Aromatic diimides

Of the array of aromatic diimides available, PMIs (1), NDIs (2), and PDIs (3) (Figure 11.1) have been the most widely used, owing to the commercial availability of the starting dianhydride precursors. Although the PDIs are the most attractive in terms of their optical properties, they suffer tremendously from solubility problems-that is, aggregation. In particular, substituted NDIs form stable radical anion and dianion species [1-7], so from this aspect NDIs have become more attractive as supramolecular components. In recent years, NDIs have been shown to be a powerful tool in organic supramolecular chemistry to separate charges from photoexcited donor molecules. In this respect, NDIs are utilized as the electron acceptors [2-5]. 

Unsubstituted NDIs are seen as attractive chromophoric units because of their electronic complementarity to ubiquinones and their ease of formation from commercially available starting materials, forming symmetrical and asymmetric analogues relatively efficiently. Simple aromatic diimides undergo single reversible reduction processes either chemically or electrochemically to yield the corresponding radical anion in high yield (E1 = -1.10V vs. Fc/Fc+) (Fc ferrocene) [20a]. 

Aromatic diimides 71 and 72 derived from 9-epi-9-amino cinchona alkaloids and pyromellitic or 1,4,5,8-naphthalenetetracarboxylic anhydride have been designed by Gawronski and Kacprzak as novel chiral receptors. These triads are present at room temperature as equimolar mixture of syn and anti conformers, resulting from restricted rotation around the imide C—N bonds. These triads show high affinity toward carboxylic adds. The syn conformer binds preferentially 1,2-dicarboxylates in a 1 1 molecular ratio whereas the anti conformer is selective toward monocarbox-ylates forming a complex in a ratio 1 2 (triad acid). The response is sensitive and could be observed by either 1H NMR or by CD spectroscopy even when equimolar amounts of the adds are present in the solution. The competition experiments have shown a higher selectivity of triads toward 1,2-dicarboxylates [140],... 

It has been possible to prepare [2]catenanes by simply using neutral n-n stacking interactions. Sanders reported the use of crown ether macrocycle 40 containing two electron-rich naphthalene units, which could interact with 2 equivalents of an electron-poor aromatic diimide unit 41 that is appended with terminal acetylene groups to allow... 

Another approach is the reaction of diimides with divinyl monomers. Examples of this route, starting from divilylsulfone and pyromellitic, benzophenonetetracarboxylic and cyclopentanetetracarboxylic diimides have been reported (Scheme 22). The polymerizations are carried out in solution in the presence of inhibitors of radical polymerization, and the molecular weights achieved are not very high [129]. By a similar mechanism, polyimides have been prepared from diallylesters and cycloaliphatic [130] and aromatic diimides [131]. 

Aliphatic—aromatic poly(amide—imides) based on N,1S7-bis(carboxyalkyl)-benzophenone-3,3, 4,4 -tetracarboxyhc diimides have shown a 10% weight loss at 400°C (14). 

The customary method of preparing perylene pigments is by reaction of perylene tetracarboxylic dianhydride with primary aliphatic or aromatic amines in a high boiling solvent. The dianhydride itself is also used as a pigment. Di-methylperylimide may also be obtained by treating the diimide with methyl chloride or dimethyl sulfate. 

The reduction of polymers can be carried out by using a diimide, generated in situ. The precursor for diimide can be p-toluenesulfonyl hydrazide (TSH), the reaction temperature is between 110-160 °C and the solvents are high boiling aromatic compounds. Possible side-reactions are cis-trans isomerization of 1,4-dienes, attachment of hydrazide fragments to the polymer, degradation and cyclization of the polymer. 

Grignard reagents have reacted with diimide dioxides prepared from nitrosohydroxylamines and with toluenesulfonyl derivatives of nitroso-hydroxylamines to prepare unsymmetrical azoxy compounds, including aliphatic-aromatic types. 

The intercalation of polycyclic aromatic compounds into duplex DNA structures was used to develop nucleic acid-based electrochemical sensors.66 For example, the bis-ferrocene-tethered naphthalene diimide (16) was used as a redox-active intercalator to probe DNA hybridization.67 The thiolated probe was assembled on a Au electrode, and the formation of the duplex DNA with the complementary analyte nucleic acid was probed by the intercalation of (16) into the double-stranded nucleic acid structure and by following the voltammetric response of the ferrocene units (Fig. 12.17a). The method enabled the analysis of the target DNA with a sensitivity that corresponded to ca. 1 x 10-20mol. 

Diimide (N2H2, see p. 779) reduces aromatic aldehydes289 and ketones, but aliphatic carbonyl compounds react very poorly.290... 

The carbon-carbon double bond can be reduced by diimide prepared in solution in a number of ways.34 183,184 Oxidation of hydrazine with oxygen (air) or H202 in the presence of a catalytic amount of Cu(II) ion was the first method to generate and use diimide in hydrogenation.183-185 Acid-catalyzed decomposition of alkali azido-dicarboxylates,185,186 as well as thermal or base-catalyzed decomposition of aromatic sulfonyl hydrazides,183,184 are also useful methods for preparing the diimide reducing agent. 

N-Arylamidines act as 1,5-dinucleophiles towards sulfur dichloride, N-sulfinyltosylamide and bis(N-tosyl)sulfur diimide. The products are 1,2,4-benzothiadiazines (Scheme 14) (73ZOR2038, 68LA(715)223), and in the case of sulfur dichloride, chlorination of the aromatic ring also occurs. 1,2,4-Benzothiadiazines can also be prepared from N-arylamidines by reaction with sulfenyl chlorides or disulfides in the presence of NCS. Thus N-phenylben-zamidine and benzenesulfenyl chloride give the 1,2,4-benzothiadiazine (182) (78CC1049). 

Diels-Alder reactions are, of course, reversible, and the pathway followed for the reverse reaction (2,3 arrows) can sometimes be as telling as the pathway for the forward reaction. The direction in which any pericyclic reaction takes place is determined by thermodynamics, with cycloadditions, like the Diels-Alder reaction, usually taking place to form a ring because two n-bonds on the left are replaced by two Diels-Alder reaction can be made to take place in reverse when the products do not react with each other rapidly, as in the pyrolysis of cyclohexene 2.3 at 600°. It helps if either the diene or the dienophile has some special stabilization not present in the starting material, as in the formation of the aromatic ring in anthracene 2.15 in the synthesis of diimide 2.16 from the adduct 2,14, and in... 

Introduction of perfluorinated chains into the periphery of other disc-like or board-like Ji-conjugated aromatics [251, 252], such as coronene diimides [279], perylene diimides [280-282], naphthalene tetracarboxylic diimides [283-286],... 

Cyclopentanone (403) and cyclohexanone enamines react with symmetric and non-symmetric diimides of type Et02CN=NAr, ArCON=NCOAr and ArN=NCOAr (404) to give 1,3,4-oxadiazine derivatives 405 or open-chain Michael-type compounds 406 (equation 85)243-245. The formation of the former products seems to be favored by the presence of acceptor substituents on the aromatic ring of the diazene, and their stability is highly dependent on the ring size of the enamine employed. 

Both the thiophene 1-imide 123 and the 1,1-diimide 124 are thermally stable. X-Ray crystallography showed that the geometry of the former is similar to that of thiophene 1-oxide with a pyramidal configuration at the sulfur atom indicating loss of aromaticity. The C-C bond lengths also confirm this. 

In order to get more structurally pure polyPc a new way may start from multifunctional low molecular Pc. Co(II), Ni(II) and Cu(II) containing bis(dicarboxybenzoyl) Pc diimides were converted with various aromatic diamines in N-methylpyrrolidone to soluble polyamides which react to insoluble polyimides (9S) by heating to 473 K ). Melt and solution condensation of (12 b) and 3,3 -diaminobenzidine led to unsoluble polymers (99) with Pc-rings linked by benzimidazole units ). 

Carbodiimides comprise a group of compounds whose general formula is R—N=C—N—R, where R and R are aliphatic, such as diethylcarbo-diimide (QHs—N==C=N—C2H5), or aromatic, such as diphenylcarbo-diimide... 

---