Interplay of Stereoelectronic and Vibrational Modulation Effects in Tuning the UPS Spectra of Unsaturated Hydrocarbon Cage Compounds

The UPS spectra of six hydrocarbon cage compounds have been investigated by a Green-function approach in conjunction with a full harmonic treatment of vibrational modulation effects. The remarkable agreement with experimental results points out the reliability of the proposed computational approach and the strong interplay of stereoelectronic and vibrational effects in tuning the overall spectra.


Assignment of UPS spectra
In what follows, computational and experimental values of transition energies for the six UPS spectra showed and discussed in the main article are provided. For what concerns the assignment of the purely electronic transition energies, the quasiparticle picture is retained.
The numeration of MOs do not take into account the core levels. The pole strength are provided in parenthesis. Values of the transition energies calculated by means of the OVGF method are provided for transition energies below 20 eV, while values calculated with the NR2 approximation are given only for transitions assigned to outer valence MOs. In the cases of 2,6-STDO (table S1) and 2,6-STDE (table S3), the computational results provided in ref. S1 are also reported.
The assignment of the vibronic transitions is carried out for five of the six compounds studied in this work. The analysis is not carried out for the 2,6-STEO molecule due to the S-1 distance between experimental and calculated values; in other words, in this case the analysis of the computed values do not have a counterpart in the real world and therefore is left out.
Normal modes associated with the most intense vibronic transitions are depicted.
Only the most intense vibronic transitions are listed, although in most of the cases many other vibronic transitions should be taken into account in order to completely reproduce the vibronic signature of a specific electronic transition.
A reduced-dimensinality scheme has been employed for the calculation of vibronic transitions of 2,6-STOT, 2,4-STDO and 2,4-STEO. The protocol is based on the exclusion (from the vibronic calculation) of all the normal modes with a fundamental frequency below a user-defined threshold. These thresholds are 800 cm −1 in the case of 2,4-STDO and 850 cm −1 in the cases of 2,6-STOT and 2,4-STEO.
S-2 S-3 Table S2: Energies, intensities and assignment of the main vibronic transitions for the first and the second bands of the spectrum of 2,6-STDO molecule.
transition main contributions energy (eV) intensity (a. u.) (1) 10.069 0.402 · 10 −3 (a) 8-th normal mode (b) 12-th normal mode (c) 24-th normal mode (d) 33-th normal mode (e) 40-th normal mode Figure S1: Graphical representation of the normal modes of 2,6-STDO, numbered with respect to the associated fundamental frequency in ascending order; only the normal modes involved in the most intense vibronic transitions are reported (see table S2). S-5 Table S4: Energies, intensities and assignment of the main vibronic transitions for the first and the second bands of the spectrum of 2,6-STDE molecule.
S-6    Figure S3: Graphical representation of the normal modes of 2,6-STOT, numbered with respect to the associated fundamental frequency in ascending order; only the normal modes involved in the most intense vibronic transitions are reported (see table S7).