Pyrogallol[4]arenes as frustrated organic solids.

Two forms of interdigitated layered arrangements of C-pentylpyrogallol[4]arene (PgC5) have been structurally elucidated and show variations in packing arrangements and host-guest interactions. Molecular dynamics simulations reveal a propensity for formation of self-included dimers, with or without incorporated solvent. Combined gas sorption and PXRD results show the presence of seven forms of PgC5, with and without CO2 (and their interconversions). This is the first CO2 gas sorption study of pyrogallol[4]arenes, and it provides evidence that pyrogallol[4]arenes may act as frustrated organic solids.

Inclusion properties of volatile organic compounds in a calixarene-based organic zeolite.

The inclusion properties of a calixarene-based porous material have been studied to investigate the adsorption and the desorption of carbon tetrachloride, chloroform, and water in the zeolite-like structure. Uptake and release processes have been studied both by time-resolved powder X-ray diffraction and by thermogravimetric analysis to obtain structural and kinetic information. The selected guests are able to enter the structure with an increase in the host cell volume and with time-dependent diffusivity coefficients. Chloroform molecules act as a permanent porosity switch promoting a phase transition to non-porous triclinic form.

Acetylene and argon adsorption in a supramolecular organic zeolite.

The adsorption properties of a new nanoporous organic zeolite with respect to acetylene and Ar were studied by volumetric adsorption analysis, microcalorimetric experiments, and synchrotron high-resolution X-ray powder diffraction. This allowed us to locate the guest molecules inside the host channels and characterize the host-guest interactions.

Design and synthesis of spirotryprostatin-inspired diketopiperazine systems from prolyl spirooxoindolethiazolidine derivatives.

Based on the spirotryprostatin-A structure, we designed, synthesized, and evaluated different series of compounds belonging to the diketopiperazine structural class as potential cell cycle modulators and cytotoxic agents. Starting from the spirooxoindolthiazolidine scaffold, amide coupling with Pro derivatives and intramolecular cyclization reactions are suitable synthetic methods to generate chemically diverse diketopiperazine system, such as hexahydropyrrolo[1,2-a][1,3]thiazolo[3,2-d]pyrazine-5,10-dione (structure I), hexahydropyrrolo[1,2-a] [1,3]thiazolo[3,4-d]pyrazine-5,10-dione (structure II) and spiroindol-2-one[3,3']hexahydro-5,10H-pyrrolo[1,2-a][1,3]thiazolo[3,4-d]pyrazine-5,10-dione (structure III). Some of these compounds, especially those who belong to the series I and II, showed interesting cytotoxic activity.

Structural effects of proline substitution and metal binding on hexameric cyclic peptoids.

L-Proline and N-methoxyethyl glycine have been included in novel cyclic hexameric peptoids. Supramolecular coordination with Na(+) triggered the formation of the first 1D metal-organic framework based on peptoids.

Finding crystal structures from few diffraction data by a combination of a random search with genetic algorithms.

A new procedure for performing structural analysis of crystalline materials from diffraction data, using internal coordinates, is described. For starting information only unit-cell content, space group, chemical formula, molecular connectivity and a limited amount of diffraction data are required. After first selecting a number of solutions using a Monte Carlo approach with severe filters, which reject the most unrealistic solutions, genetic algorithms (crossover and mutations) are applied. In fact, the initial selection step alone is, frequently, a powerful tool for discovering structures, without recourse to the genetic algorithms. The procedure, while suffering from the limitation that connectivity must be known, is effective in cases where direct methods are not applicable because the diffraction data are scarce, are limited to low diffraction angles or are missing in specific portions of the reciprocal space. The main features of the algorithm are described and examples of validation given. The routines are now available as part of the freely distributed general-purpose program TRY. The program is available on the Web at http://www.theochem.unisa.it/try.html.