rendered a reversible fluorescence enhancement in the presence of CO 2 and a
recovery with CO 2 released. Following this stimuli-responsive property, pTOC
could be used for detecting and quantifying trace amount of CO 2 among multiple
gas mixtures. Similarly, a TPE oxacalixarene macrocycle (14) with high fluorescence quantum yield (70%) was synthesized by a similar method in 2018 [38]. As
depicted in Fig. 2c, 14 as the monomer could be utilized to construct a porous
organic polymer (15), which presented a decent Brunauer–Emmett–Teller (BET)
surface area, specific pore volume, and fluorescence emissive properties. According
to the Förster resonance energy transfer (FRET) effect, 15 with blue-greenish
emission could be changed to a white-light emission material upon complexation
with tris(bipyridine)ruthenium (Ru
2+ ) as its complementary emission color.
7.2.4 Hybrid [n]Arenes
Through a hybrid approach, hybrid [n]arenes were constructed efficiently by
Szumna and coworkers in 2015 [39]. This medium-sized macrocyclic compound
with different alkoxybenzene units could be directly produced by condensation of
two commercially available alkoxybenzene monomers and formaldehyde as catalyzed by trifluoroacetic acid (TFA) (Fig. 3a). Generally speaking, hybrid [4]arenes
consisting of four alkoxybenzene units (16–19) are usually in a [2 + 2] or [3 + 1]
composite pattern. However, with the condensation of 18 and 19, a novel hybrid
macrocycle with [3 + 2] composite pattern could be facilely captured and isolated.
For the confirmation of the reversibility of the hybrid-forming reaction, a “scrambling” experiment by reaction of two conventional macrocyclic arenes based on
mono-benzene units was adopted. Subsequently, the results demonstrated that the
reaction was absolutely reversible and the distribution of the products was thermodynamically controlled. In a word, this acid-catalyzed thermodynamically favored
hybrid approach is very efficient and convenient.
Following this work, Yu and coworkers designed the first [2 + 1] pattern biphenyl-type hybrid [3]arene (20) in 2016 (Fig. 3b), which is composed of two 1,3,5trimethoxybenzene units and a 4,4-biphenol diethyl ether unit linked with methylene
bridges and exhibited a good binding affinity toward 1-dihexylammonium hexafluorophosphate [40]. Then, Szumna and coworkers synthesized a type of anthracene-based hybrid [4]arene (21) by using 1,4,5,8-tetramethoxyanthracene and 1,3dimethoxybenzene as the cyclic-forming monomers in 2017 (Fig. 3c), which could
be further used to recognize pyridinium iodide in chloroform due to its extended
cavity [41].
7.2.5 Calix[3]carbazole
In 2016, via a convenient one-step approach, a bowl-shaped calixarene derivative
named calix[3]carbazole (22) was efficiently obtained by Yang and coworkers
(Fig. 3d) [42]. Compared to many conventional carbazolyl-based macrocycles [43,
7 Emerging Macrocyclic Arenes Related to Calixarenes and Pillararenes
185
recovery with CO 2 released. Following this stimuli-responsive property, pTOC
could be used for detecting and quantifying trace amount of CO 2 among multiple
gas mixtures. Similarly, a TPE oxacalixarene macrocycle (14) with high fluorescence quantum yield (70%) was synthesized by a similar method in 2018 [38]. As
depicted in Fig. 2c, 14 as the monomer could be utilized to construct a porous
organic polymer (15), which presented a decent Brunauer–Emmett–Teller (BET)
surface area, specific pore volume, and fluorescence emissive properties. According
to the Förster resonance energy transfer (FRET) effect, 15 with blue-greenish
emission could be changed to a white-light emission material upon complexation
with tris(bipyridine)ruthenium (Ru
2+ ) as its complementary emission color.
7.2.4 Hybrid [n]Arenes
Through a hybrid approach, hybrid [n]arenes were constructed efficiently by
Szumna and coworkers in 2015 [39]. This medium-sized macrocyclic compound
with different alkoxybenzene units could be directly produced by condensation of
two commercially available alkoxybenzene monomers and formaldehyde as catalyzed by trifluoroacetic acid (TFA) (Fig. 3a). Generally speaking, hybrid [4]arenes
consisting of four alkoxybenzene units (16–19) are usually in a [2 + 2] or [3 + 1]
composite pattern. However, with the condensation of 18 and 19, a novel hybrid
macrocycle with [3 + 2] composite pattern could be facilely captured and isolated.
For the confirmation of the reversibility of the hybrid-forming reaction, a “scrambling” experiment by reaction of two conventional macrocyclic arenes based on
mono-benzene units was adopted. Subsequently, the results demonstrated that the
reaction was absolutely reversible and the distribution of the products was thermodynamically controlled. In a word, this acid-catalyzed thermodynamically favored
hybrid approach is very efficient and convenient.
Following this work, Yu and coworkers designed the first [2 + 1] pattern biphenyl-type hybrid [3]arene (20) in 2016 (Fig. 3b), which is composed of two 1,3,5trimethoxybenzene units and a 4,4-biphenol diethyl ether unit linked with methylene
bridges and exhibited a good binding affinity toward 1-dihexylammonium hexafluorophosphate [40]. Then, Szumna and coworkers synthesized a type of anthracene-based hybrid [4]arene (21) by using 1,4,5,8-tetramethoxyanthracene and 1,3dimethoxybenzene as the cyclic-forming monomers in 2017 (Fig. 3c), which could
be further used to recognize pyridinium iodide in chloroform due to its extended
cavity [41].
7.2.5 Calix[3]carbazole
In 2016, via a convenient one-step approach, a bowl-shaped calixarene derivative
named calix[3]carbazole (22) was efficiently obtained by Yang and coworkers
(Fig. 3d) [42]. Compared to many conventional carbazolyl-based macrocycles [43,
7 Emerging Macrocyclic Arenes Related to Calixarenes and Pillararenes
185