Cycloparaphenylene‐Based Ionic Donor–Acceptor Supramolecule: Isolation and Characterization of Li⁺@C₆₀⊂[10]CPP

Abstract

The first cycloparaphenylene (CPP)-based ionic donor-acceptor supramolecule Li(+)@C60⊂[10]CPP⋅X(-) has been synthesized. X-ray crystallography not only confirmed the molecular structure of Li(+)@C60⊂[10]CPP⋅X(-) but also uncovered the formation of a unique ionic crystal. The strong charge-transfer interaction between [10]CPP and Li(+)@C60, which was confirmed by electrochemical measurement and spectroscopic analyses, caused significant delocalization of the positive charge across the entire complex.

Electronic Communication between two [10]cycloparaphenylenes and Bis(azafullerene) (C59N)2 Induced by Cooperative Complexation

“…Initially,D PV of free [10]CPP in o-DCB revealed an oxidation peak at 0.88 V ( Figure 4). On addition of 0.25 equivalents of (C 59 N) 2 ,abroad oxidation signal appeared, which upon addition of further (C 59 N) 2 resulted in the evolution of two peaks,a t0 .68 Va nd 0.84 V. When excess (C 59 N) 2 was added, the peak at 0.68 Vbecame stronger than that at 0.84 V. Overall, considering the [10]CPP'-(C 59 N) 2 &[10]CPP complex, the [10]CPP oxidation potential was cathodically shifted by approximately 40 mV,c orroborating the easier oxidation of [10]CPP when complexed with the azafullerene.T his behavior is in contrast to the [10]CPP'C 60 but compares to the 20 mV shift observed for Li@C 60 [16] confirming the development of charge-transfer phenomena from the CPP to azafullerene as suggested by the calculations.I nterestingly,asecond oxidation peak, at even less-positive potentials developed, corresponding to the oxidation of the second CPP of the [10]CPP'(C 59 N) 2 &- [10]CPP complex, which shows increased charge transfer with its fullerene host, in agreement with our calculated charge states of the [10]CPP pair on the dimer. This splitting is also reflected in the HOMO and LUMO states ( Figure 5).…”

“…Binding constants for the [10]CPP units were calculated and found to be K 1 = 8.4 10 6 m À1 for the first CPP and K 2 = 3.0 10 6 m À1 for the second ( Figure S2). [15,16] Markedly,t he cooperativity factor a shows av alue greater than one (a = 1.45), supporting attractive interactions between the two [10]CPP macrocycles (for calculation see Supporting Information). [15,16] Markedly,t he cooperativity factor a shows av alue greater than one (a = 1.45), supporting attractive interactions between the two [10]CPP macrocycles (for calculation see Supporting Information).…”

“…[14][15][16][17][18][19] Forexample,in [10]CPP'C 60 ,the best fit of [10]CPP,w ith 1.4 nm diameter,w as for C 60 [14,15] as well as Li@C 60 [16] and [11]CPP,with 1.5 nm diameter, for C 70 [17] as well as La@C 82 . In those complexes,t here is ah igh size-specificity between the CPP,b ased on the number of conjugated aromatic rings,a nd the size of the carbon cage.…”

Strain‐Promoted Reactivity of Alkyne‐Containing Cycloparaphenylenes

“…Fort he ratedetermining step (DG°2 98 K = 22.1 AE 0.6 kcal mol À1 )t he entropic contribution (DS°= À37.5 AE 1.0 cal K À1 mol, at 298 K: DS°2 98 K = À11.2 AE 0.3 kcal mol À1 )s lightly exceeds that of the enthalpy (DH°= 10.9 AE 0.3 kcal mol À1 ;Supporting Information, Figure S44, Table S1). [31,50] Additionally,u pon reaction the appealing photophysical properties of the parent macrocycle are largely retained (l abs 328 nm, l em 448 nm, Figure 5b), including high fluorescence quantum yields for the click adduct 21 (F = 0.77) and its parent macrocycle 3 (F = 0.80). [49] Thep redicted difference in reaction energies for 1 and DPA is 22.6 kcal mol À1 (Figure 4), which can be ascribed to the significant release of strain energy in 1 upon [2+ +2]CA-RC reaction, as determined by homodesmotic reactions (Supporting Information).…”

Anorganische Molekülchemie

“…Die Kombination spektroskopischer (UV/Vis-NIR) und elektrochemischer Analysen zeigte, dass die Spezies durch starke Ladungstransferwechselwirkungen und eine deutliche Delokalisierung der positiven Ladung gekennzeichnet ist, wobei letztere noch über die für Li + @C 60 ermittelte hinausgeht. 1) Dass auch neutrale Moleküle jenseits der Fullerene Lithium und Natrium in Abwesenheit von Lewis-Basen binden, zeigten Chemiker mit dem Diborin B 2 (NHC) 2 (NHC = :C{N(2,6-Dipp)CH} 2 ; Dipp = 2,6-Diisopropylphenyl). Die so erzeugten Dikationen [M 2 (B 2 (NHC) 2 )] 2+ ((1), M = Li, Na) enthalten zwei Alkalimetallionen, die sich auf beiden Seiten der B≡B-Bindung zwischen den ekliptisch angeordneten Phenylringen der NHCs befinden.…”