New Supramolecular Complex of C₆₀ Based on Calix[5]arene—Its Structure in the Crystal and in Solution

Abstract

Buckminsterfullerene and its related fullerenes have generated a rapidly growing and active research area."] The former is one of the most impressive molecules because of its cagelike, truncated icosahedral structure. This molecule, a weak electronacceptor, forms clathrates in the solid state."] The selective formation of a clathrate from C,, and calix[8]arenes was excellently utilized for the separation of C,, and C,0.[31 Supramolecular complexes of C,, in solution are limited in the aqueous systhough extremely weak charge transfer (CT) complexes ['] are known in organic solvents. Quite recently weak inclusion complexes of C,, and calix[6]arenes have been reported.16] Because of the smooth and dense surface of C,,, it can be bound through an accumulation of weak van der Waals interactions, even in organic solvents, if a host with a suitably complementary shape is selected. In this paper we report the binding of calix-[5]arene['] receptors to C,, in organic solvents and the crystal structure of the inclusion complex.A color change (purple +pale yellow) was observed in the solution of C,, upon addition of the receptor (1). The intensity of the shoulder in the guest's absorption band in the 400-470 nm region increased (Figure 1) with the addition of the receptor (1).

Complexes of p-tert-butylcalix[5]arene with lanthanides: synthesis, structure and photophysical properties †

“…This X-ray analysis confirms that the reaction of H 5 L with a dmso adduct of a nitrate salt of europium in the presence of a strong base leads to the isolation of a dimeric complex, as for the parent p-tert-butylcalix [4] ).…”

“…A single-crystal analysis of [Eu 2 (H 2 L) 2 (dmso) 4 ]ؒ 10thf showed the deformation of the cone conformation of the calixarene upon complexation and co-ordination of dmso molecules by inclusion through the hydrophobic cavity of the ligand. A photophysical investigation revealed a total quenching of the metal luminescence by a ligand-to-metal charge-transfer state in the case of Eu III while luminescence of Tb III is sensitised (quantum yield in thf: 5.1%).…”

“…The cyclic framework of calixarenes, 1 associated with the presence of phenol oxygen donor atoms, affords an interesting platform for the complexation of metal atoms, 2 while the hydrophobic cavity allows the inclusion of charged 3 and neutral 4 organic guests. The relative facility with which calixarenes can be partially or totally functionalised at the upper or lower rims, coupled with their easy large-scale synthesis, at least for the even members of the series (n = 4, 6 or 8), has opened further perspectives for their use in supramolecular chemistry.…”

“…While p-tert-butylcalix [8]arenes form bimetallic complexes in which the ligand is six times deprotonated, 11 the six-membered parent calixarene is bonded to Ln III by a single phenolate group. 12 In the case of p-tert-butylcalix [4]arene 2 : 2 dimeric complexes were obtained, in which the two metal atoms are separated by only 3.91 Å. 13 In our laboratory we have mainly studied the photophysical properties of bimetallic complexes with p-tert-butylcalix [8]arene [14][15][16] and demonstrated the influence of the low-lying ligand-to-metal charge-transfer state (LMCT) on the Eu III -containing assemblies, which enhances the f-f absorption probabilities through mixing with the 4f orbitals and quenches the 5 D 0 (Eu) excited level.…”

Structural Diversity of Host–Guest and Intercalation Complexesof Fullerene C60

“…[40] Other authenticated structures in which C 60 is encapsulated by two calix [5]arenes such that there are no interfullerene contacts include a calix [5]arene complex with three methyl and two iodo groups (1,3-disposition) in the p-positions of the upper rim. [41] . [38] Oxacalix [3]arenes 2 also have complementarity of curvature with C 60 , and p-benzyloxacalix [3]arene similarly forms a 2:1 complex in which two calixarenes shroud the fullerene.…”