In chemistry, photoisomerization is a form of isomerization induced by photoexcitation.[2] Both reversible and irreversible photoisomerizations are known for photoswitchable compounds. The term "photoisomerization" usually, however, refers to a reversible process.
Applicationsedit
Photoisomerization of the compound retinal in the eye allows for vision.
Another class of device that uses the photoisomerization process is as an additive in liquid crystals to change their linear and nonlinear properties.[6] Due to the photoisomerization is possible to induce a molecular reorientation in the liquid crystal bulk, which is used in holography,[7] as spatial filter[8] or optical switching.[9]
In the presence of a catalyst, norbornadiene converts to quadricyclane via ~300nm UV radiation . When converted back to norbornadiene, quadryicyclane’s ring strain energy is liberated in the form of heat (ΔH = −89 kJ/mol). This reaction has been proposed to store solar energy (photoswitchs).[12]
Photoisomerization behavior can be roughly categorized into several classes. Two major classes are trans–cis (or E–Z) conversion, and open-closed ring transition. Examples of the former include stilbene and azobenzene. This type of compounds has a double bond, and rotation or inversion around the double bond affords isomerization between the two states.[13] Examples of the latter include fulgide and diarylethene. This type of compounds undergoes bond cleavage and bond creation upon irradiation with particular wavelengths of light. Still another class is the di-π-methane rearrangement.
Coordination chemistryedit
Many complexes are often photosensitive and many of these complexes undergo photoisomerization.[14] One case is the conversion of the colorless cis-bis(triphenylphosphine)platinum chloride to the yellow trans isomer.
^ abNatansohn, Almeria; Rochon, Paul (2002). "Photoinduced Motions in Azo-Containing Polymers". Chemical Reviews. 102 (11): 4139–4176. doi:10.1021/cr970155y. PMID 12428986.
^"Photoisomerization". IUPAC Compendium of Chemical Terminology. 2009. doi:10.1351/goldbook.P04622. ISBN 978-0-9678550-9-7.
^Mammana, A.; et al. (2011). "A Chiroptical Photoswitchable DNA Complex" (PDF). Journal of Physical Chemistry B. 115 (40): 11581–11587. doi:10.1021/jp205893y. hdl:11370/cca715c8-861f-4500-943f-028c95e8e55e. PMID 21879715. S2CID 33375716.
^Mokdad, A; Belof, J; Yi, S; Shuler, S; McLaughlin, M; Space, B; Larsen, R (2008). "Photophysical Studies of the Trans to Cis Isomerization of the Push−Pull Molecule: 1-(Pyridin-4-yl)-2-(N-methylpyrrol-2-yl)ethene (mepepy)". Journal of Physical Chemistry B. 112 (36): 8310–8315. Bibcode:2008JPCA..112.8310M. doi:10.1021/jp803268r. PMID 18700732.
^Janossy, I.; Szabados, L. (1 October 1998). "Optical reorientation of nematic liquid crystals in the presence of photoisomerization". Physical Review E. 58 (4): 4598. Bibcode:1998PhRvE..58.4598J. doi:10.1103/PhysRevE.58.4598. S2CID 26508261.
^Chen, Alan G; Brady, David J (1992). "Real-time holography in azo-dye-doped liquid crystals". Optics Letters. 17 (6): 441–3. Bibcode:1992OptL...17..441C. doi:10.1364/OL.17.000441. PMID 19784354. S2CID 20923350.
^Maly, Kenneth E; Wand, Michael D (2002). "Bistable ferroelectric liquid crystal photoswitch triggered by a dithienylethene dopant". Journal of the American Chemical Society. 124 (27): 7898–7899. doi:10.1364/OPEX.13.002358. PMID 19495125.
^Waldeck, David H. (1991). "Photoisomerization dynamics of stilbenes". Chemical Reviews. 91 (3): 415–436. doi:10.1021/cr00003a007.
^Dubonosov, Alexander D.; Bren, Vladimir A.; Chernoivanov, V. A. (2002). "Norbornadiene–quadricyclane as an abiotic system for the storage of solar energy". Russian Chemical Reviews. 71 (11): 917–927. Bibcode:2002RuCRv..71..917D. doi:10.1070/RC2002v071n11ABEH000745. S2CID 250890545.
^Kazem-Rostami, Masoud; Akhmedov, Novruz G.; Faramarzi, Sadegh (2019). "Spectroscopic and computational studies of the photoisomerization". Journal of Molecular Structure. 1178: 538–543. Bibcode:2019JMoSt1178..538K. doi:10.1016/j.molstruc.2018.10.071. S2CID 105312344.
^D. M. Roundhill (1994). Photochemistry and Photophysics of Metal Complexes. Springer. ISBN 978-1-4899-1495-8.