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• 4041-21-8 N-hexylcarbazole 

Relevant academic research and scientific papers

Sequence-Defined Macrocycles for Understanding and Controlling the Build-up of Hierarchical Order in Self-Assembled 2D Arrays

Anfinsen's dogma that sequence dictates structure is fundamental to understanding the activity and assembly of proteins. This idea has been applied to all manner of oligomers but not to the behavior of cyclic oligomers, aka macrocycles. We do this here by providing the first proofs that sequence controls the hierarchical assembly of nonbiological macrocycles, in this case, at graphite surfaces. To design macrocycles with one (AAA), two (AAB), or three (ABC) different carbazole units, we needed to subvert the synthetic preferences for one-pot macrocyclizations. We developed a new stepwise synthesis with sequence-defined targets made in 11, 17, and 22 steps with 25, 10, and 5% yields, respectively. The linear build up of primary sequence (1°) also enabled a thermal Huisgen cycloaddition to proceed regioselectively for the first time using geometric control. The resulting macrocycles are planar (2° structure) and form H-bonded dimers (3°) at surfaces. Primary sequences encoded into the suite of tricarb macrocycles were shown by scanning-tunneling microscopy (STM) to impact the next levels of supramolecular ordering (4°) and 2D crystalline polymorphs (5°) at solution-graphite interfaces. STM imaging of an AAB macrocycle revealed the formation of a new gap phase that was inaccessible using only C3-symmetric macrocycles. STM imaging of two additional sequence-controlled macrocycles (AAD, ABE) allowed us to identify the factors driving the formation of this new polymorph. This demonstration of how sequence controls the hierarchical patterning of macrocycles raises the importance of stepwise syntheses relative to one-pot macrocyclizations to offer new approaches for greater understanding and control of hierarchical assembly.

Host–Host Interactions Control Self-assembly and Switching of Triple and Double Decker Stacks of Tricarbazole Macrocycles Co-assembled with anti-Electrostatic Bisulfate Dimers

Hierarchical assembly provides a route to complex architectures when using building blocks with strong and structurally well-defined recognition elements. These rules are traditionally expressed using cationic templates with reliable metal-ligand bonding but use of anions is rare on account of weak anion–host contacts. We investigate an approach that relies on host–host interactions to fortify assemblies formed between bisulfate anion dimers, [HSO4???HSO4]2?, and shape-persistent macrocycles called tricarbazole triazolophanes. These macrocycles have significant self-association. In chloroform, they form high fidelity, triple-decker stacks with bisulfate dimers. The strength of host–host interactions allows for preferential formation of the 3:2 tricarb:bisulfate architecture over an ion-paired architecture seen with analogous macrocycles with much weaker self-association. Solvent was expected and found to tune host–host contacts enabling formation of a 2:2 complex and solvent-driven switching between triple- and double-stacked structures. Crystallography of the 2:2:2 complex supports the idea that significant host–host interactions with tricarb arises from dipole-stabilized π-stacking. Computational studies were also conducted further highlighting the importance of host–host interactions in stacked complexes of tricarb. These findings unambiguously verify the importance of host–host interactions in the assembly and stability of discrete, responsive anion-templated architectures.

Novel carbazole-based aggregation-induced emission-active gold(I) complexes with various mechanofluorochromic behaviors

A series of novel carbazole-based mono- and dinuclear gold(I) complexes with various lengths of alkyl chains were synthesized and characterized using nuclear magnetic resonance spectroscopy, elemental analysis and single crystal X-ray diffractometry. Their aggregation-induced emission characteristics were investigated by ultraviolet/visible and photoluminescence spectroscopy. Their solid-state mechanochromic luminescence behavior was also studied by photoluminescence spectroscopy. All gold(I) complexes based on a carbazole scaffold structure exhibited excellent aggregation-induced emission properties. Luminogens 1 and 2 showed reversible mechanochromism phenomena involving luminescent color transformation from yellow-green to green. Luminogens 3 and 4 exhibited switchable mechanochromic luminescence behavior involving fluorescent color change from colorless to green. The solid-state fluorescence of luminogens 5 and 6 can be switched between weak and strong fluorescence by mechanical force stimulus, and this conversion is irreversible.