Tuning the anticancer properties of Pt(ii) complexes via structurally flexible N-(2-picolyl)salicylimine ligands.

Three tridentate Schiff base ligands were synthesized from the reactions between 2-picolylamine and salicylaldehyde derivatives (3-ethoxy (OEt), 4-diethylamino (NEt2) and 4-hydroxy (OH)). Complexes with the general formula Pt(N^N^O)Cl were obtained from reactions between the ligands and K2PtCl4. The ligands and their complexes were characterized by NMR spectroscopy, mass spectrometry and elemental analysis. Further confirmation of the structure of Pt-OEt was achieved by single-crystal X-ray diffraction. The DMSO/chlorido exchange process at Pt-OEt was investigated by monitoring the change in conductivity, revealing very slow dissociation in DMSO. Moreover, solvent/chlorido exchange for Pt-OEt and Pt-NEt2 were investigated by NMR spectroscopy in DMSO and DMSO/D2O; Pt-NEt2 forms an adduct with DMSO while Pt-OEt forms adducts with DMSO and water. The DNA-binding behaviour of the platinum(ii) complexes was investigated by two techniques. Pt-NEt2 has the best apparent binding constant. The intercalation mode of interaction with ct-DNA was suggested by molecular docking studies and the increase in the relative viscosity of ct-DNA with increasing concentrations of the platinum(ii) complexes. However, the gradual decrease in the relative viscosity over time at constant concentration of platinum(ii) complexes indicated a shift from intercalation to a covalent binding mode. Anticancer activities of the ligands and their platinum(ii) complexes were examined against two cell lines. The platinum(ii) complexes exhibit superior cytotoxicity to that of their ligands. Among the platinum(ii) complexes, Pt-OEt possesses the best IC50 against both cell lines, its cytotoxicity being comparable to that observed for cisplatin. Cell cycle arrest in the HepG2 cell line upon treatment with Pt-OEt and Pt-NEt2 was investigated and compared to that of cisplatin; the change in the cell accumulation patterns supports the presumption of an apoptotic cell death pathway. The optimized structures of the B-DNA trimer adducts with the platinum complexes showed hydrogen-bonding interactions between the ligands and nucleobases, affecting the inter-strand hydrogen bonding within the DNA, and highlighting the strong ability of the complexes to induce conformational changes in the DNA, leading to the activation of apoptotic cell death. In summary, the current study demonstrates promising new anticancer platinum(ii) complexes with highly flexible tridentate ligands; the functional groups on the ligands are important in tuning their DNA binding/anticancer properties.

Synthesis and Characterization of Bipyridine-Based Polyaminal Network for CO2 Capture.

The response to the high demand for decreasing the amount of CO2 in the atmosphere, a new polyaminal-based polymer network was designed and successfully prepared through one-pot polycondensation reaction of melamine and [2,2'-Bipyridine]-5,5'-dicarbaldehyde. The formation of the polymer structure was confirmed by FT-IR, solid-state 13C NMR, and powder-X-ray diffraction. The porous properties of the polymeric structure were confirmed by field-emission scanning electron microscope and N2 adsorption-desorption methods at 77 K. The prepared polymer can take up 1.02 mmol/g and 0.71 mmol/g CO2 at 273 K and 298 K, respectively, despite its relatively modest Brunauer-Emmett-Teller (BET) surface area (160.7 m2/g), due to the existence of superabundant polar groups on the pore surfaces.

Benzoins and cyclobenzoins in supramolecular and polymer chemistry.

Benzoin condensation is one of the oldest rigorously described organic reactions, having been discovered in 1832 by Liebig and Wöhler. It creates a new C-C bond and a stereocenter from ubiquitous aldehyde starting materials under simple cyanide-catalyzed conditions. We have recently discovered cyclobenzoins: a class of macrocyclic compounds prepared by a benzoin cyclooligomerization of simple aromatic dialdehydes. Cyclobenzoins' internal cavities suggest they should be intriguing solution-phase supramolecular hosts, while their crystallographic packing aligns these cavities into potentially useful pores in the solid state. Well-precedented derivatization chemistry allows rapid functionalization into heteroacenes, which are optoelectronic materials and models for graphene defects. This Feature Article summarizes our work on cyclobenzoins, together with other applications of benzoins in supramolecular chemistry and materials science.

Confinement of Water Pentamers within the Crystals of a Reduced Cyclotribenzoin.

Reduction of cyclotribenzoin with sodium borohydride produces a cone-shaped hexaol. Crystals of this hexaol, obtained from wet tetrahydrofuran, encapsulate clusters of five water molecules in an idealized hydrogen-bonded arrangement. The water pentamer is stabilized by hydrogen bonding with the -OH groups of the hexaol, and [O-H⋅⋅⋅π] interactions with the benzene rings of the reduced cyclotribenzoin.

Synthesis and Characterization of Heterobenzenacyclo-octaphanes Derived from Cyclotetrabenzoin.

We describe the modular synthesis and characterization of several substituted N-hetero benzenacyclooctaphanes (BAOs), a new motif for heteroaromatic conjugated macrocycles. The targets were synthesized via condensation of substituted aromatic ortho-diamines with a cyclic octaketone building block in moderate to excellent yields (41-91 %). We evaluated the optical and electronic properties and the solid-state structures of the targets and discuss their properties through comparison with their linear diphenyl N-heteroacene counterparts.