Synthesis of a Series of Octabutoxy- and Octabutoxybenzophthalocyanines and Photophysical Properties of Two Members of the Series

Abstract

We have developed a new route to silicon-centered phthalocyanines and phthalocyanine-like compounds that is robust and flexible, and of considerable potential usefulness. This route entails insertion of silicon into the metal-free macrocycle. It has been developed in the course of preparing four new and two known metal-free, six new dihydroxysilicon, and six new bis-trihexylsiloxysilicon octabutoxy- and octabutoxybenzophthalocyanines. One of the siloxysilicon compounds, that with the ligand 5,9,12,16,19,23,28,32-octabutoxy-33H,35H-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 × 105 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 tendency to aggregate in benzene up to a concentration of 150 μM. The triplet state of the cis isomer has an absorption maximum at 640 nm and a lifetime in deaerated benzene solution of 105 μs, while the triplet state of the trans isomer has a maximum at 660 nm and a lifetime of 72 μs. Both isomers have a triplet quantum yield, Q t, of ca. 0.20 and a singlet oxygen quantum yield, Q Δ, of ca. 0.20, photochemical properties that are consistent with potentially efficient photosensitization action in photodynamic therapy of tumors. For both sensitizers, energy transfer from the sensitizer triplet to ground state of dioxygen is reversible at appropriate concentrations. For the cis isomer, 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 × 10-3 and E T is 19.27 kcal/mol.

Porous silicon in drug delivery devices and materials☆

“…In addition, photoexcitation of quantum confined silicon nanostructures in aqueous aerated media has been shown to produce singlet oxygen [32][33][34][35]. The ability of the porous Si nanostructure to degrade into relatively harmless silicic acid byproducts makes porous Si an attractive alternative to molecular (typically porphyrinbased [195]) sensitizers for photodynamic therapy [196,197].…”

A high-yield microwave heating method for the preparation of (phthalocyaninato)bis(chloro)silicon(IV)

“…Silicon phthalocyanines have a range of physical and chemical properties which have resulted in recent interest in these compounds, particularly in photodynamic therapy [1][2][3][4][5], fluorescence [6] and non-linear optics [7][8][9]. Figure 1 shows the known methods for the preparation of silicon phthalocyanines and the yields of silicon phthalocyanine obtained by these methods.…”

“…All but one of these involve the formation of the unsubstituted macrocycle from a disubstituted benzene or isoindolene [10,11]. Recently the insertion of silicon into peripherally substituted phthalocyanines has been achieved by an analogous method to that used to insert silicon into a porphyrin (method E) [1,12]. The yields of these preparations are dependent on the nature of the peripheral substitution of the macrocycle, and good to essentially quantitative yields can be achieved [1].…”

“…Recently the insertion of silicon into peripherally substituted phthalocyanines has been achieved by an analogous method to that used to insert silicon into a porphyrin (method E) [1,12]. The yields of these preparations are dependent on the nature of the peripheral substitution of the macrocycle, and good to essentially quantitative yields can be achieved [1]. However, the unmetallated phthalocyanines are expensive and their preparation is difficult and only achieved in low yields [13], thereby reducing the overall yield of silicon phthalocyanine.…”

Estudo químico-quântico ab initio e semi-empírico de compostos inorgânicos e orgânicos com possíveis aplicações tecnológicas

“…As ftalocianinas de silício apresentam uma grande quantidade de propriedades físi-cas e químicas, as quais fornecem a estes compostos grandes possibilidades de aplicações tecnológicas, particularmente em terapia fotodinâmica [100,101,102], fluorescência [103] e propriedades óticas não lineares [104].…”