This work focuses on the structural and magnetic characterization of arrays of cobalt nanowires, with diameters in the range 100–400 nm and lengths of $\text{L⩽6\hspace{0.05em}μ}\mathrm{m},$ produced by electrodeposition in polycarbonate membrane pores. Diffraction patterns of Co nanowires indicate that Co is stabilized in the hcp structure with a preferential (0001) texture oriented close to the perpendicular direction of the wires axes. Magnetic measurements at room temperature reveal that magnetization undergoes a change in the easy axis as the length of the wires increases. Clearly, the easy axis of the shortest wires is oriented along the axis of the wire. In the case of the longest wires, a crossover of the easy axis is observed, from the perpendicular to the parallel direction to the wire for the shortest. This magnetic behavior is explained through a simple magnetostatic model, which takes into account the dipolar interactions among wires, the demagnetizing field, and the magnetocrystalline anisotropy of Co.

Five new Pb(II) complexes of hydrazone-based and Schiff-based ligands and three different anionic co-ligands (azide, thiocyanate and bromide) have been synthesized and characterized by structural, analytical and spectroscopic methods. This variety of ligands can coordinate to the Pb(II) metal center in a tridentate or tetradentate fashion via a different combination of any of nitrogen, oxygen and sulphur donor atoms. Moreover, the organic ligands can be in mono-deprotonated or neutral forms. By using single-crystal X-ray crystallography, we show that the synthesized complexes aggregate into larger supramolecular entities due to the formation of noncovalent tetrel bonding interactions. The Pb(II) center is hemidirectionally coordinated even in those complexes where the coordination number is six. Consequently, this is sterically ideal for establishing tetrel bonding interactions with electron-rich nitrogen, bromide or sulphur atoms. These contacts are significantly larger than the sums of the covalent radii. Hence, they can be described as non-covalent tetrel bonding interactions. They interconnect the covalently bonded units into supramolecular assemblies (dimers or tetramers). The contribution of contacts involving the Pb atom has been studied using Hirshfeld surface analysis and fingerprint plots. We have analysed the supramolecular assemblies observed in the solid state by means of DFT calculations and characterized them using Bader's theory of atoms-in-molecules.

We have prepared some transition and post-transition metal complexes derived from the pentadentate thiosemicarbazone ligand bis(4-N-ethylthiosemicarbazone)-2,6-diacetylpyridine H₂L^Et, by both chemical and electrochemical procedures. The complexes have been synthesised and fully characterised, including the crystal structures for the ligand H₂L^Et and its manganese, cadmium and lead complexes. We have also performed multinuclear ¹⁰⁹Ag, ¹¹³Cd, ¹¹⁹Sn and ²⁰⁷Pb studies for silver, cadmium, tin and lead compounds, respectively. Moreover we present here a comparative study on the different structures found for pentadentate thiosemicarbazonate complexes, trying to check the influence of different factors, such as experimental procedure, size of metal, structure of the ligand, and metal oxidation state, on the final structure of the complex formed. Our aim is gaining a better insight into the coordination trends of pentadentate thiosemicarbazone ligands.

The influence of the metal size in the nuclearity of the complexes derived from the hydrazone ligand 2,6-bis(1-salicyloylhydrazonoethyl)pyridine [H₄daps] has been investigated. We have synthesised a series of new complexes [M(H_xdaps)]·yH₂O, (x = 2,3; y = 0–3) with M = Ag (1), Cd (2), Al (3), Sn (4) and Pb (6), using an electrochemical procedure. The crystal and molecular structures have been determined for the mononuclear complexes [Sn(H₂daps)(H₂O)₂]·4H₂O (5) and [Pb(H₂daps)(CN)][Et₄N] (7). Complex 5 is the first neutral Sn(II) complex derived from a pentadentate hydrazone Schiff base ligand. Complex 7 shows the lead coordinated to the hydrazone donor set and a cyanide ligand, being the first reported complex with the lead atom coordinated to a monodentate cyanide group. Additionally, we have synthesised the lead complex using chemical conditions, in the presence of sodium cyanide which allowed us to isolate the neutral complex [Pb(H₂daps)] (8). Evaporation of these mother liquors led the novel compound [Pb(Hdaphs)(CH₃COO)] (9). Complex 9 shows the initial ligand hydrolysed in one of the imine bonds giving rise to a new tetradentate ligand [H₂daphs] coordinated to the lead atom and a bidentate acetate group. Moreover, the solution behaviour of the complexes has been investigated by ¹H, ¹¹³Cd, ¹¹⁷Sn and ²⁰⁷Pb NMR techniques. In particular multinuclear NMR has provided new useful data to correlate factors such as oxidation state, coordination number and nature of the kernel donor atoms due to the new coordination found in complexes 5 and 7. The comparative study of the structures of the complexes derived from this pentadentate [N₃O₂] hydrazone ligand let us to conclude that the metal size is a key factor to control the nuclearity of the complexes derived from the ligand [H₄daps].

The coordinative chemistry of the tridentate thiosemicarbazone ligand 2-pyridinecarboxaldehyde 4-N-ethylthiosemicarbazone (HL^Et ) has been explored by using an electrochemical methodology. All the complexes have been characterized using analytical and spectroscopic techniques. In the case of copper we have isolated two different complexes, with Cu(L^Et)₂·4H₂O (6) and [Cu₂(L^Et)₂(SO₄)] (7) formulae. The sulfate group coordinated to the copper atoms in 7 was probably released to the media as a consequence of a desulfurization process. Single X-ray crystallography has been carried out for the ligand HL^Et and the complexes 7, [Ag₆(L^Et)₆]·CH₃CN (9) and [Pb(L^Et)₂ ] (12). The copper(II) complex 7 is a dimer compound in which two antiparallel monodeprotonated ligands are coordinated to two copper centres by establishment of μ₂-thiolate bridges and the additional coordination of a sulfate group bridging the two metal atoms. The silver complex 9 is an unusual hexanuclear cluster compound with a wheel-type conformation, while the lead complex 12 is a monomer which exhibits the lone pair effect. A structural comparative study of the electrochemically obtained complexes derived from HL^X ligands (X= Me, Et and Ph) have been performed. Finally, the solution behaviour of the complexes was checked by NMR, UV and fluorescence studies.