Porphyrin(2.1.2.1) rhenium(I) complexes: Synthesis, structures, properties, and dipyrrin act as bipyridyl-like ligand

Abstract

Two new rhenium(I) porphyriniod complexes (H₂PY: 3,3-rhenium(I) tricarbonyl chloride-(3¹E,3²Z,7¹E,7²Z)-4,8-bis(perfluorophenyl)-1¹H,3²H,7²H-5¹λ²,7¹λ⁴-1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane, and H₂PZ: 3,3-rhenium(I) tricarbonyl acetate-(3¹E,3²Z,7¹E,7²Z)-4,8-bis(perfluorophenyl)-1¹H,3²H,7²H-5¹λ²,7¹λ⁴-1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane) containing two different Re(I)−N π-bonding networks were prepared from the saddle-shaped porphyrin(2.1.2.1) bearing pentafluorophenyl substituents at the two meso-positions (H₂Por: 3¹E,3²Z,7¹E,7²Z)-4,8-bis(perfluorophenyl)-1¹H,3²H,5¹H,7²H-1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane). Despite the tetrapyrrolic nature of the porphyrin(2.1.2.1) scaffold, this is the first case of a pyrrole-based macrocycle which acts as a bipyridyl-like complexing ligand in the formation of an octahedral Re(I) complex. X-ray analysis and ¹H NMR studies show that both Re(I) complexes (H₂PY and H₂PZ) consist of one octahedral Re(I) ion π-bonded to a dipyrrin unit and one protonated dipyrrin moiety linked together through o-phenylene bridges. This bonding behavior is compared to related metal complexes of porphyrin(2.1.2.1) macrocycles as well as other Re(I) porphyrins and demonstrates that the distorted conformation and, by virtue, the electronics of H₂Por serve as a novel platform for examining structure property relationships which differ than those of other related planar porphyrin macrocycles.

Graphical Abstract

Keywords:

• Bipyridyl-like ligand
• rhenium(I) complex
• ligand exchange
• porphyrin(2.1.2.1)

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Project Startup Foundation for Distinguished Scholars of Jiangsu University under Grant No. 4111310026 (SLX); Postdoctoral Science Foundation of China under Grant No. 2021M701473(SLX); and Grants-in-Aid for Scientific Research under Grant Nos. JP20H00379 (HY), JP20H05833 (HY), JP20H02711 (NA), and JP19K05626 (DK). The theoretical calculations were carried out at the Centre for High Performance Computing in Jiangsu University.