Controlling Supramolecular Assembly Using Electronic Effects

Abstract

Through systematic structural studies using custom designed probe molecules, it has been shown that the balance between hydrogen-bonds in the context of supramolecular chemistry and crystal engineering can be understood and guided by a semiquantitative thermodynamic assessment that integrates theoretical and experimental views of solution-based molecular recognition events. Although pKa values can be used for ranking hydrogen-bond donors/acceptors within a family of compounds, they do not offer reliable information when comparing different functional groups. However, against a backdrop of a simple electrostatic interpretation of hydrogen bonds coupled with a focus on the primary non-covalent interactions, molecular electrostatic potential surfaces can be employed for guiding the synthesis of binary- and ternary co-crystals with the desired connectivity and dimensionality.

Polystyrene supramolecular networks based on DA-AD hydrogen bonds

“…These controllable properties were attributed to the strength of the dimers formed by hydrogen bonds. The hydrogen bonding strength has been quantified by 1 H NMR spectroscopy at different concentrations to obtain K calculated at 6.75 M −1 for MAAM and 16.75 M −1 for MAP. Furthermore, the stronger hydrogen bond interaction of P(St-co-MAP), compared to P(St-co-MAAM), was proved by applying Kwei equation to T g dependence against copolymer composition and by solubility tests.…”

“…AcAP CDCl 3 solution at 0.03 mol L −1 was also analyzed by 1 H NMR spectroscopy at different temperatures with the same spectrometer. Spectra were recorded with the same parameters mentioned above but at 300 and 315 K, respectively, in order to determine K.…”

“…In contrast to the covalent bonds, they have lower binding strength, [1] but endow materials with reversible interactions typically dependent on temperature, solvent, and pH. [2][3][4] Chemical moieties are able to form host-guest systems in dimers by single or multiple interactions distinguished by homodimers and heterodimers.…”

“…The dimers can be linked to the backbone or located at the end chains. [14] The total energy difference, ΔE HB , between the hydrogen-bonding system at equilibrium and the total energy of the free components [1,15,16] can reach 120 kJ M −1 with a single hydrogen bond, almost half the value of covalent bond strength such as σ carbon-carbon bond, close to 348 kJ M −1 . [17] Although hydrogen bonds are not the strongest non-covalent interactions, they are prominent in supramolecular chemistry due to their versatility and directionality.…”

“…[17] Although hydrogen bonds are not the strongest non-covalent interactions, they are prominent in supramolecular chemistry due to their versatility and directionality. The determination of association constants K is required to measure the reversible binding strength in supramolecular polymers (Equation (1)). [18,19] With heterodimer systems specifically, K is obtained by Rose-Drago model which establishes a relationship between δ and the host/guest mol ratio [18] (Equation (1)).…”