Solvophobically‐Driven Merocyanine Dye Assembly: Predominant Dipole‐Dipole Interactions Over Hydrogen‐Bonding

Abstract

Merocyanine dye assembly in nonpolar solvents is driven by electrostatic dipole‐dipole interactions, which make hierarchical structures of merocyanine less favorable, due to the compensation of its dipole moment in the discrete antiparallel dimer state. Herein, we describe the self‐assembly of a merocyanine dye (MC−OH) into higher aggregates in aqueous medium (with 10% dioxane) by synergistic effect of dipole‐dipole interactions and strong dispersion forces, which remains underexplored for its known molecular stabilization in polar solvents. Our results reveal that in the crystal packing, strong intermolecular hydrogen (H)‐bonding predominates over the dipole‐dipole interactions, which confines the dye into a head‐to‐head parallel π‐stacked assemblage. When intermolecular H‐bonding in water is curtailed, antiparallel dimers by dipolar interactions become predominant. Several of these antiparallel dimers laterally cluster through solvophobically‐induced π‐stacking and form stable nanodiscs, which exhibit efficient hydrophobic dye sequestering properties. At higher concentration, the nanodiscs are transformed into elongated nanotapes. The computational studies support the experimental findings and emphasize the competing nature of multiple noncovalent interactions in guiding the dye assembly under different conditions.

Tuning of the Supramolecular Helicity of Peptide-Based Gel Nanofibers

“…In addition, such a methodology has been notable to furnish spectral information of aggregates in well-agreement to experiments . Thus, this methodology is expected to provide reliable energetics to quantify the driving force concerning the helical inversion in the present work. − The steric encumbrance between the alkyl chains in stacked dimers should resist a proper self-assemblage of the chromophores. Hence, the adjacent monomeric units should rotate and reorganize to achieve the minimum energy conformation. , Thus, thermodynamics is believed to be the driving force in inducing chirality.…”

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives

“…28 However, in the absence of such conditions (such as in the solid state), the same dye showed hydrogen bond mediated stacking formation. 28 Contrary to this finding, it was noted that naphthalene monoimide (NMI) luminogens 26-28 (Chart 4) form stimuli-responsive luminescent assemblies in solid state, which is mainly mediated by dipole-dipole interactions (Fig. 6b).…”

“…Among the classical experimental techniques, NCIs in solids and solutions are characterized primarily through infrared (IR), nuclear magnetic resonance (NMR), Raman spectroscopic and crystallographic techniques. [25][26][27][28] For instance, IR spectroscopy is beneficial in providing information on the presence or absence of the electrostatic interactions such as hydrogen bonding. Further information (e.g., intra-, or intermolecular nature) can be obtained by 1D and 2D NMR techniques such as variable temperature (VT) NMR and deuterium exchange experiments.…”

Pathway Complexity in Supramolecular Copolymerization and Blocky Star Copolymers by a Hetero-Seeding Effect

“…The unsymmetrical structure of O-NMI and S-NMI introduces the possibility of both parallel and antiparallel stacking arrangements with different energy landscapes, which may compete with each other depending upon the overall strength of H-bonding in the two states and the stability acquired through dipolar interactions known for push–pull type chromophores, ,, which prefer antiparallel orientations to neutralize their dipole moments. To gain a better understanding of the molecular packing, DFT calculations at the ωB97 x -D3/6-31G­(d,p)/CPCM­(decane) level of theory were performed with both O-NMI and S-NMI (see the Supporting Information for computational details). To minimize the computational costs, the three decyloxy chains were replaced with three methoxy groups.…”