Bond data, storage

Due to its improved efficiency and its economical use of data storage capacities the modified HMBC experiment is a valuable alternative for all those structural problems for which the knowledge of long-range and one-bond connectivities and values of the corresponding coupling constants is essential and for which only small sample amounts are available. 

Multiple cyclic proton transfers occur in hydrogen bonded arrays of heterocyclic units [8.220, 8.221] or inside rings such as porphyrins [8.222]. Macrocyclic polyamines present various protonation patterns [3.13a] that could be of interest as information units. Data storage in a molecular memory by hole burning makes... 

Fig. 2. A molecular data storage scheme based on an aromatic molecule (naphthalene) bonded to four gold electrodes by sulfur atoms and polyacetylene wires [37). For the surface an insulator has to be chosen to prevent cross-talk between the electrodes. The variables X, Y and Z could either be chemical substituents or, alternatively, connections to further electrodes. Some parts of the molecule, electrodes and variables are drawn in bright colors, which is meant to indicate an active state during a particular read-out. The darker parts are considered to be inactive.

Very recently, the azobenzene norbornene derivative XI (Scheme 2) was successfully prepared and polymerized with initiator 5 and 9, and it showed a nematic mesophase. The polymer was photo-switchable due to photo cisltrans-isomerization of the N=N double bond [65]. This is the first step towards ROMP-derived materials that may be used for optical data storage. 

Structure and data storage is shown on the right. A structure table contains the structures, their internal identifiers, and their external identifiers, if any. The structures are stored in a compact binary representation that includes the connection table, the coordinates, the ring information, and any stereochemical, valence, isomer, isotope, or bond information. Certain types of structure-specific information such as polymer or component designations are stored here, whereas other types of structure-specific information (atom- or bond-specific data, and more verbose text data) are stored in their own tables, referenced by the internal identifier, and the atom or bond numbers to which the data correspond. A formula table contains the molecular formula and various atom and atom-type indexes to enhance formula searching and sorting. 

Molecular graphics visualization software performs an elaborate connect-the-dots process to make the wonderful pictures of protein structure we see in textbooks of biomolecular structure, like the structure for insulin (SINS Isaccs and Agarwa, 1978) shown in Figure 5.1. The connections used are, of course, the chemical bonds between all the atoms. In current use, three-dimensional molecular structure database records employ two different minimalist approaches regarding the storage of bond data. 

Yi and coworkers have also studied a similar hydrogen bonded complex 52, formed by V-shaped acid containing nitril azobenzene groups in each of the arms around l,3,5-triazine-2,4-diamine core [71]. Such complex forms a hquid crystalline phase and reveals response to both stimuli of hght irradiation and electric field. The induced molecular orientation can be held after the removal of the stimuli. This kind of self-assembled complex may have potential applications in imaging and data storage. 

A field of great interest at the moment is the synthesis of overcrowded tetrasubstituted alkenes which can act as switches and molecular motors [19]. They are also an interesting class of compounds for the development of optical data storage. Tietze and coworkers [Ic] have prepared a wide variety of these types of compounds, such as 16, by domino Mizoroki-Heck processes in high yield and complete control of the configuration of the double bond formed using aryl bromides 14a-f as substrates, which contain a triple bond and an allylsilane moiety. The best results were obtained using the Herrmann-Beller catalyst (15) [20]. It can be assumed that the palladium species 18a-c are intermediates,... 

Adding fluorescent molecules to photopolymers also provides a method for optical data storage. In such a system, the fluorescent molecules bond to the polymer matrix and become more concentrated in the polymerized regions causing the required refractive index pattern (194). 

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