The paper on the synthesis of several dyes by James V. McCullagh and Kelly A. Daggett (1) provides us with the JCE Featured Molecules for this month. The authors mention various applications of these dyes, ranging from commercial dyeing to techniques for determining the course of complex biochemical processes. One of the reaction products, rhodamine B, is a member of a family of molecules that are widely used as tunable laser dyes. In this application, the rhodamines are most commonly encountered in a cationic form, rather than in the neutral form shown in the paper.
In the cations, the carboxyl group is no longer part of a ring system. Several different members of the rhodamine family are included in the molecule collection because substituents have a marked effect on the effective lasing range of a given dye. Additionally, the solvent and the excitation source also influence the lasing range (2). Students can learn more about the relationship between structure, absorption and emission properties, and lasing ranges of various dyes by consulting ref 2 and from PhotochemCAD, Jonathan Lindsey’s free application (3).
fluorescein
rhodamine
Students can examine the structures of molecular dyes along with other molecules in the collection, at the JCE Digital Library Web site.
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