Novel porphyrazines containing peripherally functionalized macrocyclic (N2O2, N2S2) units: Synthesis and characterization

Novel maleonitrile moieties were synthesized by cyclization of 2,3-bis[(2-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile with 1,2-bis(2-iodoethoxy)-4-nitrobenzene or o-xylyenebis(1-chloro-3-thiapropane) under conditions of high dilution. A series of novel, free-base, magnesium and zinc porphyrazines bearing macrocyclic substituents in peripheral positions were prepared via Linstead macrocyclization reactions of different maleonitrile derivatives, 12-nitro-4,7-bis(pyridin-2-ylmethyl)-2,3,4,7,8,9-hexahydro-1,10,4,7-benzodioxa-diaza-cyclododecine-5,6-dicarbonitrile or 5,8-bis(pyridin-2-ylmethyl)-1,3,4,5,8,9,10,12-octa-hydro-2,11,5,8-benzodi-thiadiazacyclo-tetradecine-6,7-dicarbonitrile and the corresponding divalent metal salts. Pentanuclear copper(II) complexes were also prepared from the corresponding zinc(II) porphyrazine derivatives. The compounds were characterized by a combination of elemental analysis, FT-IR, UV–vis, ¹H NMR, ¹³C NMR and MS spectral data.     

1,4-Dithiaheterocycle-fused porphyrazines: Synthesis,characterization, voltammetric and spectroelectrochemical properties

Porphyrazines (M = H, Mg, Zn and Co) with a 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin group fused to each pyrrole unit were synthesized and characterized starting with the corresponding unsaturated dicarbonitrile derivative. The voltammetric and spectroelectrochemical characterizations of the metallo-porphyrazines (M = 2H⁺, Mg²⁺, Zn²⁺ and Co²⁺) substituted with 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin groups on peripheral positions are described. Cyclic voltammetry and differential pulse voltammetry studies showed that while metal-free, magnesium, and zinc porphyrazines represented well-defined one-electron ligand-based reductions and ligand-based one-electron oxidation couples, cobalt porphyrazine gave both metal-based and ligand-based reduction and oxidation couples. Assignments of the redox couples were confirmed by spectroelectrochemical measurements.     

Electrocatalytic oxygen reduction and hydrogen evolution reactions on phthalocyanine modified electrodes: Electrochemical, in situ spectroelectrochemical, and in situ electrocolorimetric monitoring

This study describes electrochemical, in situ spectroelectrochemical, and in situ electrocolorimetric monitoring of the electrocatalytic reduction of molecular oxygen and hydronium ion on the phthalocyanine-modified electrodes. For this purpose, electrochemical and in situ spectroelectrochemical characterizations of the metallophthalocyanines (MPc) bearing tetrakis-[4-((4′-trifluoromethyl)phenoxy)phenoxy] groups were performed. While CoPc gives both metal-based and ring-based redox processes, H₂Pc, ZnPc and CuPc show only ring-based electron transfer processes. In situ electrocolorimetric method was applied to investigate the color of the electrogenerated anionic and cationic forms of the complexes. The presence of O₂ in the electrolyte system influences both oxygen reduction reaction and the electrochemical and spectral behaviors of the complexes, which indicate electrocatalytic activity of the complexes for the oxygen reduction reaction. Perchloric acid titrations monitored by voltammetry represent possible electrocatalytic activities of the complexes for hydrogen evolution reaction. CoPc and CuPc coated on a glassy carbon electrode decrease the overpotential of the working electrode for H⁺ reduction. The nature of the metal center changes the electrocatalytic activities for hydrogen evolution reaction in aqueous solution. Although CuPc has an inactive metal center, its electrocatalytic activity is recorded more than CoPc for H⁺ reduction in aqueous solution.     

Diazepinoporphyrazines Containing Peripheral Styryl Substituents and Their Promising Nanomolar Photodynamic Activity against Oral Cancer Cells in Liposomal Formulations

The photochemical properties and photodynamic activity of three porphyrazines (Pzs) containing annulated diazepine rings, including novel demetalated porphyrazine‐possessing bis(styryl)diazepine moieties were investigated. The porphyrazines were evaluated in terms of their electronic absorption and emission properties, their tendency to undergo aggregation and photodegradation, as well as their singlet oxygen generation efficiency. The in vitro photodynamic activity of the porphyrazines and their liposomal formulations were examined by using two oral squamous cell carcinoma cell lines. Magnesium(II) tribenzodiazepinoporphyrazine ( 1 ) revealed the highest phototoxic effect in both cell lines used, H413 and HSC‐3. Encapsulation of Pz 1 into L ‐α‐phosphatidyl‐d,l ‐glycerol:1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine liposomes resulted in a nearly threefold increase in photocytotoxicity relative to that of the solution of Pz 1 (IC₅₀ values of 45 and 129 nM , respectively).     

Synthesis and spectroelectrochemistry of new phthalocyanines with ester functionalities

Metal-free (H₂Pc) and metallophthalocyanines (MPc; M: Co, Zn) with four n-pentyl ester of thioglycolic acid groups have been synthesized by the esterification of the corresponding carboxylic acid derivatives with n-pentanol. The novel phthalocyanine compounds were characterized by elemental analyses, mass, FT-IR and UV-Vis spectral data. The aggregation investigations carried out in different concentrations and solvents indicate that ester substituted metal-free and metallo-phthalocyanine compounds have not shown any aggregation behavior in the concentration range of about 10⁻⁵ M. Electrochemical and in-situ spectroelectrochemical measurements give common MPc based redox behaviors which supported the proposed structure of the complexes. While CoPc gives both metal-based and ring-based redox processes, H₂Pc and ZnPc give only ring-based electron transfer processes. In-situ electrocolorimetric method was applied to investigate the color of the electro-generated anionic and cationic forms of the complexes.     

Voltammetric, spectroelectrochemical, and electrocatalytic properties of thiol-derivatized phthalocyanines

Voltammetric and spectroelectrochemical properties and electrocatalytic activities of thiol-derivatized phthalocyanine complexes for hydrogen production have been investigated. Voltammetric and spectroelectrochemical measurements show that while cobalt phthalocyanine complexes (CoPc) present well defined metal-based and ring-based redox processes, all other complexes give only ring-based reduction and oxidation processes. The redox processes are generally diffusion-controlled, reversible and one-electron transferred processes. The complexes bearing tetra(acetoxyethylthio) substituents represents aggregation tendency in DCM solution. Cobalt and nickel phthalocyanines are easily electrodeposited on the GCE working electrode during the repeating cycles of positive potentials. Electrocatalytic activities of electrodeposited complexes indicated that CoPc catalyzed the proton reduction via the electro-reduced [Co^IPc²⁻]¹⁻ and/or [Co^IPc³⁻]²⁻ species depending on the pH of the aqueous solution.     

Voltammetric, in-situ spectroelectrochemical and in-situ electrocolorimetric characterization of phthalocyanines

In this work, electrochemical, and in-situ spectroelectrochemical characterization of the metallophthalocyanines bearing tetra-(1,1-(dicarbethoxy)-2-(2-methylbenzyl))-ethyl 3,10,17,24-tetra chloro groups were performed. Voltammetric and in-situ spectroelectrochemical measurements show that while cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. The redox processes are generally diffusion-controlled, reversible and one-electron transfer processes. Differently lead phthalocyanine demetallized during second oxidation reaction while it was stable during reduction processes. An in-situ electrocolorimetric method, based on the 1931 CIE (Commission Internationale de l’Eclairage) system of colorimetry, has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for the first time in this study.     

Novel magnesium and zinc porphyrazines containing galactose moieties: Synthesis via click reaction and characterization

In this study, galactose conjugated new magnesium and zinc porphyrazines were synthesized by the cyclotetramerization reaction of 2,3-bis[1-(2,2,7,7-tetramethyltetra-hydro-bis[1,3]dioxolo[4,5-b;4′,5′-d]pyran-5,methyl)-1H-[1,2,3]triazol-4-yl methylsulfanyl]-but 2-enedinitrile. This substituted dicyano compound was prepared via two different routes. One started from cis-1,2-dicyano-1,2-ethylenedithiolate disodium, [1-(2, 2, 7,7-tetramethyltetrahydrobis[1,3]dioxolo[4,5-b;4′,5′-d]pyran-5-yl-methyl)-1H-[1,2,3]triazo-l-4-yl]methanol and ended in a multi-step reaction sequence via Click procedures. The other reaction was between 5-azidomethyl-2,2,7,7-tetramethyltetrahydro-bis[1,3]dioxolo[4,5-b;4′,5′-d]pyran and (2Z)-2,3-bis(prop-2-yl-1-yl-thio)but-2-enedinitrile. A very soluble galactose linked magnesium porphyrazine derivative in common polar solvents and water was achieved by the deprotected isopropylidene groups in TFA and water media. It is first time, zinc porphyrazine complex has been achieved at one-step reaction by using Zn(BuO)₂ as template agent. The new compounds have been characterized by a combination of elemental analysis, ¹H, ¹³C NMR, IR, UV–vis and MS spectral data.     

Synthesis, electrochemical and spectroelectrochemical characterization of novel soluble phthalocyanines bearing chloro and quaternizable bulky substituents on peripheral positions

A new phthalonitrile derivative (2), bearing diethylaminophenoxy - and chloro-substituents at peripheral positions was synthesized in this work. Cyclotetramerization of (2) in hexanol gave the desired metal-free (4) and metallophthalocyanines (5-8). These new phthalocyanines (4-8) were converted into water-soluble quaternized products by the reaction with methyl iodide (9-11). The novel compounds have been characterized by using elemental analysis, UV-Vis, FT-IR, ¹H NMR and MS spectroscopic data. The aggregation behaviors of the phthalocyanine complexes were studied in different solvents and concentrations. Electrochemical and spectroelectrochemical characterization of the complexes were also performed in solution. Cobalt phthalocyanine gives both metal-based and ring-based reduction processes in comparison to the complexes having 2H⁺, Zn²⁺, Ni²⁺ and Cu²⁺ metal center which give only ring-based reduction processes. Electrochemical and spectroelectrochemical measurements exhibit that all complexes oxidatively electro-polymerize on the Pt working electrode during repetitive cyclic voltammetry measurements. An in-situ electrocolorimetric method was applied to investigate the color of the electrogenerated anionic and cationic forms of the complexes for possible electrochromatic applications.     

The Extraction Ability and Sensitivity of Porphyrazine Derivatives Towards Some Transition Metal Cations

The synthesis of novel metal-free and magnesium porphyrazines, peripherally substituted with dithia-dioxa (S₂O₂) and tetrathia (S₄) 14-membered macrocycles were performed by cyclotetramerization of (6Z)-1,3,4,9,10,12-hexahydro-2,5,8,11-benzo-dioxadithiacyclotetradecine-6,7-dicarbodinitrile (3) or (6Z)-1,3,4,9,10,12-hexahydro 2,5,8,11-benzotetrathiacyclotetradecine-6,7-dicarbodinitrile (5). The metal-free porphyrazines have been obtained by known route. The structure of compounds were characterized by elemental analysis and ¹H, ¹³C NMR, IR, UV-vis, and MS spectral data. The solvent extraction properties of the synthesized compounds towards some metal cations, such as Ag(I), Hg(II), Cu(II), Mn(II), Cr(III), Ni(II), Pb(II), and Zn(II) have been investigated. The effect of Cu²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Sr²⁺, Al³⁺, Zn²⁺, Ba²⁺, Cd²⁺, Co²⁺, Hg²⁺, and Ag⁺ ions on the absorption spectra of the compounds were investigated by means of spectrophotometric method. Magnesium porphyrazine with S₂O₂ (6) interacted within Hg²⁺ ion specifically of all the tested metal ions.     

Novel alpha-7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin substituted metal-free,Co(II) and Zn(II) phthalocyanines: Photochemistry,photophysics, conductance and electrochemistry

Novel alpha-substituted metal-free, Co(II) and Zn(II) phthalocyanines, bearing four 7-oxy-4-(4-methoxyphenyl)-8-methylcoumarin moieties were synthesized. The compounds were characterized by elemental analysis, IR, UV–vis, ¹H NMR, ¹³C NMR and MALDI-TOF mass spectroscopies. The Zn(II) phthalocyanine compound showed J-type aggregation in non-coordinating solvents. The photophysical and photochemical properties of these compounds were described in different solvents. Direct current conductivity measurements of the films of Co(II) and Zn(II) phthalocyanines as a function of temperature showed that these compounds are semiconductors with the activation energies within the range of 0.40–0.84 eV. The variation of alternating current conductivity of the films with frequency was found to be represented by the function σ_AC = Aω^s. The results indicated that charge transport mechanism of the films can be explained by hopping. The redox properties of the compounds were also examined in dimethylsulfoxide and dichloromethane by voltammetry and in situ spectroelectrochemistry. The compounds displayed metal and/or phthalocyanine ring-based reduction and oxidation processes. The electrochemistry of a phthalocyanine compound forming a J-aggregated species has been investigated. It was found that some redox couples of the Zn(II) compound in dichloromethane is split due to the equilibrium between its aggregated and non-aggregated species.     

DFT Quantum-Chemical Modeling Molecular Structures of Cobalt Macrocyclic Complexes with Porphyrazine or Its Benzo-Derivatives and Two Oxygen Acido Ligands

Based on the results of a quantum chemical calculation using the DFT method with the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of three cobalt heteroligand complexes containing in the inner coordination sphere porphyrazine, di[benzo]- and tetra[benzo]porphyrazine, and two oxygen (O²⁻) ions with probable oxidation state VI of Co, which is unknown for this element at the present time, was shown. Data on the structural parameters are presented. It was shown that CoN₄ chelate nodes as well as all metal-chelate and non-chelate cycles in each of these complexes, were strictly planar. Besides, the bond angles formed by two donor nitrogen atoms and a Co atom were close or equal to 90°, while the bond angles formed by donor atoms N, Co, and O, in most cases, albeit insignificantly, differed from this value. Good agreement between the calculated data obtained using the above two versions of the DFT method was found. Standard thermodynamic parameters of formation (standard enthalpy ΔH⁰_{f, 298}, entropy S⁰_{f, 298} and Gibbs’s energy ΔG⁰_{f, 298}) for the indicated complexes were presented too.     

Synthesis and electrochemical and in situ spectroelectrochemical characterization of manganese, vanadyl, and cobalt phthalocyanines with 2-naphthoxy substituents

Metallo (Mn, Co, VO) phthalocyanines bearing peripheral 2-naphthoxy groups were synthesized by cyclotetramerisation of the corresponding phthalonitrile derivative. The phthalocyanine compounds were characterized by elemental analyses, mass, FT-IR and UV–vis spectral data. Three intense bands in the electronic spectra clearly indicate the absorptions resulting from naphthyl groups along with the Q and B bands of the phthalocyanines. Electrochemical and spectroelectrochemical measurements exhibit that incorporation of redox active metal ions, Co^II and Mn^III, into the phthalocyanine core extends the redox capabilities of the Pc ring including the metal-based reduction and oxidation couples of the metal. Presence of molecular oxygen in the electrolyte system affects the voltammetric and spectroelectrochemical responses of the cobalt and manganese phthalocyanines due to the interaction between the complexes and molecular oxygen. Interaction reaction of oxygen with CoPc occurs via an “inner sphere” chemical catalysis process. While CoPc gives the intermediates [O₂⁻–Co^IIPc⁻²]⁻ and [O₂²–Co^IIPc⁻²]²⁻, MnPc forms μ-oxo MnPc species. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications.     

Synthesis and properties of iron(II) tetra(1,4-dithiin)porphyrazine bearing peripheral long-chain alkyl group of active end-bromine

The novel tetra-(1,4-dithiin) metal-free (H₂Pz) and metalloporphyrazines (MPz, M = Mg, Fe) bearing peripheral tetrapropyl-bromine derived from 2,3-dicyano-5-propyl-bromine-1,4-dithiin, were synthesized in a multi-step reaction sequence. These complexes were characterized by ¹H NMR, IR, UV–vis, GC–MS, XPS and elemental analysis and their UV–vis spectra were discussed in detail. The iron(II) tetra-(1,4dithiin)porphyrazine bearing peripheral tetrapropyl-bromine was supported on an Amberlite CG-400 resin to form a biomimetic catalyst, the ability of which for activating O₂ and H₂O₂ was estimated from the degradation of Rhodamine B (RhB) under visible light irradiation (λ ? 420 nm). More than 70% of the RhB was degraded by O₂ in air for 24 h in the solution of pH 9.18 and by H₂O₂ only for 12 h in the solution of pH 3.0.     

Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties (2Ni and 3Ni) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni^II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni^II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl⁻ anions to the coordinated Ni^II in 2Ni and 3Ni resulted in an appreciable shift of both Ni^II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu^II complexes.     

Synthesis, Spectral, Morphology, Thermal Degradation Kinetics and Antibacterial Studies of Terpolymer Metal Complexes

Terpolymer metal complexes involving transition metal ions such as Cu(II), Mn(II) and Zn(II) were prepared using a terpolymer ligand derived from anthranilic acid–phenyl hydrazine–formaldehyde (APHF). The terpolymer ligand and its metal complexes were intended to spectral characterizations viz. FTIR, electronic, ESR, ¹H NMR and ¹³C NMR to elucidate the structural confirmations. The number, weight, and size average molecular weights of the terpolymer ligand were determined by gel permeation chromatography (GPC). The empirical formula of the repeating unit for both the terpolymer ligand and its metal complexes was clearly justified by elemental analysis. The thermal stability of the ligand and its metal complexes was established by thermogravimetric analysis (TGA). On basis of the TGA data, the kinetic and thermodynamic parameters such as activation energy (E _a), order of reaction (n), entropy change (ΔS), apparent entropy (S*), frequency factor (Z) and free energy change (ΔF) were calculated using Freeman–Carroll and Sharp–Wentworth methods. Further the degradation mechanism for the thermal decomposition was also identified from Phadnis–Desphande method. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to establish the surface morphology and nature of the terpolymer ligand and its metal complexes. In addition, the terpolymer ligand and its metal complexes were screened against the growth of few bacteria and their inhibitions were measured and reported.     

Chelating ability of a conjugated redox active tetrathiafulvalenyl-acetylacetonate ligand

A novel tetrathiafulvalene (TTF) bearing a conjugated β-diketone moiety (TTFacacH) has been synthesized and fully characterized. The chelating ability of its enolate anion (TTFacac) has been investigated with [M^II(OAc)₂ · xH₂O] (OAc = acetate and M = Zn, Cu and Ni) leading to complexes, where the metal center is coordinated by two TTFacac. Modulation of the redox properties of the TTF can be achieved through the simple change of the two apical ligands which completed the octahedral coordination geometry. This redox active ligand shows promising features for the elaboration of hybrid organic–inorganic building blocks.     

Nickel complexes bearing 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines: Synthesis,structure and catalytic ethylene oligomerization

A series of 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines was synthesized and characterized. They are stable as solids while displaying a tendency to decompose in solution. On reaction with NiCl₂, different coordination pattern sets of L·NiCl₂ or [L₂Ni]²⁺·2Cl⁻ are obtainable in THF or ethanol. When activated by Et₂AlCl, the complexes L·NiCl₂ exhibit good to high catalytic activities and selectivities for 1-C₄ in ethylene oligomerization, while the complexes [L2Ni]²⁺·2Cl⁻ hardly showed any activity, which is attributable to nickel coordination by two ligands barring interaction of ethylene with the metal center.     

Triphenylamine substituted dipyrrinato metal complexes: Synthesis,optical and electrochemical studies

A series of triphenylamine substituted dipyrrinato metal complexes (1–8) have been synthesized. The mononuclear type complexes 1–6 have Ni(II), Co(II), Pd(II), In(III), and Zn(II) metal ions in the core. The binuclear type complexes 7 and 8 have Zn(II) metal ion in the center. All the compounds (1–8) were characterized by HRMS, NMR, IR, UV–vis absorption, cyclic voltammetry and fluorescence techniques. The presence of large electron rich triphenylamine moiety at dipyrrin ligands affected the spectral properties of complexes. Except Co(II) complex, other metal complexes exhibited blue shifted absorption maxima in UV–vis studies. The In(III) and Zn(II) metal complexes 4–6 showed red shifted emission maxima in fluorescence compared to their corresponding phenyl analogues. Complexes 3–8 exhibited good Stokes shifts in the range of 4600 to 7000 cm^− 1 with reduced quantum yields. Singlet state lifetimes of complexes 3–8 were in the range of 2 to 4 ns; also the decrease in radiative decay constants k_r and the increase in non-radiative decay constants k_nr were in line with the quantum yield data. CV studies of complexes 1–8 showed anodic shifts in the oxidation potentials, suggesting that meso-triphenylamine group has affected the electronic properties of complexes by making them difficult to oxidize.     

Lewis acidic complexes of platinum(II): a mechanistic study of the Baeyer–Villiger oxidation of methylcyclohexanone with hydrogen peroxide catalyzed by [(triphosPO)Pt]2+ species

A kinetic study of the Baeyer–Villiger epoxidation of methylcyclohexanone with 35% hydrogen peroxide catalyzed by [(triphosPO)Pt(CH₂Cl₂)]²⁺ is reported based on initial rate analysis. The mechanism suggested involves coordination of the ketone to the coordinatively unsaturated complex, followed by nucleophilic attack of free hydrogen peroxide. The importance of the Lewis acid character of the metal center is crucial in promoting the activation of the substrate as well as its ability to facilitate the leaving of the otherwise bad OH⁻ leaving group from the intermediate quasi-peroxymetallacycle.