Single oxygen generation sensitized by spiro(dipyridinogermole)(dithienogermole)s

Area of Science:

• Organic Chemistry
• Photochemistry
• Materials Science

Background:

• Singlet oxygen (¹O₂) generation is crucial for various applications, including photodynamic therapy and organic synthesis.
• Developing efficient and stable photosensitizers is key to advancing these fields.
• Spiro-heterocyclic compounds offer unique structural and electronic properties for photophysical applications.

Purpose of the Study:

• To synthesize and evaluate novel spiro(dipyridinogermole)(dithienogermole) derivatives as photosensitizers for singlet oxygen generation.
• To compare the performance of these new compounds with established photosensitizers like tetraphenylporphyrin (TPP).
• To investigate the structure-activity relationship influencing singlet oxygen generation efficiency.

Main Methods:

• Synthesis of three spiro(dipyridinogermole)(dithienogermole) derivatives (compounds 1-3).
• Photochemical irradiation of air-saturated solutions of the derivatives in dichloromethane-methanol.
• Quantification of singlet oxygen generation using scavengers like dihydronaphthoquinone (DHN) and diphenylisobenzofuran (DPBF).
• Determination of first-order rate constants and quantum yields (φΔ) for singlet oxygen generation.

Main Results:

• All three synthesized spiro(dipyridinogermole)(dithienogermole) derivatives effectively generated singlet oxygen upon irradiation.
• Spiro(dipyridinogermole)[bis(n-hexylbithiophenyl)dithienogermole] (compound 2) exhibited the highest efficiency.
• Compound 2 demonstrated a higher first-order rate constant than tetraphenylporphyrin (TPP).
• The efficient intersystem crossing of the dipyridinogermole unit contributes to the high performance.
• A quantum yield of φΔ = 0.72 was measured for compound 2, relative to rose bengal (RB).

Conclusions:

• Spiro(dipyridinogermole)(dithienogermole) derivatives are promising photosensitizers for singlet oxygen generation.
• Compound 2 represents a highly efficient photosensitizer, outperforming TPP in terms of singlet oxygen generation rate.
• The structural features, particularly the dipyridinogermole unit, are critical for efficient intersystem crossing and singlet oxygen production.
• These findings open avenues for the development of advanced photosensitizers in various scientific and technological domains.