Hydrogen‐Bond‐Directed Head‐to‐Tail Orientation of Dipolar Merocyanine Dyes: A Strategy for the Design of Electrooptical Materials

Abstract

Zwei Merocyanin‐Farbstoffe ordnen sich mithilfe mehrerer Wasserstoffbrücken unter Summation ihrer Dipolmomente an (siehe Formel; R=2‐Ethylhexyl). Durch elektrooptische Absorptionsspektroskopie wird gezeigt, dass hieraus eine deutlich verbesserte Ausrichtung des Farbstoffassoziats im elektrischen Feld resultiert.

Supramolecularly Engineered Aggregation of a Dipolar Dye: Vesicular and Ribbonlike Architectures

“…[4] Thus, simultaneous control over stacking arrangements and self-assembled architectures of functional dyes would produce organic optoelectronic materials with enhanced functionality. [8] The head-to-tail orientation (J-type aggregation) of merocyanine dyes [9] have been accomplished by Bosshard and co-workers [10] and Marks and co-workers [11] in vapor-phase deposited films, and by Würthner et al [12] in a thermodynamically equilibrated system using hydrogen-bonding interactions. [7] For functional dyes having a strong dipole moment such as merocyanines, control of the stacking arrangement is particularly challenging because aggregation of this type of chromophore is susceptible to strong dipolar interactions, thus resulting in antiparallel face-to-face stacking arrangements (H-type aggregation).…”

Solvent‐ and Guest‐Responsive Self‐Assembly of Hamilton Receptor Tethered Bis(merocyanine) Dyes

“…Merocyanine 9 with a barbituric acid acceptor group for the formation of sixfold hydrogen bonding to the Hamilton receptor was synthesized according to literature procedures and was used in molecular stimuli experiments with bis(merocyanine) 8. [15] Solvent-induced self-assembly: The first indication of the self-aggregation of 8 was obtained by mass spectrometry. Samples prepared by solvent evaporation from solutions of Figure S3 in the Supporting Information).…”

“…Merocyanine 9 with a barbituric acid acceptor group for the formation of sixfold hydrogen bonding to the Hamilton receptor was synthesized according to literature procedures and was used in molecular stimuli experiments with bis(merocyanine) 8. [15] Solvent-induced self-assembly: The first indication of the self-aggregation of 8 was obtained by mass spectrometry. Samples prepared by solvent evaporation from solutions of 8 in tetrahydrofuran/methylcyclohexane (10:90 vol %, THF/ MCH, c = 1.0 10 À4 m) were measured by MALDI-TOF and peaks that corresponded to the protonated cationic monomer ([M+H] + ) and sodium adduct ([M+Na] + ) as well as dimer ([M 2 +H] + ), trimer ([M 3 +H] + ), and traces of tetramer ([M 4 +H] + ) were observed (see Figure S3 in the Supporting Information).…”

“…From this K ass value, a binding constant of approximately 1.2 10 13 m À1 can be estimated in pure MCH by assuming a linear free-energy relationship with related Hamilton receptor host-guest systems. [15] Therefore, almost complete complex formation can be safely assumed in mixtures with high MCH ratios even under dilute conditions.…”

“…[13] As a consequence, the orthogonal character of hydrogen bonds and dipolar interactions might enable structurally well-defined assemblies and responsive materials. Although examples for well-defined architectures based on such interplay of hydrogen-bonding sites and dipolar merocyanine dyes have already been demonstrated, [14][15][16] novel functionalities such as responsiveness towards environmental changes remained unexplored. For this purpose, we have designed a system (8, Scheme 1) that contains two dipolar merocyanine dyes tethered by a Hamilton receptor [17] and investigated the solvent-and guest-responsive self-assembly of this novel molecular system.…”