Internal Probing of the Supramolecular Organization of Pyrene‐Based Organogelators

Abstract

A thorough study of the unexpected spectroscopic behavior of two new luminescent pyrene-urea-based organogelators is rationalized as a function of their aggregation state and provides a key method to probe the supramolecular organization of the material.

Triggering Gel Formation and Luminescence through Donor–Acceptor Interactions in a C3‐Symmetric Tris(pyrene) System

“…As previously discussed, one of the main interests of the pyrene unit lies on its emission properties which can be of monomer or excimer type, when Pyr⋅⋅⋅Pyr interactions take place in the excited state . Since the bipyridine units can also show emissive properties, we also prepared the reference tris(hexanoyl) derivative 5 (Scheme S1 in the Supporting Information), where pyrenebutanoyl substituents were replaced with hexanoyl units, in order to disclose the luminescence behaviour of the C 3 central platform.…”

“…In this respect, luminescent organogels occupy ap rominent place in view of their potential photonic applications. [7] The pyrene (Pyr) unit is known to possess interesting luminescent properties, [8] and was therefore introduced in the structure of organogelators, [9] including ab is(urea)s ystem, [10] which we very recently reported. Another interest of the pyrene platform lies on its electroactivity,a si tc an be readily oxidized into radicalc ation specieso rb ei nvolved in charge-transfer complexes.…”

“…As previously discussed, one of the main interests of the pyrene unit lies on itsemission properties which can be of monomer or excimer type, when Pyr···Pyr interactions take place in the excited state. [10] Sincet he bipyridineu nits can also show emissive properties, we also prepared the reference tris(hexanoyl) derivative 5 (Scheme S1 in the Supporting Information), where pyrenebutanoyl substituents were replaced with hexanoyl units, in order to disclose the luminescenceb ehaviouro f the C 3 central platform.T he synthetic strategy for 5 follows the same steps as those fort he pyrene derivative 1 starting from hexanoic acid chloride (Scheme S1). We then proceeded to absorption/emission/excitation investigations of 1 and 5 in C 2 H 2 Cl 4 at the reference concentrations of 5.24 10 À3 m,c orresponding to the CGC for the D-A 1·(TCNQ) 3 composite and of ap yrene solution at at hree-times higherc oncentration.…”

Organogel formation rationalized by Hansen solubility parameters: improved methodology

“…Indeed, these previously studied LMWGs, do not show G points uniformly distributed around S points, so that the AO method yields non-overlapping gelation and solubility spheres, with similar centre, radius and number of outliers as the originally proposed NO method. 9,10 Moreover, this AO method was also tested with success on all recent gelation data dealing with the HSP-based rationalization of gelation (see data in SI 16,18,[20][21][22][23][25][26][27][28][29] ). This indicates that using a methodology that allows but does not force the gelation sphere to share a common volume with the solubility sphere is the most suitable option for a general method for the determination of the gelation domain.…”

“…14 Some studies performed a simple qualitative description of the Hansen space (without determining a gelation sphere) or used a 1D or 2D projection of Hansen space (Teas Plot) to simplify the data treatment and representation. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] More interestingly, some studies proposed alternative procedures to determine a gelation domain from their specific experimental data. [30][31][32][33][34][35][36][37][38] While these modifications of the data treatment are certainly well suited to particular datasets, the natural question that arises is whether they are of general applicability.…”