Ricerc@Sapienza

The chance to have persistent organic radicals in combination with metals has attracted much interest since it offers the possibility of having new functional molecules with multiple open-shell elements. In this study, we report the synthesis of two tripodal tris(2-pyridyl)methylamine ligands (TPMA) functionalized with nitronyl nitroxide persistent radicals. The newly formed ligands have been used to coordinate zinc(ii), copper(ii), iron(ii) and cobalt(ii).

Ten new heterodimers were synthesized in different stoichiometry to explore the role exerted by potential proton-transfer reactions in the supramolecular structures of A-B cocrystals formed by 5-haloderivatives of uracil (halogen = F, Cl, Br, I; coformer A) coupled with aminoazines as 2-aminoadenine simulants (melamine, 2,4,6-triaminopyrimidine, 2,6-diaminopyridine; coformer B) for pyrimidine nucleobase recognition.

Seven 5-and 6-halogenated derivatives of uracil or 1-methyluracil (halogen = Cl, Br, I) were
studied by single crystal X-ray diffraction. In contrast with pure 5-halouracils, where the presence
of N-H…O and C-H…O hydrogen bonds prevents the formation of other intermolecular interactions,
the general ability of pyrimidine nucleobases to provide electron donating groups to halogen
bonding was confirmed in three crystals and cocrystals containing uracil with the halogen atom at

6-Mehyluracil, C5H6N2O2, exists in two crystalline phases: form (I), monoclinic,
space group P21/c [Reck et al. (1988). Acta Cryst. A44, 417–421]. and form (II),
monoclinic, space group C2/c [Leonidov et al. (1993). Russ. J. Phys. Chem. 67,
2220–2223]. The structure of polymorph (II) has been redetermined providing a
significant increase in the precision of the derived geometric parameters. In the
crystal, molecules form ribbons approximately running parallel to the c-axis
direction through N—H O hydrogen bonds. The radical differences observed

The catalytic effects of guests 5-7 on the cyclization of 1 and 3 have been measured at 62 °C in MeCN. A record rate acceleration of more than 2000 times has been observed in the cyclization of the tricationic host 3 featuring large diazapyrenium π-surfaces by tetrathiafulvalene guests 6 and 7. The results emphasize the role played by extended π-surfaces in the host and the goodness of a tetrathiafulvalene core in the guest, enhanced by polyethereal side arms.

Tripodal metal complexes have been widely used for catalysis and more recently also for molecular recognition applications. Their ability in recognition and signal amplification of chiral substrates is because of the setup of the ligand around the metal in a propeller shape. Within this subject, we have recently reported tris(2-pyridylmethyl)amine- and triphenolamine-based complexes for the determination of the enantiomeric excess of various substrates.

This review article is concerned with the measurement, significance and applications of the concept of effective molarity (EM) in a large variety of cyclization reactions ranging from the formation of giant macromolecules in polymeric equilibrates to the self-assembly of cyclic supermolecules and supramolecular aggregates.

In this review we cover some aspects of metal-salophen and metal-salen complex chemistry related to their supramolecular attitude. We examined under the lens of the non-covalent interactions their potential to behave as building blocks for auto-assembled architectures, supramolecular receptors and catalysts, although this last point has been only briefly mentioned.

Ion receptors could be used for the extraction of toxic or radioactive cations and anions from water or the recycling of valuable raw materials, providing means for water purification and decontamination. Supramolecular chemistry has been concerned with cation receptors since the seminal work of Pedersen, Lehn, and Cram on crown ethers, cryptands, and spherands, respectively. Since then, cation receptor chemistry represents an important research field, which has also addressed the challenge of developing systems that can efficiently work in water.