SYNTHESIS AND PHOTOCHEMICAL PROPERTIES OF ALUMINUM, GALLIUM, SILICON, AND TIN NAPHTHALOCYANINES

The synthesis and characterization of 30 Al, Ga, Si, and Sn naphthalocyanines relevant to the search for improved photodynamic therapy agents are reported. The compounds that have been studied are AlNcCl, AlNcOH, AlNcOSi-(n-C6H13)3, (AlNcF)n, GaNcCl, GaNcOH, GaNcOH.2H2O, GaNcOSi(n-C6H13)3, (GaNcF)n, SiNc(O-n-C8H17)2, SiNc[(OCH2CH2)approximately 17OCH3]2, SiNc[(OCH2CH2)approximately 43OCH3]2, SiNc[4-OCH2CH2)approximately 26OC6H4C(CH3)2CH2C(CH3)3]2, SiNc[4-OC6H4CO(OCH2CH2)3OCH3]2, SiNc[OSi(n-C4H9)2(n-C18H37)]2, SiNc[OSi(i-C4H9)2(n-C18H37)]2, SiNc[OSi(CH3)2(CH2)10COOCH3]2, SiNc(2/3-Cl)4Cl2, SiNc(2/3-Cl)4(O-n-C8H17)2, SiNc(2/3-Cl)4[OSi(n-C6H13)3]2, SiNc[2/3-Cl)4(OH)2, SiNc(2/3-Br)4Cl2, SiNc(2/3-Br)4(O-n-C8H17)2, SiNc(2/3-Br)4[OSi(n-C6H13)3]2, SiNc(2/3-Br)4(OH)2, SnNcCl2, SnNc, SnNCI2, SnNc(OH)2, and SnNc[OSi(n-C6H13)3]2. For nine of these compounds and for an additional compound, SiNc [OSi(n-C6H13)3]2, one or more of the following photoproperties have been determined: lambda(Q), the Q(0,0)-band absorption maximum; PHI(T), the triplet-state quantum yield or PHI(T)', an approximation of PHI(T); DELTA-epsilon(T) the triplet-minus-ground-state extinction coefficient difference at 590 nm; tau(T), the triplet-state lifetime in the absence of O2; and k(ox), the bimolecular rate constant for the quenching of the triplet state by O2. The values obtained show that lambda(Q) is essentially independent of the kinds of atoms in the 2 and 3 positions of the macrocycle and that PHI(T) is moderately and directly dependent on the atomic numbers of the atoms in the center and the 2 and 3 positions of the ring. In the case of the silicon naphthalocyanines, they show in addition that lambda(Q), PHI(T)', and tau(T) are moderately dependent on the type of axial ligand present.