Solvent‐Dependent Truxene‐Based Nanostructures

Abstract

Three truxene derivatives functionalized with alkyl chains, either attached directly or distanced by linking phenyl or ethynyl groups, self-assemble in solution and induce the gelation of different solvents in spite of not being endowed with groups able to establish strong directional interactions. A (1)H NMR study points to face-to-face alternating π-stacked motifs at the origin of nucleation. Solvents play an important role in modulating the aggregation of these derivatives giving rise to fibrous or spherical superstructures. Analysis of the influence of different solvents on the morphology of the aggregates provides a better understanding of the various stages of the hierarchical self-assembly. The way in which alkyl chains are attached to the central core also strongly affects the self-assembling properties and gelation ability of this series. Phenyl spacers present the highest association constants in solution and give rise to gelation in a broader range of solvents. This behavior has been rationalized by means of (1)H NMR spectroscopy, X-ray powder diffraction, SEM, and photophysical measurements. Interestingly, it was found that these compounds in the gel state exhibit unusual emission properties most likely arising from the formation of excimers, which evidences that π-π interactions also occur in the excited state.

Tunable emission in dye-doped truxene-based organogels through RET

“…It has been previously shown that the aggregation of this compound is highly dependent on the polarity of the environment. 18 Comparison of the SEM images of the xerogels obtained with and without RhB (see Fig. S4, ESI †) clearly shows how the addition of the dye decreases the entanglement of the fibers confirming a disrupting effect on the aggregation exerted by the dopant.…”

“…Truxene-based organogels were fabricated according to ref. 18 in quartz cuvettes (see Experimental). In an initial stage the emission properties of the organogel were studied (see Fig.…”

“…The presence of the two bands points to the coexistence of both species, contrary to observations in solution where only the monomer is present. 18 Though both bands have similar intensity, the fraction of excimer species is much larger than that of the monomer as the quantum yield (QY) of the former is expected to be much lower than the latter in this kind of system. 19 PL decay measurements were also performed at wavelengths close to the band center for each species, showing a multiexponential behavior of the decay curves.…”

Tunable emission in dye-doped truxene-based organogels through RET

“…It has been previously shown that the aggregation of this compound is highly dependent on the polarity of the environment. 18 Comparison of the SEM images of the xerogels obtained with and without RhB (see Fig. S4, ESI †) clearly shows how the addition of the dye decreases the entanglement of the fibers confirming a disrupting effect on the aggregation exerted by the dopant.…”

“…Truxene-based organogels were fabricated according to ref. 18 in quartz cuvettes (see Experimental). In an initial stage the emission properties of the organogel were studied (see Fig.…”

“…The presence of the two bands points to the coexistence of both species, contrary to observations in solution where only the monomer is present. 18 Though both bands have similar intensity, the fraction of excimer species is much larger than that of the monomer as the quantum yield (QY) of the former is expected to be much lower than the latter in this kind of system. 19 PL decay measurements were also performed at wavelengths close to the band center for each species, showing a multiexponential behavior of the decay curves.…”

Effect of the Linkage Position on the Conjugation Length of Truxene-Based Porous Polymers: Implications for Their Sensing Performance of Nitroaromatics

“…Curiously, the fluorescence spectra of homopolymers Tx3-CMP and Tx2-CMP show a broad structureless band in addition to the main band that can be ascribed to some degree of aggregation of the truxene units, which suggest that the presence of flexible aryl spacers in PhTx2-CMP and PhTx3-CMP prevents chromophore aggregation. Note that truxene derivatives have a strong tendency to self-assemble both in solution and in the condensed phase, which usually has a strong influence on their optical properties. − …”

High‐Mobility Self‐Assembling Truxenone‐Based n‐Type Organic Semiconductors

“…This behavior is in contrastw ith that found for analogueso f1 and 2,w hich also self-assemble strongly in solution, but shielding effects are only observed for distinct protons ignals in the variable-concentration 1 HNMR spectra, and suggestsa na lternate arrangement in which each molecule is rotated by 608 with respect to the next molecular unit. [14] The tendency of these mol-Scheme1.Chemical structures of derivatives based on truxene (1), triindole 2,a nd truxenone (3).…”

Tunable emission in dye-doped truxene-based organogels through RET

“…It has been previously shown that the aggregation of this compound is highly dependent on the polarity of the environment. 18 Comparison of the SEM images of the xerogels obtained with and without RhB (see Fig. S4, ESI †) clearly shows how the addition of the dye decreases the entanglement of the fibers confirming a disrupting effect on the aggregation exerted by the dopant.…”

“…Truxene-based organogels were fabricated according to ref. 18 in quartz cuvettes (see Experimental). In an initial stage the emission properties of the organogel were studied (see Fig.…”

“…The presence of the two bands points to the coexistence of both species, contrary to observations in solution where only the monomer is present. 18 Though both bands have similar intensity, the fraction of excimer species is much larger than that of the monomer as the quantum yield (QY) of the former is expected to be much lower than the latter in this kind of system. 19 PL decay measurements were also performed at wavelengths close to the band center for each species, showing a multiexponential behavior of the decay curves.…”

Effect of the Linkage Position on the Conjugation Length of Truxene-Based Porous Polymers: Implications for Their Sensing Performance of Nitroaromatics

“…Curiously, the fluorescence spectra of homopolymers Tx3-CMP and Tx2-CMP show a broad structureless band in addition to the main band that can be ascribed to some degree of aggregation of the truxene units, which suggest that the presence of flexible aryl spacers in PhTx2-CMP and PhTx3-CMP prevents chromophore aggregation. Note that truxene derivatives have a strong tendency to self-assemble both in solution and in the condensed phase, which usually has a strong influence on their optical properties. − …”

High‐Mobility Self‐Assembling Truxenone‐Based n‐Type Organic Semiconductors

“…This behavior is in contrastw ith that found for analogueso f1 and 2,w hich also self-assemble strongly in solution, but shielding effects are only observed for distinct protons ignals in the variable-concentration 1 HNMR spectra, and suggestsa na lternate arrangement in which each molecule is rotated by 608 with respect to the next molecular unit. [14] The tendency of these mol-Scheme1.Chemical structures of derivatives based on truxene (1), triindole 2,a nd truxenone (3).…”

Tunable emission in dye-doped truxene-based organogels through RET

“…It has been previously shown that the aggregation of this compound is highly dependent on the polarity of the environment. 18 Comparison of the SEM images of the xerogels obtained with and without RhB (see Fig. S4, ESI †) clearly shows how the addition of the dye decreases the entanglement of the fibers confirming a disrupting effect on the aggregation exerted by the dopant.…”

“…Truxene-based organogels were fabricated according to ref. 18 in quartz cuvettes (see Experimental). In an initial stage the emission properties of the organogel were studied (see Fig.…”

“…The presence of the two bands points to the coexistence of both species, contrary to observations in solution where only the monomer is present. 18 Though both bands have similar intensity, the fraction of excimer species is much larger than that of the monomer as the quantum yield (QY) of the former is expected to be much lower than the latter in this kind of system. 19 PL decay measurements were also performed at wavelengths close to the band center for each species, showing a multiexponential behavior of the decay curves.…”

Effect of the Linkage Position on the Conjugation Length of Truxene-Based Porous Polymers: Implications for Their Sensing Performance of Nitroaromatics

“…Curiously, the fluorescence spectra of homopolymers Tx3-CMP and Tx2-CMP show a broad structureless band in addition to the main band that can be ascribed to some degree of aggregation of the truxene units, which suggest that the presence of flexible aryl spacers in PhTx2-CMP and PhTx3-CMP prevents chromophore aggregation. Note that truxene derivatives have a strong tendency to self-assemble both in solution and in the condensed phase, which usually has a strong influence on their optical properties. − …”

High‐Mobility Self‐Assembling Truxenone‐Based n‐Type Organic Semiconductors

“…This behavior is in contrastw ith that found for analogueso f1 and 2,w hich also self-assemble strongly in solution, but shielding effects are only observed for distinct protons ignals in the variable-concentration 1 HNMR spectra, and suggestsa na lternate arrangement in which each molecule is rotated by 608 with respect to the next molecular unit. [14] The tendency of these mol-Scheme1.Chemical structures of derivatives based on truxene (1), triindole 2,a nd truxenone (3).…”