Tetrapyrazinoporphyrazines and their metal derivatives. Part I: Synthesis and basic structural information

Tetra(pyrazino[2,3-b]pyrazino)porphyrazines: Synthesis, absorption, photophysical and electrochemical properties of strongly electron-deficient macrocycles

Highly electron deficient 6,7-disubstituted (tert-butylsufanyl, 2,6-diisopropylphenoxy, diethylamino, 2-pyridyl, 2-thienyl, 2-furyl) pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles were prepared and attempted in cyclotetramerization to corresponding tetra(pyrazino[2,3-[Formula: see text]]pyrazino)porphyrazines (TPyzPyzPzs). Only the template reaction in pyridine with zinc acetate and only for the compounds substituted with tert-butylsulfanyl or 2,6-diisopropylphenoxy substituents resulted in efficient cyclotetramerization. Absorption spectra of these zinc TPyzPyzPzs indicated considerable blue shift of the main absorption Q-band ([Formula: see text] 693 nm and 669 nm in pyridine for tert-butylsulfanyl or 2,6-diisopropylphenoxy derivatives) when compared to other aza-analogs of naphthalocyanines. Photophysical parameters ([Formula: see text] [Formula: see text] 0.25, [Formula: see text] [Formula: see text] 0.65) seemed to be unaffected by change of the macrocycle core and only slightly by different peripheral substituents in agreement with heavy-atom effect. Electrochemical data revealed strong electron-deficient character of hetaryl disubstituted pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles. The first reduction potentials of tert-butylsulfanyl or 2,6-diisopropylphenoxy substituted zinc TPyzPyzPzs were even more cathodically shifted when compared to their corresponding pyrazino[2,3-[Formula: see text]]pyrazino-2,3-dicarbonitriles. TPyzPyzPzs represent an example of the strongest electron-deficient core among the phthalocyanines, naphthalocyanines and their aza-analogs.

DFT Study of molecular and electronic structure of magnesium (II) tetra(1,2,5-chalcogenadiazolo) porphyrazines, [TXDPzMg] (X = O, S, Se, Te)

The influence of the chalcogen atom (X) on the molecular and electronic structures for the series of Mg[Formula: see text] tetra(1,2,5-chalcogenadiazolo)porphyrazines [TXDPzMg] (X [Formula: see text] O, S, Se, Te) and their monoaqua complexes [TXDPzMg(OH[Formula: see text]] was studied using DFT methods (B3LYP and PBE0 functionals) with cc-pVTZ basis sets. The chalcogen atom X changes strongly the geometry of the fused 1,2,5-chalcogenadiazole rings, but has only a weak influence on the dimensions of the coordination cavity of the porphyrazine macrocycle in [TXDPzMg] leading to its slight expansion in the sequence S < Se < Te < O. The electron density distribution was considered in terms of the natural bond order (NBO) and the natural population analysis (NPA). The frontier molecular orbitals are destabilzed along with the decrease of electronegativity of the chalcogen atoms. The a[Formula: see text] and e[Formula: see text] orbitals (HOMO and LUMO) are mainly localized on atoms constituting the internal 16-membered macrocycle, while the chalcogen atoms have the strongest effect on the composition of the filled [Formula: see text]-MOs having the a[Formula: see text] symmetry – 2a[Formula: see text] and lower lying 1a[Formula: see text] orbitals. The Gouterman type a[Formula: see text] orbital with predominant localization on the nitrogen atoms of the internal 16-membered macrocycle is 2a[Formula: see text] for the O- and S-containing complexes and for the Se- and Te-analogs it becomes 1a[Formula: see text], while the higher lying 2a[Formula: see text] orbital resides mainly on the fused heterocycles (Se/Te and C[Formula: see text] atoms). The lowest excited states have been calculated for [TXDPzMg] and used for the explanation of the peculiarities and tendencies observed in the experimental electronic absorption spectra available for the S, Se- and Te-containing Mg[Formula: see text] complexes.

Synthesis and singlet oxygen generation of pyrazinoporphyrazines containing dendrimeric aryl substituents

Singlet oxygen generation yields and aggregation tendencies were studied for porphyrazines bearing dendrimeric substituents.

Photoelectrocatalytic degradation of partially hydrolyzed polyacrylamide using a novel particle electrode

Tetrapyrazinoporphyrazines and their metal derivatives (TPyzPzs) are the most widely studied class of phthalocyanines azaanalogues.

Radical anion and dianion salts of titanyl macrocycles with acceptor substituents or an extended π-system

Crystalline anionic salts of titanyl macrocycles: (PPN⁺)₂{OTi^IV(PcCl₈⁴⁻)}²⁻ (1), (PPN⁺){OTi^IV(Nc˙³⁻)}˙⁻·solv (2) and (PPN⁺)₂{OTi^IV(AceTPrzPz⁴⁻)}²⁻·solv (see figure, 3) have been obtained and their optical and magnetic properties are studied.

OFF-ON-OFF Red-Emitting Fluorescent Indicators for a Narrow pH Window

A unique combination of two independent mechanisms of fluorescence quenching, namely intramolecular charge transfer (ICT) from a peripheral donor and protonation of azomethine nitrogen atoms in zinc tetrapyrazinoporphyrazines (TPyzPz), provides a new possibility for sensing pH in a specific range. The pH selectivity was controlled by the different basicities of the donor for ICT (dimethylaminoaryl), which was connected to the macrocycle by π-extended linkers of different lengths. ICT and protonation have been studied in detail by photophysical, spectral (UV/Vis and MCD spectra), and electrochemical measurements, and further supported by theoretical calculations (DFT, TDDFT). The pH-sensing properties of the TPyzPzs have been investigated in THF and in water after anchoring the TPyzPzs to liposomes. The salient pK_a values were around 1.3 (azomethine nitrogen) and 2.29-4.76 (donor for ICT). The lead indicators (sensing over a pH range of 1.0-2.5) with fairly steep sensing profiles exhibited increases in fluorescence between the OFF/ON states of more than 20-fold and strong absorption in the red region (Q-band maximum >650 nm, ϵ≈2×10⁶  m^-1  cm^-1 ).

Optical, electrochemical and third-order nonlinear optical studies of triphenylamine substituted zinc phthalocyanine

Zinc phthalocyanine possessing triphenylamine at its peripheral position has been synthesized and its optical, emission, electrochemical and third-order nonlinear optical (NLO) properties were investigated. Soret band was broadened due to the presence of triphenylamine moiety. Electrochemical properties indicated that both oxidation and reduction processes were ring centered. Emission spectra were recorded in different solvents and the fluorescence yields obtained were in the range of 0.02–0.17 while the time-resolved fluorescence data revealed radiative lifetimes of typically few ns. Third-order NLO properties of this molecule have been examined using the Z-scan technique with picosecond (ps) and femtoseocnd (fs) pulses. Closed and open aperture Z-scan data were recorded with 2 ps/1 50 fs laser pulses at a wavelength of 800 nm and NLO coefficients were extracted from both the data. Our data clearly suggests the potential of this molecule for photonics applications.

Anionic hexadeca-carboxylate tetrapyrazinoporphyrazine: synthesis and in vitro photodynamic studies of a water-soluble, non-aggregating photosensitizer

Photodynamic activity of hexadeca-carboxylate tetrapyrazinoporphyrazine is largely influenced by intracellular pH and its interaction with serum proteins.