Jump to main content
Jump to site search


Unraveling structural dynamics in isoenergetic excited S1 and multi-excitonic 1(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy

Author affiliations

Abstract

Polyacenes, such as anthracene, tetracene, pentacene etc., have been identified as potential candidates for singlet fission (SF) and triplet–triplet annihilation (TTA) processes in their crystalline and thin film forms as they possess significant singlet and triplet exciton couplings. Interestingly, phenyl-ethynyl substitution to anthracene at the 9,10 positions (9,10-bis(phenylethynyl)anthracene/BPEA) enhances the transverse π-electron conjugation and retains the planar structure even in the excited state. The excited singlet state S1 and the multi-excitonic state 1(TT) in BPEA are separated by ∼30 meV (∼250 cm−1) making it an ideal system for both SF and TTA applications. BPEA is very effective in photon up-conversion even for low input intensities. Transient absorption measurements of BPEA in n-hexane solution are inadequate for distinguishing the S1 state and the multi-excitonic state 1(TT), since the spectroscopic features are complex (mixed) due to the isoenergetic nature and the existence of an equilibrium between these states. However, ultrafast Raman loss spectroscopy reveals a systematic red shift and a blue shift in the central frequencies of the Raman modes corresponding to C[double bond, length as m-dash]C and C[triple bond, length as m-dash]C vibrational frequencies with time constants of ∼2.0 and ∼20 ps, respectively. Such a shift in the Raman frequencies is direct evidence of the structural changes that take place while changing from excited singlet state S1 to the multi-excitonic state on the potential surface.

Graphical abstract: Unraveling structural dynamics in isoenergetic excited S1 and multi-excitonic 1(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy

Back to tab navigation

Supplementary files

Publication details

The article was received on 26 Oct 2018, accepted on 21 Jan 2019 and first published on 22 Jan 2019


Article type: Paper
DOI: 10.1039/C8CP06658B
Citation: Phys. Chem. Chem. Phys., 2019, Advance Article

  •   Request permissions

    Unraveling structural dynamics in isoenergetic excited S1 and multi-excitonic 1(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy

    S. Jana, A. L. Yapamanu and S. Umapathy, Phys. Chem. Chem. Phys., 2019, Advance Article , DOI: 10.1039/C8CP06658B

Search articles by author

Spotlight

Advertisements