Design, Structural Elucidation, Spectroscopic Investigations, and DFT Insights Into a (Thiolato)(4α‐tetrakis( o ‐pivalamidophenyl)(porphinato)) Ferrate(II) Porphyrin Framework

ABSTRACT

A five‐coordinate Fe(II) porphyrin complex, framed as [K(2,2,2‐crypt)][Fe ^II (TpivPP)(SH)] ( I ), where TpivPP denotes the “picket‐fence” porphyrin ligand, and 2,2,2‐crypt denotes the 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane, has been successfully synthesized and structurally characterized. Comprehensive UV–visible and infrared spectroscopic analyses complete the coordination of the thiolate ligand and the preservation of the porphyrinic framework. Single‐crystal x‐ray diffraction revealed a high‐spin Fe(II) center ( S = 2) exhibiting a electronic configuration. The displacement of the metal atom from the mean plane of the porphyrin core (Fe‐P _C = 0.574(6) Å) falls within the expected range for high‐spin five‐coordinate Fe(II) metalloporphyrins. Complementary density functional theory (DFT) studies further elucidated the electronic distribution and provided more profound insight into the structural features and bonding characteristics within the complex. The complexation is strongly exergonic (binding energy ≈ −112 kcal mol ⁻¹ ), driven by dominant coulombic attraction between the fragments, with the SH ⁻ axial ligand being the principal nucleophilic site (MEP _min = −0.074 a.u. A quintet (high‐spin, S = 2) ground state is favored by ≈ 14.4 kJ mol ⁻¹ . The frontier molecular orbital and transition analyses indicate metal‐to‐ligand charge transfer. The solid‐state structure is stabilized by extensive H···H van der Waals interactions, along with directional C─H···S and O···H hydrogen bonds.