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Handel R.W.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Willms H.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Jameson G.B.,Massey University | Berry K.J.,23 Seabreeze Street | And 3 more authors.
European Journal of Inorganic Chemistry | Year: 2010

The influence of the length of the linking alkyl spacer and of the presence of either a proton or a methyl group, in four related terdentate N3 Schiff base ligands, on the structures and properties of the resulting iron(II) and cobalt(II) complexes has been investigated. The four ligands were prepared in situ by condensation of 2-(2-aminoethyl)pyridine or 2-(aminomethyl)pyridine with 2-acetylpyridine (L1 vs, L3) or 2-formylpyridine (L2 vs. L4). Hence they comprised a mixture of a relatively rigid chelate with a 2-iminopyridyl moiety, comparable to bipyridine coordination, and a more flexible chelate containing the -(CH2)n- spacer. Four iron(II) complexes, [Fe(L1) 2](BF4)2 (1), [Fe(L2)2](BF 4)2 (2), [Fe(L3)2](BF4)2 (3), [Fe(L4)2](BF4)2 (4), were obtained whereas only in the case of the two ethylene (i.e. not methylene) spaced ligands could pure cobalt(II) complexes, [Co(L1)2](BF4)2 (5), [Co(L2)2]-(BF4)2 (6), be obtained. The 1H NMR spectra confirmed that in MeCN 1-4 are diamagnetic whereas 5 and 6 are paramagnetic. X-ray structure determinations of the ethylene-linked complexes, 1, 5 and 6, revealed distorted octahedral geometries due to chelate ring restrictions. The M-N distances were typical for high-spin cobalt(II) (5 and 6) and for low-spin iron(II) (1). The magnetic data on 5 and 6 are typical of those expected for distorted octahedral high-spin d7 species; fitting attempts have yielded zero-field splitting and low symmetry ligand field parameters. A metal-centred M2+/3+ redox wave and ligand-based reduction processes were observed for 1-6 in MeCN. The metal-centred redox potential (Fe: 1 0.59, 2 0.68, 3 0.58, 4 0.70 V; Co: 5 0.03, 6 0.09 V vs. Fc/Fc+) was influenced much more strongly by the presence of the proton vs. methyl group (Fe: shift of 0.09-0.12 V, Co: shift of 0.06 V) than by the bridging methylene vs. ethylene group (Fe: shift of 0.01-0.02 V). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Langley S.K.,Monash University | Moubaraki B.,Monash University | Berry K.J.,23 Seabreeze Street | Murray K.S.,Monash University
Dalton Transactions | Year: 2010

The synthesis and characterisation of three new mixed-valent manganese clusters [MnII 4MnIII 16O 12(OH)4(tea)8(chp)4] ·6MeOH·4H2O (1), [MnII 6Mn III 4(teaH)4(teaH2) 2(tpaa)6(F)8]·2Et2O· 4MeCN (2) and [MnII 6MnIII 4(teaH) 4(teaH2)2(2-bpca)6(F) 8]·4MeCN (3) are reported. They were obtained by the reaction of simple manganese salts with triethanolamine (teaH3), triethylamine (NEt3) and the appropriate co-ligand. In the case of 1, 6-chloro-2-hydroxypyridine (Hchp) was used, for 2, triphenylacetic acid (tpaa) and 3, 2-biphenylcarboxylic acid (2-bpca). The core of 1 is a Mn20 supertetrahedron, while the cores of 2 and 3 are identical and have distorted ring-like topologies. Variable-temperature, solid-state DC and AC magnetic studies were performed on 1-3 in the 2-300 K (DC) and 2-18 K (AC) ranges. Cluster 1 has a S = 9 ground state with excited S states, larger in value than 9, close in energy. No SMM features were apparent in 1. In contrast, clusters 2 and 3, with S = 12 or 13 ground states, and with excited S levels of lower value than 12 lying close in energy, do show SMM features, albeit below 2 K in their AC out-of-phase, frequency dependent data. © The Royal Society of Chemistry 2010.

Langley S.K.,Monash University | Chilton N.F.,Monash University | Massi M.,Curtin University Australia | Moubaraki B.,Monash University | And 2 more authors.
Dalton Transactions | Year: 2010

The syntheses and characterizations are reported for six new homo- and heterovalent manganese clusters, utilizing pyridyl functionalized β-diketones ligands. The reaction of the trinuclear complex [Mn 3O(O2CPh)6(H2O)(Py)2] with 1,3-di(pyridine-2-yl)propane-1,3-dione (dppdH) in CH2Cl 2 resulted in a mixed-valence Mn3 IIMn 6 IIIMnIV decanuclear cluster of formula [Mn10O7(dppd)3(O2CPh) 11]·4CH2Cl2 (1). The structure of the core of 1 is based upon a centred tricapped trigonal prism. Reacting Mn(BF 4)2·xH2O with dppdH and triethylamine (NEt3) in CH2Cl2-MeOH gave a rare, homoleptic hexanuclear cluster of formula [MnII 6(dppd) 8][BF4]4 (2) which has a triangular based core. Reaction of Mn(Y)2·xH2O, Y = NO3 - or BF4 -, with dppdH or 1-phenyl-3-(2-pyridyl) propane-1,3-dione (pppdH) in the presence of triethanolamine (teaH3) and NEt3 gave a heptanuclear 'disc' like manganese core of general formula [MnII 7(X)6(tea)(OH)3][Y] 2·solv (3) X = pppd- or dppd- and Y = NO3 - or BF4 -. The addition of N-(2-pyridinyl)acetoacetamide (paaH) to Mn(Y)2·4H2O Y = NO3 - or ClO4 - in MeOH gave a second divalent heptanuclear cluster with a 'disc'-like core of general formula [Mn7(paa)6(OMe)6][X]2·solv (4) (X = NO3 - or ClO4 -), whilst the addition of paaH to a mixture of Mn(NO3)2·4H 2O, teaH3 and NEt3 in CH2Cl 2-MeOH resulted in the formation of a mixed-valence Mn 2 IIMn2 III tetranuclear 'butterfly' complex of formula [Mn4(paa)4(teaH)2][NO 3]2·2MeOH·2CH2Cl2 (5). Compound 5 displays the rare MnII/III oxidation state distribution of the body positions being MnII while the wing tips are Mn III. The in situ formation of the tetranuclear [Mn 4(teaH)2(teaH2)2(O 2C(CH3)3)2][O2C(CH 3)3]2'butterfly' complex followed by the addition of Mn(O2CMe)2·4H2O resulted in a mixed-valence Mn4 IIMnIIIMnIV hexanuclear species of formula [Mn6O2(teaH 2)4(O2CMe)4][NO3] 2[O2CMe]·CH2Cl 2·MeOH·2H2O (6). The core of 6 displays a face sharing dicubane topology. Compounds 1 and 6 both display novel trapped-valence metal cores containing three different oxidation states on the manganese ion. Compounds 1, 2 and 3 are the first manganese based dppd clusters, while 4 and 5 are the first with the pyridylamino-substituted β-diketone ligand (paaH). The magnetic data for 1, 2, 3, 4, and 6 are dominated by antiferromagnetic interactions within the clusters, leading to small ground spin values of S = 1 for 1, S = 3 for 2, S = 5/2 for 3, S = 5/2 for 4 and S = 1/2 for 6. Compound 5, however, displays overall ferromagnetic interactions with the data indicating an S = 6 ground state. 5 also exhibits probable single molecule magnet behaviour as indicated by frequency dependent out-of-phase χM′′ peaks in the AC susceptibility measurements. © 2010 The Royal Society of Chemistry.

Chesman A.S.R.,Monash University | Turner D.R.,Monash University | Berry K.J.,23 Seabreeze Street | Chilton N.F.,Monash University | And 4 more authors.
Dalton Transactions | Year: 2012

The isostructural heterometallic complexes [LnIII 2MnIII2O2(ccnm)6(dcnm) 2(H2O)2] (Ln = Eu (1Eu), Gd (1Gd), Tb (1Tb), Er (1Er); ccnm = carbamoylcyanonitrosomethanide; dcnm = dicyanonitrosomethanide) have been synthesised and structurally characterised. The in situ transition metal promoted nucleophilic addition of water to dcnm, forming the derivative ligand ccnm, plays an essential role in cluster formation. The central [Ln III2MnIII2(O)2] moiety has a "butterfly" topology. The coordinated aqua ligands and the NH2 group of the ccnm ligands facilitate the formation of a range of hydrogen bonds with the lattice solvent and neighbouring clusters. Magnetic measurements generally reveal weak intracluster antiferromagnetic coupling, except for the large JMnMn value in 1Gd. There is some evidence for single molecule magnetic (SMM) behaviour in 1Er. Comparisons of the magnetic properties are made with other recently reported butterfly-type {Ln IIIxMIII4-x (d-block)} clusters, x = 1, 2; M = Mn, Fe. © 2013 The Royal Society of Chemistry.

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