Planar assemblies

The ions in a beam that has been dispersed in space according to their various m/z values can be collected simultaneously by a planar assembly of small electron multipliers. All ions within a specified mass range are detected at the same time, giving the array detector an advantage for analysis of very small quantities of any one substance or where ions are produced intermittently during short time intervals. 

The tetrametallic planar assembly will be subdivided into square-planar and triangulated-rhomboidal geometries. 

After the mass analyser has dispersed the ions in space or in time according to their various m/z values, they may be collected by a detector. In modern mass spectrometry, a detector consists of a planar assembly of small electron multipliers, called an array in one case (spatial separation) and a microchaimel plate in the other (temporal separation). These collectors can either detect the arrival of all ions sequentially at a point (a point ion collector) or detect the arrival of all ions simultaneously (an array or multipoint collector). 

The number of sites per unimer (S) and their distributions control the functionalitjj (F) of the unimers and the dimensionality of the assembly. Complementarity of shapes and interaction, localized at the north and south contacting surfaces of bifunctional unimers, results in the formation of unidimensional (linear) assemblies (Fig. la F = 2, 5 = 2). Functionalities greater than 2 result in the formation of more complex geometries (Fig. Ib). Helical supramolecular chains are expected when two additional sites are located on the same side (i.e., NE and SE) of the unimer. Planar assemblies are expected when four sites are distributed along the circumference of a disk. 

The fourth dassiiication scheme has been used by Cifetri, differentiating SPs on the basis of the physical stmcture assumed through polymerization. Example classes indude linear chains, helical chains, columnar assemblies, micdlar assemblies, planar assemblies, composite assemblies, and three-dimensional assemblies. Ciferri induded a breakdown and description of the linear and hdical chain assemblies as being controlled by different growth mechanisms however, these types are ultimatdy dassified by resulting stmcture. 

Figure 3 A dicarboxylic acid is threaded through a tetracationic cyclophane macrocycle to form a repeating unit which is connected to other units by a double H-bond. The evolution toward a pseudopolyrotaxane and a planar assembly stabilized by n-n stacking interaction is supported by X-ray data for the undiluted system. (From Ref. 12. Copyright 1997 Am. Chem. Soc.)...

Figure 15 Schematic assemblies of (A) triangular units with monofunctional and bifunctional binding sites (B) cylindrical, spherical, disklike units forming linear sequences (C) spherical units with an equatorial distribution of binding sites forming a planar assembly (D) asymmetrical site distribution generating helical assembhes. (From Ref. 2.)...

R. Blumenfeld and S. R Edwards. Granular entropy Explicit calculations for planar assemblies. Physical Review Letters, 90(11), March 21, 2003. 

For oxoanions of the second period, (e.g. carbonate, COf ) three-coordination is the norm as it allows for the formation of a planar assembly with extensive n bonding. 

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