PROBING THE LIMITS OF RESONANCE STABILIZATION - THE CASE OF LINEAR POLYACENES

The gas-phase basicity and proton affinity of pentacene have been dete rmined by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. AM1 semiempirical calculations for neutral and prot onated linear polyacenes ranging from benzene to pentaicosacene were c arried out. The influence of successive annellations (up to 25 rings) on structures, heats of formation, and proton affinities was investiga ted. Extrapolated values for an infinite linear polyacene have been de rived. AM1-calculated electronic structures (HOMO and LUMO energies) f or the studied linear polyacenes have been compared with the available experimental ionization potentials and electron affinities.