The naphthalene-benzene anion: Anion complex of aromatic hydrocarbons with the smallest electron affinity

Abstract

The mixed cluster anions between naphthalene and benzene were studied by mass spectrometry, photoelectron spectroscopy, and theoretical calculations. We found clear evidence for a stable anion of the 1:1 complex, [(Np)(1)(Bz)(1)](-), which has the smallest electron affinity measured so far for complexes of aromatic hydrocarbons. The photoelectron spectrum of [(Np)(1)(Bz)(1)](-) was identical in shape with those of (Np)(2)(-) and [(Np)(1)(H2O)(1)](-), implying the presence of a common ion core, (Np)(-), in these systems. Thus [(Np)(1)(Bz)(1)](-) is viewed to be (Np)(1)(-)(Bz)(1), where Bz stabilizes the core anion, (Np)(-), as a neutral solvent. The geometry of (Np)(1)(-)(Bz)(1) was calculated to be T-shaped, with a strong character for the pi-hydrogen bonding. An adiabatic electron affinity of 0.01 eV was determined from the measured vertical detachment energy of 0.03 eV and the theoretical estimate of the energy difference between the two neutral structures involved. (C) 2002 American Institute of Physics.