Synthesis of biomimetic light-driven molecular switches via a cyclopropyl ring-opening/nitrilium ion ring-closing tandem reaction

Zanirato, Vinicio; Pollini, G. P.; Risi, Carmela De; Valente, Filippo; Melloni, Alfonso; Fusi, Stefania; Barbetti, Jacopo; Olivucci, Massimo

doi:10.1016/j.tet.2007.03.141

Cited by 24 publications

(24 citation statements)

References 31 publications

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“…However, this can be implemented only in switches where an ultrafast photochemical reaction produces a product with a nonstatistical distribution of the vibrational energy polarized on the reactive (Z 3 E or E 3 Z) mode. It is likely that, after insertion of a stereogenic center in position 2, 3, or 2Ј [the synthetic routes do not exclude such possibility (22)], NAIP switches could provide this type of system. In fact, as shown above, upon decay from S 1 , Ͼ 25 kcal⅐mol Ϫ1 of kinetic energy are predicted to be located on the isomerization mode.…”

Section: Discussionmentioning

confidence: 99%

“…To address this problem, we have shown (21) that, in methanol solution, the N-alkylated indanylidene-pyrroline Schiff base (NAIP) 1 displays excited-state properties similar to those of Rh-embedded PSB11. We have also shown that NAIPs can be prepared in good yields (Ͼ80%) through a cyclopropyl ringopening/nitrilium ring-closing tandem reaction (22).…”

mentioning

confidence: 83%

“…Z-1, prepared as described in ref. 22, was dissolved in methanol-d4 dried over molecular sieves for the IR experiments and in spectroscopy grade MeOH for the UV-vis pump-probe experiments. Solutions of Ϸ10 mmol/L were used for time-resolved IR spectroscopy in a 100-m-thick flow cell (OD 0.8 -1.2 at the S0 3 S1 absorption maximum at 390 nm).…”

Section: Methodsmentioning

confidence: 99%

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An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds

Sinicropi

Martin

Ryazantsev

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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161

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Single molecules that act as light-energy transducers (e.g., converting the energy of a photon into atomic-level mechanical motion) are examples of minimal molecular devices. Here, we focus on a molecular switch designed by merging a conformationally locked diarylidene skeleton with a retinal-like Schiff base and capable of mimicking, in solution, different aspects of the transduction of the visual pigment Rhodopsin. Complementary ab initio multiconfigurational quantum chemistry-based computations and time-resolved spectroscopy are used to follow the light-induced isomerization of the switch in methanol. The results show that, similar to rhodopsin, the isomerization occurs on a 0.3-ps time scale and is followed by <10-ps cooling and solvation. The entire (2-photon-powered) switch cycle was traced by following the evolution of its infrared spectrum. These measurements indicate that a full cycle can be completed within 20 ps.CASPT2//CASSCF ͉ mid-IR ͉ photochemical switch ͉ time resolved spectroscopy ͉ UV-vis M olecular switches based on photochemical E/Z isomerizations have been used in different contexts to convert light energy into ''mechanical'' motion at the molecular level (1-3). For instance, switches based on azobenzene have been used to control ion complexation (4, 5), electronic properties (6), catalysis (7), and the folding of peptides (8-13) whereas diarylidenes have provided the framework for the construction of rotary motors and transmissions (14). The computer modeling of switches that differ in size, polarity, and isomerization mechanism represents an attractive research target (15) yielding building blocks to be used in diverse molecular environments. However, this cannot be limited to the computation of equilibrium properties but requires the description of the entire photocycle. In other words, one needs to compute the potential energy surfaces controlling the switch E 3 Z and Z 3 E excited-state evolution, its decay and ground state relaxation, and the competing thermal E/Z isomerization in the proper environment (e.g., in solution or in a biomolecule backbone). The complexity of these calculations impedes the study of candidates that are intractable with accurate quantum chemical methods (allowing comparison with spectroscopic data) or that feature, as for azobenzene and diarylidenes (16), more than 1 low-lying excited state, leading to a plethora of reaction paths to be computed.The retinal protonated Schiff-base chromophore of rhodopsins (17-19) constitutes an example of an E/Z switch shaped by biological evolution that can be modeled with quantitative computations (20). In bovine rhodopsin (Rh), a selective photoisomerization of the 11-cis chromophore (PSB11) occurs via evolution of a single 3 * excited state (S 1 ) that survives for only 150 fs and yields, upon decay, the all-trans ground state (S 0 ) product with a 67% quantum yield (16,20). Although these properties make Rh an excellent reference for the design of E/Z switches, irradiation of PSB11 in solution (26, 27) features an unselec...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 83%

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An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds

Sinicropi

Martin

Ryazantsev

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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161

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“…We have also shown that NAIPs can be prepared in good yields (>80%) through a cyclopropyl ring-opening/nitrilium ring-closing tandem reaction. [111] As detailed below for the photoisomerization of G1 = -OMe and G2 = -CH 2 -(structure 1 hereafter) we have shown that QM/MM calculations based on the same methodology used for proteins and featuring a multiconfigurational second-order perturbation theory treatment, reveal E-1 → Z-1 and Z-1 → E-1 isomerization paths that intercept CIs on a ∼200 fs time scale. [110] These features have been examined by time-resolved ultraviolet-visible (UV-Vis) absorption, emission, and mid-infrared (mid-IR) spectroscopy and show that the Z → E → Z photocycle is completed in picoseconds.…”

Section: Biomimetic Compoundsmentioning

confidence: 99%

Computational Photobiology and Beyond

et al. 2010

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In this paper we review the results of a group of computational studies of the spectroscopy and photochemistry of light-responsive proteins. We focus on the use of quantum mechanics/molecular mechanics protocols based on a multiconfigurational quantum chemical treatment. More specifically, we discuss the use, limitations, and application of the ab initio CASPT2//CASSCF protocol that, presently, constitutes the method of choice for the investigation of excited state organic molecules, most notably, biological chromophores and fluorophores. At the end of this Review we will also see how the computational investigation of the visual photoreceptor rhodopsin is providing the basis for the design of light-driven artificial molecular devices.

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“…(5.251)]. 699 Cyclic imines are obtained in the related transformation of methylenecyclpropanes with nitriles mediated by triflic acid 700 Dihydroquinoline derivatives are synthesized in intramolecular hetero Diels-Alder reaction from a-(alkynylsiloxy)aldimines in triflic acid 702 Efficient synthetic methods have been developed for the synthesis of 4functionalized quinolines mediated by triflic acid. Catalyst recycling was possible after reactivation with oxidizing agents (nitric acid or hydrogen peroxide).…”

Section: ð5:250þmentioning

confidence: 99%