3,6-Carbazoylene Octaphyrin (1.0.0.0.1.0.0.0) and Its Bis-BF₂ Complex

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Expanded porphyrins are a class of macrocyclic compounds with tunable electronic and optical properties.
• Carbazole derivatives offer a versatile platform for constructing complex organic molecules.
• Modulating the electronic structure of macrocycles is key to developing advanced functional materials.

Purpose of the Study:

• To synthesize novel octaphyrin macrocycles incorporating carbazole units.
• To investigate the effects of trifluoroacetate (TFA) protonation and BF2 complexation on the conformation and electronic structure.
• To evaluate the photophysical properties and potential applications of these modified macrocycles, particularly as laser dyes.

Main Methods:

• Synthesis of octaphyrin precursors based on 3,6-carbazole units.
• Protonation using trifluoroacetic acid (TFA) to form diprotonated species (2-2TFA).
• Complexation with BF2 to form bis-BF2-chelated complexes (2-2BF).

Main Results:

• The diprotonated species (2-2TFA) exhibited strong panchromic absorption extending up to 800 nm.
• The bis-BF2-chelated complex (2-2BF) displayed intense visible absorption (ε535nm = 2.1 × 10^5 M^-1 cm^-1) and red-shifted emission at 640 nm with a large Stokes shift.
• The 2-2BF complex was successfully utilized to construct a high-quality organic microlaser under optical pumping.

Conclusions:

• Modification of octaphyrins through TFA protonation and BF2 complexation effectively modulates their electronic and photophysical properties.
• The resulting macrocyclic complexes show promising characteristics for optoelectronic applications.
• Expanded porphyrins, exemplified by the 2-2BF complex, hold significant potential as efficient laser dyes for organic microlasers.