Introduction:  Designing the Molecular World

Abstract

The construction of highly complex organic molecules by the assembly of simple molecular "building blocks" is not at all a new concept in organic synthesis, as, for example, numerous Diels-Alder and other cycloadditions or condensation reactions show. What is new, however, is an immensely increased number of preparative methods for linking the building blocks on the one hand and an enormous variety of types and complexities of employable oligofunctional small molecules on the other. In particular, the numerous metal-mediated processes that have become routine in the synthetic laboratories around the world during the last two decades allow the connection of carbon atoms and heteroatoms of practically any type of hybridization. As far as the building blocks are concerned, not only do they span the wide spectrum from very simple units, such as acetylene, to DNA, a "molecular brick" once regarded as being intractable for molecular construction, but it has also become possible to combine fragments from completely different subdisciplines of organic chemistrysacetylenes and sugars, for example, or fullerenes and porphyrinssgiving rise to completely novel hybrid structures.It still remains a dream that anything can be accomplished, that any mental image of a molecule can be transformed into material reality, as a small list of so far unknown hydrocarbonssthemselves only a grain of sand in a mountain of (conceivable) structural complexitysshows: for example,

On the “Gluing” Effect of Lithium: The Lithium‐Driven Assembly of Circum‐Arranged, Edge‐Fused Cyclopentadienyl Lithium Compounds and Aza Analogues

“…) was obtained for dimer 1.1A C H T U N G T R E N N U N G [1,4,1]. Moreover, we have found that the discrete solvation of lithium, as in the case of 1.1 6e A C H T U N G T R E N N U N G [0, 3,3], does not break down the overall structure (optimization at the HF/6-31 + G* level, only).…”

“…On the other hand, the energy of association involved in the formation of three dimers ), is even less than that corresponding to the formation of 1.1.1.1.1 [1,3,3,3,3,2] pentamer (301.15 kcal mol À1 ) starting from five monomers, both measured at the B3LYP/6-31G* level (data not shown in Table 3). Altogether, these data suggest that columnar, nanometer long (the length of pentamers is about 1.9 nm), polymetallic super-sandwich compounds of either the ,4,(3) n ,1] type should be available from 1.…”

“…Likely, the ideal plan for accessing technologically valuable solid materials is a bottom-up approach [1] which starts with a simple molecule capable of self-assembly into a large supermolecule, [2] the final step being its conception as an organized solid material. [3] In M. Etters words: "organizing molecules into predictable arrays is the first step in a systematic approach to designing organic-solid state materials".…”

“…[22] While tracking down the dimerization of planar CCpLibenzene (trindenyl trilithium) 1 we recognized four possible assembly modes leading to dimers 1. ,3,2], and 1.1A C H T U N G T R E N N U N G [1,4,1]. [23] These dimers (Figure 2), as well as monomer 1, were found to be stationary points at the B3LYP/6-31 + G* level.…”

“…,5,2,1] were found to be also high energy species. [26] Analogously, pentamers 1.1.1.1.1 [1,3,3,3,3,2] and 1.1.1.1.1 [1,4,3,3,3,1] were calculated to be 37.81, and 34.65 kcal mol À1 (B3LYP/3-21G*) more stable than the isomeric 1.1. 1.1.1[0,3,3,3,3,3] as illustrated in Table 3 ( Figure 4).…”