A new diaza-18-crown-6 ligand containing two quinolin-8-ylmethyl side arms: Crystal structures and characterization of the ligand, the protonated ligand and its mononuclear Barium(II) and dinuclear copper(II) complexes

Article abstract of DOI:10.1002/jhet.5570380101

A new 7,16-bis(quinolin-8-ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane ligand, L, has been prepared and its crystal structure reported. In addition, the structure of the protonated ligand H₂L has been determined. H₂L is of interest because of interatomic interactions between the ligand and perchlorate ions. The mononuclear Ba(II) (BaL), and dinuclear Cu(II) (Cu₂L) complexes of L have been prepared and their crystal structures determined. Stability constants and other thermodynamic data valid in methanol at 23 or 25° for these and several other complexes of L have been obtained. Among the metal ions studied, L forms the most stable complex with Ba²⁺. In addition, L selectively binds Cu²⁺ over Ni²⁺ by about 3 orders of magnitude. Some of the complexes have been studied using nmr and uv-vis spectroscopic techniques. Crystal data are given for L, space group, P2₁/c, a = 8.8325(14) A, b = 13.808(3) A, c = 13.310(3) A; β = 94.72(2)° Z=2, R = 0.0727; for H₂L, space group, P2₁/c, a = 14.685(3) A, b = 15.035(6) A, c = 17.369(4) A, β = 90.366(12)°, Z = 4, R = 0.0781; for BaL, space group, Pbcn, a = 17.314(3) A, b = 9.539(2) A, c = 22.081(3) A, Z = 4, R = 0.0354; and for Cu₂L, space group, Cc, a = 19.762(2) A, b = 14.413(2) A, c = 14.935(2) A, β = 98.753(12)°, Z = 4, R = 0.0564. Cu²⁺ forms a hydroxo-bridged dinuclear complex with L while Ba²⁺ forms a mononuclear complex with L in which its two side arms are not involved in complexation.

Full text of DOI:10.1002/jhet.5570380101

Jan-Feb 2001
A New Diaza-18-Crown-6 Ligand Containing Two Quinolin-8-
ylmethyl Side Arms: Crystal Structures and Characterization of the
Ligand, the Protonated Ligand and Its Mononuclear Barium(II) and
Dinuclear Copper(II) Complexes
1
N. Kent Dalley*, Guoping Xue, Jerald S. Bradshaw*, Xian Xin Zhang,
Roger G. Harrison, Paul B. Savage, Krzysztof E. Krakowiak [a], and Reed M. Izatt
Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602
a] Current address for K.E.K., IBC Advanced Technologies, Inc., P.O. Box 98, American Fork, UT 84003
Received October 27, 2000
[
A new 7,16-bis(quinolin-8-ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane ligand, L, has been
prepared and its crystal structure reported. In addition, the structure of the protonated ligand H L has been
2
determined. H L is of interest because of interatomic interactions between the ligand and perchlorate ions.
2
The mononuclear Ba(II) (BaL), and dinuclear Cu(II) (Cu L) complexes of L have been prepared and their
2
crystal structures determined. Stability constants and other thermodynamic data valid in methanol at 23 or 25°
for these and several other complexes of L have been obtained. Among the metal ions studied, L forms the
2+
2+
2+
most stable complex with Ba . In addition, L selectively binds Cu over Ni by about 3 orders of magni-
tude. Some of the complexes have been studied using nmr and uv-vis spectroscopic techniques. Crystal data
are given for L, space group, P2 /c, a = 8.8325(14) Å, b = 13.808(3) Å, c = 13.310(3) Å; β = 94.72(2)° Z=2,
1
R = 0.0727; for H L, space group, P2 /c, a = 14.685(3) Å, b = 15.035(6) Å, c = 17.369(4) Å, β = 90.366(12)°,
2
1
Z = 4, R = 0.0781; for BaL, space group, Pbcn, a = 17.314(3) Å, b = 9.539(2) Å, c = 22.081(3) Å, Z = 4, R =
.0354; and for Cu L, space group, Cc, a = 19.762(2) Å, b = 14.413(2) Å, c = 14.935(2) Å, β = 98.753(12)°,
0
2
2+
2+
Z = 4, R = 0.0564. Cu forms a hydroxo-bridged dinuclear complex with L while Ba forms a mononuclear
complex with L in which its two side arms are not involved in complexation.
J. Heterocyclic Chem., 38, 1 (2001).
Introduction.
of ligands: heterotopic ligands capable of simultaneously
binding two different metals in proximity (Figure 1A) and
homotopic ligands which may form homonuclear com-
plexes of metal ions (Figure 1B) [32,33]. In this context,
we have recently reported that o-aminophenol-substituted
diaza-18-crown-6 ligands function as heterobinuclear
The synthesis and complexation properties of macro-
cyclic ligands containing two ligating side arms have
attracted considerable attention in recent years [1-6]. Such
ligands not only form mononuclear cryptates with metal
ions [7,8], but also dinuclear pseudocryptates by inclusion
of two metal ions into the cavity [9-11]. The general ideas
underlying the design of such systems have been pre-
sented, and a number of dimetallic cryptates of different
structural types have been reported [12-13]. Various types
of dinuclear complexes have been obtained with macrocy-
cles containing two chelating subunits such as saturated
macrocycles [14-17] and macrocyclic Schiff-base ligands
2
+
+
receptors for Cu and Na as shown in Figure 1A [34].
[
18-21]. In these complexes, the metal cations are bound
to the chelating units and held by the macrocyclic frame-
work at a distance and in a coordination arrangement that
may allow further binding of a bridging species in a "cas-
cade"-type complexation process [9]. Dinuclear macro-
cyclic complexes containing imidazolato [22-24], azido
Figure 1. A. Heterotopic ligand capable of binding two different metal
ions; B. Homotopic ligand capable of forming homonuclear complexes.
[
25-26], and hydroxo [25-29] bridges have been
described. The interest of these types of complexes lies in
their unusual physical and chemical properties. They can
be used as models of biological dimetallic sites [12,30,31]
and dinuclear catalysts possessing highly selective chemi-
cal reactivity.
Attachment of two side chains to a macrocyclic frame-
work can also yield dinucleating ligands capable of bind-
ing metals both within the macrocyclic cavity and between
the functionalized side arms. This may generate two types
Herein, we report the synthesis and the solid state struc-
ture of a new diaza-18-crown-6 ligand (L) bearing two
quinolin-8-ylmethyl groups as additional donor pendants,
the structure of the protonated ligand with HClO , and the
4
+
+
2+
2+
complexation properties of L with Na , K , Mg , Ba ,
Co , Cu , Ni , and Zn . We also report the crystal
structures of mononuclear BaL(ClO ) , and dinuclear
2+
2+
2+
2+
4
2
[
Cu L(µ-OH)](ClO ) complexes. In the BaL(ClO )
2 4 3 4 2
complex, six donor atoms (N O ) of the diazacrown are
2
4

2
N. K. Dalley, G. Xue, J. S. Bradshaw, X. X. Zhang, R. G. Harrison,
P. B. Savage, K. E. Krakowiak, and R. M. Izatt
Vol. 38
coordinated to barium as well as two bidentate perchlo-
rates and a water molecule, however, the quinoline arms
are not involved in the coordination. This is in contrast to
the Cu L(µ-OH)(ClO ) complex in which three atoms
2
4 3
from the diazacrown and a nitrogen atom from the pendant
2
+
quinoline arms coordinate to each Cu . Also coordinated
to both copper ions is a hydroxide ion which forms a single
2
+
bridge between the two Cu .
Results and Discussion.
Synthesis.
The synthetic route to ligand 7,16-bis(quinolin-8-
ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane L
is depicted in Scheme 1. Intermediate 8-bromomethyl-
quinoline (2) was easily isolated as crystals from ethanol in
an 88% yield after the reaction of 8-methylquinoline (1)
with N-bromosuccinimide in the presence of benzoyl per-
oxide in refluxing carbon tetrachloride. The reaction of
diaza-18-crown-6 with 8-bromomethylquinoline (2) in the
presence of triethylamine as base in anhydrous benzene
gave L in an 87% yield after purification by column chro-
matography on silica gel and recrystallization from methyl-
ene chloride/ethanol.
Complexation Thermodynamics.
Interactions of L with sodium, potassium, magnesium,
barium, cobalt, cupric, nickel, and zinc ions were evaluated
by calorimetric and uv-visible spectrophotometric titrations
[35-37] in an absolute methanol solution. The values of
equilibrium constants (log K) and enthalpy (∆H) and
entropy changes (Τ∆S) for these interactions are listed in
Table 2. With the exception of nickel ions, ligand L forms
stable complexes with the metal ions studied (log K > 3).
Among the metal ions studied, barium forms the most stable
complex with L. L is selctive for barium ions over the other
cations studied by more than two orders of magnitude.
The barium (II) and dinuclear copper (II) complexes of
ligand L were obtained by the reaction of ligand L with
barium perchlorate trihydrate or cupric perchlorate hexa-
hydrate in acetonitrile. We also tried to prepare the ferric
complex of Ligand L by the reaction of L with ferric per-
chlorate perhydrate. The salt obtained from this reaction
was L-(HClO ) -1.5 H O.
4
2
2
Table 1
Crystallographic Data for the Structural Studies
H2L BaL
L
Cu2L
Cu ·µOH(C32H40N O )-
Formula
C32H40N O ·CH Cl
C32H42N O (ClO ) ·CH CN
[Ba(C32H40N O )(H O)](ClO )
4 4 2 4 2
4
4
2
2
4
4
4 2
3
2
4 4
(
ClO ) CH CN
4 3 3
Formula wt
F(000)
629.61
668
786.65
1656
898.42
1824
1028.17
2112
Crystal size, mm
µ, mm-1
Crystal system
Space group
a, Å
b, Å
c, Å
β, °
0.3 x 0.25 x 0.25
0.244
Monoclinic
0.4 x 0.3 x 0.08
0.236
Monoclinic
0.34 x 0.30 x 0.25
1.305
Orthorhombic
0.5 x 0.5 x 0.3
1.281
Monoclinic
P2 /cPn2
1/cPbc
14.685(3)
15.035(6)
17.369(4)
90.366(12)
3835
Cc
1
8.8325(14)
13.808(3)
13.310(3)
94.72(2)
1617.8(5)
2
17.314(3)
9.539(2)
22.081(3)
90.00
3646.8
4
19.762(2)
14.413(2)
14.935(2)
98.753(12)
4204.2
4
Volume, Å3
Z
ρ calc, Mg/m3
4
1.293
1.363
1.637
1.624
2θmax, °
50.00
45.00
50.00
55.00
Independent data
2378 (Rint = 0.0509)
5004 (Rint = 0.0892)
5003/0/479
1.044
3217 (Rint = 0.0263)
3209/0/236
1.048
4927 (Rint = 0.0202)
4922/2/501
1.044
Data/restraints/parameters 2375/0/202
Goodness-of-fit on F2
Final R indices
1.046
R1 = 0.0727
R1 = 0.0781
R1 = 0.0358
R1 = 0.0564
2
2
2
2
wR = 0.1727
wR = 0.1616
wR = 0.0890
wR = 0.1495
-
3
Largest peak, ∆ map, eÅ
Largest hole, ∆ map, eÅ
0.228
-0.510
0.258
-0.256
1.031
-0.736
0.984
-0.482
-3

Jan-Feb 2001
A New Diaza-18-Crown-6 Ligand Containing Two Quinolin-8-ylmethyl Side Arms
3
Ligand L shows selectivity for cupric over nickel ions by
about three orders of magnitude. We first intended to deter-
mine log K for the interaction of nickel ions with L by the
calorimetric method. The very small heat of reaction sug-
gested weak complexation for which the log K value could
not be accurately calculated from the calorimetric data.
Therefore, we used a spectroscopic method [37] to evaluate
the interaction and obtained log K < 1.5 which is consistent
with the calorimetry study. The small log K value for nickel-
L complexation is probably a result of the preorganization
Entropy effects play a major role in the complexation of
magnesium, barium, and cobalt ions (Table 2). The high
stability constant of Ba -L results from both enthalpy and
entropy effects. On the other hand, the formation of mag-
nesium and cobalt complexes is essentially entropy driven.
2
+
X-ray Crystal Structures.
Crystal structures of the ligand L, the protonated ligand
H L and the barium (BaL) and copper (Cu L) complexes
2
2
of L are reported. In some respects, the structures of H2L
and BaL reported are similar to those of two 5-chloro-8-
hydroxyquinoline diaza-18-crown-6 ligands, 3 and 4
8
of the ligand. The nickel ion has a d electronic configura-
tion and is capable of forming square-planar, tetrahedral, or
octahedral complexes. However, the preorganization of the
ligand may place the donor atoms (especially the four nitro-
gens) in positions that cannot match the coordination
(Figure 2), and the Ba-4 complex [7,8]. The three ligands
have the same crown ring and have sidearms containing
quinoline rings attached to the crown ether nitrogen atoms.
However, the quinoline rings of L are attached at the car-
bon in the 8 position while the attachment in 3 and 4 are at
the 7 and 2 positions, respectively. Also, the quinoline rings
in 3 and 4 have a chloride attached at the 5 position and a
hydroxy group at the 8 position while there is no substitu-
tion of the quinoline ring in L. The hydroxy group at the 8
position in 4 provides a good donor atom for complex for-
mation because of its proximity to the nitrogen donor atom.
The two donor atoms provide the possibility of bidentate
sidearms. These structural differences suggest that the
sidearms in L may not play the same role as they did in 4.
2+
requirement of Ni no matter how the ligand adjusts its
conformation during complexation. On the other hand,
2
+
2+
Jahn-Teller effects of the Cu complexes may allow Cu
to bear a greater distortion resulting in a more stable
2
+
2+
Cu -L complex compared to Ni -L.
The calorimetric titration indicated that ligand L forms a
2
+
binuclear complex with cupric ions. (Cu :L) complexes
of both 1:1 and 2:1 (cupric ion to L) are observed while all
other cations studied form only 1:1 complexes. The data in
Table 2 indicate that the thermodynamic quantities for for-
mation of cupric ions-L from cupric ions and L and for
2
+
2+
formation of (Cu ) -L from cupric ions and Cu -L are
2
similar. Most binuclear copper (II) complexes reported are
formed with all-nitrogen-containing macrocyclic ligands
[
38-42], including the binuclear cupric complex with a
tetraazacrown ether containing two 8-hydroxyquinoline
arms reported by our laboratory [43]. To the best of our
2
+
knowledge, (Cu ) -L is the first binuclear copper(II)
2
complex formed with a diaza-18-crown-6 ligand.
Table 2
Thermodynamic Quantities for the Interactions of Macrocyclic
Ligand L with several Metal Ions in Methanol Solution [a]
Cation
log K
∆H
T∆S
+
Figure 2. 5-Chloro-8-hydroxyquinoline-substituted ligands 3 and 4.
Na
K
Mg
Ba
3.73 ± 0.02
4.58 ± 0.03
4.02 ± 0.07
6.73 ± 0.08 [c]
3.21 ± 0.06
4.43 ± 0.04
4.15 ± 0.04
< 1.5
-22.5 ± 0.3
-39.1 ± 0.3
9.9 ± 0.6
-19.4 ± 0.4 [c]
14.4 ± 0.8
-35.7 ± 0.5
-32.8 ± 0.6
-1.2
-13.0
32.8
19.0
32.7
+
2+
2+
Table 3
2+
Co
+
Hydrogen Bond and Short C-H...O Contact Data for H2L
Cu2 (1)[b]
-10.4
-9.11
2+
Cu (2)[b]
D––H . . .
A
H...A(Å) D...A(Å) D C H...A(°) Translation
of A
Ni2
+
2+
Zn
3.66 ± 0.08
N1 H1
N19
2.01
2.51
2.19
2.59
2.59
2.799
3.362
3.333
3.266
3.461
2.710
3.394
134
127
162
171
149
125
171
x, y, z
x, y, z
x, y, z
x+1, y, z
x+1, y, z
x, y, z
[
a] Both ∆H and T∆S values are in kJ/mol. Except for copper(II), all ther-
C9
C9
C3
H9A O51
H9A O54
H3A O52
modynamic parameters are for 1:1 interactions. The log K values for nickel
and zinc interactions were evaluated at 23° by uv- visible spectrophotomet-
ric titrations and other log K values were determined at 25° by calorimetric
C10 H10B O53
N21 H21
C8 H8A O64[a] 2.43
2+
2+
titrations. [b] Thermodynamic parameters for Cu (1) and Cu (2) refer to
N39[a] 1.90
2+
the formation of the 1:1 complex Cu L (from copper(II) and L) and the
:1 complex (Cu2+)2L (from copper(II) and Cu2+L), respectively. [c]
Determined by a competitive calorimetric titration.
x, y, z
2
[a] In molecule B

4
N. K. Dalley, G. Xue, J. S. Bradshaw, X. X. Zhang, R. G. Harrison,
P. B. Savage, K. E. Krakowiak, and R. M. Izatt
Vol. 38
Figure 3. The perchlorate ion sandwiched between two A molecules in the structure of H L. The thermal ellipsoids were drawn at the 25% probability level.
2
Ligand L exists in a planar, extended conformation as
there are no possible intramolecular interactions between
the sidearms and the crown ring. This was not the case in
either 3 or 4 where there are O-H N ring hydrogen
bonds, intramolecular for 3 and intermolecular for 4,
involving the hydroxy group on the sidearms and the
crown ring nitrogen atoms [7,8].
atoms is referred to as molecule A and the molecule con-
taining atoms N21-C40 and symmetry related atoms is
called molecule B. The unit cell also contains a CH CN
3
…
.
molecule which does not interact with either H L molecule.
2
Molecule A is interesting because it interacts with each of
the oxygens of the Cl5 perchlorate ion. This perchlorate ion
is sandwiched between two molecule A ligands which are
related by a translation of one unit cell in the x direction.
The binding of the perchlorate ion is shown in Figure 3. The
In the protonated ligand H L there are intramolecular
2
interactions involving the protonated nitrogen atoms of the
crown ring and the quinoline nitrogen atoms. The H-bond
…
C-H O interactions are also listed in Table 3. These data
…
data are listed in Table 3. H L is more compact than L as the
indicate that only one of the interactions, C9-H9A O54, is
2
side arms are located above and below the crown ether ring
significant. However, the combination of the four inter-
-
(
Figure 3). In this respect, H L is similar to 3 and 4 [7]. The
atomic interactions hold the ClO group in a stationary posi-
2
4
unit cell of H L contains two crystallographically different
but chemically identical molecules. The molecule contain-
ing atoms N1 through C20 and their symmetry related
tion. This is indicated by the relatively small values for the
equivalent isotropic displacement parameters for the per-
chlorate oxygens O51-O54, the average of which are
2
2
0
.081(7)Å . A comparison of this value with a similar value
2
for the oxygen atoms in the Cl6 perchlorate (0.187(46)Å ),
which interacts weakly with molecule A, shows the effect of
these intramolecular and packing forces.
The structure of BaL is shown in Figure 4. This complex
contains a crystallographic 2-fold axis with the barium ion
and a water ligand lying on that axis. The barium ion has a
coordination number of eleven, the same as that found for
2+
barium in the Ba -4 complex [7,8]. A comparison of the
types of donor atoms involved in the coordination in the two
barium complexes shows similarities but also significant dif-
ferences. The coordination of the barium by the crown ring is
similar in both structures with all six donor atoms of the
diaza-18-crown-6 ligand interacting with the cation. Also, a
seventh site occupied by a water ligand is present in both
2+
complexes. However, in the Ba -4 complex, the remaining
four sites are occupied by donor atoms of the two bidentate
sidearms and the result is a structure resembling a cryptand
which results in a very stable complex with a log K of 12.2
Figure 4. The crystal structure of BaL. Hydrogen atoms were omitted for
clarity. The thermal ellipsoids were drawn at the 40% probability level.

Jan-Feb 2001
A New Diaza-18-Crown-6 Ligand Containing Two Quinolin-8-ylmethyl Side Arms
5
[
8]. This is in contrast to the BaL complex in which the
which group I and group II cations lie in the cavity of the
macrocycle and interact electrostatically with the donor
atoms of the ring. The result is an arrangement of the ring
in which the D-C-C-D (D = N or O donor atoms) torsion
angles are approximately 60° while the C-C-D-C torsion
angles are about 180°. However, when two transition
metal ions are bound, the required geometry of the transi-
tion metal ions produces a large change in the conforma-
tion of the ligand. The three atoms, Cu-OH-Cu, are too
large to lie inside the cavity so they sit above the cavity
and the copper ions interact with the donor atoms of the
ring and the sidearms as shown in Figure 5. Each cop-
per(II) is coordinated by two nitrogen atoms (a ring and a
quinoline nitrogen), two ring oxygen atoms and the link-
ing hydroxy oxygen atom. Both copper ions have a square
pyramidal coordination and in each case the base consists
of two nitrogen atoms, one ring oxygen and the hydroxy
oxygen atom. The apical sites are occupied by the second
ring oxygen atoms, O4 for Cu1 and O13 for Cu2. The
bond distances and angles for the coordination of the cop-
per ions are listed in Table 5. The copper-O41 distances
listed in Table 5 establish that the hydroxy oxygen is mid-
way between the two copper atoms.
sidearms are not involved in the complexation of the barium
cation and instead the remaining four coordination sites are
occupied by oxygens from two bidentate perchlorate ligands.
The log K value for the formation of BaL is only 6.2, which is
approximately the same as that for barium with diaza-18-
crown-6 (6.12) [44]. A comparison of the geometry of the
coordination spheres for the two barium complexes indicates
that they are similar. The 18-crown-6 ring forms a nearly pla-
nar arrangement of donor atoms below the barium ion and the
water ligand being considerably below the crown ring. The
2+
sidearm donor atoms in Ba -4 and the perchlorate oxygen
atoms in BaL are above the barium ion. The interatomic dis-
tances (barium-donor atoms) of BaL are listed in Table 4.
Table 4
Interatomic distances (Å) involving barium in BaL
atoms
distances (Å)
Ba - N1ring
Ba - O4ring
Ba - O7ring
Ba – O1AClO4
Ba – O2AClO4
Ba – O5AClO4
3.068(3)
2.853(3)
2.820(3)
3.006(4)
2.928(4)
2.889(6)
-
-
-
The geometry of the three-atom guest of Cu L is similar
2
to that found in other dinuclear copper complexes. In the
The Cu L complex is of interest for a number of rea-
2
3
+
[
Cu L(µ-OH)] ion, the copper-oxygen-copper angle is
sons but it is particularly interesting because the two cop-
per(II) ions are bound by the 18-crown-6 and are linked
by a hydroxy oxygen. The conformation of the crown ring
2
135.7° and the copper-copper interatomic distance is 3.527
Å, both of which are within the ranges reported in similar
complexes. In previously reported copper-hydrory-copper
moieties the angles range from 100 to 146° and the copper-
copper distances range from 2.972 to 3.663 Å [45-46].
in Cu L differs significantly from that of the crown ring
2
in BaL. The conformation of the crown ring in BaL is
similar to that found in other 18-crown-6 complexes in
Figure 5. The crystal structure of Cu L. The perchlorate ions, the acetonitrile molecule, and the hydrogen atoms were omitted for clarity. The thermal
2
ellipsoids were drawn at the 30% probability level.

6
N. K. Dalley, G. Xue, J. S. Bradshaw, X. X. Zhang, R. G. Harrison,
P. B. Savage, K. E. Krakowiak, and R. M. Izatt
Vol. 38
Table 5
interact with the barium ion, which was supported by nmr
and X-ray crystal structural studies.
Selected Interatomic distances (Å) and angles (°) of Cu2L
1H nmr Spectra.
Cu1 - O41
Cu1 - N1
Cu1 - N28
Cu1 - O16
Cu1 - O4
1.903(5)
1.996(6)
2.017(6)
2.010(6)
2.347(6)
Cu2 - O41
Cu2 - N10
Cu2 - N39
Cu2 - O7
1.904(5)
2.000(7)
2.020(6)
2.069(6)
2.368(6)
1H nmr spectra of free and complexed L in perdeuterated
methanol are shown in Figure 7. The presence of barium
does not result in a significant change in quinoline proton
signals (δ = 7.5 - 9.0 ppm), indicating that the quinoline
rings of the ligand are not involved in the binding in the
solution structure as well as in the solid state structure. On
Cu2 - O13
O41 - Cu1 - N1
O41 - Cu1 - O16
O41 - Cu1 - N28
O41 - Cu1 - O4
N1 - Cu1 - O16
N1 - Cu1 - N28
N1 - Cu1 - O47
N28 - Cu1 - O16
N28 - Cu1 - O4
O16 - Cu1 - O4
171.4(3)
89.0(2)
97.4(2)
101.3(2)
82.7(3)
91.2(3)
8.3(3)
164.0(3)
91.3(3)
101.9(3)
O41 - Cu2 - N10
O41 - Cu2 - O7
O41 - Cu2 - N39
O41 - Cu2 - O13
N10 - Cu2 - O7
N10 - Cu2 - N39
N10 - Cu2 - O13
N39 - Cu2 - O7
N39 - Cu2 - O13
O7 - Cu2 - O13
171.3(3)
91.1(2)
98.0(2)
100.2(2)
82.8(3)
90.1(3)
76.2(3)
154.9(3)
91.8(2)
109.7(2)
1
the other hand, large changes in the H nmr spectra of
macrocyclic methylenes (δ = 3.0 - 4.5 ppm) indicate a
strong interaction of the macororing donor atoms of the lig-
and with magnesium and barium ions.
UV-Visible Spectra.
Selected uv-visible spectra of free and metal-ion com-
plexed ligand L in methanol are shown in Figure 6. Ligand
L exhibits two absorption bands originating from the
4
-1
-1
quinoline groups, one at 227 nm (ε = 7.38 x 10 M cm )
3
-1
-1
and the other at 284 nm (ε = 9.51 x 10 M cm ). Upon
addition of metal ions (10 times the ligand concentration)
to the ligand solution, changes in the ligand spectrum are
observed. Among the metal ions studied (magnesium, bar-
ium, copper(II), cobalt, nickel, and zinc) copper(II) causes
the most significant changes and barium the least changes
in the ligand spectrum. In the presence of copper(II), the
intensity of the absorption bands is increased significantly
and the absorption maxima of the ligand at 227 and 284
nm are shifted to 234 and 279 nm, respectively. These
results suggest a different type of binding for copper(II)
from that of the other cations, probably due to the binu-
clear complex. The very small change in the uv spectrum
of the ligand produced by barium was surprising since bar-
ium formed a very stable complex with the ligand. A pos-
sible reason for this is that the two quinoline groups do not
Figure 7. 1H nmr spectra of free ligand L and its Ba2+ and Mg2+
complexes in perdeuteromethanol.
Magnetic Properties of Copper(II) Complexes.
Dinuclear complexes of copper(II) have been studied
extensively due to their interesting magnetic properties
[47]. The copper ions in dinuclear copper compounds can
be coupled antiferromagnetically or ferromagnetically.
Hydroxide bridged dinuclear copper complexes are often
antiferromagnetically coupled [45,46]. The room tempera-
ture solution (acetonitrite and dimethyl sulfoxide) magnetic
3+
moment (µ /Cu) of 1.28 BM for Cu L(µ-OH) indicates
eff
2
antiferromagnetic coupling between the copper ions and
gives an average spin of 0.62 for each copper. These data
indicate that the hydroxo bridged complex is present in the
1
Figure 6. Uv-visible spectra of L (a) and its Ba2+ (b) and Cu2+ (c)
complexes in methanol.
solution as well as the solid state. Due to this coupling, H
3+
nmr signals for Cu L(µ-OH) can be observed [48]. If the
2

Jan-Feb 2001
A New Diaza-18-Crown-6 Ligand Containing Two Quinolin-8-ylmethyl Side Arms
7
3
+
7.65 (dd, 2H), 8.02 (d, 2H), 8.11 (dd, 2H), 8.90 (dd, 2H); 13
nmr: δ 54.78, 54.86, 70.33, 71.00, 120.95, 126.53, 126.74,
solution structure of Cu L(µ-OH) is the same as the solid
C
2
state structure, then half of the protons on the diazacrown
will be nonequivalent while the protons on the quinoline
side arms will be equivalent and a total of 20 different H
nmr signals are expected. Eleven isotropically shifted H
nmr signals are observed for Cu L(µ-OH) : five of which
1
28.36, 129.20, 136.54, 138.23, 147.02, 149.42; hrms: m/z calcd.
+
for C H O N (M+H) : 545.3130, found: 545.3132. Crystals
1
32 41 4 4
of this compound suitable for X-ray analysis were grown by slow
evaporation of a dilute solution with a mixed methylene chlo-
ride:methanol solvent (1:2) at room temperature.
1
3+
2
are sharp (δ = 16.8, 14.7, 12.7, 8.0, and 7.3 ppm), four of
which are broad (δ = 17.0, 14.2, 6.6, and 6.3 ppm), and two
of which are very broad (δ = 41 and 66 ppm). The nine
most upfield signals are narrow enough to be integrated and
all integrate to one with respect to each other. Thus, either
several protons are broadened to the extent that they are not
observed or the structure of the molecule is different in
solution than in the solid state.
Anal. Calcd for C H N O -CH Cl -H O: C, 61.20; H, 6.85.
Found: C, 61.24; H, 6.62.
3
2
40
4
4
2
2
2
Preparation of [Ba(L)](ClO ) -H O.
4
2
2
To L (13.6 mg, 0.025 mmole) dissolved in 1 ml of acetonitrile
was added barium perchlorate trihydrate (9.75 mg, 0.025 mmole)
dissolved in 1 ml of acetonitrile at room temperature. Crystals of the
complex suitable for X-ray analyses were obtained by slow evapo-
ration of this solution at room temperature to give 18.7 mg (85%).
Anal. Calcd for C32H40N O Cl Ba: C, 43.63; H, 4.58.
4
12-
2
EXPERIMENTAL
Found: C, 43.58; H, 4.72.
Preparation of [Cu (L)(OH)](ClO ) .CH CN.
2
4 3
3
The H and 13C nmr spectra were recorded at 300 MHz in
deutereochloroform. Hrms were obtained using the fast atom
bombardment (fab) technique. All solvents were purified by stan-
dard procedures. Starting materials were commercial reagents
and were used without further purification. Reagent grade inor-
ganic chemicals were obtained from the indicated sources and
used without further purification: sodium bromide (Baker),
cupric chloride (Wasatch), magnesium perchlorate (Allied), bar-
ium bromide (Johnson-Matthey), colbalt chloride hexahydrate
1
This dark blue complex was obtained in a similar fashion as for
the above complex except that 2 equivalents of cupric perchlorate
hexahydrate were used instead of the barium salt to give 23.1 mg
(90%) of the complex.
Anal. Calcd for C H O Cl Cu -CH CN: C, 39.72; H, 4.32.
32 41 17
3
2
3
Found: C, 40.10; H, 4.65.
Preparation of L(HClO ) .1.5 H O.
4
2
2
In an attempt to prepare the ferric complex of L,13.6 mg
0.025 mmole) of L was dissolved in 1 ml of acetonitrile and 8.86
(
(
Fisher), cupric chloride (Aldrich), nickel nitrate hexahydrate
Baker), and zinc chloride (Mallinckrodt AR).
(
mg (0.025 mmole) of ferric perchlorate perhydrate dissolved in 1
ml of acetonitrile was added at room temperature. Crystals of the
salt L(HClO4)2.CH3CN suitable for X-ray analysis were
obtained by slow evaporation of this solution at room tempera-
ture. Caution! The perchlorate salts must be handled with care as
they are potential explosives.
Preparation of 8-Bromomethylquinoline (2) (Scheme 1).
-Bromomethylquinoline was prepared in a manner similar to
8
that described by Kimura et.al [49]. A solution of 8-methylquino-
line (1) (12.6 g, 88 mmoles) in 400 ml of carbon tetrachloride
was refluxed with N-bromosuccinimide (16.0 g, 90 mmoles) in
the presence of benzoyl peroxide (0.7 g) for 12 hours. The hot
solution was filtered and the brown filtrate was evaporated under
reduced pressure. The residue was dissolved in 50 ml of chloro-
form, and the solution was washed twice with saturated aqueous
sodium carbonate and once with water. The organic phase was
dried over anhydrous sodium sulfate and evaporated. The residue
was recrystallized from ethanol to give 17.2 g (88%) of 2 as
white crystals. The mp and nmr spectral data were identical to
those reported [49].
Anal. Calcd for C32H40N4O4-2 HClO4-1.5 H2O: C, 49.74; H,
5.87. Found: C, 49.65; H, 5.69.
Preparation of Mg-L.
The Mg-L complex was formed by mixing magnesium
perchlorate with L in perdeuterated methanol in an nmr tube.
Calorimetric Measurements.
Values of log K, ∆H, and Τ∆S for the interactions of metal ions
(except nickel and zinc ions) with L were determined as described
7
,16-Bis(quinolin-8-ylmethyl)-1,4,10,13-tetroxa-7,16-diazacy-
earlier [35] in absolute methanol solutions at 25.0 ± 0.1° by titra-
tion calorimetry using a Tronac Model 450 calorimeter equipped
with a 20 ml reaction vessel. The metal ion solutions were titrated
into the macrocyclic ligand solutions and the titrations were car-
ried out to a 2-fold excess of metal ions. In general, concentrations
clooctadecane (L) (Scheme 1).
A solution of 2 (2.0 g, 9.0 mmoles) in 50 ml of benzene was
added dropwise to a solution of diaza-18-crown-6 (1.0 g, 3.8
mmoles) and triethylamine (1.6 g, 15.8 mmoles) in 50 ml of ben-
zene under nitrogen. The mixture was stirred at room temperature
for 20 hours and then refluxed for 2 hours. The solvent was evap-
orated under reduced pressure. The residue was treated with a
mixture of water and chloroform (1:2). The organic layer was
separated, washed with water, and dried over anhydrous sodium
sulfate. After evaporation, the residue was purified by column
chromatography on silica gel with acetone as eluent. The product
-3
of the ligands were 2.2 - 3.2 x 10 M and those of the metal ions
7.5 x 10- M - 0.1 M. In the case of cupric ion, the concentration of
2
the ligand was 1.5 x 10- M and that of cupric ion, 5.1 x 10 M.
After a 2:1 (cupric ion:L) complex was observed, the cupric ion
concentration was increased to 0.11 M. The method used to
process the calorimetric data and to calculate the log K and ∆H
values has been described [36]. Calorimetric titrations showed no
detectable heat for the nickel ion-L interaction and a white precip-
3
-2
was recrystallized from methylene chloride/ethanol to give 1.81 g
1
-3
(
87%) of L as yellow crystals, mp 95-96°; H nmr: δ 2.93. (t,
itate was observed when the ligand (1.5 - 2.1 x 10 M) was
8H), 3.66 (m, 16H), 4.43 (S, 4H), 7.36 (dd, 2H), 7.52 (d, 2H),
titrated with zinc ion. Therefore, log K values for nickel and zinc

8
N. K. Dalley, G. Xue, J. S. Bradshaw, X. X. Zhang, R. G. Harrison,
P. B. Savage, K. E. Krakowiak, and R. M. Izatt
Vol. 38
ion interactions were evaluated by a uv-visible spectrophotomet-
ric method.
the H L and Cu L compounds and the hydrogen atoms bonded
2 2
to C17 and C17' and to the neighboring carbon C18 in the copper
complex. The riding model was used for the refinement of all
hydrogen atoms. All programs used in the solution, refinement
and display of these structures are contained in the SHELXTL
PC [52] program package.
Uv-Visible Spectral Measurements.
Uv-visible spectra were recorded at 23 ± 1° in a 1-cm quartz
cell by using a Hewlett-Packard 8453 spectrophotometer.
Absolute methanol was used as the solvent. For the determination
Acknowledgment.
-5
of stability constants, a 5.0 x 10 M L solution (2.50 mL) was
titrated by nickel or zinc ion solutions and the uv-visible spectra
were recorded after each titration. The method described by
Bourson and Valeur [37] was employed to calculate log K values.
Absorbance data at 280 and 284 nm were used to make the calcu-
lations for L-zinc and L-nickel interactions, respectively. Since
nickel nitrate showed a weak absorption at 284 nm in methanol
The authors thank the Office of Naval Research for financial
support and Ning Su for his helpful advice.
Supplementary Material.
Atomic coordinates, displacement parameters, bond lengths
and angles have been deposited at the Cambridge
Crystallographic Centre.
-1
-1
solution (ε = 10.9 M cm ), the values of ligand absorbance were
corrected by subtracting the nickel absorption.
1H nmr Spectral Measurements.
REFERENCES AND NOTES
1H nmr spectra of free and complexed L were recorded using a
Varian Unity INOVA 300 (300 MHz) spectrometer at 25° in
perdeuterated methanol. Tetramethylsilane (TMS) was used as
the internal standard. The concentration of L was 5 x 10- M and
[
1] R. M. Izatt, K. Pawlek, J. S. Bradshaw, and R. L. Bruening,
Chem. Rev., 91, 1721 (1991).
2] R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J. D. Lamb, J. J.
[
3
Christensen, and D. Sen, Chem. Rev., 85, 271 (1985).
[3] R. M. Izatt, K. Pawlak, J. S. Bradshaw, and R. L. Bruening,
Chem. Rev., 95, 2529 (1995).
1
those of the metal ions were 6 times that of the ligand. H nmr
measurements of Cu L (µ-OH)(ClO ) were recorded in acetoni-
2
4 3
trile-d and referenced to residual solvent (δ = 1.98 ppm).
Solution magnetic susceptibility measurements were done with
the Evans susceptibility method [50,51].
[4] G. W. Gokel, J. E. Trafton, Cation Binding by
Macrocycles; Y. Inoue and G. W. Gokel, Eds.; Marcel Dekker: New
York, 1990.
3
[5] G. W. Gokel, Chem. Soc. Rev., 21, 39 (1992).
X-ray Structure Determinations.
[6] G. W. Gokel, Inclusion Compounds; J. L. Atwood, J. E. D.
.
The crystal data and some experimental details for L CH Cl
Davies and D. D. MacNicol, Eds.; Oxford University Press: Oxford,
991.
2
2
1
(
L), H L(ClO ) -CH CN (H L), [BaL(H O)(ClO ) ] (BaL), and
2 4 2 3 2 2 4 2
[
7] A. V. Bordunov, J. S. Bradshaw, X. X Zhang, N. K. Dalley,
X.-L. Kou, and R. M. Izatt, Inorg. Chem., 35, 7229 (1996).
8] X. X. Zhang, A. V. Bordunov, J. S. Bradshaw, N. K. Dalley,
X.-L. Kou, and R. M. Izatt, J. Am. Chem. Soc., 117, 11507 (1995).
9] J.-M. Lehn, Pure Appl. Chem., 52, 2441 (1980).
10] K. P. Wainwright, Coord. Chem. Rev., 166, 35 (1997).
11] D. R. Smith, Coord. Chem. Rev., 172, 457 (1998).
12] L. F. Lindoy, The Chemistry of Macrocyclic Ligands;
Cambridge University Press: Cambridge, U.K., 1989.
13] P. Zanello, S. Tamburini, P. A Vigato, and G. A.
Cu (µ-OH)L]-CH CN (Cu L) are listed in Table 1. The intensity
2
3
2
data for the four structures were collected using a Bruker P4 auto-
mated diffractometer which utilized ΜοΚα radiation (λ= 0.71073
Å). Additional crystal data and experimental details are contained
in the supplementary material. The four structures were solved
using direct methods followed by Fourier methods to complete the
[
[
[
[
[
structures. The ligand L in both L and H L lies about a center of
2
inversion. In the protonated ligand there are two crystallographi-
cally independent molecules in the unit cell so its asymmetric unit
consists of two half molecules. The barium complex contains a
crystallographic two-fold axis with the barium ion and water lig-
and oxygen atom (O5A) lying on the axis. The copper complex
does not contain crystallographic symmetry though it does contain
a pseudo two-fold axis. There is disorder in the copper complex
involving atoms in the region of C17 but it was only possible to
resolve the disorder for C17.
All nonhydrogen atoms in the four structures except the per-
chlorate oxygen atoms of the copper complex were refined
anisotropically. These oxygen atoms were disordered as indicated
by their large isotropic thermal parameters. The carbon atom of
the methylene chloride in L was disordered across a center of
inversion but it was possible to refine the two partial atoms
anisotropically. Positions for all hydrogen atoms were calculated
with the exception of the hydrogen atoms bonded to C9 in L,
[
Mazzocchin, Coordination Chem. Rev., 77, 165 (1987).
[14] K. Travis and D. H. Busch, J. Chem. Soc., Chem.
Commun., 1042 (1970).
[15] G. R. Newkome, D. K. Kohli, F. R. Fronczek, B. J. Hales,
E. E. Case, and G. Chiari, J. Am. Chem. Soc., 120, 7608 (1980).
[16] S. J. Brundenell, L. Spiccia, and E. R. T. Tiekiwk, Inorg.
Chem., 35, 1974 (1996).
[17] Q. Lu, J. J. Reibenspies, A. E. Martell, and R. J. Motekaitis,
Inorg. Chem., 35, 2630 (1996).
[18] S. M. Nelson, Pure Appl. Chem., 52, 2461 (1980).
[19] U. Casellato, P. A. Vigato, D. E. Fenton, and M. Vidali,
Chem. Soc. Rev., 8, 199 (1979).
20] R. Menif, A. E. Martell, P. J. Squattrito, and A. Clearfield,
Inorg. Chem., 29, 4723 (1990).
21] H. Adams, M. R. J. Elsegood, D. E. Fenton, S. L. Heath,
[
[
and S. J. Ryan, J. Chem. Soc., Dalton Trans., 2031 (1999).
[22] P. K. Coughlin, J. C. Dewan, S. J. Lippard, E. Watanabe,
and J.-M. Lehn, J. Am. Chem. Soc., 101, 265 (1979).
H L, and BaL, the hydrogen atoms of the acetonitrile ligands in
2
H L and Cu L, the water hydrogens in the barium complex and
2
2
the hydroxy hydrogen and the hydrogens bonded to C17, C17'
and C18 of the copper complex. It was possible to obtain posi-
tions for all of these hydrogen atoms using difference maps with
the exception of the hydrogen atoms of the acetonitrile ligands in
[
23] M. G. B. Drew, C. Cairns, A. Lavery, and S. M. Nelson, J.
Chem. Soc., Chem. Commun., 1122 (1980).
[24] P. K. Coughlin, S. J. Lippard, A. E. Martin, and J. E.
Bulkowski, J. Am. Chem. Soc.,102, 7616 (1980).

Jan-Feb 2001
A New Diaza-18-Crown-6 Ligand Containing Two Quinolin-8-ylmethyl Side Arms
9
[25] M. G. B. Drew, M. McCann, and S. M. Nelson, J. Chem.
Reedijk, and A. L. Spek, Inorg. Chem., 38, 1239 (1999).
Soc., Chem. Commun., 481 (1979).
[39] M. B. Inoue, E. F. Valazquez, A. Ruiz-Lucero, M. Inoue, A.
Raitsimring, and Q Fernando,Inorg. Chem., 38, 834 (1999).
[40] T. F. Pauwels, W. Lippens, P. W. Smet, G. G. Herman, and
A. M. Goeminne, Polyhedron 18, 1029 (1999).
[41] P. Dapporto, V. Fusi, M. Micheloni, P. Palma, P. Paoli, and
R. Pontellini, Inorg. Chim. Acta, 275-276, 168 (1998).
[42] A. Bencini, A. Bianchi, S. Brazzini, V. Fusi, C. Biorgi, P.
Paoletti, and B. Valtancoli, Inorg. Chim. Acta, 273, 326 (1998).
[43] Z. Yang, J. S. Bradshaw, X. X Zhang, P. B. Savage, K. E.
Krakowiak, N. K. Dalley, N. Su, R. T. Bronson, and R. M. Izatt, J.
Org. Chem., 64, 3162 (1999).
[44] H.-J. Buschman, J. Solution Chem., 15, 453 (1989).
[45] E. Spodine, J. Manzur, M. T. Garland, M. Kiwi, O. Pena,
D. Grandjean, and L. Toupet, J. Chem. Soc., Dalton Trans., 365
(1991) and references therein.
[46] I. Castro, J. Faus, M. Julve, and F. Lloret, J. Chem. Soc.,
Dalton Trans., 2207 (1990) and references therein.
[47] K. D. Karlin and J. Zubieta, Eds.; Biological and Inorganic
Chemistry of Copper; Adenine: Guilderland, NY, 1986; Vol. II.
[48] J. M. Brink, R. A. Rose, and R. C. Holz, Inorg. Chem., 35,
2878 (1996).
[49] X. H. Bu, D. L. An Y.T. Chen, M. Shionoya, and E.
Kimura, J. Chem. Soc., Dalton Trans., 2289 (1995).
[50] S. Hilty, B. Webb, R. B. Frankel, and G. D. Watt, J. Inorg.
Biochem., 56, 173 (1994).
[
26] Y. Agnus, R. Louis, and R. Weiss, J. Am. Chem. Soc., 101,
381 (1979).
27] J.-M. Lehn, S. H. Pine, E. Watanable, and A. K. Willard, J.
Am. Chem. Soc., 99, 6766 (1977).
28] P. L, Burk, J. A. Osborn, M. T. Youinou, Y. Agnus, R.
Louis, and R. Weiss, J. Am. Chem. Soc., 103, 1273 (1981).
29] P. K. Coughlin and S. J. Lippard, J. Am. Chem. Soc., 103,
328 (1981).
30] S. J. Lippard and J. M. Berg, Principles of Bioinorganic
Chemistry: University Science Books: Mill Valley, CA, 1994.
31a] J. A. Fee, Struct. Bonding (Berlin), 23, 1 (1975); [b] R.
Malkin and B.G. Malmstrom, Adv. Enzymol., 33, 177 (1970).
32] B. A. Boyce, A. Carroy, J.-M. Lehn, and D. Parker, J.
Chem. Soc., Chem. Commun., 1546 (1984).
33] A. Carroy, C. R. Langick, J.-M. Lehn, K. E. Matthes, and
D. Parker, Helv. Chim. Acta, 69, 580 (1986).
34] N. Su, J. S. Bradshaw, X. X. Zhang, P. B. Savage, K. E.
Krakowiak, and R. M. Izatt, J. Org. Chem., 64, 3825 (1999).
35a] J. L. Oscarson and R. M. Izatt, Determination of
3
[
[
[
3
[
[
[
[
[
[
Thermodynamic Properties In Physical Methods of Chemistry. Vol.
VI; B. W. Rossiter and R. C. Baetzold, Eds; John Wiley & Sons: New
York, 1992; Chapter 7. [b] R. M. Izatt, X. X. Zhang, H. Y. An, C. Y.
Zhu, and J. S. Bradshaw, Inorg. Chem., 33, 1007 (1994).
[36] D. J. Eatough, J. J. Christensen, and R. M. Izatt,
Thermochim. Acta, 3, 219 and 233 (1972).
[51] D. F. Evans, J. Chem. Soc., 2003 (1959).
[
37] J. Bourson and B. Valeur, J. Phys. Chem., 93, 3871 (1989).
[52] G. M. Sheldrick, SHELXTL PC version 5.03, Bruker
Analytical X-ray Systems: Madison, WI. 1994.
[38] R. H. Bode, J. E. Bol, W. L. Drissen, F. B. Hulsbergen, J.