G2ÁBArF (Entry 5), suggesting that the flexible octyl group can twist to fit into the
host cavity.
Particularly, G6ÁBArF and G7Á2BArF, bearing 1,4-diazabicyclo [2.2.2] octane
(DBO) cations, exhibit the largest association constants with 44BP4 (of the magnitude of 10
4 M
À1 , Entries 12 and 14), while 44BP3 cannot bind with G6ÁBArF and
G7Á2BArF (Entries 11 and 13), suggesting that spherical DBO moieties are excellent
matches in size and shape with the cavity of 44BP4 but cannot fit into the cavity
of 44BP3.
In addition, cobaltocenium G23ÁPF 6 , a guest molecule with a tridimensional
shape and a relatively large size, can be encapsulated into the cavity of 44BP4OH with a strong binding ability. For this host–guest pair, the K a values are
influenced by the effects of solvent polarity. As shown in Table 1 (Entries 60–64),
no significant complexation was observed in the highly polar solvents
DMSO-d 6 (Entry 61) and DMF-d 7 (Entry 62), and a medium binding affinity
(K a = 250 Æ 20 M
À1 , Entry 60) was demonstrated in acetone-d 6 . Particularly, the
K a values in the relatively low-polarity mixed solvents 1:1 (v/v) acetone-d 6 /CDCl 3
((2.1 Æ 0.3) Â 10
3 M
À1
, Entry 63) and acetone-d 6 /CD 2 Cl 2 ((3.1 Æ 0.3) Â 10
3 M
À1 ,
Entry 64) are higher than those in pure acetone-d 6 .
22BPns (n = 4–8) also display strong complexation with ammonium guests such
as G11ÁBArF, G12ÁBArF and G20ÁBArF. The results of
1 H NMR titration experiments suggest that all of these macrocycles exhibit strong binding affinities towards
G11ÁBArF, G12ÁBArF, and G20ÁBArF, with K a values up to 10
3 and 10
4 M
À1
(Entries 17–26, 50–53), except for G20ÁBArF & 44BP4 (640 Æ 30 M
À1 , Entry
49). For these three guests, medium 22BP5 and 22BP6 exhibited the strongest
affinities. In addition, 22BPns displayed remarkably different K a values with diquat
G20ÁBArF and paraquat G14ÁBArF. For example, the K a value of G20ÁBArF by
22BP5 ((2.2 Æ 0.2) Â 10
3 M
À1 , Entry 50) is 35 times higher than that for G14ÁBArF
(63 Æ 13 M
À1 , Entry 32).
12.7 Pyridinium-Based Dicationic Guests
Our group demonstrated the binding behaviors of biphenarenes and their derivatives
toward several types of pyridinium-based dicationic guests in organic solutions or in
water (Table 1, Entries 27–59). These guests include paraquat derivatives with
different substituents (G13
2+
–G15
2+
); bis(bipyridinium) cations with different
linkers (G16
2+
–G19
2+
); diquat and phenanthrolinediium with different counter
anions (G20
2+ and G21
2+
), as well as diazapyrenium (G22
2+ ).
Water-soluble 44CBPns can bind dicationic guests more efficiently in aqueous
solution. The K a values for 44CBP3 and 44CBP4 with dicationic guests in water
(Entries 27–28, 38–41, 43, and 54), are far greater than those of alkyl-substituted
(Entries 29–30, 45–48, and 55–56) or hydroxylated 44BPns (Entries 36–37, 42, 44,
and 57–58) in organic solvents, in the range of 10
3
–10
4 M
À1 . For example, there was
no interaction for 44BP3 with paraquat derivative G14Á2BArF in organic solvent.
However, 44CBP3 exhibited a strong binding affinity towards G14Á2Br, with a K a
328
B. Li et al.
host cavity.
Particularly, G6ÁBArF and G7Á2BArF, bearing 1,4-diazabicyclo [2.2.2] octane
(DBO) cations, exhibit the largest association constants with 44BP4 (of the magnitude of 10
4 M
À1 , Entries 12 and 14), while 44BP3 cannot bind with G6ÁBArF and
G7Á2BArF (Entries 11 and 13), suggesting that spherical DBO moieties are excellent
matches in size and shape with the cavity of 44BP4 but cannot fit into the cavity
of 44BP3.
In addition, cobaltocenium G23ÁPF 6 , a guest molecule with a tridimensional
shape and a relatively large size, can be encapsulated into the cavity of 44BP4OH with a strong binding ability. For this host–guest pair, the K a values are
influenced by the effects of solvent polarity. As shown in Table 1 (Entries 60–64),
no significant complexation was observed in the highly polar solvents
DMSO-d 6 (Entry 61) and DMF-d 7 (Entry 62), and a medium binding affinity
(K a = 250 Æ 20 M
À1 , Entry 60) was demonstrated in acetone-d 6 . Particularly, the
K a values in the relatively low-polarity mixed solvents 1:1 (v/v) acetone-d 6 /CDCl 3
((2.1 Æ 0.3) Â 10
3 M
À1
, Entry 63) and acetone-d 6 /CD 2 Cl 2 ((3.1 Æ 0.3) Â 10
3 M
À1 ,
Entry 64) are higher than those in pure acetone-d 6 .
22BPns (n = 4–8) also display strong complexation with ammonium guests such
as G11ÁBArF, G12ÁBArF and G20ÁBArF. The results of
1 H NMR titration experiments suggest that all of these macrocycles exhibit strong binding affinities towards
G11ÁBArF, G12ÁBArF, and G20ÁBArF, with K a values up to 10
3 and 10
4 M
À1
(Entries 17–26, 50–53), except for G20ÁBArF & 44BP4 (640 Æ 30 M
À1 , Entry
49). For these three guests, medium 22BP5 and 22BP6 exhibited the strongest
affinities. In addition, 22BPns displayed remarkably different K a values with diquat
G20ÁBArF and paraquat G14ÁBArF. For example, the K a value of G20ÁBArF by
22BP5 ((2.2 Æ 0.2) Â 10
3 M
À1 , Entry 50) is 35 times higher than that for G14ÁBArF
(63 Æ 13 M
À1 , Entry 32).
12.7 Pyridinium-Based Dicationic Guests
Our group demonstrated the binding behaviors of biphenarenes and their derivatives
toward several types of pyridinium-based dicationic guests in organic solutions or in
water (Table 1, Entries 27–59). These guests include paraquat derivatives with
different substituents (G13
2+
–G15
2+
); bis(bipyridinium) cations with different
linkers (G16
2+
–G19
2+
); diquat and phenanthrolinediium with different counter
anions (G20
2+ and G21
2+
), as well as diazapyrenium (G22
2+ ).
Water-soluble 44CBPns can bind dicationic guests more efficiently in aqueous
solution. The K a values for 44CBP3 and 44CBP4 with dicationic guests in water
(Entries 27–28, 38–41, 43, and 54), are far greater than those of alkyl-substituted
(Entries 29–30, 45–48, and 55–56) or hydroxylated 44BPns (Entries 36–37, 42, 44,
and 57–58) in organic solvents, in the range of 10
3
–10
4 M
À1 . For example, there was
no interaction for 44BP3 with paraquat derivative G14Á2BArF in organic solvent.
However, 44CBP3 exhibited a strong binding affinity towards G14Á2Br, with a K a
328
B. Li et al.