Nicholas F. Chilton

PHI: a powerful new program for the analysis of anisotropic monomeric and exchange-coupled polynuclear d- and f-block complexes.

A new program, PHI, with the ability to calculate the magnetic properties of large spin systems and complex orbitally degenerate systems, such as clusters of d‐block and f‐block ions, is presented. The program can intuitively fit experimental data from multiple sources, such as magnetic and spectroscopic data, simultaneously. PHI is extensively parallelized and can operate under the symmetric multiprocessing, single process multiple data, or GPU paradigms using a threaded, MPI or GPU model, respectively. For a given problem PHI is been shown to be almost 12 times faster than the well‐known program MAGPACK, limited only by available hardware.

Molecular coolers: The case for [CuII5GdIII4]

The use of triethanolamine (teaH3) in 3d/4f chemistry produces the enneanuclear cluster compound [CuII5GdIII4O2(OMe)4(teaH)4(O2CC(CH3)3)2(NO3)4]·2MeOH·2Et2O (1·2MeOH·2Et2O) whose molecular structure comprises a series of vertex- and face-sharing {GdIIICuII3} tetrahedra. Magnetic studies reveal a large number of spin states populated even at the lowest temperatures investigated. Combined with the high magnetic isotropy, this enables 1 to be an excellent magnetic refrigerant for low temperature applications.

Single molecule magnetism in a family of mononuclear β-diketonate lanthanide(III) complexes: rationalization of magnetic anisotropy in complexes of low symmetry

The use of an amino-pyridyl substituted β-diketone, N-(2-pyridyl)-ketoacetamide (paaH), has allowed for the isolation of two new families of isostructural mononuclear lanthanide complexes with general formulae: [Ln(paaH*)2(H2O)4][Cl]3·2H2O (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5) and Y (6)) and [Ln(paaH*)2(NO3)2(MeOH)][NO3] (Ln = Tb (7), Dy (8), Ho (9) and Er (10)). The dysprosium members of each family (3 and 8) show interesting slow magnetic relaxation features. Compound 3 displays Single Molecule Magnet (SMM) behaviour in zero DC field with an energy barrier to thermal relaxation of Ea = 177(4) K (123(2) cm−1) with τ0 = 2.5(8) × 10−7 s, while compound 8 shows slow relaxation of the magnetization under an optimum DC field of 0.2 T with an energy barrier to thermal relaxation of Ea = 64 K (44 cm−1) with τ0 = 6.2 × 10−7 s. Ab initio multiconfigurational calculations of the Complete Active Space type have been employed to elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 2–5 and 8. The orientation of the anisotropic magnetic moments for compounds 2–5 are rationalized using a clear and succinct, chemically intuitive method based on the electrostatic repulsion of the aspherical electron density distributions of the lanthanides.

Structure, Magnetism and Theory of a Family of Nonanuclear CuII5LnIII4–Triethanolamine Clusters Displaying Single‐Molecule Magnet Behaviour

Synthesis, crystal structures and magnetic studies are reported for four new heterometallic Cu(II)-Ln(III) clusters. The reaction of Cu(NO(3))(2)·3H(2)O with triethanolamine (teaH(3)), pivalic acid, triethylamine and Ln(NO(3))(3)·6H(2)O (Ln=Gd, Tb, Dy and Ho) results in the formation of four isostructural nonanuclear complexes of general formula [Cu(II)(5)Ln(III)(4)O(2)(teaH)(4){O(2)CC(CH(3))(3)}(2)(NO(3))(4)(OMe)(4)]·2MeOH·2Et(2)O [Ln=Gd (1), Tb (2), Dy (3) and Ho (4)]. The metal core of each cluster is made up of four face- and vertex-sharing tetrahedral units. Solid-state DC magnetic susceptibility studies reveal competing anti- and ferromagnetic interactions within each cluster leading to large-spin ground states for 1-4. Solid-state AC magnetic susceptibility studies show frequency-dependent out-of-phase (χ(M)) signals for 2-4 below 4 K, suggestive of single-molecule magnet behaviour. Ab initio calculations on one of the anisotropic examples (3) provided a rare set of J values for Dy-Cu and Cu-Cu exchange interactions (Dy-Dy zero), some ferro- and some antiferromagnetic in character, that explain its magnetic behaviour.

Synthesis, structural and magnetic studies of an isostructural family of mixed 3d/4f tetranuclear ‘star’ clusters

DC magnetic studies on new star clusters of formula [Mn(3)Ln(acac)(6)(tea)(2)][Mn(acac)(3)] (Ln = Gd (1) and Dy (2)) and [Fe(3)Ln(acac)(6)(tea)(2)] (Ln = Gd (3) and Dy (4)) show that all cases display weak coupling, with compounds 3 and 4 displaying ferromagnetic J(LnFe) coupling, 3 having a S = 11 ground state.

Planar tetranuclear lanthanide clusters with the Dy4 analogue displaying slow magnetic relaxation

Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar butterfly arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour.

Partial spin crossover behaviour in a dinuclear iron(II) triple helicate

Reported herein are the synthesis, structural, magnetic and Mössbauer spectroscopic characterisation of a dinuclear Fe(II) triple helicate complex [Fe(2)(L)(3)](ClO(4))(4).xH(2)O (x = 1-4), 1(H(2)O), where L is a bis-bidentate imidazolimine ligand. Low temperature structural analysis (150 K) and Mössbauer spectroscopy (4.5 K) are consistent with one of the Fe(II) centres within the helicate being in the low spin (LS) state with the other being in the high-spin (HS) state resulting in a [LS:HS] species. However, Mössbauer spectroscopy (295 K) and variable temperature magnetic susceptibility measurements (4.5-300 K) reveal that 1(H(2)O) undergoes a reversible single step spin crossover at one Fe(II) centre at higher temperatures resulting in a [HS:HS] species. Indeed, the T(1/2)(SCO) values at this Fe(II) centre also vary as the degree of hydration, x, within 1(H(2)O) changes from 1 to 4 and are centred between ca. 210 K-265 K, respectively. The dehydration/hydration cycle is reversible and the fully hydrated phase of 1(H(2)O) may be recovered on exposure to water vapour. This magnetic behaviour is in contrast to that observed in the related compound [Fe(2)(L)(3)](ClO(4))(4)·2MeCN, 1(MeCN), whereby fully reversible SCO was observed at each Fe(II) centre to give [LS:LS] species at low temperature and [HS:HS] species at higher temperatures. Reasons for this differing behaviour between 1(H(2)O) and 1(MeCN) are discussed.

Synthesis and characterization of homo- and heterovalent tetra- hexa- hepta- and decanuclear manganese clusters using pyridyl functionalized ??-diketone, carboxylate and triethanolamine ligands

The syntheses and characterizations are reported for six new homo- and heterovalent manganese clusters, utilizing pyridyl functionalized beta-diketones ligands. The reaction of the trinuclear complex [Mn3O(O2CPh)6(H2O)(Py)2] with 1,3-di(pyridine-2-yl)propane-1,3-dione (dppdH) in CH2Cl2 resulted in a mixed-valence Mn3(II)Mn6(III)Mn(IV) decanuclear cluster of formula [Mn10O7(dppd)3(O2CPh)11] x 4 CH2Cl2 (1). The structure of the core of 1 is based upon a centred tricapped trigonal prism. Reacting Mn(BF4)2 x xH2O with dppdH and triethylamine (NEt3) in CH2Cl2-MeOH gave a rare, homoleptic hexanuclear cluster of formula [Mn(II)6(dppd)8][BF4]4 (2) which has a triangular based core. Reaction of Mn(Y)2 x 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 [Mn(II)7(X)6(tea)(OH)3][Y]2 x solv (3) X = pppd- or dppd- and Y = NO3(-) or BF4(-). The addition of N-(2-pyridinyl)acetoacetamide (paaH) to Mn(Y)2 x 4 H2O 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 x solv (4) (X = NO3(-) or ClO4(-)), whilst the addition of paaH to a mixture of Mn(NO3)2 x 4 H2O, teaH3 and NEt3 in CH2Cl2-MeOH resulted in the formation of a mixed-valence Mn2(II)Mn2(III) tetranuclear butterfly complex of formula [Mn4(paa)4(teaH)2][NO3]2 x 2 MeOH x 2 CH2Cl2 (5). Compound 5 displays the rare Mn(II/III) oxidation state distribution of the body positions being Mn(II) while the wing tips are Mn(III). The in situ formation of the tetranuclear [Mn4(teaH)2(teaH2)2(O2C(CH3)3)2][O2C(CH3)3]2 butterfly complex followed by the addition of Mn(O2CMe)2 x 4 H2O resulted in a mixed-valence Mn4(II)Mn(III)Mn(IV) hexanuclear species of formula [Mn6O2(teaH2)4(O2CMe)4][NO3]2[O2CMe] x CH2Cl2 x MeOH x 2 H2O (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 beta-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 chiM peaks in the AC susceptibility measurements.

Single molecule magnetism in a μ-phenolato dinuclear lanthanide motif ligated by heptadentate Schiff base ligands

The heptadentate Schiff base ligand, 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline (H(3)api), yields [Ln(2)api(2)] species when combined with lanthanide salts under basic conditions. A survey of the magnetic properties of this dinuclear lanthanide motif (Ln = Gd, Tb, Dy, Ho) has identified weak magnetic exchange, antiferromagnetic in nature for the isotropic gadolinium analogue, while single molecule magnetic behaviour is displayed in the case of the anisotropic dysprosium complex.

Post‐Synthetic Monovalent Central‐Metal Exchange, Specific I2 Sensing, and Polymerization of a Catalytic [3×3] Grid of [CuII5CuI4L6]⋅(I)2⋅13 H2O

From a predesigned grid, [Cu(II)5Cu(I)4L6]⋅(I)2⋅13u2009H2O (1), in which LH2 was a pyrazinyl-triazolyl-2,6-substituted pyridine, we successfully synthesized an extended 3D complex, (1)∞[{Cu(II)5Cu(I)8L6}{μ-[Cu(I)3(CN)6]}2⋅2u2009CH3-CN] (2), that displayed unprecedented coexistence of all the five known coordination geometries of copper. Grid 1 displayed monovalent central metal exchange (CME) of Cu(I) for Ag(I) for the first time, as well as the formation of tri-iodide in the crystalline state. These systems were investigated for their magnetic properties. Remarkably, grid 1 showed much higher catalytic activity than the Ag-exchanged product for synthesis of a substituted triazole, 1-benzyl-4-phenyl-1H-1,2,3-triazole.