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Ga
Ga
[Ga 2 L 3 ] 6-
N = 5, y = 2, B = 6
inter = 4, intra = 2
[Eu 3 L 3 ] 9+
N = 6, y = 2, B = 6
inter = 5, intra = 1
[Tb 4 L 4 ] 12+
N = 8, y = 3, B = 12
inter = 7, intra = 5
Figure 3.5 Calculation of the number of intra and intermolecular connections in polynuclear
linear [24] and circular helicates [25] and tetrahedra [22].
3.3 Cooperativity in Self-Assembly
The self-organization of molecules into helicoidal structures is often accompanied by a
predominant formation of the desired products. Their thermodynamic stabilization is usu-
ally associated with the existence of cooperative interactions between components. In this
context, the typical cooperative self-assembly process borrowed from biology is the
“zipping up” of a double-helical structure upon the multiple binding interactions between
adenine and uracyl bases [2]. The beginning of the assembly process is dominated by
unfavourable entropy changes. However, further association of bases increases the
enthalpic term due to the induced preorganization, which translates into the overall
decrease of free energy. Although the cooperativity concept is well understood for
intermolecular binding, the recognition of cooperativity in metalloorganic systems
suffered from the confusion of inter- and intramolecular binding events. Ercolani
shed light on these phenomena [11,12,26] and introduced a reliable classification
of cooperativity interactions. If we consider intra- and intermolecular reactions as
fundamentally different binding processes, three types of cooperativity can be inde-
pendently accessed, which report to the following reaction pairs: intermolecular
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