Photoisomerization among ring-open merocyanines. I. Reaction dynamics and wave-packet oscillations induced by tunable femtosecond pulses

Ruetzel, Stefan; Diekmann, Meike; Nuernberger, Patrick; Walter, Christof; Engels, Bernd; Brixner, Tobias

doi:10.1063/1.4881258

Cited by 37 publications

(53 citation statements)

References 65 publications

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“…2), which has been studied extensively with femtosecond transient absorption spectroscopy (see Paper I). 11 According to the experiments, the TTC (transtrans-cis) isomer predominates in acetonitrile, while excitation in the visible range of the spectrum leads to an increase of the TTT (trans-trans-trans) isomer due to an ultrafast excitedstate photoisomerization TTC → TTT within 200 fs (see a) Electronic mail: brixner@phys-chemie.uni-wuerzburg.de b) Electronic mail: bernd.engels@mail.uni-wuerzburg.de Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

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Photoisomerization among ring-open merocyanines. II. A computational study

Walter

Ruetzel

Diekmann

et al. 2014

The Journal of Chemical Physics

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The photochemical isomerization of the trans-trans-cis to the trans-trans-trans isomer of the merocyanine form of 6-nitro BIPS, which has been studied with femtosecond transient absorption spectroscopy [S. Ruetzel, M. Diekmann, P. Nuernberger, C. Walter, B. Engels, and T. Brixner, J. Chem. Phys. 140, 224310 (2014)], is investigated using time-dependent density functional theory in conjunction with polarizable continuum models. Benchmark calculations against SCS-ADC(2) evaluate the applicability of the CAM-B3LYP functional. Apart from a relaxed scan in the ground state with additional computation of the corresponding excitation energies, which produces the excited-state surface vertical to the ground-state isomerization coordinate, a relaxed scan in the S1 gives insight into the geometric changes orthogonal to the reaction coordinate and the fluorescence conditions. The shape of the potential energy surface (PES) along the reaction coordinate is found to be highly sensitive to solvation effects, with the method of solvation (linear response vs. state-specific) being critical. The shape of the PES as well as the computed harmonic frequencies in the S1 minima are in line with the experimental results and offer a straightforward interpretation.

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Section: Introductionmentioning

confidence: 99%

“…This challenging entanglement of geometry and electronic character makes the MCs an ideal model system for the investigation of the photochemical behavior with ultrafast time-resolved techniques (such as coherent multidimensional spectroscopy 17,18 or transient absorption [9][10][11] ).…”

Section: Introductionmentioning

confidence: 99%

Photoisomerization among ring-open merocyanines. II. A computational study

Walter

Ruetzel

Diekmann

et al. 2014

The Journal of Chemical Physics

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“…ron transfer, 28 internal conversion, 2 light-activated geometry changes, 5 conical intersections, 7 photoisomerization, 1,20,29,41 photodissociation, 42,43 and coherent phonons in polymers and crystals. [44][45][46] In order to investigate the dynamics revealed in transient absorption spectra, populations and oscillations are currently treated separately.…”

Section: Introductionmentioning

confidence: 99%

“…Time traces at single detection wavelengths are either Fourier transformed, or fitted with damped cosines. 1,2,4,25,27,41,47 Next, for a few dominant frequencies the amplitude and phase can be plotted as function of the detection wavelength. No attempt has been made yet to globally analyze the complete data.…”

Section: Introductionmentioning

confidence: 99%

Estimation of damped oscillation associated spectra from ultrafast transient absorption spectra

Stokkum

Jumper

Snellenburg

et al. 2016

The Journal of Chemical Physics

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When exciting a complex molecular system with a short optical pulse, all chromophores present in the system can be excited. The resulting superposition of electronically and vibrationally excited states evolves in time, which is monitored with transient absorption spectroscopy. We present a methodology to resolve simultaneously the contributions of the different electronically and vibrationally excited states from the complete data. The evolution of the excited states is described with a superposition of damped oscillations. The amplitude of a damped oscillation cos(ωnt)exp(−γnt) as a function of the detection wavelength constitutes a damped oscillation associated spectrum DOASn(λ) with an accompanying phase characteristic φn(λ). In a case study, the cryptophyte photosynthetic antenna complex PC612 which contains eight bilin chromophores was excited by a broadband optical pulse. Difference absorption spectra from 525 to 715 nm were measured until 1 ns. The population dynamics is described by four lifetimes, with interchromophore equilibration in 0.8 and 7.5 ps. We have resolved 24 DOAS with frequencies between 130 and 1649 cm−1 and with damping rates between 0.9 and 12 ps−1. In addition, 11 more DOAS with faster damping rates were necessary to describe the “coherent artefact.” The DOAS contains both ground and excited state features. Their interpretation is aided by DOAS analysis of simulated transient absorption signals resulting from stimulated emission and ground state bleach.

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“…Triplet emission (phosphorescence) of the closed-ring isomer was previously observed at low temperatures, [31,32] and in media of high viscosity, including glasses, [33] ionic liquids, [34] and electrospun fibers [35] -however, the emergence of the band centered at approximately 450 nm , insulin fibrils(red), and in the absenceo fp rotein (gray;i na ll cases, the excitationwavelengthwas 390 nm). [30,51,52] The small peak at approximately 450 nm can be attributed to Raman scattering of the excitation beam by waterm olecules. Right:Photographs of the corresponding solutions excitedw ith ah and-held, long-wave (365 nm) UV lamp.…”

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Noncovalent Interactions with Proteins Modify the Physicochemical Properties of a Molecular Switch

et al. 2015

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It is reported that spiropyran-aw idely investigated molecular photoswitch-can be stabilized in aqueous environments in the presence of av ariety of proteins, including human serum albumin, insulinf ibrils, lysozyme, and glucoseo xidase. The optical properties of the complexed photoswitch are protein dependent, with humans erum albumin providing the spiropyran with emission features previously observed for ap hotoswitch confined in media of high viscosity.D espite being bound to the protein molecules,s piropyranc an undergo ar ing-opening reactionu pon exposure to UV light. This photoisomerization process can affect the properties of the proteins:h ere, it is shown that the electrical conduction through humans erum albumin to which the spiropyran is bound increases following the ring-opening reaction.Bacteriorhodopsinh as long impressed scientists with the elegance with whichi tu ses the energy of sunlight to guide the motion of protons across cell membranes. This functioni se nabled by ap hotoswitchabler etinal moiety strategically positioned within the protein structure;light-induced isomerization of retinal triggersacascade of reactions, resulting in proton transfer against apHgradient. [1,2] Inspired by this and other examples, [3] chemists have developed different strategies to covalently immobilize photoswitchablem olecules within various biomacromolecules, [4][5][6][7][8][9] with the primary goal of controlling their structures and/or functions. Attractive and diverse applications have become possible, including photoswitchable enzymaticc atalysis [10,11] and light-actuated ion transport through ac hannel protein. [12] Herein, we considered as impler approach, which takes advantage of noncovalent interactions [13,14] between am olecular switch (in our case, spiropyran [15][16][17][18][19] )a nd the target protein. We found that av ariety of proteins, including human serum albumin (HSA), insulin, glucoseo xidase, and lysozyme can provide the spiropyran with good water solubility,i ndicating the formation of protein-spiropyranc omplexes. Within these complexes,s piropyran remained photoresponsive;h owever,i ts optical properties depended on which protein "host" it was bound to. We also found that photoisomerization of spiropyran bound to the serum albuminr esults in markedlyi ncreased electricalconduction through the protein.We worked with the most widely investigated spiropyran-1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] (1,F igure 1a;S ection S1 in the Supporting Information). This compound is practically insoluble in water,a s evidenced by an experiment in which we injected 8.6 mLo f a3 .5 mm solutiono f1 in DMSO into 1mLo faphosphate-buffered saline (PBS;5m m phosphate, 70 mm NaCl, pH 8). The characteristic optical response of 1 disappeared within 4h,i ndicatingq uantitative precipitation (Figure 1b). However,w hen the same amount of 1 wasi njected into the buffer solution containing HSA at 30 mm (an equimolar ratio of 1 to the protein), the spiropyran remained soluble...

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Photoisomerization among ring-open merocyanines. I. Reaction dynamics and wave-packet oscillations induced by tunable femtosecond pulses

Cited by 37 publications

References 65 publications

Photoisomerization among ring-open merocyanines. II. A computational study

Photoisomerization among ring-open merocyanines. II. A computational study

Estimation of damped oscillation associated spectra from ultrafast transient absorption spectra

Noncovalent Interactions with Proteins Modify the Physicochemical Properties of a Molecular Switch

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