Naslov
Chiral Induction and Hydrogen-Bonded Self-Assembly of Palladium Complexes with Amino Acid Derived Monodentate Phosphine Ligands

Autori
Kokan, Zoran ; Kovačević, Borislav ; Tzvetkova, Pavleta ; Kirin, Srećko I.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
12th International Symposium on Macrocyclic and Supramolecular Chemistry in conjunction with ISACS: Book of Abstracts / - , 2017

Skup
International Symposium on Macrocyclic and Supramolecular Chemistry

Mjesto i datum
Cambridge, Ujedinjeno Kraljevstvo, 02.07.2017. - 06.07.2017

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
palladium complexes, NOESY, computational studies

Sažetak
Palladium complexes have been extensively used for the construction of various self-assembled structures. However, in many cases, the square planar geometry of the palladium atom is coupled with cis-directing bidentate ligands, whereas trans configuration is rarely encountered along with the use of monodentate phosphine ligands. Hydrogen bonding and metal coordination are often combined as orthogonal driving forces for the supramolecular assembly, where complementary interactions are mostly pre-designed rather than emerged from the recognition process. In addition, chiral peptide-palladium systems have not been sufficiently explored in supramolecular assembly, most probably due to the non-specific nature of the amino acid interactions. Recently, we have published our research on supramolecular chirality inversion of small chiral metal-ligand system. The alanylaminopyridine ligand already exhibiting hydrogen-bonded self-assembly in solution can invert its supramolecular chirality upon complexation to zinc ions. Herein, we present an unprecedented dichloropalladium-monodentate phosphine system incorporating different amino acids, which unexpectedly forms non-covalent dimers in chloroform through eight hydrogen bonded amides indicated by NMR and IR measurements. Phosphorous NMR measurements showed different palladium isomers in solution: trans-, cis-, or a mixture thereof, in chloroform, acetonitrile, or methanol, respectively. DOSY measurements confirmed the formation of dimeric species in chloroform. The phenylalanine derivative shows strong exciton-coupled Cotton-effect in chloroform or dichloromethane, in the visible region, assuming two metal centres in close proximity. In 20% acetonitrile/chloroform solution, slow trans-cis isomerisation of the complex is accompanied by the gradual disappearance of Cotton-effect (1 h), indicating the importance of trans-configured palladium for the self-assembly process. The solution structure of the dimeric specie was elucidated by NOESY and computational methods. To the best of our knowledge, monodentate phosphine complexes of trans-dichloropalladium(II) that form discrete hydrogen-bonded dimers in solution have not been reported in the literature.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA