The synthesis of a new class of carbazole based macrocycles via [3 + 1] acid-catalyzed condensation is reported. Spectroscopic investigations and computational studies imply that these macrocycles have a large influence on the electronic structure in comparison to previously reported carbazole based macrocycles. Macrocycle 8 bearing a furan ring reversibly binds aqueous Hg 2+ with high affinity over other M n+ ions. The limit of detection (LOD) is ca. 100 nM. Hg 2+ binding was confirmed via X-ray diffraction analysis.

Herein, we report the synthesis of anthracene‐containing twisted cyclo[2]dipyrrin 1 by utilizing a non‐planar building block, 1,5‐dipyrrylanthracene (1,5‐DPA). The non‐planar nature of the macrocycle enhanced the solubility and helped in structural characterization. Macrocycle 1 adopts a twisted ‘figure of eight’ conformation stabilized by strong intramolecular H‐bonding interactions and exists as a pair of helical enantiomers, as revealed by X‐ray crystallographic analysis. More importantly, the sterically locked structure enabled facile optical resolution using chiral HPLC. The (P,P) and (M,M) enantiomers show moderate chiroptical properties, such as absorption dissymmetry factors |gabs| in the order of 10−3, and luminescence dissymmetry factors |glum| of 3.8×10−3 and 2.9×10−3 at 702 nm, respectively.

A tetra-functionalized pyrene precursor 4b is prepared using the Suzuki–Miyaura coupling of 1,3,6,8-tetrabromopyrene with N-Boc-2-pyrroleboronic acid. 4b displayed a blue emission with a high quantum yield (ϕF = 0.89). 4b is subjected to [3 + 2] Lewis acid-catalyzed condensation with 2,2′-bithiophene-dialcohol 5, affording a planar bis-N 2 S 2 internally linked with pyrene. The single-crystal X-ray structure of bis-N 2 S 2 revealed a planar conformation with all of the pyrrolic nitrogens and thiophenic sulfurs pointing toward the macrocyclic core. Further, the reduction of bis-N 2 S 2 was attempted in the presence of Zn/NH4Cl at room temperature in CHCl3. A sharp color change from pink to brown was observed presumably due to the formation of its reduced congener bis-N 2 S 2 –2H. However, the reduced species was found to revert back to its oxidized form over a period of 25 min in CHCl3. Density functional theory (DFT) studies reveal that the two monocyclic halves of bis-N 2 S 2 –2H exhibit differences in aromaticity depending on amino and imino pyrroles present inside each individual core. Such a conversion was also monitored by ultraviolet–visible (UV–vis) absorption spectral studies, and the exact composition of bis-N 2 S 2 –2H was confirmed by High-resolution/mass spectrometry (HR/MS) analysis. Experimental and theoretical studies reveal a weak aromatic character of bis-N 2 S 2 due to the absence of global conjugation.

A [3+2] acid-catalyzed condensation of a tetra-functionalized pyrene fluorophore (4) with dipyrromethane dicarbinol (5) resulted in the unprecedented formation of two bis-calix[5]phyrins (bis-calix[5]-1 and bis-calix[5]-2). The solution state structure of both bis-calix[5]phyrins was found to be similar with slight variations as confirmed by NMR spectral studies. Interestingly, two different linkages between the pyrene subunits with dipyrromethane dicarbinols led to two different calix[5]phyrin systems. Although the optical features seem to be similar, the single crystal X-ray structure obtained for bis-calix[5]-1provided the structural proof showing a non-planar, half-chair conformation with two meso-sp3 carbons. DFT studies were carried out to compare the HOMO-LUMO energy levels of both bis-calix[5]phyrins with the targetted conjugated bis-macrocycle (bis-N[Formula: see text]. Further, both the calix[5]-phyrins showed high Stokes shift (5404 cm[Formula: see text] and fluorescence quantum yield efficiency of around 90%.

Herein, we report the synthesis of anthracene‐containing twisted cyclo[2]dipyrrin 1 by utilizing a non‐planar building block, 1,5‐dipyrrylanthracene (1,5‐DPA). The non‐planar nature of the macrocycle enhanced the solubility and helped in structural characterization. Macrocycle 1 adopts a twisted ‘figure of eight’ conformation stabilized by strong intramolecular H‐bonding interactions and exists as a pair of helical enantiomers, as revealed by X‐ray crystallographic analysis. More importantly, the sterically locked structure enabled facile optical resolution using chiral HPLC. The (P,P) and (M,M) enantiomers show moderate chiroptical properties, such as absorption dissymmetry factors |gabs| in the order of 10−3, and luminescence dissymmetry factors |glum| of 3.8×10−3 and 2.9×10−3 at 702 nm, respectively.