Synthesis, photophysics and electrochemical study of tin macrocycles

Three non-peripherally substituted tin(IV) macrocylic compounds, octahexylphthalocyaninato dichlorotin(IV) (35a), octahexyltetrabenzo-5,10,15-triazaporphyrinato dichlorotin(IV) (35b) and octadecylphthalocyaninato dichlorotin(IV) (35c) were synthesized and their photophysical and electrochemical behaviour studied. Complex (35b), containing a CH group in place of one of the aza nitrogen atom of the phthalocyanine core, shows a split Q band due to its lower symmetry. The triplet state quantum yields were found to be lower than would be expected on the basis of the heavy atom effect of tin as the central metal for phthalocyanine derivatives (35a and 35c). In contrast, (35b) shows a triplet quantum yield ΦT = 0.78. The triplet state lifetimes were solvent dependent, and were higher in THF than in toluene. Cyclic voltammetry and spectroelectrochemistry of the complexes revealed only ring based redox processes. This thesis also reports on the microwave syntheses of tetrasulphonated tin phthalocyanine and tetrasulphonated tin α,β,γ-tetrabenzcorrole. The latter was only formed at low ratios (< 1:8) of 4-sulfophthalic acid to urea. Both complexes are aggregated in aqueous media, but can be partly or fully disaggregated by the addition of Triton X-100. The SnTSTBC complex has lower triplet life times and yields, while binding constant and quenching (of bovine serum albumin) constant are lower for SnTSTBC, compared to SnTSPc. Finally Non-peripherally (α) tetra- (40) and octa-(38a) substituted dodecyl-mercapto tin(IV) phthalocyanines where synthesized and the electrochemical behavior studied. Cyclic voltammetry and spectroelectrochemistry show ring-based reductions for (38a) and (40); the former shows two ring oxidations, while the latter shows only one ring based oxidation. The adsorption kinetics of (38a) and (40) on a gold electrode have been investigated by electrochemical impedance spectroscopy (EIS). The equilibrium constant (K) for the adsorption and the Gibbs free energy ΔG(ads) of the self-assembled monolayer (SAMs) were evaluated based on the Frumkin isotherm. The interaction factor between adsorbate –adsorbate molecules is also discussed

Nanocomposites of nickel phthalocyanines as electrocatalysts for the oxidation of chlorophenols an experimental and theoretical approach

In this work the interaction between peripherally (b) substituted nickel tetrahydroxyphthalocyanines (b-NiPc(OH)4 and poly-b-Ni(O)Pc(OH)4) with 4-chlorophenol is theoretically rationalized by performing calculations at the B3LYP/6-31G(d) level. Density functional theory (DFT) and molecular orbital theory are used to calculate the condensed Fukui function for phthalocyanine derivatives and 4-chlorophenol, in order to determine the reactive sites involved when 4-chlorophenol is oxidized, and to compare theoretically predicted reactivity to experimentally determined electrocatalytic activity. Electrocatalytic activities of adsorbed NiPc derivatives: OPGE-α-NiPc(OH)8 (OPGE = ordinary pyrolytic graphite electrode, α = nonperipheral substitution), OPGE-a-NiPc(OH)4 and OPGE-β- NiPc(OH)4 are compared with those of the polymerized counterparts: OPGE-poly-α-Ni(O)Pc(OH)8, OPGE poly-a-NiPc(OH)4 and OPGE-poly-β-NiPc(OH)4, respectively. β-NiPc(NH2)4, β-NiPc(OH)4, α-NiPc(OH)4, α-NiPc(OH)8, α-NiPc(C10H21)8 are adsorbed on singled walled carbon nanotube (SWCNT) and β-NiPc(NH2)4-SWCNT (linked to SWCNT), are used to modify glassy carbon electrode (GCE) and employed for the electro oxidation of chlorophenols. The β-NiPc(NH2)4-SWCNT gave the best current response for the oxidation of 4-chlorophenol. α-NiPc(OH)8-SWCNT and α-NiPc(C10H21)8 gave the best resistance to electrode fouling due to oxidation by product of 4-chlorophenol. The synthesis of conjugates of cadmium telluride quantum dots (CdTe-QDs) capped with thioglycolic acid and peripherally substituted nickel tetraamino phthalocyanine (β-NiPc(NH2)4) complex were also employed for the oxidation of chlorophenols. Separation of one of the diastereomers of 1, 2-subnaphthalocyanine (SubNPc) was achieved as well as separation of the enantiomers. The absorption and magnetic circular dichroism spectra, together with theoretical calculations, reveal rather small variations in the frontier molecular orbitals of the SubNPc compared to conventional subphthalocyanine (SubPc), except for the destabilization of the highest occupied molecular orbital (HOMO), which results in a characteristic absorption in the Soret band region. The chirality of SubNPc, including the cyclic dichroism (CD) signs and intensities, are discussed in detail

Electrooxidation of Chlorophenols Catalyzed by Nickel Octadecylphthalocyanine Adsorbed on Single‐Walled Carbon Nanotubes

We described the synthesis of nickel octadecylphthalocyanine (NiPc(C10H21)8), followed by its adsorption on single-walled carbon nanotubes (SWCNT) to form SWCNT-NiPc(C10H21)8 conjugates. SWCNT-NiPc(C10H21)8 was used to modify a glassy carbon electrode (GCE) and for the electrooxidation of 4-chlorophenol and 2,4-dichlorophenol. The SWCNT and NiPc(C10H21)8 have a synergistic effect on each other in terms of improving electrocatalysis for the detection of chlorophenols. The stability of the electrode improved in the presence of NiPc(C10H21)8 or NiPc compared to the bare GCE. The presence of SWCNT improves the electrocatalytic behaviour of NiPc(C10H21)8 but not of unsubstituted NiPc. All modified electrodes showed improved stability towards the detection of 2,4-dichlorophenol. The best stability for 4-CP detection was observed in the presence of SWCNT for NiPc(C10H21)8

Redox activity of CdTe quantum dots linked to nickel tetraaminophthalocyanine

Cadmium tellurite quantum dots (CdTe-QDs) are linked to nickel tetraamino phthalocyanine (CdTe-QDs-NiTAPc) through an amide bond. Differential pulse voltammetry shows that that NiTAPc stabilizes the QDs against oxidative disintegration into metallic products on oxidation. Electrocatalytic oxidation of 2, 4-dichlorophenol (DCP) and pentachlorophenol (PCP) on CdTe-QDs and CdTe-QDs-NiTAPc adsorbed or electrodeposited onto a gold electrode were studied. Adsorbed CdTe-QDs-NiTAPc shows the lowest potential for DCP and PCP oxidation and it is also more stable to fouling by PCP and its oxidation products compared to adsorbed CdTe-QDs without NiTAPc. Electrodeposited CdTe-QDs or CdTe-QDs-NiTAPc show the best activity in terms of enhanced currents towards the oxidation of the chlorophenols

Single walled carbon nanotubes functionalized with nickel phthalocyanines

In this work we report on electrochemical behavior of nickel phthalocyanine derivatives tetrasubstituted peripherally and non-peripherally with hydroxy and used to modify single walled carbon nanotubes. Nickel phthalocyanine complex octasubstituted at the peripheral positions with hydroxy groups was also used to modify single walled carbon nanotubes. Nickel phthalocyanine complex tetrasubstituted with amino groups at peripheral position was covalently and non-covalently linked to single walled carbon nanotubes. All the conjugates of nickel phthalocyanine derivatives with single walled carbon nanotubes were used for the electro oxidation of 4-chlorophenol. The nickel phthalocyanine octabsubstituted with hydroxy groups at the non-peripheral positions gave the best current response and the best resistance against electrode fouling for the oxidation of 4-chlorophenol

Enhanced optical limiting performance in phthalocyanine-quantum dot nanocomposites by free-carrier absorption mechanism

Enhanced nonlinear optical properties (in dimethyl sulphoxide) is observed for 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy)phthalocyaninato indium(III) chloride (InPc) when covalently linked to CdSe/ZnS or CdSe quantum dots (QDs). The experimental nonlinear optical parameters were obtained from Z-Scan measurements. Contributions from two-photon absorption (2PA) due to the InPc, and free-carrier absorption (FCA) by QDS have been identified as the main factors responsible for the enhanced optical limiting. The effective nonlinear absorption coefficient for InPc-CdSe/ZnS was found to be 700.0 cm/GW. The FCA cross-sections for InPc-CdSe/ZnS and InPc-CdSe composites were found to be 1.52 × 10−19 and 6.00 × 10−20 cm2 respectively. A much lower limiting threshold of 92 mJ cm−2 was observed for InPc-CdSe/ZnS nanocomposite, hence, making it suitable for use as optical limiting material. Density Functional Theory (DFT) calculations on similar phthalocyanine-quantum dots system was modeled in order to explain the enhancement in the observed nonlinear optical properties of the Pc in the presence of the QDs. The experimentally determined nonlinear optical properties are well within the range of the DFT calculated properties

Voltammetry and electrochemical impedance spectroscopy of gold electrodes modified with CdTe quantum dots and their conjugates with nickel tetraamino phthalocyanine

This work reports on the synthesis of conjugates of cadmium telluride quantum dots (CdTe-QDs) caped with thioglycolic acid and peripherally substituted nickel tetraamino phthalocyanine (NiTAPc) complex. The conjugates are characterized using cyclic (CV) and differential pulse (DPV) voltammetries, electrochemical impedance spectroscopy, X-ray powder diffraction, infrared spectroscopy, Raman spectroscopy, atomic force microscopy and time correlated single photon counting. CV and DPV show that NiTAPc stabilizes the CdTe QDs against oxidation to metallic products

The effects of point of substitution on the formation of manganese phthalocyanine-based molecular materials

Molecular films of manganese phthalocyanine (MnPc) complexes, tetra-substituted with 2-diethylaminoethanethio at the peripheral (Mn(OAc)-β-TDEAETPc, 1) and non-peripheral (Mn(OAc)-α-TDEAETPc, 2) positions were formed on glassy carbon electrode by electropolymerization and electrodeposition respectively. Atomic force microscopy images confirmed the presence of the films and revealed significant morphological differences. The films exhibited an electrocatalytic activity towards the oxidation of the insecticide, bendiocarb. Hydrodynamic technique, using rotating disc electrode voltammetry, was used to investigate the kinetics of electro-oxidation of the insecticide. Morphological differences of the films significantly influenced kinetic parameters. Values of Tafel slopes, obtained from Tafel plots, suggested that catalysis of bendiocarb occurred via outer sphere mechanism

Photophysical and nonlinear optical characteristics of pyridyl substituted phthalocyanine-detonation nanodiamond conjugated systems in solution

In this study photophysical, nonlinear absorption and optical limiting properties of detonation nanodiamonds (DNDs)-phthalocyanine nanoconjugate systems containing: 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyaninato (H2TPPc), 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato zinc(II) (ZnTPPc) and 2,9(10),16(17),23(24)-tetrakis-(4-pyridyloxy) phthalocyanato silicon(IV) hydroxide (Si(OH)2TPPc), were investigated in dimethylsulfoxide solution. Pcs were non-covalently linked to nanondiamonds (also covalently linked for Si(OH)2TPPc) and investigated using 532 nm laser excitation at 10 ns pulses for their optical limiting properties. Complexes that have higher triplet state absorption also possessed enhanced nonlinear optical behaviour following reverse saturable absorption mechanism. Superior optical performance is observed when the Pcs had a central metal with axial ligands conjugated to DNDs in solution. Nanoconjugate of DNDs-Si(OH)2TPPc and respective Pc in solution gave the highest imaginary third-order susceptibility (Im[X(3)]) and hyperpolarizability (γ) at 2.91 × 10−8 and 3.17 × 10−8 esu and 3.88 × 10−28 and 4.22 × 10−28 esu, respectively, with Ilim value of 0.47 and 0.39 J·cm−2

Characterization of nickel tetrahydroxy phthalocyanine complexes and the electrocatalytic oxidation of 4-chlorophenol

This work reports on the use of nickel(II) tetrahydroxy (NiPc(OH)4) and (poly-Ni(OH)Pc(OH)4) phthalocyanine complexes as films on ordinary poly graphite electrode (OPGE) for the electrochemical oxidation of 4-chlorophenol (4-CP). The NiPc(OH)4 film was electrotransformed to Ni(OH)Pc(OH)4 film in aqueous 0.1 M NaOH solution to the ‘O–Ni–O oxo’ bridge form. The result showed that the Ni(OH)Pc(OH)4 film on OPGE was more electroactive in terms of increase in current and less catalytic in terms of potential compared to the adsorbed NiPc(OH)4 on OPGE. The reactivity of the two molecules was explained by theoretical calculations. The energies of the frontier orbitals of NiPc(OH)4, Ni(OH)Pc(OH)4 and 4-chlorophenol were calculated using density functional theory (DFT) method. The inter molecular hardness (η) and donor–acceptor hardness (ηDA) of Ni(OH)Pc(OH)4, NiPc(OH)4, Ni(OH)Pc(OH)4/4-chlorophenol and NiPc(OH)4/4-chlorophenol were estimated. The Ni(OH)Pc(OH)4, showed stronger interaction with 4-chlorophenol than NiPc(OH)4. DFT method was also used to model IR and Raman spectrum of H2Pc(OH)4 and NiPc(OH)4