Synlett 2016; 27(11): 1613-1617
DOI: 10.1055/s-0035-1561447
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© Georg Thieme Verlag Stuttgart · New York

Biradicaloid with a Twist: Lowering the Singlet–Triplet Gap

Prince Ravat
,
Tomáš Šolomek
,
Peter Ribar
,
Michal Juríček*
Further Information

Publication History

Received: 25 February 2016

Accepted after revision: 21 March 2016

Publication Date:
27 April 2016 (online)

Dedicated to Miroslav Kozák

Abstract

Fusing two phenalenyl units such that a Kekulé structure is obtained leads to ‘biradicaloid’ systems, which typically display low ­singlet–triplet (S–T) energy gaps. The value of the S–T gap in biradicaloids can be lowered by extending the conjugated system for an additional fused ring(s). Recently, we have described an alternative approach to decrease the S–T gap with the aid of through-space interactions that arise in helically twisted biradicaloids. Using [5]helicene-based biradicaloid ‘cethrene’ as an illustrative example, we have shown that the value of its S–T gap is substantially decreased when compared to that of its planar isomer heptazethrene, on account of the helical twist, inducing crucial intramolecular interactions.

 
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