Title:
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Understanding the origins of strong multivalent cooperativity
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This thesis presents a combined experimental and computational evaluation of chelate cooperativity. The principal result from the thesis is that host-guest design cannot be limited to chemical intuition. By using a combination of theoretical approaches, we determined a procedure for a qualitative prediction of chelate cooperativity. Chapter 1 briefly reviews the concepts of supramolecular chemistry and cooperativity, its different types and presents experimental methods used to quantify cooperativity. In Chapter 2, host-guest are designed to probe different influences on chelate cooperativity. The synthesis of the studied host-guest library is presented. In Chapter 3 we show whether cooperativity can be predicted based on simple molecular structures. Therefore, we determined binding constants for the selected systems and compared the chelate cooperativity strength qualitative and quantitative. Our conclusion is that even systems only exhibiting chelate cooperativity are too complex to base cooperativity prediction exclusively on molecular structure. In Chapter 4, the cooperativity study of the presented host-guest systems is extended and contributions of entropy and enthalpy on chelate cooperativity are separated. The results have shown that the intramolecular process is driven by favourable entropy, but additional factors such as solvation lead to entropy-enthalpy compensation. In Chapter 5, computational results on the prediction of effective molarities and cooperativity strength are presented. A benchmark compares different methods on the evaluation of supramolecular systems. The results have shown that theoretical methods allow a qualitative prediction of chelate cooperativity strength. A comparison of different solvation models revealed a procedure to reproduce experimental results.
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