Sezione di Chimica Organica

Stereochemistry of Organic Compounds Through CD We determine the absolute configuration, as well as the conformation and the enantiomeric composition of organic moleucles endowed with suitable cromophores or derivatized ad hoc. We follow a variety of possible approaches, ranging from non empirical (ab initio DFT calculations and DeVoe coupled oscillator approach) to qualitative comparisons. We participate in setting up new derivatization protocols to prepare cottonogenic systems. Principal investigators: Lorenzo Di Bari and Gennaro Pescitelli Participants: Piero Salvadori Collaborations: J. -C. Marchon, K. Krohn

Near Infrared Circular Dichroism of Chiral Lanthanide Complexes Chiral Ln3+ complexes find widespread applications in organic catalysis, as MRI contrast agents, in the study of ion transport mechanism, as auxiliaries for organic stereochemical determinations. We characterize their structural and dynamic properties by means of their unique NIR-CD properties and taking advantage of paramagnetic NMR. We have studied conformational rearrangements, chirality inversions and axial ligand exchange. Principal investigator: Lorenzo Di Bari, Piero Salvadori Participants: Chiara Pastore, Moreno Lelli, Silvia Ripoli, Gennaro Pescitelli Collaborations: José M. Saà, H. Tsukube, M. Woods

Protein-small molecules interactions We investigate the interactions between proteins and small organic molecules, mainly by means of induced CD and by NMR. We aim at determining the binding site(s) and affinity and to discover potential interactions between ligands. In particular we focus on two distinct problems, both related to serum albumin as the protein. First, antioxidant molecules and herbal drugs, that are found in the mediterranean diet, as well as in common food supplements. They may interfere with the transport of other drugs, possibly administered for therapy. Second, we are interest in MRI contrast agents, which may take advantage of the binding to a macromolecule. We take advantage of a combination of experimental data from induced CD, saturation transfer difference NMR, and paramagnetic NMR. Principal investigators: Lorenzo Di Bari Participants: Piero Salvadori, Gennaro Pescitelli, Sanghamitra Pradan

Structure and Function of Enantioselective Catalysts We developed new experimental protocols for the investigation of more or less labile species which originate after the mixing of a chiral organic ligand with a metal ion. These systems provide useful catalytic precursors, whose optimization is ensured by fully understanding their structure and dynamic properties. In several cases we experienced that multiple solution equilibria among complexes of different stoichiometries can complicate the picture and may require dedicate experiments. The experimental data span NMR, CD and MS (possibly high resolution) spectra and are complemented by a full computational investigation of the most likely geometries. Principal investigators: Lorenzo Di Bari and Gennaro Pescitelli Participants: Piero Salvadori Collaborations: J. M. Saà

Chiral supramolecular organization in luminescent polymers and dyes Chiral groups appended to rodlike polymers or to dyes, which spontaneously give rise to stacking phenomena, may induce a twist in the supramolecular aggregates, which strongly influences their luminescent properties. We found that this twist is clearly witnessed in the CD spectra and that this is indeed a most sensitive technique to follow aggregation. When the individual molecules feature chiral elements in positions very remote from the chromophores, only weak CD spectra are measured. On the contrary, we observed spectacular CD bands in aggregates. Principal investigator: Lorenzo Di Bari and Gennaro Pescitelli Participants: Piero Salvadori Collaborations: G. M. Farinola, F. Babudri, F. Naso, O.H. Omar