Jordi Esteban

High nuclearity in azido/oximate chemistry: Ni14 and Ni13 clusters with S = 6 and 9 ground states.

In the present work, we report a family of Ni(14) and unprecedented Ni(13) clusters linked by end-on azido and oximato bridges. Ferrimagnetic response gives S = 6 and 9 ground states, resulting in the largest nuclearities and spins in nickel oximato chemistry.

Triangular Nickel Complexes Derived from 2-Pyridylcyanoxime: An Approach to the Magnetic Properties of the [Ni3(μ3-OH){pyC(R)NO}3]2+ Core

A series of nickel complexes with nuclearity ranging from Ni(3) to Ni(6) have been obtained by treatment of a variety of nickel salts with the 2-pyridylcyanoxime ligand. The reported compounds have as a common structural feature the triangular arrangement of nickel cations bridged by a central μ(3)-oxo/alkoxo ligand. These compounds are simultaneously the first nickel derivatives of the 2-pyridylcyanoxime ligand and the first examples of isolated, μ(3)-O triangular pyridyloximate nickel complexes. Magnetic measurements reveal antiferromagnetic interactions promoted by the μ(3)-O and oximato superexchange pathways and comparison of the experimental structural and magnetic data with DFT calculations give an in-depth explanation of the factors that determine the magnetic interaction in this kind of system.

Ni5, Ni8, and Ni10 Clusters with 2,6-Diacetylpyridine-dioxime as a Ligand

In the present work, novel coordination possibilities for the system dapdoH(2)/Ni(II) (dapdoH(2) = 2,6-diacetylpyridine-dioxime) have been explored. Depending on the starting reagents and solution conditions, several clusters with nuclearities ranging from Ni(5) to Ni(10) were achieved and structurally characterized, namely, [Ni(5)(R-COO)(2)(dapdo)(2)(dapdoH)(2)(N(CN)(2))(2)(MeOH)(2)] in which R-COO(-) = benzoate (1) or 3-chlorobenzoate (2), [Ni(8)(dapdo)(4)(NO(3))(4)(OH)(4)(MeOH)(4)] (3), and [Ni(10)(dapdo)(8)(N(CN)(2))(2)(MeO)(MeOH)](NO(3)) (4). For the first time, pentadentate coordination for the dapdo(2-) ligand has been established. All compounds show a combination of square-planar and octahedrally coordinated nickel atoms. According to the Ni(2)(sp)Ni(3)(Oh) (1 and 2), Ni(4)(sp)Ni(4)(Oh) (3), and Ni(4)(sp)Ni(6)(Oh) (4) environments, these systems magnetically behave as trimer, tetramer, and hexanuclear clusters, respectively. dc magnetic measurements in the 2-300 K range of temperature reveal antiferromagnetic coupling for all compounds, and the correlation of the superexchange interaction with the torsion angles involving the oximato bridges is experimentally confirmed.

First Structural and Magnetic Studies of Ni Clusters Containing 2,6-Diacetylpyridine-dioxime as a Ligand

In the present work, coordination possibilities of the system dapdoH(2)/Ni(2+), being dapdoH(2) = 2,6-diacetylpyridine dioxime, have been explored, offering as a result a number of unprecedented clusters with a variety of topologies and magnetic behaviors. Depending on the precursors and reaction conditions, several compounds named [Ni(2)(dapdo)(2)] (1), [Ni(3)(OH)(BzO)(3)(dapdo)(dapdoH(2))(H(2)O)] x1.25 H(2)O (2), [Ni(3)(AcO)(4)(dapdoH)(2)(H(2)O)(2)] x H(2)O (3), and [Ni(4)(AcO)(3)(dapdo)(dapdoH)(2)(H(2)O)(3)] x (AcO) x 3 H(2)O (4) were achieved and structurally well-characterized. Dc magnetic measurements were carried out in the 2-300 K range revealing antiferromagnetic interactions for (2-4) compounds and diamagnetic response for the square planar coordinated complex (1).

New topologies in pentanuclear nickel/oximato clusters: structural and magnetic characterization.

In the present work, five new Ni5 clusters employing the versatile 2-pyridylcyanoxime ligand have been synthesized and chemically, structurally, and magnetically characterized. The crystallographic examination of these Ni5 clusters together with those already published in the literature, giving a total number of 14 complexes, exhibiting up to 8 different topologies for which the relationship between topology, reaction conditions and magnetic response has been analyzed. DC magnetic measurements were carried in the 300-2 K range for the new complexes and the analysis of the experimental data revealed an antiferromagnetic response for the oximato mediated interactions with a variety of ground states (S = 0, 1, 3) as function of the cluster topology.

Anionic Guests in Prismatic Cavities Generated by Enneanuclear Nickel Metallacycles

The combination of polydentate aminated ligands with the 2-pyridyloxime-nickel-azide system leads to series of clusters with unprecedented topologies. Among them, a remarkable family of {Ni9} metallacycles that are capable of selective encapsulation of azide/halide anions in a cryptand-like cavity through hydrogen-bond interactions has been characterized.

A Paleoneurohistological Study of 3,000-Year-Old Mummified Brain Tissue from the Mediterranean Bronze Age

Objectives: Mummified nervous tissue is very rarely found in ancient remains and usually corresponds to corpses which were frozen or preserved in bogs, conditions which limit tissue autolysis and bacterial degradation. Here, we show the unusual finding of spontaneously mummified brain tissue from several individuals from the little known megalithic talaiotic culture of the island of Minorca, dating approximately 3,000 years before present and corresponding to the late Mediterranean Bronze Age. Methods: These individuals were part of an intact burial site containing 66 subjects. Intracraneal samples were carefully rehydrated with Sandison’s solution. We used classical histochemical as well as 2D and 3D (scanning) electron-microscopic techniques. Results: We provide evidence of the nervous nature of the samples as well as a detailed description of the morphological features of these ancient tissues. The intracranial material consisted of well-preserved eosinophilic reticular tissue and, although mostly absent, some exceptional pigment-containing neurons were identified. Conclusions: We present a detailed morphological analysis which can provide valuable information and guidelines for the interpretation of this scarce type of mummified samples and provide explanations for this surprising preservation.

Histopathological Study of a Mummified Eye and Optic Nerve from a Strangled Peruvian Mummy

We present the histopathological findings of a naturally mummified eye from the Peruvian Lambayeque culture (900-1,200 AD), in which rehydration, light microscopy, and scanning electron microscopy allowed a detailed analysis of several eye tissues including the eyelids, sclera, and optic nerve, the latter showing evidence of hemorrhage likely related to the documented strangulation as the cause of death. We conclude that histopathological analysis of rehydrated mummified tissues can provide valuable information from fragile eye structures including the optic nerve, and these findings can be useful from a forensic point of view.