Solvent Controls Synthesis and Properties of Supramolecular Structures
摘要:
A template effect by solvent was found in the synthesis of self-assembled capsules. Use of aromatic solvents such as benzene, toluene, and p-xylene leads predominantly to the formation of the C-shaped molecules 3 and 6, which form hydrogen-bonded dimeric capsules. This is the medium in which the solvent-occupied dimeric capsule enjoys the greatest stability, and the best solvated surfaces with properly filled niches are formed preferentially. The dimerization constant (K-D) value and a Delta G(0) value of >14.0 kcal mol(-1) for the capsules 16 (3.3) were estimated for the first time in guest-exchange experiments. When solvents not suitable for dimerization (CHCl3 and CH2Cl2) or those solvents that compete for hydrogen bonds (DMSO and THF) were employed, only statistical yields of the stereoisomers (C-, S-, and W-shaped) were observed. Experimental evidence is presented that the solvent molecules control the covalent bond formation through molecular recognition within the monomeric tetrahedral intermediate. It is proposed that solvation effects can be treated as a subset of molecular recognition events.
Solvent Controls Synthesis and Properties of Supramolecular Structures
摘要:
A template effect by solvent was found in the synthesis of self-assembled capsules. Use of aromatic solvents such as benzene, toluene, and p-xylene leads predominantly to the formation of the C-shaped molecules 3 and 6, which form hydrogen-bonded dimeric capsules. This is the medium in which the solvent-occupied dimeric capsule enjoys the greatest stability, and the best solvated surfaces with properly filled niches are formed preferentially. The dimerization constant (K-D) value and a Delta G(0) value of >14.0 kcal mol(-1) for the capsules 16 (3.3) were estimated for the first time in guest-exchange experiments. When solvents not suitable for dimerization (CHCl3 and CH2Cl2) or those solvents that compete for hydrogen bonds (DMSO and THF) were employed, only statistical yields of the stereoisomers (C-, S-, and W-shaped) were observed. Experimental evidence is presented that the solvent molecules control the covalent bond formation through molecular recognition within the monomeric tetrahedral intermediate. It is proposed that solvation effects can be treated as a subset of molecular recognition events.