Single crystals of [NH3C2H5][Gd(Cl2HCCOO)4] have been obtained by reaction of Gd2O3 with NH3C2H5Cl in an aqueous solution of Cl2HCCOOH. The compound crystallizes in the triclinic space group P1¯ (no. 2, Z=2, a=813.7(3)pm, b=1246.9(4)pm, c=1263.9(4)pm, α=61.67(4)°, β=87.39(4)°, γ=84.84(4)°). The Gd3+ ion is eight-fold coordinated by oxygen atoms. The magnetic behavior of the compound was investigated in the temperature range of 1.72–300K. The magnetic data indicate an intramolecular ferromagnetic interaction within a dimeric unit (Jintra=+0.029cm−1) on which an intermolecular antiferromagnetic interaction is imposed (Jinter=−0.010cm−1).

Single crystals of [NH3CH3][Gd(Cl2HCCOO)(4)] have been obtained by reaction of Gd2O3 with NH3CH3Cl in an aqueous solution of Cl2HCCOOH. The compound crystallizes in the triclinic space group P (1) over bar (No. 2, Z = 2, a = 811.5 pm, b = 1228.4 pm, c = 1228.9 pm, alpha = 62.43degrees, beta 87.67degrees, gamma = 84.48degrees). The Gd3+ ions are connected to chains by carboxylate groups. The chains can be considered to consist of dimeric units as two different Gd3+-Gd3+ distances appear. The magnetic behaviour of the compound was investigated in the temperature range of 1.77 to 300 K. The magnetic data indicate an intramolecular ferromagnetic interaction within the dimeric unit (j(intra) = +0.023 cm(-1)) on which an intermolecular antiferromagnetic interaction is imposed (J(inter) = -0.007 cm(-1)).

Single crystals of Gd(CF2HCOO)(3)(phen) have been obtained by reaction of Gd(CF2HCOO)(3)(H2O)(2)center dot H2O with 1,10-phenanthroline in a solution of ethanol and water. The compound crystallizes in the triclinic space group P (1) over bar (Nr, 2, Z = 2, a 874.6(2) pm, b = 928.9(l) pm, c = 1338.5(2) pm, alpha = 104.73 degrees, beta = 106.96 degrees, gamma = 99.92 degrees). The Gd3+ ions are bridged by carboxylate groups to dimers and are ninefold coordinated by seven oxygen and two nitrogen atoms. The magnetic behaviour of the compound was investigated in the temperature range of 1.76 to 300 K. The magnetic data indicate an antiferromagnetic interaction within the dimeric unit (J(ex) = -0.016 cm(-1)).

Abstract Rules are pointed out to protect the magnetochemist from pitfalls in both measurement and interpretation of magnetic data. Carefully chosen magnetic field strengths during magnetic susceptibility measurements guarantee the recording of genuine data. With the help of examples, the effect of too strong applied fields is demonstrated producing magnetic saturation and, for example, quenching of weak ferro- or antiferromagnetic spin–spin couplings. In consequence, the data run the risk of being misinterpreted unless model susceptibility equations are applied that take the field dependence of χ m into consideration. Recommendations are given for the presentation of experimental and theoretical data. The limited applicability of the most overworked formula in paramagnetism, the Curie–Weiss law χ m = C/(T–θ), is clearly presented (magnetically condensed systems, pure spin magnetism). While rough and ready susceptibility formulae are applicable to specific 3d and 4f systems, the complex situation for the remaining d and f centers, including actinides, demands computer programs which consider simultaneously interelectronic repulsion, ligand field potential, spin-orbit coupling, interatomic exchange interactions, and applied magnetic field.

Single crystals of Gd-2(Cl3CCOO)(6)(bipy)(2) x (H2O)(2) (.) 4 bipy, Pr(Cl3CCOO)(3)(bipy)(2), Nd(Cl3CCOO)(3) x (bipy)(2) and Er(Cl3CCOO)(3)(bipy)(2)(H2O) have been obtained by reaction of the corresponding trichloroacetate salts with 2,2'-bipyridyl (bipy) in a water/ethanol (1 : 1) solution. Gd-2(Cl3CCOO)(6)(bipy)(2)(H2O)(2) (.) 4 bipy crystallizes in the monoclinic space group P2(1)/c (no. 14, Z = 4, a = 1642.40(9) pm, b = 1227.36(10) pm, c = 2303.48(14) pm, beta = 107.043(7)degrees). The Gd3+ ions are bridged to dimers by carboxylate groups and are surrounded by six oxygen and two nitrogen atoms. One 2,2'-bipyridyl molecule is coordinated to Gd3+, the two other ones are non-coordinated.The monomeric compounds Ln(Cl3CCOO)(3)(bipy)(2) (Ln = Pr, Nd) are isotypic with each other and crystallize in the triclinic space group P (1) over bar (no. 2, Z = 2, Pr: a = 989.83(8) pin, b 1032.22(8) pin, c = 1791.56(13) pm, a = 99.312(9)degrees, beta = 102.036(9)degrees, gamma = 99.166(9)degrees; Nd: a = 990.09(7) pm, b = 1030.74(8) pm, c = 1788.70(13) pm, a = 99.393(9)degrees, beta = 102.064(8)degrees, gamma = 99.242(9)degrees). The Ln(3+) atom is Surrounded by six oxygen and four nitrogen atoms. A chelating coordination by the carboxylate groups is observed. There are two 2,2'-bipyridyl molecules coordinated to Ln(3+).The compound Er(Cl3CCOO)(3)(bipy)(2)(H2O) crystallizes in the triclinic space group P (1) over bar (no. 2, Z = 2, a = 1060.65(9) pm, b = 1273.35(11) pm, c = 1402.49(11) pm, a = 105.484(10)degrees, beta = 104.504(9)degrees, gamma = 93.712(10)degrees). The Er3+ ion is coordinated by four oxygen and four nitrogen atoms. There are two 2,2'-bipyridyl molecules attached to Er3+.

Single crystals of the title compound have been obtained by reaction of Gd-3(CIH2CCOO)(9)(H2O)(5) with 2,2'-bipyridyl (bipy) in a solution of ethanol and water. Gd-2(CIH2CCOO)(6)(bipy)(2) crystallises in the triclinic space group P1 (Z = 2) with a = 959.5(3) pm, b = 980.9(3) pm, c = 1163.9(4) pm, a = 68.67(3) degrees, beta = 84.82(4)degrees and gamma = 82.47(4)degrees. The crystal structure is built up of discrete molecules of dinuclear Gd3+-Gd3+ units. The corresponding residual (all data) for the refined structure is 4.46%. The magnetic behaviour of the compound was investigated in the temperature range of 1.76-300 K. The magnetic data were interpreted considering exchange interactions within the dimeric unit (J(ex) = -0.020 cm(-1)). ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Single crystals of Gd(HF2CCOO)3(H2O)2·H2O have been obtained by reaction of Gd2O3 with HF2CCOOH in water. Data collection was carried out using a STOE imaging plate diffractometer at 173K. The compound crystallizes in the triclinic space group P1̄ (Z=2) with a=833.1(2)pm, b=943.5(2)pm, c=944.9(2)pm; α=66.78(3), β=79.54(3) and γ=77.61(3). The corresponding residual (all data) for the refined structure is 2.98%. The magnetic behaviour of the compound was investigated in the temperature range of 1.7–300K. The magnetic data were interpreted considering exchange interaction effects in the dinuclear Gd3+–Gd3+ unit. The exchange coupling constant J=−0.024cm−1 indicates antiferromagnetic interaction, whereas J=+0.05cm−1 for Gd(H3CCOO)3(H2O)2·2H2O a ferromagnetic one.

Single crystals of Ln(ClF2CCOO)(3)(H2O)(3) (Ln = Gd, Dy, Ho, Er) have been obtained by reaction of Ln(2)O(3) with an aqueous solution of ClF2CCOOH. The compounds are isotypic with each other and crystallize monoclinically in the space group P 2(1)/c (No. 14; Z = 4) with the following lattice constants, e.g. Gd(ClF2CCOO)(3)(H2O)(3): a = 927.9(3) pm, b = 1923.8(4) pm, c = 1037.2(4) pm, beta = 114.21(4)degrees. In the crystal structures the lanthanide ions are bridged by carboxylate groups to dimers and are eightfold coordinated by oxygen atoms. The magnetic behaviour of Gd(ClF2CCOO)(3)(H2O)(3) was investigated in the temperature range of 1.73 to 300 K. The magnetic data indicate weak antiferromagnetic interactions within the dimeric unit.

Single crystals of Gd(HF2CCOO)(3)(H2O)(2).H2O have been obtained by reaction of Gd2O3 with HF2CCOOH in water. Data collection was carried out using a STOE imaging plate diffractometer at 173 K. The compound crystallizes in the triclinic space group P (1) over tilde (Z = 2) with a = 833.1(2) pm, b = 943.5(2) pm, c = 944.9(2) pm; alpha = 66.78(3), beta = 79.54(3) and gamma = 77.61(3). The corresponding residual (all data) for the refined structure is 2.98%. The magnetic behaviour of the compound was investigated in the temperature range of 1.7-300 K. The magnetic data were interpreted considering exchange interaction effects in the dinuclear Gd3+-Gd3+ unit. The exchange coupling constant J = -0.024 cm(-1) indicates antiferromagnetic interaction, whereas J = +0.05 cm(-1) for Gd(H3CCOO)(3)(H2O)(2).2H(2)O a ferromagnetic one. (C) 2003 Elsevier B.V. All rights reserved.

Single crystals of the title compound were prepared from the elements by a solid state reaction in an iodine atmosphere. Data collection were carried out using a STOE image plate detector at 293 K. The compound crystallizes in the space group P2(1)/n of the monoclinic system isotypically to Tb-4[SiS4](3) with four formular units in cells of dimensions: a = 986.7(2)pm, b=1099.69(19)pm, c = 1646.2(4) pm, beta = 102.67(3)degrees. The corresponding residual (all data) for the refined structure is 3.09%.The magnetic behavior of the compound was investigated on powdered samples in a temperature range between 1.7 and 300 K. The deviations from the Curie-behavior could be interpreted by the molecular field approach. (C) 2003 Elsevier Science (USA). All rights reserved.

The magnetism of the three compounds Pr3X[SiS4]2 (X=Cl, Br, I) has been measured in the temperature range between 1.7 and 300K. For the theoretical calculations to interpret the magnetic behavior the angular overlap model was employed to reproduce the ligand field influence and the molecular field approach to take magnetic interaction into account.

Single crystals of Nd3ClS2[SiS4] were prepared from the. elements. Data collection was carried out using a STOE image plate detector at 293 K. The compound crystallizes in the orthorhombic space group Pnma with eight familiar units in a cell of dimension:a = 1240.3 (2), b = 1035.8 (2), c = 1616.4 (3) pmThe corresponding residual (all data) for the refined structures is 3.45%. In the crystal structure, the chloride ions form chains along [010] with trigonal coordination by the lanthanide ions.The magnetic behavior of powdered crystals was interpreted by ligand field calculations where the influence of the ligand field was taken into account by applying the angular overlap model and magnetic exchange by the molecular field approximation. (C) 2002 Elsevier Science Ltd. All rights reserved.

On the Hydrate Isomer Gd 3 (H 2 ClCCOO) 9 (H 2 O) 5 Single crystals of Gd 3 (H 2 ClCCOO) 9 (H 2 O) 5 have been obtained by reaction of Gd 2 O 3 with an aqueous solution of H 2 ClCCOOH. The compound crystallizes in the monoclinic space group P 2 1 / a ( Z = 4, a = 1438.2(3), b = 1870.2(4), c = 1475.9(3) pm, β = 95.37(2)°). There are three kinds of crystallographically independent Gd 3+ ions. All of them are ninefold coordinated, two of them are each coordinated by a tricapped trigonal prism, whereas the third one is coordinated by a monocapped square antiprism. The compound represents an hydrate isomer of the known Gd 3 (H 2 ClCCOO) 9 (H 2 O) 4 ·H 2 O.

Breaking the law: Whereas antiferromagnetic interactions in crystalline carboxylates of lanthanides are often observed, ferromagnetism is unknown. The first example of a ferromagnetic interaction is observed for a crystalline sample of the gadolinium compound [{Gd(OAc)3(H2O)2}2]⋅4 H2O (see picture Gd: gray, O: red).

LU2O7S12, monoclinic, C\Um\ (No. 12), a = 6.762(2)Â, b = 8.835(3) Â, c = 4.711(2) k,ß = 101.99(4)°,V= 275.3 Â 3 , Ζ = 2, Rgf(F) = 0.019, wRretfF 2 ) = 0.045, T= 293 K.

Terbium thiosilicate Tb-4[SiS4](3) was obtained by reaction of the elements in a bromine atmosphere in silica ampoules. The crystal structure was determined by single crystal X-ray diffraction methods (monoclinic, P2(1)/n, Z = 4, a = 983.6(2) pm, b = 1096.4(2) pm, c = 1639.1(3) pm, b = 102.76(2)degrees). The structure is characterized by four crystallographically independent terbium positions with coordination numbers seven and eight as well as isolated [SiS4](4-)-tetrahedra. The magnetic behaviour of powdered crystals was interpreted by theoretical calculations where the influence of the crystal field was taken into account by applying the angular overlap model and magnetic exchange by the molecular field approximation.

The structure of completely exchanged Mn2+-beta"-Al2O3 (Mn0.77Al10.46Mg0.54O17) crystals has been investigated by single-crystal X-ray diffraction methods at room temperature (trigonal, Rim, Z = 3, a = 560.65(7), c = 3329.3(9) pm). The manganese ions (Mn2+) are found to occupy Beevers-Ross (56%) and mid-oxygen positions (44%) in nearly the same amounts. The crystal composition was confirmed by electron probe microanalyses on various crystals.

The crystal structure of Ho3+-beta"-Al2O3 (Ho-0.5- Mg0.5Al10,5O17) was determined by single crystal X-ray diffraction methods at room temperature (trigonal. R (3) over barm, Z = 3, a = 561.43(12) pin, c = 33517(11) pm). The structural chemical results are correlated with magnetic measurements, where ligand field calculations applying the angular overlap model have been taken into account.

Dy4(SiS4)3 is isotypic with Tb4(SiS4)3 [Hatscher & Urland (2002). Z. Anorg. Allg. Chem. 628, 1673–1677]. It contains almost undistorted, isolated (SiS4)4− tetrahedra and four crystallographically different Dy positions with coordination numbers seven and eight.

Dominant in the structure of the title compound are two crystallographically different Si positions forming almost undistorted isolated [SiS4]4− tetrahedra and four crystallographically different Sm positions with coordination numbers seven and eight. The thio­silicate is isotypic with Nd3ClS2[SiS4] [Hatscher & Urland (2002d), Mater. Res. Bull. In the press].