Reducing zirconium(IV) phthalocyanines and the structure of a Pc(4-)Zr complex.

The synthesis and characterization of the ring-unsubstituted zirconium phthalocyanine PcZrCl2 (; Pc(x-) = phthalocyaninato(x-)) and its reduction products are described. X-ray analysis of (crystallized from hot 1-chloronaphthalene) reveals that is a chloride-bridged dimer [PcZrCl]2(µ-Cl)2 in the solid-state; was also characterized by UV-vis/MCD spectroscopy and cyclic voltammetry, which indicated reduction potentials at -0.55, -0.95 and -1.28 V. Although attempts to access these Pc-ring reduced species with KC8 led to mixtures of reduced products due to the insolubility of both starting materials, one equivalent of the reducing agent KEt3BH reacted with to generate Pc(3-)-containing species, as indicated by visible Q-band spectral changes (from λmax = 686 for to 589/611 nm), a single ESR peak (g = 2.001) and paramagnetically shifted (1)H NMR resonances consistent with the presence of a Pc-radical anion. Addition of two equivalents of KEt3BH to generated Pc(4-)-containing species, confirmed by a shift in λmax to 522 nm and upfield-shifted (1)H NMR peaks relative to . Reaction of with one and two equivalents of LiCp* did not generate Cp*-substituted products but also effected reduction to analogous Pc(3-) and Pc(4-) species. This latter material, the air-sensitive ring di-reduced "ate"-complex Pc(4-)Zr(LiCl)1.5(DME)3, of the form [LiCl(DME)4]0.5[Pc(4-)ZrClLi(DME)] was structurally characterized, illustrating partial bond localization in the Pc(4-) ring, which also adopts a saddle-shape vs. the more typical dome-configuration found in . This represents a rare example of an isolated and structurally characterized Pc(4-) complex.

Metallophthalocyanin-ocenes: scandium phthalocyanines with an η(5)-bound Cp ring.

A series of new scandium complexes supported by the phthalocyanine (Pc) ligand have been prepared and structurally characterized. Reaction of ScCl3 with phthalonitrile affords a mixture of PcScCl (1) and unreacted ScCl3, which upon addition of LiCH(SiMe3)2 yields THF-soluble PcSc(µ-Cl2)Li(THF)2 (2). Metathesis with NaCp or LiCp* generates PcSc(η(5)-C5H5) and PcSc(η(5)-C5Me5), respectively, which represent the first examples of η(5)-Cp metal phthalocyanines where the Cp fragment sandwiches the metal centre.

Synthesis of new chlorin†e6 trimethyl and protoporphyrin†IX dimethyl ester derivatives and their photophysical and electrochemical characterizations.

In view of increasing demands for efficient photosensitizers for photodynamic therapy (PDT), we herein report the synthesis and photophysical characterizations of new chlorin e6 trimethyl ester and protoporphyrin IX dimethyl ester dyads as free bases and Zn(II) complexes. The synthesis of these molecules linked at the ß-pyrrolic positions to pyrano[3,2-c]coumarin, pyrano[3,2-c]quinolinone, and pyrano[3,2-c]naphthoquinone moieties was performed by using the domino Knoevenagel hetero Diels-Alder reaction. The α-methylenechromanes, α-methylenequinoline, and ortho-quinone methides were generated in situ from a Knoevenagel reaction of 4-hydroxycoumarin, 4-hydroxy-6-methylcoumarin, 4-hydroxy-N-methylquinolinone, and 2-hydroxy-1,4-naphthoquinone, respectively, with paraformaldehyde in dioxane. All the dyads as free bases and as Zn(II) complexes were obtained in high yields. All new compounds were fully characterized by 1D and 2D NMR techniques, UV/Vis spectroscopy, and HRMS. Their photophysical properties were evaluated by measuring the fluorescence quantum yield, the singlet oxygen quantum yield by luminescence detection, and also the triplet lifetimes were correlated by flash photolysis and intersystem crossing (ISC) rates. The fluorescence lifetimes were measured by a time-correlated single photon count (TCSPC) method, fluorescence decay associated spectra (FDAS), and anisotropy measurements. Magnetic circular dichroism (MCD) and circular dichroism (CD) spectra were recorded for one Zn(II) complex in order to obtain information, respectively, on the electronic and conformational states, and interpretation of these spectra was enhanced by molecular orbital (MO) calculations. Electrochemical studies of the Zn(II) complexes were also carried out to gain insights into their behavior for such applications.

An exemplary relationship between the extent of cofacial aggregation and fluorescence quantum yield as exhibited by quaternized amphiphilic phthalocyanines.

The aggregation equilibrium of a series of positively-charged water-soluble phthalocyanines (Pcs) was studied in aqueous solution by means of absorption and fluorescence techniques. The aggregation equilibrium in water depends on the bridging atoms between the pyridyl groups and the Pc core, and on the central metal of the Pcs, while N-alkyl groups are virtually uninvolved in the aggregation properties. Thus, in the water-methanol mixture, the aggregation tendency increased in the order of Zn < Cu ≤ Ni, Pd when the ligand is the same, while the bridging element sulfur gives much more propensity for aggregation compared to oxygen. The fluorescence quantum yields of the Pcs showed an excellent correlation with the extent of aggregation.