Spectral properties of the tumor-localizing dimer/oligomer fraction of HPD and of several diporphyrin ethers were assessed by fluorescence and absorbance spectroscopy in different solvents and after accumulation by leukemia L1210 cells in vitro. Joining 2 porphyrins by an ether linkage caused a blue shift in the Soret bands of the dimers, but not monomers, when the dielectric constant of the solvent was lowered. The presence of ether linkages was assciated with enhanced fluorescence at 630-640 nm and decreased fluorescence lifetimes and fluorescence yields. The joining of two mesoporphyrin or protoporphyrin mole cules by an ether linkage reduced dye accumulation by L1210 cells, but makedly promoted uptake of the hematoporphyrin analog.
Single-and two-color multiphoton ionization of anthracene have been compared in n- alkane solvents. The simultaneous action of 10-ns laser lights at 355 (UV) and 1064 nm (IR) gave a substantially larger time-integrated photocurrent signal (thus, the escape probability of a geminate cation-electron pair based on the Onsager model) as compared with that obtained when the UV light acted alone. It is suggested that the IR light acts through the geminate cation-electron pair to give its longer thermalization distance. For a solvent with higher electron mobility, escape probabilities for both photoionization methods tended to belarger but the relative increase in the escape probability by the additional action of the IR light tended to be smaller.