Solvatochromic, spectroscopic and DFT studies of a novel synthesized dye: l-(4-Dimethylaminophenyl)-2-(5H-phenanthridine-6-ylidene)-ethanone (6-KMPT).

A novel solvatochromic l-(4-dimethylaminophenyl)-2-(5H-phenanthridine-6-ylidene)-ethanone (6-KMPT) dye was synthesized and characterized by means of NMR, IR, mass spectroscopies. Also, it was studied using UV-vis and fluorescence spectroscopic methods in a broad range of solvents. UV-vis results showed that increasing 6-KMPT concentration dose not cause molecular aggregation in chloroform. Varying the temperature in the range from 25 to 55 degrees C dose not have a significant effect on the characteristics bands of the molecule. However, in the presence of surfactant SDS the UV-vis spectrum undergoes drastic alteration. This phenomenon is related to the removal of hydrogen atom from nitrogen atom of phenanthridine moiety. Fluorescence spectroscopic results showed that 6-KMPT has an appreciable fluorescence quantum yield. The effect of excitation wavelength, concentration of 6-KMPT, concentration of oxygen and surfactants (SDS, C(16)TAB, CPC, Brij-35) were studied. Further results showed that the fluorescent behavior of 6-KMPT can be attributed to planarity induced by intramolecular hydrogen bonding which can in turn be destroyed by anionic surfactant SDS. Results showed that oxygen and SDS can be operate as fluorescence quencher compounds for 6-KMPT and Stern-Volmer plot showed a straight line. Fluorescence polarization and anisotropy of 6-KMPT in chloroform strongly depend on concentration. The 6-KMPT exhibits solvent-induced spectral band shifts. By using Lippert equation, the change of dipole moment of 6-KMPT molecule upon excitation was estimated as 6.39 D. Furthermore, absorption, fluorescence emission, Stokes shift values and fluorescence quantum yield (Phi(F)) of 6-KMPT in different solvents of polarity were determined. Maximum Phi(F) value of 0.372 for 6-KMPT molecule was found in ethanol solvent with a Stokes shift of 2446.8 cm(-1). The results of DFT calculations showed that tautomer 2c (enol) energetically is more stable than tautomer 2b (keto) in gas phase whereas it was vice versa in CHCl(3).

Modeling the formation and reactions of benzene metabolites.

One or more of the muconaldehyde isomers is a putative product of benzene metabolism. As muconaldehydes are highly reactive dienals and potentially mutagenic they might be relevant to the carcinogenicity of benzene. Muconaldehydes may be derived through the action of a cytochrome P450 mono-oxygenase on benzene oxide-oxepin, which are established metabolites of benzene. Oxidation of benzene oxide-oxepin either by the one-electron oxidant cerium(IV) ammonium nitrate (CAN) or by iron(III) tris(1,10-phenanthroline) hexafluorophosphate in acetone at -78 degrees C or acetonitrile at -40 degrees C gave (E,Z)-muconaldehyde, which was a single diastereoisomer according to analysis by (1)H NMR spectroscopy. Reaction of toluene-1,2-oxide/2-methyloxepin with CAN gave (2E,4Z)-6-oxo-hepta-2,4-dienal. Similarly, the action of CAN on 1,6-dimethylbenzene oxide-2,7-dimethyloxepin gave (3Z,5E)-octa-3,5-diene-2,7-dione. In vivo, benzene oxide-oxepin could suffer one-electron oxidation by cytochrome P450 mono-oxygenase giving (E,Z)-muconaldehyde. The observations presented may be relevant to the toxicology of benzene oxide-oxepin and other arene oxide-oxepins as we have previously shown that (E,Z)-muconaldehyde, analogously to (Z,Z)-muconaldehyde, affords pyrrole adducts with the exocyclic amino groups of the DNA bases adenine and guanine. Independent of their possible toxicological significance, the experiments described provide preparatively useful routes to (E,Z)-muconaldehyde and its congeners. Methods are also described for the trapping and analysis of reactive benzene metabolites, e.g. using the Diels-Alder reaction with the dienophile 4-phenyl-1,2,4-triazoline-3,5-dione to trap arene oxides and with the diene 1,3-diphenylisobenzofuran to trap enals.