A variety of solid-state fluorescence properties of pyrazine dyes depending on terminal substituents

Abstract

The optical properties of 2,5-diamino-3,6-dicyanopyrazine derivatives bearing singly methyl-or halogen-substituted benzyl groups were studied in both solution and crystalline phases. In solution, all derivatives showed similar absorption and fluorescence properties, since the electronic state of their fluorophore was not altered by substituents attached to the benzyl groups. In contrast, crystalline compounds exhibited a variety of fluorescence colours (yellow, orange, and red), since their solid-state absorption and fluorescence properties were correlated with a change in the electron-donating ability of amino groups due to crystallisation. The absolute fluorescence quantum yields of crystalline dyes (0.14−0.91) showed broad variability, depending on the nature and positions of terminal substituents.

Synthesis, optical and electrochemical properties of a series of push-pull dyes based on the 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) acceptor

“…Therefore, a perfect control of the absorption maxima of the dye that will be used as the photosensitizer is a prerequisite to efficiently initiate the polymerization process and generate reactive species such as radicals or cations. [31][32][33] In these different research fields, many electron acceptors have been studied over the years as exemplified by malononitrile 1 [34], substituted tricyanopropenes 2 [35], 1,1,3-tricyano-2-substituted propenes 3 [36], dicyanovinyl-thiophen-5-ylidenes 4 [37], tetranitrofluorene 5 [38], pyran derivatives 6 and 7 [39,40], dicyanoimidazoles 8 [41], pyrazines 9 [42], hydantions and rhodanines 10 [43], (thio)barbituric derivatives 11 [44], isoxazolones 12 [45], Meldrum derivatives 13 [46], indanedione derivatives 14 [47], 15 [48,49] [51] and pyridinium 18. [52] Among all electron acceptors, 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) has been extensively studied due to the ability to design push-pull dyes with ICT bands extending from the visible range to the near infrared region.…”

Recent advances on push–pull organic dyes as visible light photoinitiators of polymerization

“…C. Pigot et al European Polymer Journal xxx (xxxx) xxx-xxx A5, [130] methyl-containing tricyanofurans A6, [131] substituted tricyanopropenes A7, [132] pyran derivatives A8 and A9, [133,134] 1,1,3-tricyano-2-substituted propenes A10, [135] isoxazolones A11, [136] hydantions and rhodanines A12, [137] pyrazines A13, [138] dicyanoimidazoles A14, [139] [141] dicyanovinyl-thiophen-5-ylidenes A17 [142] and 9-methylene-2,4,5,7-tetranitro-9H-fluorene A18 [143] can be mentioned. Another appealing feature of push-pull dyes is the possibility to design these structures by using a convergent approach.…”

Comparison of semi‐empirical and density functional approaches for the colour and constitution of anthraquinone dyes using X‐ray structure

“…10,11 On the other hand, semi-empirical PM5 random phase approximation (PM5/RPA) and Zerner's intermediate neglect of differential overlap CI (ZINDO/CI) have already been applied for predicting molecular structures, the reaction mechanism and electronic properties. [12][13][14][15][16] Anthraquinone (AQ) dyes comprise the next most important dye class after azo dyes. Anthraquinones are typically present in the most common red natural colourants used extensively in textile dyeing, from many thousands of years ago until the late nineteenth century.…”