Isomerisation of phenanthrene dication studied by tagging photodissociation ion spectroscopy and DFT calculations

Figures & data

Figure 1. Electronic tagging photodissociation spectra of He-Phen²⁺ recorded at different levels of laser power. The Y-axis shows the absolute depletion value, 1-N_i/N₀.

Figure 2. a) Far-IR tagging photodissociation spectrum of He-Phen²⁺; b) calculated vibrational spectrum of phenanthrene dication ¹1²⁺; c) Vis-IR hole-burning tagging photodissociation spectrum of He-Phen²⁺, recorded with Vis excitation fixed at 570 nm; d) calculated vibrational spectrum of isomer ¹10²⁺ (see Figure 4).

Figure 3. a) Mid-IR tagging photodissociation spectrum of He-Phen²⁺; b) calculated vibrational spectrum of phenanthrene dication ¹1²⁺; c) IR-IR hole-burning tagging photodissociation spectrum of He-Phen²⁺, recorded with pump IR excitation fixed at 1427 cm⁻¹; d) calculated vibrational spectrum of isomer ¹10²⁺ (see Figure 4).

Figure 4. Geometries and relative energies in kJ mol⁻¹ of various C₁₄H₁₀²⁺ isomers. The energies are given at 0 K (including zero-point vibrational energy) relative to the energy of phenanthrene dication in the singlet ground state (¹1²⁺). Note that ¹25²⁺ and ¹26²⁺ have -C≡C- motif between the phenyl rings appearing as one long connection and ¹28²⁺ has -C≡C- as a part of the macrocycle.

Figure 5. Harmonic IR spectra of the low-energy isomers of C₁₄H₁₀²⁺.

Figure 6. Calculated anharmonic spectra of a) phenanthrene dication ¹1²⁺ and selected lowest energy structures, namely b) ¹10²⁺, c) ¹2²⁺, d) ³1²⁺, e) ¹3²⁺,and f) ¹11²⁺. The intensity of the theoretical bands in a) and b) mid-IR region are scaled for better visibility.