Topochemical solid-state

Polydiacetylenes are obtained as single crystals by topochemical solid-state polymerization of the monomer single crystal. These compounds have received considerable attention because of their one-dimensionally -conjugated structure. Their unique --electron structures, and therefore superior third-order nonlinear optical properties, have been extensively investigated. 

Fang G, Javier M-R, Zhigang P, Colan EH, Kenneth DMH (2008) Direct structural understanding of a topochemical solid state photopolymerization reaction. J Phys Chem C 112 19793-19796... 

Figure 2 Topochemical solid-state synthesis of bis-adduct 9 and templated synthesis of tetrakis-adduct 11 in solution.

As a suitable reaction we selected 2n + 2n) photocycloaddition as demonstrated by Schmidt, disubstituted ethylenes, appropriately oriented in the crystal and with the double bonds at a distance 4 A, form on u.v. irradiation cyclobutane dimers with a stereochemistry that directly reflects the symmetry relating the monomers in the mother phase (topochemical dimerization). Subsequently, Hasegawa and Naka-nishi have demonstrated that, when the double bonds are appropriately oriented and spaced, symmetrical disubstituted / -distyryl derivatives undergo, by the same mechanism, topochemical solid-state photopolymerization. 

Tashiro, K., Kamae, T., Kobayashi, M., Matsumoto, A., Yokoi, K. and Aoki, S. (1999) Structural change in the topochemical solid-state polymerization process of diethyl ds.cis-muconate crystal. 1. Investigation of polymerization process by means of X-ray diffraction, infrared/ raman spectra, and DSC. Macromolecules, 32, 2449-2454. 

Organic compounds with delocalized jr-electron systems, e,g., jr-conjugated polymers, are considered to be candidates for third-order nonlinear optical materials. Among them, polydiacetylenes (PDAs) are an important class of conjugated polymers that has attracted investigators from many different fields (7,2). PDAs, which can be obtained as single crystals by topochemical solid-state polymerization (5), have been extensively studied since 1976 (4). PDAs show large third-order nonlinear optical susceptibilities (5) and ultrafast optical... 

Figure 15.3 Topochemical solid-state polymerization of diacetylenes (1,4-addition). Partillel diacetylene molecules (A) reacting to form the trans, trans polymer, which can be represented by the alternate monomeric structures (B) and (C)...

These characteristics can be derived from a polymerization of crystalline monomers controlled topochemically. Topotactic reaction geno-ally involve a strong correspondence between the lattices of the monomer crystal and the resulting polymer crystal. Hence, the topochemical solid state reaction occurs when sufficiently intense thermal mobility of molecules takes place in the lattice, and the distance between active centers for the polymerization in the neighboring molecules should not exceed 3.7 A for C — O interactions All monomers mentioned above show quite close C — O interactions. 

If we can effectively use the chirality of the molecules expressed by spontaneous crystallization, asymmetric synthesis using chiral crystals, which has been restricted to the topochemical solid-state photoreaction, becomes a general synthetic method playing the part of organic synthesis. ) In this review, a general method of chiral crystallization and a new advanced asymmetric synthesis using the chiral crystals in a non-topochemical process will be described. 

The first reported and one of the best examples of the use of Raman spectroscopy to follow drformation in polymers is the case of substituted polydiacetylene single crystals [8-12]. The macroscopic polymer crystals are produced by the solid-state polymerization of substituted diacetylene single crystal monomers. The reaction is a topochemical solid-state polymerization [13], and the oystals produced have a high degree of perfection [14]. 

Biradha K, Santra R (2013) Crystal engineering of topochemical solid state reactions. Chem Soc Rev 42(3) 950-967... 

Knowing these requirements the problem then becomes one of engineering a suitable crystal, i.e. of selecting a monomer which will tend to crystallize in a structure which meets these requirements. In order to describe logically the steps leading to this selection we shall first make some remarks on topochemical solid-state polymerization in general and discuss (2+2)-solid-state-photopolymerization in particular. We also make some comments on chiral crystals. 

Controlled preparation of thin films of P(DiAc)s can be obtained by topochemical (solid state) polymerization of thin films of monomer previously deposited by evaporation under high vacuum, followed by UV or gamma irradiation [569] such thin films possess high order and alignment. Variation of the substrate crystallinity yields thin films or crystals of varying crystallinity [569]. Innovative methods, such as application of pressure on a mobile monomer phase between two optical plates... 

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