Electronic States of Anthanthrene. Linear and Magnetic Circular Dichroism, Fluorescence Anisotropy, and Quantum Chemical Calculations

Abstract

The pericondcnsed henzenoid hydrocarbtm (Uithantlirene {dibenz.ol\\c\,\xw\ojclirysene, dibetizolcL\,\\^jpyretu'i was investigated by UV-VIS and IR linear dlchroistn (L!^) spectroscopy in stretchedpolyerhyteui', by UV-VIS magnetic circular dichtoiini (MCD) spectroscopy, and by Jltiorescence polarization anlsotmpy measurements. The combitied results led to a detailed experimental ciiaracterization of electronic transitions in the near-UV and visible regions, with determination of polarization directions. In particular, the results allowed an unambiguous assignment ofthe weak Li, transition (corresponding to Ctar's a-band), in spite ofoveriap with the ntttch sttonger L,, transition (Clar's p-bttnd). This assignment, which is at variance with a previous suggestion, was supported by a study of solvent and temperature shifts. The e.xperimental results were compared with theoretical 23 24 C. Johannessen et ai ptedictions using the LCOAO procedure. E.xcellent agreentent with observed transitions was obtained, including transition moment directions and MCD signs. The theoretical {tnalysis revealed a signifwaut bteakdown ofthe altetttattt pairing sytnmetryfor atuhatithrene, correspottding to AHOMO > ALUMO, Sittiilar to benzol a Ipyt ene, atuhanthrene can be classified as a positive-hard MCD chtvntophore in Michl's tertnmology.

Water-Insoluble Organics Dominate Brown Carbon in Wintertime Urban Aerosol of China: Chemical Characteristics and Optical Properties

“… a The blue and red lines in the UV–Vis spectra represent the main chromophores in aerosol samples and the standard compounds, respectively. Legend for superscript numbers: (1) ionization mechanism [M + H] ± for protonated, [M – H] − for deprotonated, and [M • ] + for ion radical; (2) standard compounds measured in our study; (3) The MS signal was not detectable due to low ESI ionization efficiency. ,, …”

“…The low ESI ionization efficiency for nonpolar organic molecules, however, hinders the identification of those WI-BrC chromophores with low concentrations. Future studies should combine 2D HPLC-PDA-HRMS with different ionization techniques (e.g., atmospheric-pressure photoionization) to provide a more comprehensive characterization of BrC chromophores in ambient aerosol. ,, …”

Efficiency of Noncoherent Photon Upconversion by Triplet–Triplet Annihilation: The C60 Plus Anthanthrene System and the Importance of Tuning the Triplet Energies

“…(iv) Substitution of the An ring system can be used to systematically tune its electronic energies and photophysical properties. 31 Johannessen et al 37 have reported the most thorough study of An's UV−visible absorption spectrum. They assign its lowest-energy absorption band in the violet to a 1 B 2u − 1 A 1g electric-dipole-allowed transition that exhibits a slight red shift in solvents of increasing polarizability.…”

“…Johannessen et al have reported the most thorough study of An’s UV–visible absorption spectrum. They assign its lowest-energy absorption band in the violet to a 1 B 2u – 1 A 1g electric-dipole-allowed transition that exhibits a slight red shift in solvents of increasing polarizability.…”

Photochromism and polarization spectroscopy of p-methyl(thiobenzoyl)acetone

“…A fruitful approach in such situation is to combine different experimental techniques, studies in various spectral ranges, e.g. visible and IR, and to correlate transition moments in the electronic and vibrational spectra [3][4][5][6][7][8]. The most popular techniques for the determination of transition moment directions include linear dichroism (LD) and luminescence anisotropy.…”