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Dechan P, Devi Bajju G, Sood P. Trans A
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Porphyrins: Synthesis, Crystal Structure Determinations and Hirshfeld Surface Analysis. ChemistrySelect 2020. [DOI: 10.1002/slct.202001052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Padma Dechan
- Postgraduate Department of ChemistryUniversity of Jammu Jammu 180006 India
| | - Gauri Devi Bajju
- Postgraduate Department of ChemistryUniversity of Jammu Jammu 180006 India
| | - Puneet Sood
- Puneet SoodAdvanced Materials Research Centre, Block- A2, Kamand Campus, Indian Institute of Technology, Mandi Himachal Pradesh 175005 India
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Dechan P, Bajju GD. A hypervalent Bismuth(III) derivative of Tetrakis-4-methoxyphenyl porphyrin: Synthesis, spectroscopic characterisation and morphological investigations. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.127320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Synthesis and spectroscopic properties of axial phenoxide and para amino phenoxide incorporated indium (III) porphyrins. J Mol Struct 2019. [DOI: 10.1016/j.molstruc.2019.05.120] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Formation, Photophysics, and Photochemistry of Anionic Lanthanide(III) Mono- and Bisporphyrins. Molecules 2019; 24:molecules24071309. [PMID: 30987150 PMCID: PMC6480351 DOI: 10.3390/molecules24071309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 03/29/2019] [Accepted: 03/31/2019] [Indexed: 11/17/2022] Open
Abstract
Since water-soluble porphyrin complexes of lanthanides(III) have proved to be promising for medical applications (e.g., luminescence imaging, photodynamic therapy, and theranostics), the investigation of the formation, photophysical, and photochemical properties of such coordination compounds provides useful pieces of information for their potential usage. Steady-state and time-resolved fluorometry, UV-Vis absorption spectroscopy, and continuous-wave photolysis were utilized for this purpose. 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin formed mono- and bisporphyrin complexes with samarium(III), europium(III), and gadolinium(III) as representatives in the middle of the lanthanide series. The special photoinduced behavior of these compounds was mostly determined by the position of the metal center, which was located out of the ligand plane, thus distorting it. Besides, the photochemical and, especially, photophysical features of the corresponding mono- and bisporphyrin complexes were similar because, in the latter species, two monoporphyrins were connected by a weak metal bridge between the peripheral sulfonato substituents (tail-to-tail dimerization). The formation of these coordination compounds and the transformation reactions between the mono- and bisporphyrins were rather slow in the dark at room temperature. These processes were accelerated by visible irradiation. However, dissociation and, especially, redox degradation were the main photoreactions in these systems, although with low quantum yields. Additionally, depending on the excitation wavelength, new types of photoproducts were also detected.
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Leng F, Liu H, Ding M, Lin QP, Jiang HL. Boosting Photocatalytic Hydrogen Production of Porphyrinic MOFs: The Metal Location in Metalloporphyrin Matters. ACS Catal 2018. [DOI: 10.1021/acscatal.8b00764] [Citation(s) in RCA: 135] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fucheng Leng
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Hang Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Meili Ding
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
| | - Qi-Pu Lin
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China
| | - Hai-Long Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
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Valicsek Z, Kiss MP, Fodor MA, Imran M, Horváth O. Formation, Photophysics, Photochemistry and Quantum Chemistry of the Out-of-Plane Metalloporphyrins. HUNGARIAN JOURNAL OF INDUSTRY AND CHEMISTRY 2017. [DOI: 10.1515/hjic-2017-0006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Among the complexes of porphyrins, special attention has been paid to those possessing out-of-plane (OOP) structures, for the formation of which the size, as well as the coordinative character of the metal center are responsible. In these coordination compounds, the central atom cannot fit coplanarly into the cavity of the ligand, hence, it is located above the porphyrin plane, distorting it. Equilibria and kinetics of the complex formation, spectrophotometric, photophysical and primary photochemical properties of post-transition and lanthanide OOP metalloporphyrins were investigated, in addition electronic structural calculations were performed; hence, the general OOP characteristics were determined.Meanwhile, few doubtful questions have attempted to be answered concerning the categorization of metalloporphyrins, the borderline case complexes and hyperporphyrins.
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Ghadermazi M. Characterization, luminescent properties, crystal structure determination, and thermal properties of [Tl(Ph2phen)Cl3(DMSO)]. J STRUCT CHEM+ 2016. [DOI: 10.1134/s0022476616050176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Valicsek Z, Horváth O. Application of the electronic spectra of porphyrins for analytical purposes: The effects of metal ions and structural distortions. Microchem J 2013. [DOI: 10.1016/j.microc.2012.07.002] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Valicsek Z, Eller G, Horváth O. Equilibrium, photophysical and photochemical examination of anionic lanthanum(III) mono- and bisporphyrins: the effects of the out-of-plane structure. Dalton Trans 2013; 41:13120-31. [PMID: 23001150 DOI: 10.1039/c2dt31189e] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lanthanum(III) ions form kinetically labile complexes with the 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (H(2)TSPP(4-)), the compositions and formation constants of which significantly depend on the presence of potential axial ligands (at 0.01 M). Deviating from the chloride ion, acetate coordinating to the metal center hinders the formation of a bisporphyrin complex. In these lanthanum(III) complexes, the metal center, due to its large ionic radius (103.2 pm), is located out of the ligand plane, distorting it. Accordingly, the absorption and fluorescence spectra of these coordination compounds display special properties characteristic of the so-called sitting-atop (SAT) or out-of-plane (OOP) porphyrin complexes. Metalation significantly decreases the quantum yield of the fluorescence from the S(1) excited state. Quantum chemical calculations (DFT) confirm the considerable OOP displacement of the La(III) center (about 120 pm in the monoporphyrin complexes). The monoporphyrins display efficient fluorescence (Φ ≈ 0.03), while the bisporphyrin does not emit. Differing from the normal (in-plane) metalloporphyrins, the excitation of these lanthanum(III) porphyrins leads to an irreversible ligand-to-metal charge transfer (LMCT) followed by the opening of the porphyrin ring, which is also typical of OOP complexes. Dissociation releasing free-base porphyrin can also be observed upon irradiation of the monoporphyrin in acetate solution, while in the presence of chloride ions interconversions of the mono- and bisporphyrins may also take place beside the irreversible photoredox reaction.
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Affiliation(s)
- Zsolt Valicsek
- Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Veszprém, Hungary
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Horváth O, Valicsek Z, Harrach G, Lendvay G, Fodor MA. Spectroscopic and photochemical properties of water-soluble metalloporphyrins of distorted structure. Coord Chem Rev 2012. [DOI: 10.1016/j.ccr.2012.02.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Valicsek Z, Lendvay G, Horváth O. Equilibrium, photophysical, photochemical and quantum chemical examination of anionic mercury(I) porphyrins. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424609001261] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Hg22+ ion and 5,10,15,20-tetrakis(parasulphonato-phenyl)porphyrin anion can form 2:1 (2 clusters:1 porphyrin) and 2:2 complexes, while the formation of the 1:1 species is not observable: it is only an intermediate, similarly to the cases of other large metal ions of small charge-density. The differences between mercury(I) and mercury(II) porphyrins in the composition of monoporphyrins (2:1 vs. 1:1), in the stability and the Soret absorption based on the arrangement of 2:2 complexes (asymmetric vs. probably symmetric sandwich-structure), in the kinetic behavior (molecularities and the special dimerization of HgIIP4-), in the product of the photoinduced dissociations of 2:2 bisporphyrins (free-base ligand vs. 1:1 complex) can prove that no mercury(II) porphyrins can form due to the possible disproportion of dimercury(I) ions. However, the similarities in the absorption, photophysical and photochemical features (also to other out-of-plane metalloporphyrins) suggest that the out-of-plane position of metal center and the distorted structure of complexes may be responsible for these common properties, the so-called sitting-atop characteristics. Moreover, the calculated structural data of the theoretically studied 1:1 mercury(I) porphyrin are very similar to those of Hg II P as a consequence of the charge separation in the cluster based on the strength of metal-nitrogen bonds. In the case of the 2:2 species, neither the increased distance (because of the Hg-Hg bond), nor the absence of 45° rotation of the two ligands can significantly modify the π-π interaction because its both measured and calculated absorption spectra are similar to those of Hg II2 P 2.
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Affiliation(s)
- Zsolt Valicsek
- Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém, Hungary
| | - György Lendvay
- Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém, Hungary
- Institute of Structural Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary
| | - Ottó Horváth
- Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém, Hungary
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Valicsek Z, Horváth O, Patonay K. Formation, photophysical and photochemical properties of water-soluble bismuth(III) porphyrins: The role of the charge and structure. J Photochem Photobiol A Chem 2011. [DOI: 10.1016/j.jphotochem.2011.10.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Harrach G, Valicsek Z, Horváth O. Water-soluble silver(II) and gold(III) porphyrins: The effect of structural distortion on the photophysical and photochemical behavior. INORG CHEM COMMUN 2011. [DOI: 10.1016/j.inoche.2011.08.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Formation, photophysics, and photochemistry of cadmium(II) complexes with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin and its octabromo derivative: The effects of bromination and the axial hydroxo ligand. J Photochem Photobiol A Chem 2011. [DOI: 10.1016/j.jphotochem.2010.12.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Škorić I, Kikaš I, Kovács M, Šindler-Kulyk M, Horváth O. Synthesis, spectroscopic characterization and photophysics of new functionalized 2,3-distyrylfurans: Substituent and solvent effects on their photobehavior. J Photochem Photobiol A Chem 2010. [DOI: 10.1016/j.jphotochem.2010.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Wang MS, Xu G, Zhang ZJ, Guo GC. Inorganic–organic hybrid photochromic materials. Chem Commun (Camb) 2010; 46:361-76. [PMID: 20066296 DOI: 10.1039/b917890b] [Citation(s) in RCA: 271] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Ming-Sheng Wang
- State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China
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Wang KK, Choi KH, Shin HW, Kim BJ, Im JE, Oh SL, Park NS, Jung M, Oh JB, Lee MJ, Kim HK, Kim YR. Photophysics of a new photosensitizer with high quantum yield of singlet oxygen generation and its application to stereo-selective synthesis of (+)-deoxoartemisinin. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.09.081] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Dehghani H, Shaterian M. Synthesis of new ionic intermediate sitting-atop complexes of free base meso-tetraarylporphyrin and phosphorus(V) chloride under solvent free conditions. Inorganica Chim Acta 2009. [DOI: 10.1016/j.ica.2009.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Orzeł Ł, van Eldik R, Fiedor L, Stochel G. Mechanistic Information on Cu
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Metalation and Transmetalation of Chlorophylls. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200800662] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Łukasz Orzeł
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30‐060 Kraków, Poland, Fax: +48‐12‐6340515,
- Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen‐Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany, Fax: +49‐9131‐8527387,
| | - Rudi van Eldik
- Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen‐Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany, Fax: +49‐9131‐8527387,
| | - Leszek Fiedor
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30‐387 Kraków, Poland, Fax: +48‐12‐6646902
| | - Grażyna Stochel
- Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30‐060 Kraków, Poland, Fax: +48‐12‐6340515,
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Spectrophotometric Studies of the Thermodynamics of Molecular Complexation between Free Base Meso-Tetraarylporphyrins and Iodine(III) Chloride. J SOLUTION CHEM 2009. [DOI: 10.1007/s10953-009-9409-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Synthesis, characterization and the thermodynamic study of intermediate sitting-atop (i-SAT) complexes of free base meso-tetraarylporphyrins with InCl3. Inorganica Chim Acta 2009. [DOI: 10.1016/j.ica.2008.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Valicsek Z, Lendvay G, Horváth O. Equilibrium, photophysical, photochemical, and quantum chemical examination of anionic mercury(II) mono- and bisporphyrins. J Phys Chem B 2008; 112:14509-24. [PMID: 18954102 DOI: 10.1021/jp804039s] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mercury(II) ion and 5,10,15,20-tetrakis(parasulfonato-phenyl)porphyrin anion can form 1:1, 2:2, and 3:2 (metal ion/porphyrin) out-of-plane (OOP) complexes, from which Hg2P2(8-) has not been identified until now. Identification of this species significantly promoted the confirmation of the composition and the precise elucidation of the equilibrium of Hg3P2(6-). Since the formation of each complex is too fast, their kinetic behavior was studied from the side of dissociation. The rate-determining step in dissociations, as well as in the formation of the 2:2 complex, that is, the dimerization of 1:1 complex, proved to be virtually first-order under these conditions, while the consecutive formations of HgP(4-) and Hg3P2(6-) are second-order reactions. The equilibria can be spectrophotometrically investigated because the Soret- as well as the Q-absorption bands of the free-base ligand are more and more red-shifted in the series of 1:1, 2:2, and 3:2 complexes, and the split of Q-bands disappears as the singlet-1 excited states become degenerate; in the case of bisporphyrins, the bands broaden, especially in the longer-wavelength region of the spectra. The quantum yield and the lifetime of S1-fluorescence from the macrocycle is decreased by the insertion of a mercury(II) ion due to distortion, and in bisporphyrins the luminescence totally ceases because their more complicated structure promotes other ways of energy dissipation. The lifetime of the triplet excited-state is also reduced by metalation. The transient absorption measured upon excitation of Hg3P2(6-) probably originates from Hg2P2(8-) formed by efficient photodissocation during the laser pulse. This photoinduced dissociation is characteristic to out-of-plane complexes, but in metallo-monoporphyrins it needs the energetically higher Soret-excitation; in bisporphyrins, it can take place during irradiation at the longer Q-wavelengths. Investigation of the intramolecular photoredox reactions has proved that for the increased efficiency of the indirect photoinduced LMCT, not the redox potential, but the position of the metal center is responsible. The two orders of magnitude higher photoredux quantum yield for the 3:2 complex, compared to that of the 2:2 species, can be explained by the repulsive effect of the inner mercury(II) ion pushing the other two farther out of the ligand cavity. In bisporphyrins the second excited states are photochemically more reactive than the first ones, while most of the photochemical processes of HgP(4-) originate from the first excited state. According to our quantum chemical calculations, the mercury(II) ion causes the expansion of the porphyrin-cavity; therefore its out-of-plane position is smaller than the value expected based on its ionic radius. In the hitherto unknown 2:2 dimer two 1:1 saucer-shaped monomers are kept together by secondary forces, mostly by pi-pi interaction, but their relative arrangement was not unequivocally determined by the two DFT functionals used. The arrangements with a symmetry axis or plane perpendicular to both rings are not favored; instead, the two monomers are shifted along the porphyrin planes, either in a Hg-P-Hg-P or a Hg-P-P-Hg order. Our time-dependent density functional theory (TD-DFT) calculations indicate that the electronic spectra are not very sensitive to the structure of the dimer, even though the environment of the porphyrin rings is quite different if one of the metal ions is between or outside of both macrocycles. The calculated spectral shifts agree only partially with the experimental data. The TD-DFT calculations suggest that the chromophores are not fully independent in the bisporphyrins and that the observed spectral shift cannot be uniquely assigned to the geometrical distortion of the porphyrin macrocyle.
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Affiliation(s)
- Zsolt Valicsek
- Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, H-8201 Veszprem, P.O. Box 158, Hungary.
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Synthesis of intermediate sitting-atop complexes (i-SAT) from the reaction between free base meso-tetraarylporphyrins and phosphorus(III) chloride in solvent free media. Polyhedron 2008. [DOI: 10.1016/j.poly.2008.07.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Dehghani H, Bordbar M, Rezakhani S, Mansournia MR. Spectrophotometric Studies of the Thermodynamics of Molecular Interaction between Some Free Basemeso-Tetraarylporphyrins and SbF3. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2008. [DOI: 10.1246/bcsj.81.711] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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DENG K, CHEN ZL, ZHOU XP, WANG WF, YANG XX, TIAN J. Studies on the Photodynamic Mechanism of Tetrapyrrole Compounds by Laser Flash Photolysis. CHINESE J CHEM 2008. [DOI: 10.1002/cjoc.200890024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Huszánk R, Lendvay G, Horváth O. Air-stable, heme-like water-soluble iron(II) porphyrin: in situ preparation and characterization. J Biol Inorg Chem 2007; 12:681-90. [PMID: 17333300 DOI: 10.1007/s00775-007-0217-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 01/29/2007] [Indexed: 10/23/2022]
Abstract
Preparation of the water-soluble, kinetically labile, high-spin iron(II) tetrakis(4-sulfonatophenyl)porphyrin, Fe(II)TPPS(4-), has been realized in neutral or weakly acidic solutions containing acetate buffer. The buffer played a double role in these systems: it was used for both adjusting pH and, via formation of an acetato complex, trapping trace amounts of iron(III) ions, which would convert the iron(II) porphyrins to the corresponding iron(III) species. Fe(II)TPPS(4-) proved to be stable in these solutions even after saturation with air or oxygen. In the absence of acetate ions, however, iron(II) ions play a catalytic role in the formation of iron(III) porphyrins. While the kinetically inert iron(III) porphyrin, Fe(III)TPPS(3-), is a regular one with no emission and photoredox properties, the corresponding iron(II) porphyrin displays photoinduced features which are typical of sitting-atop complexes (redshifted Soret absorption and blueshifted emission and Q absorption bands, photoinduced porphyrin ligand-to-metal charge transfer, LMCT, reaction). In the photolysis of Fe(II)TPPS(4-) the LMCT process is followed by detachment of the reduced metal center and an irreversible ring-opening of the porphyrin ligand, resulting in the degradation of the complex. Possible oxygen-binding ability of Fe(II)TPPS(4-) (as a heme model) has been studied as well. Density functional theory calculations revealed that in solutions with high acetate concentration there is very little chance for iron(II) porpyrin to bind and release O(2), deviating from heme in a hydrophobic microenvironment in hemoglobin. In the presence of an iron(III)-trapping additive that is much less strongly coordinated to the iron(II) center than the acetate ion, Fe(II)TPPS(4-) may function as a heme model.
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Affiliation(s)
- Róbert Huszánk
- Department of General and Inorganic Chemistry, University of Pannonia, P.O. Box 158, Veszprém 8201, Hungary
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