Application of UV-Vis and NMR Spectra of Porphyrin Dications to the Investigation of the Structural Flexibility of Porphyrins Under Solution Conditions

Document Type : Research Article


Faculty of Chemistry, Institue for Advanced Studies, Basic in Sciences, Zanjan, I.R. IRAN


In this study, the influence of core protonation on UV-vis, 13C NMR, and 1H NMR spectra of meso-tetra(aryl)porphyrins has been investigated. The porphyrins have meso substituents with different electron-donating abilities and a steric hindrance at the porphyrin periphery. The changes in the position of the Soret band in UV-vis spectra and chemical shift of the β carbon and protons in 13C NMR and 1H NMR spectra provide evidence on the degree of out-of-plane deformation of porphyrin core. Also, the position of the higher wavelength absorption bands (Q bands) in UV-vis spectra of the porphyrin dications depends directly on the degree of coplanarity between the meso substituents and porphyrin mean plane. Introduction of bulky methyl groups and chlorine atoms onto the ortho-position of phenyl substituents leads to a significant decrease in the saddling of porphyrin core and degree of coplanarity of meso aryl groups with the porphyrin mean plane. Concomitant use of the UV-vis and NMR spectra provide valuable information on the relative molecular flexibility of different porphyrins towards planar to saddle conformational changes upon deprotonation of the used porphyrins. Furthermore, the spectral changes can be used to compare the dihedral angles between the meso aryl groups and the macrocycle mean plane of different porphyrins.


Main Subjects

[1] De Montellano P.R.O., "Cytochrome P450: Structure, Mechanism, and Biochemistry", Springer Science & Business Media (2005).
[2] Mosinger J., Slavetınska L., Lang K., Coufal P., Kubat P., Cyclodextrin Carriers of Positively Charged Porphyrin Sensitizers, Org. Biomol. Chem., 7(18): 3797 (2009).
[3] Zakavi S., Hoseini S., Mojarrad, A.G., New Insights Into The Influence of Weak and Strong Acids on the Oxidative Stability and Photocatalytic Activity of Porphyrins, New J. Chem., 41(19):11053-11059 (2017).
[5] Somma M.S., Medforth C.J., Nelson N.Y., Olmstead M.M., Khoury R.G., Smith K.M., Evidence for Unusually Strong Intramolecular Hydrogen Bonding in Highly Nonplanar Porphyrins, Chem. Commun., 1999 (13):1221-1222 (1999).
[6] Medforth C.J., Muzzi C.M., Shea K.M., Smith K.M., Abraham R.J., Jia S., Shelnutt J.A., NMR Studies of Nonplanar Porphyrins. Part 1. Axial Ligand Orientations in Highly Nonplanar Porphyrins, J. Chem. Soc., Perkin Trans. 2, 1997(4): 839-834 (1997).
[7] Haddad R.E., Gazeau S., Pécaut J., Marchon J.C., Medforth C.J., Shelnutt J.A., Origin of the Red Shifts in the Optical Absorption Bands of Nonplanar Tetraalkylporphyrins, J. Am. Chem. Soc.,125(5): 1253-1268 (2003).
[9] Aronoff S., Perchloric Acid Titrations of Porphyrins in Nitrobenzene, J. Phys. Chem.,62: 428-431 (1958).
[10] Stone A., Fleischer E.B., The Molecular and Crystal Structure of Porphyrin Diacids, J. Am. Chem. Soc.,90(11): 2735-2748 (1968).
[12] Walter R.I., Ojadi E.C.A., Linschitzll H., A Proton NMR Study of the Reactions with Acid of Meso-Tetraphenylporphyrins with Various Numbers of 4-(dimethylamino) Groups,J. Phys. Chem. 97(50): 13308-13312 (1993).
[13] Cheng B., Munro O.Q., Marques H.M., Scheidt W.R., An Analysis of Porphyrin Molecular FlexibilitysUse of Porphyrin Diacids, J. Am. Chem. Soc. 119(44): 10732-10742 (1997).
[14] Gouterman M., Spectra of porphyrins, J. Mol. Spectrosc. 6 138-163 (1961).
[16] Zakavi S., Omidyan R., Talebzadeh S., The Influence of Protonation on the Structure and Spectral Properties of Porphine: UV-Vis, 1H NMR and Ab Initio Studie, RSC Adv., 6(85): 82219-82226 (2016).
[17] Meot-Ner M., Adler A.D., Substituent Effects in Noncoplanar π Systems. ms-Porphins, J. Am. Chem. Soc. 97(18): 5107-5111 (1975).
[18] Alden R.G., Crawford B.A., Doolen R., Ondrias M.R., Shelnutt J.A., Ruffling of Nickel(II) Octaethylporphyrin in Solution, J. Am. Chem. Soc., 111 (6): 2070-2072 (1989).
[21] Rosa A., Ricciardi G., Baerends E.J., Romeo A., ‎ Synergism of Porphyrin-Core Saddling and Twisting of meso-Aryl Substituents,J. Phys. Chem. A, 110 (15):5180-5190 (2006).
[22] Gorski A., Starukhin A., Stavrov S., Gawinkowski S., Waluk J., Resonance Raman Spectroscopy Study of Protonated Porphyrin, Spectrochim. Acta A Mol. Biomol. Spectrosc., 173 (15): 350-355 (2017).
[24] Zakavi S., Najafi-Ragheb M., Interaction of Meso-Tetraarylporphyrins with Formic Acid: A Variable Temperature 1H NMR Study, Inorg. Chem. Commun., 36 (1): 113-116 (2013).
[26] Heydari-turkmani A., Zakavi S., Nikfarjam N., Novel Metal Free Porphyrinic Photosensitizers Supported on Solvent-Induced Amberlyst-15 Nanoparticles with a Porous Structure, New J. Chem.,41(12): 5012-5020 (2017).
[27] Mamardashvili N. Z., Golubchikov O. A., Spectral Properties of Porphyrins and their Precursors and Derivatives, Russ. Chem. Rev.,70 (7): 577-606 (2001).
[28] Adler A.D., Longo F.R., Finarelli J.D., Goldmacher J., Assour J., Korsakoff L., A Simplified Synthesis for Meso-Tetraphenylporphin, J. Org. Chem., 32(2): 476-476 (1967).
[29] Mohajer D., Zakavi S., Rayati S., Zahedi M., Safari N., Khavasi H.R., Shahbazian S.,Unique 1:2 Adduct Formation of Meso-Tetraarylporphyrins And Mesotetraalkylporphyrins with BF3: Aspectroscopic And Ab Initio Study, New J. Chem. 28(12): 1600-1607(2004).