Tailoring Spin-Spin Dipolar Interactions by Conformational Locking Toward Room-Temperature Molecular Qubits

Area of Science:

• Organic Chemistry
• Quantum Materials Science
• Spin Chemistry

Background:

• Chichibabin's hydrocarbons (CHs) exist in equilibrium between closed-shell quinoidal and open-shell diradical forms.
• Molecular flexibility allows facile rotation, influencing their electronic and spin properties.

Purpose of the Study:

• To design and synthesize conformationally rigidified CHs.
• To systematically control and enhance the open-shell character of CHs.
• To investigate the impact of rigidity on spin-spin interactions and coherence.

Main Methods:

• Synthesis of rigidified CHs using chiral binaphthalene frameworks.
• Electronic spectroscopy to monitor electronic structure changes.
• Pulsed electron paramagnetic resonance (EPR) to probe diradical character and spin dynamics.
• Analysis of zero-field splitting parameters to quantify spin-spin interactions.

Main Results:

• Rigidified CHs showed enhanced open-shell character correlated with increased dihedral angles.
• EPR studies confirmed precise engineering of spin-spin dipolar interactions.
• CH(2) demonstrated remarkable ambient stability and spin coherence.
• Exceptional spin-lattice relaxation (T1 = 1207 ns) and spin dephasing (Tm = 205 ns) times were measured at room temperature.

Conclusions:

• Conformational locking is an effective strategy to control electronic coupling in diradical systems.
• This approach provides a molecular design paradigm for tuning spin functionalities in organic molecules.
• The findings offer critical insights for the development of next-generation quantum materials.