9 research outputs found
A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2'-Pyridil
No full textReactions of 2, 2-pyridil (pyCOCOpy) with CuCl2 · 2H2O and CuBr2in EtOH yielded the mononuclear complex [Cu(pyCOOEt)2Cl2] · H2O (1) and the one-dimensional, mixed-valence complex [CuI2CuII(pyCOOEt)2Br4]n (2), respectively. Both complexes crystallize in the triclinic space group P 1. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2),α = 101.17(1), β = 114.55(1), γ = 94.14(1)◦ for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.78(1)◦ for 2. 2,2-pyridil undergoes a metal-assisted alcoholysis and oxidation leading to decomposition and yielding the ethyl picolinate (pyCOOEt) ligand. The autoredox process associated with the reduction of copper(II) to copper(I) in the case ofcomplex 2 is discussed in terms of the increased redox activity of the copper(II) bromide system relative to the copper(II) chloride system
Oxime based manganese molecular magnets
No full textThe synthesis and characterisation of a large family of hexametallic [MnIII
6] Single-Molecule Magnets with general formula [MnIII
6O2(R-sao)6(X)2(L)4-6] (where sao2- =
dianion of salicylaldoxime; R = H, Me, Et, Ph; X = O2CR' (R' = H, Me, Ph etc),
Hal , O2PHPh or O2P(Ph)2; L = solvent) are presented. Deliberate structural
distortions of the [Mn3O] trinuclear moieties within the complexes are used to tune
the observed magnetic properties. These findings highlight a qualitative magnetostructural
correlation whereby the type (anti- or ferromagentic) of each Mn2 pairwise
magnetic exchange is dominated by the magnitude of each individual Mn-N-O-Mn
torsion angle.
To shed further light on this intriguing family of nanomagnets, a large family of the
analogous “half” molecules has been synthesised and fully characterised. These
trimetallic [MnIII
3] complexes can be divided into three categories with general
formulae (type 1) [MnIII
3O(R-sao)3(X)(sol)3-4] (where R = H, Me, tBu; X = O2CR (R
= H, Me, Ph etc); sol = py and / or H2O), (type 2) [MnIII
3O(R-sao)3(X)(sol)3-5] (where
R = Me, Et, Ph, tBu; X = O2CR (R = H, Me, Ph etc); sol = MeOH, EtOH and / or
H2O), and (type 3) [MnIII
3O(R-sao)3(sol)3](XO4) (where R = H, Et, Ph, Naphth; sol =
py, MeOH, -pic, Et-py, tBu-py; X = Cl, Re). In the crystals the ferromagnetic
triangles are involved in extensive inter-molecular H-bonding which is clearly
manifested in the magnetic behaviour, producing exchange-biased SMMs. These
interactions can be removed by ligand replacement to give “simpler” SMMs.
The [MnIII
6] and [MnIII
3] molecular nanomagnets are then exploited as building
blocks to construct supramolecular architectures by means of host-guest interactions
and coordination driven self-assembly. A number of discrete and infinite
architectures based on the molecular triangle [Mn3] and various pyridyl-type ligands
were obtained and structurally and magnetically characterised
The hexakis(N,N '-dimethylurea)cobalt(II) cation : a flexible building block for the construction of hydrogen bonded networks
No full textAbstract: The ligand N,N'-dimethylurea (DMU) is used to propagate the octahedral coordination geometry of [Co(DMU)(6)](2+) into 1D and 2D assemblies via a combination of coordinative bonds and interionic hydrogen-bonding. Compounds [Co(DMU)(6)](ClO4)(2) (1), [Co(DMU)(6)](BF4)(2) (2) and [Co(DMU)(6)](NO3)(2) (3) have been prepared from the reactions of DMU and the appropriate hydrated cobalt(II) salts in EtOH, MeCN or Me2CO (only for 1) in the presence of 2,2-dimethoxypropane. Crystal structure determinations demonstrate the existence of [Co(DMU)(6)](2+) cations and ClO4- BF4- or NO3- counterions. The great stability of the [Co(DMU)(6)](2+) cation in the solid state is attributed to a pseudochelate effect which arises from the existence of strong intracationic N-H...O(DMU) hydrogen bonds. The [Co(DMU)(6)](2+) cations and counterions self-assemble to form a hydrogen-bonded 1D architecture in 1, and different 2D hydrogen-bonded networks in 2 and 3. The precise nature of the resulting supramolecular structure is influenced by the nature of the counterion. Two main motifs of intermolecular (interionic) hydrogen bonds have been observed: N-H...O(ClO4-, NO3-) or N-H...F(BF4-) and weak C-H...F(BF4-) or C-H...O(NO3-) hydrogen bonds. The complexes were also characterized by vibrational spectroscopy (IR, far-IR, low-frequency Raman). The spectroscopic data are discussed in terms of the nature of bonding and the known structures
Polymetallic clusters of iron(III) with derivatised salicylaldoximes
No full textThe synthesis and magnetic properties of the compounds [HNEt3][Fe-2(OMe)(Ph-sao)(2) (Ph-saoH)(2)]center dot 5MeOH (1.5MeOH), [Fe3O(Et-sao)(O2CPh)(5)(MeOH)(2)]center dot 3MeOH (2.3MeOH), [Fe-4(Me-sao)(4)(Me-saoH)(4)] (3), [HNEt3](2)[Fe6O2(Me-sao)(4)(SO4)(2)(OMe)(4)(MeOH)(2)](4), [Fe8O3(Me-sao)(3)(tea)(teaH)(3)(O2CMe)(3)] (5), [Fe8O3(Et-sao)(3)(tea)(teaH)(3)(O2CMe)(3)] (6), and [Fe8O3(Ph-sao)(3)(tea)(teaH)(3)(O2CMe)(3)] (7) are reported (Me-saoH(2) is 2'-hydroxyacetophenone oxime, Et-saoH(2) is 2'-hydroxypropiophenone oxime and Ph-saoH(2) is 2-hydroxybenzophenone oxime). 1-7 are the first Fe-III compounds synthesised using the derivatised salicylaldoxime ligands, R-saoH(2). 1 is prepared by treatment of Fe-2(SO4)(3)center dot 6H(2)O with Ph-saoH(2) in the presence of NEt3 in MeOH; 2 prepared by treatment of Fe(ClO4)(2)center dot 6H(2)O with Et-saoH(2) and NaO2CPh in the presence of NEt4OH in MeOH; 3 prepared by treatment of Fe(ClO4)(2)center dot 6H(2)O with Me-saoH(2) and NaO2CCMe3 in the presence of NEt4OH in MeOH; and 4 prepared by treatment of Fe-2(SO4)(3)center dot 6H(2)O with Me-saoH(2) in the presence of NEt3 in MeOH. 4 is a rare example of a polynuclear iron complex containing a coordinated SO42- ion. Compounds 5-7 are prepared by treatment of Fe(O2CMe)(2) with Me-saoH(2) (5), Et-saoH(2) (6), Ph-saoH(2) (7) in the presence of H(3)tea (triethanolamine) in MeOH, and represent the largest nuclearity Fe-III clusters containing salicyladoxime-based ligands, joining a surprisingly small family of characterised octanuclear Fe complexes. Variable temperature magnetic susceptibilty measurements of 1,3 and 5-7 reveal all five complexes possess S = 0 spin ground states; 2 possesses an S = 1/2 spin ground state, while 4 has an S = 4 +/- 1 spin ground state
A general synthetic route for the preparation of high-spin molecules: Replacement of bridging hydroxo ligands in molecular clusters by end-on azido ligands
No full textA general method of increasing the ground-state total spin value of a polynuclear 3d-metal complex is illustrated through selected examples from cobalt(II) and nickel(II) cluster chemistry that involves the dianion of the gem-diol form of di-2-pyridyl ketone and carboxylate ions as organic ligands. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions, by the end-on azido ligand, which is a ferromagnetic coupler. (c) 2006 Elsevier Ltd. All rights reserved
A general synthetic route for the preparation of high-spin molecules: Replacement of bridging hydroxo ligands in molecular clusters by end-on azido ligands
No full textAbstract A general method of increasing the ground-state total spin value of a polynuclear 3d-metal complex is illustrated through selected examples from cobalt(II) and nickel(II) cluster chemistry that involves the dianion of the gem-diol form of di-2-pyridyl ketone and carboxylate ions as organic ligands. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions, by the end-on azido ligand, which is a ferromagnetic coupler
Polynuclear metal clusters using polyalkoxide ligands
No full textWe have investigated the use of calix[4]arenes in 3d and 3d/4f chemistry which produced a family of 7 new complexes. These are: [MnIII2MnII2(OH)2(TBC4)2(DMF)6] (1) , the analogous version with C4 (2). [MnIII4GdIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (3), [MnIII4TbIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (4), [MnIII4DyIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (5),
[CuII9(OH)3(TBC4)3Cl2(DMSO)6](CuICl2)·DMSO (6·DMSO) (6) and [CuII9(OH)3(TBC4)3(NO3)2(DMSO)6](NO3)· DMSO (7·DMSO) (7).
We continued with a series of Pseudo Metallocalix[6]arene planar disc complexes : [Ni7(OH)6(L1)6](NO3)2 (8), [Ni7(OH)6(L1)6](NO3)2.2MeOH (9), [Ni7(OH)6(L1)6](NO3)2.3MeNO2 (10), [Ni7(OH)6(L2)6](NO3)2.2MeCN (11), [Zn7(OH)6(L1)6](NO3)2.2MeOH.H2O (12) and [Zn7(OH)6(L1)6](NO3)2.3MeNO2 (13) and in the final part of this thesis we present a family of tetranuclear mixed valent Mn complexes using the tripodal ligand heedH2 : [MnII2MnIV2O2(heed)2(EtOH)6Br2]Br2 (14), [MnII2MnIV2O2(heed)2(H2O)2Cl4] (15), [MnII2MnIV2O2(heed)2(heedH2)2](ClO4)4 (16), [MnII2MnIV2O2(heed)2(MeCN)2(H2O)2(bpy)2](ClO4)4 (17), [MnII2MnIV2O2(heed)2(bpy)2Br4] (18); and the 2-D network of tetranuclear MnII/IV clusters {[MnII2MnIV2O2(heed)2(H2O)2(MeOH)2(dca)2]Br2}n (19). In total nineteen new complexes are reported. Studies of the magnetic properties show that 1 and 2 are SMM’s, whilst complex 3 is an excellent magnetic refrigerant for low-temperature applications and 4 and 5 behave as low-temperature molecular magnets
