Institute of Fundamental Technological Research

This work reports on the linkage of 2(3),9(10),16(17),23(24) tetrakis [(benzo[d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (1) and indium(III) chloride (2) to gold speckled silica (GSS) nanoparticles via gold to
sulphur (Au-S) and gold to nitrogen (Au-N) self-assembly to form the conjugates: 1-GSS and 2-GSS. The formed
conjugates were characterized using microscopic and spectroscopic techniques, and the photophysicochemical
properties and photodynamic therapy (PDT) activity against human breast adenocarcinoma cell line (MCF-7
cells) were studied. The conjugates afforded decrease in fluorescence quantum yields with corresponding increase in triplet and singlet oxygen quantum yields when compared to phthalocyanines alone. Singlet oxygen is
cytotoxic to cancer cells hence it is important for PDT. The in vitro dark toxicity of complex 2 and 2-GSS against
MCF–7 cells showed ≥93% viable cells within concentration ranges of 10–160 μg/mL. 2–GSS showed enhanced
PDT activity with less than 50% viable cells at 80 μg/mL as compared to 2 and GSS alone which showed > 60%
viable cells within 10–160 μg/mL. The observed improvements in the PDT activity of 2-GSS could be attributed
to the high singlet oxygen generation of 2-GSS compared to 2 alone in addition to the phototoxicity of GSS.

The syntheses of neodymium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (2),
bis europium(III) 2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (3), bis dysprosium(III)
2,9,16,23-tetrakis-(2,6-di-tert-butyl-4-methylphenoxy)phthalocyanine (4) and their conjugated analogues with
nitrogen doped quantum dots (NGQDs) are reported herein. The optical nonlinearity of the sandwich-type phthalocyanine complexes and their conjugates with NGQDs were studied in dimethyl sulfoxide using the
open aperture Z-scan technique at an excitation wavelength of 532 nm with a 10 ns pulse. The nonlinear
absorption coefficient (beff) value of the samples ranges from 15 cm GW1 to 89.6 cm GW1
. Complex 4 and
its conjugates afforded a strong optical limiting behaviour compared to the other samples. These fabricated
complexes and their conjugates with NGQDs could serve as a plausible nonlinear optical (NLO) material due
to their fascinating NLO properties

In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with <50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with <50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres

Benzothiazole phthalocynines complexes: tetrakis[(benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] indium(III) chloride (1) and tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] indium(III) chloride (2) were synthesisized and their nanosecond nonlinear optical behaviours in solution, solid state and when conjugated to metallic nanoparticles were examined and compared to those of the corresponding ZnPc and GaPc which are designated as: tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] zinc(II) (3), tetrakis[(4-benzo[d]thiazol-2-ylphenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5) and tetrakis[(4-benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6). Trends in the electronic structures were identified through a comparison of the UV–vis absorption and magnetic circular dichroism (MCD) spectroscopy of the complexes and calculated spectra predicted by time dependent density functional theory (TD-DFT). Of all the complexes and nanoconjugates, complex 2 (containing sulphur linkages and In as a central metal) gave the best optical limiting behaviour.

The syntheses of zinc(II) tetra–[3–(4–phenoxy) (propanoic acid) phthalocyanine] (2) and zinc(II) mono–[3–(4–phenoxy) (propanoic acid) phthalocyanine (3) are reported in this work. Compounds 2 and 3 were covalently linked to glutathione capped silver (AgNPs–GSH), gold (AuNPs–GSH) and silver-gold alloy (Ag3Au1NPs–GSH) nanoparticles (NPs) via an amide bond formation to afford the conjugates: 2–AgNPs–GSH, 3–AgNPs–GSH, 2–AuNPs–GSH, 3–AuNPs–GSH, 2-Ag3Au1NPs–GSH and 3-Ag3Au1NPs–GSH. The photophysicochemical behaviours of the compounds and their conjugates with NPs were assessed in solution. The conjugates afforded a decrease in fluorescence quantum yields and lifetimes with improved triplet quantum yields in comparison to the compounds. Accordingly, the AgNPs and AuNPs conjugates with the compounds afforded high singlet quantum yields. On the contrary, the conjugates of the alloy afforded decreased singlet quantum yields probably due to the screening effect. The compounds and their conjugates with NPs could serve as a viable and efficacious photosensitizer for photodynamic therapy.

The synthesis of ball–type indium phthalocyanine (complex 4) and its covalent attachment to glutathione (GSH–) capped (Ag, Au, CdTeSe, CdTeSe/ZnO) nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical behaviour were investigated. We observed a decrease in the fluorescence quantum yield with corresponding increase in the triplet quantum yield of the nanoconjugates in comparison to complex 4 alone. The reverse saturable absorption was found to be dependent on excited state absorption. The optical limiting threshold ranges from 0.40–0.78 (J/cm2). The nanoconjugate of the complex 4 with GSH–CdTeSe/ZnO (QD1) accounted for the most improved triplet state parameters and nonlinear optical behaviour in comparison to complex 4 and the other nanoconjugates studied in this work.