The excitation wavelength dependent fluorescence of porphyrins

Uttamlal, Mahesh; Holmes-Smith, A. Sheila

doi:10.1016/j.cplett.2008.02.012

Cited by 121 publications

(64 citation statements)

References 22 publications

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“…As shown in Figure 1, the electronic absorption spectrum of a typical free‐base meso‐tetraphenylporphyrin consists of a strong transition to the second excited state (S0→S2) at about 400 nm (the Soret band or B(0,0)) and four relatively weak transitions to the first excited state (S0→S1) at about 500–650 nm (the Q‐bands: Q y (0,1), Q y (0,0), Q x (0,1), and Q x (0,0)). The fluorescence emission spectrum features two strong emission bands at about 650 (Q(0,0)) and 720 nm (Q(0,1)) 2. Over the past decade, porphyrin and its analogues, such as corrole, bacteriochlorin, and phthalocyanine (Figure 2), have earned recognition as key materials for application in catalytic systems,3,4 photodynamic therapy (PDT),5 field‐effect transistors,6 chemical sensors,7 electrochromic devices,8 energy conversion devices, [9–11] optoelectronic materials,12 and biomedical sensing and imaging,13–15 since their large π‐conjugated systems offer unique functionality.…”

Section: Introductionmentioning

confidence: 99%

Design and Properties of Porphyrin‐based Singlet Oxygen Generator

Jeong

Choi

2015

Israel Journal of Chemistry

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In this review, we address recent studies of porphyrin‐based molecular systems for efficient singlet oxygen (1O2) generation. Porphyrins have a highly conjugated, delocalized 18‐π electron system (for the shortest cyclic path) that is responsible for the strong absorption and emission characteristics in the visible region. Singlet oxygen is useful for applications in photodynamic cancer therapy (PDT), photooxidation of toxic molecules, and photoproduction of important intermediates for various chemicals owing to its high oxidation ability. Porphyrin and its analogues have been investigated as photosensitizers for 1O2 generation. The production of 1O2 is successfully regulated by photophysical parameters, such as intersystem crossing, triplet state (T1) lifetime, and photosensitizer to 3O2 energy transfer in molecular systems. Introduction of substituents with heavy atoms (halogen, metal) and radicals onto the photosensitizer (PS) exerts a strongly positive impact on intersystem crossing of the singlet excited state of the PS, promoting generation of the triplet excited state. Environmental conditions, such as solvent and pH, may also influence 1O2 generation. As a means to limit cellular photodamage, two‐photon absorption and DNA switches for 1O2 generation have been proposed and developed. Achieving control of singlet oxygen generation is pertinent to many arenas at the cutting edge of modern science, ranging from the chemical industry to biomedical applications.

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Section: Introductionmentioning

confidence: 99%

Design and Properties of Porphyrin‐based Singlet Oxygen Generator

Jeong

Choi

2015

Israel Journal of Chemistry

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“…In general, fluorescence of porphyrins is emitted from Q bands and shows similar spectrum shape unrelated to the excitation wavelength. Recently, a few reports have been published for the excitation wavelength dependence of fluorescence for p-expanded porphyrins with substituents at 5,15-meso-positions [2,3]. …”

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confidence: 99%

Absorption and Emission Properties of Acenaphthoporphyrins

Nakamura

Ono

Yamada

et al. 2009

Molecular Crystals and Liquid Crystals

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Acenaphtho[1,2-b]porphyrins (AcePs) were prepared by the [3 þ 1] condensation method and their photochemical properties were investigated. The fluorescence spectra of the free-base AcePs in CHCl 3 showed two emission bands at 660 and 720 nm, whose intensity drastically changed depending on the excitation wavelength. However, those of zinc complexes did not show such a wavelength dependence and showed similar emission spectra by the excitation at various wavelengths. The fluorescence excitation spectra and quantum yields of the free-base AcePs in CHCl 3 showed the similar excitation wavelength dependence. This fact indicates that two electronic structures exist in the free-base AcePs and their fluorescence is emitted from one structure in higher quantum yield (k EM ¼ 660 nm) and from the other in lower yield (k EM ¼ 720 nm), respectively.The p-conjugated porphyrins with exocyclic aromatics have been extensively studied because of their special optical and electrical properties [1]. It is well known that porphyrin molecules present two absorption bands in the visible spectra, Soret (S 0 -S 2 transition) and Q (S 0 -S 1 transition) bands, which are observed at around 400 nm and at 500-650 nm, respectively. In general, fluorescence of porphyrins is emitted from Q bands and shows similar spectrum shape unrelated to the excitation wavelength. Recently, a few reports have been published for the excitation wavelength dependence of fluorescence for p-expanded porphyrins with substituents at 5,15-meso-positions [2,3].

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“…Fig. 2B showed the emission spectrum of complex 1, which is typical of a metallated porphyrin with two bands differing in intensity at 598 and 650 nm [19].…”

Section: Uv-vis Spectramentioning

confidence: 99%