The synthesis and magnetic characterisation of a series of bis-μ-alkoxide bridged Mn(III) dinuclear complexes of general formula [Mn(III)(2)(μ-OR)(2)(biphen)(2)(ROH)(x)(L)(y)] (where R = Me, Et; H(2) biphen = 2,2'-biphenol and L = terminally bonded N-donor ligand) is described, doubling the literature basis set for this type of complex. Building on these findings we have categorised all known μ-OR bridged Mn(III) dinuclear complexes into one of three classifications with respect to their molecular structures. We have then employed DFT and MO calculations to assess all potential magneto-structural correlations for this class of compound in order to identify the structural requirements for constructing ferromagnetic family members. Our analysis indicates that the most influential parameter which governs the exchange interaction in this class of compounds is the relative orientation of the JT axes of the Mn(III) atoms. A perpendicular orientation of the JT axes leads to a large ferromagnetic contribution to the exchange. These results also suggest that a large ferromagnetic interaction and a large anisotropy are unlikely to co-exist in such structural types.
The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO(4))·EtOH (1) built using the pro-ligand 2,2'-biphenol (LH(2)), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu(II) and Mn(III) ions mediated through the phenolate O-atoms (J = -33.4 cm(-1)), with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy. Simulations of high-field and high frequency powder EPR data suggest a single-ion anisotropy D(Mn(III)) = +4.45 cm(-1). DFT calculations also yield an antiferromagnetic exchange for 1, though the magnitude is overestimated (J(DFT) = -71 cm(-1)). Calculations reveal that the antiferromagnetic interaction essentially stems from the Mn(d(x(2)-y(2)))-Cu(d(x(2)-y(2))) interaction. The computed single-ion anisotropy and cluster anisotropy also correlates well with experiment. A larger cluster anisotropy for the S = 3/2 state compared to the single-ion anisotropy of Mn(III) is rationalised on the basis of orbital mixing and various contributions that arise due to the spin-orbit interaction.
We report the first Co(II) based discrete and extended network materials comprising the 2,2´-biphenol ligand. We first present the synthesis and magnetic characterisation of the Co(II) dinuclear complexes [Co(II) 2 (L) 2 (py) 4 ].2EtOH (1) and [Co(II) 2 (L) 2 (4-pic) 4 ].2LH 2 (2), both of which exhibit antiferromagnetic exchange between their Co(II) centres. The introduction of the co-ligand 2-hydroxypyridine (2-hpH) leads to the production of planar octametallic complex [Co(II) 8 (OMe) 2 (L) 4 (LH) 2 (2-hp) 4 (MeCN) 4 ].MeCN (3). Magnetic susceptibility and magnetisation measurements on 3 indicate dominant ferromagnetic exchange between the Co(II) centres. We also 10 describe the first Co(II) / 2,2'-biphenol extended networks in the shape of the 1D coordination polymer {[Co(II)(LH)(4,4-tmdp) 2 (NO 3 )](LH 2 )} n (4) (where 4,4'-tmdp = 4,4'-trimethylenedipyridine) and the 2D brickwall network [Co(II)(LH)(trans-bpe) 1.5 (NO 3 )] (5) (where trans-bpe = trans-1,2-bis(4-pyridyl)ethylene), comprising T-shaped nodes.
We report the synthesis and full characterisation of a family of chains each exhibiting an alternating [M-Na-M-] n (M ¼ Mn 3+ or Fe 3+ ) 1-D topology linked via the 2,2 0 -biphenol ligand along with various N-donor co-ligands such as pyridine, 3-picoline and 2,2-bipyridine. The chains [Na 2 Mn 2 (biphen) 4 (py) 3 (EtOH) 2 ] n (1), [Na 2 Mn 2 (biphen) 4 (3-cnp) 2 (EtOH) 3 ] n (5), [{Na 2 Mn 2 (biphen) 4 (4-Et-py) 3 (EtOH) 2 }$EtOH] n ( 6) and [NaFe(biphen) 2 (2,2-bipy)(EtOH) 2 ] (8) are connected into 1-D arrays via predominantly covalent bonds while their siblings 4)) are linked via ionic bonds along with strong hydrogen bonding interactions.
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