Acceleration of the Z to E photoisomerization of penta-2,4-dieniminium by hydrogen out-of-plane motion: theoretical study on a model system of retinal protonated Schiff base.

We report the result of comparison between two reaction coordinates [on the potential energy surface of the first excited state (S(1))] produced by CASSCF and these energies recalculated by MRMP2 in the Z to E photoisomerization of penta-2,4-dieniminium (PDI) as the minimal model of the retinal protonated Schiff base (RPSB). One coordinate is the S(1) state minimum-energy-path (MEP) in mass-weighted coordinates from the S(1) vertically excited point, where a strong hydrogen-out-of plane (HOOP) motion is not exhibited. The energy profile of the S(1) MEP at the MRMP2//CASSCF level shows a barrier for the rotation around the reactive C-C and hits the S(1)/S(0) degeneracy space where the central C-C-C-C dihedral angle is distorted by 65 degrees . The other coordinate is an S(1) coordinate obtained by the relaxed scan strategy. The relaxed coordinate along the central C-C-C-C dihedral angle, which we call the HOOP coordinate, shows strong HOOP motion. According to the MRMP2//CASSCF calculation, there is no barrier on the HOOP coordinate. Furthermore, the S(1) to S(0) transition may be possible without the large skeletal deformation by HOOP motion because the HOOP coordinate encounters the S(1)/S(0) degeneracy space where the central C-C-C-C dihedral angle is distorted by only 40 degrees . Consequently, if PDI is a suitable model molecule for the RPSB as often assumed, the 11-cis to all-trans photoisomerization is predicted to be accelerated by the HOOP motion.

[1]  Oliver Weingart,et al.  The role of HOOP-modes in the ultrafast photo-isomerization of retinal models , 2008 .

[2]  N. Mataga,et al.  Excited-state dynamics of rhodopsin probed by femtosecond fluorescence spectroscopy , 2001 .

[3]  Kazuya Saito,et al.  Theoretical study on hula-twist motion of penta-2,4-dieniminium on the S1 surface under isolated condition by the complete active space self-consistent field theory , 2006 .

[4]  Massimo Olivucci,et al.  Probing the Photochemical Funnel of a Retinal Chromophore Model via Zero-Point Energy Sampling Semiclassical Dynamics. , 2004 .

[5]  Marco Garavelli,et al.  Minimum energy paths in the excited and ground states of short protonated Schiff bases and of the analogous polyenes , 1998 .

[6]  Marco Garavelli,et al.  Structure, spectroscopy, and spectral tuning of the gas-phase retinal chromophore: the beta-ionone "handle" and alkyl group effect. , 2005, The journal of physical chemistry. A.

[7]  Mark S. Gordon,et al.  General atomic and molecular electronic structure system , 1993, J. Comput. Chem..

[8]  Massimo Olivucci,et al.  CASPT2//CASSCF and TDDFT//CASSCF mapping of the excited state isomerization path of a minimal model of the retinal chromophore , 2004 .

[9]  F. Bernardi,et al.  Reaction path analysis of the "tunable" photoisomerization selectivity of free and locked retinal chromophores. , 2002, Journal of the American Chemical Society.

[10]  F. Bernardi,et al.  The short-chain acroleiniminium and pentadieniminium cations: towards a model for retinal photoisomerization. A CASSCF/PT2 study , 1999 .

[11]  Thom Vreven,et al.  Photoisomerization Path for a Realistic Retinal Chromophore Model: The Nonatetraeniminium Cation , 1998 .

[12]  H. Bernhard Schlegel,et al.  Reaction Path Following in Mass-Weighted Internal Coordinates , 1990 .

[13]  O. Takahashi,et al.  Characterization of the hyperline of D1/D0 conical intersections between the maleic acid and fumaric acid anion radicals. , 2004, Journal of Chemical Physics.

[14]  Y. Shichida,et al.  Deuterium substitution effect on the excited-state dynamics of rhodopsin , 1998 .

[15]  L. Stryer,et al.  Resonance Raman studies of the conformation of retinal in rhodopsin and isorhodopsin. , 1977, Journal of molecular biology.

[16]  Kazuya Saito,et al.  Ab initio study on one-way photoisomerization of the maleic acid and fumaric acid anion radical system as a model system of their esters. , 2006, The journal of physical chemistry. A.

[17]  M Olivucci,et al.  Computational evidence in favor of a two-state, two-mode model of the retinal chromophore photoisomerization. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[18]  O. Takahashi,et al.  A note on geometric constraints in conical intersection optimizations , 2005 .

[19]  Thom Vreven,et al.  Potential-energy surfaces for ultrafast photochemistry Static and dynamic aspects , 1998 .

[20]  Ralph S. Becker,et al.  A comprehensive investigation of the mechanism and photophysics of isomerization of a protonated and unprotonated Schiff base of 11-cis-retinal , 1985 .

[21]  F. Bernardi,et al.  The retinal chromophore/chloride ion pair: structure of the photoisomerization path and interplay of charge transfer and covalent states. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[22]  Potential energy surface crossings in organic photochemistry , 1996 .

[23]  Marco Garavelli,et al.  The C 5 H 6 NH 2 + Protonated Shiff Base: An ab Initio Minimal Model for Retinal Photoisomerization , 1997 .

[24]  Massimo Olivucci,et al.  Structure, initial excited-state relaxation, and energy storage of rhodopsin resolved at the multiconfigurational perturbation theory level , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[25]  N. Ferré,et al.  Tracking the excited-state time evolution of the visual pigment with multiconfigurational quantum chemistry , 2007, Proceedings of the National Academy of Sciences.

[26]  Y. Koyama,et al.  EFFECT OF PROTONATION ON THE ISOMERIZATION PROPERTIES OF n‐BUTYLAMINE SCHIFF BASE OF ISOMERIC RETINAL AS REVEALED BY DIRECT HPLC ANALYSES: SELECTION OF ISOMERIZATION PATHWAYS BY RETINAL PROTEINS , 1991, Photochemistry and photobiology.

[27]  Richard A. Mathies,et al.  Vibrational Assignment of Torsional Normal Modes of Rhodopsin: Probing Excited-State Isomerization Dynamics along the Reactive C11C12 Torsion Coordinate , 1998 .

[28]  Dage Sundholm,et al.  Stairway to the conical intersection: a computational study of the retinal isomerization. , 2007, The journal of physical chemistry. A.

[29]  Massimo Olivucci,et al.  Relationship between photoisomerization path and intersection space in a retinal chromophore model. , 2003, Journal of the American Chemical Society.

[30]  Ming Yan,et al.  Femtosecond Dynamics of Rhodopsin Photochemistry Probed by a Double Pump Spectroscopic Approach , 2001 .

[31]  G. Kochendoerfer,et al.  Spontaneous Emission Study of the Femtosecond Isomerization Dynamics of Rhodopsin , 1996 .

[32]  B. Roos,et al.  A complete active space SCF method (CASSCF) using a density matrix formulated super-CI approach , 1980 .

[33]  R R Alfano,et al.  Fluorescence quantum yield of visual pigments: evidence for subpicosecond isomerization rates. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[34]  M. Olivucci,et al.  Complex excited dynamics around a plateau on a retinal-like potential surface: chaos, multi-exponential decays and quantum/classical differences , 2007 .

[35]  M. Garavelli,et al.  Substituent-controlled photoisomerization in retinal chromophore models: Fluorinated and methoxy-substituted protonated Schiff bases , 2007 .

[36]  P. Anfinrud,et al.  The photoisomerization of retinal in bacteriorhodospin: experimental evidence for a three-state model. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[37]  M. Olivucci,et al.  A tiny excited-state barrier can induce a multiexponential decay of the retinal chromophore: a quantum dynamics investigation. , 2005, Angewandte Chemie.

[38]  Haruyuki Nakano,et al.  Quasidegenerate perturbation theory with multiconfigurational self‐consistent‐field reference functions , 1993 .

[39]  Massimo Olivucci,et al.  Probing the rhodopsin cavity with reduced retinal models at the CASPT2//CASSCF/AMBER level of theory. , 2003, Journal of the American Chemical Society.

[40]  R. Mathies,et al.  Structural Observation of the Primary Isomerization in Vision with Femtosecond-Stimulated Raman , 2005, Science.

[41]  Marco Garavelli,et al.  About the intrinsic photochemical properties of the 11-cis retinal chromophore: computational clues for a trap state and a lever effect in Rhodopsin catalysis , 2007 .