Oxonol

Solubility Soluble in ethanol, methanol, dimethyl sulfoxide 

CA Index Name 5(4fl)-Isoxazolone, 4-[5-(5-hydroxy-3-phenyl-4-isoxazolyl)-2,4-pentadien-1 -ylidene]-3-phenyl- 

Other Names Bis[3-phenyl-5-oxoisoxazol-4-yl]penta-methineoxonol 4- [5-(5-Hydroxy-3-phenyl-4-isoxazo-lyl)-2,4-pentadienylidene]-3-phenyl-5(4/l)-isoxazolone 5(4//)-Isoxazolone, 4-[5-(5-hydroxy-3-phenyl-4-isoxa-zolyl)-2,4-pentadienylidene]-3-phenyl- 1,5-Penta-1,3-dien-l-yl-5-ylidene-bis(5-oxo-3-phenyl-4-isoxazole) OX-V Oxonol V 

Merck Index Number Not listed Chemical/Dye Class Oxonol Isoxazole Molecular Formula C23H16N2O4 Molecular Weight 384.38 Physical Form Dark green powder 

Absorption (Amax) 610 nm Emission (Amax) 639 nm Synthesis Synthetic methods  

---

The condensation of a thiazolium with an oxonol dye in a basic medium is another example of the combination of electrophilic and nucleophilic reagents (Scheme 55). With a nonopening ring, the obtained neutrodimethine cyanine is not mesosubstimted (68). 

The cleavage of thiazolopentamethine cyanine and also neocyanine results in a tetramethine neutrocyanine together with neutrodimethine cyanine (26). 2-Methylthiazolium reacts with a trimethine oxonol dye and gives a neutrotetramethine dye (Scheme 56) (26). 

The simplest PMDs include the polymethines (2), streptocyanines (3), oxonols (4), and merocyanines (5). 

Other Electrophilic Reactants. ReversibHity of the electrophilic reactions enables substituted dye derivatives to be obtained. Thus, the halogenation of cyanines, oxonoles, and merocyanines has been studied (3,65,66). Halogen atoms are mobHe in the polymethine chain, and the derivatives themselves can function as halogenation reagents. 

If the dye contains no mobile substituents ia the chain, nucleophiles attack primarily the end carbon atoms (changing of terminal residues). Streptocyanines can be hydroly2ed ia aqueous alkaline solution to form the corresponding merocyanines and then the oxonoles (71,72). These processes are reversible. Nucleophilic reactions with the methylene bases of the corresponding heterocycles result ia polymethines containing new end groups (Fig. 

Fig. 1. Chromophoric systems. Note that (A) = amidinium-ion system (a cyanine), (B) = carboxyl-ion system (an oxonol), and (C)...

A wide variety of stmetures exist in the cyanine, merocyanine, and oxonol classes of dyes. Properties that may affect toxicity vary widely also. These include solubihty, propensity to be oxidized or reduced, aggregation tendency, and diffusion through membranes. Specific acute toxicity data are Hsted in Table 2, and the LD q data vary widely with the test used. 

Dyes, polymethine used for dyes having at least one electron donor and one electron acceptor group linked by methine groups or aza analogues aUopolar cyanine, dye bases, complex cyanine, hemicyanine, merocyanine, oxonol, streptocyanine, and styryl. Supersensitization has been reported for these types—18 cites for cyanines, 3 for merocyanine, and 6 for all other polymethine types. 

Trimethine oxonols, in synthesis of tetra-methine neutrocyanines, 63... 

Ortho esters, in synthesis of symmetrical trimethine thiazolocyanines, 54 Oxazolone, for neutrocyanines, 27 Oxidation potentials, of dyes, 75 of mesosubstituted dyes, in relation with absorption, 77 of polymethine dyes, 72 Oxidoreduction, relation between sensitizers, and silver halides, 78 4-Oxo-disubstituted 2-aminoselenazoles, table of products, 262 Oxonols, nomenclature of, 26 in synthesis of dimethine neutrocyanines, 62... 

Hunig, S. t)ber die Bildung von Methinbrucken durch Formamid. II. Oxonole. 

Slow-response probes (response times greater than milliseconds) cationic car-bocyanine and rhodamine dyes and anionic oxonol dyes... 

Fig. 1 Examples of the structures of a few slow-response electric field sensitive dyes 3, 3 -dipropylthiadicarbocyanine (DiSC3(5)), tetramethylrhodamine methyl ester (TMRM), and bis-(3-propyl-5-oxoisooxazol-4-yl)pentamine oxonol (oxonol VI)...

Hydroxytriphenylmethane derivatives give rise to anionic charge-resonance systems that are isoconjugate with the corresponding amino-substituted dyes. Thus, for example, the oxonol analogue of malachite green is benzaurine (Scheme 6.33). The quinonoid neutral form (6.184), which is pale yellow, produces a violet anion (6.185) on the addition of alkali in... 

Figure 3. General structure of Hiinig s violene-cyanine hybrid. One or two of the moieties X=C-Y represent cyanines, oxonols, or merocyanines.

Als Beispiel eines Oxonols sei die Verbindung angefiihrt, die sich bei Ver-knupfung zweicr N-Athylrhodaninreste durch eine Kette von drei Methingruppen ergibt H H H... 

The main classes of dyes nsed as potentiometric probes are cationic or zwitterionic styryl dyes, cationic carbocyanines and rhodamines, anionic oxonols and hybrid oxonols and merocyanines. The particular class of dye determines factors snch as accnmnlation in cells, response mechanism and toxicity. 

---