Parameterization of the torsional potential for calix[4]arene‐substituted poly(thiophene)s

Abstract

Three different strategies have been followed to develop the torsional force-field parameters of the inter-ring dihedral angles for calix[4]arene-substituted poly(thiophene)s, a family of highly sensitive ion receptors. These procedures, which are based on the rotational profiles calculated using quantum mechanical methods, differ in the complexity of the model compounds and the processing applied to the quantum mechanical energies before the fitting. The performance of the three sets of developed parameters, which are essentially compatible with the General Amber Force Field, has been evaluated by computing the potential of mean forces for the inter-ring rotation of 2,2'-bithiophene, and its substituted analog bearing a calix[4]arene group in different environments. Finally, the ability of the new sets of torsional parameters to describe a calix[4]arene-substituted poly(thiophene) in tetrahydrofuran solution has been checked using Molecular Dynamics simulations. Specifically, the molecular shape, the polymer conformation, and the effects of the Na(+) ions trapped in the cavity of the receptor have been examined. Although the potential derived from unsubstituted 2,2'-bithiophene is able to reproduce the experimental free energies of the minima, the overall results indicate that the parameters derived from the analog bearing a calix[4]arene group provide the best description of the systems under study. This should be attributed to the strong constraints found in complex substituted poly(thiophene)s, which require parameterization strategies able to capture all the interactions and phenomena involved in their inter-ring rotations.

Redox‐Responsive Covalent Organic Nanosheets from Viologens and Calix[4]arene for Iodine and Toxic Dye Capture

“…To further investigate the formation of the nanosheets, we performed MD simulations of COP1 ++ and COP2 ++ . Although monomeric and dimeric calixarene derivatives have been studied extensively using both quantum mechanical and classical molecular mechanics approaches, MD simulations of covalent calixarene‐based polymeric systems are still rare . Initial structures of the repeating units of COP1 ++ and COP2 ++ were constructed in primitive unit cells such that parallel layers of sheets were stacked on top of each other in the first set (Figure S12, Supporting Information).…”

Polythiophene-g-poly(ethylene glycol) graft copolymers for electroactive scaffolds

“…41 The parameters for the S-C-C-S torsion were extracted from a recent study in which force-eld parameters compatible with AMBER were developed by computing the potential of mean forces for the inter-ring rotation of different 2,2 0 -bithiophene derivatives. 42 Atomic charges were adjusted using the Restrained ElectroStatic Potential (RESP) strategy. 43 The van der Waals parameters of the spherical particles used to construct the surface [R ¼ 2.35 Å and 3 ¼ 0.90 kcal mol À1 ] were extrapolated from previous studies devoted to investigate the structure of organic systems tethered to rigid surfaces.…”

Calix[4]arene-Based Porous Organic Nanosheets

“…The lamellar features of the material were further confirmed by atomic force microscopy (AFM), which demonstrates a sheet-like morphology of 3.52 nm thickness and a rather broad lateral size distribution of 1–5 μm (Figure e,f). To further investigate nanosheet formation, we conducted computational modeling by applying and extending methods that have been used to study monomeric and dimeric calixarene derivatives. − DFT was used to identify the minimum energy structures of the calixarene-containing nanosheet by varying the unit cell parameters (see the Supporting Information for details). In the lowest energy structure, the calixarenes adopt a 1,2-alternate conformation that results in a two-dimensional pattern that has a rhomboid unit cell.…”