title: Quantum chemical DFT study of the interaction between molecular oxygen and FeN₄ complexes, and effect of the macrocyclic ligand.
abstract: Density functional theory (DFT) was used to examine the interaction between molecular oxygen (O₂) and macrocyclic iron complexes of the type FeN₄ during the formation of FeN₄--O₂ adducts. In order to understand how this interaction is affected by different macrocyclic ligands, O₂ was bonded to iron-tetraaza[14]annulene (FeTAA), iron-tetramethyl-tetraaza[14]annulene (FeTMTAA), iron-hexamethyl-tetraaza[14]annulene (FeHMTAA), iron dibenzotetraaza[14]annulene (FeDBTAA), and two iron-tetramethyl-dibenzotetraaza[14]annulene complexes (FeTMDBTAA1, FeTMDBTAA2). The ground state for FeN₄-O₂ adducts was the open-shell singlet. Analysis of the factors influencing the O₂ bonding process showed that different macrocyclic ligands yielded adducts with differences in O--O and Fe--O₂ bond lengths, total charge over the O₂ fragment, O--O vibrational frequency, and spin density in the O₂ fragment. A smaller energy gap between the α-HOMO of the FeN₄ complexes and the β-LUMO of O₂ increased the interaction between the complex and the O₂ molecule. The order of activity was FeDBTAA < FeTMDBTAA2 < FeTMDBTAA1 < FeTAA < FeTMTAA < FeHMTAA.
authors.affiliation: Universidade Federal da Paraíba, 58051-900, João Pessoa, PB, Brazil.
authors.forename: Adilson Luís Pereira
authors.initials: AL
authors.lastname: Silva
authors.forename: Luciano Farias
authors.initials: LF
authors.lastname: de Almeida
authors.forename: Aldaléa Lopes Brandes
authors.initials: AL
authors.lastname: Marques
authors.forename: Hawbertt Rocha
authors.initials: HR
authors.lastname: Costa
authors.forename: Auro Atsushi
authors.initials: AA
authors.lastname: Tanaka
authors.forename: Albérico Borges Ferreira
authors.initials: AB
authors.lastname: da Silva
authors.forename: Jaldyr
authors.initials: J
authors.lastname: de Jesus Gomes Varela
mesh_terms: D000327:Adsorption; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D047028:Macrocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D008024:Ligands; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D007501:Iron; D010100:Oxygen