Thermotropic Behavior of Lipophilic Derivatized [60]Fullerenes Studied by Deuterium NMR, X-ray Diffraction, and Microcalorimetry

Abstract

The dynamics, structure, and thermotropic behavior of a new class of lipophilic [60]fullerene (C60) derivatives, so-called lipo-fullerenes, have been studied by differential scanning calorimetry (DSC), deuterium nuclear magnetic resonance (2H NMR), and X-ray scattering. The lipo-fullerene studied consists of six pairs of perdeuterated C18 alkyl chains as substituents of six covalently attached methylene groups in octahedral sites. The symmetry of this highly symmetrical hexamethanofullerene is T h . We find drastic changes of the molecular arrangement of the lipo-fullerenes induced by temperature. Heating the sample from 20 to 70 °C causes it to undergo two major structural transitions. At 55 °C we observe an exothermic transition from a low-temperature, hard sphere-like packing state of the molecules, with separation distances (6.1 nm) slightly above the maximum diameter of the molecules, to a condensed one. This latter state involves partial intercalation (interdigitation) of the alkyl chains belonging to adjacent molecules and is preceded by partial melting of the chains to accommodate sterically for the (exothermic) interdigitation. The latter allows denser packing with an average separation distance of 4.8 nm. At a temperature of 64 °C, an endothermic melting transition from the interdigitated to a viscous fluidlike state is observed, with an average separation distance of 2.8 nm. Cooling the sample from 70 °C causes a direct transition from the fluid into the low-temperature state with no interdigitation of the chains.

C60 Hexakisadducts with an Octahedral Addition Pattern − A New Structure Motif in Organic Chemistry

“…The dynamics, structure and thermotropic behaviour of this unprecedented type of membrane composite have been studied by means of microcalorimetry, deuterium NMR and X-ray scattering. [15,16] The spherical lipofullerenes show a pronounced tendency toward spontaneous formation of spatially anisotropic superstructures, which may be of importance for future membrane technology. [16] In order to polymerise aggregates of lipofullerenes, we synthesized the functional lipofullerene 13, containing six pairs of dioctadeca-10,12-diynyl chains.…”

“…[15,16] The spherical lipofullerenes show a pronounced tendency toward spontaneous formation of spatially anisotropic superstructures, which may be of importance for future membrane technology. [16] In order to polymerise aggregates of lipofullerenes, we synthesized the functional lipofullerene 13, containing six pairs of dioctadeca-10,12-diynyl chains. After intercalation of 13 in DPPC vesicles, a photochemically induced polymerization was carried out.…”

Self- or Induced Organization of [60]Fullerene Hexakisadducts

“…In addition, small anisotropic units are often insufficient as interactions are too weak to generate mesomorphism [72]. Examples of C 60 derivatives possessing a high LC character (bearing more than two anisotropic moieties per C 60 via polyaddition [73] or dendritic approach [74][75][76][77]) showed either a transient nematic [78], a chiral nematic [79], or a smectic A phase [80,81]. In these cases, the properties of the materials were mostly dominated by the anisotropic moieties, due to dilution of the C 60 moiety.…”

Spreading behaviour of a series of amphiphilic [3 : 3] [60]fullerene hexakisadducts: a systematic study

“…The preparation, characterisation and functionalisation of [60]fullerene thin films such as self-assembled monolayers (SAMs) [1][2][3][4][5][6], self-organised bilayers [7][8][9][10], or Langmuir-Blodgett films [11][12][13][14][15] are currently of great interest from both fundamental and practical viewpoints owing mainly to their unique electronic and/or structural characters. Both the SAM approach, achieved through junction moieties such as organosilane [16], organosulfur [17], or carboxylic acid [18], and the Langmuir technique allow control of the formation and the structure of the resulting film at a molecular level.…”