Química de coordinación de un ligando derivado de tripticeno: en la búsqueda de sensores ópticos

Traballo Fin de Grao en Química. Curso 2013-2014The present work describes the synthesis of the new Schiff base H2L, containing a trypticene residue, and its reactivity towards niquel(II), copper(II), zinc(II), palladium(II), silver(I) and cadmium(II). This study discusses the reaction conditions that allow isolating trinuclear Zn and Ni complexes. The experimental requirements to obtain coordination compounds with the remaining metal ions, although sought, could not be set. Analytical and spectrometric characterization of the Zn and Ni compounds completely agrees with the trinuclear nature of the complexes. The fluorescence study of the ligand in solution, both as free ligand and in the presence of ZnII and NiII, shows that H2L is fluorescent and that the presence of the metal ions partially quenches the fluorescence emission of the ligand itself. Thus, given the variation of the luminescence properties in the presence of metal ions, the ability of H2L to act as a luminescence chemosensor was investigated. The results show that the experimental conditions tested do not permit to stabilize the optical response of the ligand in the presence of metal ions. In addition, H2L was checked as an absorbance chemosensor, and in this case the results demonstrate that it can be used to quantify the presence of Zn2+ and Ni2+ in the medium

Mononuclear lanthanide complexes with 18-crown-6 ether: synthesis, characterization, magnetic properties, and theoretical studies

A family of lanthanide metal complexes with general formula [Ln(H2O)3(18-crown-6)](ClO4)3 (Ln: TbIII, DyIII, ErIII and YbIII) has been synthesized. Their magnetic properties have been characterized by DC and AC SQUID measurements and analyzed with the help of CASSCF-type calculations. The DyIII and YbIII compounds show slow relaxation of the magnetization under an external magnetic field. The analysis of the dependence of the relaxation time with the temperature and external magnetic field reveals that the main contributions are respectively the quantum tunneling and the Raman term, respectively. The analysis of the beta electron density and electrostatic potentials indicate that the axial ligands (three water molecules) generate a relatively small repulsion with the lanthanide electron density being the reason of the moderate magnetic anisotropy found in these systems

Slow-spin relaxation of a low-spin S = 1/2 FeIII carborane complex

In this communication, we report the first evidence of slow-spin relaxation of a low-spin FeIII carborane complex. Iron S=1/2 complexes showing such behaviour are specially appealing as qubits candidates because they fulfil some of the main requirements to reach long decoherence times: moderate magnetic anisotropy, small spin, metal element mainly with zero-nuclear spin and furthermore, large versatility to introduce chemical modifications

[UF6](2-): A molecular hexafluorido actinide(IV) complex with compensating spin and orbital magnetic moments

The first structurally characterized hexafluorido complex of a tetravalent actinide ion, the [UF6]2- anion, is reported in the (NEt4)2[UF6]2H2O salt (1). The weak magnetic response of 1 results from both U(IV) spin and orbital contributions, as established by combining X-ray magnetic circular dichroism (XMCD) spectroscopy and bulk magnetization measurements. The spin and orbital moments are virtually identical in magnitude, but opposite in sign, resulting in an almost perfect cancellation, which is corroborated by ab initio calculations. This work constitutes the first experimental demonstration of a seemingly non-magnetic molecular actinide complex carrying sizable spin and orbital magnetic moments

A low spin manganese(IV) nitride single molecule magnet

Structural, spectroscopic and magnetic methods have been used to characterize the tris(carbene) borate compound PhB(MesIm)(3)Mn equivalent to N as a four-coordinate manganese(IV) complex with a low spin (S = 1/2) configuration. The slow relaxation of the magnetization in this complex, i.e. its single-molecule magnet (SMM) properties, is revealed under an applied dc field. Multireference quantum mechanical calculations indicate that this SMM behavior originates from an anisotropic ground doublet stabilized by spin-orbit coupling. Consistent theoretical and experiment data show that the resulting magnetization dynamics in this system is dominated by ground state quantum tunneling, while its temperature dependence is influenced by Raman relaxation