Xanthene

About: Xanthene is a research topic. Over the lifetime, 2132 publications have been published within this topic receiving 34803 citations. The topic is also known as: Xanthene & dibenzo[a,e]pyran.

A new Cu2+-induced color reaction of a rhodamine derivative N-(3-carboxy)acryloyl rhodamine B hydrazide

Abstract: A new rhodamine derivative, N-(3-carboxy)acryloyl rhodamine B hydrazide (CARB), has been synthesized, and its unusual spectroscopic reaction with Cu2+ has been investigated. The derivative exhibits a rapid and reversible non-fluorescent absorption upon coordination to Cu2+, which is a rather unusual phenomenon for rhodamine B derivatives. Stoichiometric measurements using the Job’s method and the molar ratio method reveal that one CARB molecule combines two Cu2+ ions, and the two Cu2+ ions play different roles: one opens the spirocyclic structure and the other quenches the fluorescence of the xanthene moiety. This reaction mechanism is supported by a comparative study on the model compound N-acryloyl rhodamine B hydrazide as well as by the density functional theory calculations. Furthermore, the absorption response of CARB is highly selective for Cu2+ over other common ions, which implies that CARB may be used as a colorimetric probe for the rapid visual detection of Cu2+.

Quenching of chemiexcited triplet acetone by biologically important compounds in aqueous medium

Abstract: — Thermolysis of tetramethyl-l,2-dioxetane is a convenient source of triplet acetone, which can be monitored in aerated solutions by the sensitized fluorescence of 9,10-dibromoanthracene. We have investigated the quenching of chemiexcited triplet acetone in air-equilibrated aqueous solutions containing the 9,10-dibromoanthracene-2-sulfonate ion by five classes of compounds: indoles, tyrosine derivatives, quinones, riboflavin, and xanthene dyes. Quenching rates for indoles, tyrosine and its 3,5-dihalogenoderivatives, and xanthene dyes (kq= 108-109M-1 s-1) are considerably smaller than the diffusion controlled rate, whereas those for quenchers with high electroaffinities, such as quinones (IP = 10–11 eV), approach the diffusion controlled rate (kq= 1010 M-1 s-1). Energy transfer for riboflavin probably occurs by a triplet-singlet Forster type process. A comparison of the present data with previous studies of quenching of enzymically generated triplet acetone (isobutanal/O2/horseradish peroxidase) by the same classes of quenchers (except riboflavin) reveals that, independent of the nature of the quencher and the deactivation mechanism, the Stern-Volmer quenching constants (kq t0) are systematically about one order of magnitude higher in the enzymatic system. The difference is attributed to a longer lifetime of triplet acetone in the latter case, “protected” in an enzyme cavity against collisions with dissolved oxygen.

Inhibition of vesicular glutamate uptake by Rose Bengal-related compounds: structure-activity relationship.

Abstract: Synaptic vesicular accumulation of glutamate is a vital initial step in glutamate transmission. We have previously shown that Rose Bengal, a polyhalogenated fluorescein analog, is a potent inhibitor of glutamate uptake into synaptic vesicles. Here, we report the structural features of Rose Bengal required for this inhibition. Various Rose Bengal-related compounds, with systematic structural variations, were tested. Results indicate that the four iodo groups and the phenyl group attached to the xanthene moiety are critical for potent inhibitory activity. Replacement of these groups with two iodo groups and an alkyl group, respectively, results in substantial reduction in potency. Of further interest in creating high potency is the critical nature of the oxygen atom which links the two benzene rings of xanthene. Thus, the phenyl group and multiple iodo groups, as well as the bridging oxygen of xanthene, are crucial elements of Rose Bengal required for its potent inhibitory action.