The synthesis and photophysicochemical properties of low-symmetry zinc phthalocyanine analogues

The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (Ф_T) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest Ф_T values and triplet lifetimes (τ_T) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.     

The Electrochemical Behavior of Gold Nanoparticle‐Tantalum(V) Phthalocyanine Composites: Applications Towards the Electroanalysis of Bisphenol A

The formation of gold nanoparticle (AuNP) composites with tantalum phthalocyanines (TaPc) complexes { 1a and 1b (Figure 1 )} is reported. The TaPc‐AuNPs conjugates were characterised by atomic force microscopy (AFM) and transmission electron microscopy. The AFM analyses show that conjugates of TaPc with AuNPs are more aggregated when compared to AuNPs alone. The conjugates and TaPc complexes were immobilized on a gold electrode by drop and dry method and these were characterized by electrochemical impedance spectroscopy. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc complexes. All the modified electrodes showed electrocatalytic oxidation of bisphenol A. The limits of detection for complexes 1a and 1 b were 4.78×10^?10 and 2.76×10^?10 mol L^?1, respectively.     

Synthesis and photophysical behavior of a novel zinc phthalocyanine containing a single carboxylic acid and three phenylthio substituents

Zinc 2, (3)-tri-(phenylthio)-2, (3)-carboxy phthalocyanine (ZnPc(COOH)(SPh)₃), zinc 2, (3)-tetra-(phenylthio) phthalocyanine (ZnPc(SPh)₄) and 2, (3)-tetra-(phenylthio) phthalocyanine (H₂Pc(SPh)₄) were synthesized and their photophysical behavior were compared with those of a number of zinc phthalocyanine (ZnPc) derivatives. ZnPc(COOH)(SPh)₃ and ZnPc(SPh)₄ had similar fluorescence (Φ_F=0.14) and triplet state (Φ_T=0.65) quantum yields in dimethylsulfoxide, hence showing no effects of the replacement of one of the phenylthio groups with a carboxylic acid group. ZnPc(COOH)(SPh)₃ displayed a slightly shorter triplet lifetime (τ_T=331 μs) than ZnPc (τ_T=350 μs) in DMSO, but within the range of ZnPc derivatives. The triplet lifetime for ZnPc(COOH)(SPh)₃ is much longer than for the symmetrical derivative (ZnPc(SPh)₄) with τ_T=149 μs in DMSO.     

Interaction of CdTe Quantum Dots with 2,2-Diphenyl-1-Picrylhydrazyl Free Radical: A Spectroscopic, Fluorimetric and Kinetic Study

The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH^●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH^● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH^● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH^● is proposed.     

Synthesis and photophysical studies of phthalocyanine-gold nanoparticle conjugates

This work reports on the synthesis, characterization and photophysical studies of phthalocyanine-gold nanoparticle conjugates. The phthalocyanine complexes are: tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyanine (3), 2,9,17,23-tetrakis-[(1, 6-hexanedithiol) phthalocyaninato]zinc(II) (8) and [8,15,22-tris-(naptho)-2(amidoethanethiol) phthalocyanato] zinc(II)(10). The gold nanoparticles were characterized using transmission electron microscopy, X-ray diffraction, atomic force microscopy and UV-vis spectroscopy where the size was confirmed to be ～5 nm. The phthalocyanine Au nanoparticle conjugates showed lower fluorescence quantum yield values with similar fluorescence lifetimes compared to the free phthalocyanines. The Au nanoparticle conjugates of 3 and 10 also showed higher triplet quantum yields of 0.69 to 0.71, respectively. A lower triplet quantum yield was obtained for the conjugate compared to free phthalocyanine for complex 8. The triplet lifetimes ranged from 70 to 92 μs for the conjugates and from 110 to 304 μs for unbound Pc complexes.     

Electroanalytical detection of heavy metals using metallophthalocyanine and silica-coated iron oxide composites

The monitoring of heavy metal ions particularly in water is important in safeguarding the environment and humans from the toxic effects these metal ions pose. This work describes the synthesis, characterization and electrocatalytic properties of silica-coated iron oxide nanoparticles (Si-NP) in the presence of cobalt or iron phthalocyanines (MPc) for heavy metal (HM) detection. TEM, XRD, XPS and VSM confirmed the successful synthesis of Si-NP with an average diameter of 12.07 nm. The electrochemical sensing properties of MPc/Si-NP-modified glassy carbon electrodes (GCE) were assessed for HM detection. Differential pulse anodic stripping voltammetry (DPASV) studies indicated detection limits that compared positively with the literature. The FePc/Si-NP composite showed the lowest detection limits (S/N?=?3) of 3.66, 11.56, 2.28, 4.54 μg L^?1 for arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb), respectively. A linear working range of 10–100 μg L^?1 was obtained for As³⁺, Hg²⁺ and Pb²⁺ ions while it was between 20 and 100 μg L^?1 for Cd²⁺ ions. Both composites displayed reproducible signals for the simultaneous detection of the HMs for ten consecutive scans. These composites offer a cheap and simplistic sensing device for HM analysis.     

In Silico Drug Repurposing Approach: Investigation of Mycobacterium tuberculosis FadD32 Targeted by FDA-Approved Drugs

Background: Despite the enormous efforts made towards combating tuberculosis (TB), the disease remains a major global threat. Hence, new drugs with novel mechanisms against TB are urgently needed. Fatty acid degradation protein D32 (FadD32) has been identified as a promising drug target against TB, the protein is required for the biosynthesis of mycolic acids, hence, essential for the growth and multiplication of the mycobacterium. However, the FadD32 mechanism upon the binding of FDA-approved drugs is not well established. Herein, we applied virtual screening (VS), molecular docking, and molecular dynamic (MD) simulation to identify potential FDA-approved drugs against FadD32. Methodology/Results: VS technique was found promising to identify four FDA-approved drugs (accolate, sorafenib, mefloquine, and loperamide) with higher molecular docking scores, ranging from −8.0 to −10.0 kcal/mol. Post-MD analysis showed that the accolate hit displayed the highest total binding energy of −45.13 kcal/mol. Results also showed that the accolate hit formed more interactions with FadD32 active site residues and all active site residues displayed an increase in total binding contribution. RMSD, RMSF, Rg, and DCCM analysis further supported that the presence of accolate exhibited more structural stability, lower bimolecular flexibility, and more compactness into the FadD32 protein. Conclusions: Our study revealed accolate as the best potential drug against FadD32, hence a prospective anti-TB drug in TB therapy. In addition, we believe that the approach presented in the current study will serve as a cornerstone to identifying new potential inhibitors against a wide range of biological targets.     

Photophysical behaviour of asymmetrically substituted metal free, Mg and Zn phthalocyanines in the presence of folic acid

This work reports on the synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines containing a mono carboxylic acid group for possible linking to biological molecules via an amide bond. Successful synthesis of the phthalocyanines was achieved through the statistical condensation method. The phthalocyanines were mixed with folic acid and their photophysical properties were examined. The triplet quantum yield values for all the complexes in DMSO were between 0.49 and 0.74 and in the presence of folic acid they were between 0.37 and 0.63. The lifetimes were generally good ranging from 70 to 290 μs in the absence or presence of folic acid.