Acridine complexes

Adenylyl-3, 5 -uridine amino acridine complex 15 H20 X All water oxygens located Choice of two hydrogenbonding schemes [825]... 

Optical studies of DNA-acridine complexes orientated by flow have shown that the planar dye molecule has a definite orientation, and is parallel to the plane of the bases. 

In complex cases, the prefixes amino- and imino- may be changed to ammonio- and iminio- and are followed by the name of the molecule representing the most complex group attached to this nitrogen atom and are preceded by the names of the other radicals attached to this nitrogen. Finally the name of the anion is added separately. For example, the name might be 1-trimethylammonio-acridine chloride or 1-acridinyltrimethylammonium chloride. 

Acridine-9-carbaldehyde (24%) is one of several products formed from the oxidation of 5//-dibenz[A/]azepine with tert-butyl hypochlorite in dichloromethane at — 70 C.229 The reaction is even more complex in the presence of silver(I) trifluoroacetate, and an analysis of the reaction mixture by GC-MS techniques reveals the presence of eleven products, the major ones being acridine (37%), an unidentified 5//-dibenz[/ ,/]azepinecarbaldehyde (23%) and acridine-9-carbaldehyde (9 %). 

A highly sensitive method for the determination of anionic surfactants, particularly sodium dodecyl sulfate, has been described [275]. The method is based on the formation of fluorescent ionic complexes of the anionic surfactant with acridine red and acridine yellow. The complexes are extracted with dichloro-... 

For some strong electron donor molecules the polarization of the X2 molecule may be sufficient that the X atom not complexed to B serves as an electron donor to a second X2 molecule, i.e., the dihalogen is amphoteric , acting as a Lewis acid to Lewis base B, and as a Lewis base to the second X2 molecule, acting as a Lewis acid. For a 1 1 B X2 X2 ratio, an extended adduct (Fig. 1, mode AA) is formed, as illustrated in Fig. 2c for 4,5-bis(bromomethyl)-l,3-dithiole-2-thione-diiodine diiodine (HAMCAA) [58]. This is often referred to as an extended spoke structure. If the second X2 acts as Lewis acid acceptor at either end of the molecule, then a bridged amphoteric adduct (Fig. 1, mode BA) is formed, as illustrated for (acridine I2)2 I2 (QARGIZ) [31] in Fig. 2d. 

Second only to sulfur-based systems, nitrogen complexes are relatively well represented in the structural literature with 41 complexes reported. Of these, 25 are with I2 as the electron acceptor, 11 are with the interhalogen IC1, three are with Br2, and two are with IBr. As expected, in every case the halogen bond forms between the nitrogen and the softest halogen atom, i.e., iodine, in all of the complexes except those with dibromine. Most N I2 complexes, and all N Br2, N IBr, and N IC1 complexes are simple adducts, mode A. Exceptions for the diiodine complexes include bridging mode (B) observed for diazines, such as pyrazine [86], tetramethylpyrazine [86], phenazine, and quinoxaline [87], and for 9-chloroacridine [89] and the 1 1 complex of diiodine with hexamethylenetetramine [144] and amphoteric bridging mode (BA) observed for 2,2 -bipyridine [85], acridine [89], 9-chloroacridine [89], and 2,3,5,6-tetra-2/-pyridylpyrazine [91]. The occurrence of both B and BA complexes with 9-chloroacridine, and of B and A complexes and an... 

Amine complexes stabilized with phosphine ligands of the type [AuL(PR3)]+ have been obtained for L = bipy,2310 phen,2310,231 quinoline,23 1 acridine,2311 benzo[h]quinoline,2311 naphthyr-idine (388)2311 2,2 -biquinoline,2311 di-2-pyridyl-ketone,2311 di-2-pyridylamine,2311 2-(2-pyridyl)-benzimidazole, 2311 ferrocenylpyridine, 2-nitroaniline,2312 4-methoxyaniline,2312 NHPh2, 2 NHEt2,2312 NMe3,2312 quinuclidine,2313 NEt3,2314 2-aminothiazoline,2315 histidine,2316... 

The aromatic spacer group of the model receptors prevent the formation of intramolecular hydrogen bonds between the opposing carboxyls yet these functions are ideally positioned for intermolecular hydrogen bonds of the sort indicated in 32. The acridine derivatives do indeed form stoichiometric complexes with oxalic, malonic (and C-substituted malonic acids) as well as maleic and phthalic acids, Fumaric, succinic or glutaric acids did not form such complexes. Though protonation appears to be a necessary element in the recognition of these diacids, the receptor has more to... 

The protonated acridine must therefore provide special stabilization to the conjugate bases of small dicarboxylic acids. Evidence for the nature of this special stabilization was provided by some of the receptors which are not constrained to convergent conformations. Figure 2 shows the ambient temperature spectrum of 33 and its simple salts such as the picrate. At low temperature, complex spectra are observed as interconversion between the three possible conformations become slow. In the presence of appropriate diacids such as oxalic acid the spectra are sharpened and are no longer temperature dependent22c). 

In polar solvents, the structure of the acridine 13 involves some zwitterionic character 13 a [Eq. (7)] and the interior of the cleft becomes an intensely polar microenvironment. On the periphery of the molecule a heavy lipophilic coating is provided by the hydrocarbon skeleton and methyl groups. A third domain, the large, flat aromatic surface is exposed by the acridine spacer unit. This unusual combination of ionic, hydrophobic and stacking opportunities endows these molecules with the ability to interact with the zwitterionic forms of amino acids which exist at neutral pH 24). For example, the acridine diacids can extract zwitterionic phenylalanine from water into chloroform, andNMR evidence indicates the formation of 2 1 complexes 39 such as were previously described for other P-phenyl-ethylammonium salts. Similar behavior is seen with tryptophan 40 and tyrosine methyl ether 41. The structures lacking well-placed aromatics such as leucine or methionine are not extracted to measureable degrees under these conditions. 

Another way in which Pt could bind to DNA is through the formation of intercalation compounds. The parallel here is with the hydrocarbon carcinogens and the nucleic acid stains, the acridines. It has been shown that metal chelates will form this same type of jt-complex. For example, palladium oxinate will form exactly the same type of -complexes as anthracene (88). 

Several complexes that involve intercalation of an acridine in a portion of a nucleic acid have been studied by X-ray crystallographic techniques. These include complexes of dinucleoside phosphates with ethidium bromide, 9-aminoacridine, acridine orange, proflavine and ellipticine (65-69). A representation of the geometry of an intercalated proflavine molecule is illustrated in Figure 6 (b) this is a view of the crystal structure of proflavine intercalated in a dinucleoside phosphate, cytidylyl- -S ) guano-sine (CpG) (70, TV). For comparison an example of the situation before such intercalation is also illustrated in Figure 6 (a) by three adjacent base pairs found in the crystal structure of a polynucleotide (72, 73). In this latter structure the vertical distance (parallel to the helix axis) between the bases is approximately... 

E. M. Duffy and W. L. Jorgensen, Structure and binding complexes of Rebek s acridine... 

There are many interesting derivatives of quinoline and acridine obtained by substitution. In particular, 8-hydroxyquinoline (oxine) is the second complexing agent in importance after EDTA. Sulfonation in position 5 leads to a compound which is soluble in water and that exhibits outstanding fluorogenic properties (i.e. fluorescence enhancement) on complexation with metal ions (e.g. aluminum). 

The fluorescence spectrum of the tris-acridine cryptand A-13 shows the characteristic monomer and excimer bands. Upon complexation with various organic anions (carboxylates, sulfonates, phosphates), the monomer band increases at the expense of the excimer band. The stability of the complexes depends on the contribution of the electrostatic and hydrophobic forces and on the structural complementarity. Stability constants of the complexes ranging from 103 to 107 have been measured. In particular, A-13 binds tightly to mono- and oligonucleotides, and it can discriminate by its optical response between a pyridimic and a purinic sequence. 

Although chlorination, bromination and iodination of thiophenes by polyhalide salts require forcing conditions with the addition of zinc chloride [52], halogenation of acridine and acridone has been recorded to yield both 3-halo and 3,7-dihalo derivatives under relatively mild reaction conditions [53], However, whereas chloro-, bromo- and iodo-compounds are readily obtained from acridone, acridine only forms the bromo derivatives, as it produces stable complexes with the dichloroiodate and tetrachloroiodate salts [53]. 

This last path has experimental support in the case of the reaction with acridine in the isolation of 9-acyl-9,10-dihydro derivatives. This behavior can be correlated with the fact that the protonation of the heterocyclic nitrogen and the presence of an electron-withdrawing group (R-CO) causes a relatively high ionization potential of the o-complex... 

---