We have analyzed the nature and role of functional groups on the self‐assembly modes and the physical properties of multicomponent gels with structurally similar individual components. The gelation properties of individual and mixed enantiomeric compounds of biphenyl bis‐(amides) of alanine (BPA) or phenylalanine (BPP) methyl ester were analyzed in various solvent/solvent mixtures. Multicomponent gels were formed by mixing the enantiomeric BPP compounds at a lower concentration, but a higher concentration was required for mixed alanine‐based BPA gels. The comparison of the mechanical strength of the individual and mixed BPP compounds indicated that the mixed BPP gels displayed enhanced mechanical strength (∼2‐fold increase) in p‐xylene, but a weaker gel was observed in DMSO/water. However, a reverse trend was observed for BPA gels, indicating the role of functional groups in the gel network formation. X‐ray diffraction analysis of the gelator and the xerogels in the solid state confirmed the formation of co‐assembled networks in mixed enantiomeric gels. The stability of the gels towards anions was evaluated by analyzing the anion induced stimuli‐responsive properties. These results indicate the effective modeling of the functional groups of the individual components could lead to multicomponent gels with tunable properties.
In this study, we have prepared new tripyrranes embedded with azulene bearing two meso-pentafluorophenyl substituents. They were obtained as diastereomers in high yield which were separated using conventional column chromatography. Their distinct solution structures were unambiguously confirmed by NMR and mass analysis. Our synthetic strategy is simple and straightforward due to the reactivity of 1,3-positions of azulene, which underwent Lewis acid-catalyzed condensation with pyrrole-2-carbinol. These diastereomers were further subjected to acid-catalyzed (CF3COOH) condensation with pyrrole dicarbinol to afford the target N-confused azuliporphyrin (reduced form) in trace amount. However, we obtained the tris-meso-pentafluorophenyl substituted azulicorrole (AzCorA) as major product due to an unprecedented scrambling of the azulitripyrranes. The structural characterization of newly synthesized key precursors and macrocycles was done with the aid of high-resolution mass analyses, and 1H and 2D NMR analyses. The single crystal X-ray structure obtained for AzCorA revealed that the azulene subunit is tilted by 34.03[Formula: see text] due to the steric congestion of inner-NHs.
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