Robust coherent spin centers from stable azafullerene radicals entrapped in cycloparaphenylene rings

Abstract

Stable and abundant spin-1/2 species from azafullerene (C59N˙) supramolecularly hosted in [10]cycloparaphenylene nanohoops are operated as stable qubits, with possibility of qubit wiring via intermediate polymerized spin-redistributed states.

Long Spin Coherence Times on C59N-C60 Heterodimer Radicals Entrapped in Cycloparaphenylene Rings

“…C 59 N • can rotate in structure H with energy barrier lower than 0.2 eV, keeping N beneath the [10]CPP ring, 17 and this may also help the cage rotation at intermediate temperatures. 18 Our calculated energy to fully separate two [10]CPP rings in this system (structure G to H) is 1.39 eV, close to the previous literature value of 1.7 eV. 16 However, [10]CPP in structure H can lower energy by a further 0.46 eV through a 90°rotation of one of the rings, giving the herringbone structure I, more closely resembling the known packing in C 60 ⊂[10]CPP.…”

“…We remeasured the 25% sample over 1 year later and detected both components of the singlet and triplet signal, with roughly comparable signal ratios but with reduced intensity in terms of the number of EPR-active molecules. This reflects what was observed previously for the triplet signal in pure (C 59 N) 2 samples 17,18 and can be directly linked to the presence of [10]CPP, which screens the radicals from external access.…”

“…The most stable structure contains two separated C 60 and a stable dimer (C 59 N) 2 (structure A), consistent with prior experimental and theoretical models for azafullerenes. 10,18,28,29 Breaking the dimer allows creation of the structures presented in structures B−E (their magnetic moments are also summarized in the same table, hereinafter structures B−E, respectively). Structure B represents the case where the two C 59 N rotate by 180°after breaking their shared bond, before the carbon radicals on each cage attack the neighboring C 60 molecules, forming two C 59 N-C 60…”

“…Moreover, the radical protection suppresses its interactions with the nearest environment and thus very long coherence times are measured. Despite the obvious success of such a supramolecular encapsulation approach, the concentration of stable radicals remains low, in the 2–3% range . How to surpass this statistical limit for the encapsulated fullerene radicals remains as an open challenge.…”

Two Rings Around One Ball: Stability and Charge Localization of [1 : 1] and [2 : 1] Complex Ions of [10]CPP and C60/70[*]

“…As hosts for numerous guest molecules such as smaller rings, [35][36][37][38] fullerenes, [38][39][40][41][42][43] fullerene dumbbells, [24,[44][45][46][47] endohedral metallo fullerenes, [36,[48][49][50][51][52] larger PAHs [53][54][55] and organic cations, [56] CPPs represent a tremendously important contribution to the world of noncovalent inclusion complexes. Bonding results from concave/convex π-π, CH-π and/or charge-π interactions between host and guest.…”