Synthesis, structure, spectroscopic properties, and electrochemical behavior of mixed ligand bis(β-ketoesterato)zirconium (IV) and -hafnium (IV) phthalocyaninates

The synthesis of new zirconium and hafnium mixed ligand phthalocyanine complexes PcM(β-ketoester)₂, where M-Zr (IV), Hf (IV); Pc - the dianion of phthalocyanine, and β-ketoester - the out planed ligand, is reported. The obtained complexes are characterized by ¹H NMR, IR, UV-Vis spectroscopy and cyclic voltammetry. ¹H NMR and elemental analysis confirm the substitution of two Cl atoms for two β-ketoester fragments to the central atom of the macrocycle. The data of ¹H NMR, UV-Vis spectroscopy have allowed us to conclude that two β-ketoester ligands are in the cis geometry to the phthalocyanine plane. X-ray crystallography for bis(isopropyl 3-oxobutanoato)hafnium(IV)phthalocyanine confirms this conclusion. The central macrocycle of the phthalocyanine ligand is not exactly planar (deviations from the least-square plane exceed 0.15 Å) and has the conformation of an essentially flattened crown. The Hf(1) atom is 1.349(3) above this least-square plane. Cyclic voltammetry investigation shows that the introduction of two β-ketoester ligands to the central atom of phthalocyanine complex leads to both chemical and electrochemical stabilization of the whole Pc system.     

Synthesis and characterization of novel symmetrical phthalocyanines substituted with four benzo [d] [1, 3] dioxol-5-ylmethoxy groups

Metal (Zn, Cu, Co, Mg) phthalocyanines substituted with four benzo [d] [1, 3] dioxol-5-ylmethoxy unit through oxy-bridges have been synthesized from phthalonitrile derivative, 4-(benzo [d] [1, 3] dioxol-5-ylmethoxy) phthalonitrile. Benzo [d] [1, 3] dioxol-5-ylmethoxy substituted Pcs showed the enhanced solubility in organic solvents. The newly prepared compounds have been characterized by elemental analyses, IR, UV-Vis, ¹H NMR spectra.     

Thermodynamics of Interaction of Phthalocyanine‐Oligonucleotide Conjugates with Single‐ and Double‐Stranded DNA

Thermodynamics of interaction of phthalocyanine‐oligonucleotide conjugates with single‐ and double‐stranded DNA resulting in formation of duplexes and triplexes was measured by UV melting method. It was shown that a phthalocyanine moiety of conjugates stabilized the formation of duplexes and triplexes.     

Synthesis, characterization and investigation of electrical and electrochemical properties of imidazole substituted phthalocyanines

Compound 1 has been synthesized by the reaction of 4-nitrophthalonitrile and 4,5-diphenyl-1H-imidazolethiole in DMSO in the presence of K₂CO₃. Compound 2 has been synthesized by heating compound 1 with metallic lithium in pentanol and hydrolyzed with hydrochloric acid (10%) and then neutralized with ammonia solution. Compound 3 and 4 have been synthesized by heating 1 with ZnCl₂ or CoCl₂ in DMF in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), respectively. The new compounds were obtained in sufficient purity after successive washing with different solvents and were characterized by elemental analysis, ¹H NMR, ¹³C NMR, UV-vis, IR and mass spectra. We also studied aggregation behavior, electrochemical and electrical properties of these phthalocyanines. Direct current (dc) and alternating current (ac) conductivity (40-100 kHz) measurements of films of 2, 3 and 4 were performed in the temperature range of 295-523 K. Impedance spectra (IS) of the 2, 3 and 4 were also studied. The conduction processes were discussed. Temperature dependence of dc conductivity of the films revealed that 2, 3 and 4 show a semiconductor behavior. Results of ac measurements showed that, conduction processes of the films of the complex consisted of different mechanisms depending on temperature and frequency.     

Synthesis of diiodo butadiynyl-bridged bisphthalocyaninatozinc(II) complexes

Two functionalized phthalocyanine-based chromophore systems having two iodophthalocyaninatozinc(II) rings bound together through a butadiynyl linkage 1a,b have been synthesized by oxidative Eglinton coupling of the corresponding monomer, and fully characterized. The electronic characteristics of these extensively linearly pi-conjugated compounds were modulated by the introduction of different peripheral substituents into the phthalocyanine moieties and investigated by UV-visible spectroscopy. The reactivity of the two iodo substituents was explored to prepare a novel bisphthalocyanine containing two ethynylphenyl moieties, thus pointing out the possibility of incorporating other electro and/or photoactive moieties in the BisPc system, taking advantage of the iodo-functionalization.     

Tetra(β-phenothiazinyl) zinc phthalocyanine: An easily prepared D4-A system for efficient photoinduced electron transfer

Four identical electron donor (D) moieties, phenothiazines (PTZs), were covalently attached onto the same acceptor (A), zinc phthalocyanine (ZnPc), to form ZnPc(β-PTZ)₄, i.e. D₄-A. The symmetrical D₄-A was synthesized by the condensation method to examine intra-molecular photoinduced electron transfer (PET). The common electron donor-spacer-acceptor (D-A) photosynthetic models, which involve the asymmetrical synthesis of a mono-substituted porphyrin or its analogs, suffer from a low yield and arduous isolation, since D-A is only one of several products (D_n-A or A_n-D, n = 0, 2-4). The D₄-A preparation, however, can be carried out without the problem. The steady state and time-resolved fluorescence of the D₄-A were measured and compared with that of ZnPc(β-R)₄ (R = H, OPh). The result showed that the excited singlet state of phthalocyanine moiety in the D₄-A molecule was efficiently quenched by phenothiazine units owing to intra-molecular PET. The rate constant of PET (k_et) was calculated and the value is much higher than the rate constant of fluorescence emission, intersystem crossing and internal conversion of ZnPc moiety. The laser flash photolysis study revealed the presence of a long-lived charge-separated state due to PET. The results suggest that a D₄-A system can be a more efficient artificial photosynthetic model than D-A towards the practical commercial use.     

Re-examination of the emission properties of alkoxy- and thioalkyl-substituted phthalocyanines

The role of n → π^∗ transitions in the optical spectra of alkoxy- and thioalkyl-substituted phthalocyanines with peripheral substituents is re-examined, based on a detailed analysis of UV-visible absorption, magnetic circular dichroism (MCD) and fluorescence emission spectral data and the results of density functional theory (DFT) and time dependent-density functional theory (TD-DFT) calculations. The nπ^∗ excited states associated with the lone pairs of the peripheral heteroatoms have been proposed as the origin of a second emission peak observed in the 400-600 nm region, which has been assigned as S₂ emission, since S₁ fluorescence associated with the Q band is observed in the near IR region. Our results demonstrate that emission from a photodecomposition product can fully account for this violet emission and that reports of S₂ emission for peripherally substituted phthalocyanines and porphyrazines should be treated with caution.     

Comparing a thioglycosylated chlorin and phthalocyanine as potential theranostic agents

Herein we describe the design, efficient synthesis, and photophysical properties of two macrocycle dyes for cancer theranostics. This study compares a glycosylated chlorin with a glycosylated phthalocyanine designed to specifically target cancer, wherein the photophysical properties enable both fluorescence imaging and the sensitization of the formation of reactive oxygen species (ROS) for photodynamic therapy. Both the compounds show low darktoxicity (IC₅₀ > 100 μM). The glycosylated phthalocyanine showed low phototoxicity (IC₅₀ > 100 μM) while glycosylated chlorin showed high phototoxicity (IC₅₀ = 1–2 μM). ZnPcGlc₈ has low solubility and also form aggregates in aqueous media, thus resulting in minimal uptake in two different human breast cancer cell lines: MDA-MB-231 and MCF-7. The glycosylated chlorin however was efficiently taken up by these two cell lines, thus allows fluorescence imaging in cells and in xenograft tumor model in mice. In this study, we find that the chlorin conjugate is the more promising theranostic agent.     

Amido functional phthalocyanines as metal ion sensor; synthesis, characterization, spectroscopy, electrochemistry, in-situ spectroelectrochemistry

Tetrasubstituted metal ion sensor amido functional phthalocyanines, PyMA-MPc, {PyMA: [N¹,N³-bis(pyridin-2-ylmethyl)malonamide], M = Pd(II), Cu(II) and Co(II)} bearing amido functionality on the periphery were synthesized from the corresponding tetrasubstituted diethylmalonate substituted phthalocyanines, DEM-MPc (DEM: diethylmalonate; M = Pd(II), Cu(II) and Co(II)), and 2-aminopyridine in N,N-dimethylaminoethanol (DMAE) solvent. The new complexes have been characterized by elemental analysis, FT-IR, ¹H NMR and mass spectra. Peripheral malonamide groups of the phthalocyanine complexes serve as exocyclic binding sites for metal ion, such as Pd^II and also increase the solubility in protic solvents, i.e MeOH. Protonation of the pyridyl groups with HCl formed quaternized salts of the MPc, N¹,N³-bis(pyridin-2-ylmethyl)malonamide substituted metallophthalocyanines (PyMA-PdPc×8HCl) which are freely soluble in aqueous media. Methylation of M[Pc(CH(COOC₂H₅)₂)₄] with CH₃I gave the octacationic 2(3),9(10),16(17),23(24)-tetrakis-[N¹,N³-bis(N-methylpyridin-2-ylmethyl)malonamide]-phthlocyaninato Cu(II) salts which are freely soluble in water. Voltammetric and spectroelectrochemical studies show that while PyMA-Pd(II)Pc and PyMA-Cu(II)Pc give ring-based reversible/quasi-reversible redox processes, PyMA-Co(II)Pc give both metal and ring-based, reversible/quasi-reversible electron transfer processes.     

Electrooptical behavior of heme-like molecules adsorbed on nerve membrane

This paper discusses the electrooptical properties of iron tetrasulfonated phthalocyanine (Fe-TsPc) adsorbed on a nerve membrane. The study is based on a comparative analysis of the properties of an aqueous solution of Fe-TsPc and the properties of Fe-TsPc adsorbed on a silver electrode. The resonant Raman spectra were obtained from the adsorbed Fe-TsPc on the interfaces of a silver electrode and the nerve membrane. Considerable optical signal changes have been observed when the interfacial potential is altered. The Raman spectra are sufficiently sensitive to indicate the submolecular mechanisms of electron delocalization. The changes in Raman signals as a function of the interfacial potential provide a means for optically monitoring electrical excitability in nerve.