Soluble chlorofullerenes C(60)Cl(2,4,6,8,10). Synthesis, purification, compositional analysis, stability, and experimental/theoretical structure elucidation, including the X-ray structure of C(1)-C(60)Cl(10).

The efficacy of various analytical techniques for the characterization of products of C(60) chlorination reactions were evaluated by (i) using samples of C(60)Cl(6) of known purity and (ii) repeating a number of literature syntheses reported to yield pure C(60)Cl(n) compounds. The techniques were NMR, UV-vis, IR, and Raman spectroscopy, FAB, MALDI, LDI, ESI, and APCI mass spectrometry, HPLC, TGA, elemental analysis, and single-crystal X-ray diffraction. Most of these techniques are shown to give ambiguous or erroneous results, calling into question the composition and/or purity of nearly all C(60)Cl(n) compounds reported to date. The optimum analytical method for chlorofullerenes was found to be a combination of HPLC and either MALDI or APCI mass spectrometry. For the first time, the chlorination of C(60) by ICl, ICl(3), and Cl(2) was studied in detail using dynamic HPLC analysis and APCI mass spectrometry. Suitable conditions were found for the preparation of the new chlorofullerenes 1,7-C(60)Cl(2), 1,9-C(60)Cl(2), 1,6,9,18-C(60)Cl(4), and 1,2,7,10,14,24,25,28,29,31-C(60)Cl(10). The latter compound was also studied by (13)C NMR spectroscopy and X-ray diffraction, which led to the unambiguous determination of its asymmetric addition pattern. The unusual structure of C(60)Cl(10) was compared with other possible isomers using DFT-predicted relative energies. These results, along with additional experimental data and an analysis of the DFT-predicted frontier orbitals of likely intermediates, were used to rationalize the formation of the new compound C(60)Cl(10) from C(60)Cl(6) and excess ICl without the rearrangement of any C-Cl bonds. For the first time, the stability of C(60)Cl(n) compounds under a variety of conditions was studied in detail, leading to the discovery that they are, in general, very light-sensitive in solution. The X-ray structure of C(60)Cl(6) was also redetermined with higher precision.

Growth of p- and n-dopable films from electrochemically generated C60 cations.

The formidable electron-acceptor properties of C60 contrast with its difficult oxidations. Only recently it has become possible to achieve reversibility of more than one electrochemical anodic process versus the six reversible cathodic reductions. Here we exploit the reactivity of electrochemical oxidations of pure C60 to grow a film of high thermal and mechanical stability on the anode. The new material differs remarkably from its precursor since it conducts both electrons and holes. Its growth and properties are consistently characterized by a host of techniques that include atomic force microscopy (AFM), Raman and infrared spectroscopies, X-ray-photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX), matrix-assisted laser desorption/ionization (MALDI), and a variety of electrochemical measurements.

Application and evaluation of solvent-free matrix-assisted laser desorption/ionization mass spectrometry for the analysis of derivatized fullerenes.

A variety of derivatized fullerenes have been studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Of particular emphasis has been the evaluation of a recently introduced solvent-free sample/target preparation method. Solvent-free MALDI is particularly valuable in overcoming adverse solvent-related effects, such as insolubility and/or degradation of the sample. The method was applied to fullerene derivatives susceptible to decomposition under insufficiently "soft" MALDI conditions. Analytes included the hydrofullerene: C(60)H(36), fluorofullerenes: C(60)F(x) where x = 18, 36, 46, 48 and C(70)F(x) where x = 54, 56, methano-bridged amphiphilic ligand adducts to C(60) and the [4 + 2] cycloadduct of tetracene to C(60). The new solvent-free sample preparation is established as an exceedingly valuable addition to the repertoire of preparation protocols within MALDI. The MALDI mass spectra were of very high quality throughout, providing a testimony that "soft" MALDI conditions could be achieved. Using the [4 + 2] cycloadduct of tetracene to C(60) as the model analyte for direct comparison with solvent-based MALDI, the solvent-free approach led to less fragmentation and more abundant analyte ions. Applying solvent-free sample preparation, different matrix compounds have been examined for use in the MALDI of derivatized fullerenes, including sulfur, tetracyanoquinodimethane (TCNQ), 9-nitroanthracene (9-NA) and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2- propenylidene]malononitrile (DCTB). DCTB was confirmed as the best performing matrix, reducing unwanted decomposition and suppression effects.

Dynamic HPLC study of C70 chlorination reveals a surprisingly selective synthesis of C70Cl8.

A dynamic HPLC study of C(70) chlorination led to the discovery, isolation, characterization, and development of the efficient preparatory procedures for two previously unknown soluble chlorofullerenes C(70)Cl(8) and C(70)Cl(6) and for insoluble [C(70)Cl(8)](n). A novel synthesis of 99% pure C(70)Cl(10) with a nearly quantitative yield was also developed. The first stability study of C(70)Cl(10,8,6) in solution showed that these compounds are very light-sensitive.

Electron transfer reactivity in matrix-assisted laser desorption/ionization (MALDI): ionization energy, electron affinity and performance of the DCTB matrix within the thermochemical framework.

DCTB [(H(3)C)(3)C-p-Ph-CH=C(CH(3))-trans-CH=C(CN)(2)] has recently advanced to the most promising matrix material for matrix-assisted laser desorption/ionization (MALDI) within material sciences. However, data that would allow the evaluation of the electron-transfer reactivity within a thermochemical framework are sparse. The present study reports the first-time determination of the ionization energy (IE) of DCTB applying photoelectron (PE) spectroscopy. The experimental IE (8.54 +/- 0.05 eV) is in excellent agreement with the theoretical value of 8.47 eV, obtained by AM1 calculations. The same level of theory determines the electron affinity (EA) as 2.31 eV. Model analytes of known thermochemistry (phenanthrene [C(14)H(10)], anthracene [C(14)H(10)] and fluorofullerene [C(60)F(46/48)]) are used to bracket the electron-transfer reactivity within DCTB-MALDI. The formation of molecular ions of these analytes either is expected or is beyond the thermochemical accessibility of the DCTB matrix.

Formation of long-lived fluorofullerene trianions in collisions with Na.

The first experimental observation of long-lived triply charged fluorofullerene anions in the gas phase obtained from C60F48 is reported. The existence of a Coloumb barrier trapping the third electron in the trianion is supposed to be responsible for detection of the species which is estimated to have negative third electron affinity.

In-plume thermodynamics of the MALDI generation of fluorofullerene anions.

The mechanism of formation of fluorofullerene (FF) negative ions derived from the compounds C(60)F(18), C(60)F(36), and C(60)F(48) was studied by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (ToF) mass spectrometry (MS). A combined experimental/theoretical approach provides compelling evidence of nondissociative, thermodynamically controlled electron transfer from matrix-derived negative ions to the FF analyte as the main secondary-ionization process. Consistent with this thermochemical model, analyte parent molecular ion yield and degree of fragmentation for a particular MALDI experiment was found to depend on the nature of the matrix material (the five matrices investigated were sulfur, trans-2-[3-{4-tert-butylphenyl}-2-methyl-2-propenylidene]malononitrile, 9-nitroanthracene, 2,6-bis((furan-2-yl)methylene)cyclohexanone, and 2,6-bis((thiophen-2-yl)methylene)cyclohexanone). For mixtures of C(60)F(n) compounds with different n values and therefore different electron affinitites, unwanted electron-transfer reactions, which can lead to the suppression of C(60)F(n)(-) ions with low n values, were successfully blocked for the first time by judicious choice of the matrix. Therefore, reliable qualitative MS analysis of FF mixtures with wide ranges of composition is now possible.

Seven-minute synthesis of pure C(s)-C60Cl6 from [60]fullerene and iodine monochloride: first IR, Raman, and mass spectra of 99 mol % C60Cl6.

Three previously reported procedures for the synthesis of pure C(s)-C60Cl6 from C60 and ICl dissolved in benzene or 1,2-dichlorobenzene were shown to actually yield complex mixtures of products that contain, at best, 54-80% C(s)-C60Cl6 based on HPLC integrated intensities. MALDI mass spectrometry was used for the first time to identify other components of the reaction mixtures. An improved synthetic procedure was developed for the synthesis of about 150 mg batches of chlorofullerenes containing 90% C(s)-C60Cl6 based on HPLC intensities. The optimum reaction time was decreased from several days to seven minutes. Small amounts of the product were purified by HPLC (toluene eluent) to 99% purity. The pure compound C(s)-C60Cl6 is stable for at least three months as a solvent-free powder at 25 degrees C. The Raman, far-IR, and MALDI mass spectra of pure C(s)-C60Cl6 are reported for the first time. The Raman and far-IR spectra, the first reported for any C60Cl(n) chlorofullerene, were used to carry out a vibrational analysis of C(s)-C60Cl6 at the DFT level of theory.