Study On The Regio-and Stereoselective Synthesis Of Fullerene Derivatives

Fullerene derivatives have been proposed as a molecular qudit for quantum information processing due to their unique structure and sufficiently long spin relaxation time.Moreover,the scalability issue challenging other proposed quantum materials,such as crystal defects,can be potentially dealt with by the chemical functionalization of fullerene.However,the regioselectivity of multiple additions is challenging in fullerene chemistry and the quantum entanglement based on fullerene molecular qubit is still limited by its stereoisomer.In this work,we study the regio-and stereoselective synthesis of fullerene derivatives to pave the way towards quantum devices based on fullerene.Firstly,we report that hexaadduct of fullerene shows high regioselectivity because of the stereo-hindrance effect.Regioselective formations of[60]fullerene derivatives with octahedral addition patterns are described.We synthesized the hexaadduct T_h-C₆₆（COOEt）₁₂,by nucleophilic cyclopropanation with diethyl bromomalonate in the presence of 1,8-Diazabicyclo[5.4.0]undec-7-ene（DBU）as the base.Moreover,the spectroscopic properties of T_h-C₆₆（COOEt）₁₂ are quite different from the[60]fullerene.It is stable under the 532 nm laser due to the diminished conjugated structure of the carbon cage.It could be used as magnetic dilution material of gain medium in the maser.Unexpectedly,another hexaadduct fullerene derivative which is assumed to be D₃-C₆₆（COOEt）₁₂ has been synthesized.The transition and relaxation properties of its photoexcited triplet are similar to the[60]fullerene.Secondly,using the method of spin compatible Bingel reaction for endohedral nitrogen fullerene with DBU and 2-Bromo-1,3-indanedione,two stereoselective N@C_60,70 derivatives with rigid addends were designed and synthesized,including a mono-functionalized derivative IND-N@C₆₀ and a bis-functionalized derivative Bis-IND-N@C₇₀.The rigidity of spiro addends plays a key role in stereoselectivity.Their spin centers and relaxation properties were retained by well-controlled Bingel reactions,as confirmed by the electron spin paramagnetic resonance（EPR）measurements.They can exhibit zero-field splitting（ZFS）effects in the solid-state due to the anisotropy properties caused by the distortion on the fullerene cage.By embedding the IND-N@₆₀ which has good rigidity in liquid crystals is expected to obtain a remarkable ordering result.We managed to perform nutation experiments in the main peak and the ZFS region of IND-N@C₆₀respectively.As a result,the different Rabi oscillations can be detected which proved that separate addressing of the multiple transitions in a frequency domain is possible.And the multilevel Rabi oscillations are also successfully conducted proving the transitions between the 4 electron spin levels are coherently manipulated.In summary,this work explores the chemical functionalization of the fullerene-based qudit,especially providing a basis for the research on quantum phase gate operation,the coherent manipulation of the multilevel electron spin,and so on.