Coarse-Grained Modeling of the Titration and Conductance Behavior of Aqueous Fullerene Hexa Malonic Acid (FHMA) Solutions

Abstract

The coarse-grained continuum primitive model is developed and used to characterize the titration and electrical conductance behavior of aqueous solutions of fullerene hexa malonic acid (FHMA). The spherical FHMA molecule, a highly charged electrolyte with an absolute valence charge as large as 12, is modeled as a dielectric sphere in Newtonian fluid, and electrostatics are treated numerically at the level of the non-linear Poisson-Boltzmann equation. Transport properties (electrophoretic mobilities and conductances) of the various charge states of FHMA are numerically computed using established numerical algorithms. For reasonable choices of the model parameters, good agreement between experiment (published literature) and modeling is achieved. In order to accomplish this, however, a moderate degree of specific binding of principal counterion and FHMA must be included in the modeling. It should be emphasized, however, that alternative explanations are possible. This comparison is made at 25 °C for both Na(+) and Ca(2+) principal counterions. The model is also used to characterize the different charge states and degree of counterion binding to those charge states as a function of pH.

Basic hydrolysis of fullerene-based esters: a tiny step away from nucleophilic addition to fullerene

“…18 We have used C 60 (99.5+ % purity), supplied by MER Corporation (USA), 9,10-dimethylanthracene (99%, Aldrich), 1,8-diazabicyclo [5,4,0]undec-7-ene (98%, Aldrich), and diethyl bromomalonate (95%, Merck). Reaction product was purified by column chromatography using SiO 2 as a stationary phase (Kieselgel 60, 0.043-0.060 mm), and toluene/ethyl acetate mobile phase (95:5 v/v at the beginning, and 88:12 v/v at the end of the chromatographic separation).…”

“…One of such topics is investigation of properties of solutions of highly charged particles where salts of T h -symmetric fullerenehexamalonic acids (T h -C 66 (COOH) 12 , in further text denoted as T h -FHMA ) are almost ideal model compounds. [3][4][5][6] It is not only that C 60 's spherical shape significantly facilitates calculation of electrostatic field around the functionalized molecule; 7,8, in numerous cases rigidity of its skeleton is equally important as well as exactly defined number of ionizable functional groups in the molecule. 5 The synthesis of welldefined T h -FHMA sample, however, is accompanied with serious difficulties.…”

“…[3][4][5][6] It is not only that C 60 's spherical shape significantly facilitates calculation of electrostatic field around the functionalized molecule; 7,8, in numerous cases rigidity of its skeleton is equally important as well as exactly defined number of ionizable functional groups in the molecule. 5 The synthesis of welldefined T h -FHMA sample, however, is accompanied with serious difficulties. The most troublesome is the final step of the synthesis where, during the hydrolysis of T h -FHMA ester into its salt, partial decarboxylation as a side reaction was observed.…”