The Boc and N,N'-dicyclohexylurea capped γ-amino acid upon monobromination showed phosphorescence in the solid state. The compound exhibited different photoluminescence intensity and lifetimes in crystals obtained from ethyl acetate and methanol. X-ray crystallography revealed that the intermolecular C=O…Br halogen bond directs the heavy atom effect to produce the phosphorescence.

Different assembly and behaviour of homologous discotic tricarboxyamides containing b-alanine and gaminobutyric acid have been investigated. From UV/Vis and FT-IR spectroscopy the tricarboxyamides have similar self-assembly patterns. But, the tricarboxyamide 2 containing g-aminobutyric acid residues forms a gel in aromatic solvents after heating, cooling and ageing. However, the b-alanine analogue 1 failed to form a gel under the same conditions. From FE-SEM studies the tricarboxyamide 1 shows unbranched rod like morphology but the tricarboxyamide 2 exhibits an entangled fiber network. Finally, the X-ray crystallography reveals that both the tricarboxyamides 1 and 2 adopt 3-fold intermolecular Hbonded helical columnar structures. Detailed structural analysis shows that the individual helical columnar structures of tricarboxyamide 2 are themselves self-assembled through multiple hydrophobic interactions between side chains and thereby form a supramolecular network structure. However, the tricarboxyamide 1 columns are self-assembled into a supramolecular bundle-like structure. The result indicates that side chain interactions have a drastic effect on quaternary structure and function.

stimuli such as temperature, [5] pH, [6] metal ions, [7] or ion strain. [8] Nevertheless, the complexity of motion executed by these actuators is limited by two factors: i) the whole volume of the material responses simultaneously to the stimuli; ii) the response lacks temporal regulation (that is, the response coincides with the stimulus, when the stimulus is ON, the response is ON, and no delays, periodicities, or other complex temporal patterns take place). To overcome these limitations, actuation should be spatially and temporarily regulated.Inspired by biological organisms where responses are controlled by biochemical signaling networks, [9] researchers have been developing hydrogel materials and actuators that are autonomously regulated by synthetic chemical reaction networks. [10] Initially, the research focused on using the Belousov-Zhabotinsky (BZ) reaction-the best-known chemical oscillator-or its close analogs to create periodical swelling/shrinking hydrogels. [11] Lately, however, the focus has moved towards using de novo enzymatic, [12] DNA, [13] and organic [14] reaction networks to regulate hydrogel materials. These reaction networks provide control over individual interactions between the system's components and therefore, they are more desirable than the BZ reaction from a design standpoint. Schulman, Gracias, and co-workers demonstrated the selective actuation of various parts of the hydrogel by specific DNA strands. [13b] Walther and coworkers [14a-c,15] and Huck and co-workers [12a] pioneered temporal control of sol-gel transitions by organic or enzymatic reaction networks. Pojman, Taylor, and co-workers demonstrated spatiotemporal regulation of gelation by an autocatalytic front. [12b,16] Nevertheless, autonomous spatiotemporal regulation of hydrogel actuators by de novo reaction networks remains elusive.In this work, we regulated the actuation of disulfide-containing hydrogel materials by autocatalytic fronts that release thiols. These actuators can perform complex motions (that is, gradual unrolling, wave movement, or sequential actuation) otherwise inaccessible to hydrogel actuators without an external control. Results and DiscussionDesigning hydrogel actuators that can be regulated by the autocatalytic front requires developing two compatible Regulating hydrogel actuators with chemical reaction networks is instrumental for constructing life-inspired smart materials. Herein, hydrogel actuators are engineered that are regulated by the autocatalytic front of thiols. The actuators consist of two layers. The first layer, which is regular polyacrylamide hydrogel, is in a strained conformation. The second layer, which is polyacrylamide hydrogel with disulfide crosslinks, maintains strain in the first layer. When thiols released by the autocatalytic front reduce disulfide crosslinks, the hydrogel actuates by releasing the mechanical strain in the first layer. The autocatalytic front is sustained by the reaction network, which uses thiouronium salts, disulfides of β-aminothiols, and maleimide...

The benzene-1,3,5-tricarboxyamide containing three l-methionine (1) self-assemble through 3-fold amide-amide hydrogen bonds and π-π stacking to fabricate one-dimensional nanorod like structure. However, the tyrosine analogue (2) carrying multiple H-bonding side chains lost the C3 symmetry and 3-fold amide-amide hydrogen bonds and developed a porous structure. The porous material exhibits ten times more N2 sorption (155 cc/g) than the columnar one, indicating that side chain-core interactions have a drastic effect on structure and function.

Autocatalytic reaction networks are instrumental for validating scenarios for the emergence of life on Earth and for synthesizing life de novo. Here, we demonstrate that dimeric thioesters of tripeptides with the general structure (Cys‐Xxx‐Gly‐SEt)2 form strongly interconnected autocatalytic reaction networks that predominantly generate macrocyclic peptides up to 69 amino acids long. Some macrocycles of 6–12 amino acids were isolated from the product pool and were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. We studied the autocatalytic formation of macrocycles in a flow reactor in the presence of acrylamide, whose conjugate addition to thiols served as a model “removal” reaction. These results indicate that even not template‐assisted autocatalytic production combined with competing removal of molecular species in an open compartment could be a feasible route for selecting functional molecules during the pre‐Darwinian stages of molecular evolution.