analysis, FTIR spectroscopy, magnetic and thermogravimetric studies and also by X-ray diffraction (XRD) measurements. The carboxylate groups bind as bidentate chelating. On heating to 1173 K in air all compounds at first dehydrate in one stage to form anhydrous salts, that next with rising temperature are being directly decomposed (complexes of Pr(III) and Eu(III)) or with the intermediate formation of oxycarbonates (the rest of analysed compounds) to the oxides of respective metals. The gaseous products of compound thermal decomposition in nitrogen were also determined. The magnetic susceptibilities were measured over the ranges 76-303 K and 1.8-303 K, and their magnetic moments were calculated. The results show that 4-nitrocinnamates of lanthanides(III) are high-spin complexes with weak ligand field.

Synthetic, Structural, and Spectroscopic Characterization of a Novel Family of High-Spin Iron(II) [(β-Diketiminate)(phosphanylphosphido)] Complexes

This work describes a series of iron(II) phosphanylphosphido complexes. These compounds were obtained by reacting lithiated diphosphanes R2PP(SiMe3)Li (R = t-Bu, i-Pr) with an iron(II) β-diketiminate complex, [LFe(μ2-Cl)2Li(DME)2] (1), where DME = 1,2-dimethoxyethane and L = Dippnacnac (β-diketiminate). While the reaction of 1 with t-Bu2PP(SiMe3)Li yields [LFe(η1-Me3SiPP-t-Bu2)] (2), that of 1 with equimolar amounts of i-Pr2PP(SiMe3)Li, in DME, leads to [LFe(η2-i-Pr2PPSiMe3)] (3). In contrast, the reaction of 1 with (i-Pr2N)2PP(SiMe3)Li provides not an iron-containing complex but 1-[(diisopropylamino)phosphine]-2,4-bis(diisopropylamino)-3-(trimethylsilyl)tetraphosphetane (4). The structures of 2-4 were determined using diffractometry. Thus, 2 exhibits a three-coordinate iron site and 3 a four-coordinate iron site. The increase in the coordination number is induced by the change from an anticlinal to a synclinal conformation of the phoshpanylphosphido ligands. The electronic structures of 2 and 3 were assessed through a combined field-dependent 57Fe Mössbauer and high-frequency and -field electron paramagnetic resonance spectroscopic investigation in conjunction with analysis of their magnetic susceptibility and magnetization data. These studies revealed two high-spin iron(II) sites with S = 2 ground states that have different properties. While 2 exhibits a zero-field splitting described by a positive D parameter (D = +17.4 cm-1; E/D = 0.11) for 3, this parameter is negative [D = -25(5) cm-1; E/D = 0.15(5)]. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations provide insights into the origin of these differences and allow us to rationalize the fine and hyperfine structure parameters of 2 and 3. Thus, for 2, the spin-orbit coupling mixes a z2-type ground state with two low-lying {xz/yz} orbital states. These interactions lead to an easy plane of magnetization, which is essentially parallel to the plane defined by the N-Fe-N atoms. For 3, we find a yz-type ground state that is strongly mixed with a low-lying z2-type orbital state. In this case, the spin-orbit interaction leads to a partial unquenching of the orbital momentum along the x axis, that is, to an easy axis of magnetization oriented roughly along the Fe-P bond of the phosphido moiety.

Heterometallic ZnII–LnIII–ZnII Schiff Base Complexes with Linear or Bent Conformation—Synthesis, Crystal Structures, Luminescent and Magnetic Characterization

A series of racemic, heteronuclear complexes [Zn2Nd(ac)2(HL)2]NO3·3H2O (1), [Zn2Sm(ac)2(HL)2]NO3·3CH3OH·0.3H2O (2), [Zn2Ln(ac)2(HL)2]NO3·5.33H2O (3–5) (where HL is the dideprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diamino-2-propanol, ac = acetate ion, and Ln = Eu (3), Tb (4), Dy (5), respectively) with an achiral multisite coordination Schiff base ligand (H3L) were synthesized and characterized. The X-ray crystallography revealed that the chirality in complexes is centered at lanthanide(III) ions due to two vicinally located μ-acetato-bridging ligands. The presented crystals have isoskeletal coordination units but they crystallize in monoclinic (1, 2) or trigonal crystal systems (3–5) with slightly different conformation. In 1 and 2 the ZnII–LnIII–ZnII coordination core is linear, whereas in isostructural crystals 3–5 the chiral coordination cores are bent and lie on a two-fold axis. The complexes 1, 3–5 show a blue emission attributed to the emission of the ligand. For ZnII2SmIII complex (2) the characteristic emission bands of f-f* transitions were observed. The magnetic properties for compounds 1, 4 and 5 are characteristic for the paramagnetism of the corresponding lanthanide(III) ions.

Crystal structures of 5-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Zn(II)

The crystal and molecular structures of [bis(5-chloro-2-methoxybenzoate)tetraaquamanganese(II)], [pentaaqua(5-chloro-2-methoxybenzoato)cobalt(II)] (5-chloro-2-methoxybenzoate), [pentaaqua(5-chloro-2-methoxybenzoato)nickel(II)] (5-chloro-2-methoxybenzoate) and [aquabis(5-chloro-2-methoxybenzoate)zinc(II)] monohydrate were determined by a single-crystal X-ray analysis. Mn(H2O)4L2 (where L = C8H6ClO3) crystallizes in the monoclinic system, space group P21/c. [Co(H2O)5L]L and [Ni(H2O)5L]L both are isostructural, space group P212121. The crystals of [Zn(H2O)L2] H2O are monoclinic, space group Pc. Mn(II) ion is positioned at the crystallographic symmetry center. Mn(II) and Co(II) ions adopt the distorted octahedral coordination but Zn(II) tetrahedral one.The carboxylate groups in the complexes with M(II) cations function as monodentate, bidentate and/or free COO-groups. The ligands exist in the crystals as aquaanions. The complexes of 5-chloro-2-methoxybenzoates with Mn(II), Co(II) and Zn(II) form bilayer structure.

Magnetic, Spectral, and Thermal Behaviour of 2-Chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II)

Some physicochemical properties of 2-chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono-and dihydrates with a metal ion—ligand mole ratio of 1: 2. All complexes are polycrystalline compounds. Their colours depend on the kind of central ion: pink for Co(II) complex, green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293 K–523 K because it was found that on heating in air above 523 K 2-chloro-4-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step. During dehydration process no transformation of the nitro group to nitrito one took place. Their solubilities in water at 293 K are of the orders of 10−3-10−2 mol dm−3. The magnetic moment values of 2-chloro-4-nitrobenzoates determined in the range of 76 K–303 K change from 3.48µB to 3.82µB for Co(II) complex, from 2.24µB to 2.83µB for Ni(II) 2-chloro-4-nitrobenzoate, and from 0.31µB to 1.41µB for Cu(II) complex. 2-Chloro-4-nitrobenzoates of Co(II) and Ni(II) follow the Curie—Weiss law, but the complex of Cu(II) forms dimer.

Structural, Luminescent and Thermal Properties of Heteronuclear PdII–LnIII–PdII Complexes of Hexadentate N2O4 Schiff Base Ligand

New PdII–LnIII–PdII complexes of hexadentate N2O4 Schiff base ligand (H4L: N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane) with Eu (1), Tb (2), Er (3) and Yb (4) ([Pd2Eu(H2L)2NO3](NO3)2∙2H2O∙2CH3OH 1, [Pd2Ln(H2L)2H2O](NO3)3∙3H2O, where Ln = Tb 2, Er 3, [Pd2Yb(H2L)2H2O](NO3)3∙5.5H2O 4) were synthesized and characterized structurally and physicochemically by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC) and luminescence measurements. The compounds 1–4 are built of cationic heterometallic PdII–LnIII–PdII trinuclear units. The palladium(II) centers adopt a planar square geometry occupying the smaller N2O2 cavity of the Schiff base ligand. The lanthanide(III) is surrounded by two Schiff base ligands (eight oxygen atoms) and its coordination sphere is supplemented by a chelating bidentate nitrate ion in 1 or by a water molecule in 2–4. The complexes have a bent conformation along the PdII–LnIII–PdII line with valence angles in the ranges of 162–171°. The decomposition process of the complexes results in mixtures of: PdO, Pd and respective lanthanide oxides Eu2O3, Tb2O3, Tb4O7, Er2O3, Yb2O3. The luminescent measurements show low efficiency intramolecular energy transfer only in the complex of terbium(III) (2).

New complexes of 4-[(4-fluorophenyl)amino]-4-oxobut-2-enoic acid with selected transition metal ions: Synthesis, thermal, and magnetic properties

Complexes of 4-[(4-fluorophenyl)amino]-4-oxobut-2-enoic acid, HL, with Mn(II), Co(II), Ni(II), Cu(II), Nd(III), Gd(III), and Er(III) were synthesized and characterized by various physico-chemical methods: elemental analysis, FT-IR, TG, DTG, DSC, TG/FT-IR, XRF, XRD, and magnetic measurements using the Gouy’s method and a SQUID-VSM magnetometer. The complexes were found to be hydrates (except Er(III) complex) containing 1 to 4 molecules of water. The carboxylate groups acted as bidentate ligands.