SYNTHESIS OF A SERIES OF OCTABUTOXYPHTHALOCYANINES AND OCTABUTOXYBENZOPHTHALOCYANINES AND PHOTOPHYSICAL PROPERTIES OF 2 MEMBERS OF THE SERIES

We have developed a new route to silicon-centered phthalocyanines and phthalocyanine-like compounds that is robust and flexible, and of cons iderable potential usefulness. This route entails insertion of silicon into the metal-free macrocycle. It has been developed in the course o f preparing four new and two known metal-free, six new dihydroxysilico n, and six new bis-trihexylsiloxysilicon octabutoxy- and octabutoxyben zophthalocyanines. One of the siloxysilicon compounds, that with the l igand -dibenzo[b,g]dinaphtho[2,3-l:2',3'-q]porphyrazine, has a Q-band at a wavelength of 804 nm and an extinction coefficient of 1.9 x 10(5) M-1 cm(-1). Its wavelength thus matches the wavelength of the output of the most common GaAlAs diode laser. The compound and its analog in which the benzo rings are trans to each other instead of cis have no t endency to aggregate in benzene up to a concentration of 150 mu M. The triplet state of the cis isomer has an absorption maximum at 640 nm a nd a Lifetime in deaerated benzene solution of 105 mu s, while the tri plet state of the trans isomer has a maximum at 660 nm and a lifetime of 72 mu s. Both isomers have a triplet quantum yield, Q(t), of ca. 0. 20 and a singlet oxygen quantum yield, Q(Delta), of ca. 0.20, photoche mical properties that are consistent with potentially efficient photos ensitization action in photodynamic therapy of tumors. For both sensit izers, energy transfer from the sensitizer triplet to ground state of dioxygen is reversible at appropriate concentrations. For the cis isom er, the equilibrium constant for the energy transfer process, K-e, is 0.012 +/- 0.001, and the triplet state energy calculated from this, E- T, is 21.29 kcal/mol (E-T derived from phosphorescence measurements is 21.26 kcal/mol). For the trans isomer, K-e, is 3.68 x 10(-3) and E-T is 19.27 kcal/mol.