Self sorting, kinetic

Scheme 4.9 Kinetic and thennodynamic self-sorting based on guests with two binding epitopes.

Scheme 4.9 Kinetic versus thermodynamic self-sorting using two-faced guests.

In this context the supramolecular crystalline [15-22] or hybrid materials [23-35] can be prepared and constitutionally self-sorted by using an irreversible kinetic process like crystallization or sol-gel polymerization. The self-selection is based on constitutional internal interactions of library components, resulting in the dynamic amplification of self-optimized architectures, during the phase change process. With all this in mind, the second part will be devoted to sol-gel resolution of dynamic molecular supramolecular libraries, emphasizing recent developments, especially as pursued in our laboratory. 

Fig. 4.10 a The acceptor (Aj) and donor OI3) molecules having spacer length mismatch b gradual transition of the kinetically controlled chaige transfer gel to self-sorted gel with time. Reproduced from Ref. [60] by permission of John Wiley Sons Ltd... 

Self-sorting under kinetic control has also been reported [75]. However, due to the dynamic nature of the noncovalent interactions used in polymer self-assembly, the products of self-sorting usually cannot be isolated when they form in solution. 

Interestingly, the addition of 4 equiv. of dppp c s-protected Pd(II) complex to a 1 1 mixture of tetrakis(4-pyridylethynyl) and tetrakis(cyanophenyl) cavitand derivatives, 45 and 46, resulted in the kinetically controlled formation of the two homocontainers 47 and 48 (narcissistic self-sorting). However, heating the mixture at 50 °C produced the diagnostic proton signals of the heterocontainer 50. In a different experiment, a 1 1 mixture of pre-assembled homocontainers 47 and 48 was also shown to produce the heterocontainer 50. In this latter case, the thermodynamic equilibrium was reached by heating the mixture at 50 °C for 2 h and produced a [50]/[47] ratio of 1.0 [68]. The heterocontainer 50 was also assembled... 

The importance of kinetic studies of this sort for synthetic investigations is self-evident. 

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