Two-step anti-cooperative self-assembly process into defined π-stacked dye oligomers: insights into aggregation-induced enhanced emission

Abstract

Aggregation-induced emission enhancement (AIEE) phenomena received great popularity during the last decade but in most cases insights into the packing structure – fluorescence properties remained scarce. Here, an almost non-fluorescent...

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

“…Spherical aggregates were also reported earlier for other merocyanine dyes in organic solvents. [10] The height profile from atomic force microscopy (AFM) analysis (Figure 4b, S8) showed much lower particle thickness (~2-8 nm) with respect to the diameter that showed a broad particle size distribution in the range of ~50-120 nm. Much larger particle size with respect to its height indicates the occurrence of flat disc-like morphology.…”

“…[1] Owing to the compensation of the polarization effect in the antiparallel dimer forms, higher ordered structures of merocyanines are less favourable and have been reported to be anti-cooperative in some cases. [10] Combination of the dipolar interactions of merocyanines with other secondary forces like H-bonding [3f,11] and hydrophobic interactions [12,13a] represents a powerful method for promoting their favourable long-range ordered assembly. Other approaches for extended dipolar interactions of merocyanine dyes include specific structural designs using tweezer-based bismerocyanines, [13] foldamers [14] or polymeric templates.…”

“…In order to neutralize their dipole moments, merocyanine dyes tend to assemble by directional electrostatic dipole‐dipole interactions into discrete centrosymmetric antiparallel dimers by opposite orientation of their molecular dipoles in less polar solvents with very high binding constants (∼10 6 M −1 ), [8,9] unlike other hydrophobic aromatic analogues whose π‐stacking is dominated by weak dispersion forces [1] . Owing to the compensation of the polarization effect in the antiparallel dimer forms, higher ordered structures of merocyanines are less favourable and have been reported to be anti‐cooperative in some cases [10] . Combination of the dipolar interactions of merocyanines with other secondary forces like H‐bonding [3f,11] and hydrophobic interactions [12,13a] represents a powerful method for promoting their favourable long‐range ordered assembly.…”

Anti‐kooperative Selbstorganisation mit aufrechterhaltener Emission reguliert durch konformationelle und sterische Effekte

“…Hierbei muss beachtet werden, dass die extrem kleine Größe der Aggregate aufgrund der Faltung zwischen Spitze und Probe mit dem AFM nicht genau bestimmt werden kann, [54] was zu einer artifiziellen Verbreiterung führt [55] . Dennoch liegen die beobachteten Längenverteilungen im typischen Bereich für kurze Oligomere [22] . Außerdem weisen diese kleinen Aggregate eine einheitliche Höhe von 1.1±0.3 nm auf, was gut mit der Bildung von 1D‐Stapeln von 1 übereinstimmt, die parallel zum HOPG‐Substrat angeordnet sind, um die Wechselwirkungen mit den Alkoxyketten zu maximieren (siehe Schema in Abbildung 5a).…”

Crystallization‐Driven Controlled Two‐Dimensional (2D) Assemblies from Chromophore‐Appended Poly(L‐lactide)s: Highly Efficient Energy Transfer on a 2D Surface

“…Herein, we describe CDSA of different chromophore‐appended PLLA homopolymers (Scheme 1) to access well‐defined luminescent diamond‐shaped 2D platelets, surface‐decorated with self‐assembled π‐scaffolds like merocyanine (MC), naphthalene monoimide (NMI), pyrene (PY) or benzene (Bn). The choice of a suitable push–pull type dipolar MC‐dye was made based on the propensity of these class of molecules to readily self‐assemble into discrete antiparallel dimers [13a, b] or extended stacks [13c–e] via directional dipole–dipole interactions, which have been previously used to prepare supramolecular architectures from small molecules, [13] or macromolecules [14]…”