3d-metal macrocyclic complexes containing porphyrazine/ perfluoroporphyrazine and fluoro ligands: Structural and thermodynamic parameters according to the various DFT model chemistries

Abstract

By using three independent of density functional theory (DFT) model chemistries with functionals B3PW91, M06 and OPBE, and the TZVP basis set, combining the D3 version of Grimme’s dispersion with the original D3 damping function, the molecular structures of three types of 3[Formula: see text] element (M) macrocyclic coordination compounds — homoligand with porphyrazine (H2L1), heteroligand with porphyrazine and two axially oriented fluoro ligands and heteroligand with perfluoroporphyrazine (H2L2) and two axially oriented fluoro ligands having [ML1], [ML1(F)2] and [ML2(F)2] compositions, respectively, were calculated. The values of the most important bond lengths, bond and non-bond angles in the resulting metal complexes, and NBO analysis data are presented. It was noted that almost each of these complexes contains a coplanar MN4 chelate unit and a group of N4 atoms, as well as coplanar 5- and 6-membered rings; moreover, both of them are pairwise identical to each other in terms of the sums of bond angles (540[Formula: see text] and 720[Formula: see text], respectively) and their assortments. Bond angles formed by M atoms and two fluorine atoms are 180[Formula: see text]; bond angles formed by fluorine, M and nitrogen atoms are 90[Formula: see text]. NBO analysis of all the above 3[Formula: see text]-metal chelates was carried out, and based on the data, a high degree of delocalization of the electron density in these coordination compounds was stated. The values of the standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs energy [Formula: see text] of formation of these compounds were also calculated. Particular attention was paid to the fact that according to these data, for the ([ML1]) and ([ML1(F)2]) complexes the values of [Formula: see text] and [Formula: see text] are positive, whereas for ([ML2(F)2]) complexes they are negative, and in the series [ML1] – [ML1(F)2] – [ML2(F)2] there is an increase in the thermodynamic stability of the complexes, which is undoubtedly due to the presence of peripheral fluorine substituents in the [ML2(F)2] structure. There was also good agreement between similar parameters calculated by different DFT methods, both qualitatively and quantitatively.