Cross-phase modulation in visible-pump/mid-infrared-probe spectroscopy

Lapini, Andrea; Vazquez, Sandra Mosquera; Touceda, Patricia Tourón; Lima, Manuela

doi:10.1016/j.molstruc.2010.11.042

Cited by 10 publications

(9 citation statements)

References 7 publications

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“…The first exponential reproduces the cross-phase modulation artefact (XPM) that affects the first 100 fs. [77][78][79] Transient absorption and stimulated emission bands grow-up with the same rise time that, taking into account the XPM, is comparable with our temporal resolution. This means that they are associated with transitions occurring from the same excited state and that the excitation of Dn with l exc = 325 nm directly populates the first singlet excited state (S 1 ).…”

Section: Time-resolved Measurementssupporting

confidence: 81%

Ultrafast resonance energy transfer in the umbelliferone–alizarin bichromophore

Lapini

Fabbrizzi

Piccardo

et al. 2014

Phys. Chem. Chem. Phys.

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In this work we present the synthesis, time-resolved spectroscopic characterization and computational analysis of a bichromophore composed of two very well-known naturally occurring dyes: 7-hydroxycoumarin (umbelliferone) and 1,2-dihydroxyanthraquinone (alizarin). The umbelliferone donor (Dn) and alizarin acceptor (Ac) moieties are linked to a triazole ring viaσ bonds, providing a flexible structure. By measuring the fluorescence quantum yields and the ultrafast transient absorption spectra we demonstrate the high efficiency (∼85%) and the fast nature (∼1.5 ps) of the energy transfer in this compound. Quantum chemical calculations, within the density functional theory (DFT) approach, are used to characterize the electronic structure of the bichromophore (Bi) in the ground and excited states. We simulate the absorption and fluorescence spectra using the TD-DFT methods and the vertical gradient approach (VG), and include the solvent effects by adopting the conductor-like polarizable continuum model (CPCM). The calculated electronic structure suggests the occurrence of weak interactions between the electron densities of Dn and Ac in the excited state, indicating that the Förster-type transfer is the appropriate model for describing the energy transfer in this system. The average distance between Dn and Ac moieties calculated from the conformational analysis (12 Å) is in very good agreement with the value estimated from the Förster equation (∼11 Å). At the same time, the calculated rate constant for energy transfer, averaged over multiple conformations of the system (3.6 ps), is in reasonable agreement with the experimental value (1.6 ps) estimated by transient absorption spectroscopy. The agreement between experimental results and computational data leads us to conclude that the energy transfer in Bi is well described by the Förster mechanism.

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Section: Time-resolved Measurementssupporting

confidence: 81%

Ultrafast resonance energy transfer in the umbelliferone–alizarin bichromophore

Lapini

Fabbrizzi

Piccardo

et al. 2014

Phys. Chem. Chem. Phys.

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“…For the quantitative analysis of the time-resolved spectral data we used a combined approach, consisting of singular values decomposition (SVD) and the simultaneous fitting of all the collected kinetic traces (global analysis). To avoid the contribution due to perturbed free induction decay and cross-phase modulation, − we excluded from our analysis the spectra measured for delays shorter than 500 fs. First, we extrapolated the number of components using SVD; − then we analyzed the whole ensemble of kinetic data by means of a global fitting procedure.…”

Section: Methodsmentioning

confidence: 99%

Carbon Monoxide Recombination Dynamics in Truncated Hemoglobins Studied with Visible-Pump MidIR-Probe Spectroscopy

Lapini¹,

Donato

Patrizi³

et al. 2012

J. Phys. Chem. B

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Carbon monoxide recombination dynamics upon photodissociation with visible light has been characterized by means of ultrafast visible-pump/MidIR probe spectroscopy for the truncated hemoglobins from Thermobifida fusca and Bacillus subtilis. Photodissociation has been induced by exciting the sample at two different wavelengths: 400 nm, corresponding to the heme absorption in the B-band, and 550 nm, in the Q-bands. The bleached iron-CO coordination band located at 1850-1950 cm(-1) and the free CO absorption band in the region 2050-2200 cm(-1) have been observed by probe pulses tuned in the appropriate infrared region. The kinetic traces measured at 1850-1950 cm(-1) reveal multiexponential subnanosecond dynamics that have been interpreted as arising from fast geminate recombination of the photolyzed CO. A compared analysis of the crystal structure of the two proteins reveals a similar structure of their distal heme pocket, which contains conserved polar and aromatic amino acid residues closely interacting with the iron ligand. Although fast geminate recombination is observed in both proteins, several kinetic differences can be evidenced, which can be interpreted in terms of a different structural flexibility of the corresponding heme distal pockets. The analysis of the free CO band-shape and of its dynamic evolution brings out novel features about the nature of the docking site inside the protein cavity.

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“…For the quantitative analysis of the time resolved spectral data we used a combined approach, consisting of singular values decomposition and global fitting (global analysis). In order to avoid the contribution due to perturbed free induction decay and cross-phase modulation, [30][31][32][33][34] we excluded from our analysis the spectra measured for delays shorter than 500 fs. First, we extrapolated the number of components using Singular Values Decomposition (SVD); then we analyzed the whole ensemble of kinetic data by means of a global fitting procedure.…”

Section: Discussionmentioning

confidence: 99%

Transient infrared spectroscopy: a new approach to investigate valence tautomerism

Patricia¹,

Sandra²,

Lima³

et al. 2012

Phys. Chem. Chem. Phys.

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In this work we present, to our knowledge for the first time, the results of a transient infrared spectroscopic study of the photoinduced valence tautomerism process in cobalt-dioxolene complexes with sub-picosecond time resolution. The molecular systems investigated were [Co(tpa)(diox)]PF(6) (1) and [Co(Me(3)tpa)(diox)]PF(6) (2), where diox = 3,5-di-tert-butyl-1,2-dioxolene; tpa = tris(2-pyridylmethyl)amine and Me(3)tpa its 6-methylated analogue. Complex (1) is present in solution as ls-Co(III)(catecholate) (1-CAT), while (2) as hs-Co(II)(semiquinonate) (2-SQ). DFT calculation of the harmonic frequencies for (1) and (2) allowed us to identify the vibrational markers of catecholate and semiquinonate redox isomers. Irradiation with 405 and 810 nm pulses (~35 fs) of (1-CAT) induces the formation of an intermediate excited species from which the ground state population is recovered with a time constant of 1.5 ± 0.3 ns. Comparing the 1 ns transient infrared spectrum with the experimental difference spectrum FTIR(2-SQ)-FTIR(1-CAT) and with the calculated difference spectrum IR(c)(1-SQ)-IR(c)(1-CAT) we are able to unequivocally identify the long lived species as the semiquinonate redox isomer of (1). On the other hand, no evidence of photoconversion is observed upon irradiation of (2) with 405 nm. Temporal evolution of transient spectra was analyzed with the combined approach consisting of singular values decomposition and global fitting (global analysis). After 405 and 810 nm excitation of (1-CAT), the semiquinonate excited species is formed on an ultrafast time scale (<200 fs) and cools down within the first 50 ps. Excitation of (2-SQ) with 405 nm wavelength produces a short lived excited state in which the semiquinonate nature of dioxolene is preserved and the ground state recovery is completed within 30 ps.

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Cross-phase modulation in visible-pump/mid-infrared-probe spectroscopy

Cited by 10 publications

References 7 publications

Ultrafast resonance energy transfer in the umbelliferone–alizarin bichromophore

Ultrafast resonance energy transfer in the umbelliferone–alizarin bichromophore

Carbon Monoxide Recombination Dynamics in Truncated Hemoglobins Studied with Visible-Pump MidIR-Probe Spectroscopy

Transient infrared spectroscopy: a new approach to investigate valence tautomerism

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