Novel cycloketo tetraphenylporphyrins: spectroscopic study of structure-properties relationships

The developments in porphyrin chemistry over the last decades give great advantages for the practical use of porphyrin-based compounds. The properties of these compounds can be systematically tuned by rational utilization of substituents on meso- and/or β-positions as well as by using different metal atoms in the center of the tetrapyrrole macrocycle. Recently we prepared novel mono- and bis-functionalized cycloketo-porphyrins (CKPors). In this work the results of detailed spectroscopic investigations of these compounds are presented. It was found that a seven-membered ketone exocycle remarkably influences the photophysical properties of the CKPor systems. For mono-functionalized CKPors it results in strongly enhanced probability of intersystem crossing S1 → T1 with an ISC quantum yield up to 90%. Moreover, the absorption of all CKPors undergoes a bathochromic shift and the Q-bands extinction is above two times higher compared to that of H2TPP, what makes these compounds promising candidates for use as photosensitizers in photodynamic therapy of tumors. For the first time two NH-tautomers of nonsymmetrical CKPors were experimentally resolved at room temperature using optical spectroscopic methods. It was found that the concentration of tautomer A with a lower frequency of the S0,0 → S1,0 transition is higher than that one of tautomer B at room temperature, and becomes dominant with cooling down. In contrast - and as it is expected - only one optical active species was observed for non-symmetrical CKPor with a central Zn(II) atom as well as for symmetrical bis-CKPor.

[1]  B. Röder,et al.  The influence of solvent polarity and metalation on energy and electron transfer in porphyrin-phthalocyanine heterotrimers. , 2007, The journal of physical chemistry. B.

[2]  C. Storm,et al.  Nitrogen-hydrogen tautomerism in porphyrins and chlorins. , 1972, Journal of the American Chemical Society.

[3]  A. Lever,et al.  Phthalocyanines : properties and applications , 1989 .

[4]  Roger Guilard,et al.  The porphyrin handbook , 2002 .

[5]  P. Seybold,et al.  Porphyrins. XIII: Fluorescence spectra and quantum yields , 1969 .

[6]  Peter Liljeroth,et al.  Current-Induced Hydrogen Tautomerization and Conductance Switching of Naphthalocyanine Molecules , 2007, Science.

[7]  Y. Kobuke.  Artificial Light‐Harvesting Systems by Use of Metal Coordination , 2006 .

[8]  S. Eaton,et al.  Kinetic isotope effect on proton tautomerism in tetraarylporphyrins. , 1977, Journal of the American Chemical Society.

[9]  Tymish Y. Ohulchanskyy,et al.  Photosensitizers Derived from 132-Oxo-methyl Pyropheophorbide-a: Enhanced Effect of Indium(III) as a Central Metal in In Vitro and In Vivo Photosensitizing Efficacy , 2006, Photochemistry and photobiology.

[10]  R. Nolte,et al.  Molecular Materials by Self‐Assembly of Porphyrins, Phthalocyanines, and Perylenes , 2006 .

[11]  E. Vogel,et al.  NMR Study of the Tautomerism of Porphyrin Including the Kinetic HH/HD/DD Isotope Effects in the Liquid and the Solid State , 1994 .

[12]  M. Boronat,et al.  Theoretical study of the NH tautomerism in free base porphyrin , 1997 .

[13]  John A. Nelder,et al.  A Simplex Method for Function Minimization , 1965, Comput. J..

[14]  J. Knutson,et al.  Decay-associated fluorescence spectra and the heterogeneous emission of alcohol dehydrogenase. , 1982, Biochemistry.

[15]  G. Gurinovich,et al.  NH tautomerism and visible absorption spectra of porphyrins with asymmetrical substitution: Oscillator model and MO calculations , 1985 .

[16]  G. Gurinovich,et al.  Spectral peculiarities of NH-tautomerism in isocycle-containing porphyrins and their covalently linked dimers , 1984 .

[17]  N. Jux.  o-(Bromomethyl)-substituted tetraarylporphyrin building blocks. , 2000, Organic letters.

[18]  J. Hennig,et al.  Localization and Transfer of Protons between 15N Atoms of meso-Tetraphenylporphine Probed by Nuclear Overhauser Effects and Dipole-Dipole Relaxation Times , 1984 .

[19]  N. Kobayashi.  Dimers, trimers and oligomers of phthalocyanines and related compounds , 2002 .

[20]  A. Harriman,et al.  Luminescence of porphyrins and metalloporphyrins. Part 10.—Mixed-metal dimers , 1985 .

[21]  M. Drobizhev,et al.  Very efficient two-photon induced photo-tautomerization in non-symmetrical phthalocyanines , 2008 .

[22]  Gene H. Golub,et al.  The differentiation of pseudo-inverses and non-linear least squares problems whose variables separate , 1972, Milestones in Matrix Computation.

[23]  J. Lakowicz.  Principles of fluorescence spectroscopy , 1983 .

[24]  J. Michl,et al.  Fourier transform fluorescence and phosphorescence of porphine in rare gas matrices , 1991 .

[25]  K. Berg,et al.  Porphyrin‐related photosensitizers for cancer imaging and therapeutic applications , 2005, Journal of microscopy.

[26]  Steffen Hackbarth,et al.  Singlet Oxygen Quantum Yields of Different Photosensitizers in Polar Solvents and Micellar Solutions , 1998 .

[27]  B. Röder,et al.  Novel Synthetic Cycloketo-Tetraphenylporphyrins , 2007 .

[28]  A. Harriman,et al.  Metal phthalocyanines and porphyrins as photosensitizers for reduction of water to hydrogen , 1982 .

[29]  M. Drobizhev,et al.  Photo-tautomer of Br-porphyrin: a new frequency-selective material for ultrafast time–space holographic storage , 2000 .

[30]  A. Zeug,et al.  On the Influence of Higher Excited States on the ISC Quantum Yield of Octa‐aL‐alkyloxy‐substituted Zn‐Phthalocyanine Molecules Studied by Nonlinear Absorption , 1997 .

[31]  Michael Kasha,et al.  Characterization of electronic transitions in complex molecules , 1950 .

[32]  A. Harriman.  Luminescence of porphyrins and metalloporphyrins. Part 3.—Heavy-atom effects , 1981 .

[33]  B. Röder,et al.  Photoinduced electron and energy transfer in a new porphyrin–phthalocyanine triad , 2006 .

[34]  C. Moore,et al.  Hydrogen atom tunneling in the thermal tautomerism of porphine imbedded in a n-hexane matrix , 1988 .

[35]  D. Holten,et al.  Conformational and Electronic Effects of Phenyl-Ring Fluorination on the Photophysical Properties of Nonplanar Dodecaarylporphyrins , 2001 .

[36]  I. Renge.  Symmetry and hole-burning properties of porphyrins , 2002 .

[37]  P. Hynninen,et al.  Research advances in the use of tetrapyrrolic photosensitizers for photodynamic therapy. , 2004, Journal of photochemistry and photobiology. B, Biology.

[38]  Michael R Hamblin,et al.  Mechanisms in photodynamic therapy: part two-cellular signaling, cell metabolism and modes of cell death. , 2005, Photodiagnosis and photodynamic therapy.