Role of Solvent and Dendritic Architecture on the Redox Core Encapsulation

Abstract

Dendrimers with redox cores can accept, donate, and/or store electrons and are used in nanoscale devices like artificial receptors, magnetic resonance imaging, sensors, light harvesting antennae, and electrical switches. However, the dendrimer molecular architectures can significantly alter the encapsulation of the redox core and charge transfer pathways, thereby changing the electron transfer rates. In this study, we used molecular dynamics simulations to investigate the role of solvent and peripheral groups on molecular structure and core encapsulation of iron–sulfur G2-benzyl ether dendrimers in polar and nonpolar solvent. We found that the dendrimer branches collapse in water and swell in chloroform. The presence of the long hydrophobic alkyl groups at the periphery deters the encapsulation of the core in water which may cause an increase in electron transfer rate. However, in chloroform, the dendrimer branches remain in the extended form, which leads to an increased radius of gyration. Our results suggest that peripheral alkyl chains in dendrimers cause steric hindrance, which prevents branches from back folding in chloroform solvent, but in water it reverses the trend. Overall, the presence of a hydrophobic interior and hydrophilic periphery in a dendrimer improves core encapsulation in water while hindering encapsulation in chloroform.

Unraveling the Conformational Determinants of Peptide Dendrimers Using Molecular Dynamics Simulations

“…The radius of gyration provides a measure of a dendrimer compactness, ,− while the rmsd quantifies the (dis)similarity among pairs of conformations. The rmsd to a “central” structure was computed using all dendrimer atoms, according to a combinatorial procedure accounting for quasi-symmetry described elsewhere .…”

A “breathing” dendritic molecule—conformational fluctuation induced by external stimuli

“…good or bad solvent), pH condition, and temperature. [39][40][41][42][43][44][45][46][47] The dendritic backbone usually adopts extended conformation in good solvents, although different degrees of backfolding of terminal branches exists owing to the conformation flexibility of molecular chains (entropydriven) and interaction between monomer units. In solvents of lower quality, dendritic branches tend to shrink and assume a compact structure, although such a solvent effect is relatively insensitive for dendrimers of lower generation.…”

Solvent Quality Controls Macromolecular Structural Dynamics of a Dendrimeric Hydrogenase Model

“…However, in a molecular dynamics study of a poly(aryl ether) dendrimer with an [FeS] 2 core, the dendritic groups were found to extend consistently in the explicit chloroform solvent, indicating that chloroform is a reasonably good solvent for poly(aryl ether) dendrons. 48 The solvation dynamics as sensed by the spectral diffusion of mode 2 of the dendrimer are significantly different from that found for mode 2 in [Fe(μ-S)(CO) 3 ] 2 . The most apparent difference is that the dendrimer invariably displays two pronounced time scales, and when an additional slow time scale is present in [Fe(μ-S)(CO) 3 ] 2 its contribution to the total inhomogeneity amplitude is typically small in comparison to the contribution of the fast time scale (see Table 2).…”

“…Of the solvents used here, toluene, DMF, and THF are known to be good solvents for poly­(aryl ether) dendrimers, whereas acetone is a “medium” quality solvent, and acetonitrile is classified as poor. , To the best of our knowledge, the solvent quality of chloroform for poly­(aryl ether) dendrimers has not been determined experimentally. However, in a molecular dynamics study of a poly­(aryl ether) dendrimer with an [FeS] 2 core, the dendritic groups were found to extend consistently in the explicit chloroform solvent, indicating that chloroform is a reasonably good solvent for poly­(aryl ether) dendrons …”