Phenyl-Substituted Cibalackrot Derivatives: Synthesis, Structure, and Solution Photophysics

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Singlet fission (SF) is a promising mechanism for enhancing solar energy conversion efficiency.
• Cibalackrot dyes are explored for their potential in molecular electronics.
• Controlling solid-state packing is crucial for optimizing photophysical processes in organic materials.

Purpose of the Study:

• Synthesize novel cibalackrot derivatives for molecular electronics and SF applications.
• Investigate the photophysical properties and conformational behavior of these dyes.
• Understand the influence of solid-state crystal packing on SF efficiency.

Main Methods:

• Chemical synthesis of symmetrically and unsymmetrically substituted cibalackrot dyes.
• Solution-based photophysical measurements (excitation energies, fluorescence yields, lifetimes).
• Computational analysis of conformational properties and crystal structure determination via single-crystal X-ray diffraction (XRD).
• SIMPLE method calculations for predicting SF candidates in solid state.
• Preparation of deuteriated analogs for mechanistic studies.

Main Results:

• Synthesized six cibalackrot derivatives with potential for SF.
• Solution measurements indicated favorable molecular properties for SF.
• Crystal structures revealed packing arrangements similar to known polymorphs where SF is outcompeted by charge-separated states and excimer formation.
• Computational methods identified potential solid-state SF candidates but highlighted difficulties in controlling crystal packing.

Conclusions:

• While molecular properties are promising for singlet fission, solid-state crystal packing in cibalackrot derivatives impedes efficient SF.
• Further research is needed to control crystal packing for effective solar energy applications.
• Deuteriated analogs were prepared to aid in understanding intersystem crossing mechanisms.