Diastereoselective Control of Tetraphenylethene Reactivity by Metal Template Self‐Assembly

Abstract

The reaction of 4,4′,4′′,4′′′‐(ethene‐1,1,2,2‐tetrayl)tetraaniline with 2‐pyridinecarboxaldehyde and iron(II) chloride resulted, after aqueous workup, in the diastereoselective formation of an [Fe2L3]4+ triple‐stranded helicate structure, irrespective of the stoichiometry employed. The helicate structure was characterized in solution by multinuclear NMR spectroscopy, and in the solid state by single‐crystal X‐ray crystallography. The reaction of iron(II) tetrafluoroborate or iron(II) bistriflimide with the tetraaniline and 2‐pyridinecarboxaldehyde allowed the formation of an [Fe8L6]16+ cube when the appropriate stoichiometry was used, but these structures were unstable with respect to hydrolysis. The pendant amine groups on the helicate can be functionalized by reaction with acid chlorides or anhydrides, and the resulting functionalized tetraphenylethene (TPE) units were isolated by the reaction of the helicate with tris(2‐aminoethyl)amine. The emission properties of the TPE units were studied in THF/water mixtures, and they were found by dynamic light scattering to self‐assemble into large (av. diameter 250 nm) structures.

The efficiency of MSC‐based targeted AIE nanoparticles for gastric cancer diagnosis and treatment: An experimental study

“…TPE and PTX were loaded onto PCL‐PEG by self‐assembly later. The 1 H‐NMR spectrum of PCL‐PEG/TPE/PTX (Figure 1a) shows proton peaks at 6.7–7.2 ppm representing the benzene rings of TPE, and the peak around 4.3 ppm representing PTX; the characteristic proton peaks of PCL‐PEG‐NH 2 were also observed, suggesting the successful formation of the PCL‐PEG/TPE/PTX complex 25–27 . Sharp and intense bands of the PCL‐PEG‐NH 2 were shown at 1732 cm −1 in the FT‐IR spectrum, which were caused by the stretching of carboxylic ester (C=O) groups in PCL.…”

Covalent Post‐Assembly Modification: A Synthetic Multipurpose Tool in Supramolecular Chemistry

“…Beves and co-workers recently described the use of M2L3 metallohelicates as templates to control the regiospecific functionalization of a symmetric small molecule (Scheme 3). [33] The authors formed Fe II 2L3 triple helicate 4 by the subcomponent self-assembly [34] of tetrakis(4-aminophenyl)ethene with 2formylpyridine and iron(II) chloride in acetonitrile. Due to steric constraints, the only observed isomer of 4 involved coordination of geminal aniline groups rather than aniline groups on either side of the double bond.…”

“…helicate 4 permits regioselective di-functionalization of geminal aniline groups in tetrakis(4-aminophenyl)ethene. [33] Post-assembly acylation of the exposed amines of 4 using acyl chlorides and anhydrides afforded hexa-acylated 5. Subsequent treatment with tris(2-aminoethyl)amine provided complex 6 and di-acylated ligand 7 (R = Me, Ph and C7H15).…”

“…Covalent PAM is especially powerful when used to introduce functional groups that cannot be incorporated into supramolecular building blocks due to incompatibilities with self-assembly. [19,33] This advantage is notable in Eggers and Ziener's work on the functionalization of Zn II and Co II molecular grids (28a and 28b, respectively). [45] The authors found that the copper(I)-catalyzed and strain-promoted azide-alkyne reactions (CuAAC and SPAAC, respectively) were problematic for PAM of 28, as CuAAC caused decomposition of the complex while SPAAC requires unstable and expensive strained alkynes.…”

“…Scheme 3. PAM of Fe II 2L3 helicate 4 permits regioselective di-functionalization of geminal aniline groups in tetrakis(4-aminophenyl)ethene [33]. Post-assembly acylation of the exposed amines of 4 using acyl chlorides and anhydrides afforded hexa-acylated 5.…”