Acridine absorption

Like acridine, phenanthridine and dimethyl acetylenedicarboxylate in methanol give a high yield of 1 1 1 molar adduct. Ultraviolet absorption spectrum comparisons show that this is best formulated as 9,10-dihydro-9-methoxy-10- (tran.s-l,2-dimethoxycarbonylvinyl) phenanthridine (142) rather than the corresponding phenanthridinium methoxide (143) under neutral conditions acidification changes the spectrum to that characteristic of the phenanthridinium cation. Crystallization of the adduct (142) from methanol containing 5-15% of water gave the betaine [(144) the positions of the ester and carboxylate groups have not been established], while in the presence... 

Anthracene has also been used as an acceptor (Fig. 10). In solution, 26 emits a single fluorescence band that is somewhat structured in nonpolar solvents and becomes broad and structureless with increasing polarity [58]. The strongly hindered molecule 27 also exhibits a similar behavior, but its absorption spectrum is better structured [59]. The rate of formation of a charge transfer state is higher for 27 than for 26. Based on this observation, it appears that the twist around the anthryl-phenyl C-C bond plays a significant role in the fluorescence profile of the probes [60]. Acridines, such as 28, behave similarly to anthracene except that acridine is a better electron acceptor [61]. 

In some heterocyclic compounds such as acridine, the n-n absorption band is difficult to distinguish from the much more intense n-n absorption bands. 

Zanker, V. Quantitative Absorptions- und Emissionsmessungen am Acridin-orangekation bei Normal- und Tieftemperatur im organischen L6sungsmittel und ihr Beitrag zur Deutung des metachromatischen Fluoreszenzproblems. Z. physik. Chem. 200, 250 (1952). 

Isolation of Oxidation Products. After oxygen absorption had ceased, or reached the desired value, the oxidates were poured into water. In many cases the reaction product could be removed by filtration in high yield. In this manner xanthone (m.p. 172-174°C.), was isolated from oxidations of xanthene or xanthen-9-ol thioxanthone (m.p. 208-210°C.), from thioxanthene acridine (m.p. 107-109°C.), from acridan anthracene (m.p. 216-217°C.), from 9,10-dihydroanthracene phenanthrene (m.p. 95-99°C.), from 9,10-dihydrophenanthrene pyrene (m.p. 151-152.5°C.) (recrystallized from benzene) from 1,2-dihydropyrene and 4-phenan-throic acid (m.p. 169-171 °C.) (recrystallized from ethanol) by chloroform extraction of the hydrolyzed and acidified oxidate of 4,5-methyl-enephenanthrene. 

Figure 15 (1) UV absorption spectra of anthracene, phenazine and acridine in ethanol. (2) UV absorption spectra of anthracene, and 1- and 2-azaanthracene in ethanol (Reproduced with permission from (51JCS3199))...

Heavy atom enhancement of intersystem crossing has been used to determine the mechanism of acridine photoreduction in ethanol.115 It was found that addition of sodium iodide decreased the fluorescence intensity and the rate of disappearance of acridine to the same extent, confirming that the singlet state is responsible for photoreduction. From the increase in triplet state absorption upon addition of iodide it was found that Of for acridine was 0.76. Thus the short singlet lifetime (0.8 nsec) of acridine is due to rapid inter-system crossing to unreactive triplet states. 

Table III summarizes experimental and theoretical data on the first three absorption bands (Lb, La, Bb) in the spectra of pyridine, quinoline, isoquinoline, acridine, and their benzo and dibenzo derivatives.

Complexes between chiral polymers having ionizable groups, and achiral small molecules become, under certain conditions, optically active for the absorption regions of the achiral small molecules. Dyes such as acridine orange and methyl orange have been used as achiral species, since they are in rapport with biopolymers through ionic coupling. This phenomenon has been applied to the detection of the helix chirality in poly-a-amino acids, polynucleotides, or polysaccharides when instrumental limitations prevent direct detection of the helices. 

Fig. 1 A. The absorption (-a-) and fluorescence (-o-) spectra of 9AAHH (5 x 10 3 M) in PVA film. The inset shows the molecular structure of 9-amino acridine. Panel (B) gives the fluorescence spectra of 9AAHH (5 x1c4 M) in spherical beads of PMMA with radius (a) 9 pm, (b) 3 pm and (c) 1.5 pm.

Classes Of Sensitization, a. Photoreducible Dye Sensitization. In 1954 Oster (7) reported the first documentation of a dye-sensitized photoredox system. During the course of his work, Oster identified several classes of effective dyes, termed by him "photoreducible." These included examples of the classes of acridine, xanthine, and thiazine dyes. Figure 3 illustrates an example of each class, chosen in such a manner that the entire visible spectrum is covered by their absorption spectra. In Oster s work, identification of suitable activators (reduc-tants) to use in conjunction with the dyes was empirically determined. 

In addition, the UV spectra have been explored more thoroughly. In two papers, Tatibouet and Demeunynck reported the study of acridine derivatives. First they noted that the UV-visible absorption of the acridine chromophore in 16a (NIH-MEW, Scheme 21) exhibits large variations as compared to the parent acridine (97BSF495). As was commented in Section IV.A.2, these authors recorded the UV-visible spectrum of (+)-16b in the presence of increasing concentrations of calf thymus DNA, experiments used to demonstrate that 16b interacts with DNA (99CC161). As reported in Section IV.A.4, the UV-visible titration of 38b with tetraamines confirmed the formation of 2 1 and 1 1 complexes (98CC11). 

Using pulse radiolysis, Moorthy and Hayon have studied radicals from pyrazine, pyrimidine, pyridazine, quinoxaline, phthalazine, and acridine.219 Electronic absorption characteristics and kinetic data were reported for the hydrodiazinyl neutral radicals, among others, and the pK values for their protonation to (V,JV -dihydrodiaziniumyl radicals were given. The neutral... 

Subsequent investigations have reinforced earlier evidence for the wide occurrence of hydrogen bonding of azines. Bonding of all the monocyclic azines,many substituted azines, and azinones with water, alcohols, and dilute acids has been studied by electronic absorption spectra and the variation of the effect with changes in the position of the substituent noted. Quinolines and acridines with chloroform, alcohols, phenols, carboxylic acids, aniline, and pyrrole show the influence of hydrogen bonding on... 

The film remaining after extensive bleaching (where the bleaching curves of Figure 5 are flat) still contains some acridine as judged by the weak blue fluorescence, but the absorption spectrum shows only a small bump near 250nm on top of an otherwise featureless curve. 

We cannot say what the relative mix of photochemical and thermal effects is as yet. The literature suggests that significant photochemical reactions should occur due to 248nm irradiation of acridine (25,26), but these are not the massive bond-breaking type that characterize 193nm photoablation(16). The fluorescence yield of acridine in PMMA is known to be about 0.2 (26) so considerable heat is produced by the absorption of short pulses in the 100 mJ/cm2 range an estimate based on an approximate heat capacity formula (27) is about 300 0. The excited state properties of acridine in PMMA show a pronounced temperature dependence (26). It seems likely that the bleaching arises from a combination of photochemical destruction of the acridine chromophore and polymer ablation. 

The presence of MEF, MEP and Metal-Enhanced superoxide anion radical generation in the same system seems surprising at first, as these processes are effectively competitive and ultimately provide a route for deactivation of electronic excited states. As recently shown by the authors, simultaneous photophysical mechanisms can be present within the same system when enhanced absorption effects of the fluorophore near to silver are present (i.e. an enhanced excitation rate). In this case, enhanced absorption of Acridine near-to the plasmon resonant particles facilitates MEF, MEP, ME Oa and also Metal-Enhanced superoxide generation simultaneously within the same system. Aaidine showed an enhanced absorption spectra near-to silver, similar to other probes reported by the authors, in essence acridine absorbs more light. ... 

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