ABSTRACT
Gas-phase ion chromatography can separate ions that have the same mass but differ in isomeric structure or electronic configuration. The main features of this technique are briefly outlined, and applications to a series of problems in transition metal chemistry and carbon cluster chemistry are described. Examples in transition metal chemistry include state-selective reactivity, excited state deactivation, and state-selective ligand binding energies. For clusters, ion chromatography was used to determine the structure of pure carbon cluster ions as a function of size from C(4) to C(84). The results indicate that carbon grows first in linear chains, transforms to monocyclic planar rings at about C(10), and forms new families of planar bi-, tri-, and tetracyclic rings at C(20), C(30), and C(40), respectively. Fullerenes, which mysteriously appear at C(30) and dominate by C(50), are generated by heating the planar ring systems above an isomerization barrier rather than by growth of graphite precursors.
ABSTRACT
The structure of small carbon cluster anions, Cn(-) (4 = n = 20), was investigated with the use of ion chromatography. With this technique, both the existence and the relative amounts of possible structural isomers can be determined. More than 99% of the ions C(5)(-) to C(9)(-) were found to be linear under these experimental conditions. Starting with C(10)(-), a monocyclic isomer was observed, and linear and moncyclic structures coexisted from C(10)(-) through at least C(20)(-). This result is in contrast to previous work on positive ions, which showed the existence of linear isomers from C(5)(+) to C(10)(+), with linear and cyclic isomers coexisting only from C(7)(+) to C(10)(+). Above C(10)(+), no linear clusters were observed.