Highly Efficient Synthesis of Globular (Bola)amphiphilic [5:1]Hexakisadducts of C₆₀

Abstract

We report on the very facile access of a new family of amphiphilic and bola-amphiphilic fullerene [5:1]hexakisadducts 9a-f and 11a-e. The key point for this successful approach is the use of C(2v)-symmetrical fullerene pentakisadduct precursors 2b-f allowing for the completely regioselective addition of a sixth malonate addend to complete the octahedral [5:1] addition pattern. For the synthesis of the new amphiphiles we first developed a new second-generation dendrimer containing 9 tert-butoxycarbonyl (Boc)-protected amino functions at the periphery and two new malonates containing 6 or 18 Boc-protected amino termini, respectively. The hexakisadducts contain up to 18 positive or negative charges at the dendritic moiety and either no or ten positive or negative charges at the unbranched malonate positions after deprotection with trifluoroacetic acid (TFA). The charge state at the termini is pH-dependent. Complete structural characterization of the new compounds was carried out by ESI mass spectrometry and by UV/Vis, FTIR, (1)H NMR and (13)C NMR spectroscopy. We were also able to obtain the first X-ray crystal structure of pentakisadduct (2a) with a C(2v)-symmetrical addition pattern. The new amphiphilic hexakisadducts show interesting solubility properties in water. Initial investigations on the aggregation properties of the amphiphilic hexakisadduct 12c by using dynamic light scattering (DLS) and conductivity measurements, show aggregates with a radius up to 200 nm and a critical micelle concentration (CMC) of approximately 8 mg L(-1).

Mono‐ and Ditopic Bisfunctionalization of Graphene

“…As a consequence, promising practical applications of nanocarbons such as in sensors, nanocomposites, and biomedical products can be targeted. The construction of molecular architectures consisting of a carbon allotrope core and two or more different covalently attached functionalities has so far been realized with fullerenes and carbon nanotubes, whereas examples for mixed graphene derivatives are still elusive. One of the most efficient methods for the functionalization of graphene is the reduction/exfoliation of graphite with alkaline metals in suitable solvents followed by quenching of the intermediately formed graphenides with electrophiles (Scheme a).…”

“…Multiple covalent functionalization of synthetic carbon allotropes,s uch as fullerenes,c arbon nanotubes,a nd graphene,w ith different addends represents an attractive concept for the design and combination of specific chemical, physical, and materials properties.A saconsequence,p romising practical applications of nanocarbons such as in sensors, [1] nanocomposites, [2] and biomedical products [3] can be targeted. Thec onstruction of molecular architectures consisting of ac arbon allotrope core and two or more different covalently attached functionalities has so far been realized with fullerenes [4][5][6][7][8][9][10] and carbon nanotubes, [11][12][13][14][15] whereas examples for mixed graphene derivatives are still elusive. One of the most efficient methods for the functionalization of graphene is the reduction/exfoliation of graphite with alkaline metals in suitable solvents followed by quenching of the intermediately formed graphenides with electrophiles (Scheme 1a).…”

Mono‐ und ditope Bisfunktionalisierung von Graphen

“…Dadurch lassen sich vielversprechende praktische Anwendungen im Bereich der Sensorik, [1] des Nanokompositaufbaus [2] und biomedizinischer Produkte [3] verwirklichen. Die Synthese derartiger molekularer Architekturen, bestehend aus einem Kohlenstoffallotrop-Kern und zwei oder mehreren unterschiedlichen kovalent gebundenen Funktionalitäten, konnte im Bereich der Fulleren- [4][5][6][7][8][9][10] und der Kohlenstoffnanorçhrenchemie [11][12][13][14][15] bereits realisiert werden. Demgegenüber erschien der zielgerichtete Aufbau von gemischtfunktionalen Graphenderivaten nur schwer umsetzbar.E ine der effizientesten Methoden der Graphenfunktionalisierung basiert auf der Reduktion/Exfolierung von Graphit mit Alkalimetallen in inerten Lçsungsmitteln und nachfolgendem Abfangen der intermediär gebildeten Graphenide mit geeigneten Elektrophilen (Schema 1a).…”

The first one-pot synthesis of a chiral pentakis-adduct of C60 utilising an opened-structure malonate tether

“…This activated [6,6] double bond can be selectively functionalised with a wide range of molecules, in a completely regioselective manner as well-established in the literature both theoretically and experimentally. 3,4 The first synthesis of a cyclopropanated pentakis-adduct of C 60 was reported in 1994, by Hirsch. 3 Starting from an e,e,e tris-adduct and employing stepwise Bingel 5 additions followed by preparative HPLC separations, a pentakis-adduct equipped with malonate ester moieties was successfully isolated and fully characterised.…”