Solid-State Photoreactions in Two-Component Crystals

Abstract

This paper overviews the photochemical reactions of two-component crystals and solid mixtures. It covers mixed crystals, hydrogenbonded cocrystals, donor-acceptor crystals, inclusion crystals, crystalline organic salts (including Lewis acid complexes), and solid mixtures. Solid-state sensitization and quenching and solid-state asymmetric syntheses are also mentioned. Emphasis is placed on the synthetic points. Neither details of reaction mechanisms nor crystal structures are described in most cases. Yoshikatsu Ito SYNTHESIS 2 Biographical Sketch Yoshikatsu Ito was born near Hiroshima City, Japan in 1945. He graduated from Hiroshima University in 1967. After working at a chemical company (Kyoto City) and Ph. D. studies (Kyoto University), he joined the faculty of Hiroshima University and then moved to Columbia University for postdoctoral studies under the supervision of Professor N. J. Turro. He joined the faculty of Kyoto University in 1977 and is still at the same place. His research interests mainly reside in the application of solid state and aqueous media to organic photochemistry. Scheme 72 Scheme 73 Scheme 74 Downloaded by: University of Illinois. Copyrighted material. Scheme 81 Scheme 82 Scheme 84 Scheme 83 Downloaded by: University of Illinois. Copyrighted material.

Crystal structures and photoreactivity of trans- and cis-valerophenone diperoxides

“…Then ca. 10 mg of each sample was placed in a special quartz vessel [25,26] and was irradiated for 0.5 h under the stream of Ar gas at 0°C. After the irradiation, the sample was dissolved in MeCN, followed by the addition of benzophenone as the standard to determine the amounts of 2 and 3, and then the solution was analyzed with HPLC.…”

“…The decomposition of the diperoxides 1 stopped at low conversions and the HPLC retention times of 1 differed very much from those of 2 and 3 (retention times with 90/10 MeOH-H 2 O: trans-1 9.4, cis-1 8.2, 2 2.6, 3 3.0 min; retention times with 65/35 MeOH-H 2 O: trans-1 [ 60, cis-1 [ 60, 2 10.8, 3 18.9 min). Furthermore, irradiation of all parts of the solid sample equally was difficult with our set-up [25,26], although the powder was mixed with a spatula from time to time. Therefore, determinations of the diperoxide recovery were subjected to large experimental errors as seen from Fig.…”

“…2] and [4 ? 4] photocyclodimerization by varying the crystal structures through formation of two-component crystals [25,26]. As a modifier component, hydrogen-bonding intermolecular linkers (e.g., gauche 1,2-diamine, phthalic acid, and oxalic acid) [39][40][41][42][43][44], small molecules (e.g., NH 3 and divalent metal) [26,45], and relatively small and planar molecules (e.g., imidazole, trans,trans-muconic acid, and acetylenedicarboxylic acid) [45,46] were employed.…”

“…In the course of these studies, two-component crystals were frequently found to be more loosely packed than one-component crystals and hence two-component crystals appeared to undergo decreased topochemical restriction to molecular motions. For example, in addition to static disorder, dynamic disorder caused by a pedal-like dynamic conformational change and volume-demanding reactions such as trans-cis photoisomerization of olefin occurred relatively easily in cocrystals [25,26,43,44].…”

A facile, stereoselective [2 + 2] photoreaction mediated by cucurbit[8]uril

“…For example, by forming host-guest complexes, cyclodextrins mediate photoreaction of aromatic guests such as anthracene, 5 coumarin 6 and stilbene 7,8 derivatives in solution as well as in the solid state. 8,9 However, few studies reported large rate acceleration and high stereo-and/or regioselectivity in [2 + 2] photoreactions mediated by cyclodextrins in solution.…”