Optical Spectra and Electronic Structure of Porphyrins and Related Rings

Gouterman, Martin

doi:10.1016/b978-0-12-220103-5.50008-8

Cited by 908 publications

(860 citation statements)

References 272 publications

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“…Nickel(II) porphyrins are non-fluorescent due to radiationless decay pathways associated with the unfilled d orbitals. 24 As shown in Fig. 5, the fluorescence profiles for MgDPP 2 and a mixture of 2 with NiDPP 13 differ only slightly.…”

Section: Electronic Absorption Spectra Emission Spectra and Redox Prmentioning

confidence: 77%

Multiporphyrin coordination arrays based on complexation of magnesium(ii) porphyrins with porphyrinylphosphine oxides

2007

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Di-and triporphyrin arrays consisting of 5,15-diphenylporphyrinatomagnesium(II) (MgDPP) coordinated to free-base and Ni(II) porphyrinyl mono-and bis-phosphine oxides, as well as the self-coordinating diphenyl [10,20- demonstrate the strong affinity of phosphine oxides towards Mg(II) porphyrins. These complexes are the first strongly bound synthetic Mg(II) multiporphyrin complexes and could potentially mimic the "special pair" in the photosynthetic reaction centre.

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Section: Electronic Absorption Spectra Emission Spectra and Redox Prmentioning

confidence: 77%

Multiporphyrin coordination arrays based on complexation of magnesium(ii) porphyrins with porphyrinylphosphine oxides

2007

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“…This phenomenon is well demonstrated by the Soret-bands of H2TMPyP 4+ and Co(III)TMPyP 5+ at 421 and 434 nm, respectively [17]. Such metalloporphyrins, the spectra of which cannot be interpreted by the 4 MO theory of Gouterman, are classified as hyper-porphyrins [18]. This unusual phenomenon can be explained by the very strong interaction between the  orbital of the porphyrin ring and the d orbital of the metal center [3].…”

mentioning

confidence: 81%

“…The bands assigned to the (0,2) transition are not perceptible in this case. Generally, the highly distorted porphyrin complexes with diamagnetic metal center do not display appreciable fluorescence at room temperature [18]. Accordingly, earlier, Mn(III) and Co(III) porphyrins were not found to be fluorescent at all [17].…”

mentioning

confidence: 98%

Photophysical and photocatalytic behavior of cobalt(III) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin

Fodor¹,

Horváth²,

Fodor³

et al. 2014

Inorganic Chemistry Communications

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Although kinetically inert cationic Co(III)TMPyP 5+ (H2TMPyP 4+ = 5,10,15,20-tetrakis(methylpyridinium-4-yl)porphyrin) was considered earlier to be very weakly emissive, both the spectrum and the lifetime of its fluorescence could be determined. Besides, this complex proved to be favorable for outer-sphere photoinduced reduction of the metal center in the presence of triethanolamine (TEOA) as electron donor quenching the triplet excited state of this metalloporphyrin. The corresponding cobalt(II) porphyrin formed in this way was also photoactive; it forwarded an electron to a suitable acceptor (e.g., methylviologen) upon irradiation, regenerating the starting complex. Hence, this system may be a candidate for hydrogen generation from water by utilization of visible light. Metalloporphyrins play important roles in nature, due to their special spectral, coordination and redox features. Their advantageous photoinduced properties can also be exploited in various photocatalytic procedures [1]. Water-soluble derivatives can be utilized in environmentally benign systems not containing organic solvents. Kinetically inert in-plain metalloporphyrins, in which the metal center coplanarly fits into the cavity of the ligand, may offer promising possibilities for realization of photocatalytic systems based on outer-sphere electron transfer [2]. The so-called hyper-porphyrins can be especially interesting in this respect, due to their distorted structure, which may increase the (photo)redox reactivity of these complexes. From water-soluble metalloporphyrins of this type, photoredox reactions of manganese(III) complexes were thoroughly studied [1,3,4], while scarce attention was paid to the corresponding cobalt(III) porphyrins in this respect. Keywords: cobalt(III) porphyrinPhotocatalytic oxidation of the sulfide content of a wastewater to sulfate was studied with Co(III)TMPyP 5+ , Mn(III)TMPyP 5+ , and Fe(III)TMPyP 5+ (H2TMPyP 4+ = 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin) [5]. Upon irradiation in the range of the Soretbands, the cobalt(III) complex proved to be the most efficient, but the results have not been interpreted. This metalloporphyrin can also connect to the chain of DNA and oxidatively split it in the presence of suitable electron acceptors [6]. Since cationic manganese(III) porphyrins proved to be efficient photocatalysts in the presence of appropriate electron donors (such as EDTA and TEOA) and methylviologen as electron acceptor [1,3,7], cationic cobalt(III) porphyrins, the other characteristic representatives of water-soluble hyper-porphyrins, are also worth investigating in this respect. Hence, in this work, some photophysical and photochemical properties of Co(III)TMPyP 5+ were studied, also confirming its photocatalytic behavior, which may be utilized in water-splitting by solar radiation.The compounds used for our experiments were of reagent grade. Water purified in a Millipore/Milli-Q system was applied as solvent. Stock solutions of Co(III)TMPyP 5+ were prepared by in situ generation ...

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“…The first is that the excitation regions between 390 nm and 415 nm are the best for autofluorescence from porphyrins because porphyrins emit bright red-orange when they are excited in Soret's band around 405 nm. 5 Actually, we established by using microspectrophotometry that the red-orange autofluorescence in 30-week-old male LEC rat kidneys was from the emission of porphyrins. 6,7 The second hypothesis is that there are many articles about red-orange autofluorescence in hepatocytes with liver disease, such as hepatitis, liver cirrhosis, porphyria cutanea tarda, and especially hepatocellular carcinoma.…”

Section: What Is the True Origin Of The Bright Red-orange Autofluoresmentioning

confidence: 99%

What Is the True Origin of the Bright Red-Orange Autofluorescence in the Hepatocytes?

Nakayama

Tamura

2010

Hepatology

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insulin sensitivity was related to SVR. Lastly, >80% of females receiving metformin reached virus clearance at week 24, and this did not correlate with weight loss or with insulin sensitivity at this time point. A relationship between metformin use and viral decline was seen in females. Metformin does not have an antiviral effect and, thus, it seems to be due to an improvement in the antiviral activity of the combined peginterferon and ribavirin therapy. Females that reached HOMA <2 but had no weight loss showed significantly higher viral decline (À5.3 [SD ¼ 0.79] versus À4.2 [SD ¼ 1.8] log 10 HCV RNA; P ¼ 0.004).In hepatitis C, insulin resistance depends on viral factors such as genotype and HCV replication as well as host factors such as body weight and/or steatosis. However, the weighting of these factors differs between patients. 3 Improving viral and/or host factors can help improve insulin sensitivity. The final mechanism by which metformin improved SVR in females remains unclear, and further studies are warranted to elucidate how insulin-sensitizer drugs could improve response in patients with chronic hepatitis C treated with pegylated interferon plus ribavirin. What Is the True Origin of the Bright Red-Orange Autofluorescence in the Hepatocytes?To the Editor:We read with interest the article titled ''Copper-Metallothionein Autofluorescence'' by Quaglia et al. 1 The authors mentioned: (1) fluorescence microscopy is based on the interactions between light wavelengths, molecules, and filters/dichromatic mirrors, which may unmask specific combinations for the identification of particular structures; (2) autofluorescence-based techniques have been used for the assessment of fibrosis, cell metabolism, and differentiation; discrimination between neoplastic and non-neoplastic tissue; and studies of microorganisms and drug interaction. We agree with the authors' descriptions concerning fluorescence microscopic techniques. However, we should usually recognize that these factors are restrictive and exceptional. Here, we would like to demonstrate that there was another possibility in their observations. Their fluorescence microscopy systems were as follows: dichromatic mirror reflecting at 415 nm wavelength, excitation filter at 420 6 30 nm wavelength, and suppression filter at 465 6 20 nm wavelength. The unstained 6-lm-thick sections were excited at the regions between 390 nm and 415 nm. These regions did not match for autofluorescence from copper-metallothioneins (minutely cuprous [Cu(I) or Cu þ ] metallothioneins [MTs]), because a maximum peak of excitation wavelength for Cu(I)-MTs is around 300 nm. 2 Therefore, it can be imagined that the emission from Cu(I)-MTs was very weak. Mysteriously, the red-orange autofluorescence, which originated from Cu(I)-MTs at around 600 nm, 2 was observed when illuminated with the excitation filter, although the suppression filter at 465 6 20 nm shades the light of wavelength more than 485 nm. Moreover, Cu(I)-MTs were identified with the comparable colocalizations of the red-oran...

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Optical Spectra and Electronic Structure of Porphyrins and Related Rings

Cited by 908 publications

References 272 publications

Multiporphyrin coordination arrays based on complexation of magnesium(ii) porphyrins with porphyrinylphosphine oxides

Multiporphyrin coordination arrays based on complexation of magnesium(ii) porphyrins with porphyrinylphosphine oxides

Photophysical and photocatalytic behavior of cobalt(III) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin

What Is the True Origin of the Bright Red-Orange Autofluorescence in the Hepatocytes?

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