Synthesis and Structure of a Functionalized [9]Cycloparaphenylene Bearing Three...

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Cycloparaphenylenes (CPPs) are strained macrocycles with unique electronic properties.
• Functionalization of CPPs is crucial for tuning their characteristics for advanced applications.
• Indeno[2,1-a]fluorene-11,12-dione units offer interesting photophysical and electronic properties.

Purpose of the Study:

• To develop a synthetic pathway for a novel functionalized [9]cycloparaphenylene.
• To incorporate three indeno[2,1-a]fluorene-11,12-dione-2,9-diyl units into the macrocyclic ring structure, creating [3]CIFO.
• To investigate the structural, conformational, and photophysical properties of the synthesized molecule.

Main Methods:

• Multi-step organic synthesis to construct the functionalized macrocycle.
• Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C) for structural elucidation and rotamer identification.
• Density Functional Theory (DFT) calculations to determine relative stabilities and rotational barriers of rotamers.
• UV-vis absorption and fluorescence spectroscopy to study photophysical properties.
• Cyclic voltammetry to investigate electrochemical behavior.

Main Results:

• A successful synthetic route to the functionalized [9]cycloparaphenylene, [3]CIFO, was established.
• NMR analysis confirmed the exclusive formation of the anti rotamer of [3]CIFO.
• DFT calculations revealed that the anti rotamer is thermodynamically more stable (4.3 kcal/mol) and possesses a significant rotational barrier (23.3 kcal/mol) compared to the syn rotamer.
• Initial investigations into the UV-vis, fluorescence, and cyclic voltammetry of anti-[3]CIFO were performed.

Conclusions:

• The synthesis of a novel macrocycle, anti-[3]CIFO, incorporating indeno[2,1-a]fluorene-dione units was achieved.
• The exclusive formation and enhanced thermodynamic stability of the anti rotamer were demonstrated.
• The study provides a foundation for exploring the photophysical and electrochemical properties of this new class of functionalized cycloparaphenylenes.