Photo solid-state reactions

The development of the principles of solid-state reactions of substituted cinnamic acids was pioneered by Gerhard M. J. Schmidt. The trans-SLcid was found to be polymorphic, and three different crystal forms (designated a, and 7) were identified by him. The finding that the nature of the cyclobutane derivatives formed by the solid-state photochemical reaction on crystals of frans-cinnamic acid depend on which polymorph is irradiated was of great interest. The products of the photo-... 

Corona poling technique in the wire to plane geometry as well as parallel electrode poling techniques have been used to pole these classes of polymers in film form. Poling is carried out prior to crosslinking to align the NLO units and possibly poise the photoreactive groups for photo-induced solid state reaction. 

In this review article, after a description of the historical background of the present subject, some general features of reactions in amorphous polymer solids are summarized and then specific features of photo-physical processes, photoisomerization, photodimerization, chain scission, and crosslinking reactions are discussed separately. Typical theoretical treatments of solid-state reactions are reviewed in relation to the interpretation of experimental results. 

Keywords 2+2 cycloaddition Coordination polymers (CPs) Crystal engineering Cyclobutane derivatives Ladder structures MOFs Photo-reactivity Solid-state reactions Structural transformation... 

The low solubility of fullerene (Ceo) in common organic solvents such as THE, MeCN and DCM interferes with its functionalization, which is a key step for its synthetic applications. Solid state photochemistry is a powerful strategy for overcoming this difficulty. Thus a 1 1 mixture of Cgo and 9-methylanthra-cene (Equation 4.10, R = Me) exposed to a high-pressure mercury lamp gives the adduct 72 (R = Me) with 68% conversion [51]. No 9-methylanthracene dimers were detected. Anthracene does not react with Ceo under these conditions this has been correlated to its ionization potential which is lower than that of the 9-methyl derivative. This suggests that the Diels-Alder reaction proceeds via photo-induced electron transfer from 9-methylanthracene to the triplet excited state of Ceo-... 

However, the biochemical significance of the latter studies is challenged by the fact that the transformation of transient purine and pyrimidine radicals into diamagnetic decomposition products is oxygen-independent in the solid state. Therefore, it is necessary to study the chemistry of one-electron nucleobase intermediates in aerated aqueous solutions in order to investigate the role of oxygen in the course of reactions that give rise to oxidation products within DNA and model compounds. In this respect, type I photo-... 

M. x 108M 1s 1 at 25°C, but may be appreciably lower in the solid state. In comparison k2 for oxygen competition for the alkyl radical is 2 x 109M-1s 1. Thus for air-saturated PPH ([02] 8 x 10-1,M)reaction7 will be protection against xenon irradiation was improved as compared to the parent piperidine by about 25, but the nitroxide itself was reduced to the 1 x 10 M level within the first lOOh and persisted at this level until brittle failure (7,) In contrast the parent amine is completely destroyed in the first lOOh of xenon exposure. 

In fact the extremely rapid reaction of NOH with hydroperoxides combined with the ready oxidation of hydroxylamines to nitroxides during storage even in the solid state makes unlikely the detection of >N0H from hindered amines in photo-oxidizing polymer. 

In the solid state, small N0 species can diffuse through the amorphous zones, and clearly become associated with the oxidized domains in these amorphous zones. Thus the local N0 concentration adjacent to an -00H site (before photo-cleavage) is anticipated to be much greater than expected from the overallI NO1 concentration, and so increase the effectiveness of the scavenging process (reaction 7) as compared to the propagation step (reaction 2). 

The photo-induced single and double Diels-Alder reactions between [60]fullerene and 9-methylanthracene (212) which gave 213 and 214 were performed in the solid state by Mikami and colleagues (equation 60)141. The Diels-Alder reaction was considered to proceed following a photo-induced electron transfer from 9-methylanthracene to fullerene. The higher ionization potential of anthracene should explain its inreactivity toward the cycloaddition reaction with [60]fullerene. 

Unlike Zn(II)Pc and Ru(II)Pc, Co(II)Pc and Fe(II)Pc are known to undergo oxidation at the metal prior to ring oxidation (14 15). Electrochemical studies of CoPc have, however, shown that ring oxidation does occur before metal oxidation if weakly-coordinating ligands are employed (16). The products of the chemical oxidation of CoPc and FePc in solution, have been only poorly characterized in the peist (17 18). Lever and coworkers (9j33) have reported the oxidation of CoPc and FePc in the solid state and characterized the reaction as metal oxidation, M(II)Pc(-2) M(III)Pc(-2), followed by phthalocyemine n ring oxidation, M(III)Pc(-2) M(III)Pc(-1). However, no electro- or photo-chemical... 

ElZ isomerizations are usually not expected in the solid state. They have been widely studied in solutions or in liquids. This includes thermal, catalytic, and photolytic processes and ElZ isomerization was also observed in competition with biphotonic excimer laser photodecompositions [47]. Most of the ElZ isomerizations in the solid state have been photo chemically observed [48], but mostly not as uniform quantitative reactions. If these isomerizations cannot be performed under selective conditions of irradiation (an exception is 83/84) [49], the only chance to have these reactions uniform with 100% yield is a very efficient isomerization (according to the phase rebuilding mechanism) that leads to an isomeric product with heavily interlocked crystal lattice. Under such circumstances side reactions of the substrate and photoconversions of the product are prohibited (including the back reaction, of course). Four favorable cases... 

Eliminations belong to one of the most diverse reaction types [76] and numerous solvent-free pyrolyses (sometimes quantitative melt reactions) provided useful syntheses [58,81-87]. However, quantitative solid-state eliminations are rare (examples are found in the halogenations of 110,112, and 114 (Scheme 12)). If an elimination reaction cannot be performed purely thermally or photo-chemically, usually a catalyst or other auxiliary has to be added and it is then no longer waste-free. 

It may be suspected that the genuinely topotactic (as secured by the molecular precision of the AFM [18]) photodimerization of 2-benzyl-5-benzyli-denecyclopentanone [118] might be a good candidate for a quantitative preparative photo dimerization to give the head-to-tail anti-[2+2] dimer. Early quantitative solid-state [2-1-2] photodimerizations (most of the published mechanistic interpretations of which can no longer be accepted) are listed in [110]. These deal with the anti dimerization of acenaphthylene-1,2-dicarboxylic anhydride, the head-to-head syn dimerization of acenaphthylene-1-carboxylic acid, the syn dimerization of 5,6-dichloroacenaphthylene, and the thermally reversible head-to-tail anti dimerization of seven ( )-2,6-di-f-butyl-4-(2-aryl-ethenyl)pyrylium-trifluoromethanesulfonates. All of these reactions proceed fully specific. On the other hand, quantitative photoconversions of a 1 1 mixed crystal of ethyl and propyl a-cyano-4-[2-(4-pyridyl)ethenyl]cinnamates gives mixtures of diesters with one (A>410 nm) or two cyclobutane rings (no cutoff filter). 

Table 10 Photo reaction of thioamides 24f-h in both solution and the solid-state...

The polymerization proceeds under photo- [49,50],X-ray [51], and y-ray [52] irradiation in the dark in vacuo, in air, or even in water or organic solvent as the dispersant (nonsolvent) for the crystals, similar to the solid-state polymerization of diacetylene compounds [ 12]. The process of topochemical polymerization of 1,3-diene monomers is also independent of the environment surrounding the crystals. Recently, the thermally induced topochemical polymerization of several monomers with a high decomposition and melting point was confirmed [53]. The polymer yield increases as the reaction temperature increases during the thermal polymerization. IR and NMR spectroscopies certified that the polymers obtained from the thermally induced polymerization in the dark have a stereoregular repeating structure identical to those of the photopolymers produced by UV or y-ray irradiation. 

Irradiation of 4-(but-3-enylidene)-2-phenyl-5(477)-oxazolone 733 leads to the [4 + 2] adduct 734 derived from 733 acting as both a diene and a dienophile in a solid-state photo Diels-Alder reaction (Scheme 7.226). °... 

Hochstrasser and Porter4 reported on Primary Processes in Photo-Oxidation. A short review was given on direct photooxygenation reactions in solution as well as in the solid state. Gas-phase reactions in the presence of oxygen were also discussed. 

A considerable amount of attention has also been paid to the photo-Fries rearrangement of polymer pendant groups. For example, the rearrangement of poly (phenyl acrylate) (10,11) in solution or in the solid-state, is usually incomplete and results in the formation of both the ortho and the para-hydroxyphenone rearranged products in amounts which vary with the conditions of the photolysis. A concurrent side-reaction, which we term the Fries degradation, also results in the liberation of small amounts of phenol (Scheme 2). Similar results have been obtained with poly (phenyl methacrylate) and other substituted aryl acrylates (4,9,12). 

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