Solid-State [2+2] Photodimerization and Photopolymerization of α,ω-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals

Abstract

[2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of α,ω-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.

Formation of interfacial network structure via photo-crosslinking in carbon fiber/epoxy composites

“…Among the physical and chemical crosslinking methods [14,15], photo-crosslinking exhibits considerable advantages, including mild reaction conditions, minimum byproduct formation, absence of potential toxic catalysts and initiators and easily controlled processing [16]. Consequently, in recent years there has been an increasing interest in utilizing photo-crosslinking as a means of biomaterial preparation in the field of medicinal and biomedical science [17][18][19][20][21]. However, to our knowledge, introduction of photosensitive materials into the interface between carbon fibers and resin matrix has never been reported.…”

Features of styryl dye crystal packings and their influence on [2 + 2] photocycloaddition reaction with single crystal retention

“…The PCA reaction is also challenging for creation of information optical recording systems. [3][4][5][6][7]9,[17][18][19][20]22,28,29,38,43,45,46 In studies of PCA reactions it is important to a priori achieve the formation of a "pre-organized" dimeric pair which shows the stacking interaction of the two molecules. 49 However, these reactions are thermal and they proceed in solution.…”

“…It is photochemically reversible, often regio-and stereoselective and it proceeds in both solution and in the solid phase. [3][4][5][6][7]13,16,18,19,22,[26][27][28]31,33,37,42,44,45 In this case the problem consists in directed design to create the required crystal packing. In order to achieve a solid phase PCA, pre-organization of the ethylene fragments is required in which these fragments are situated effectively parallel to one above another at a distance between the ethylene carbon atoms (d 1 ) not exceeding 4.2 Å (Schmidt's criterion 1 ).…”

Hybrid UV Curing System Using Methacrylates Having a Chalcone Moiety

“…Photodimerization of anthracene, cinnmate ester, chalcone, and coumarin proceed by irradiation of UV light [15,16]. Photodimerization conditions are tunable by selecting the dimerization moieties and/or irradiation conditions.…”