Health & Environmental Research Online (HERO)


Print Feedback Export to File
7638173 
Journal Article 
Heli(aza)cene: A Helical Molecular Tweezer with Tunable Intra- and Intermolecular Charge Transfer 
Kumar, R; Semwal, S; Choudhury, J; Srivastava, A; , 
2017 
Yes 
Chemistry: A European Journal
ISSN: 0947-6539
EISSN: 1521-3765 
WILEY-V C H VERLAG GMBH 
WEINHEIM 
15012-15016 
English 
28881051 
WOS:000413768900006 
Non-planar fluorophores offer unique avenues of intra- and intermolecular energy transfer not available in their planar counterparts. We have rationally designed a molecular tweezer based on the pyridine-2,6-dicarboxamide framework having two structurally similar arms with extended π-surface. We termed this molecular tweezer as Heli(aza)cene (HAC) due to its spontaneous adoption of helical conformation stabilized by the amide and imine moieties present in it. In the helical conformation, the two arms of HAC are twisted unequally. This asymmetry confers dissimilar electronic character to the two arms and results in intramolecular charge transfer interactions in HAC. Homochiral stacking of the P- and the M- helices in crystal, and profound redshifting of the emission at higher concentrations of HAC was attributed to intermolecular charge-transfer interactions in aggregated/crystal state. Exposure of HAC, in solution as well as in the solid state, to Lewis/Brønsted acids results in rapid and vibrant color changes. This is the first example of a π-layered helical molecule exhibiting tunable intra-/intermolecular charge-transfer characteristics.