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An investigation into the physical consequences of including a Jahn–Teller distorted CuIIion within an antiferromagnetically coupled ring, [R2NH2][Cr7CuF8((O2CtBu)16)] is reported. Inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) spectroscopic data are simulated using a microscopic spin Hamiltonian, and show that the two Cr–Cu exchange interactions must be inequivalent. One Cr–Cu exchange is found to be antiferromagnetic and the other ferromagnetic. The geometry of the Jahn–Teller elongation is deduced from these results, and shows that a Jahn–Teller elongation axis must lie in the plane of the Cr7Cu wheel; the elongation is not observed by X-ray crystallography, due to positional disorder of the Cu site within the wheel. An electronic structure calculation confirms the structural distortion of the Cu site. [ABSTRACT FROM AUTHOR]

We explored the possibility to deposit Molecular NanoMagnets (metallorganic complexes) by electrospray. To this end, we developed an apparatus for nondestructive in vacuum deposition of fragile molecular complexes, by modifying a commercial Mass Spectrometer equipped with an electrospray ionization source. Starting from solution, this system creates a beam of ionized molecules which is then transferred into an evacuated region where molecules can be mass selected before deposition. To check the system efficiency, we deposited sub monolayers of oxo-centered carboxylate-bridged trinuclear complexes (Cr3and Cr2Ni) on the Au(111) surface. By XPS and STM we determined the deposited molecule stoichiometry and the surface coverage. Results show that this type of apparatus works well for the in vacuum deposition of molecular nanomagnets and, thanks to the reduced dimensions, it is portable and adaptable to facilities requiring UHV. [ABSTRACT FROM AUTHOR]

Linking polymetallic cages can be a method for creating new structures and new properties. In this tutorial reviewwe use heterometallic anti-ferromagnetically coupled rings (AF-rings) as exemplars for three approaches that can be used to link cage compounds. The first of three routes involves an ion-pair interaction supported by hydrogen-bonding interactions, which allows the synthesis of hybrid rotaxanes among other materials. The second route involves functionalising the exterior of the AF-ring so that it will act as a Lewis base; complexes involving coordination of pyridine to bridging monometallic and dimetallic fragments are discussed. The third route involves creating a vacancy on one site of the AF-ring, and then using the ring as a Lewis acid. Di-imine ligands can then be used to link the AF-rings into dimers. A brief discussion of the physical properties of these systems is also included. [ABSTRACT FROM AUTHOR]

We report a detailed physical analysis on a family of isolated, antiferro-magnetically (AF) coupled, chromium(iii) finite chains, of general formula (Cr(RCO2)2F)nwhere the chain length n= 6 or 7. Additionally, the chains are capped with a selection of possible terminating ligands, including hfac (= l,l,l,5,5,5-hexafluoropentane-2,4-dionate(l-)), acac (= pentane-2,4-dionate(l-)) or (F)3. Measurements by inelastic neutron scattering (INS), magnetometery and electron paramagnetic resonance (EPR) spectroscopy have been used to study how the electronic properties are affected by nand capping ligand type. These comparisons allowed the subtle electronic effects the choice of capping ligand makes for odd member spin 3/2 ground state and even membered spin 0 ground state chains to be investigated. For this investigation full characterisation of physical properties have been performed with spin Hamiltonian parameterisation, including the determination of Heisenberg exchange coupling constants and single ion axial and rhombic anisotropy. We reveal how the quantum spin energy levels of odd or even membered chains can be modified by the type of capping ligand terminating the chain. Choice of capping ligands enables Cr–Cr exchange coupling to be adjusted by 0, 4 or 24%, relative to Cr–Cr exchange coupling within the body of the chain, by the substitution of hfac, acac or (F)3capping ligands to the ends of the chain, respectively. The manipulation of quantum spin levels vialigands which play no role in super-exchange, is of general interest to the practise of spin Hamilton modelling, where such second order effects are generally not considered of relevance to magnetic properties. [ABSTRACT FROM AUTHOR]

The reaction of cobalt salts with phosphonic acids in the presence of 6-chloro-2-hydroxypyridine as a co-ligand, using sodium methoxide as a base, leads to a series of new polymetallic cobalt cages. Variation of the phosphonate present and the cobalt salt leads to {Co6Na8}, {Co12}, {Co13Na6}, {Co14Na4} and {Co15Na} cages, all of which have been characterized by X-ray crystallography. Using lithium methoxide produces a sixth cage with a {Co6Li9} core. The structures are, in general, extremely irregular with no structural motifs common to the six cages. Magnetic studies of these cages show a general decline in the product χmTwith T, but for {Co13Na6}, {Co15Na} and {Co12} there are maxima at low temperature, which suggest non-diamagnetic ground states. Investigation of the dynamic behaviour of the magnetisation of these complexes shows that the {Co13Na6}, and possibly the {Co12} cage, appear to display slow relaxation of magnetisation. [ABSTRACT FROM AUTHOR]

The optical and magnetic properties of the multi-metal rings [NH2R2][Cr7MF8(O2CCMe3)16], where M = Cd(ii), Mn(ii) or Ni(ii), have been studied using variable-field and variable-temperature magnetic circular dichroism (MCD) in the UV-visible spectra. Spectra of samples were recorded in a frozen organic matrix or cast in a polymethacrylate (PMMA) polymer film between 1.7 and 75 K. The spectra are characteristic of the Cr(iii) ion (d3) in a rhombic field when M = Cd(ii). In the case that M = Ni(ii) additional optical transitions arise from the d8 ion whereas for M = Mn(ii) no additional transitions are observed. The influence of magnetic exchange is apparent from a change in the sign of the MCD signal between complexes in which the hetero-atom has a local spin moment greater, or less, than that of Cr(iii), S = 3/2, namely, Mn(ii), S = 5/2, and Ni(ii), S = 1. The exchange coupling generates a manifold of thermally accessible electronic states that give rise to variations in MCD intensity as well as additional spectral features as the temperature is raised. Equations have been derived to relate the splittings observed in the optical spectrum to the single-ion ground state zero-field splittings of chromium(iii). There is reasonable agreement between the sign and magnitude of the contribution to the cluster anisotropy from that of the single ion with values estimated from other techniques. [ABSTRACT FROM AUTHOR]

The optical and magnetic properties of the multi-metal rings [NH2R2][Cr7MF8(O2CCMe3)16], where M = Cd(ii), Mn(ii) or Ni(ii), have been studied using variable-field and variable-temperature magnetic circular dichroism (MCD) in the UV-visible spectra. Spectra of samples were recorded in a frozen organic matrix or cast in a polymethacrylate (PMMA) polymer film between 1.7 and 75 K. The spectra are characteristic of the Cr(iii) ion (d3) in a rhombic field when M = Cd(ii). In the case that M = Ni(ii) additional optical transitions arise from the d8 ion whereas for M = Mn(ii) no additional transitions are observed. The influence of magnetic exchange is apparent from a change in the sign of the MCD signal between complexes in which the hetero-atom has a local spin moment greater, or less, than that of Cr(iii), S = 3/2, namely, Mn(ii), S = 5/2, and Ni(ii), S = 1. The exchange coupling generates a manifold of thermally accessible electronic states that give rise to variations in MCD intensity as well as additional spectral features as the temperature is raised. Equations have been derived to relate the splittings observed in the optical spectrum to the single-ion ground state zero-field splittings of chromium(iii). There is reasonable agreement between the sign and magnitude of the contribution to the cluster anisotropy from that of the single ion with values estimated from other techniques. [ABSTRACT FROM AUTHOR]

The synthesis of a series of heterometallic rings and chains is reported. The family is based on the octanuclear cages of general formula [H2NR2][M7M′F8(O2CR′)16], where M is a trivalent metal (Cr, Fe, V, Al, Ga or In), M′ is a divalent metal (Mn, Fe, Co, Ni, Mg, Zn, Cd), R is a linear alkyl chain and O2CR′ is one of around twenty carboxylates. Other members of the family with nonametallic and decametallic cores are described, and some new physics is outlined, including initial investigations of the proposed application of {Cr7Ni} rings as Qubits in quantum information processing. [ABSTRACT FROM AUTHOR]

Synthesis and structure of a cyclic tetranuclear Ni2Gd2complex bridged by amino acidato ligands, with an S= 9 spin ground state, derived from ferromagnetic spin-coupling between SGd= 7/2 and SNi= 1 are reported. [ABSTRACT FROM AUTHOR]

A new class of oxygen donor ligands is described and preliminary results using these ligands are given which show they can be used to make polymetallic cages. [ABSTRACT FROM AUTHOR]

Synthetic, structural and magnetic studies of a new Fe(ii) single chain magnet are reported. [ABSTRACT FROM AUTHOR]

Synthetic and structural studies of Cr horseshoes are reported which show that these compounds demonstrate a rich supramolecular chemistry through H-bonding interactions, and can act as ligands for metal clusters. [ABSTRACT FROM AUTHOR]

The synthesis and magnetic properties of enneametallic and octametallic Fe(iii) cage complexes from tetraazamacrocycle ligands (1,7-H2DO2A) and (H3DO3A) respectively, are reported. [ABSTRACT FROM AUTHOR]

Three new polymetallic nickel(ii) phosphonate complexes are reported; in one cage the twelve nickel centres are arranged at the vertices of a truncated tetrahedron in a similar manner to a Keggin ion. [ABSTRACT FROM AUTHOR]

The synthesis of a new pentanuclear V(iii) complex [V5O2(Me3CCO2)9Cl2] (1) by solid state methods is described. [ABSTRACT FROM AUTHOR]

Cyclic octanuclear complexes, each containing seven group 13 metals and one d-block metal are reported and preliminary physical characterisation of the compounds discussed. [ABSTRACT FROM AUTHOR]

The optical and magnetic properties of the multi-metal rings [NH2R2][Cr7MF8(O2CCMe3)16], where M = Cd(ii), Mn(ii) or Ni(ii), have been studied using variable-field and variable-temperature magnetic circular dichroism (MCD) in the UV-visible spectra. Spectra of samples were recorded in a frozen organic matrix or cast in a polymethacrylate (PMMA) polymer film between 1.7 and 75 K. The spectra are characteristic of the Cr(iii) ion (d3) in a rhombic field when M = Cd(ii). In the case that M = Ni(ii) additional optical transitions arise from the d8 ion whereas for M = Mn(ii) no additional transitions are observed. The influence of magnetic exchange is apparent from a change in the sign of the MCD signal between complexes in which the hetero-atom has a local spin moment greater, or less, than that of Cr(iii), S = 3/2, namely, Mn(ii), S = 5/2, and Ni(ii), S = 1. The exchange coupling generates a manifold of thermally accessible electronic states that give rise to variations in MCD intensity as well as additional spectral features as the temperature is raised. Equations have been derived to relate the splittings observed in the optical spectrum to the single-ion ground state zero-field splittings of chromium(iii). There is reasonable agreement between the sign and magnitude of the contribution to the cluster anisotropy from that of the single ion with values estimated from other techniques. [ABSTRACT FROM AUTHOR]