Photoisomerization and relaxation dynamics of a structurally modified biomimetic photoswitch.

Recent experimental and theoretical studies on N-alkylated indanylidene pyrroline Schiff bases (NAIP) show that these compounds exhibit biomimetic photoisomerization analogous to that in the chromophore of rhodopsin. The NAIP compounds studied previously isomerize rapidly and often evolve coherently on the ground-electronic surface after reaction. We present the results of transient electronic absorption spectroscopy on dMe-OMe-NAIP, a newly synthesized NAIP analogue that differs from other NAIP compounds in the substituents on its pyrrolinium ring. Following excitation with 400 nm light, dMe-OMe-NAIP relaxes from the electronic-excited state in less than 500 fs, which is slower than in other analogues, and does not show the prominent oscillations observed in other NAIP compounds. A reduction in the amount of twisting between the rings caused by removal of the methyl group is likely responsible for the slower isomerization. Measurements in solvents of varying viscosity and structure suggest that intramolecular processes dominate the relaxation of nascent photoproducts.

[1]  Roland Lindh,et al.  The ultrafast photoisomerizations of rhodopsin and bathorhodopsin are modulated by bond length alternation and HOOP driven electronic effects. , 2011, Journal of the American Chemical Society.

[2]  R A Mathies,et al.  Vibrationally coherent photochemistry in the femtosecond primary event of vision. , 1994, Science.

[3]  B. Abel,et al.  Intramolecular vibrational energy redistribution in aromatic molecules of type C₆H₅X (X = H, D, F, Cl, CH₃, CF₃). , 2010, The journal of physical chemistry. A.

[4]  N. Ferré,et al.  Modeling, preparation, and characterization of a dipole moment switch driven by Z/E photoisomerization. , 2010, Journal of the American Chemical Society.

[5]  T. Aida,et al.  Photoisomerization in dendrimers by harvesting of low-energy photons , 1997, Nature.

[6]  N. Ferré,et al.  An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds , 2008, Proceedings of the National Academy of Sciences.

[7]  He Tian,et al.  Recent progresses on diarylethene based photochromic switches. , 2004, Chemical Society reviews.

[8]  D. Bingemann,et al.  Transient electronic absorption of vibrationally excited CH2I2: Watching energy flow in solution , 2000 .

[9]  L. Sheps,et al.  Relaxation of the C–H stretching fundamental vibrations of CHI3,CH2I2, and CH3I in solution , 2002 .

[10]  M. Olivucci,et al.  Photoisomerization acceleration in retinal protonated Schiff-base models. , 2003, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.

[11]  Shayu Li,et al.  Light-harvesting and photoisomerization in benzophenone and norbornadiene-labeled poly(aryl ether) dendrimers via intramolecular triplet energy transfer. , 2005, Journal of the American Chemical Society.

[12]  D. Schwarzer,et al.  Intramolecular vibrational energy redistribution and intermolecular energy transfer of benzene in supercritical CO2: measurements from the gas phase up to liquid densities , 2004 .

[13]  C. Elles,et al.  Vibrational relaxation of CH3I in the gas phase and in solution. , 2004, The Journal of chemical physics.

[14]  David S. Boucher,et al.  The influence of vibrational excitation on the photoisomerization of trans-stilbene in solution. , 2010, The journal of physical chemistry. A.

[15]  D. Bingemann,et al.  CH2I2 fundamental vibrational relaxation in solution studied by transient electronic absorption spectroscopy , 2001 .

[16]  C. Ruckebusch,et al.  Investigation of ultrafast photoinduced processes for salicylidene aniline in solution and gas phase: toward a general photo-dynamical scheme , 2010, Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology.

[17]  C. Pedregal,et al.  Synthesis of Enantiomerically Pure 4-Substituted Glutamic Acids and Prolines: General Aldol Reaction of Pyroglutamate Lactam Lithium Enolate Mediated by Et2O.cntdot.BF3 , 1995 .

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

[19]  Robert S. H. Liu,et al.  Mechanism of Photoisomerization of 1‐Naphthyl‐2‐Phenylethylenes in Organic Glasses , 2007, Photochemistry and photobiology.

[20]  M. Chergui,et al.  Coherent ultrafast torsional motion and isomerization of a biomimetic dipolar photoswitch. , 2010, Physical chemistry chemical physics : PCCP.

[21]  M. Baer,et al.  The role of degenerate states in chemistry , 2002 .

[22]  C. Renner,et al.  A photocontrolled beta-hairpin peptide. , 2006, Chemistry.

[23]  Luis Moroder,et al.  Picosecond conformational transition and equilibration of a cyclic peptide , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[24]  R. Mathies,et al.  The first step in vision occurs in femtoseconds: complete blue and red spectral studies. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[25]  David H. Waldeck.  Photoisomerization dynamics of stilbenes , 1991 .

[26]  Benjamin G. Levine,et al.  Isomerization through conical intersections. , 2007, Annual review of physical chemistry.

[27]  C. Elles,et al.  Connecting chemical dynamics in gases and liquids. , 2006, Annual review of physical chemistry.

[28]  R. Hochstrasser,et al.  Vibrational relaxation dynamics in solutions. , 1994, Annual review of physical chemistry.

[29]  M. Olivucci,et al.  Toward a stable α-cycloalkyl amino acid with a photoswitchable cationic side chain. , 2012, The Journal of organic chemistry.

[30]  B. Pate,et al.  Vibrational Dynamics of Terminal Acetylenes: II. Pathway for Vibrational Relaxation in Gas and Solution , 2004 .

[31]  Luis Moroder,et al.  Single-Molecule Optomechanical Cycle , 2002, Science.

[32]  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.

[33]  B. Mudryk,et al.  One-pot synthesis of cyclic enecarbamates from lactam carbamates , 2005 .

[34]  Mark S Gordon,et al.  Photoisomerization of stilbene: a spin-flip density functional theory approach. , 2011, The journal of physical chemistry. A.