Heavy metal effects on physicochemical properties of non-aggregated azaphthalocyanine derivatives

Abstract

Two series of peripherally substituted azaphthalocyanines (AzaPcs) containing different transition metals ( Al(III), Zn(II), Ga(III), In(III) and Fe(II) ) were synthesized and studied for their photophysical properties. As confirmed by UV-vis and1H NMR analyses, the non-aggregation behavior was effectively induced by the applied bulky peripheral substituents which had no effect on the photophysical properties. Tuning the Q-band position was clearly achievable by using different central heavy metals which have considerable effects on the fluorescence quantum yield and singlet oxygen generation efficiency. This comparative study showed an interesting linear relationship between the former and atomic number of the central metal. The indium containing complexes exhibited the best result due to the heavy metal effect and therefore could be promoted as a potential photosensitizer in photodynamic therapy (PDT) application.

Peripheral substitution as a tool for tuning electron-accepting properties of phthalocyanine analogs in intramolecular charge transfer

“…The sum is typically constant for various macrocycles even though the ratio between the fluorescence and singlet oxygen production may vary depending on various structural factors (e.g., heavy atom effect). 31,32 This fact was confirmed also in the current study for symmetrical s1Zn, s2Zn, s4Zn and s5Zn. Their sum of Φ Δ + Φ F reached comparable values (approximately 0.83).…”

Structural factors influencing the intramolecular charge transfer and photoinduced electron transfer in tetrapyrazinoporphyrazines

“…The magnesium complexes were always characterized by F F values that were greater than those of the corresponding zinc complexes, which is consistent with a number of previous observations of TPyzPzs and is explained by the heavy-atom effect. 17,21 The heavy-atom effect supposes that substitution with heavier atoms increases the probability of intersystem crossing and thus decreases the photon emission from the first excited state. 22 Singlet oxygen production was determined via the chemical trapping of singlet oxygen by DPBF with ZnPc as the reference compound.…”

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

“…Interestingly, all X-ray characterized 2-thienyl substituted dinitriles have coplanar arrangement of one of 2-thienyl rings (see also It is noteworthy that if the phenolic -OH group is extremely sterically hindered by the adjacent substituents, the C-nucleophilic substitution of the chlorine atoms in Pyz53 can occur (Scheme 18; right) instead of the usual O-nucleophilic reaction (Scheme 18; left). Thus, while 2,6-diisopropylphenol (as well as 2,6-diphenylphenol) gave the products of O-substitution (Pyz65,Pyz69) [145,146,160], the C-substitution products (disubstituted Pyz84a and monosubstituted Pyz84b) were obtained under similar conditions in the case 2,6-di(tert-butyl)phenol [161]. The structure of the products of the consecutive C-substitution of the two chlorine atoms (Scheme 18; right) was confirmed by single crystal X-ray diffraction and indicated full coplanar structure for the monoarylated derivative Pyz84b and rotation out of the plane for the diarylated Pyz84a (Fig.…”

“…Metal free, Zn II , Co II and Ni II complexes bearing eight 2,6-diisopropyl [TPyz65PzM] or 2,6-diphenyl [TPyz69PzM] substituted aryloxy groups (Chart 15) were obtained by direct heating of the corresponding dinitriles in quinoline (metal free, yield 40%) M a n u s c r i p or in quinoline in the presence of the corresponding metal acetates in yields typically close to 55% [145,146]. The procedure was subsequently used for the synthesis of a number of metal complexes of derived TPyzPz bearing bulky substituents in 2,6-positions that efficiently prevent aggregation in organic solvents ([TPyz66PzM] - [TPyz68PzM], Chart 15, Table 7) [150,151,153,160,229]. Interestingly, the hydroxy substituted derivative [TPyz67bPzZn] was not obtained by direct cyclotetramerization of the corresponding precursor, but cleavage of the methoxy groups in [TPyz67aPzZn] by BBr 3 was employed instead [153].…”