Correlation of the photoelectron (PE) spectra of spiro[4.4]nonatetraene (1), spiro[4.4]nona-1,3,7-triene (2), spiro[4.4]nona-1,3,6-triene (3), and spiro[4.4]nona-1,3-diene (4) yields the assignment of the first three bands at 7.99, 9.22, and 10.55 eV in the PE spectrum of 1 (symmetry D2d) to ionization processes in which the photoelectron vacates the molecular orbitals 1a2(π), lb1(π), and 7e(π), respectively. The difference ΔI(1,2) = 1.23 eV between the positions of the first two PE bands of 1 is equal, within the limits of error, to the difference ΔE (1,2) ≈ 1.2 to 1.3 eV between the first two bands 8e(π*)← 1a2(π) and 8e(π*)←1b1(π) in the electronic absorption spectrum of 1. It is shown that this correspondence is the consequence of spiroconjugation between two identical alternant subsystems in a molecule of D2d symmetry, e.g., in 1.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry