Stability of Odd‐ Versus Even‐Electron Gas‐Phase (Quasi)Molecular Ions Derived from Pyridine‐Substituted N‐Heterotriangulenes

Abstract

Electrospray ionisation of N-heterotriangulenes (i.e., dimethylmethylene-bridged triphenylamines) with up to three pyridyl groups at their periphery, produces the true radical cation ([M]⁺•) and the protonated molecule ([M+H]⁺) simultaneously. These ions are studied as model systems to illustrate the stability alternation of odd- versus even-electron ions in energy-dependent collision-induced dissociation (CID) experiments. All ions show the same fragmentation pattern, the consecutive loss of three methyl radicals (•CH₃) from the dimethylmethylene bridges of the central triangulene core. [M]⁺• ions dissociate at much lower collision energies than their [M+H]⁺ counterparts. The radical cation forms a singlet fragment with an extended aromatic system that is energetically favoured. Ab initio and density functional theory calculations support this interpretation and allow the assignment of the electronic structure of the fragment ions. Consecutive collision-induced dissociations provide a better match with theory when studied with an ion trap, rather than a linear quadrupole. This is attributed to the resonant nature of the excitation of intermediate ions

Dithiafulvenyl‐Extended N‐Heterotriangulenes and Their Interaction with C60: Cooperative Fluorescence

“…The formation of radical cations in ESI is rare, but not unprecedented and may occur with analytes that are likely to undergo redox reactions (oxidation in the present case) within the ESI source which effectively operates as an electrochemical cell . Electrospray oxidation to yield the corresponding radical cations has been observed for both substituted N ‐heterotriangulenes and TTF‐based molecules . The radical cation of C 60 is neither formed directly in this ESI experiment, nor during fragmentation of the adduct, indicating that the charge within the [ 1 +C 60 ] +.…”

“…To further characterize the 1:1 complexes of C 60 with 1 (Figure ) and 2 (Figure S14), the relative binding strengths within these complexes were evaluated by electrospray ionization mass spectrometry (ESI MS) studies and gas‐phase DFT calculations. A detailed fragmentation study covering related pyridine‐substituted N ‐heterotriangulenes has been recently published elsewhere . Figure displays the positive‐ion collision‐induced dissociation (CID, MS 2 ) mass spectrum of the non‐covalent adduct [ 1 +C 60 ] +.…”

“…To further characterize the 1:1c omplexes of C 60 with 1 ( Figure 6) and 2 ( Figure S14), the relative binding strengths within thesec omplexes were evaluated by electrospray ionization mass spectrometry (ESI MS) studies and gas-phase DFT calculations.Adetailed fragmentation study covering related pyridine-substituted N-heterotriangulenes has been recently published elsewhere. [65] Figure 6d isplays the positive-ion collisioninduced dissociation (CID, MS 2 )m ass spectrum of the non-co-valent adduct [1 + C 60 ] + C,w hose identity was confirmed by the excellent matcho fm easured and simulated isotope patterns. The adduct fragments into the radical cation [1] + C and neutral C 60 .T he formation of radicalc ations in ESI is rare, but not unprecedented and mayo ccur with analytes that are likely to undergo redox reactions (oxidation in the present case) within the ESI source which effectively operates as an electrochemical cell.…”

“…The adduct fragments into the radical cation [1] + C and neutral C 60 .T he formation of radicalc ations in ESI is rare, but not unprecedented and mayo ccur with analytes that are likely to undergo redox reactions (oxidation in the present case) within the ESI source which effectively operates as an electrochemical cell. [66] Electrosprayoxidation to yield the corresponding radical cations hasb een observed for both substituted N-heterotriangulenes [65] and TTF-based molecules. [67] The radical cation of C 60 is neither formed directly in this ESI experiment, nor during fragmentation of the adduct, indicating that the chargew ithin the [1 + C 60 ] + C adduct is exclusively located on 1.I ndeed, the chargeo nC 60 is À0.08 e in [1 + C 60 ] + C and À0.11 e in [2 + C 60 ] + C according to the naturalp opulation analysis( NPA) [68] at B3LYP-D3(BJ)/def2-TZVP.C onsequently,t he complexes observed in the gas phase can be described as [1 + C + C 60 ]a nd [2 + C + C 60 ].…”

Screening Nanographene‐Mediated Inter(Porphyrin) Communication to Optimize Inter(Porphyrin–Fullerene) Forces

“…To estimate the binding strength of the cavity by two porphyrins in ortho-position, energy dependent CID experiments were conducted with free-base porphyrin 2o (2oH 2 ). [5,12,[56][57][58] A solution containing 2oH 2 and C 60 was investigated by ESI-MS. The mass spectrum reveals the presence of the doubly protonated 2oH 2 and the corresponding doubly protonated C 60 @2oH 2 .…”