Matrix dependence of blue light emission from a novel NH 2 ‐functionalized dicyanoquinodimethane derivative

• Published in: Journal of physical organic chemistry Vol. 19; no. 3; pp. 206 - 213
• Main Authors: Szablewski, Marek, Bloor, David, Kagawa, Yasuyuki, Mosurkal, Ravi, Cole, Jacqueline M., Clark, Stewart J., Cross, Graham H., Pålsson, Lars‐Olof
• Format: Journal Article
• Language: English
• Published: 01.03.2006
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/poc.1020

The reactions of primary and secondary amines with (cyclohexa‐2,5‐diene‐1,4‐diylidene)‐dimalononitrile (TCNQ) lead to mono‐ and disubstituted dicyanoquinodimethane derivatives and fluorescence emission has been observed for several of these compounds. We report the luminescence properties, synthesis and crystal structure of the novel dicyanoquinodimethane derivative 2‐{4‐[amino‐(2,6‐dimethyl‐morpholin‐4‐yl)‐methylene]‐cyclohexa‐2,5‐ dienylidene}‐malononitrile (Ammor), a unique example of an asymmetric dicyanoquinodimethane derivative in which one of the nitrile groups has been replaced with an NH 2 moiety, which provides a reactive centre for potential further substitution or tethering to larger molecules or polymers. The luminescence properties of the title compound were investigated in a variety of environments, including alcohol solutions at room temperature and a glass‐forming solvent at low temperature. The fluorescence quantum yields and Stokes' shifts of the blue emission were found to be very sensitive to the matrix. The crystal structure of the subject compound was determined, revealing that the molecules are non‐planar in the ground state. The environmentally sensitive emission is discussed in terms of the conformational change during photoexcitation and the constraint imposed on this by the matrix. This behaviour is also compared with that of other related amino‐functionalized dicyanoquinodimethane derivatives. Copyright © 2006 John Wiley & Sons, Ltd.