Juan Manuel Germán-Acacio

Strategies for the design and synthesis of pincer-based dendrimers: Potential applications

Abstract The excellent thermal and chemical stability and robustness of ECE-pincer metal complexes make these species promising candidates as medical and therapeutics tools; tools such as: biomarkers, sensors, anticarcinogenic agents, surface plasmon resonance enhancers, etc. In this sense, one of the main interests is the hybridization of organometallic species anchored or incorporated in biological molecules, i.e., mainly in enzymes. Also of interest is the preparation of dendritic ECE-pincer metal complexes as potential drug carriers. Thus far, several papers describing dendrimeric skeletons (e.g., PAMAM) have been reported with promising drug delivery abilities. However, to the best of our knowledge, there are no reports describing the utilization of dendritic ECE-pincer metal complexes as drug carriers. In addition, an incipient development of bioorganometallic conjugates, combining the properties of ECE-pincer metal complexes covalently anchored to diverse biological molecules (peptides, aminoacids, carbohydrates, anticarcinogenic agents, proteins, enzymes, etc.), have been synthetized in an effort to generate potential sensors or biomarkers, exploiting the properties of the biomolecules used (water solubility, size, chiral environment, etc.). In this chapter, we describe the development of metallopincer dendrimers and the potential applications of more compact metallopincer species in medical, therapeutic, and other fields.

Solvatomorphism: the inclusion of unexpected guests. An interesting case of study of different solvates in the tecton [Pd(1,10-phen)(2,3,5,6-S-C6F4H)2]

In this work is described the crystalline structures of a non-solvated tecton [Pd(1,10-phen)( 2,3,5,6-S-C6F4H)2] (1) (phen = 1,10-phenanthroline) and three different solvatomorphs [Pd(1,10-phen)( 2,3,5,6-S-C6F4H)2]·S, S = C6H6 (2), S = C6H6-Cl (3) and S = C6H6-Br (4). In addition is described the formation of the crystalline solvate [Pd(1,10-phen)( 2,3,4,5,6-SC6F5)2]·C6H6-Br (5) for comparison purposes with the former compounds. In this case we are interested in getting deeper in the knowledge of the fascinating phenomena of solvatomorphism. Thus, we performed computational studies in order to elucidate the energetics involved of the non-solvated tecton and their solvatomorphs in attempt to establish how these unexpected guests are encrusted within the unit cell.

trans-Bis(μ-benzene­thiol­ato-κ2S:S)bis[chlorido­(tri­phenyl­phosphane-κP)palladium(II)] chloro­form disolvate

The title compound, [Pd2Cl2(C6H5S)2(C18H15P)2]·2CHCl3, contains a centrosymmetric dinuclear palladium complex with the PdII cation in a slightly distorted square-planar coordination environment. The PdII cations are bridged by the S atoms of two benzenethiolate ligands with different Pd—S distances [2.2970 (11) and 2.3676 (11) Å]. The coordination of the metal atom is completed by a chloride anion [2.3383 (11) Å] and a triphenylphosphane ligand [2.2787 (11) Å]. Weak C—H⋯Cl interactions are present between complex molecules and the CHCl3 solvent molecule. The latter is disordered over two positions in a 0.792 (8):0.208 (8) ratio. The crystal under investigation was found to be twinned by nonmerohedry, with a fraction of 73.4 (1)% for the major twin component.

1,3-Bis[(tert-butylsulfanyl)methyl]-2,4,6-trimethylbenzene.

The complete molecule of the title compound, C19H32S2, is generated by crystallorgaphic twofold symmetry, with three C atoms lying on the axis. The Car—C—S—C (ar = aromatic) torsion angle is 156.2 (2) °. In the crystal, the molecules are linked by very weak C—H⋯S interactions, generating [001] chains.

1,3-Bis[(naphthalen-2-ylsulfan-yl)meth-yl]benzene.

Molecules of the title compound, C28H22S2, are located on a crystallographic mirror plane with one half-molecule in the asymmetric unit. The dihedral angle between the phenyl ring and the naphthyl unit is 83.14 (7)°. In the crystal, molecules are interconnected by C—H⋯S and C—H⋯π interactions.

3-[1-(3-Hy-droxy-benz-yl)-1H-benzimid-azol-2-yl]phenol dimethyl sulfoxide monosolvate.

Crystals of the title compound were obtained as a 1:1 dimethyl sulfoxide solvate, C20H16N2O2·C2H6O. The molecular conformation of the organic molecule is similar to that in the previously reported unsolvated structure [Eltayeb et al. (2009 ▶). Acta Cryst. E65, o1374–o1375]. Thus, the dihedral angles formed by the benzimidazole moiety with the two benzene rings are 57.54 (4) and 76.22 (5)°, and the dihedral angle between the benzene rings is 89.23 (5)°. In the crystal, a three-dimensional network features O—H⋯O, O—H⋯N and O—H⋯S hydrogen bonds, as well as C—H⋯O and C—H⋯π interactions.