Investigation of Cycloparaphenylenes (CPPs) and their Noncovalent Ring‐in‐Ring and Fullerene‐in‐Ring Complexes by (Matrix‐Assisted) Laser Desorption/Ionization and Density Functional Theory

Abstract

[ n ]Cycloparaphenylenes ([ n ]CPPs) with n =5, 8, 10 and 12 and their noncovalent ring‐in‐ring and [ m ]fullerene‐in‐ring complexes with m =60, 70 and 84 have been studied by direct and matrix‐assisted laser desorption ionization ((MA)LDI) and density‐functional theory (DFT). LDI is introduced as a straightforward approach for the sensitive analysis of CPPs, free from unwanted decomposition and without the need of a matrix. The ring‐in‐ring system of [[10]CPP⊃[5]CPP] +. was studied in positive‐ion MALDI. Fragmentation and DFT indicate that the positive charge is exclusively located on the inner ring, while in [[10]CPP⊃C 60 ] +. it is located solely on the outer nanohoop. Positive‐ion MALDI is introduced as a new sensitive method for analysis of CPP⊃fullerene complexes, enabling the detection of novel complexes [[12]CPP⊃C 60, 70 and 84 ] +. and [[10]CPP⊃C 84 ] +. . Selective binding can be observed when mixing one fullerene with two CPPs or vice versa, reflecting ideal size requirements for efficient complex formation. Geometries, binding and fragmentation energies of CPP⊃fullerene complexes from DFT calculations explain the observed fragmentation behavior.

Redox-switchable host–guest complexes of metallocenes and [8]cycloparaphenylene

“…S9a†), we observed a [M − Cp] + signal (common in metallocenes), as well as [M − H] + and [M − 2H] + signals attributable to laser induced coalescence, as observed in prior CPP complexes. 35,78…”

Synthesis and C60 Binding of Aza[10]CPP and N-Methylaza[10]CPP

“…As such, we were primarily interested in the reduction of the title compounds by means of cyclic voltammetry (THF, nBu4PF6). Although the chemical reduction of [n]CPPs has been achieved before, 24 we were unable to observe the reduction of [10]CPP by cyclic voltammetry, at least within the electrochemical window of the solvent. The same result was observed for Aza [10]CPP, even though we expected a decreased LUMO level based on DFT calculations.…”

“…Moreover, the Aza [10]CPP H + ⊃C 60 exhibits a fragmentation energy of 1.82 eV, indicating a stronger binding energy than [10]CPP +• ⊃C 60 , for which the fragmentation energy was 1.69 eV. 27 The N-Me-Aza [10]CPP + allows for two extreme positions of the methyl group towards the ring, i.e. pointing inwards ("in") or outwards ("out").…”

Bethe Salpeter Equation Spectra for Very Large Systems

“…In the last decade, cycloparaphenylenes (CPPs), also known as carbon nanohoops, have emerged as highly structurally tunable emitters, with rich size-dependent opto-electronic properties and host-guest chemistry. [43] While substantial DFT modeling has been completed on CPP+fullerene complexes, [35,[44][45][46] extraction of optical properties at this level of theory is difficult due to the characteristic charge transfer states in CPPs. Further, it has already been established that the BSE formalism is very accurate in predicting the properties of other fullerene-polymer complexes.…”