Cooperative Supramolecular Polymerization of Triphenylamine bis‐Urea Macrocycles

Abstract

Herein, we probe the hydrogen bond-driven selfassembly of a triphenylamine (TPA) bis-urea macrocycle in the presence and absence of guests. Comprised of methylene urea-bridged TPAs with exterior tridodecyloxy benzene solubilizing groups, the macrocycle exhibits concentration-dependent aggregate formation in THF and H 2 O/THF mixtures as characterized by 1 H NMR and DOSY experiments. Its assembly processes were further probed by temperaturedependent UV/Vis and fluorescence spectroscopy. Upon heating, UV/Vis spectra exhibit a hypsochromic shift in the λ max , while fluorescence spectra show an increase in emission intensity. Conversely, the protected macrocycle that lacks hydrogen bond donors demonstrates no significant change. Thermodynamic analysis indicates a cooperative self-assembly pathway with distinct nucleation and elongation regimes. The morphology and structure of the aggregate were elucidated by dynamic light scattering, atomic force microscopy, scanning and transmission electron microscopy. Variable temperature emission spectra were utilized to monitor the impact of guests, such as diphenylacetylene, that can be bound in the columnar channels. The findings suggest that the elongation of assemblies is influenced by the presence of these guests. In comparison, diphenyl sulfoxide, likely functioning as a chain stopper, limited the assembly size. These studies suggest that judicious selection of (co)monomers may modulate the function and utility of these supramolecular systems.

Supramolecular Gelation of Triphenylamine Bis-Urea Macrocycles in Toluene

“…Earlier assembly reports in THF showed fiber formation but no gelation . In comparison to THF, toluene is less polar with a polarity value of 2.4 vs 4 for THF .…”

“…TPA macrocycle 1 was synthesized through a Suzuki coupling reaction between the triazinanone-protected macrocycle 3 and the boronate ester of tridodecycloxybenzene 4 (Scheme S1). 24 The synthesis of compound 4 involved three steps, starting with the readily available 5-bromo-1,2,3-trimethoxybenzene. Following the coupling between 3 and 4, the protective group was removed under acidic conditions.…”

“…31 Previous work found a decrease in the aggregate size of 1 in the H 2 O/THF solution upon the addition of diphenyl sulfoxide (DPS). 24 Therefore, dimethyl sulfoxide (DMSO) and DPS were investigated as chain stoppers, and their effects on the gel storage and loss modulus were tested.…”

“…Macrocycle 1 assembled cooperatively in H 2 O/THF solutions to give 1D fibers. 24 This intriguing fibrous structure of 1 motivated further investigation of its potential for gelation in other solvents. Such gels may retain homogeneous binding channels, which could offer novel functional properties.…”

“…Recently, the two exterior bromides were replaced with dodecycloxybenzenes affording 1 which retains a similar size internal cavity. Macrocycle 1 assembled cooperatively in H 2 O/THF solutions to give 1D fibers …”