The model compounds, 8-methoxypsoralen-CH2O(CH2)n-adenine (MOPCH2OCnAd, n=2, 3, 5, 6, 8, and 10) in which 5 position of 8-methoxypsoralen (8-MOP) is linked by various lengths of polymethylene bridge to N 9 of adenine. UV absorption spectra are identical with the sum of MOPCH2OC3 and adenine absorption spectra. Solvent effects on the UV absorption and fluorescence emission spectra indicate that the lowest excited singlet state is the (π→π*) state. The spectral characteristics of the fluorescence of MOPCH2OCnAd are strongly dependent upon the nature of the solvents. The fluorescence emission spectra in aprotic solvents are broad and structureless due to the excimer formation through the folded conformation accelerated by hydrophobic π-π stacking interaction. Increasing polarity of the protic solvents leads to higher population of unfolded conformation stabilized through favorable solvation and H-bonding, and consequently to an increase in the fluorescence intensity, fluorescence lifetime, and a shift of fluorescence maximum to longer wavelengths. The decay characteristics of the fluorescence in polar protic solvents shows two exponential decays with the lifetimes of 0.6-0.8 and 1.6-1.9 ns in 5% ethanol/water, while MOPCH2OC3 shows 0.5 and 1.7 ns fluorescence lifetimes. The long-lived component of fluorescence can be attributed to the relaxed species (i.e., the species for which the solvent reorientation (or relaxation) has occurred), while the short-lived components can be associated with the unrelaxed, or only partially relaxed, species.

In this research, the preparation processes for making a series of ω-mercapto alkylamine 1 and ω-mercapto alkanoic acid 2 useful for studying of the self-assembled monolayer(SAM) are described. The preparation methods of the first goal materials, ω-mercapto alkylamines 1 were carried out as follows: First, ω-phthalimide alkanol 3 was synthesized from commercially available potassium phthalimide derivatives and ω-bromoalkanol in DMF at 80 o C via substitution reaction. After refluxing ω-phthalimide alkanol 3 with hydrazine hydrate in ethanol followed by treating with c-HCl, ω-aminoalkanol 4 was obtained in 76~98% yield, accompanied with side-product 5. Bromination of hydroxyl moiety of ω-aminoalkanol 4 using aqueous hydrobromic acid furnished ω-bromoamine 6 in 34~97% yields. Substitution reaction 6 with thiourea in 95% ethanol gave ω-aminoalkanthiuronium 7, which was treated with aqueous † To whom correspondence should be addressed.