Near-Infrared-II Absorbing Doubly N-Confused Dioxo-Heptaphyrins as Robust Photothermal Conversion Agents

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Expanded porphyrinoids are versatile macrocycles with tunable electronic and photophysical properties.
• Developing novel photothermal agents with enhanced stability and specific absorption is crucial for advanced therapeutic applications.

Purpose of the Study:

• To synthesize and characterize a novel meso-aryl-substituted [32]heptaphyrin and its derivatives.
• To investigate the photophysical properties and metal coordination behavior of the synthesized compounds.
• To explore their potential as photothermal agents for cancer therapy.

Main Methods:

• Synthesis of a novel [32]heptaphyrin (1) and its bicyclic derivative (2).
• Oxidation of compound 1 to yield the dioxygenated derivative (1-O2).
• Formation of zinc(II) and copper(II) complexes (Zn1-O2 and Cu1-O2).
• Characterization using 1H NMR and femtosecond transient absorption spectroscopy.
• Evaluation of photothermal conversion properties and photostability.

Main Results:

• Successful synthesis of a novel [32]heptaphyrin with confused pyrrole units and its hybrid bicyclic derivative.
• The dioxygenated derivative (1-O2) exhibited site-selective metal coordination.
• The resulting metal complexes (Zn1-O2 and Cu1-O2) displayed strong near-infrared absorption and efficient photothermal conversion.
• High photostability of the metal complexes was observed.
• Ultrafast excited-state decay confirmed weak aromatic character.

Conclusions:

• The study presents a novel class of expanded porphyrinoids with potential as photothermal agents.
• The synthesized dioxo-heptaphyrin metal complexes demonstrate promising characteristics for cancer phototherapy.
• Findings offer insights into molecular design for flexible expanded porphyrinoids in photothermal applications.