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Molecular Materials with Contrasting Optical Responses from a Single‐Pot Reaction and Fluorescence Switching in a Carbon Acid
Author(s) -
Patra A.,
Radhakrishnan T. P.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801878
Subject(s) - protonation , amine gas treating , chemistry , deprotonation , tetracyanoquinodimethane , fluorescence , photochemistry , molecule , yield (engineering) , conjugate , carbon fibers , structural isomer , organic chemistry , materials science , ion , mathematical analysis , physics , mathematics , quantum mechanics , composite number , metallurgy , composite material
Three for the price of one : The reaction of tetracyanoquinodimethane with an aromatic amine is shown to follow an unusual course leading to three products in a single pot. The product molecules form a family of materials with contrasting optical responses, in that they exhibit light emission of different colors and emission switching that is sensitively triggered by acidic/basic environments (see scheme).A wide variety of amines are known to react with 7,7,8,8‐tetracyanoquinodimethane (TCNQ) to yield push–pull diaminodicyanoquinodimethanes with a strongly zwitterionic structure and significant optical and nonlinear optical properties. A novel course of reaction is observed now with the amine 2‐methyl‐4‐chloroaniline, which leads to three well‐defined products, A – C , in a single pot. A and B are formed through the replacement of one cyano group in TCNQ by the amine; A is a carbon acid and B is its corresponding salt. C is the conventional product in which two cyano groups in TCNQ are replaced by the amine. The products are characterized structurally and spectroscopic studies reveal contrasting optical responses. A is nonfluorescent, whereas B and C show red and green emission, respectively, in the solution and solid states. The acid/conjugate‐base pair A and B can be interconverted through facile, reversible, and repeated deprotonation/protonation cycles, which are accompanied by instantaneous switching of the fluorescence. The current study illustrates an interesting case of a single‐pot reaction yielding different optical materials with attributes that can be switched through simple approaches such as protonation or tuned through modification of the push–pull characteristics.