Electronic properties of kekulene

Abstract

The fluorescence and phosphorescence of kekulene in a host matrix of polycrystalline tetrachlorobenzene are investigated, together with the triplet zero field splitting parameters IDI and lEI obtained by ODMR in zero field. The D value is also calculated within a semi-empirical 1T-theory and compared with experiment. It could be shown that the triplet state energies of a number of different sites of kekulene in the host matrix and the zero field splitting parameters are related, in first order, by spin orbit interaction.

Novel series of giant polycyclic aromatic hydrocarbons: electronic structure and aromaticity

“…The molecules 11 and 13 are included for testing purposes because they are the largest PAHs with available experimental electronic spectra. The calculated electronic transitions, oscillator strengths, and available experimental results (for 1 [31], 11 [6], and 13 [7]) are listed in Table 1. The term Bright State was used in case of the largest oscillator strengths.…”

MP2 and DFT Calculations on Circulenes and an Attempt to Prepare the Second Lowest Benzolog, [4]Circulene

“…Whereas 36 is a well-investigated hydrocarbon, [45] its two isomers shown in Scheme 8 are so far unknown. As far as their geometries are concerned, 38 should be especially interesting.…”

Structures and 1H‐chemical shifts of conjugation deficient hydrocarbons

“…The large nonsinglet root A', for 3a corresponds to the rather large triplet excitation energy and zero-field splitting parameter D [ 6 ] . Also for l a and 2a large triplet excitation energies are observed [33].…”

“…A represents one of the possible four KekulC structures for two concentric noninteracting perimeters, thus forming a "super sextet" [4] C. It is of interest to investigate whether the electronic structure of cycloarenes or corannulenes is dominated by A-or B-type KekulC resonance structures. Theoretical studies on cycloarenes [5-81 as well as experimental work on kekulene [6,9] revealed that cycloarenes cannot be considered as macrocyclic annulenes.…”

“…They represent corannulenes with (n,n') = (2,14), (6,18), and (18,30) for the inner [n]-and outer [n '1 perimeters. The conjugation deficient nonalternant hydrocarbons lb, 2b, and 3b are derived from the alternant conjugated systems pyrene (la), coronene (h), and kekulene (3a) by replacing 6-rings by 5-rings and 7-rings.…”