The synthesis of octahedral copper and zinc coordination complexes containing ligands of the type 6R,2,4-bis(3,5-dimethylpyrazol-1-yl)triazine is described. They exhibit the simultaneous presence of C-H/pi and anion-pi interactions on both sides of the same triazine ring. When the pyrazolyl groups are not methylated, lone pair-pi and anion-pi interactions coexist on the same triazine ring. In addition, the interplay between C-H/pi and anion-pi interactions is studied by means of high level correlation ab initio calculations. They demonstrate that synergistic effects are present when both interactions coexist. These synergistic effects have been evaluated using the genuine non-additivity energies and symmetry adapted perturbation theory (SAPT).

The synthesis and characterization of Pt(II) (1 and 2) and Ru(II) arene (3 and 4) or polypyridine (5 and 6) complexes is described. With the aim of having a functional group to form bioconjugates, one uncoordinated carboxyl group has been introduced in all complexes. Some of the complexes were selected for their potential in photodynamic therapy (PDT). The molecular structures of complexes 2 and 5, as well as that of the sodium salt of the 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine ligand (cptpy), were determined by X-ray diffraction. Different techniques were used to evaluate the binding capacity to model DNA molecules, and MTT cytotoxicity assays were performed against four cell lines. Compounds 3, 4, and 5 showed little tendency to bind to DNA and exhibited poor biological activity. Compound 2 behaves as bonded to DNA probably through a covalent interaction, although its cytotoxicity was very low. Compound 1 and possibly 6, both of which contain a cptpy ligand, were able to intercalate with DNA, but toxicity was not observed for 6. However, compound 1 was active in all cell lines tested. Clonogenic assays and apoptosis induction studies were also performed on the PC-3 line for 1. The photodynamic behavior for complexes 1, 5, and 6 indicated that their nuclease activity was enhanced after irradiation at λ = 447 nm. The cell viability was significantly reduced only in the case of 5. The different behavior in the absence or presence of light makes complex 5 a potential prodrug of interest in PDT. Molecular docking studies followed by molecular dynamics simulations for 1 and the counterpart without the carboxyl group confirmed the experimental data that pointed to an intercalation mechanism. The cytotoxicity of 1 and the potential of 5 in PDT make them good candidates for subsequent conjugation, through the carboxyl group, to "selected peptides" which could facilitate the selective vectorization of the complex toward receptors that are overexpressed in neoplastic cell lines.

New coordination polymers have been obtained by the self-assembly of silver salts AgX (X = BF 4, PF 6, CF 3SO 3) and 2,4-diamino-6-R-1,3,5-triazines L (R = phenyl and p-tolyl) of formulas AgLX ( 1- 6). A complex of different stoichiometry, [Ag 3L 2(H 2O)(acetone) 2](BF 4) 3, 7 (R = phenyl), has also been synthesized. The three-dimensional structures of five compounds have been determined by X-ray diffraction studies. For the AgLX complexes, when X = BF 4 and R = phenyl or p-tolyl, chiral chains with alternating Ag and L are formed. The chains are cross-linked by the counteranions in a three-dimensional fashion through hydrogen bonds and weak Ag...F interactions giving rise to a structure with solvent-filled channels. Different and more compact structures have been found when the counteranion is CF 3SO 3 (OTf). When R = phenyl, sheets are formed which consist of [Ag 2(OTf) 2L 2] units with double triflate bridges and which contain columns of pi-pi stacked arenes. Hydrogen bonds connect the sheets. When AgOTf is used and R is p-tolyl, a different and unusual ladderlike structure is obtained in which the rungs are double asymmetric bridges consisting of the triflate groups bonded to Ag in kappa (2) O,mu 2- O and kappa (1) O,mu 2- O fashion. The ladders are parallel to each other and are mutually linked by N-H...N hydrogen bonds to give a 3D architecture. A very similar ladderlike structure has been found for 7 but with a water molecule and a BF 4 (-) group acting as bridges. The role played by the hydrogen bonds in complex 6 to form the 3-D structure is played in 7 by [Ag(acetone) 2] fragments. The noncovalent interactions play an important role in the different solid-state 3D structures. The behavior of the new derivatives in solution has also been analyzed. A new species has been detected at low temperatures, and this exhibits restricted rotation of the phenyl ring.

The synthesis of several silver double helices containing bis(3,5dimethylpyrazolyl)-6-(R)-s-triazine ligands is described. The structure of two of them has been determined by X-ray difraction. Both derivatives represent the first reported examples of a new interaction mode for a triazine ring that involves a triazine N atom bridging two metal centers. Argentophilic contacts are also present. The Ag-N and Ag-Ag interactions have been demonstrated by theoretical studies, which also showed the clear influence of weak interactions with the counteranion and the effect of the symmetry of the triazine substituent. The different donor characters of these substituents allows a modulation of the strength of the bridging Ag-N(triazine) interaction. Double pi-pi stacking, anion-pi interactions, hydrogen bonds, and hydrophobic effects are observed in an unusual highly symmetrical interpenetrated three-dimensional superstructure.

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Several complexes with a [2 × 2] grid structure have been obtained by the self-assembly of different copper(I) salts and ligands of the type 4,6-bis(pyrazol-1-yl)pyrimidine containing different substituents on the heterocycles. The main goal has been to evaluate the influence over the solid state and solution behavior of the functionalization of the pyrimidine ring with a primary amino substituent. The molecular and crystalline structures of some derivatives have been determined by X-ray diffraction. The grids contain two open voids formed by pairs of ligands facing one another on opposite sides of the grid in a somewhat divergent manner. One counteranion is hosted in each void interacting through hydrogen bonds and anion-π interactions. The presence of the amino group that points toward the inside of the cavity dominates the interactions in the void and apparently determines the orientation of the hosted counteranion and that of the ligands. With the exception of the derivative with chloride as the anion, the grid structure is preserved in solution (NMR and UV-vis) and some cation-anion interaction, increased by the presence of the amino group, exists also in solution (DOSY experiments). The experiments of anion interchange performed in solution indicate that a higher stability is found for the host-guest aggregates with OTs(-) (p-Me-C(6)H(4)SO(3)) and NO(3)(-). While for these anions a 1:2 stoichiometry is reached, for the rest of the anions tested (ReO(4)(-), OTf(-), and PF(6)(-)), only weaker 1:1 complexes are formed. Computational studies support the presence of anion-π interactions.