Binding enhancements of nicotinic acid to water-soluble zinc porphyrins based on triple attractions of coordination, Coulomb, and CH-π interactions

Article abstract of DOI:10.1248/cpb.56.969

The binding of amines to artificial zinc-porphyrin receptors 1-4 was examined in basic aqueous solutions. For nicotinic acid and 3,5- dicarboxypyridine, substantial binding enhancements were observed compared to other amines with no π system or carboxyl group. This observation suggested that interligand attractions of Coulomb and CH-π interactions in addition to N-atom coordination can act effectively as recognition factors. The differences in the Coulomb interaction between carboxylate and sulfonate anions were also discussed.

Full text of DOI:10.1248/cpb.56.969

July 2008
Chem. Pharm. Bull. 56(7) 969—972 (2008)
969
Binding Enhancements of Nicotinic Acid to Water-Soluble Zinc
Porphyrins Based on Triple Attractions of Coordination, Coulomb, and
p
CH– Interactions
Hiroyasu IMAI,* Hiroki MUNAKATA, and Yoshio UEMORI
Faculty of Pharmaceutical Sciences, Hokuriku University; 3 Ho Kanagawa-Machi, Kanazawa 920–1181, Japan.
Received March 14, 2008; accepted April 23, 2008; published online April 23, 2008
The binding of amines to artificial zinc-porphyrin receptors 1—4 was examined in basic aqueous solutions.
For nicotinic acid and 3,5-dicarboxypyridine, substantial binding enhancements were observed compared to
other amines with no p system or carboxyl group. This observation suggested that interligand attractions of
Coulomb and CH–p interactions in addition to N-atom coordination can act effectively as recognition factors.
The differences in the Coulomb interaction between carboxylate and sulfonate anions were also discussed.
Key words water-soluble zinc porphyrin; nicotinic acid; molecular recognition; coordination; Coulomb interaction; CH–p in-
teraction
The examination of the binding of small biomolecules tion.13) The N atom of amines is not protonated under the
with artificial receptors in aqueous media is one of the tradi- basic experimental conditions (pH 10.4), thereby the N atom
tional approaches to obtain fundamental information on mo- of the amines can coordinate to the zinc ion and substitute
lecular recognition in biological and pharmaceutical condi- the bound H2O of the porphyrins. The binding equilibrium
tions. Binding enhancements and selectivity for guests by between zinc porphyrin ZnP and amine L is expressed as fol-
receptors result from additively and/or cooperatively com- lows:
bined weak non-covalent interactions. Synthetic metallopor-
phyrins have been widely used as receptors for biomolecules
ZnP·H2OꢀL
ZnP·LꢀH2O
and their analogs; however, not many studies in aqueous so- where the binding constant is given as
lutions1—12) have been reported because of the lipophilic na-
[ZnP⋅L]
[ZnP⋅H2O][L]
ture of porphyrins. In a previous work,8) we reported amino
K ꢁ
acid chiral recognition by a water-soluble zinc porphyrin,
where three interactions act as the recognition factors. Two of
the interactions are attractive, but the remaining interaction The spectral changes correspond to the N coordination of the
has not yet been identified as attractive or repulsive. Here, we
examined the binding behavior of zinc porphyrins 1—4 with
amine guests in basic aqueous solutions, where the porphyrin
substituents near the central zinc ion can differently interact
with the bound guests. The binding data suggested the exist-
ence of three types of simultaneous attractive interactions be-
tween the zinc porphyrins (2, 4) and the anions of nicotinic
acid and 3,5-dicarboxypyridine.
Figure 1 shows visible spectra of 4 upon titration of nico.
Results and Discussion
In the absence of amine, zinc porphyrins exist as five coor-
Chart 2. Amine Guests
dinated species with a bound H2O molecule in aqueous solu-
Fig. 1. Visible Absorption Spectra of 4 upon Titration of nico
At 25.0 °C in aqueous solution buffered with NaHCO3–Na2CO3 (pH 10.4, I = 0.02).
[4]ꢁ3.49ꢂ10ꢃ6 mol/l; [nico]ꢁ0, 1.44ꢂ10ꢃ3
, , , ,
2.88ꢂ10ꢃ3 4.30ꢂ10ꢃ3 5.71ꢂ10ꢃ3
7.11ꢂ10ꢃ3, 8.50ꢂ10ꢃ3, 9.89ꢂ10ꢃ3 mol/l.
Chart 1. Water-Soluble Zinc Porphyrins
∗ To whom correspondence should be addressed. e-mail: h-imai@hokuriku-u.ac.jp
© 2008 Pharmaceutical Society of Japan

970
Vol. 56, No. 7
Table 1. Binding Constants (l/mol) of Amines with Zinc Porphyrinsa)
Amine
Compd.
aet
gly
mim
py
nico
dc-py
1
2
3
4
9.9
(2/0)b)
12
(1/0)
10
(2/0)
10
(1/0)
110
(2/1)
57
(1/1)
150
(2/1)
66
59
(2/0)
190
(1/0)
66
(2/0)
240
(1/0)
9.4
(2/0)
42
(1/0)
15
(2/0)
64
(1/0)
130
(2/1)
230
(1/1)
180
(2/1)
350
(1/1)
1000
(2/2)
1200
(1/2)
1600
(2/2)
2000
(1/2)
(1/1)
Fig. 2. Correlation of log K with √ꢀI
ꢀ; 4ꢀdc-py (1/2, ꢃ2.26), ꢁ; 3ꢀdc-py (2/2, ꢃ4.04), ꢂ; 4ꢀnico (1/1, ꢃ0.97), ꢃ;
4ꢀmim (1/0, ꢃ0.06), ꢄ; 3ꢀnico (2/1 ꢃ2.92), respectively. The cation/anion ratio and
the slope value are in parentheses.
a) At 25 °C, pH 10.4 (Iꢁ0.02). Errors for K are within 16%. b) Ratios for
cation/anion are in parentheses.
amine, since the addition of acetate ion to the zinc por-
phyrins does not cause any spectral change. The binding con-
stants of the amines to the zinc porphyrins were determined
from the spectra and are listed in Table 1. The binding behav-
ior reflects the interligand interactions between the bound
amines and the –C(CH3)3 or –N(CH3)3+ of the porphyrins and
solvation-desolvation phenomena of the solutes, in addition
to the coordination of the N atom to the central zinc ion. The
K values of aet are substantially small due to the weak lig-
and-exchange ability of the N atom from the bound H2O. It
has also been reported that the K values for the amine bind-
ing to anionic water-soluble zinc porphyrins are small.13)
Since the –OH and –CH2– groups of aet cannot interact
strongly with the porphyrin substituents, similar K values are
obtained for different porphyrins with aet, suggesting that the
zinc acidity is similar in each case.
Table 2. Binding Constants (l/mol) of Sulfonatesa)
Compd.
K(ams)
K(ams)/K(gly)
0.69
K(s-py)
K(s-py)/K(nico)
1
2
3
4
76
ndb)
120
nd
120
190
160
300
0.94
0.82
0.92
0.86
0.80
a) At 25 °C, pH 10.4 (Iꢁ0.02). b) Could not be determined due to their small spec-
tral changes.
Table 3. 1H-NMR Shiftsa) upon Addition of dc-py
dC(CH3)3
ꢀdc-py
dN(CH3)3
ꢀdc-py
Compd.
Dd
Dd
1
2
3
4
2.326
2.005
2.281
1.931
2.336
2.091
0.010
0.086
For the binding of carboxylate amines to the porphyrins,
Coulomb interactions between the –COOꢃ group of the for-
ꢃ0.079 ꢃ0.271 ꢃ0.192
ꢃ0.064 ꢃ0.241 ꢃ0.177
2.243 ꢃ0.038
1.934 0.004
ꢀ
mer and the –N(CH3)3 group of the latter in addition to the
coordination were expected. In fact, the binding constants
increased with the number of possible Coulomb interactions;
the K values with gly are larger as compared to those with
aet, and this is more obvious for 1 and 3 (the cation/anion
ratio is 2/1 in the gly adducts) than for 2 and 4 (the
cation/anion ratio is 1/1). Since the pKa values of gly (9.57)14)
and aet (9.52)14) are similar, comparisons of their binding
data for 2 or 4 may provide the binding enhancement factor
by Coulomb interactions with a cation/anion ratio of 1/1, that
can be estimated to be ca. 5—7 times in K and 3.9—4.6
kJ/mol in ꢃDG° (25 °C). The effects of the Coulomb
interaction were reasonably supported by examining the
dependence of K on the ionic strength I, where the slope of
the plot of log K versus √ꢀI can be related to the magnitude of
a) At 27 °C in D2O, 4ꢂ10ꢃ3 mol/l Na2CO3; [porphyrin]ꢁ5ꢂ10ꢃ4 mol/l, [dc-
py]ꢁ5ꢂ10ꢃ3 mol/l.
Table 4. Binding Constantsa) (l/mol) in H2Ob)/CH3OH (1/1)
Amine
Compd.
aet
mim
nico
dc-py
3
4
ndc)
5.0
15
80
ndc)
156
900
670
a) At 25°C. b) pH 10.4 (Iꢁ0.02). c) Could not be determined due to their small
spectral changes.
the Coulomb interaction.15,16) The slope values in Fig. 2 are be observed for the binding of nico and s-py, where the bind-
well correlated to the magnitude of the possible Coulomb in- ing constants for these amines are fairly close.
teractions that enhance the binding.
Another apparent feature shown in Table 1 is that the bind-
Table 2 compares binding constants for carboxylates and ing constants for mim and pyridines, which have p systems,
sulfonates. The pKa value of 9.57 for gly is considerably are large with 2 and 4 containing –C(CH3)3 groups. The fact
1
higher than that of 5.7517) for ams, indicating an appreciably that the –C(CH3)3 signals of 2 and 4 in H-NMR substan-
weaker donor ability of the N atom of ams than that of gly. tially shift upfield upon dc-py binding indicates that the
However, the binding constants for ams are only slightly –CH3 groups exist above the p system of the bound amines
small as compared to those for gly. Since the binding data (Table 3).18) When the binding was examined in CH3OH/H2O
cannot be correlated to the difference in pKa, this may be ex- (1 : 1), similar binding enhancements have been retained
plained in terms of the increased Coulomb interaction with (Table 4).19) These results suggest that the binding enhance-
the sulfonate anion than with the carboxylate anion that ments of the amines with p system for 2 and 4 could be at-
eclipses the poor donor ability of ams. A similar result can tributed to the CH–p20,21) or van der Waals interactions but

July 2008
971
were examined by spectrophotometric titration of amines in aqueous solu-
tion buffered with NaHCO3–Na2CO3 (pH 10.4, Iꢁ0.02). The ionic strength I
was changed with NaCl. The binding constants were determined based on
the published method.25,26)
Synthesis Compound 2 was obtained according to the literature.25)
Compounds 1, 3, and 4 were prepared by methods similar to that for 2.
5a,10a,15b,20b-Tetrakis(2-aminophenyl)porphyrinatozinc(II) (5)
To a solution of 5a,10a,15b,20b-tetrakis(2-aminophenyl)porphyrin (0.200
g, 0.296 mmol) and 2,6-lutidine (0.30 ml, 1.3 mmol) in tetrahydrofuran
(100 ml) was added zinc chloride (0.300 g, 2.20 mmol). After stirring the so-
lution for 4 h at room temperature, the volume was reduced to a quarter on
an evaporator. Chloroform (200 ml) was added to the solution and the mix-
ture was washed twice with water (200 ml). The organic layer was dried over
anhydrous Na2SO4 then was evaporated to dryness. The solid was purified
on a silica-gel column (2.5ꢂ20 cm, chloroform); yield 0.168 g (76.7%). 1H-
NMR (500 MHz, DMF-d7) d 4.59 (s, 8H, NH2), 7.06 (t, 4H, ph), 7.22 (d,
4H, ph), 7.55 (t, 4H, ph), 7.80 (d, 4H, ph), 8.86 (s, 8H, pyrrole); Vis (CHCl3)
lmax 426, 517 (sh), 555, 595 nm. MS m/z 737 ((MꢀH)ꢀ) (Calcd for
C44H32N8Zn: 736).
Fig. 3. Schematic Representation for the Binding Enhancement of nico to
2 and 4 Based on Coordination (
Interactions
), Coulomb (
), and CH–p (ꢀ)
not to the hydrophobic interactions. The comparison of the
binding data of py between 1 and 2 or 3 and 4 showed the
binding enhancement factor between the py p system and
–C(CH3)3 to be ca. 4 times in K and 3.5—3.6 kJ/mol in
ꢃDG° (25 °C). A similar binding enhancement has been
reported in nonpolar organic solvents,22) but it was hardly
observed in aqueous solutions due to the strong solvent–
solute interactions.13) Another attraction between the bound
5a,10a,15b,20b-Tetrakis(2-(N,N-dimethylaminomethylcarbonyl-
amino)phenyl)porphyrinatozinc(II) (6) To
a suspended solution of
(CH3)2NCH2COOH·HCl (0.600 g, 4.30 mmol) in CH2Cl2 (30 ml) was added
dropwise (COCl)2 (2.00 ml, 15.5 mmol). The mixture was stirred for 2 h at
room temperature and was evaporated to dryness then dissolving the solid in
CH2Cl2 (30 ml). To an ice-cold solution of 5 (0.150 g, 0.203 mmol) and tri-
ethylamine (8 ml) in CH2Cl2 (100 ml) was added the above acid-chloride so-
lution. After stirring for 3 h at room temperature, the solution was washed
twice with water (100 ml). The solution was dried over anhydrous Na2SO4
ꢀ
amines with p systems and –N(CH3)3 may be possible in
aqueous solutions in the form of cation–p interactions that
play biologically important roles.23,24) For 1 and 3, however,
the comparison of the binding data of aet and py suggested then was evaporated to dryness. The solid was purified on a silica-gel col-
1
umn (2.5ꢂ20 cm, chloroform); yield 0.108 g (49.3%). H-NMR (500 MHz,
that such the interactions can be negligible here. Further, the
fact that no upfield shift of the –N(CH3)3ꢀ signal upon dc-py
CDCl3) d 0.21 (s, 24H, N(CH3)2), 2.19 (s (br), 8H, CH2), 7.53 (s, 4H, ph),
7.82 (s, 4H, ph), 7.97 (s, 4H, ph), 8.69 (m, 8H, ph, NHCO), 8.86 (s, 8H, pyr-
binding is observed supports this suggestion.
role); Vis (CHCl3) lmax 427, 517 (sh), 557, 595 nm. MS m/z 1077 ((MꢀH)ꢀ)
(Calcd for C60H60N12O4Zn: 1076).
With regard to atropisomerism, cis-types 1 and 3 show
somewhat small K values except for aet than trans-types 2
and 4. Although binding enhancements for trans-types with
nico and dc-py are more apparent than cis-types, the differ-
ences between 1 and 3 or 2 and 4 are not sufficiently large to
affect the selectivity for amines. Together with the NMR
data, the relative configuration of the porphyrin substituents
in the two atropisomers might provide similar interactions
with the guest amines.
In conclusion, receptors 2 and 4 apparently induce attrac-
tions for the nitrogen atom as a donor, anionic group, and p
system of a guest molecule based on coordination, Coulomb
interaction, and CH–p interaction, respectively (Fig. 3). The
binding enhancements for nico and dc-py are additive for the
double interactions; for example, a comparison of the bind-
5a,10a,15b,20b-Tetrakis(2-(trimethylammoniomethylcarbonyl-
amino)phenyl)porphyrinatozinc(II) Chloride (1) A solution of 6 (0.090
g, 0.083 mmol) in N,N-dimethylformamide (10 ml) and CH3I (0.500 ml,
6.44 mmol) was stirred for 3 h at room temperature. The addition of ether to
the solution afforded a solid of the corresponding iodide of 1. The iodide
was converted to chloride, 1, by ion-exchange column chromatography
1
(CH3OH, 3ꢂ30 cm (Amberlyst A-21)); yield 0.057 g (53%). H-NMR (400
MHz, DMSO-d6) d 2.27 (s, 36H, N(CH3)3), 7.70 (t, 4H, ph), 7.87 (t, 4H,
ph), 7.97 (d, 4H, ph), 8.10 (d, 4H, ph), 8.54 (s, 4H, pyrrole), 8.59 (s, 4H, pyr-
role), 8.95 (s, 4H, NHCO); Vis (H2O/NaHCO3-Na2CO3, pH 10.4) lmax (log
e) 425 (5.51), 520 (sh) (3.46), 558 (4.24), 597 (3.69) nm; Anal. Calcd for
C64H72N12O4ZnCl4·8H2O: C, 53.96; H, 6.23; N, 11.80. Found: C, 54.01; H,
5.90; N, 11.78. MS m/z 1243 (Mꢀ) (Calcd for C64H72N12O4ZnCl3: 1243).
5a,10b,15a,20b-Tetrakis(2-(trimethylammoniomethylcarbonyl-
amino)phenyl)porphyrinatozinc(II) Chloride (3) Compound 3 was ob-
tained by a procedure similar to that for 1 by using 5a,10b,15a,20b-
tetrakis(2-aminophenyl)porphyrin instead of 5a,10a,15b,20b-tetrakis(2-
ing data of 3-py and 4-nico systems yields the stability factor aminophenyl)porphyrin as the starting material. 1H-NMR (400 MHz,
DMSO-d6) d 2.44 (s, 36H, N(CH3)3), 7.72 (t, 4H, ph), 7.85 (m, 8H, ph),
of 23 times in K and 7.6 kJ/mol in ꢃDG°, which well agree
with the two additive contributions noted above. The com-
bined weak attractions effectively recognize these small guest
molecules. These porphyrins also showed a possibility to act
as a receptor for nicotine derivatives in aqueous solution.
8.08 (d, 4H, ph), 8.52 (s, 8H, pyrrole), 9.13 (s, 4H, NHCO); Vis (H2O/
NaHCO3–Na2CO3, pH 10.4) lmax (log e) 424 (5.57), 519 (sh) (3.46), 558
(4.24), 597 (3.69) nm; Anal. Calcd for C64H72N12O4ZnCl4·5H2O: C, 56.08;
H, 6.03; N, 12.26. Found: C, 55.99; H, 5.91; N, 12.09. MS m/z 1243 (Mꢀ)
(Calcd for C64H72N12O4ZnCl3: 1243).
5a ,10b -Bis((2-(trimethylammoniomethylcarbonylamino)phenyl)-
15a,20b-bis(2-pivalamidophenyl)porphyrinatozinc(II) Chloride (4) was ob-
tained by a procedure similar to that for 2 by using 5a,10b,15a,20b-
tetrakis(2-aminophenyl)porphyrin instead of 5a,10a,15b,20b-tetrakis(2-
aminophenyl)porphyrin as the starting material. The synthesis of 4 is as fol-
lows.
Experimental
General All chemicals were purchased commercially and were used as
received without further purification unless otherwise noted. Aminoethanole
(aet), 1-methylimidazole (mim), and pyridine (py) were purified by distilla-
tion. Water for visible spectral measurements was purified by use of a
SIBATA PP-101 water purification apparatus. Silica gel for column chro-
matography was Wakogel C-200 (Wako).
Visible absorption spectra were recorded on a Hitachi U-3000 spectropho-
tometer. Proton NMR spectra were obtained from a JEOL JNM-ECP-500
(500 MHz) or a JEOL JNM-GSX-400 (400 MHz) spectrometer with tetra-
methylsilane or sodium 3-trimethylsilyl-propanesulfonate as the internal
standard. FAB-MS spectra were measured on a JEOL JMS-SX-102A mass
spectrometer using magic bullet as matrix.
5a,10b-Bis(2-(triphenylmethylamino)phenyl)-15a,20b-bis(2-
aminophenyl)porphyrin (7) To an ice-cold solution of 5a,10b,15a,20b-
tetrakis(2-aminophenyl)porphyrin (2.000 g, 2.96 mmol) and triethylamine
(5.0 ml) in CH2Cl2 (800 ml) was added dropwise a solution of triphenyl-
methyl bromide (2.08 g, 6.44 mmol) in CH2Cl2 (400 ml). The reaction mix-
ture containing some kinds of partly amino-protected porphyrins was evapo-
rated to dryness and the solid was chromatographed on a silica-gel column
(benzene, 4ꢂ30 cm). The third band of 7 was separated and evaporated to
1
dryness, yield 0.836 g. (24.4%). H-NMR (400 MHz, CDCl3) d ꢃ2.69 (s,
Binding Experiments Visible absorption spectra were recorded on a
Hitachi U-3000 spectrophotometer. The binding of amines to the porphyrins
2H, pyrrole–NH), 3.61 (s, 4H, NH2), 5.09 (s, 6H, Cph3), 6.65 (d, 2H, ph),

972
Vol. 56, No. 7
6.94 (d, 12H, Cph3), 7.03 (d, 12H, Cph3), 7.19 (m, 8H, ph), 7.61 (d, 2H, ph), References and Notes
7.64 (t, 2H, ph), 7.89 (d, 2H, ph), 8.90 (d, 2H, ph), 8.94 (m, 8H, pyrrole); Vis
(CHCl3) lmax 420, 519, 553, 591, 654 nm. MS m/z 1159 ((M+H)ꢀ) (Calcd
for C82H62N8: 1158).
1) Liu T., Schneider H.-J., Angew. Chem. Int. Ed., 41, 1368—1370
(2002).
2) Sirish M., Chertkov V. A., Schneider H.-J., Chem. Eur. J., 8, 1181—
1188 (2002).
3) Rosenblatt M. M., Huffman D. L., Wang X., Remmer H. A., Suslick
K. S., J. Am. Chem. Soc., 124, 12394—12395 (2002).
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1627 (2002).
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2368—2380 (2003).
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1211—1213 (2004).
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(2005).
5a,10b-Bis(2-aminophenyl)-15a,20b-bis(2-pivalamidophenyl)por-
phyrin (8) Compound 7 (0.800 g, 0.690 mmol) was dissolved in CH2Cl2
(80 ml) containing triethylamine (1.1 ml). To the solution, pivaloyl chloride
(0.35 ml, 2.8 mmol) was added then stirred for 3 h at room temperature. The
reactant solution was treated with a mixture of dilute HCl (6 mol/l, 10 ml)
and CH3COOH (10 ml) for 1 h at room temperature, deprotecting the two
amino groups. After neutralization with aqueous ammonia in an ice bath, the
organic layer was dried over anhydrous Na2SO4 then evaporated to dryness.
The solid of 8 was purified by silica-gel column chromatography (CHCl3,
1
2.5ꢂ30 cm); yield 0.346 g (59.5%). H-NMR (500 MHz, CDCl3) d ꢃ2.62
(s, 2H, pyrrole–NH), 0.18 (s, 18H, C(CH3)3), 1.55 (s, 4H, NH2), 7.16 (m,
4H, ph), 7.22 (s, 2H, NHCO), 7.51 (t, 2H, ph), 7.62 (t, 2H, ph), 7.80 (t, 2H,
ph), 7.85 (d, 2H, ph), 7.96 (d, 2H, ph), 8.72 (d, 2H, ph), 8.81 (m, 4H, pyr-
role), 8.94 (m, 4H, pyrrole); Vis (CHCl3) lmax 420, 516, 550, 589, 647 nm.
MS m/z 843 ((MꢀH)ꢀ) (Calcd for C54H50N8O2: 842).
5a,10b-Bis(2-aminophenyl)-15a,20b-bis(2-pivalamidophenyl)por- 10) Rakow N. A., Sen A., Janzen M. C., Ponder J. B., Suslick K. S.,
phyrinatozinc(II) (9) Zinc ion was inserted to 8 by a method similar to Angew. Chem. Int. Ed., 44, 4528—4532 (2005).
that of 5, giving 9 as a purple solid. H-NMR (500 MHz, CDCl3) d 0.14 11) Angelini N., Micali N., Mineo P., Scamporrino E., Villari V., Vitalini
(s, 18H, C(CH3)3), 1.56 (s (br), 4H, NH2), 6.75 (s, 2H, NHCO), 7.17 (m, D., J. Phys. Chem. B, 109, 18645—18651 (2005).
4H, ph), 7.52 (m, 4H, ph), 7.77 (d, 2H, ph), 7.83 (t, 2H, ph), 7.98 (d, 2H, 12) Zhou H., Baldini L., Hong J., Wilson A. J., Hamilton A. D., J. Am.
ph), 8.71 (d, 2H, ph), 8.86 (m, 4H, pyrrole), 8.89 (s, 4H, pyrrole); Vis Chem. Soc., 128, 2421—2425 (2006).
(CHCl3) lmax 427, 517 (sh), 556, 595 nm. MS m/z 904 (Mꢀ) (Calcd for 13) Imai H., Munakata H., Takahashi A., Nakagawa S., Ihara Y., Uemori
C54H48N8O2Zn: 904). Y., J. Chem. Soc., Perkin Trans. 2, 1999, 2565—2568 (1999).
1
5a,10b-Bis((2-(N,N-dimethylaminomethylcarbonylamino)phenyl)- 14) “Kagakubinran Kisohen,” 3rd ed., Maruzen, Tokyo, 1984, p. II-339.
15a,20b-bis(2-pivalamidophenyl)porphyrinatozinc(II) (10) This com- 15) Mizutani T., Wada K., Kitagawa S., J. Am. Chem. Soc., 121, 11425—
1
pound was prepared from 9 by a procedure similar to that for 6 from 5. H-
11431 (1999).
NMR (500 MHz, CDCl3) d 0.03 (s, 18H, C(CH3)3), 0.09 (s, 12H, N(CH3)2), 16) Hossain M. A., Schneider H.-J., Chem. Eur. J., 5, 1284—1290 (1999).
1.90 (s (br), 4H, CH2), 6.99 (s, 2H, NHCO), 7.55 (m, 4H, ph), 7.79 (t, 2H, 17) “Lange’s Handbook of Chemistry,” 12th ed., ed. by Dean J. A., Mc-
ph), 7.84 (t, 2H, ph), 8.03 (d, 2H, ph), 8.12 (m, 2H, ph), 8.48 (m, 2H, ph),
Graw-Hill, New York, 1979, pp. 5—19.
8.65 (d, 2H, ph), 8.85 (d, 2H, ph), 8.89 (s, 4H, pyrrole), 8.91 (s, 4H, pyr- 18) It should be noted that the observed d values of –CH3 are an average
role); Vis (CHCl3) lmax 427, 518 (sh), 557, 596 nm. MS m/z 1075 ((MꢀH)ꢀ)
(Calcd for C62H62N10O4Zn: 1074).
5a,10b-Bis((2-(trimethylammoniomethylcarbonylamino)phenyl)-
of the 6 or 12 methyl signals because of their rapid ligand exchange in
the 1H-NMR time scale. Therefore, the net p-current shift of the inter-
acting methyl signal with p system becomes appreciably large.
15a,20b-bis(2-pivalamidophenyl)porphyrinatozinc(II) Chloride (4) 19) Decreases in the binding constant of zinc porphyrin receptors from
This compound was prepared from 10 by a procedure similar to that for 1
H2O to H2O/alcohol mixed solvents have been observed.1,27)
20) Nishio M., Hirota M., Umezawa Y., “The CH/p Interaction, Evidence,
Nature, and Consequences,” Wiley-VHC, New York, 1998.
1
from 6. H-NMR (400 MHz, DMSO-d6) d 0.06 (s, 18H, C(CH3)3), 2.28 (s,
18H, N(CH3)3), 7.37 (s, 2H, NHCO), 7.60 (t, 2H, ph), 7.72 (t, 2H, ph), 7.80
(t, 2H, ph), 7.86 (m, 4H, ph), 8.07 (d, 2H, ph), 8.15 (d, 2H, ph), 8.37 (d, 2H, 21) Nishio M., Cryst. Eng. Comm., 6, 130—158 (2004).
ph), 8.52 (s, 2H, pyrrole), 8.56 (d, 2H, pyrrole), 8.60 (d, 2H, pyrrole), 8.62 22) Imai H., Kyuno E., Inorg. Chem., 29, 2416—2422 (1990).
(s, 2H, pyrrole), 8.94 (s, 2H, NHCO); Vis (H2O/NaHCO3–Na2CO3, pH 10.4) 23) Dougherty D. A., Science, 271, 163—168 (1996).
lmax (log e) 425 (5.36), 520 (sh) (3.38), 558 (4.15), 596 (3.55) nm; Anal. 24) Ma J. C., Dougherty D. A., Chem. Rev., 97, 1303—1324 (1997).
Calcd for C64H68N10O4ZnCl2·5H2O: C, 60.64; H, 6.20; N, 11.05. Found: C, 25) Imai H., Misawa K., Munakata H., Uemori Y., Chem. Lett., 2001,
60.65; H, 6.06; N, 11.00. MS m/z 1141 (Mꢀ) (Calcd for C64H68N10O4ZnCl:
688—689 (2001).
1141).
26) Collman J. P., Brauman J. I., Doxsee K. M., Halbert T. R., Hayes S. E.,
Suslick K. S., J. Am. Chem. Soc., 100, 2761—2766 (1978).
27) Mizutani T., Wada K., Kitagawa S., J. Org. Chem., 65, 6097—6106
(2000).