title: Influence of the chelator structures on the stability of Re and Tc tricarbonyl complexes with iminodiacetic acid tridentate ligands: a computational study.
abstract: The development of novel radiopharmaceuticals for nuclear medicine based on M(CO)3 (M = Tc, Re) complexes has attracted great attention. The versatility of this core and the easy production of the fac-[M(CO)3(H2O)3](+) precursor could explain this interest. The main characteristics of these tricarbonyl complexes are the high substitution stability of the three CO ligands and the corresponding lability of the coordinated water molecules, yielding, via easy exchange of a variety of bi- and tridentate ligands, complexes xof very high kinetic stability. Here, a computational study of different tricarbonyl complexes of Re(I) and Tc(I) was performed using density functional theory. The solvent effect was simulated using the polarizable continuum model. These structures were used as a starting point to investigate the relative stabilities of tricarbonyl complexes with various tridentate ligands. These complexes included an iminodiacetic acid unit for tridentate coordination to the fac-[M(CO)3](+) moiety (M = Re, Tc), an aromatic ring system bearing a functional group (-NO2, -NH2, and -Cl) as a linking site model, and a tethering moiety (a methylene, ethylene, propylene butylene, or pentylene bridge) between the linking and coordinating sites. The optimized complexes showed geometries comparable to those inferred from X-ray data. In general, the Re complexes were more stable than the corresponding Tc complexes. Furthermore, using NH2 as the functional group, a medium length carbon chain, and ortho substitution increased complex stability. All of the bonds involving the metal center presented a closed shell interaction with dative or covalent character, and the strength of these bonds decreased in the sequence Tc-CO > Tc-O > Tc-N.
authors.affiliation: Instituto Superior de Tecnología y Ciencias Aplicadas, 6163, Avenida Salvador Allende No 1110 entre Infanta y Avenida Rancho Boyeros, Quinta de los Molinos, La Habana, 10600, Cuba.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hernández-Valdés
authors.affiliation: Instituto Superior de Tecnología y Ciencias Aplicadas, 6163, Avenida Salvador Allende No 1110 entre Infanta y Avenida Rancho Boyeros, Quinta de los Molinos, La Habana, 10600, Cuba.
authors.forename: Zalua
authors.initials: Z
authors.lastname: Rodríguez-Riera
authors.affiliation: Facultad de Química, Universidad de La Habana, Zapata esquina G, 10400, La Habana, Cuba.
authors.forename: Alicia
authors.initials: A
authors.lastname: Díaz-García
authors.affiliation: Université de Toulouse, 118, avenue de Rangueil, 31062, Toulouse, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Benoist
authors.affiliation: Instituto Superior de Tecnología y Ciencias Aplicadas, 6163, Avenida Salvador Allende No 1110 entre Infanta y Avenida Rancho Boyeros, Quinta de los Molinos, La Habana, 10600, Cuba. ulises.jauregui@infomed.sld.cu.
authors.forename: Ulises
authors.identifier: http://orcid.org/0000-0002-6943-4873
authors.initials: U
authors.lastname: Jáuregui-Haza
keywords: DFT calculation; Iminodiacetic acid ligands; Radiopharmaceutical design; Re and Tc complexes; Tricarbonyl complexes