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Synthesis and photophysical properties of tetra- and octasubstituted phosphorous oxide triazatetrabenzcorrole photosensitizers.

Antunes EM, Nyokong T - Met Based Drugs (2008)

Bottom Line: The Q band absorption spectra of the complexes are red-shifted compared to unsubstituted PTBC.The latter complex shows a large triplet lifetime (1.7 milliseconds), higher than for MPc derivatives.The chlorinated derivatives show good triplet yields (Phi(T) approximately 0.46 and 0.36) and relatively long lifetimes (256 and 452 microseconds), respectively, for 11 and 13.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Rhodes University, Grahamstown 6140, South Africa.

ABSTRACT
The synthesis of phosphorous oxide triazatetrabenzcorroles (TBC) tetra- (9, 11) or octa- (13) substituted on the ring with halogenated functional groups is reported. The complexes are not aggregated in dimethylsulfoxide (DMSO) and show solubility in solvents such as pyridine. The Q band absorption spectra of the complexes are red-shifted compared to unsubstituted PTBC. The latter complex shows a large triplet lifetime (1.7 milliseconds), higher than for MPc derivatives. The chlorinated derivatives show good triplet yields (Phi(T) approximately 0.46 and 0.36) and relatively long lifetimes (256 and 452 microseconds), respectively, for 11 and 13.

No MeSH data available.


Related in: MedlinePlus

Spectrum of metal-free Pc (10) and transformation upon formationof PTClTBC (11) in DMSO. Concentration = 3.59 × 10−5 mol dm−3.
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fig1: Spectrum of metal-free Pc (10) and transformation upon formationof PTClTBC (11) in DMSO. Concentration = 3.59 × 10−5 mol dm−3.

Mentions: TBC complexes havedistinct UV-Vis spectra with a sharp peak at ~450 nm [16–19], which can beemployed in their characterization. Theformation of the TBC complexes occurs when the MPc molecules no longer retainsa Pc moiety as they no longer have the fourth azomethine nitrogen (see Schemes 1 and 2).It is believed [11] that in the presence of excess metal halide, the bridgenitrogen of the Pc is eliminated, forming TBC. In this study, the unmetallated Pc derivatives(8, 10 and 12) were formed first,which, upon reaction with PBr3, resulted in the formation of PTBCderivatives. This was judged spectroscopically by the collapse of the sharp Qband in the visible region of unmetallated Pcs to three bands (in the Q bandregion), together with the formation of the sharp Soret band at 440 nm (see Figure 1). The spectra of unmetallated Pcs 6, 8, 10, and 12 in DMSO and pyridineshowed a single Q band (see Figure 1) which is uncharacteristic of unmetallatedPcs. Typically, unmetallated Pcs show a split Q band due to lack ofsymmetry. Solvation in polar aproticsolvents (such as DMSO and pyridine) occurs through their unsharedelectrons. Thus, in DMSO (see Figure 1)and pyridine, the spectra of 8, 10, and 12 did not show the normal splitting of the Qband that is typical of free-base phthalocyanines, showing instead a singlesharp Q band. The same applies to H2Pc inpyridine. The nonsplit Q band is a result of the basicity of thesolvents. It has been documented that instrongly basic solvents, the inner pyrrole hydrogens are acidic enough todissociate resulting in a charged system (Pc−2) which becomessymmetric and thus possesses an unsplit Q band [30].


Synthesis and photophysical properties of tetra- and octasubstituted phosphorous oxide triazatetrabenzcorrole photosensitizers.

Antunes EM, Nyokong T - Met Based Drugs (2008)

Spectrum of metal-free Pc (10) and transformation upon formationof PTClTBC (11) in DMSO. Concentration = 3.59 × 10−5 mol dm−3.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2266970&req=5

fig1: Spectrum of metal-free Pc (10) and transformation upon formationof PTClTBC (11) in DMSO. Concentration = 3.59 × 10−5 mol dm−3.
Mentions: TBC complexes havedistinct UV-Vis spectra with a sharp peak at ~450 nm [16–19], which can beemployed in their characterization. Theformation of the TBC complexes occurs when the MPc molecules no longer retainsa Pc moiety as they no longer have the fourth azomethine nitrogen (see Schemes 1 and 2).It is believed [11] that in the presence of excess metal halide, the bridgenitrogen of the Pc is eliminated, forming TBC. In this study, the unmetallated Pc derivatives(8, 10 and 12) were formed first,which, upon reaction with PBr3, resulted in the formation of PTBCderivatives. This was judged spectroscopically by the collapse of the sharp Qband in the visible region of unmetallated Pcs to three bands (in the Q bandregion), together with the formation of the sharp Soret band at 440 nm (see Figure 1). The spectra of unmetallated Pcs 6, 8, 10, and 12 in DMSO and pyridineshowed a single Q band (see Figure 1) which is uncharacteristic of unmetallatedPcs. Typically, unmetallated Pcs show a split Q band due to lack ofsymmetry. Solvation in polar aproticsolvents (such as DMSO and pyridine) occurs through their unsharedelectrons. Thus, in DMSO (see Figure 1)and pyridine, the spectra of 8, 10, and 12 did not show the normal splitting of the Qband that is typical of free-base phthalocyanines, showing instead a singlesharp Q band. The same applies to H2Pc inpyridine. The nonsplit Q band is a result of the basicity of thesolvents. It has been documented that instrongly basic solvents, the inner pyrrole hydrogens are acidic enough todissociate resulting in a charged system (Pc−2) which becomessymmetric and thus possesses an unsplit Q band [30].

Bottom Line: The Q band absorption spectra of the complexes are red-shifted compared to unsubstituted PTBC.The latter complex shows a large triplet lifetime (1.7 milliseconds), higher than for MPc derivatives.The chlorinated derivatives show good triplet yields (Phi(T) approximately 0.46 and 0.36) and relatively long lifetimes (256 and 452 microseconds), respectively, for 11 and 13.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Rhodes University, Grahamstown 6140, South Africa.

ABSTRACT
The synthesis of phosphorous oxide triazatetrabenzcorroles (TBC) tetra- (9, 11) or octa- (13) substituted on the ring with halogenated functional groups is reported. The complexes are not aggregated in dimethylsulfoxide (DMSO) and show solubility in solvents such as pyridine. The Q band absorption spectra of the complexes are red-shifted compared to unsubstituted PTBC. The latter complex shows a large triplet lifetime (1.7 milliseconds), higher than for MPc derivatives. The chlorinated derivatives show good triplet yields (Phi(T) approximately 0.46 and 0.36) and relatively long lifetimes (256 and 452 microseconds), respectively, for 11 and 13.

No MeSH data available.


Related in: MedlinePlus