Synthesis and Characterizations of Novel Pentacoordinate Iron(II) Porphyrin: Insights from X-ray Crystallography, Interactions Mechanisms, DFT Modeling, QTAIM Analysis and Molecular Docking Investigations

Abstract

<title>Abstract</title> The reaction of four-coordinate picket fence iron(II) porphyrin complex [Fe ^II (TpivPP)] with cryptand-222 solubilized C ₅ H ₁₀ NNaS ₂ in organic solvents, yelds the five-coordinate porphyrin species [Fe ^II (TpivPP)(SH)] ⁻ . The five-coordinate, high-spin (S = 2) (hydrogensulfido)(α,α,α,α-tetrakis( <italic>o</italic> -pivalamidophenyl)porphinato)iron(II) “picket fence” porphyrin derivative [Na(2,2,2-crypt)][Fe ^II (TpivPP)(SH)] ( <bold>I</bold> ) has been synthesized and characterized by UV-vis and IR spectroscopies as well as single-crystal structure determinations. The average equatorial iron-pyrrole nitrogens [Fe-N _p = 2.106(4) Å] bond length and the distance between the iron and the 24-atom core of the porphyrin ring [Fe-P _C = 0.610(2) Å] are longer than those of all other similar five-coordinate iron(II) high-spin porphyrinates. The iron atom is pentacoordinated by the four nitrogen atoms of the pyrrole rings and the sulfur atom of the SH ⁻ group. The Fe-S(SH) bond length is 2.3225(17) Å. This compound crystallizes in the orthorhombic system with the space group <italic>Pbca</italic> . A computational modelling study has been conducted utilizing density functional theory (DFT), Hirshfled surface (HS), HOMO/LUMO analyses, and QTAIM-NCI-RDG iso-surfaces were employed to elucidate the mechanisms of interactions, chemical reactivity properties, and the nature and types of forces contributing to the stability of the complex. Molecular docking analyses have been employed to investigate the potential antibacterial of our material, demonstrating its efficacy against Escherichia coli.