Abstract
In this paper, the photodynamics of three chromenes (2,2-spiro-adamantyl-7,8-benzo(2H)chromene, 2,2-diphenyl(2H)chromene and 2,2-diphenyl-5,6-benzo(2H)chromene) has been investigated by nano- and femtosecond time resolved techniques in hydrocarbon solutions at room temperature. Using pump–probe techniques, ultrafast steps of molecular dynamics characterizing the photoresponse of chromenes have been investigated: the breakage of the C–O bond was found to occur within a few hundred femtoseconds producing a short-lived transient that converts to the cisoid-cis open form in less than one picosecond and then to the metastable transoid-cis structure within a few picoseconds. The effect of different excitation wavelengths on the formation rate of the first shortest-lived transient of 5,6DPBC is in agreement with the model previously proposed to explain the wavelength dependence of the reaction and emission quantum yields in photostationary experiments. The results obtained in the nanosecond time domain show that the triplet marginally participates in the photoreaction for only one of the studied compounds (2,2-spiro-adamantyl-7,8-benzo(2H)chromene).
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J. C. Crano and R. J. Guglielmetti, Organic Photochromic and Thermochromic Compounds, Kluwer Academic–Plenum Publishers, New York, 1999, vol. 1–2.
H. Dürr and H. Bouas-Laurent, Photochromism: Molecules and Systems, Elsevier, Amsterdam, 1990.
R. S. Becker, E. Dolan and D. E. Balke, Vibronic effects in photochemistry. Competition between internal conversion and photochemistry, J. Chem. Phys., 1969, 50, 239–245.
R. S. Becker, A. P. Pelliccioli, A. Romani and G. Favaro, Vibronic quantum effects in fluorescence and photochemistry. Competition between vibrational relaxation and photochemistry and consequences on photochemical control, J. Am. Chem. Soc., 1999, 121, 2104–2109.
G. Favaro, A. Romani and R. S. Becker, Competition between vibrational relaxation and photochemistry: relevance of vibronic quantum effects, Photochem. Photobiol., 2001, 74, 378–384.
See e.g. N. Tamai and H. Miyasaka, Ultrafast dynamics of photochromic systems, Chem. Rev., 2000, 100, 1875–1890.
C. Lenoble and R. S. Becker, Photophysics, photochemistry and kinetics of photochromic 2H-pyrans and chromenes, J. Photochem., 1986, 33, 187–197.
J. Aubard, F. Maurel, G. Buntinx, O. Poizat, G. Levi, R. Guglielmetti and A. Samat, Femto/pico transient absorption spectroscopy of photochromic 3,3-diphenylnaphtho[2,1-b]pyran, Mol. Cryst. Liq. Cryst., 2000, 345, 215–220.
Y. Kodama, T. Nakabayashi, K. Segawa, E. Hattori, M. Sakuragi, N. Nishi and H. Sakuragi, Time-resolved absorption studies on the photochromic process of 2H-benzopyrans in the picosecond to submillisecond time domain, J. Phys. Chem. A, 2000, 104, 11478–11485.
T. Nakabayashi, N. Nishi and H. Sakuragi, Photochemistry of photochromic benzopyrans studied by time-resolved absorption spectroscopy, Sci. Progr., 2001, 84, 137–156.
J. Hobley, V. Malatesta, K. Hatanaka, S. Kajimoto, S. L. Williams and H. Fukumura, Picosecond and nanosecond photo-dynamics of a naphthopyran merocyanine, Phys. Chem. Chem. Phys., 2002, 4, 180–184.
G. Favaro, A. Romani and R. S. Becker, Photochromic behavior of 2,2-spiro-adamantylidene-2H-naphtho[1,2-b]pyran: a new thermoreversible and photoreversible photochromic system, Photochem. Photobiol., 2000, 72, 632–638.
G. Ottavi, G. Favaro and V. Malatesta, Spetrokinetic study of 2,2-diphenyl-5,6-benzo(2H)chromene: a thermoreversible and photoreversible photochromic system, J. Photochem. Photobiol. A: Chem., 1998, 115, 123–128.
S. L. Murov, I. Carmichael and G. L. Hug, Handbook of Photochemistry, Marcel Dekker Inc., New York, 1993.
C. V. Kumar, L. Qin and P. K. Das, Aromatic thioketone triplets and their quenching behaviour towards oxygen and di-t-butylnitroxy radical, J. Chem. Soc., Faraday Trans. 2, 1984, 80, 783–793.
R. S. Becker and J. Michl, Photochromism of synthetic and naturally occurring 2H-chromenes and 2H-pyrans, J. Am. Chem. Soc., 1966, 88, 5931–5933
J. Kolc and R. S. Becker, Proofs of structure of the coloured photoproducts of chromenes and spiropyrans, J. Phys. Chem., 1967, 71, 4045–4048.
R. S. Becker, G. Favaro, A. Romani, P. L. Gentili, and F. M. B. Dias, Mechanisms of vibrational relaxation and photochemistry: vibronic effects and pathways of radiationless processes involving excited states, vibrational levels and the ground state, J. Phys. Chem. A, submitted.
F. Ortica et al., unpublished results.
G. Favaro, U. Mazzucato, G. Ottavi and R. S. Becker, Kinetic analysis of the photochromic behavior of a naturally occurring chromene (lapachenole) under steady irradiation, Mol. Cryst. Liq. Cryst., 1997, 298, 137–144.
P. Celani, F. Bernardi, M. Olivucci and M. A. Robb, Conical intersection mechanism for photochemical ring opening in benzospiropyran compounds, J. Am. Chem. Soc., 1997, 119, 10815–10820.
P. L. Gentili, P. Migani, F. Negri, A. Romani, R. S. Becker, G. Favaro and M. Olivucci, The ring opening reaction of chromenes: a photochemical mode-dependent transformation, to be submitted.
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Gentili, P.L., Danilov, E., Ortica, F. et al. Dynamics of the excited states of chromenes studied by fast and ultrafast spectroscopies. Photochem Photobiol Sci 3, 886–891 (2004). https://doi.org/10.1039/b407541b
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DOI: https://doi.org/10.1039/b407541b