Controlling Interchromophore Coupling in Diamantane-Linked Pentacene Dimers To Create a "Binary" Pair.

Area of Science:

• Organic Chemistry
• Photochemistry
• Materials Science

Background:

• Pentacene dimers are investigated for their potential in photophysical applications.
• Understanding interchromophore electronic coupling is crucial for controlling photophysical processes.
• Quantum mechanical calculations predict spacer substitution influences coupling in pentacene dimers.

Purpose of the Study:

• To synthesize pentacene dimers with diamantane spacers to experimentally verify theoretical predictions.
• To investigate the role of the diamantane spacer's substitution pattern in controlling electronic coupling between pentacene units.
• To utilize intramolecular singlet fission (i-SF) as a probe for electronic coupling strength.

Main Methods:

• Synthesis of two isomeric pentacene dimers linked by diamantane spacers.
• Characterization of intramolecular singlet fission (i-SF) using transient absorption spectroscopy.
• Analysis of the impact of 4,9- and 1,6-diamantane substitution on interpentacene coupling.

Main Results:

• The 4,9-dimer showed no electronic coupling, with photoexcitation deactivating similarly to monomeric pentacene.
• The 1,6-dimer exhibited strong coupling, driving i-SF with high correlated triplet yields (close to unity) and significant free triplet yields (ca. 50%).
• Diamantane substitution pattern provides binary control ('on'/'off') over interpentacene electronic coupling, unlike other spacers.

Conclusions:

• The substitution pattern on the diamantane spacer is decisive in controlling electronic coupling between pentacene chromophores.
• Diamantane spacers offer a unique binary switching mechanism for interchromophore interactions.
• This study provides experimental validation for theoretical predictions on molecular spacer design in pentacene systems.