Pyrazole and Indazole Semihemiporphyrazine Complexes of Rhenium Tricarbonyl: A Structure/Properties Study

The semihemiporphyrazines are a class of ligands comprised of a heterocycle ring and an isoindoline unit linked through a bridging nitrogen atom. These bidentate ligands can be altered in the exocyclic heteroatom position on the isoindoline and in the identity of the heterocycle. Herein, we present a series of Re(CO)₃X (X=Cl, Br, py) complexes of indazole and pyrazole-based semihemiporphyrazines. Changing the ligand and the axial position at the metal alters the character of the complexes, including the structure, tautomerization and charge of the chelate. Modifications to the semihemiporphyrazine also alter the electronic structure of the resultant Re(CO)₃ complexed as demonstrated in their UV-visible spectra. In addition to full characterization, we carried out density functional theory (DFT) and time-dependent density functional theory (TDDFT) to interrogate the electronic structures of these compounds.