Synthesis, Structure, and Optical Properties of a Bis-Macrocycle Derived from a Highly Emissive 1,3,6,8-Tetra(1H-pyrrol-2-yl)pyrene

Abstract

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.

Synthesis of stable nonaromatic phenothiazinophyrins

“…1) possess quite different and novel features. 14 We and others have reported the synthesis of various PAH-embedded porphyrinoids such as biphenyl, 15 bipyridyl, 16 naphthalene, 17 anthracene, 18 phenanthrene, 19 phenanthroline, 20 fluorene, 21 dibenzofuran/thiophene, 22 phenothiazine 23 and pyrene 24 incorporated porphyrinoids. Some of these PAH-embedded porphyrinoids showed very unusual and interesting structures and spectral and coordination properties.…”

Porphyrinoid framework embedded with polycyclic aromatic hydrocarbons: new synthetic marvels

“…Gokulnath and co-workers 57 synthesized pyrene-embedded expanded porphyrinoid 131 and several pyrene-incorporated bis-calix[5]phyrins 132–133 , as presented in Scheme 24. Pyrene was reacted with Br 2 in nitrobenzene at 160 °C for 3 h to afford 1,3,6,8-tetrabromopyrene 134 .…”

Phenothiazine Embedded Dithiasmaragdyrins

“…13 10H-Phenothiazine, 1,9-dithienyl À 3,7-bis(1,1-dimethylethyl)-, 5,5-dioxide (13). To the solution of 10H-phenothiazine, 1,9-dibromo À 3,7-bis(1,1-dimethylethyl)-, 5,5-dioxide (12) (1.00 g, 2.92 mmol) and tetrakis-(triphenylphosphine)-palladium (0) (137 mg, 0.11 mmol) in 1,2-dimethoxyethane (30 mL), thiophene-2-boronic acid (3.02 g, 23.80 mol) was added slowly followed by a sodium bicarbonate solution (36 mL, 1 M). The reaction mixture was refluxed for 12 h, with vigorous stirring under a nitrogen atmosphere.…”

“…[6,7] In recent times, polycyclic aromatic hydrocarbon/heterocycle (PAH) embedded porphyrinoids have received significant attention due to their unique properties exhibiting the features of both PAH and porphyrinoids. Different polycyclic aromatic hydrocarbons/ heterocycles such as naphthalene, [8] dibenzofuran/ thiophene, [9,10] anthracene, [11] pyrene, [12] fluorene, [13,14] bipyridine, [15] phenanthroline, [16] phenothiazine, [17a-c] and so on have been incorporated into the framework of porphyrinoid in place of one or two pyrrole/heterocycle rings and explored their electronic and structural properties. Among different polycyclic aromatic heterocycles, phenothiazine (PTZ) is very important as this heterocycle is widely used in the synthesis of various organic dyes [18] such as methylene blue, [19] methylene green, [20] thionine [21] and also in certain pharmaceutical drugs such as chlorpromazine [22] and so on.…”