Weak coordination of H2S to the solid-state ferrous porphyrin complexes with diatomic molecules. Characterization of 6-coordinate adducts at low temperature

Abstract

The interaction of hydrogen sulfide (H2S) with ferrous porphyrin five coordinate complexes bearing CO and O2 (L) was studied at low temperatures in sublimated porphyrin layers using electronic and infrared absorption spectroscopy. Upon addition of H2S to a cryostat containing Fe(II)(TPP)(L) (TPP is meso-tetraphenyl-porphyrinato dianion) at low temperatures, the spectral changes were observed that are consistent with H2S binding in axial position trans to the diatomic ligand. Density functional theory (DFT) computational analysis also supports formation of the six-coordinate adducts. These complexes are stable only at very low temperature and dissociate upon warming. The stretching frequencies of diatomic ligands in the six-coordinate adducts were recorded and compared with those, known for the other thiol and thioether ligands.