Issue 3, 2017

Enhanced intersystem crossing in core-twisted aromatics


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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Article information

Article type
Edge Article
21 Nov 2016
19 Dec 2016
First published
20 Dec 2016
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 1776-1782

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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