Aggregation in the Solid State

For non-ionic polysoaps the situation is quite different. Whereas in the case of oligoethyleneoxide head groups thermotropic mesophases seem to be absent [87, 121-124, 126, 231, 403, 409], polysoaps with liposaccharide [230,240, 300] surfactant fragments or with lipopeptide [244, 400-402] ones frequently show lamellar mesophases (e.g. of smectic A type) and even nematic ones (Fig. 39). It should be emphasized that the thermotropic mesophases here are not the result of mesogenic groups being present, but are the consequence of the amphiphilic character of the polysoaps and the resulting microphase separation. 

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Several groups have studied introduction of phenylene ethynylene units into PPV backbones. The first material of this type, copolymer 163, was reported by Bunz and coworkers [193] (Chart 2.36). The material displayed blue luminescence in solution (A ax = 460 nm), but due to the polymer s rigid-rod structure, very strong aggregation in the solid state gave rise to... 

Red emission chomophores having a long wavelength emission band are usually polar, such as the above DCM series. The push-pull red emitters are normally prone to aggregation in the solid state owing to dipole dipole interactions or through intermolecular tt-tt stacking, especially when the molecules are flat as is the case for DCM. As a consequence, the push-pull red... 

The bicycles 40-42 can all be considered as TTFs and as such may have potential as component molecules for conducting organic solids. In this respect, heteroatom intermolecular S- -N and S- -S contacts are of special interest since they may increase the dimensionality of aggregation in the solid state, and, accordingly, much effort has been directed toward structure determination of this family of molecules <1993SM(68)1914, 1997SM(86)1871,... 

Bis-ferf-butylmagnesium (52) also forms dimeric aggregates in the solid state. Its molecular geometry comprises two f-Bu groups each bridging between two magnesium atoms [C(l)-Mg(l) 2.3044(9), C(l)-Mg(2) 2.2978(8), C(2)-Mg(l) 2.3057(8) and... 

In Group III a similar polymerization, leading to a reduction of the number of double bonds, is observed for all oxides. Whereas C02, with two double bonds, has no tendency to polymerization, Si02, as a monomeric molecule 0=Si=0, is only stable in the vapour at very high temperature and forms a three-dimensional aggregate in the solid state, each Si atom forming four single bonds with the O atoms. 

Of the transition metals, the nickel triad has been the most studied in terms of xanthate structures, especially nickel xanthates. Thus, binary xanthate structures are known for all elements with no less than 15 binary nickel xanthate structures known and these aggregate in the solid state in six distinct supramolecular architectures. There is also a rich diversity of adducts as well as mixed-ligand complexes, in particular for nickel. 

The first type of cruciform or cross-like material that we present is based on the so-called tetrahedral approach . The motivation for constructing it-conjugated materials using such tetrahedral cores (e.g. tetraarylmethane or -silane building blocks) stems from the perception that a bulky, sterically hindered architecture should be less prone to self-aggregation in the solid state and hence should lead to more efficient and morphologically stable photo- and electroluminescence. 

D. N. Chin, J. A. Zerkowski, J. C. MacDonald and G M. Whitesides, Strategies for the design and assembly of hydrogen-bonded aggregates in the solid state, in J. K. Whitesell (ed.), Organised Molecular Assemblies in the Solid State, Wiley, Chichester, 1999. 

A 1.27-1.68 mm/second) and solution, as are 72 in the solution state (230). The latter, however, aggregate in the solid state to produce a cis-R2SnS3 geometry about tin (A 1.93-2.62 mm/second) through a single intermolecular Sn-S interaction (230,231), in a proposed array similar to... 

Although it is usual to represent the alkali and alkaline-earth derivatives as MOC(= CRR )R, i.e. as they were mononuclear metal enolates (3), they are actually dinuclear, tetranuclear or hexanuclear aggregates in the solid state and in solution through bridging... 

A different aggregation behavior has been found for NHSns with sterically non-demanding or donor-functionalized A/, A/ -substituents. The NHSn 1 with A, A -(CH3)2-substituents dimerizes in the solid state via two strong inter-molecular Sn—N interactions (Figure 2.8.1). Only weakintra-molecular Sn O and no inter-molecular interactions were observed for the monomeric A,A -ether-functionalized stannylene 2 The stannylene with tz-propylamine substituents 3 exhibits both intra-molecular and inter-molecular Sn N interactions, thereby forming a bimolecular aggregate in the solid state. 

The first N-heterocyclic benzannulated plumbylenes 12 (N,Al -substituents CH2fBu) and 13 (N,N -substituents t Bu) have recently been described. Depending on the steric bulk of the A,A -substituents, they form two different bimolecular aggregates in the solid state (Figure 2.8.4). ... 

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