Theoretical study of vibrational and optical spectra of methylene-bridged oligofluorenes

Vladimír Lukeš, Adelia Aquino, Hans Lischka

Research output: Contribution to journalArticle

102 Scopus citations

Abstract

We report a systematic characterization of methylene-bridged fluorene oligomers constructed of two, four, six, and eight aromatic rings using time-dependent density functional theory (TDDFT), the ab initio approximate coupled-cluster singles and doubles (CC2) method, and semiempirical spectroscopic Zerner's intermediate neglect of differential overlap method (ZINDO/S). Geometry optimizations have been performed for the ground state and for the first electronically excited state. Vertical excitations and the fluorescence transition from the lowest excited state have been calculated. Computed ground-state geometries and infrared spectra for fluorene are in good agreement with experimental results. The RI-CC2 and ZINDO/S absorption and fluorescence spectra agree very well with the available experimental data for studied fluorene oligomers and for para oligophenylenes films. On the other hand, TDDFT calculations underestimate excitation and fluorescence energies systematically for larger systems (N > 4) in comparison with the above-mentioned results. The effective conjugation length was estimated to 13-14 repeat units. The computed radiative lifetimes for the fluorene molecule show good agreement with experiment within realistic expectations. The decrease of the radiatiave fluorescence lifetime with the increase in the conjugation length has been discussed also.

Original languageEnglish
Pages (from-to)10232-10238
Number of pages7
JournalJournal of Physical Chemistry A
Volume109
Issue number45
DOIs
StatePublished - Nov 17 2005

Fingerprint Dive into the research topics of 'Theoretical study of vibrational and optical spectra of methylene-bridged oligofluorenes'. Together they form a unique fingerprint.

  • Cite this