Electron Autodetachment from Isolated Nickel and Copper Phthalocyanine−Tetrasulfonate Tetraanions:  Isomer Specific Rates

Abstract

Electron autodetachment from isolated metal phthalocyanine-tetrasulfonate tetraanions (MPc(SO 3 ) 4 4-) (M)Ni, Cu) was studied at room temperature in an FT-ICR mass spectrometer under UHV conditions. For M ) Cu, the electron loss rate was measured for the as-prepared isomer mixture. In the case of M ) Ni, two chromatographically purified fractions containing different compositions of constitutional isomers were studied. The observed rate constants for these fractions differed by a factor of 37 ( 5. Photoelectron spectroscopy indicates that both Cu and Ni compounds comprise isomer ensembles which are electronically metastable. Model calculations suggest that the differing electron loss rates observed for the Ni isomer fractions reflect tunneling through repulsive Coulomb barrier surfaces, which are themselves strongly isomer dependent in shape and height.

A multi-agent quantum Monte Carlo model for charge transport: Application to organic field-effect transistors

“…[4][5][6]32,33 The Kappes group successfully integrated an ESI source to a RT hexapole ion trap and a magnetic-bottle PES analyzer for the studies of MCAs. [38][39][40] One of the limitations of the first ESI-PES apparatus was the lack of ion temperature control because the Paul trap was operated at room temperature. Molecular ions, in particular complex MCAs or weakly bounded anions, could carry substantial internal energies even at RT.…”

“…[75][76][77][78][79][80] The coupling of ESI with PES allowed MCAs to be spectroscopically characterized for the first time. [4][5][6][32][33][34][35][36][37][38][39][40] When an electron is detached from a MCA, it experiences a short-range attraction by the nuclei and a long-range repulsion from the negatively charged residual ion, resulting in the socalled RCB (Fig. 2(a)).…”

“…2(b)). 38,[81][82][83][84] The strong intramolecular Coulomb repulsion not only influences the energetics and stability of MCAs, but it is also expected to strongly influence the electron emission dynamics, which can be investigated using PE imaging by measuring the photoelectron angular distribution. [85][86][87] The first PE imaging on MCAs was done on a series of linear aliphatic dicar- [88][89][90] which were expected to display strong anisotropy in the PE angular distribution.…”

Resonant tunneling through the repulsive Coulomb barrier of a quadruply charged molecular anion

“…The RCB provides dynamic stability to MCAs and allows long-lived metastable MCAs with negative electron binding energies to be observed [9][10][11][12]. Metastable MCAs can undergo spontaneous electron emission from their ground states by tunneling through the RCB, analogous to α-decay for radioactive nuclei [11][12][13][14][15][16].…”

“…Metastable MCAs can undergo spontaneous electron emission from their ground states by tunneling through the RCB, analogous to α-decay for radioactive nuclei [11][12][13][14][15][16]. Such decay has been studied using ion trap mass spectrometry, yielding tunneling lifetimes on the order of seconds for a number of metastable MCAs at room temperature [11,12,16].…”