title: Density functional theory study of interactions between carbon monoxide and iron tetraaza macrocyclic complexes, FeTXTAA (X = -Cl, -OH, -OCH3, -NH2, and -NO2).
abstract: This work describes a DFT level theoretical quantum study using the B3LYP functional with the Lanl2TZ(f)/6-31G* basis set to calculate parameters including the bond distances and angles, electronic configurations, interaction energies, and vibrational frequencies of FeTClTAA (iron-tetrachloro-tetraaza[14]annulene), FeTOHTAA (iron-tetrahydroxy-tetraaza[14]annulene), FeTOCH3TAA (iron- tetramethoxy-tetraaza[14]annulene), FeTNH2TAA (iron-tetraamino-tetraaza[14]annulene), and FeTNO2TAA (iron-tetranitro-tetraaza[14]annulene) complexes, as well as their different spin multiplicities. The calculations showed that the complexes were most stable in the triplet spin state (S = 1), while, after interaction with carbon monoxide, the singlet state was most stable. The reactivity of the complexes was evaluated using HOMO-LUMO gap calculations. Parameter correlations were performed in order to identify the best complex for back bonding (3dxzFe → 2pxC and 3dyzFe → 2pzC) with carbon monoxide, and the degree of back bonding increased in the order: FeTNO2TAA < FeTClTAA < FeTOHTAA < FeTOCH3TAA < FeTNH2TAA.
authors.affiliation: Universidade Federal do Maranhão, 65080-805, São Luís, MA, Brazil.
authors.forename: Isaias
authors.initials: I
authors.lastname: de Matos Mourão Neto
authors.affiliation: Universidade Estadual do Maranhão, 65080-040, CP 09, São Luís, MA, Brazil.
authors.forename: Adilson Luís Pereira
authors.initials: AL
authors.lastname: Silva
authors.affiliation: Universidade Federal do Maranhão, 65080-805, São Luís, MA, Brazil.
authors.forename: Auro Atsushi
authors.initials: AA
authors.lastname: Tanaka
authors.affiliation: Universidade Federal do Maranhão, 65080-805, São Luís, MA, Brazil. jaldyr.varela@ufma.br.
authors.forename: Jaldyr
authors.initials: J
authors.lastname: de Jesus Gomes Varela
keywords: Back bonding; Carbon monoxide; Density functional theory; Iron complexes