Mononuclear manganese(III) complexes as building blocks for the design of trinuclear manganese clusters: study of the ligand influence on the magnetic properties of the [Mn3(mu3-O)](7+) core.

The synthesis, crystal structure, and magnetic properties of three new manganese(III) clusters are reported, [Mn 3(mu 3-O)(phpzH) 3(MeOH) 3(OAc)] (1), [Mn 3(mu 3-O)(phpzMe) 3(MeOH) 3(OAc)].1.5MeOH (2), and [Mn 3(mu 3-O)(phpzH) 3(MeOH) 4(N 3)].MeOH (3) (H 2phpzH = 3(5)-(2-hydroxyphenyl)-pyrazole and H 2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole). Complexes 1- 3 consist of a triangle of manganese(III) ions with an oxido-center bridge and three ligands, phpzR (2-) (R = H, Me) that form a plane with the metal ions. All the complexes contain the same core with the general formula [Mn 3(mu 3-O)(phpzR) 3] (+). Methanol molecules and additional bridging ligands, that is, acetate (complexes 1 and 2) and azide (complex 3), are at the terminal positions. Temperature dependent magnetic susceptibility studies indicate the presence of predominant antiferromagnetic intramolecular interactions between manganese(III) ions in 1 and 3, while both antiferromagnetic and ferromagnetic intramolecular interactions are operative in 2.

Short-range correlations in d-f cyanido-bridged assemblies with XY and XY-Heisenberg anisotropy.

Two new d-f cyanido-bridged 1D assemblies [RE(pzam)(3)(H(2)O)Mo(CN)(8)]·H(2)O (RE = Sm(III), Er(III)) were synthesized and their magneto-structural properties have been studied by field-dependent magnetization and specific heat measurements at low temperatures (≥0.3 K). Below ≈ 10 K the ground state of both the Sm(III) and Er(III) ions is found to be a Kramers doublet with effective spin S = 1/2. From analyses of the low-temperature magnetic specific heat and magnetization the exchange coupling between these RE(III) effective spins and the Mo(v) spins S = 1/2 along the structural chains has been determined. It is found to be antiferromagnetic, with J(∥)/k(B) = -2.6 K and Ising-Heisenberg symmetry of the interaction (J(∥)/J(⊥) = 0.3) for RE = Sm(III), whereas the compound with RE = Er(III) behaves as a pure XY chain, with J(⊥)/k(B) = -1.0 K. For the compound [Sm(pzam)(3)(H(2)O)Mo(CN)(8)]·H(2)O a small λ-type anomaly in the specific heat is observed at about 0.6 K, which is ascribed to a transition to long-range magnetic ordering induced by weak interchain interactions of dipolar origin. No evidence for 3D interchain magnetic ordering is found in the Er(III) analogue.

High nuclearity manganese(III) compounds containing phenol-pyrazole ligands: the influence of the ligand on the core geometry.

Three high-nuclearity manganese(III) clusters have been synthesized and characterized: [Mn8(µ4-O)4(phpzH)8(thf)4] (1), [Mn8(µ4-O)4(phpzH)4(EtOH)4]·2EtOH (2), and [Mn6(µ3-O)4(µ3-Br)2(HphpzEt)6(phpzEt)] (3). Compounds 1 and 2 contain a [Mn8(µ4-O4)(phpzH)8] core in which antiferromagnetic interactions between the manganese(III) ions are found. Compound 3 is a hexanuclear manganese(III) cluster in which weak ferromagnetic interactions appear to be operative. The formation and the stability of the cluster cores in relation to the type of phenol-pyrazole ligand and the reaction conditions are discussed.

Manganese(III) compounds with phenol-pyrazole based-ligands: impact of the co-ligand and the carboxylate ligand on the trinuclear core [Mn3(mu3-O)(phpzR)3(O2CR')n](1-n).

The reaction of H2phpzR (R = Me, Ph; H2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole and H2phpzPh = 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole) with Mn(O2CR').nH2O (R' = Me and Ph) and (nBu4N)MnO4 in ethanol (EtOH) affords three new manganese(III) compounds, [Mn3(mu3-O)(phpzMe)3(O2CMe)(EtOH)].EtOH (1), (nBu4N)[Mn3(mu3-O)(phpzMe)3(O2CPh)2] (2) and (nBu4N)[Mn3(mu3-O)(phpzPh)3(O2CPh)2] (3). Their synthesis, crystal structure and magnetic properties are reported. Compounds 1-3 are mu3-oxido-centered trinuclear manganese(III) compounds whose edges are bridged by phpzR2- with average intracluster separations of 3.25 A. The three Mn-O-Mn angles are distorted from the equilateral triangle with values in the range of 113 degrees to 124 degrees; 117 degrees to 125 degrees; and 117 degrees to 126 degrees for complexes 1-3, respectively. Hydrogen bonding interactions between the trinuclear units of 1 result in a one-dimensional chain structure. Compounds 2 and 3 have isolated trinuclear units, perhaps as a result of the presence of the bulky nBu4N+ cation. Temperature-dependent magnetic susceptibility studies indicate the presence of both antiferromagnetic and ferromagnetic interactions in compound 1 (J1 = -10.3 cm(-1), J2 = +10.9 cm(-1)), while only antiferromagnetic interactions are present in compounds 2 and 3 (J1 = -4.2 cm(-1), J2 = -10.3 cm(-1) for 2; and J1 = -4.8 cm(-1), J2 = -10.2 cm(-1) for 3), with J1 representing the similar Mn-O-Mn angles and J2 representing the unique Mn-O-Mn angle (Mn(1)-O(1)-Mn(2)).

Strongly isolated ferromagnetic layers in poly-trans-mu-dichloro- and poly-trans-mu-dibromobis(1-(2-chloroethyl)-tetrazole-N4)copper(II) complexes.

Two new isostructural compounds, dichlorobis(1-(2-chloroethyl)tetrazole)copper(II) (1) and dibromobis(1-(2-chloroethyl)tetrazole)copper(II) (2), have been prepared. The synthesis, characterization, and spectral and magnetic properties as well as the crystal and molecular structures of 1 and 2 have been studied. Both complexes form two-dimensional, distorted square grid planes of copper and halides, distinctly separated by layers of tetrazole ligands. The differential (ac) magnetic susceptibility, chi = (deltaM/deltaH)(T), and magnetization M(H) of both complexes have been studied as a function of temperature and field. The compounds possess a ferromagnetic interaction within the isolated copper-halide layers (J/k(B) = 8.0 K, J/k(B) = 10.2 K, respectively, for the chloride and the bromide, and T(c) = 4.75 K, T(c) = 8.01 K). The magnetic coupling J'/k(B) between the different layers is found to be very weak (|J'/J|