Phosphorescence, optically detected magnetic resonance, and electron paramagnetic resonance studies of the lowest excited triplet state of the anti isomer of a 1,5-diazabicyclo[3.3.0]octadienedione (9,10-dioxa-anti-(methyl,hydrogen)bimane)

Masaaki Baba, Noboru Hirota, Edward M. Kosower

Research output: Contribution to journalArticlepeer-review

Abstract

We have studied the T1 state of the anti isomer of a 1,5-diazabicyclo[3.3.0]octadienedione by means of phosphorescence emission and excitation spectroscopy, optically detected magnetic resonance (ODMR), and EPR. From the excitation spectra the locations of the T2(3nπ*) and S1(1nπ*) states were determined in crystals and frozen solutions. It was suggested that the molecule is planar in crystals and acetonitrile but is twisted in methyltetrahydrofuran (MTHF). Contrary to the cases of many aromatic carbonyls, the radiative decay rate at the 0-0 band is the largest for the y sublevel, which indicates the importance of the spin-orbit mixing with the 1σπ* state in the radiative mechanism. The radiative activity of the x sublevel at the vibronic band is due to the 3ππ*-3nπ* and 1nπ*-1ππ* vibronic mixings. The radiationless decay takes place predominantly from the x and y sublevels as expected. In the durene mixed crystal there are two differently oriented molecules which give rise to slightly different zfs and phosphorescence spectra: D = 0.1004 cm-1 and |E| = 0.0245 cm-1, and D = 0.1000 cm-1 and |E| = 0.0235 cm-1, were obtained for these species.

Original languageEnglish
Pages (from-to)1469-1474
Number of pages6
JournalJournal of Physical Chemistry
Volume85
Issue number11
DOIs
StatePublished - 1981

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