作者:Barry A. Blight、Christopher A. Hunter、David A. Leigh、Hamish McNab、Patrick I. T. Thomson
DOI:10.1038/nchem.987
日期:2011.3
Secondary electrostatic interactions between adjacent hydrogen bonds can have a significant effect on the stability of a supramolecular complex. In theory, the binding strength should be maximized if all the hydrogen-bond donors (D) are on one component and all the hydrogen-bond acceptors (A) are on the other. Here, we describe a readily accessible AAAAâDDDD quadruple hydrogen-bonding array that exhibits exceptionally strong binding for a small-molecule hydrogen-bonded complex in a range of different solvents (Ka > 3 Ã 1012 Mâ1 in CH2Cl2, 1.5 Ã 106 Mâ1 in CH3CN and 3.4 Ã 105 Mâ1 in 10% v/v DMSO/CHCl3). The association constant in CH2Cl2 corresponds to a binding free energy (ÎG) in excess of â71 kJ molâ1 (more than 20% of the thermodynamic stability of a carbonâcarbon covalent bond), which is remarkable for a supramolecular complex held together by just four intercomponent hydrogen bonds. The stability of multiply hydrogen-bonded complexes can be influenced significantly by secondary electrostatic interactions between the pairs of atoms in adjacent hydrogen bonds. Now, a quadruple hydrogen-bonding array in which all of the donors are located in one component and all of the acceptors in the other has been shown to form complexes that are exceptionally stable.