Perla Elizondo Martínez

Recent advances on ditopic ligands

Recent (2000–2009) achievements on ditopic ligands are reviewed. The ditopic ligands are mainly represented by N-, P-, O-, and S-containing organic molecules or their N, O-, N, S-, and N, P-combinations with azine, azole, amine, azide, β-diketone, crown ether, carboxylate, phenanthroline, oxazoline, phosphole, and thiophene moieties, among others. A series of mono- and polynuclear transition and f-metal complexes with these ligands, in particular cluster- and supramolecular unit-containing complexes, have been obtained and characterized spectroscopically and electrochemically.

Metal Complexes Containing Natural and Artificial Radioactive Elements and Their Applications

Recent advances (during the 2007–2014 period) in the coordination and organometallic chemistry of compounds containing natural and artificially prepared radionuclides (actinides and technetium), are reviewed. Radioactive isotopes of naturally stable elements are not included for discussion in this work. Actinide and technetium complexes with O-, N-, N,O, N,S-, P-containing ligands, as well π-organometallics are discussed from the view point of their synthesis, properties, and main applications. On the basis of their properties, several mono-, bi-, tri-, tetra- or polydentate ligands have been designed for specific recognition of some particular radionuclides, and can be used in the processes of nuclear waste remediation, i.e., recycling of nuclear fuel and the separation of actinides and fission products from waste solutions or for analytical determination of actinides in solutions; actinide metal complexes are also usefulas catalysts forcoupling gaseous carbon monoxide, as well as antimicrobial and anti-fungi agents due to their biological activity. Radioactive labeling based on the short-lived metastable nuclide technetium-99m (99mTc) for biomedical use as heart, lung, kidney, bone, brain, liver or cancer imaging agents is also discussed. Finally, the promising applications of technetium labeling of nanomaterials, with potential applications as drug transport and delivery vehicles, radiotherapeutic agents or radiotracers for monitoring metabolic pathways, are also described.

N,N′-Bis(2-amino­benz­yl)ethane-1,2-diaminium dinitrate

In the title salt, C16H24N4 2+·2NO3 −, both the cation and anion are placed in general positions, although the cation displays non-crystallographic inversion symmetry, with the aliphatic chain extended in an all-trans conformation. The benzene rings are almost parallel, with a dihedral angle between their mean planes of 3.3 (6)°. The nitrate ions are placed in the vicinity of the protonated amine groups, forming efficient N—H⋯O inter-ion hydrogen bonds. Each nitrate ion in the asymmetric unit bridges two symmetry-related cations, forming an R 4 4(18) ring, a common motif in organic ammonium nitrate salts. This results in the formation of chains along [010] with alternating cations and anions. The neutral amine groups are involved in slightly weaker N—H⋯O hydrogen bonds with the nitrate O atoms, and there are also a number of C—H⋯O hydrogen bonds present. The resulting supramolecular structure is based on a two-dimensional network extending in the ab plane.

Tris[2-(2H-indazol-2-yl)eth-yl]amine.

The title tertiary amine, C27H27N7, a potential tripodal ligand for coordination chemistry, crystallizes with the central N atom located on a threefold axis of a trigonal cell. The gauche conformation of the N(amime)—CH2—CH2—N(indazole) chain [torsion angle = −64.2 (2)°] places the pendant 2H-indazole heterocycles surrounding the symmetry axis, affording a claw-like shaped molecule. Two symmetry-related indazole planes in the molecule make an acute angle of 60.39 (4)°. The lone pair of the tertiary N atom is located inside the cavity, and should thus be inactive (as a ligand). In the crystal, neither significant π–π nor C—H⋯π interactions between molecules are found.

N,N′-Bis(2-aza­niumylbenz­yl)ethane-1,2-diaminium tetra­chloride

The title compound, C16H26N4 4+·4Cl−, is based on a fully protonated tetraamine. In the cation, both benzene rings are connected by an all-trans chain, and the rings are almost parallel, with an angle between the mean planes of 8.34 (12)°. The benzene rings are arranged in such a way that the NH3 + substituents are oriented cis with respect to the central chain. This arrangement is a consequence of multiple N—H⋯Cl hydrogen bonds, involving all N—H groups in the cation and the four independent Cl− anions. These contacts have strengths ranging from weak to strong (based on H⋯Cl separations), and generate a complex three-dimensional crystal structure with no preferential crystallographic orientation for the contacts.

Tris{2-[(2-amino­benzyl­idene)amino]­ethyl}amine

The title Schiff base, C27H33N7, is a tripodal amine displaying C 3 symmetry, with the central tertiary N atom lying on the threefold crystallographic axis. The N—CH2—CH2—N conformation of the pendant arms is gauche [torsion angle = 76.1 (3)°], which results in a claw-like molecule, with the terminal aniline groups wrapped around the symmetry axis. The lone pair of the apical N atom is clearly oriented inwards towards the cavity, and should thus be chemically inactive. The amine NH2 substituents lie in the plane of the benzene ring to which they are bonded. With such an arrangement, one amine H atom forms an S(6) motif through a weak N—H⋯N hydrogen bond with the imine N atom, while the other is engaged in an intermolecular N—H⋯π contact involving the benzene ring of a neighbouring molecule related by inversion. The benzene rings also participate in an intramolecular C—H⋯π contact of similar strength. In the crystal structure, molecules are separated by empty voids (ca 5% of the crystal volume), although the crystal seems to be unsolvated.

2,2'-(Propane-1,3-di-yl)bis-(2H-indazole).

The title molecule, C17H16N4, is a bis-indazole crystallized in the rare 2H-tautomeric form. Indazole heterocycles are connected by a propane C3 chain, and the molecule is placed on a general position, in contrast to the analogous compound with a central C2 ethane bridge, which was previously found to be placed on an inversion center in the same space group. In the title molecule, indazole rings make a dihedral angle of 60.11 (7)°, and the bridging alkyl chain displays a trans conformation, resulting in a W-shaped molecule. In the crystal, molecules interact weakly through π–π contacts between inversion-related pyrazole rings, with a centroid–centroid separation of 3.746 (2) Å.