Unraveling structural dynamics in isoenergetic excited S-1 and multi-excitonic (1)(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy Electronic supplementary information (ESI) available: Summary of the concentration-dependent kinetics of TA of BPEA, and the molecular structure of BPEA along with its numbering on each atom. See DOI: 10.1039/c8cp06658b

Jana, Sanjib and Yapamanu, Adithya Lakshmanna and Umapathy, Siva (2019) Unraveling structural dynamics in isoenergetic excited S-1 and multi-excitonic (1)(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy Electronic supplementary information (ESI) available: Summary of the concentration-dependent kinetics of TA of BPEA, and the molecular structure of BPEA along with its numbering on each atom. See DOI: 10.1039/c8cp06658b. In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 21 (26). pp. 14341-14349.

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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 pi-electron conjugation and retains the planar structure even in the excited state. The excited singlet state S-1 and the multi-excitonic state (1)(TT) in BPEA are separated by similar to 30 meV (similar to 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 S-1 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, ultra fast Raman loss spectroscopy reveals a systematic red shift and a blue shift in the central frequencies of the Raman modes corresponding to C C and C C vibrational frequencies with time constants of similar to 2.0 and similar to 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 S-1 to the multi-excitonic state on the potential surface.

Item Type:	Journal Article
Publication:	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publisher:	ROYAL SOC CHEMISTRY
Additional Information:	Copyright of this article belongs to ROYAL SOC CHEMISTRY
Keywords:	TRIPLET-TRIPLET ANNIHILATION; SINGLET FISSION; UP-CONVERSION; PENTACENE; MECHANISM; NANOPARTICLES; SEPARATION; TETRACENE; COHERENT; PLATFORM
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited:	18 Nov 2019 05:57
Last Modified:	18 Nov 2019 05:57
URI:	http://eprints.iisc.ac.in/id/eprint/63300

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