Preparation of ternary platinum(II) complexes with N-(ω-phenylalkyl)- 1,2-ethanediamine and 2,2′-dipyridine and the effect of the methylene chain length of the N-(ω-phenylalkyl)-1,2-ethanediamine in the complexes on intermolecular interactions with various arylsulfonates

Article abstract of DOI:10.1248/cpb.51.649

A series of ternary complexes comprised of platinum(II), 2,2′-dipyridine, and N-(ω-phenylalkyl)-1,2-ethanediamine was prepared by varying the number (n) of methylene chain carbons between the phenyl group and one of the amino groups of 1,2-ethanediamine. NMR measurements indicated that intramolecular stacking occurred for n=1 and intermolecular stacking occurred for n=3 for several of the aryl sulfonates.

Full text of DOI:10.1248/cpb.51.649

June 2003
Chem. Pharm. Bull. 51(6) 649—653 (2003)
649
w
Preparation of Ternary Platinum(II) Complexes with N-( -Phenylalkyl)-
1,2-ethanediamine and 2,2؅-Dipyridine and the Effect of the Methylene
w
Chain Length of the N-( -Phenylalkyl)-1,2-ethanediamine in the
Complexes on Intermolecular Interactions with Various Arylsulfonates
Masafumi GOTO,* Katsutoshi TANAKA, Masamitsu SUMIMOTO, Hiromasa MORI, and
Hiromasa KUROSAKI
Faculty of Pharmaceutical Sciences, Kumamoto University; Oe-honmachi, Kumamoto 862–0973, Japan.
Received January 17, 2003; accepted March 17, 2003; published online March 27, 2003
A series of ternary complexes comprised of platinum(II), 2,2؅-dipyridine, and N-(w-phenylalkyl)-1,2-ethane-
diamine was prepared by varying the number (n) of methylene chain carbons between the phenyl group and one
of the amino groups of 1,2-ethanediamine. NMR measurements indicated that intramolecular stacking occurred
for n؍1 and intermolecular stacking occurred for n؍3 for several of the aryl sulfonates.
Key words molecular recognition; platinum(II) complex; aromatic-aromatic interaction; aryl sulfonate
propionate-2,2,3,3-d4 (TSP) were purchased from Merck (Darmstadt, Ger-
many). Tetraphenylarsonium chloride was purchased from Dojindo Labora-
tories (Kumamoto, Japan). Sodium naphthalene-1-sulfonate hemihydrate
(Np-1-S), and sodium naphthalene-2-sulfonate (Np-2-S) were obtained from
Nakalai Tesque (Kyoto, Japan). Potassium tetrachloroplatinate(II), 2,2Ј-
Aromatic-aromatic interactions are important in the three
dimensional structures of biomolecules and supra molecules
and such interaction have been investigated in several
fields.1,2) Metal complexes are good candidates for such stud-
ies, because several ligands are assembled by coordination of dipyridine(bpy), sodium perchlorate, nitric acid, 1,2-ethanediamine, sodium
ligand donor atoms to a metal ion.3—6) Platinum(II) com-
plexes are of particular interest, because platinum(II) has a
strong tendency to form a square-planar four-coordinated
benzene sulfonate (BS), dichloromethane, benzene, thionyl chloride, 2-
methyl-2-propanol (tert-BuOH), and disodium anthraquinone-1,5-disul-
fonate (Atq-1,5-DS) were purchased from Wako Pure Chemicals (Osaka,
Japan). These were used as received.
complex and the coordination bonds between the metal ion
and ligand donor atoms are kinetically inert. The latter is the
molecular basis for the action of cisplatin, widely used and
effective antineoplasmic agent.7,8)
In earlier studies, we reported on an NMR study of the in-
tramolecular aromatic-aromatic interactions between the aryl
group and 2,2Ј-dipyridine within (N-benzyl-1,2-ethanedi-
amine)(2,2Ј-dipyridine)platinum(II), [Pt(bpy)(Been)]2ϩ, in
which the equilibrium is shifted toward the syn-form in
D2O.9,10)
[Pt(bpy)Cl2] was prepared according to the method described by Morgan
and Burstall.12) Np-1-S, Np-2-S, Np-1,5-DS were recrystallized from hot
water after treatment with charcoal. Anal. Calcd for NaC10H7SO3·
0.5H2O(Np-1-S): C, 50.21; H, 3.37. Found: C, 49.90; H, 3.36. Anal. Calcd
for NaC10H7SO3(Np-2-S): C, 52.17; H, 3.07. Found: C, 52.21; H, 3.06. Anal.
Calcd for Na2C10H6S2O6·1.5H2O(Np-1,5-DS): C, 33.43; H, 2.52. Found: C,
33.09; H, 2.44.
Preparation of Ligands. 4-Phenylbutyl Chloride and 5-Phenylpentyl
Chloride These compounds were prepared by treatment of the corre-
sponding alcohols with thionyl chloride in dichlomethane. The residues,
after the evaporation of dichloromethane and excess thionyl chloride, were
used in the following procedures.
A number of studies have reported on molecular recogni-
tion based on the stacking of an aromatic guest compound
between the preformed aromatic planes of a host molecule.11)
The synthesis of platinum(II) complexes are relatively
straightforward and can be extended to the preparation of
ethanediamine derivatives with variable methylene chain
lengths. In this study we report on an investigation of the ef-
fect of length between the two aromatic rings on intramolec-
ular stacking. In addition, the possibility that these plat-
inum(II) complexes and aryl sulfonates could form a sand-
wich structure where the aryl sulfonates are held by the aro-
matic ring and 2,2Ј-bipyridine in a platinum(II) complex
were explored.
N-Phenylethyl-1,2-ethanediamine (Peen) Anhydrous 1,2-ethanedi-
amine (42.7 g, 711 mmol) was placed in a 100 ml flask equipped with a re-
flux condenser protected by a calcium chloride drying tube. At 0 °C,
phenethyl chloride (12.5 g, 88.9 mmol) was added dropwise to the 1,2-
ethanediamine with stirring over a 15 min period, followed by the addition of
ethanol (20 ml). The reaction mixture was heated at reflux for 3 h. After
Experimental
Materials N-Benzyl-1,2-ethanediamine (Been), phenethyl chloride, 3-
phenylpropyl bromide, 1,4-dioxane, disodium naphthalene-1,5-disulfonate
sesquihydrate (Np-1,5-DS), disodium naphthalene-2,6-disulfonate (Np-2,6-
DS), disodium naphthalene-2,7-disulfonate (Np-2,7-DS), disodium an-
thraquinone-2,6-disulfonate (Atq-2,6-DS), and disodium anthraquinone-2,7-
disulfonate (Atq-2,7-DS) were purchased from Tokyo Kasei (Tokyo, Japan).
4-Phenyl-1-butanol was purchased from Janssen Chemical. 5-Phenyl-1-pen-
tanol, deuterium oxide, dioxane-d8, chloroform-d were purchased from Fig. 1. Intramolecular Stacking of Aromatic Rings in [Pt(bpy)(Been)]2ϩ
Aldrich (Milwaukee, WI, U.S.A.). Methanol-d4, sodium 3-(trimethylsilyl)- (A) and Intermolecular Stacking between Host and Guest Molecules (B)
* To whom correspondence should be addressed. e-mail: gotomphi@gpo.kumamoto-u.ac.jp
© 2003 Pharmaceutical Society of Japan

650
Vol. 51, No. 6
cooling the reaction mixture, excess 1,2-ethanediamine was removed with a
rotatory evaporator. Into the oily residue, an aqueous concentrated sodium
hydroxide–sodium chloride solution (30 ml) was added and oily layer was
separated and concentrated. The oily residue was distilled under reduced
pressure and the fraction boiling at 116 °C at 7.5 mmHg was collected.
N-(4-Phenylbutyl)-1,2-ethanediamine(2,2؅-dipyridine)platinum(II)
Dichloride Monohydrate, [Pt(bpy)(Pben)]Cl2·H2O (4) A mixture of
[Pt(bpy)Cl2] (0.97 g, 2.29 mmol), Pben·2HCl (0.67 g, 2.52 mmol) and
sodium carbonate (0.73 g, 6.86 mmol) in 10 ml of water was stirred at 80 °C
for 1 h. The black precipitate was removed by filtration and the filtrate con-
centrated to near dryness. The yellow compounds in the residue were dis-
solved in ethanol (6 ml) at 70 °C and the mixture was filtered to remove the
NaCl. The filtrate was allowed to stand in a refrigerator for 2 d. The resulting
yellow crystals were collected on a filter and washed with diethyl ether. The
crude product was recrystallized from water. Yield, 1.08 g (74.6%). Anal.
Calcd for [Pt(C10H8N2)(C12H20N2)]Cl2·H2O: C, 41.77; H, 4.78; N, 8.86.
Found: C, 41.35; H, 4.91; N, 8.87.
1
Yield, 7.20 g (49.3%). H-NMR (CDCl3); d: 7.29 (t, 2H, Jϭ7.4 Hz, m-H),
7.21 (d, 2H, Jϭ7.1 Hz, o-H), 7.20 (t, 1H, Jϭ7.1 Hz, p-H).
N-(3-Phenylpropyl)-1,2-ethanediamine (Ppen) This compound was
prepared according to the method described above using 3-phenylpropyl
bromide instead of phenethyl chloride. Yield, 7.14 g (63.8%). bp
1
133 °C/9.5 mmHg. H-NMR (CDCl3); d: 7.27 (t, 2H, Jϭ7.6 Hz, m-H), 7.19
(d, 2H, Jϭ6.9 Hz, o-H), 7.18 (t, 1H, Jϭ7.3 Hz, p-H).
N-(4-Phenylbutyl)-1,2-ethanediamine Dihydrochloride (Pben·2HCl)
Anhydrous 1,2-ethanediamine (22.4 g, 373 mmol) was placed in a 100 ml
flask equipped with a reflux condenser protected by a calcium chloride dry-
ing tube. At 0 °C, 4-phenylbutyl chloride (6.30 g, 37.3 mmol) was added
dropwise to 1,2-ethanediamine under stirring over a 15 min period, followed
by the addition of ethanol (20 ml). The reaction mixture was heated at reflux
for 5 h. After cooling the reaction mixture, 1,2-ethanediamine dihydrochlo-
ride separated as a white precipitate and the entire mixture was allowed to
stand for 3 d in a refrigerator. The precipitates were removed by filtration
and the filtrate was acidified to Congo red acidic with 1 M hydrochloric acid.
This solution was washed with 30 ml of diethyl ether three times. The hy-
drochloric acid layer was concentrated on a rotatory evaporator. Methanol
was added to the residue and the mixture was heated to reflux. After cooling
the mixture, the separated precipitate was removed by filtration and the fil-
trate was concentrated. The remaining residue was recrystallized from
ethanol. Yield, 4.02 g (44.1%). 1H-NMR (D2O); d: 7.39 (t, 3H, Jϭ8 Hz, o-H,
p-H), 7.31 (dt, 2H, Jϭ7 Hz, m-H). Anal. Calcd for C12H20N2·2HCl: C,
54.34; H, 8.36; N, 10.56. Found: C; 54.06; H, 8.49; N, 10.80.
N-(5-Phenylpentyl)-1,2-ethanediamine Dihydrochloride (Pven·2HCl)
Anhydrous 1,2-ethanediamine (23.4 g, 390 mmol) was placed in a 100 ml
flask equipped with a reflux condenser protected by a calcium chloride dry-
ing tube. After cooling the solution to 0 °C, 5-phenylpentyl chloride (7.02 g,
38.4 mmol) was added dropwise to 1,2-ethanediamine under stirring over a
15 min period, followed by the addition of ethanol (20 ml). The reaction mix-
ture was heated to reflux for 5 h. After cooling the reaction mixture, excess
1,2-ethanediamine was distilled off. The resulting oily residue was treated
N-(5-Phenylpentyl)-1,2-ethanediamine(2,2؅-dipyridine)platinum(II)
Dichloride Monohydrate, [Pt(bpy)(Pven)]Cl2·H2O (5) A mixture of
[Pt(bpy)Cl2] (1.27 g, 3.01 mmol), Pven·2HCl (0.92 g, 3.29 mmol) and
sodium carbonate (0.95 g, 8.46 mmol) in 15 ml of water was stirred at 80 °C
for 1 h. The black precipitate was removed by filtration. The filtrate was con-
centrated to near dryness. The yellow compounds in the residue were dis-
solved in ethanol (8 ml) at 70 °C and the mixture was filtered to remove
NaCl. The filtrate was allowed to stand in a refrigerator for 2 d. The resulting
yellow crystals were collected on a filter and washed with diethyl ether and
the crude product recrystallized from water. Yield, 1.48 g (76.1%). Anal.
Calcd for [Pt(C10H8N2)(C13H22N2)]Cl2·H2O: C, 42.73; H, 4.98; N, 8.67.
Found: C, 42.87; H, 4.68; N, 8.79.
General 1H- and 13C-NMR spectra were recorded on a JEOL JNM-
GX400 and a JEOL JNM-EX270 spectrometer. 1H-NMR measurements
used TSP or tert-butanol (1.25 ppm) as internal standards for D2O and 23%
methanol-d4-deuterium oxide solutions. Chloroform-d solutions were mea-
sured using TMS as an internal standard. 13C-NMR measurements were
done using dioxane as an internal standard (67.4 ppm). The ionic strength
was maintained at Iϭ0.2 M using sodium chloride. Electronic spectra were
recorded with a Shimadzu UV-2200 spectrophotometer. Elemental analysis
were carried out using a Yanaco CHN CORDER at Chemical Instrumental
Analysis Center of Kumamoto University by Mrs. Kuniko Shiraki.
Results and Discussion
N-(w-Phenylalkyl)-1,2-ethanediamines were prepared ac-
with ethanol saturated with hydrogen chloride until Congo red test paper cording to the method described by Linsker and Evans for
gave a blue color. The resulting white precipitate was removed by filtration.
the preparation of N-alkyl-1,2-ethanediamines.13) All the
platinum(II) complexes were prepared by the substitution of
two chloro ligands of [Pt(bpy)Cl2] with 1,2-ethanediamine
The addition of diethyl ether to the filtrate caused the separation of a brown
1
precipitate. This was recrystallized from ethanol. Yield, 4.65 g (54.8%). H-
NMR (D2O); d: 7.38 (t, 2H, Jϭ8 Hz, m-H), 7.31 (dt, 3H, Jϭ7 Hz, o-H, p-
H). Anal. Calcd for C13H22N2·2HCl: C, 55.91; H, 8.66; N, 10.03. Found: C,
56.32; H, 8.85; N, 10.08.
derivatives at elevated temperature and were isolated as chlo-
ride salts. The structures of the platinum(II) complexes are
shown schematically in Fig. 2. The UV spectra of these com-
pounds share a common feature, i.e. two absorption maxima
at 320 and 290 nm and one absorption maxima at around
240 nm. These correspond to the absorption of 2,2Ј-dipyri-
dine.
The effect of the chain length between the phenyl group
and the amine site of 1,2-ethanediamine on intramolecular
stacking was evaluated by the chemical shift of the 2,2Ј-
dipyridine portion of the complex. The chemical shifts of the
Preparation of Pt(II) Complexes. N-Benzyl-1,2-ethanediamine(2,2؅-
dipyridine)platinum(II) Dichloride Tetrahydrate, [Pt(bpy)(Been)]Cl2·
9)
4H2O (1) An aqueous solution of [Pt(bpy)(Been)](NO3)2 was passed
through a Dowex 1-X8 resin(chloride form). The eluted solution was con-
centrated on a rotatory evaporator and the resulting crystals were collected.
Yield, 130 mg (77%). Anal. Calcd for [Pt(C10H8N2)(C9H14N2)]Cl2·4H2O: C,
35.41; H, 4.69; N, 8.69. Found: C, 35.83; H, 4.50; N, 8.62.
N-Phenylethyl-1,2-ethanediamine(2,2؅-dipyridine)platinum(II)
Dichloride Monohydrate, [Pt(bpy)(Peen)]Cl2·H2O (2) A mixture of
[Pt(bpy)Cl2] (1.66 g, 3.93 mmol) and Peen (0.73 g, 4.44 mmol) in 20 ml of
water was stirred at 80 °C for 1 h. Black precipitates were removed by filtra-
tion. The filtrate was concentrated to near dryness. The residue was dis-
solved in ethanol (10 ml) at 70 °C and diethyl ether was added until the solu-
tion became turbid. The mixture was allowed to stand in a refrigerator
overnight. The resulting yellow crystals were collected on a filter and
washed with diethyl ether. Yield, 1.98 g (83.4%). Anal. Calcd for
[Pt(C10H8N2)(C10H16N2)]Cl2·H2O: C, 39.74; H, 4.34; N, 9.27. Found: C,
39.20; H, 4.18; N, 9.27.
N-(3-Phenylpropyl)-1,2-ethanediamine(2,2؅-dipyridine)platinum(II)
Dichloride Dihydrate, [Pt(bpy)(Ppen)]Cl2·2H2O (3)
A mixture of
[Pt(bpy)Cl2] (1.69 g, 4.00 mmol), Ppen (0.79 g, 4.43 mmol) in 10 ml of water
was stirred at 80 °C for 1 h. The black precipitate was removed by filtration
and the filtrate concentrated to near dryness. The residue was dissolved in
water (12 ml) at 80 °C and the mixture was allowed to stand at room temper-
ature overnight. The resulting yellow crystals were collected on a filter
and successively washed with ethanol and diethyl ether. The crude product
was recrystallized from water. Yield, 1.97 g (77.4%). Anal. Calcd for
[Pt(C10H8N2)(C11H18N2)]Cl2·2H2O: C, 39.63; H, 4.75; N, 8.80. Found: C,
38.98; H, 4.71; N, 8.71.
Fig. 2. Schematic Representation of the Platinum(II) Complexes

June 2003
651
plotted against the length of the methylene chains, 1—5. In
the presence of hosts, the 1H signals of the 8-, 5-, 3-positions
of the guest are shifted significantly. These up-field shifts are
dependent on the number of carbon atoms in the methylene
chain and the largest up-field shift is observed for host 3; the
up-field shifts for which are 0.23, 0.25, 0.30 ppm for the 8-,
5-, and 3-positions. In the presence of host 4 or 5, these up-
field shifts are almost the same as those in the presence of en
which have 2,2Ј-dipyridine rings accessible from both sur-
faces. On the other hand, host 1 caused the least up-field
shifts, probably because the intramolecularly stacked phenyl
3,3Ј-, 4,4Ј-, 5,5Ј-, and 6,6Ј-protons of [Pt(bpy)(1,2-ethanedi-
amine)]2ϩ (en) were 8.43, 8.47, 7.81, and 8.64 ppm, respec-
tively. Figure 3 shows the change in the chemical shift of
proton signals of the platinum(II) complexes from those of
en, dϪden. The large up-field shifts observed at position 6
and 5 for complex 1 were caused by the ring current ef-
fect.14,15) As the chain length became longer, this effect be-
came smaller and at chain lengths of 4 and 5, the chemical
shifts for these complexes were nearly equal to those of en.
Thus, an intramolecular p–p aromatic interaction is signifi-
cant in the case of 1.
Intermolecular interactions between these platinum(II)
complexes and several aromatic sulfonates shown in Fig. 4
1
were evaluated. H-NMR spectra of an equimolar (1.6 mM)
mixture of the platinum(II) complex (Host) and sodium aryl
sulfonate (Guest) in 23% CD3OD–D2O were obtained at
30 °C. Figure 5 shows the aromatic region of spectra of a
mixture of Np-2-S and en or platinum(II) complexes, 1—5.
1
The H signals for Np-2-S are assigned as shown at the top
of the Figure based on 1H–1H COSY data. The 1H signals of
the guest were shifted to higher field in the presence of the
host.
1
In Fig. 6, the change in chemical shift for each H signal
of Np-2-S in the presence and absence of hosts, dϪdNp-2-S, is
Fig. 5. Aromatic Region of 1H-NMR Spectra of Equimolar (1.6 mM) Mix-
ture of Pt(II) Complexes and Naphthalene-2-sulfonate in 23% CD3OD–D2O
at 30 °C
Fig. 3. Changes in Chemical Shifts for the 2,2Ј-Dipyridine Portions as a
Fusnction of the Length of Methylene Bridge
3-, ᭿; 3Ј-; ᮀ; 4-; ᭹; 4Ј-, ᭺; 5-, ᭡; 5Ј-, ᭝; 6-, ϫ; 6Ј-, ϩ.
Fig. 6. Change in Chemical Shifts of Naphthalene-2-sulfonate in the Pres-
ence of Equimolar Amounts of Hosts
Fig. 4. Aryl Sulfonates and Their Abbreviations Used in This Study
1-, —᭿—; 3-, —ᮀ—; 4-, —᭹—; 5-, —᭺—; 6-, —᭡—; 7-, —᭝—; 8, —ϫ—.

652
Vol. 51, No. 6
Fig. 7. Change in Chemical Shift of Aromatic Sulfonates in the Presence
of an Equimolar Amount of Host
BS, p-, —᭿—; Np-1-S, 5-, —ᮀ—; Np-2-S, 3-, —᭹—; Np-1,6-DS, 4-, —᭺—; Np-
2,7-DS, 1,8-, —᭡—; Atq-1,5-DS, 3,7-, —ϫ—.
Fig. 8. Change in Chemical Shift of the Dipyridyl Portion of
[Pt(bpy)(Ppen)]Cl2 (3) in Equimolecular Mixture with Several Aromatic
Sulfonates
rings cannot be used for intermolecular stacking. Thus, host
3 would be expected to accept an aryl sulfonate between the
phenyl ring and the dipyridine moiety in the same molecule.
In order to confirm this assumption, the up-field shifts of
several aryl sulfonates were measured, as described above.
The differences in the chemical shifts of guests relative to
those of the guest in the absence of the host were determined.
The largest up-field-shifted signals for each guest are p-, for
BS; 5-, Np-1-S; 3-, for Np-2-S; 4-, Np-1,6-DS; 1,8-, for Np-
2.7-DS; 3,7-, for Atq-1,5-DS. The differences in chemical
shifts are plotted against the chain length in Fig. 7. In each
case, the maximum up-field shift was observed in the case of
host 3. The magnitude of the maximum shifts were depen-
dent on the size of sulfonate aryl group: an increase in size
led to up-field shifts. Both the number of the sulfonyl group
and their position where it is substituted affect the magnitude
of the up-field shift. This suggests that coulombic interac-
tions contribute to some extent, to these host-guest interac-
tions.
3-, ᭿; 3Ј-; ᮀ; 4-; ᭹; 4Ј-, ᭺; 5-, ᭡; 5Ј-, ᭝; 6, ϫ; 6Ј, ϩ.
1
Fig. 9. Change in Chemical Shift of the 3-1H Signal of the Dipyridine Por-
tion of [Pt(bpy)(Ppen)]Cl2 (3) with Varying Concentrations of Several Aro-
matic Sulfonates
The effect of guest on the chemical shifts of H signals of
the bpy ring of host 3, which showed the largest up-field shift
among 1—5, is shown in Fig. 8. The increase in the number
of aromatic ring and sulfonate resulted in an increase in the
up-field shift for host 3. In the case of the Np-2,7-DS, the
BS, —᭿—; Np-1-S, —ᮀ—; Np-2-S, —᭹—; Np-1,5-DS, —᭺—; Np-2,6-DS, —
᭡—; Np-2,7-DS, —᭝—; Atq-1,5-DS, —ϫ—; Atq-2,7-DS, —ϩ—.
1
6Ј-, 6-, 3Ј-, and 3-positioned H showed up-field shifts of
method was then employed to obtain the final values for K
and Ddsat using all the experimental data with Eq. 3. The val-
ues of K and dsat are listed in Table 1.
0.28, 0.31, 0.41, and 0.45 ppm, respectively.
The chemical shifts of two host en and 3, for each of
which the concentration was maintained at 2 mM, were mea-
sured with varying concentrations of guests (0—40 mM) with
Iϭ0.2 M at 30 °C. The up-field shift increased with the con-
centration of guests, reaching a constant limiting value at
higher concentrations. Figure 9 shows, the up-field shift of
K
hostϩguest
host guest
(1)
(2)
1
1
1
ϭ
ϩ
1
the 3-position H signal of the bpy ring of 3 in the presence
Ddobs Ddsat DdsatK[guest]t
of several guest compared to hosts only (Dd3-H). The binding
constant, K, defined by Eq. 1 and the estimated limiting up-
field shift for the host-guest complex, Ddsat, was obtained as
follows.16) First, the primary K values and Ddsat values were
estimated using Eq. 2 and data obtained under conditions of
[guest]totalϾϾ[host]total. Using these primary values, a non-lin-
ear least-squares method using the damping Gauss-Newton
Ddsat
2K[host]t
Ddϭ
{K([host]tϩ[guest]t )ϩ1}
Ddsat
2K[host]t
Ϫ
K2 ([host]tϪ[guest]t )2ϩ2K([host]tϩ[guest]t )ϩ1
(3)

June 2003
653
Table 1. Binding Constants (K) of Hosts en and 3 with Various Aryl Sul-
fonates and Estimated Shifts of the Aromatic 3-H Signal of Hosts in Associ-
demonstrated by the readily available platinum(II) com-
plexes.
ated Species (Ddsat
)
Acknowledgements This study was financially supported in parts by a
Grant-in-Aid for Science Research from the Ministry of Education, Culture,
Sports, Science and Technology of Japan.
Host
en
3
Ϫ1
Ϫ1
References
Guest
K/M
Ddsat/ppm
K/M
Ddsat/ppm
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(1990).
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3337—3339 (1986).
5) Odani A., Masuda H., Yamauchi O., Ishiguro S., Inorg. Chem., 30,
4484—4486 (1991).
BS
Np-1-S
Np-2-S
Np-1,5-DS
Np-2,6-DS
Np-2,7-DS
Atq-1,5-DS
18Ϯ2
42Ϯ1
0.12Ϯ0.01
1.19Ϯ0.03
1.04Ϯ0.03
0.82Ϯ0.03
1.18Ϯ0.03
1.18Ϯ0.02
—
25Ϯ3
79Ϯ5
0.10Ϯ0.01
1.04Ϯ0.04
0.98Ϯ0.02
1.22Ϯ0.06
1.31Ϯ0.03
1.29Ϯ0.04
0.84Ϯ0.03
1.17Ϯ0.03
124Ϯ2
164Ϯ2
251Ϯ3
185Ϯ3
—
169Ϯ1
179Ϯ5
344Ϯ1
185Ϯ5
186Ϯ2
142Ϯ2
Atq-2,7-DS 144Ϯ3
1.12Ϯ0.02
6) Sugimori T., Shibakawa K., Masuda H., Odani A., Yamauchi O., Inorg.
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From these values, 3 acts as a stronger host than en in
binding with most aromatic sulfonates, the binding constant
increases with increasing size of the guest aromatic ring,
disulfonates have a larger binding constant than monosul-
fonates for the naphthalene sulfonates but the position of the
sulfonate group has a considerable effect on this, and the lim-
iting shift in chemical shift is larger for 3 than en but the dif-
ference is not very large.
Several compounds have been reported to act as hosts for
aromatic guests. Kuroda et al. reported that biporphyrins
bind to pyrazine derivatives,17) Kadish et al. reported that co-
facial biscorroles and porphyrin-corroles bind with pyri-
dine.18) These compounds have been extensively explored for
electron-transfer and the activation of small gaseous mole-
cules such as O2, H2, and N2.19) Adams and Whitlock used
[8.8](1,4)benzophanes, [8.8](2,6)- and [8.8](1,4)naph-
thalenophanes to capture naphtalene-2-sulfonate and 8-
anilino-1-naphthalenesulfonic acid.20) The hosts used either
two metal coordinated macrocycles or organic compounds.
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Bolze F., Burdet F., Guilard R., Inorg. Chem., 41, 3990—4005 (2002).
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Ed. Engl., 33, 1537—1554 (1994).
In the present work, ternary mono-metal complexes with 20) Adams S. P., Whitlock H. W., J. Am. Chem. Soc., 104, 1602—1611
(1982).
the two aromatic rings (phenyl and dipyridine) separated by
varying degrees were used and molecular recognition was