Transcript スライド 1
Katsuki Okuno Miyasaka Laboratory 1 Introduction Definition Example of Photochromic Molecules History Recent research Photochromism in single crystal Shape change of photochromic crystal Fluorescence switching by photochromic reaction Research with Lasers Observation of reaction dynamics Control chemical reaction by laser What I am going to study Future Prospects in Photochromism 2 Original Definition of Photochromism Phenomenon that color of material is changed by light irradiation. photo(light) + chrom(color) + ism(phenomenon) Similar phenomena ・Thermochromism color is changed by changing temperature ・Electrochromism color is changed by gain or loss of electron ・Solvatochromism color is changed by changing polarity of solvent 3 Definition of Molecular Photochromism Reversible isomerization between two isomers having different absorption spectra, which is induced in at least one direction by light irradiation. hn A hn’ or D B A and B have an equal molecular weight but have different structures. Example (diarylethene in solution) UV light Vis. light 4 Azobenzene Fulgide Spiropyran / Spirooxazine Diarylethene HABI (Hexaarylbiimidazole) T-type P-type 5 Application Quick property change •Absoption spectra •Refractive indices •Dielectric constants •Redox potential •Structure Application Rewritable paper Photo-memories Photo-switches Photo-driven actuator etc. Basic Time origin of reaction is easily determined time-resolved detection of precise reaction profiles 6 1867 First discovery of photochromism (M. Fritsche, Comp. Rend. 1867, 69, 1035.) 1905 Discovery of fulgide (H. Stobbe, Ber. 1905, 38, 3673.) 1937 Discovery of azobenzene (G. S. Hartley, Nature 1937, 140, 281.) 1952 Discovery of spiropyran (E. Fischer, Y. Hirshberg, J. Chem. Soc. 1952, 4522.) 1960 Discovery of HABI (Japan) (T. Hayashi, K. Maeda, Bull. Chem. Soc. Jpn. 1960, 33, 565.) 1967 Discovery of spirooxazine (Japan) (Fuji Film) 1988 Discovery of diarylethene (Japan) (M. Irie, M. Mohri, J. Org. Chem. 1988, 53, 803.) 7 UV light Vis. light fluorescent non-fluorescent Digital switching T. Fukaminato, M. Irie et al., Nature, 420 (2002) 759. T. Fukaminato, M. Irie et al., J. AM. CHEM. SOC. 126, (2004) 14843. → Single-molecular photo-memory/switch 8 Photochromic reaction occurs in crystalline phase UV Vis UV Vis AFM image of surface of diarylethene single crystal S. Kobatake and M. Irie, Science, 291 (2001) 1769. 9 Changing of crystalline shape is induced by photochromic reaction UV Vis Energy of light is directly converted into mechanical energy “Photo-driven mesoscopic actuator” Open-form S. Kobatake, M. Irie et al, Nature, 446 (2007) 778. Closed-form 10 photo detector pump pulse Dt monitor pulse sample pump pulse t=0 monitor pulse Time observe spectra at various delay time Dt 11 Excited state(S1) have limited life time Isomerization occurs in competition with ・radiative transition (fluorescence and phosphorescence) hn ・nonradiative transition (internal conversion and intersystem crossing) S1 isomerization S0 Measurement of reaction dynamics Revealing reaction mechanism Determination of rate constant Revealing the factors determining reaction rate → Rational principle for development of advanced molecule 12 in PMMA matrices 1 mm2 PS 532 nm irradiation 4.2 mJ / mm2 2 shots 5 min. 3.75 mJ / mm2 10 min. 7.5 mJ / mm2 20 min. 15 mJ / mm2 5,10,20 min. Steady-state Xe lamp At 532 nm 0.05 mW 13 Cycloreversion reaction is more than 2500 times enchanced by 15-ps 532-nm laser pulse excitation. When used as optical memory Data writing → UV light Data reading → weak visible light Data deleting → strong visible light Cycloreversion reaction yield : 10-5 14 visible two-photon absorption process UV one-photon absorption process Large reaction yield Sn 532 nm × S1 532 nm Open form Closed form 266 nm Open form J. Am. Chem. Soc., 123 (2001) 753, J. Am. Chem. Soc, 126 (2004) 14764 J. Phys. Chem. C, 111 (2007) 2730, J. Phys. Org. Chem., 20 (2007) 953, J. Phys. Chem. C, 112 (2008) 11150. Phys. Chem. Chem. Phys, 11 (2009) 2640, New. J. Chem. 33 (2009) 1409, Photochem. Photobiol. Sci., 9 (2010) 172. 15 Sn ? ? Property of higher excited state Role of excess vibrational energy photo detector S1 monitor pulse pump pulse S0 repump/dump pulse 16 Sn S1 0.04 S0 DAbsorbance Probed at 710 nm 0.03 0.02 0.01 Graund state 0.00 0.0 0.5 1.0 1.5 2.0 Time / ps 17 1. 2. 3. 4. Application of molecular photochromic reaction into control of bulk and surface properties. ex. hydrophilicity/hydrophobility More effective and rapid response photo-actuator; direct change of photo-energy into mechanical force New photochromic molecular system with nonlinear and threshold function. Revealing the reaction dynamics; intramolecular vibration, nonradiative transition and symmetry of electronic state 18