The novel tetrameric gadolinium(III) compound [Gd-4(OH)(4)(CF3COO)(8)(H2O)(4)] center dot 2.5 H2O was synthesized and structurally characterized by X-ray crystallography. The Gd3+ ions are bridged by hydroxide ions and carboxylate groups to tetramers with Gd3+-Gd3+ distances between 384.2(2) and 388.1(2) pin. The compound crystallizes in the monoclinic space group C2/c (Z = 4). The magnetic behaviour of [Gd-4(OH)(4)(CF3COO)(8)(H2O)(4)] center dot 2.5 H2O was investigated in the temperature range of 2 to 300 K. The magnetic data of this compound indicate antiferromagnetic interactions (J(ex) = -0.0197 cm(-1)).

The gadolinium(III) trifluoroacetates ((CH3)2NH2)[Gd(CF3COO)4] (1), ((CH3)3NH)[Gd(CF3 COO)4(H2O)] (2), Gd(CF3COO)3(H2O)3 (3) as well as Gd2(CF3COO)6(H2O)2(phen)3 · C2H5OH (4) (phen = 1,10-phenanthroline) were synthesized and structurally characterized by X-ray crystallography. These compounds crystallize in the space group P1̅ (No. 2, Z = 2) (1, 2 and 4) and P 21/c (No. 14, Z = 4) (3), respectively, with the following lattice constants 1: a = 884.9(2), b = 1024.9(2), c = 1173.1(2) pm, α = 105.77(2), β = 99.51(2), γ = 107.93(2)°; 2: a = 965.1(1), b = 1028.6(1), c = 1271.3(2) pm, α = 111.83(2), β = 111.33(2), γ = 90.44(2)°; 3: a = 919.6(2), b = 1890.6(4), c = 978.7(2) pm, β = 113.94(2)°; 4: a = 1286.7(8), b = 1639.3(8), c = 1712.2(9) pm, α = 62.57(6), β = 84.13(5), γ = 68.28(5)°. The compounds consist of Gd3+ ions which are bridged by carboxylate groups either to chains (1 and 2) or to dimers (3 and 4). In addition to the Gd3+ dimers, compound (4) also contains monomeric Gd3+ units. The magnetic behaviour of 2 and 3 was investigated in a temperature range of 1.77 to 300 K. The magnetic data for these compounds indicate weak antiferromagnetic interactions

Four complexes with the formulae Gd-2(ClF2CCOO)(6)(hypy)(2) (1), Gd-2(F3CCOO)(6)(hypy)(2) (2), Gd-2(F2HCCOO)(6)(hypy)(2) (3) and Gd-2(Cl2HCCOO)(6)(H2O)(2)(hypy)(2) (4) have been synthesised and characterised by single-crystal X-ray diffraction methods at room temperature. The title compounds have been obtained by reaction of the corresponding gadolinium carboxylates with 4-hydroxypyridine in a solution of ethanol and water. They crystallise in the triclinic space group P(1)overbar (Z = 2) [1: a = 999.8(4) pm, b = 1061.8(5) pm, c = 1283.6(6) pm, alpha = 91.23(5)degrees, beta = 111.29(5)degrees and gamma = 105.27(5)degrees; 2: a = 972.4(4) pm, b = 1053.5(5) pm, c = 1252.4(6) pm, alpha = 94.23(5)degrees, beta = 110.21(5)degrees and gamma = 104.84(5)degrees; 3: a = 883.3(4) pm, b = 1051.3(4) pm, c = 1284.9(6) pm, alpha = 100.46(5), beta = 109.87(5)degrees and gamma = 97.43(5)degrees; 4: a = 913.7(4) pm, b = 1079.0(5) pm, c = 1137.5(5) pm, alpha = 93.41(5)degrees, beta = 109.36(5)degrees and gamma = 99.53(5)degrees]. The crystal structures consist of dinuclear Gd3+-Gd3+ units. The corresponding residuals (all data) for the refined structures are 4.82 % (1), 5.93 % (2), 5.68 % (3) and 4.04 % (4). The magnetic behaviour of the compounds was investigated over the temperature range 1.76-300 K. The magnetic data were interpreted by considering exchange interactions within the dimeric units [J(ex) = -0.019 cm(-1) (1), J(ex) = -0.034 cm(-1) (2), J(ex) = -0.064 cm(-1) (3), J(ex) = -0.011 cm(-1) (4)]. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).

Single crystals of Gd(ClF2CCOO)(3)(H2O)(bipy)(2) have been obtained by reaction of Gd(ClF2CCOO)(3)(H2O)(3) with 2,2'-bipyridyl in a solution of ethanol and water. The compound crystallises in the triclinic space group P (1) over bar (Nr. 2, Z = 2, a = 1005.0 pm, b = 1175.7 pm, c = 1181.5 pm, alpha = 98.79 degrees, beta = 109.84 degrees, gamma = 105.61 degrees). The Gd3+ ions are bridged by carboxylate groups to dimers and are eightfold coordinated by six oxygen and two nitrogen atoms. The magnetic behaviour of the compound was investigated in the temperature range of 2 to 300 K. The magnetic data indicate an antiferromagnetic interaction within the dimeric units.

Single crystals of [Gd-2(ClF2CCOO)(6)(H2O)(2)(biPY)(2)](2). C2H5OH have been obtained by reaction of Gd(ClF2CCOO)(3)(H2O)(3) with 2,2'-bipyridyl in a solution of ethanol and water. The compound crystallizes in the triclinic space group P (1) over bar (Nr. 2, Z = 2, a = 1201.6(2) pm, b = 1241.1(3) pm, c = 1990.4(3) pm, alpha = 96.29(2)degrees, beta = 104.85(2)degrees, gamma = 116.70(2)degrees). The Gd 31 ions are bridged by carboxylate groups to dimers and are eightfold coordinated by six oxygen and two nitrogen atoms. The magnetic behaviour of the compound was investigated in the temperature range of 1.77 to 300 K. The magnetic data indicate an anti ferromagnetic interaction within the dimeric units.

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)).

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)