Fig. 3: ISE in fluorescence spectra of neutral and charged phthalocyanines.
STML spectra (acquisition time t = 120 s) of (a) H2Pc (I = 100 pA, V = −2.5 V), (b) HPc− (I = 60 pA, V = −2.5 V), and (c) a Pc2− (I = 100 pA, V = 2.5 V) on 3ML NaCl/Ag(111). The spectrum of HPc− was obtained by resonant energy transfer from a neighboring ZnPc. The vertical dashed lines correspond to TD-DFT calculations of the S0 → S1 absorption energies for H2Pc, HPc−, and Pc2−, rigidly shifted by −250 meV to fit the experiment. This shift can be rationalized by considering that the dynamical screening linked to the presence of the NaCl/Ag(111) substrate and of the STM tip are not accounted for by our theoretical approach. While this prevents a quantitative comparison between experimental and theoretical energies, this procedure shows that theory accurately predicts the energy shift upon deprotonation. d Comparison between TD-DFT absorption energies calculated for H2Pc, HPc−, and Pc2− (blue dots) and TD-DFT absorption energies calculated for a Pc2− as a function of partial positive charges added artificially in its center (white dots). The line through the white dots is a parabolic fit with the parameters given in inset. Source data are provided as a Source Data file.
