Azaphthalocyanines Containing Pyrazine Rings with Focus on the Alkylheteroatom, Aryl and Heteroaryl Substitution and Properties Important in Photodynamic Therapy

Abstract

In this work, we summarize the recent knowledge about the syntheses, UV-vis absorption properties, aggregation, protonation and deprotonation of macrocycle and singlet oxygen and fluorescence quantum yields in the group of azaphthalocyanines bearing pyrazine rings in their conjugated system. Precursors (pyrazine-2,3-dicarbonitriles) for tetramerization are usually built up by condensation from aliphatic starting materials thus enabling peripheral substitutions sometimes not available for phthalocyanines (Pc). Conditions of tetramerizations are discussed in the article too. Although tetrapyrazinoporphyrazines (TPyzPA) suffer from the hypsochromic shift comparing to corresponding Pc, several types of peripheral substituents can induce important bathochromic shift and eliminate this disadvantage. TPyzPA macrocycle tends to higher aggregation comparing to Pc molecules and a lot of aggregation inhibiting substituents have been developed. Protonation of the TPyzPA macrocycle in acidic media starts on azomethine nitrogens and at higher concentrations of acid also pyrazine nitrogens accept the proton. The central hydrogens in metal-free compounds are acidic (N-acids) and the macrocycle can be deprotonated in basic solutions. Singlet oxygen production as well as fluorescence emission are strongly dependent on peripheral substituents, namely on the heteroatoms connecting the core with the substituents.

Synthesis and X-Ray Crystal Structure of 1',7',7'-Trimethylbicyclo[2.2.1]heptane[2',3'-b]-2,3-dicyanopyrazine

“…[10] 5,6-Alkyl-and 5,6-aryl substituted pyrazines and their derivatives, such as 2,3-dichloroquinoxaline-6,7-carbonitrile, were obtained by condensation with diaminomaleonitrile in methanol, using acetic [11] or hydrochloric [12] acids as a catalyst. Synthesis of 5,6-bis(1H-pyrrol-2-yl)pyrazine-2,3-dicarbonitrile with a 55 % yield in dichloromethane, using BF 3 as a catalyst, was described.…”

Tetra[6,7]quinoxalinoporphyrazines: The Effect of an Additional Benzene Ring on Photophysical and Photochemical Properties

“…Aliphatic alkyls do not contribute to a redshift and compounds with such modification usually absorb at the same wavelength as unsubstituted macrocycles. [31,32] TQP2 can be therefore considered as the standard for comparison. The butoxycarbonyl groups of TQP1 shifted the position of the Q-band significantly bathochromically due to the strong conjugation of the carbonyl group with the π-system of the TQP core.…”

Synthesis of Iron(II) Octachlorotetrapyrazinoporphyrazine, Molecular Structure and Optical Properties of the (X−)2FeTPyzPACl8 Dianions with Two Axial Anionic Ligands (X− = CN−, Cl−)

“…[25,26,34] We use commercially available 1,2-dichloro-4,5-dicyanopyrazine from TCI. Synthetic procedure was modified using 1-chloronaphthalene as solvent and iron(II) acetylacetonate as a source of iron.…”

“…[21,[28][29][30][31] Molecular structure of pyridine substituted tetrapyrazinoporphyrazine is determined by single-crystal X-ray analysis for cobalt(II) tetrakis[5,6-di(2-pyridyl)-2,3-pyrazino}porphyrazine, Co II TPyzPAPy 8 . [15] Substituted tetrapyrazinoporphyrazines are used in cancer and photodynamic therapy, [32][33][34] as components for capacitors, [35] and their nonlinear properties are analyzed. [29] In this work we developed a simple method to synthesize iron(II) octachlorotetrapyrazinoporphyrazine, FeTPyzPACl 8 (1), bearing eight electron-withdrawing chlorine substituents attached to the electron deficient tetrapyrazinoporphyrazine macrocycle.…”