Intersystem crossing processes in nonplanar aromatic heterocyclic molecules

Karin Schmidt*, Sergio Brovelli, Veaceslav Coropceanu, David Beljonne, Jérôme Cornil, Cristina Bazzini, Tullio Caronna, Riccardo Tubino, Francesco Meinardi, Zhigang Shuai, Jean Luc Brédas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

257 Scopus citations


A comprehensive study of the photophysical properties of a series of monoaza[5]helicenes is presented on the basis of joint optical spectroscopy and quantum chemistry investigations. The molecules have been characterized by absorption and CW/time-resolved luminescence measurements. All quantities related to spin-orbit-coupling processes, such as intersystem crossing rates and radiative phosphorescence lifetimes, were found to depend strongly on the nitrogen position within the carbon backbone. Density functional theory and semiempirical quantum-chemical methods were used to evaluate the molecular geometries, the characteristics of the excited singlet and triplet states, and the spin-orbit coupling matrix elements. We demonstrate that the magnitude of spin-orbit coupling is directly correlated with the degree of deviation from planarity. The trends from the calculated photophysical quantities, namely, radiative fluorescence and phosphorescence decay rates and intersystem crossing rates, of the mono-aza-helicenes are fully consistent with experiment.

Original languageEnglish (US)
Pages (from-to)10490-10499
Number of pages10
JournalJournal of Physical Chemistry A
Issue number42
StatePublished - Oct 25 2007
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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