Luminescence of porphyrins and metalloporphyrins. Part 3.—Heavy-atom effects

Harriman, Anthony

doi:10.1039/f29817701281

Cited by 218 publications

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“…The electronic spectra and states of free base porphyrin are fairly well described in terms of a simple four-orbital model [4]. Transitions occur between the two highest filled molecular orbital alu('lr) and a2u('lr) and two lowest empty orbitals eg('lr*).…”

Section: Resultsmentioning

confidence: 91%

“…IdJ as metallated porphyrine molecules in various solvents lIId vapor phase [2][3][4][5] while investigations of these systems msolid matrices especially in inorganic glassy matrices have l!Ceived little attention. The present work has been underIlken because of the following reasons: (i) the metalloporIhyrine systems are particularly useful as photosensitizers and it is an inherent necessity for such systems to absorb ltrongly in the visible region and possess a relatively long excited state lifetime; (ii) the formation of triplet state can…”

Section: ~ Introductionmentioning

confidence: 99%

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Optical properties of porphyrins in borate glassy matrix

Kumar

Thomas

Jose

et al. 2002

Materials Chemistry and Physics

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Optical properties of free and substituted porphyrins (PP) doped borate glass matrix are reported for the first time. Absorption spectral !l5urernents of H2 TPP, CdTPP, MgTPP and ZnTPP doped borate glass matrix have been made in the 200-1100 nm region and the :l:traobtained are analyzed to obtain the optical bandgap (Eg) and other important spectral parameters viz. oscillator strength (f), molar :Iinction coefficient (e), electric dipole strength (l), absorption cross-section (a.) and molecular concentration (N). Intense fluorescence ~observed in the region 668-685 nm for CdTPP, ZnTPP and MgTPP doped matrices, whereas no such fluorescence was observed in ~TPP doped matrix. Fluorescence intensity was observed to be almost similar in all the metallated porphyrine matrices. Fluorescence mdwidth (~)..), decay time (r), stimulated emission cross-section (a) and optical gain (G) of the principal fluorescence transitions iUesponding to the Q-band excitation were also evaluated and discussed. © 2002 Elsevier Science B.V. All rights reserved. [·mail address: spapforum@vsnl.com (N.v. Unnikrishnan).systems in realizing intense fluorescence and optical amplification is enhanced by the above mentioned factors; (iv) the present systems studied possess such properties and may have significant applications in energy storage devices. The aim of the present work is, in general, to elucidate the optical absorption and emission spectral properties of H2 TPP, CdTPP, ZnTPP and MgTPP molecules in borate glassy matrix and to investigate the effect of the metal ions on these properties. A quantitative analysis of the spectral and radiative properties of the investigated samples have also been reported and discussed. ExperimentalAll the glass samples were prepared by the well-known rapid quenching technique [3]. Reagent grade boric acid (H3B03) and doubly sublimed PP have been used as the starting materials for the preparation of the glass samples. The weighed quantities of the starting materials for 18 gm of glass are mixed homogeneously using an agate mortar. The batch was then placed in a silica crucible and heated in an electric muffle furnace. A slow heating was initially maintained until the temperature reaches 80°C and decomposition of H3B03 to B203 is complete. The temperature was then rapidly increased to 120°C so as to obtain a greenish melt. The melt was retained for about 10 min and then 0254'()584/02/$ -see front matter

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Section: Resultsmentioning

confidence: 91%

Section: ~ Introductionmentioning

confidence: 99%

Optical properties of porphyrins in borate glassy matrix

Kumar

Thomas

Jose

et al. 2002

Materials Chemistry and Physics

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“…While the majority of applications utilize metallated porphyrins, free-base porphyrins exhibit distinct characteristics that include enhanced fluorescence quantum yields and excited state lifetimes relative to metallated porphyrins [24] and pH dependent spectral properties owing to the acid/base properties of the porphyrin central nitrogens. Porphyrin diacids may be obtained upon protonation of the imino nitrogen atoms and exhibit perturbed photophysical properties relative to the neutral derivatives [25−29].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic characterization of free-base hydroxy(arylethynyl)porphyrins in acidic and basic media

Evens

Splan

2017

J. Porphyrins Phthalocyanines

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ABSTRACT:The addition of arylethynyl groups to the porphyrin macrocycle represents an effective strategy with which to enhance the light-harvesting properties of porphyrins. We now extend this modification to arylethynyl porphyrins with two or four p-hydroxyphenyl substituents. Arylethynyl porphyrins bearing four, but not two, p-hydroxyphenyl substituents show evidence of aggregation under acidic conditions. Under basic conditions, deprotonation of the peripheral hydroxyphenyl substituents results in substantially red-shifted spectral features and enhanced absorption in the Q-band region. When the hydroxyphenyl groups are appended to the porphyrin macrocylce via the ethynyl spacers, the spectral shifts observed upon deprotonation are significantly enhanced relative to those observed for hydroxyphenylporphyrins, highlighting the role of expanded conjugation in altering porphyrin photophysics.

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“…There are, however, many factors that count against the use of manganese porphyrins as photosensitizers, one of them being the short excited state lifetimes (28), which play a decisive role in the efficiency as long as we have to let the reactants diffuse together. Another way ofcreating oxidized manganese compounds photochemically (see Fig.…”

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confidence: 99%

Environmental influences on the photooxidation of manganese by a zinc porphyrin sensitizer

Wohlgemuth

Otvos²,

Calvin³

1982

Proc. Natl. Acad. Sci. U.S.A.

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The photosensitized oxidation of a membranebound Mn(Ell) tetrapyridylporphyrin derivative by a Zn tetrapyridylporphyrin derivative, which is confined to the membrane, has been achieved in negatively charged membranes consisting of phosphatidylglycerol or phosphatidic acid. At the same time, the zwitterionic electron acceptor, propylviologen sulfonate (PVS0), is reduced in the aqueous phase. The same reaction cannot be obtained with zwitterionic or cationic membranes, nor does this photosensitized reaction take place in a homogeneous solution with Mn(III) tetrapyridylporphyrin and Zn tetrapyridylporphyrin. These results show that the organization of donor, sensitizer, and acceptor at an appropriately selected interface allows reactions that would not occur in homogeneous solutions.

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Luminescence of porphyrins and metalloporphyrins. Part 3.—Heavy-atom effects

Cited by 218 publications

References 0 publications

Optical properties of porphyrins in borate glassy matrix

Optical properties of porphyrins in borate glassy matrix

Spectroscopic characterization of free-base hydroxy(arylethynyl)porphyrins in acidic and basic media

Environmental influences on the photooxidation of manganese by a zinc porphyrin sensitizer

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