Networks self-penetrating

An interesting series of structures based on the rutile net illustrates the relationship between interpenetration and self-penetration. The compounds are constructed using octahedral metal ions and the trigonal ligands tcm [tricyanomethanide, C(CN) ] and dca [dicyanamide, N(CN)2 ]. It is important to note that dca is a smaller ligand than tcm. Thus, while the compounds M(tcm)2 have two interpenetrating rutile-related networks,the... 

Fig. 4 The self-penetrating network of M(dca)(tcm), with the penetration of a rod through a ring highlighted. ...

Another self-penetrating network is the (12,3) net, of which two examples were recently reported. If interpenetrating networks can be related to catenanes and rotaxanes, then self-penetrating networks can be considered to be polymeric equivalents of molecular knots. 

Figure 4.38 (a) A two-fold three-dimensional interpenetrating network of Co(dca)2(pyrazine) and (b) part of a self-penetrating three-dimensional network Co(dca)(tcm). 

Yu. S. Lipatov, R. A. Veselovskii, and Yu. K. Znachkov, Characteristics of the Properties of Adhesives Based on Self-Penetrating Polymer Networks, Dokl. Akad. Nauk SSSR 238(1), 174 (1978). PU/Polyester IPN adhesives. Bonding strength. 

Another fascinating discrete supramolecular architecture that has attracted considerable attention is the molecular knot. The polymeric version of a knot is a self-penetrating network indeed, this is sometimes referred to as polyknotting. ... 

A reasonably simple way to derive a self-penetrating network is to cross-link 2D (4,4) sheets with bridges that lie significantly inclined to the normals of the sheets. The catenated shortest circuits then inevitably include two of the intersheet links in each circuit. For example, in the structiu e of [Cd(CN)2(pyrazine)], corrugation of the (4,4) sheets of Cd(CN)2 leads to the bridging pyrazine ligands connecting the sheets at... 

Ni(tpt)(NOp2-solv (b) a self-penetrating (8,4) network. Catenated rings are highlighted in green and pink in each net... 

With controllable strength of the self- and hetero-associated hydrogen, a molecular level penetrated semi-interpenetrating polymer networks (semi-IPNs) of ST-VPDMS with poly(N-vinylpyrrolidone) (PVPr) were prepared by condensation of the self-associated silanols.13... 

It has been mentioned already that there are different levels of sophistication with regard to the involvement of computer applications in GLP studies and test facilities. These levels may range from the complex problems involved in the GLP compliant management of computer networks and of laboratory information management systems (LIMS) to the question of whether a simple instrument controlled by a built-in, pre-programmed chip should be treated in the same, extensive way with regard to software validation . It is certainly self-evident, as these two examples demonstrate, that not all types of IT applications have to be considered as equal with regard to GLP compliance it may indeed be impossible to do so. As it is commonplace nowadays that the silicon chip penetrates the operation of practically all kinds of work, the elucidation of its involvement in the operations of test facilities becomes an essential part of the implementation of GLP. 

Figure 10.5 illustrates the chemical structure of a plane parallel PDR by giving the relative abundances of C+, C and CO as a function of the penetration depth into the model cloud [11]. We assumed a kinetic equilibrium and determined the relative abundances from a chemical network consisting of 38 different species formed and destroyed in 434 reactions. The PDR is illuminated from the left by the mean interstellar radiation field and extends from the predominantly atomic surface region to the point where almost all carbon is bound into CO. One of the difficulties in calculating the chemical and thermal structure of a PDR arises from the effect of self-shielding. Molecules already formed absorb UV photons which are able to dissociate the respective molecule. In other words they cast a shadow into the cloud which enhances the further formation of the respective molecule. This effects becomes especially important for the formation of key molecules like O2, H2 and CO. Our current research addresses the question under which physical conditions an instability due to shadowing effects could occur. Another difficulty concerns the effects of small-scale fluctuations of the UV radiation field on the chemical network. 

An example of a three-dimensional penetrating network is the solvated [(ZnCl2)3(35)2] 56 [139], The triazine molecules are part of threefold connecting knots (Fig. 7-17). The zinc atoms have a nearly tetrahedral coordination geometry with two N atoms of 35 and two chlorine ligands. A distorted network is obtained. The self-assembly of CUSO4 in water and l,3-bis(4-pyridyl)propane in ethanol results in 57 which presents a three-dimensional architecture sustained by two different types of coordination polymer one-dimensional ribbons of rings and two-dimensional layers (Fig. 7-18) [138]. 

Carlucci, L. Ciani. G. Macchi, P. Proserpio, D.M. An unprecedented triply intei penetrated chiral network of square-planar metal centres from the self-assembly of copper(II) nitrate and L2-bis(4-pyridyl)ethyne. Chem. Commun. 1998. (17). 1837-1838. 

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