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Issue 3, 2017
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Enhanced intersystem crossing in core-twisted aromatics

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Abstract

We describe the design, bottom-up synthesis and X-ray single crystal structure of systematically twisted aromatics 1c and 2d for efficient intersystem crossing. Steric congestion at the cove region creates a nonplanar geometry that induces a significant yield of triplet excited states in the electron-poor core-twisted aromatics 1c and 2d. A systematic increase in the number of twisted regions in 1c and 2d results in a concomitant enhancement in the rate and yield of intersystem crossing, monitored using femtosecond and nanosecond transient absorption spectroscopy. Time-resolved absorption spectroscopic measurements display enhanced triplet quantum yields (ΦT = 10 ± 1% for 1c and ΦT = 30 ± 2% for 2d) in the twisted aromatics when compared to a negligible ΦT (<1%) in the planar analog 3c. Twist-induced spin–orbit coupling via activated out-of-plane C–H/C[double bond, length as m-dash]C vibrations can facilitate the formation of triplet excited states in twisted aromatics 1c and 2d, in contrast to the negligible intersystem crossing in the planar analog 3c. The ease of synthesis, high solubility, access to triplet excited states and strong electron affinity make such imide functionalized core-twisted aromatics desirable materials for organic electronics such as solar cells.

Graphical abstract: Enhanced intersystem crossing in core-twisted aromatics

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Publication details

The article was received on 21 Nov 2016, accepted on 19 Dec 2016 and first published on 20 Dec 2016


Article type: Edge Article
DOI: 10.1039/C6SC05126J
Citation: Chem. Sci., 2017,8, 1776-1782
  • Open access: Creative Commons BY license
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    Enhanced intersystem crossing in core-twisted aromatics

    K. Nagarajan, A. R. Mallia, K. Muraleedharan and M. Hariharan, Chem. Sci., 2017, 8, 1776
    DOI: 10.1039/C6SC05126J

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