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

We investigate the gas-phase chemistry of non-covalent complexes of [10]cycloparaphenylene ([10]CPP) with C-60 and C-70 by means of atmospheric pressure photoionization and electrospray ionization mass spectrometry. The literature-known [1 : 1] complexes, namely [10]CPP superset of C-60 and [10]CPP superset of C-70, are observed as radical cations and anions. Their stability and charge distribution are studied using energy-resolved collision-induced dissociation (ER-CID). These measurements reveal that complexes with a C-70 core exhibit a greater stability and, on the other hand, that the radical cations are more stable than the respective radical anions. Regarding the charge distribution, in anionic complexes charges are exclusively located on C-60 or C-70, while the charges reside on [10]CPP in the case of cationic complexes. [2 : 1] complexes of the ([10]CPP2 superset of C-60/70)(+center dot/-center dot) type are observed for the first time as isolated solitary gas-phase species. Here, C-60-based [2 : 1] complexes are less stable than the respective C-70 analogues. By virtue of the high stability of cationic [1 : 1] complexes, [2 : 1] complexes show a strongly reduced stability of the radical cations. DFT analyses of the minimum geometries as well as molecular dynamics calculations support the experimental data. Furthermore, our novel gas-phase [2 : 1] complexes are also found in 1,2-dichlorobenzene. Insights into the thermodynamic parameters of the binding process as well as the species distribution are derived from isothermal titration calorimetry (ITC) measurements.

Automated summary

We studied the gas-phase chemistry of [10]cycloparaphenylene ([10]CPP) non-covalent complexes with C-60 and C-70 using atmospheric pressure photoionization and electrospray ionization mass spectrometry. The stability and charge distribution of these complexes were analyzed using energy-resolved collision-induced dissociation (ER-CID). It was found that complexes with a C-70 core exhibited greater stability, and the radical cations were more stable than the radical anions. [2:1] complexes of the ([10]CPP2 superset of C-60/70)(+center dot/-center dot) type were observed as isolated solitary gas-phase species for the first time. The stability of these complexes was reduced compared to the [1:1] complexes.