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

Abstract

Within the growing family of strained carbon nanohoops and nanobelts, [10]CPP arguably offers the best compromise between synthetic accessibility and strong binding affinity for C60. In this work, we report the synthesis of two nitrogen-containing analogues of [10]CPP and we systematically compare the structure, optoelectronic properties and C60 binding affinities of this small set of structurally similar macrocycles. While Aza[10]CPP outcompetes the parent compound by approximately one order of magnitude in respect to C60 binding, we found that the reverse was true for the methylaza analogue. Transient absorption studies showed that photo-induced electron transfer occurred readily from [10]CPP and its aza-analogue to an encapsulated C60 guest. Formation of a charge separated complex was not observed however for the N-methylated derivative. These insights will prove useful for further applications of strained nanohoops in supramolecular chemistry and organic electronics.

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

“…For instance, MS 2 experiments provided evidence for a [10]CPP that is firmly interlocked within a [2]rotaxane [46] . Furthermore, we were able to determine the relative bond strength of a CPP‐based porphyrinoid host molecule to C 60 [57] as well as the relative bond strength between the host molecules [10]CPP, aza[10]CPP and methyl‐aza[10]CPP and the C 60 guest [32] …”

“…[16][17][18] To tune their molecular properties, CPPs have been chemically modified. In this context, the substitution of hydrogen by halides [19][20][21][22][23][24][25][26] as well as carbon by nitrogen [27][28][29][30][31][32] have been achieved. Additionally, introduction of electron-donating or withdrawing groups [33] and larger π-frameworks [34] into the ring molecule have been reported.…”

“…[46] Furthermore, we were able to determine the relative bond strength of a CPP-based porphyrinoid host molecule to C 60 [57] as well as the relative bond strength between the host molecules [10]CPP, aza [10]CPP and methyl-aza [10]CPP and the C 60 guest. [32] In this study, CPP�fullerene complexes are investigated by atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) mass spectrometry (MS) in combination with density functional theory (DFT). We are able to observe stable [2 : 1] complexes in which two CPPs encapsulate one fullerene.…”

Tunable Macrocyclic Polyparaphenylene Nanolassos via Copper‐Free Click Chemistry

“…Because of its indifferent nature towards the displacement of electron density, nanohoop 2 was chosen as the host. Soft ionization methods such as matrix-assisted laser desorption ionization (MALDI) [37,39,40] and electrospray ionization (ESI) [11,37,39,41] have been successfully applied to the analysis of non-covalent CPP-fullerene host-guest complexes. For the present study, we successfully tested the application of atmospheric pressure chemical ionization (APCI).…”

N-doped nonalternant aromatic belt via a six-fold annulative double N-arylation

“…The tubular belt structures formed by annulated conjugated aromatic rings pose formidable synthetic challenges because of their high strain. 3 To date, ring-shaped, 4 planar, 5 bowl-shaped, 6 and triangle- or square-shaped aromatic molecules have only been reported. 7 An N-doped aromatic belt with nonconjugated sp 3 -linkers can also release the belt strain.…”