title: Theoretical spectroscopic studies and identification of metal-citrate (Cd and Pb) complexes by ESI-MS in aqueous solution.
abstract: The combined use of ESI-MS, FTIR-ATR and theoretical calculations for the determination of metal-citrate (metal=Cd and Pb) structures are reported. Mass spectrometry allowed to determine the stoichiometry 1:1 and 2:1 of the complexes, corroborating the theoretical calculations. The species found in the ratio 2:1 had their molecular structures readjusted, since the deprotonation of citric acid differed from what was simulated. The calculations of thermodynamic stability (ΔH(0)(aq.)) for the complexes obtained by B3LYP/LANL2DZ were more exoenergetic than those found by PM6. However, for both methods, the stability of the complexes follows a trend, that is, the lowest-energy isomers in PM6 are also the most stable in B3LYP/LANL2DZ. The infrared analysis suggested that carboxyl groups are complexation sites and hydrogen bonds can help in the stability of the complexes. The vibrational frequencies in B3LYP/LANL2DZ had a good correlation with the experimental infrared results.
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000 Lavras, MG, Brazil. Electronic address: bertolialexandre@yahoo.com.br.
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Bertoli
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000 Lavras, MG, Brazil.
authors.forename: Ruy
authors.initials: R
authors.lastname: Carvalho
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000 Lavras, MG, Brazil.
authors.forename: Matheus P
authors.initials: MP
authors.lastname: Freitas
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000 Lavras, MG, Brazil.
authors.forename: Teodorico C
authors.initials: TC
authors.lastname: Ramalho
authors.affiliation: Departamento de Química, Universidade Federal de Lavras, Caixa Postal 3037, 37200-000 Lavras, MG, Brazil.
authors.forename: Daiana T
authors.initials: DT
authors.lastname: Mancini
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Oliveira
authors.affiliation: Departamento de Química Ambiental, Instituto Superior de Agronomia, Universidade de Lisboa, 1399-017 Lisbon, Portugal.
authors.forename: Amarílis
authors.initials: A
authors.lastname: de Varennes
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Dias
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000737:chemistry*; D008962:Models, Theoretical; D008968:Molecular Conformation; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics; D014732:Vibration
chemical_list: D005740:Gases; D012996:Solutions; D002104:Cadmium; D019343:Citric Acid; D007854:Lead
keywords: Cd/Pb complexes; DFT; ESI-MS; FTIR-ATR; PM6