Supramolecular assembly of carbohydrate-functionalized salphen-metal complexes

Article abstract of DOI:10.1002/chem.200902031

Metallosalphen complexes with peripheral glucose and galactose substitueras were synthesized and characterized. Their self-assembled supramolecular structures were then studied with transmission electron microscopy (TEM), scanning electron microscopy (SEM

Full text of DOI:10.1002/chem.200902031

DOI: 10.1002/chem.200902031
Supramolecular Assembly of Carbohydrate-Functionalized
Salphen–Metal Complexes
Joseph K.-H. Hui,[a] Zhen Yu,[a] Tissaphern Mirfakhrai,[b] and Mark J. MacLachlan*[a]
Abstract: Metallosalphen complexes with peripheral glucose and galactose sub-
stituents were synthesized and characterized. Their self-assembled supramolecular
structures were then studied with transmission electron microscopy (TEM), scan-
ning electron microscopy (SEM) and atomic force microscopy (AFM). It was
found that all of the complexes displayed aggregation in the solid-state. Zinc–sal-
phen complexes showed a remarkably homogeneous helical nanofibrillar morphol-
ogy, whereas the other metal complexes only displayed micron-sized clusters.
Keywords: carbohydrates · helical
structures · salphen · supramolec-
ular chemistry · zinc
Introduction
perstructures.[7] Macrocycles such as calix[4]resorcarenes
and cucurbiturils may be functionalized with oligosaccha-
Supramolecular self-assembly of molecules and macromole-
cules into one-dimensional long-range-ordered nanofibers
through non-covalent interactions, such as hydrogen-bond-
ing and intermolecular p–p stacking,[1] has received a lot of
attention in the recent years. The molecule-based construc-
tion approach to fibrous nanostructures provides a way to
diversify the properties of the aggregates by tuning the func-
tionalities of the building blocks. Nanofibers are an exciting
class of materials as these supramolecular aggregates have
useful applications in nanosized electronic,[2] mechanical[3]
and medical fields.[4]
The hydrogen-bonding ability of carbohydrates may be
used to aggregate supramolecular complexes.[5] For instance,
Shinkai and co-workers reported a library of low-molecular
weight monosaccharide gelators that exhibit fibrous aggre-
gates.[6] They also found that peripheral carbohydrates on
porphyrins can help in the formation of stable xerogels,
which can then be used as the templates for helical silica su-
ACHTUNGTRENrNUGN ides to give macrocyclic glycoclusters and porous aggre-
gates.[8] These new supramolecular structures with biocom-
patible carbohydrate surfaces are attractive for drug delivery
agents.
Metal–salen and metal–salphen derivatives have been
studied extensively for their use in catalysis,[9] for oxygen
storage/release,[10] and for chemical sensing.[11] More recent-
ly, the supramolecular organization of metal–salphen com-
plexes has proven a promising route to new materials.[12] It
is surprising that few carbohydrate-functionalized salen de-
rivatives have been reported thus far and none have been
investigated for supramolecular assembly. Nevertheless,
there has been a great deal of research devoted to the func-
tionalization of coordination complexes with carbohydrates.
These substances combine the advantages of the metal com-
plexes, such as catalysis, with the favorable properties of the
carbohydrates—water solubility, hydrogen-bonding, and spe-
cific recognition capabilities—to produce molecules with
new function. The enantiomeric purity of natural carbohy-
drates renders them particularly useful for developing metal
complexes for asymmetric catalysis.[13] For example, MnIII
salen complexes with chiral carbohydrate groups demon-
strate good enantioselectivity for asymmetric epoxidation of
non-functionalized olefins.[14] Orvig and co-workers have in-
vestigated salen-based ligands with glucose attached as
metal-chelating agents for treating Alzheimerꢀs disease.[15]
We have been interested in the supramolecular assembly
of Schiff base macrocycles based on salphen.[16,17] With the
notion that hydrogen bonding between monosaccharides
could facilitate supramolecular assembly of salphen com-
[a] J. K.-H. Hui, Z. Yu, Prof. Dr. M. J. MacLachlan
Department of Chemistry, University of British Columbia
2036 Main Mall, Vancouver, BC V6T 1Z1 (Canada)
Fax : (+1)604-822-2847
E-mail: mmaclach@chem.ubc.ca
[b] T. Mirfakhrai
Department of Electrical and Computer Engineering and
Advanced Materials and Process Engineering Laboratory
University of British Columbia, 2355 East Mall
Vancouver, BC V6T 1Z4 (Canada)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902031.
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FULL PAPER
plexes or macrocycles, we set out to prepare new Schiff base
complexes with appended glucosyl or galactosyl groups. In a
recent communication, we showed that carbohydrate-func-
tionalized salphen compounds complexed to zinc form
supramolecular structures that could be imaged by transmis-
sion electron microscopy (TEM).[18] Here we report our
studies of the synthesis, characterization, and supramolec-
ular assembly of monosaccharide-functionalized salphen
complexes 1a–e and 2a–e. We have found that zinc–salphen
complexes undergo supramolecular assembly into one-di-
mensional helical nanofibers and that other metals lead only
to poorly-defined aggregates.
sis in the presence of silver(I) oxide, having an equatorial
acetyl protecting group at C2 position of the glycopyranosyl
bromide 6 would induce the formation of a b-anomeric
product.[19] To confirm that the carbohydrate moieties have
b-anomeric centers, we undertook a single crystal X-ray dif-
fraction study of the acetyl-protected galactose-functional-
ized dinitrobenzene 5b.[20] The solid-state structure of the
compound (see Figure 1) verified that the two galactosyl
components have b-anomeric centers. The galactose moiet-
ies retain the chair conformation and the compound itself
possesses C2 rotational symmetry. It packs in an orthorhom-
bic lattice, which contains four compound 5b molecules in
each unit cell. The molecules overlap directly on top of each
other along the a axis, but are offset along the c axis. As
they extend along the b axis, the molecule flips in an alter-
nating fashion.
Results and Discussion
With the long term goal of forming Schiff base macrocycles
that are externally functionalized with carbohydrate groups,
we required o-phenylenediamine substituted with carbohy-
drates in the 4,5 positions. These particular compounds were
unknown and, in fact, there are no examples of two carbo-
hydrates attached to ortho positions on the same phenyl
ring; we were uncertain that the compounds could be
formed as they look very sterically crowded. Scheme 1
shows our route to these compounds. Dinitrocatechol (4)
was prepared by a literature procedure then was coupled
with acetyl-protected carbohydrate derivatives 3 by the Koe-
nigs–Knorr reaction. To our surprise, we were able to attach
two carbohydrate moieties ortho to one another on the dini-
trocatechol 4 and obtained compound 3 in 60–70% yield.
According to the literature preparation for glycoside synthe-
Figure 1. a) Top view and b) side view of the crystal structure of acetyl-
protected galactose-functionalized dinitrobenzene 5b. The hydrogen
atoms have been removed for clarity, except the anomeric hydrogen in
the side view to show the b-conformation. The acetyl-protecting groups
are also removed for clarity in the side view. A color version is provided
in the Supporting Information.
The dinitrobenzenes functionalized with acetyl-protected
glucose 5a and galactose 5b were then reduced to yield o-
phenylenediamines 3. We found that the reduction with hy-
drazine using a Pd/C or Raney nickel catalyst, reagents that
worked well to reduce 1,2-dialkoxy-4,5-dinitrobenzenes, re-
sulted in cleavage of some of the acetyl protecting groups as
determined by NMR spectroscopy of the products. The re-
sulting partially-deprotected species prevented isolation of
pure 3. Fortunately, this problem was overcome by using
ammonium formate as the reducing agent. With this proce-
dure, the air-sensitive acetyl-protected carbohydrate-func-
tionalized phenylenediamines 3 were obtained in 70–80%
yield.
After the preparation of phenylenediamines 3 was com-
pleted, they were reacted with salicylaldehyde in situ with
the presence of different metal(II) acetylacetonates under
Scheme 1. Syntheses of dinitrobenzenes 5 and phenylenediamines 3.
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M. J. MacLachlan et al.
nitrogen to obtain metal–salphen complexes
7
and
8
Since carbohydrates are known to facilitate supramolec-
ular assembly, we examined the solid-state structures ob-
tained from the glucose- and galactose-appended metal
complexes. We performed a series of TEM studies by drop-
casting methanol solutions of the metallated carbohydrate
species onto Formvar carbon-coated grids and viewing them
under the electron microscope. Supramolecular structures
were observed and their morphologies are strongly depen-
dent on the metal center being coordinated in the pocket of
the salphen complexes.
(Scheme 2). The acetyl protecting groups on the carbohy-
drate moieties were then cleaved by the use of base (i.e.,
sodium methoxide or triethylamine) in methanol to yield
the target complexes 1 and 2 (Scheme 2).
Representative TEM micrographs of the metal complexes
1a–e and 2a–e are shown in Figure 2. The complexes of
[VO]2+, Fe2+, Ni2+, and Cu2+ all show similar cluster assem-
blies. The petal-like aggregates in each case are microns in
size and most likely are dominated by hydrogen-bonding in-
teractions between the carbohydrate substituents. There is
no apparent difference between the two sets of metal com-
plexes with glucosyl and galactosyl substituents (1–2). Va-
nadyl–salphen complexes are known to form polymeric
structures with the neighboring units through the ···V-O-V-
O··· linking pattern,[21] which would be expected to affect
the supramolecular assembly. However, the observation of
an absorption band at 980 cmÀ1 in the IR spectra for com-
plexes 1a and 2a confirms that the V=O complexes are not
À
coordinated into an extended network (the V O stretch is
observed at 860 cmÀ1 in the case of polymers).[21]
In contrast to the other metal complexes, the zinc com-
plexes display a fibrillar morphology. The discrete nanofib-
ers were found to be microns in length and tens of nanome-
ters in diameter. Clearly, there is a different interaction pro-
Scheme 2. Syntheses of acetyl-protected metal–salphen complexes 7 and
8, and metal–salphen complexes 1 and 2.
The MALDI-TOF or ESI
mass spectra of the complexes
indicated the successful depro-
tection for most of the com-
plexes, but we found that the
deprotection of the acetyl
groups did not go to completion
for some of the metal com-
plexes 7 and 8 (i.e., 7a, 8a, 8b,
and 8d). There was always
Scheme 3. Syntheses of the new phenylenediamines 10.
mono- or diacetyl-protected
complexes still present in the
sample and they could not be
moting the self-assembly in this case. Zinc–salphen com-
plexes are well-known to behave as Lewis acids, and either
coordinate Lewis bases (e.g., pyridine) to the unsaturated
metal centers,[12,17,22] or aggregate whereby the Zn of one
salphen is coordinated to the phenoxy O of another.[23] Di-
merization of the zinc–salphen complexes through this Zn–
O interaction may be responsible for changing the molecu-
lar shape of the molecule sufficiently that it organizes into a
fibrillar structure. Alternatively, the Zn–O interaction may
extend beyond a dimer and yield a polymeric structure with
a (ZnO)n backbone.[18] This Zn–O interaction appears to
dominate over the hydrogen-bonding interactions of the pe-
ripheral glycopyranosyl groups in directing the structure.
easily removed by purification. We therefore developed an-
other route to reach the target glucosyl- and galactosyl–met-
allosalphen complexes (Scheme 3). Compound 5 was first
deacetylated with triethylamine in methanol to yield com-
pound 9, followed by reduction by hydrazine with Pd/C cat-
alyst to obtain the new glycopyranosyl phenylenediamine
10. Metal–salphen complexes 1 and 2 were then synthesized
by reacting compound 10a or 10b with salicylaldehyde and
the corresponding metal salts. This method successfully
overcame the problem of incomplete deprotection, and
MALDI-TOF or ESI mass spectra of the resultant com-
plexes showed only the expected products.
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Salphen–Metal Complexes
FULL PAPER
Figure 3. AFM images of (a–e) glucose-functionalized metal–salphen
complexes 1a–e, respectively. Insets of e) top: a closer look of the rectan-
gular-boxed region; bottom, a histogram of the widths of 100 nanofibers
counted in e).
volution arising from the AFM and sample variation (the
fiber density is greater in the case of the AFM sample).
Closer observation of the fibers reveals that they all have
helical superstructures (Figure 3e inset) and all of the heli-
ces are left-handed. The helical pitches measured by AFM
range from about 30 to 80 nm. A representation of the heli-
cal segment is as shown in Figure 4.
Figure 2. TEM images of (a–e) glucose-functionalized metal–salphen
complexes 1a–e and (f–j) galactose-functionalized metal–salphen com-
plexes 2a-e, respectively.
The helical superstructure of the Zn–salphen molecules is
surprising and not easily explained as the fiber must contain
We also studied the supramolecular structures of salphen
complexes 1 with atomic force microscopy (AFM). Metha-
nol solutions of 1a–e were drop-cast onto individual micro-
scope glass slides and imaged with AFM by scanning with
tapping mode (Figure 3). The AFM micrographs generally
correlate with the morphologies that were observed from
TEM. The [VO]2+, Fe2+, Ni2+, and Cu2+ complexes display
micron-sized clusters with no defining features. On the other
hand, Zn–salphen complex 1e displays well-defined fibers
(Figure 3e). The fibers are mostly straight, and have diame-
ters of 78Æ13 nm (based on a count of 100) and extend for
microns. The size of the fibers is larger than observed from
TEM, and this may be explained by two factors: the tip con-
Figure 4. Graphical representation of the helicity in the fibers of
Zn–salphen 1e.
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M. J. MacLachlan et al.
hundreds of the salphen molecules in diameter. We have
modeled the Zn–O polymer that may form from the Zn–sal-
phen assembly, and this polymer could have a helical struc-
ture. This helical polymer structure may be projected onto
the superstructure morphology we observe. As the sugar
complexes are the only source of chirality in the complex,
they must be responsible for directing the helicity since all
of the helices have the same direction.
plex 8d are much shorter, extending only a few hundreds of
nanometers. Here, the acetyl groups prevent strong interac-
tions between the carbohydrate groups, and the assembly is
likely maintained by stacking of the copper–salphen groups,
known to be nearly flat. No obvious change in the fibril tex-
ture was observed as the gel was diluted in methanol.
Helical fibers have been observed with other carbohy-
drate-based molecules or receptors[24] and other synthetic as-
semblies.[25] Moreover, fibrous aggregates with a helical mor-
phology can be found in biological systems. For instance,
amino acids and sugars can act as supramolecular building
units and direct the assembly of helical nanofibers, such as
collagen, amyloid and keratin.[26]
Conclusions
A series of metal–salphen complexes functionalized with pe-
ripheral carbohydrates and their acetate-protected derivates
has been prepared through two different routes. The use of
carbohydrates facilitates the solid-state clustering of the
metal complexes as determined by TEM and AFM studies.
Surprisingly, the zinc complexes showed a 1D fibrillar as-
sembly that extends over microns in length while the other
metal complexes (copper(II), iron(II), nickel(II), and vanad-
yl) showed a cluster morphology that looks like aggregation
of sheets packed into ball-shaped agglomerates. AFM clear-
ly showed that the zinc complexes organize into helical as-
semblies where the helicity of the fibers is left handed. It is
clear that while the carbohydrates have a role in the supra-
molecular organization of the complexes, the metal has a
surprisingly significant and differential role in directing the
structure. Further study of the aggregation and textures of
the zinc-containing complexes may give useful insight into
biological structures, including zinc-rich plaques implicated
in Alzheimerꢀs disease.
Shinkai and co-workers have reported that carbohydrate
substituents could also be used to promote gelation.[27]
Therefore, we investigated whether such phenomena could
be observed in our metal–salphen complexes that are func-
tionalized with glucose and galactose. Among all complexes
(1–2) and their acetyl derivatives (7–8) that were synthe-
sized, we only noticed gelation occurring for Ni–salphen 7c
and Cu–salphen 8d appended with acetyl-protected glucose
and galactose substituents, respectively. In these cases, the
gels formed when the corresponding methanol solution was
slowly evaporated. Figure 5 shows TEM images of the gels
of complexes 7c and 8d. From the micrographs, we see that
Ni–salphen 7c formed helical bundles (Figure 5a). When
the Ni gel was diluted in methanol and inspected further
with TEM, the morphology, however, changed from helical
bundles to spheres that are linked together (Figure 5b). It is
believed that the intermolecular interaction between the
Ni–salphen was weakened in the diluted sample. Cu–salphen
8d showed a nanofibrillar morphology when viewed under
TEM (Figure 5c). The 1D fibers are similar to those ob-
served for Zn complexes 1e and 2e, but the fibers of com-
Experimental Section
General methods: See Supporting Information.
1,2-Bis(tetra-O-acetyl-b-d-glucopyranosyl)-4,5-dinitrobenzene
(5a):
Tetra-O-acetyl-a-d-glucopyranosyl bromide (6a) (8.42 g, 20.5 mmol) was
dissolved in acetonitrile (150 mL) to give a colorless solution. The solu-
tion was purged with nitrogen for 15 min, then 4,5-dinitrocatechol (4)
(1.65 g, 8.25 mmol) and silver(I) oxide (4.63 g, 20.5 mmol) were added se-
quentially under nitrogen. The resulting mixture, which was very dark in
color, was stirred at 508C for 24 h. After cooling to room temperature,
the mixture was filtered through a thin layer of Celite to obtain a brown-
ish solution. The solvent was removed by rotary evaporation to give a
dark brown solid. Chromatography on silica gel (hexanes/ethyl acetate
1:1), followed by recrystallization in methanol yielded compound 5a
(4.12 g, 58%, colorless plates). M.p. 214–2158C; 1H NMR (300 MHz,
CDCl3): d=7.65 (s, 2H, aromatic CH), 5.29 (m, 2H, CH), 5.21 (m, 4H,
CH), 5.10 (t, 2H, CH), 4.17 (m, 4H, CH), 3.96 (m, 2H, CH), 2.08 (s, 6H,
CH3), 2.07 (s, 6H, CH3), 2.05 (s, 6H, CH3), 2.01 ppm (s, 6H, CH3);
13C NMR (75.5 MHz, CDCl3): d=170.5, 170.0, 169.4, 168.8 (C(O)CH3),
149.1, 138.1, 113.4 (aromatic C), 99.0, 73.0, 72.3, 70.7, 67.9, 62.0 (CH),
20.5, 20.4 ppm (CH3); IR: n˜ = 1754 (m), 1742 (m), 1697 (w), 1600 (w),
1548 (m), 1539 (m), 1511 (m), 1430 (w), 1418 (w), 1375 (m), 1367 (m),
1340 (w), 1294 (m), 1247 (m), 1219 (s), 1212 (s), 1125 (m), 1079 (s), 1034
(s), 968 (m), 922 (m), 895 (m), 870 (m), 816 (m), 761 (w), 754 (w), 725
(w), 701 (w), 682 (w), 665 (w), 644 (w), 601 cmÀ1 (m); UV/Vis (CH2Cl2):
lmax (e)=262 (7.92ꢂ103), 278 nm (7.77ꢂ103 cmÀ1 mÀ1); ESI-MS: m/z:
883.3 [M+Na]+; elemental analysis calcd (%) for 5a (C34H40N2O24): C
47.45, H 4.68, N 3.25; found: C 47.67, H 4.75, N 3.49.
Figure 5. TEM images of the gels of a) acetyl-protected glucose-function-
alized Ni–salphen 7c and b) diluted in methanol; c) acetyl-protected gal-
actose-functionalized Cu–salphen 8d and d) diluted in methanol.
1,2-Bis(tetra-O-acetyl-b-d-galactopyranosyl)-4,5-dinitrobenzene
(5b):
Compound 5b was prepared by the same procedure as for compound 5a.
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Salphen–Metal Complexes
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Chromatography on silica gel (hexanes/ethyl acetate 1:2), followed by re-
Chromatography on silica gel (methylene chloride/ethyl acetate 1:1)
yielded salphen 7a (58%, greenish-yellow solid). M.p. 182–1858C (de-
composition started at 1728C); IR: n˜ =1749 (m), 1608 (m), 1587 (m),
1536 (m), 1509 (m), 1467 (m), 1442 (w), 1373 (m), 1313 (m), 1221 (s),
1193 (m), 1154 (m), 1125 (m), 1068 (s), 1042 (s), 981 (m), 953 (m), 918
(m), 863 (w), 824 (w), 761 (m), 745 (w), 609 cmÀ1 (m); UV/Vis (CH2Cl2):
lmax (e)=246 (4.06ꢂ104), 319 (2.46ꢂ104), 412 nm (2.55ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1074.6 [M+H]+; HR-ESI-MS: m/z: calcd for 8a
(C48H50N2O23V): 1073.2244; found: 1073.2229.
crystallization in methanol yielded compound 5b (66%, colorless nee-
1
dles). M.p. 198–1998C; H NMR (400 MHz, CDCl3): d=7.68 (s, 2H, aro-
matic CH), 5.45 (m, 4H, CH), 5.19 (d, 2H, CH), 5.13 (d, 2H, CH), 4.16
(m, 6H, CH), 2.17 (s, 6H, CH3), 2.09 (s, 6H, CH3), 2.07 (s, 6H, CH3),
2.00 ppm (s, 6H, CH3); 13C NMR (100.6 MHz, CDCl3): d=171.5, 170.9,
169.7 (C(O)CH3), 150.2, 139.1, 114.7 (aromatic C), 100.6, 73.3, 71.5, 69.1,
68.0, 62.9 (CH), 21.6, 21.5, 21.4 ppm (CH3); IR: n˜ =1739 (s), 1597 (w),
1538 (m), 1511 (m), 1431 (w), 1414 (w), 1367 (m), 1360 (m), 1285 (m),
1273 (m), 1248 (m), 1216 (s), 1145 (w), 1125 (m), 1065 (s), 1037 (s), 969
(m), 943 (w), 914 (m), 892 (m), 881 (m), 839 (w), 831 (w), 813 (m), 768
(w), 756 (w), 744 (w), 721 (w), 713 (w), 669 (w), 656 (w), 628 (w),
590 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=314 nm (3.72ꢂ103 cmÀ1 mÀ1);
ESI-MS: m/z: 883.3 [M+Na]+; elemental analysis calcd (%) for 5b
(C34H40N2O24): C 47.45, H 4.68, N 3.25; found: C 47.44, H 4.76, N 3.43.
Glucose-functionalized oxovanadium(IV)–salphen (1a): Salicylaldehyde
(0.040 mL, 0.382 mmol) and vanadyl acetylacetonate (0.069 g,
0.258 mmol) were added to a solution of 4,5-diamino-1,2-bis(b-d-gluco-
pyranosyl)benzene (10a) (0.080 g, 0.172 mmol) in ethanol (22 mL). The
deep brown solution was stirred at 808C for 24 h. After cooling to room
temperature, the product was isolated by precipitation with a mixture of
petroleum ether and methylene chloride, then filtration to yield salphen
1a (0.082 g, 65%, greenish yellow solid). M.p. did not melt at 3008C (de-
composition started at 2328C); IR: n˜ =3346 (m), 2874 (w), 1606 (s), 1584
(s), 1537 (s), 1507 (m), 1469 (m), 1442 (w), 1379 (s), 1337 (w), 1305 (m),
1277 (s), 1222 (w), 1194 (m), 1151 (w), 1094 (m), 1063 (s), 1038 (s), 1028
(s), 1015 (s), 981 (s), 967 (m), 919 (m), 905 (w), 858 (w), 821 (m), 753 (s),
656 (w), 633 (m), 613 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=254 (4.13ꢂ
104), 316 (2.61ꢂ104), 355 (2.01ꢂ104), 412 nm (3.37ꢂ104 cmÀ1 mÀ1); ESI-
MS: m/z: 737.5 [M+H]+, 760.3 [M+Na]+; HR-ESI-MS: m/z: calcd for
1a+Na+ (C32H34N2NaO15V): 760.1297; found: 760.1287.
4,5-Diamino-1,2-bis(tetra-O-acetyl-b-d-glucopyranosyl)benzene
(3a):
Compound 5a (2.30 g, 2.67 mmol) was dissolved in methanol (65 mL)
and the solution was purged with nitrogen for 15 min. Palladium on
carbon (2 spatula tips) and ammonium formate (1.35 g, 21.4 mmol) were
then added to the flask under nitrogen. The resulting mixture was stirred
at 708C for 2 h until the solution became clear and colorless. After cool-
ing to room temperature, the catalyst was removed by filtration through
a Schlenk frit and a colorless filtrate was obtained. The solvent was then
removed under vacuum. Degassed water and chloroform were added to
the flask and the product was extracted into the chloroform under nitro-
gen. Chloroform removal under vacuum yielded air-sensitive compound
3a (1.39 g, 65%, purple solid). This compound was >99% pure
(1H NMR) and was used without further purification. Attempts to
remove colored impurities resulted in further decomposition, so it was
best to purify at the next stage. 1H NMR (400 MHz, CDCl3): d=6.45 (s,
2H, aromatic CH), 5.22 (t, 2H, CH), 5.11 (q, 4H, CH), 5.03 (d, 2H, CH),
4.27 (d, 2H, CH), 4.09 (d, 2H, CH), 3.67 (d, 2H, CH), 3.47 (broad, 4H,
NH2), 2.07 (s, 6H, CH3), 2.04 (s, 6H, CH3), 2.00 (s, 6H, CH3), 1.99 ppm
(s, 6H, CH3); 13C NMR (100.6 MHz, CDCl3): d=170.5, 170.1, 169.3,
169.2 (C(O)CH3), 140.2, 131.1, 109.6 (aromatic C), 100.7, 72.8, 71.9, 71.4,
68.2, 61.6 (CH), 20.6, 20.5, 20.5, 20.4 ppm (CH3); EI-MS: m/z: 800
[M+H]+.
Galactose-functionalized oxovanadium(IV)–salphen (2a): Salphen 2a
(61%, greenish yellow solid) was prepared by the same procedure and
purification as for salphen 1a. M.p. did not melt at 3008C (decomposition
started at 1958C); IR: n˜ =3346 (m), 2874 (w), 1606 (s), 1586 (s), 1537 (s),
1506 (m), 1468 (m), 1440 (w), 1377 (m), 1305 (m), 1277 (m), 1191 (m),
1149 (w), 1064 (s), 1049 (s), 1032 (s), 978 (m), 967 (m), 919 (m), 889 (w),
858 (w), 822 (m), 759 (s), 700 (w), 611 (m) cmÀ1; UV/Vis (DMSO): lmax
(e)=254 (4.13ꢂ104), 309 (2.40ꢂ104), 355 (1.77ꢂ104), 411 (2.85ꢂ104) nm
(cmÀ1 mÀ1); ESI-MS: m/z: 760.0 [M+Na]+; HR-ESI-MS: m/z: calcd for
2a+Na+ (C32H34N2NaO15V): 760.1297; found: 760.1312.
Acetyl-protected glucose-functionalized iron(II)–salphen (7b): Salphen
7b was prepared by the same procedure as for salphen 7a. The product
was purified by chromatography on silica gel. Ethyl acetate was used to
remove impurities, followed by methanol to yield pure salphen 7b (97%,
brown solid). M.p. 162–1658C (decomposition started at 1498C); IR: n˜ =
1748 (s), 1608 (m), 1588 (w), 1535 (w), 1505 (w), 1466 (w), 1438 (w), 1369
(m), 1316 (w), 1217 (s), 1187 (m), 1152 (w), 1065 (m), 1035 (s), 908 (w),
851 (w), 760 (w), 599 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=248 (2.53ꢂ
104), 292 (2.65ꢂ104), 320 (2.13ꢂ104), 414 nm (1.06ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1064.6 [M+H]+; HR-ESI-MS: m/z: calcd for 7b
(C48H50FeN2O22): 1062.2205; found: 1062.2228.
4,5-Diamino-1,2-bis(tetra-O-acetyl-b-d-galactopyranosyl)benzene
(3b):
Compound 3b (83%, greenish solid) was prepared by the same proce-
dure and purification as for compound 3a. This compound was ~90%
pure (1H NMR) and was used without further purification. Attempts to
obtain a pure product resulted in further decomposition, so it was best to
1
purify at the next stage. H NMR (400 MHz, CDCl3): d=6.47 (s, 2H, aro-
matic CH), 5.35 (m, 4H, CH), 5.06 (d, 2H, CH), 4.99 (d, 2H, CH), 4.21
(q, 2H, CH), 4.12 (q, 2H, CH), 3.90 (t, 2H, CH), 3.29 (broad, 4H, NH2),
2.17 (s, 6H, CH3), 2.10 (s, 6H, CH3), 1.99 (s, 6H, CH3), 1.97 ppm (s, 6H,
CH3); 13C NMR (100.6 MHz, CDCl3): d=170.5, 170.4, 170.3, 169.6
(C(O)CH3), 140.9, 131.4, 109.8 (aromatic C), 101.7, 71.2, 71.1, 69.2, 67.4,
61.5 (CH), 21.0, 20.8, 20.7 ppm (CH3); EI-MS: m/z: 800 [M+H]+.
Acetyl-protected galactose-functionalized iron(II)–salphen (8b): Salphen
8b was prepared by the same procedure as for salphen 7a. Chromatogra-
phy on silica gel, first eluted with methylene chloride and ethyl acetate
until the eluent became slight yellow to remove impurities, followed by
flushing with ethyl acetate/acetone 1:1 (brown band). Rotary evaporation
of the brown solution yielded salphen 8b (31%, brown solid). M.p. 194–
1968C (decomposition started at 1768C); IR: n˜ =1747 (s), 1608 (m), 1587
(m), 1534 (m), 1504 (m), 1465 (m), 1445 (w), 1370 (m), 1317 (w), 1298
(w), 1220 (s), 1183 (m), 1151 (m), 1125 (w), 1067 (s), 1041 (s), 953 (w),
916 (m), 900 (w), 850 (w), 839 (w), 819 (w), 759 (m), 741 (w), 711 (w),
629 (w), 599 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=243 (2.41ꢂ104), 296
(3.03ꢂ104), 319 (2.42ꢂ104), 410 nm (1.18ꢂ104 cmÀ1 mÀ1); MALDI-TOF-
MS: m/z: 1062.8 [M+H]+, 2124.9 [2M+H]+; HR-ESI-MS: m/z: calcd for
8b (C48H50FeN2O22): 1062.2205; found: 1062.2208.
Acetyl-protected glucose-functionalized oxovanadium(IV)–salphen (7a):
4,5-Diamino-1,2-bis(tetra-O-acetyl-b-d-glucopyranosyl)benzene
(3a)
(0.150 g, 0.187 mmol) was dissolved in tetrahydrofuran (30 mL) under ni-
trogen. Salicylaldehyde (0.043 mL, 0.421 mmol) and vanadyl acetylaceto-
nate (0.075 g, 0.281 mmol) were then added, giving a green solution. The
solution was stirred at 508C for 24 h. After cooling to room temperature,
petroleum ether was added to the flask to precipitate the crude product
solid, which was isolated by filtration. Chromatography on silica gel
(methylene chloride/ethyl acetate 3:1) yielded salphen 7a (0.091 g, 45%,
yellow solid). M.p. 149–1528C (decomposition started at 1428C); IR: n˜ =
1748 (s), 1608 (m), 1588 (w), 1537 (m), 1507 (m), 1468 (m), 1441 (w),
1376 (m), 1313 (w), 1217 (s), 1154 (m), 1152 (w), 1066 (s), 1036 (s), 981
(m), 919 (m), 909 (m), 859 (w), 823 (m), 760 (m), 744 (w), 610 (m),
600 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=246 (2.76ꢂ104), 319 (1.72ꢂ
104), 411 nm (1.70ꢂ104 cmÀ1 mÀ1); MALDI-TOF-MS: m/z: 1073.9
[M+H]+; HR-ESI-MS: m/z: calcd for 7a+Na+ (C48H50N2NaO23V):
1096.2142; found 1096.2172.
Glucose-functionalized iron(II)–salphen (1b): Triethylamine (30 mL) was
added to a solution of salphen 7b (0.050 g, 0.05 mmol) in methanol
(50 mL). The dark brown solution was stirred at room temperature for
24 h. Methanol and excess triethylamine were then removed by rotary
evaporation to give a brown solid. The crude product was dissolved in
methanol and re-precipitated with petroleum ether, followed by filtration
to yield salphen 1b (0.022 g, 65%, brown solid). M.p. did not melt at
3008C (decomposition started at 1988C); IR: n˜ =3329 (m), 2873 (w),
Acetyl-protected galactose-functionalized oxovanadium(IV)–salphen
(8a): Salphen 8a was prepared by the same procedure as for salphen 7a.
Chem. Eur. J. 2009, 15, 13456 – 13465
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13461

M. J. MacLachlan et al.
1606 (s), 1586 (m), 1536 (m), 1503 (m), 1466 (m), 1440 (m), 1378 (m),
1305 (m), 1278 (m), 1183 (m), 1153 (w), 1065 (s), 1033 (s), 1013 (s), 916
(w), 846 (w), 817 (w), 757 (m), 669 (w), 583 cmÀ1 (m); UV/Vis (DMSO):
lmax (e)=296 (2.98ꢂ104), 344 (2.12ꢂ104), 372 (1.74ꢂ104), 418 nm (1.39ꢂ
104 cmÀ1 mÀ1); MALDI-TOF-MS: m/z: 727.2 [M+H]+, 1453.6 (2m+H)+);
HR-ESI-MS: m/z: calcd for 1b (C32H34FeN2O14): 726.1359; found:
726.1356.
(m), 1289 (m), 1250 (m), 1195 (m), 1187 (m), 1149 (m), 1097 (m), 1063
(s), 1037 (s), 1030 (s), 1015 (s), 990 (s), 959 (m), 920 (m), 904 (w), 886
(w), 863 (w), 848 (w), 825 (w), 759 (m), 738 (m), 656 (w), 629 (m),
587 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=261 (5.30ꢂ104), 294 (2.16ꢂ
104), 380 (3.66ꢂ104), 478 nm (1.29ꢂ104 cmÀ1 mÀ1); MALDI-TOF-MS: m/
z: 729.5 [M+H]+; HR-ESI-MS: m/z: calcd for 1c+Na+
(C32H34N2NaNiO14): 751.1261; found: 751.1248.
Galactose-functionalized nickel(II)–salphen (2c): Salphen 2c (91%, red
solid) was prepared by the same procedure and purification as for sal-
phen 1b. M.p. 241–2438C (decomposition started at 2368C); 1H NMR
(400 MHz, [D6]DMSO): d=8.58 (s, 2H, CH=N), 7.93 (s, 2H, aromatic
CH), 7.52 (d, 2H, aromatic CH), 7.31 (t, 2H, aromatic CH), 6.88 (d, 2H,
aromatic CH), 6.66 (t, 2H, aromatic CH), 5.19 (broad, 2H, CH), 4.94 (d,
6H, CH), 4.62 (broad, 2H, CH), 3.71 (s, 4H, CH), 3.67 (broad, 4H, OH),
3.58 ppm (broad, 4H, OH); 13C NMR (100.6 MHz, [D6]DMSO): d=164.8
(CH=N), 155.2, 147.2, 136.7, 135.0, 134.1, 120.3, 120.2, 115.2, 104.4 (aro-
matic C), 102.1, 76.2, 73.4, 70.4, 68.5, 60.4 ppm (CH); IR: n˜ =3385 (m),
2873 (w), 1609 (s), 1589 (m), 1532 (m), 1506 (m), 1465 (m), 1445 (m),
1373 (m), 1321 (m), 1285 (m), 1250 (w), 1190 (m), 1187 (m), 1147 (m),
1067 (s), 1044 (s), 1028 (s), 957 (m), 920 (m), 893 (w), 825 (w), 756 (s),
702 (w), 601 (m), 569 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=261 (5.43ꢂ
104), 295 (2.19ꢂ104), 380 (3.87ꢂ104), 478 nm (1.36ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 729.1 [M+H]+; HR-ESI-MS: m/z: calcd for 2c+
Na+ (C32H34N2NaNiO14): 751.1261; found: 751.1266.
Galactose-functionalized iron(II)–salphen (2b): Salphen 2b (92%, brown
solid) was prepared by the same procedure and purification as for sal-
phen 1a. M.p. did not melt at 3008C (decomposition started at 2048C);
IR: n˜ =3361 (m), 2873 (w), 1606 (s), 1590 (m), 1537 (m), 1505 (m), 1466
(m), 1444 (m), 1379 (m), 1299 (m), 1279 (m), 1184 (m), 1149 (m), 1067
(s), 1049 (s), 1032 (s), 944 (w), 917 (w), 856 (w), 817 (w), 756 (m), 700
(w), 665 (w), 600 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=296 (3.12ꢂ104),
342 (2.31ꢂ104), 372 (1.96ꢂ104), 417 nm (1.42ꢂ104 cmÀ1 mÀ1); ESI-MS: m/
z: 726.2 [M+H]+; HR-ESI-MS: m/z: calcd for 2b (C32H34FeN2O14):
726.1359; found: 726.1363.
Acetyl-protected glucose-functionalized nickel(II)–salphen (7c): Salphen
7c (88%, red solid) was prepared by the same procedure and purification
as for salphen 7a. M.p. 147–1498C (decomposition started at 1428C);
1H NMR (300 MHz, CD2Cl2): d=8.28 (s, 2H, CH=N), 7.54 (s, 2H, aro-
matic CH), 7.48 (d, 2H, aromatic CH), 7.32 (t, 2H, aromatic CH), 6.99
(d, 2H, aromatic CH), 6.71 (t, 2H, aromatic CH), 5.32 (m, 4H, CH), 5.18
(m, 4H, CH), 4.24 (d, 4H, CH), 3.86 (m, 2H, CH), 2.10 (s, 6H, CH3),
2.03 (s, 6H, CH3), 2.02 (s, 6H, CH3), 2.01 ppm (s, 6H, CH3); 13C NMR
(75.5 MHz, CDCl3): d=170.5, 170.1, 169.4, 169.3 (C(O)CH3), 166.0 (CH=
N), 154.7, 146.2, 138.9, 135.4, 133.5, 121.8, 120.0, 116.2, 106.8 (aromatic
C), 99.8, 72.6, 72.3, 71.3, 68.2, 61.3 (CH), 20.8, 20.7, 20.6, 20.5 ppm; IR:
n˜ =1756 (m), 1611 (m), 1589 (m), 1528 (m), 1508 (m), 1464 (m), 1445
(m), 1371 (m), 1331 (w), 1289 (w), 1244 (s), 1221 (s), 1213 (s), 1188 (m),
1152 (m), 1066 (s), 1036 (s), 985 (w), 958 (w), 920 (w), 909 (w), 825 (w),
758 (m), 741 (w), 599 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=261 (8.79ꢂ
104), 295 (4.67ꢂ104), 381 (6.54ꢂ104), 483 nm (2.22ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1065.4 [M+H]+; HR-ESI-MS: m/z: calcd for
7c+H+ (C48H51N2NiO22): 1065.2287; found: 1065.2299.
Acetyl-protected glucose-functionalized copper(II)–salphen (7d): Sal-
phen 7d (47%, yellow solid) was prepared by the same procedure and
purification as for salphen 7a. M.p. 168–1718C (decomposition started at
1538C); IR: n˜ =1751 (m), 1610 (m), 1590 (m), 1524 (m), 1504 (m), 1463
(m), 1448 (w), 1436 (w), 1375 (m), 1330 (w), 1280 (w), 1214 (s), 1183 (m),
1152 (m), 1117 (w), 1064 (m), 1034 (s), 984 (m), 959 (w), 943 (w), 916
(m), 909 (m), 852 (w), 816 (w), 757 (m), 739 (w), 702 (w), 650 (w), 626
(w), 597 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=245 (5.77ꢂ104), 311
(4.56ꢂ105), 355 (2.84ꢂ104), 407 (3.83ꢂ104), 427 nm (4.27ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1070.4 [M+H]+, 1092.5 [M+Na]+; HR-ESI-MS:
m/z: calcd for 7d+H+ (C48H51CuN2O22): 1070.2229; found: 1070.2219.
Acetyl-protected galactose-functionalized copper(II)–salphen (8d): Sal-
phen 8d was prepared by the same procedure as for salphen 7a. The
product was purified by chromatography on silica gel (ethyl acetate/ace-
tone 9.5:0.5) and yielded salphen 8d (20%, greenish-yellow solid). M.p.
156–1598C (decomposition started at 1448C); IR: n˜ =1747 (m), 1610 (m),
1591 (m), 1526 (m), 1505 (m), 1464 (m), 1448 (m), 1372 (m), 1328 (w),
1301 (w), 1221 (s), 1183 (m), 1153 (m), 1125 (m), 1068 (s), 1041 (s), 953
(m), 902 (m), 855 (w), 816 (w), 758 (m), 740 (m), 712 (w), 653 (w),
599 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=245 (4.06ꢂ104), 312 (3.18ꢂ
105), 357 (2.05ꢂ104), 408 (2.78ꢂ104), 428 nm (3.03ꢂ104 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1070.3 [M+H]+, 1092.4 [M+Na]+; HR-ESI-MS:
m/z: calcd for 8d+H+ (C48H51CuN2O22): 1070.2229; found: 1070.2238.
Acetyl-protected galactose-functionalized nickel(II)–salphen (8c): Sal-
phen 8c (82%, red solid) was prepared by the same procedure and pu-
rification as for salphen 7a. M.p. 186–1888C (decomposition started at
1778C); 1H NMR (400 MHz, CDCl3): d=8.12 (s, 2H, CH=N), 7.44 (s,
2H, aromatic CH), 7.41 (d, 2H, aromatic CH), 7.29 (t, 2H, aromatic
CH), 7.14 (d, 2H, aromatic CH), 6.65 (t, 2H, aromatic CH), 5.45 (m, 4H,
CH), 5.17 (m, 4H, CH), 4.29 (m, 2H, CH), 4.08 (m, 4H, CH), 2.20 (s,
6H, CH3), 2.13 (s, 6H, CH3), 2.01 (s, 6H, CH3), 1.94 ppm (s, 6H, CH3);
13C NMR (100.6 MHz, CD2Cl2): d=170.8, 170.6, 170.5, 169.9 (C(O)CH3),
166.7 (CH=N), 154.8, 147.1, 139.3, 136.1, 134.1, 121.7, 120.6, 116.5, 106.5
(aromatic C), 101.0, 72.2, 71.2, 69.3, 67.7, 62.0 (CH), 21.2, 21.1, 20.0,
20.9 ppm (CH3); IR: n˜ =1747 (s), 1611 (m), 1589 (m), 1524 (m), 1508
(m), 1465 (m), 1445 (m), 1368 (m), 1334 (w), 1215 (s), 1188 (m), 1151
(m), 1126 (m), 1067 (s), 1042 (s), 952 (m), 914 (m), 850 (w), 825 (w), 754
(m), 741 (m), 710 (w), 580 cmÀ1 (m); UV/Vis (CH2Cl2): lmax (e)=261
(2.89ꢂ104), 296 (1.49ꢂ104), 381 (2.20ꢂ104), 483 nm (7.35ꢂ103 cmÀ1 mÀ1);
MALDI-TOF-MS: m/z: 1065.5 [M+H]+; HR-ESI-MS: m/z: calcd for
8c+Na+ (C48H50N2NaNiO22): 1087.2106; found: 1087.2091.
Glucose-functionalized copper(II)–salphen (1d): Salphen 1d (81%,
brownish-yellow solid) was prepared by the same procedure and purifica-
tion as for salphen 1b. M.p. 228–2318C (decomposition started at
2268C); IR: n˜ =3346 (m), 2883 (w), 1610 (s), 1592 (s), 1531 (m), 1507 (s),
1466 (m), 1446 (m), 1436 (m), 1381 (m), 1311 (m), 1281 (m), 1273 (m),
1248 (m), 1220 (w), 1190 (m), 1184 (m), 1150 (m), 1126 (m), 1097 (m),
1070 (s), 1061 (s), 1040 (s), 1030 (s), 994 (s), 947 (m), 917 (m), 890 (w),
870 (w), 852 (w), 817 (w), 765 (s), 756 (m), 738 (m), 660 (w), 629 (m),
582 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=265 (4.64ꢂ104), 302 (3.37ꢂ
104), 312 (3.20ꢂ104), 335 (2.22ꢂ104), 357 (2.35ꢂ104), 418 nm (3.62ꢂ
104 cmÀ1 mÀ1); ESI-MS: m/z: 734.5 [M+H]+, 756.2 [M+Na]+; HR-ESI-
MS: m/z: calcd for 1d+Na+ (C32H34CuN2NaO14): 756.1204; found:
756.1190.
Glucose-functionalized nickel(II)–salphen (1c): Salphen 7c (0.160 g,
0.150 mmol) was dissolved in methanol (120 mL), giving a red solution.
Sodium methoxide (0.122 g, 2.26 mmol) was added and the reaction was
stirred at room temperature for 24 h. Orange precipitate was observed
after stirring for several hours. The orange solid was filtered and yielded
salphen 1c (0.075 g, 68%, orange solid). M.p. 244–2478C (decomposition
started at 2408C); 1H NMR (400 MHz, [D6]DMSO): d=8.57 (s, 2H,
CH=N), 7.88 (s, 2H, aromatic CH), 7.51 (d, 2H, aromatic CH), 7.31 (t,
2H, aromatic CH), 6.88 (d, 2H, aromatic CH), 6.66 (t, 2H, aromatic
CH), 5.30 (s, 2H, CH), 5.13 (d, 4H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H,
CH), 3.48 (broad, 8H, OH), 3.78 (m, 2H, CH), 3.16 ppm (m, 2H, CH);
13C NMR (100.6 MHz, [D6]DMSO): d=164.8 (CH=N), 155.2, 147.0,
136.7, 135.0, 134.1, 120.3, 120.2, 115.3, 104.2 (aromatic C), 101.4, 77.5,
76.7, 73.3, 70.2, 61.0 ppm (CH); IR: n˜ =3314 (m), 2874 (w), 1610 (s), 1590
(m), 1532 (m), 1509 (m), 1465 (m), 1443 (m), 1390 (m), 1373 (m), 1321
Galactose-functionalized copper(II)–salphen (2d): Salphen 2d (92%,
brown solid) was prepared by the same procedure and purification as for
salphen 1a. M.p. 215–2188C (decomposition started at 2128C); IR: n˜ =
3323 (m), 2874 (w), 1609 (s), 1591 (s), 1531 (m), 1505 (m), 1467 (m), 1445
(m), 1436 (m), 1381 (m), 1313 (m), 1278 (m), 1249 (m), 1185 (m), 1151
(m), 1137 (m), 1067 (s), 1045 (s), 1032 (s), 951 (w), 917 (w), 891 (w), 816
(w), 761 (m), 702 (w), 595 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=258
(2.70ꢂ104), 304 (2.15ꢂ104), 312 (2.18ꢂ104), 335 (1.59ꢂ104), 357 (1.68ꢂ
13462
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 13456 – 13465

Salphen–Metal Complexes
FULL PAPER
104), 418 nm (2.60ꢂ104 cmÀ1 mÀ1); ESI-MS: m/z: 756.3 [M+Na]+; HR-
ESI-MS: m/z: calcd for 2d+Na+ (C32H34CuN2NaO14): 756.1204; found:
756.1216.
CH), 4.61 (s, 2H, CH), 3.69 (s, 4H, CH), 3.59 (broad, 4H, OH), 3.45 ppm
(broad, 4H, OH); 13C NMR (75.5 MHz, [D6]DMSO): d=171.9 (CH=N),
161.2, 147.0, 136.0, 134.0, 133.9, 122.9, 119.5, 112.8, 105.2 (aromatic C),
102.2, 76.1, 73.2, 70.4, 68.5, 60.9 ppm (CH); IR: n˜ =3354 (m), 2874 (w),
1615 (s), 1601 (m), 1538 (m), 1504 (m), 1470 (s), 1441 (m), 1387 (m),
1339 (w), 1290 (m), 1207 (w), 1175 (m), 1155 (m), 1064 (s), 1047 (s), 1022
(s), 936 (w), 915 (w), 883 (w), 811 (w), 756 (s), 700 (w), 668 (w), 599 cmÀ1
(w); UV/Vis (methanol): lmax (e)=242 (2.33ꢂ104), 297 (1.82ꢂ104), 343
(1.23ꢂ104), 395 nm (1.97ꢂ104 cmÀ1 mÀ1); UV/Vis (solid): lmax =291,
395 nm; fluorescence (methanol): lmax =506, lexc =395 nm; fluorescence
(solid): lmax =525, lexc =395 nm; ESI-MS: m/z: 735.3 [M+H]+, 757.2
[M+Na]+, 1493.4 [2M+Na]+; HR-ESI-MS: m/z: calcd for 2e+Na+
(C32H34N2NaO14Zn): 757.1199; found: 757.1210.
Acetyl-protected glucose-functionalized zinc(II)–salphen (7e): Salphen
7e was prepared by the same procedure as for salphen 7a. The product
was then purified by chromatography on silica gel (ethyl acetate) and
yielded salphen 7e (32%, yellow solid). M.p. 187–1908C (decomposition
started at 1808C); 1H NMR (400 MHz, [D6]DMSO): d=8.87 (s, 2H,
CH=N), 7.59 (s, 2H, aromatic CH), 7.38 (d, 2H, aromatic CH), 7.24 (t,
2H, aromatic CH), 6.71 (d, 2H, aromatic CH), 6.53 (t, 2H, aromatic
CH), 5.75 (d, 2H, CH), 5.34 (t, 2H, CH), 5.05 (q, 4H, CH), 4.26 (m, 4H,
CH), 4.12 (d, 2H, CH), 2.04 (s, 6H, CH3), 2.03 (s, 6H, CH3), 1.99 (s, 6H,
CH3), 1.91 ppm (s, 6H, CH3); 13C NMR (100.6 MHz, [D6]DMSO): d=
172.0 (CH=N), 170.0, 169.7, 169.3, 168.9 (C(O)CH3), 162.0, 145.4, 136.0,
135.0, 134.3, 123.2, 119.3, 113.0, 105.5 (aromatic C), 97.6, 72.2, 71.2, 70.7,
67.8, 61.5 (CH), 20.4, 20.3 ppm (CH3); IR: n˜ =1748 (s), 1614 (m), 1536
(m), 1503 (m), 1467 (m), 1442 (m), 1370 (m), 1295 (m), 1219 (s), 1175
(m), 1154 (m), 1118 (m), 1065 (s), 1036 (s), 984 (w), 935 (w), 914 (m), 810
(w), 761 (m), 741 (w), 599 (m) cmÀ1; UV/Vis (CH2Cl2): lmax (e)=298
(2.27ꢂ104), 339 (1.93ꢂ104), 377 nm (1.87ꢂ104 cmÀ1 mÀ1); MALDI-TOF-
MS: m/z: 1071.2 [M+H]+, 1093.2 [M+Na]+; HR-ESI-MS: m/z: calcd for
7e+Na+ (C48H50NaN2O22Zn): 1093.2044; found: 1093.2057.
1,2-Bis(b-d-glucopyranosyl)-4,5-dinitrobenzene
(9a):
Triethylamine
(20 mL) was added to a Schlenk flask containing compound 5a (0.500 g,
0.581 mmol) and dry methanol (30 mL). The yellow solution was stirred
at room temperature for 2 d. The solvent was then removed by rotary
evaporation at 508C to obtain a yellow solid. Recrystallization of the
crude product with a methanol/ethanol mixture yields compound 9a
(0.253 g, 83%, off-white solid). M.p. 168–1708C (turned black as it
melted); 1H NMR (300 MHz, [D6]DMSO): d=7.91 (s, 2H, aromatic
CH), 5.39 (d, 2H, CH), 5.22 (d, 2H, CH), 5.16 (d, 2H, CH), 5.08 (d, 2H,
CH), 4.60 (t, 2H, CH), 3.66 (m, 4H, CH), 3.49 (m, 4H, OH), 3.18 ppm
(broad, 2H, OH); 13C NMR (100.6 MHz, [D6]DMSO): d=149.4, 136.5,
112.2 (aromatic C), 100.1, 77.3, 76.5, 73.0, 69.4, 60.5 ppm (CH); IR: n˜ =
3592 (m), 3363 (w), 1594 (w), 1547 (m), 1524 (s), 1511 (m), 1464 (w),
1387 (w), 1367(m), 1345 (m), 1284 (m), 1267 (m), 1219 (m), 1138 (m),
1076 (s), 1036 (s), 1020 (m), 986 (m), 925 (m), 903 (w), 889 (m), 867 (w),
815 (m), 785 (m), 753 (m), 701 (w), 669 (m), 648 (m), 617 cmÀ1 (m); UV/
Vis (DMSO): lmax (e)=270 (7.59ꢂ103), 306 nm (6.24ꢂ103 cmÀ1 mÀ1); ESI-
MS: m/z: 547.3 [M+Na]+, 1071.5 [2M+Na]+; elemental analysis calcd
(%) for 9a (C18H24N2O16): C 41.35, H 4.54, N 5.19; found: C 41.23, H
4.61, N 5.34.
Acetyl-protected galactose-functionalized zinc(II)–salphen (8e): Salphen
8e was prepared by the same procedure as for salphen 7a. The product
was purified by chromatography on silica gel (ethyl acetate/acetone 95:5)
to yield salphen 8e (42%, yellow solid). M.p. 194–1978C (decomposition
started at 1918C); 1H NMR (300 MHz, [D6]DMSO): d=8.87 (s, 2H,
CH=N), 7.60 (s, 2H, aromatic CH), 7.38 (d, 2H, aromatic CH), 7.25 (t,
2H, aromatic CH), 6.71 (d, 2H, aromatic CH), 6.54 (t, 2H, aromatic
CH), 5.68 (d, 2H, CH), 5.40 (s, 2H, CH), 5.24 (m, 4H, CH), 4.45 (t, 2H,
CH), 4.13 (d, 4H, CH), 2.16 (s, 6H, CH3), 2.09 (s, 6H, CH3), 1.97 (s, 6H,
CH3), 1.84 ppm (s, 6H, CH3); 13C NMR (100.6 MHz, [D6]DMSO): d=
172.1 (CH=N), 170.0, 169.9, 169.6, 168.9 (C(O)CH3), 161.8, 145.7, 135.9,
134.9, 134.3, 123.2, 119.3, 113.0, 105.4 (aromatic C), 98.2, 70.8, 70.5, 68.4,
67.4, 61.5 (CH), 20.4 ppm (CH3); IR: n˜ =1748 (s), 1615 (m), 1537 (m),
1504 (m), 1467 (m), 1445 (m), 1370 (m), 1295 (m), 1219 (s), 1176 (m),
1153 (m), 1125 (m), 1069 (s), 1041 (s), 954 (w), 936 (w), 914 (m), 899 (m),
854 (w), 810 (w), 761 (m), 741 (m), 714 (w), 652 (w), 629 (w), 601 cmÀ1
(m); UV/Vis (CH2Cl2): lmax (e)=300 (2.29ꢂ104), 341 (1.99ꢂ104), 379 nm
(1.95ꢂ104 cmÀ1 mÀ1); MALDI-TOF-MS: m/z: 1071.2 [M+H]+, 1093.4
[M+Na]+, 2162.4 [2M+Na]+; HR-ESI-MS: m/z: calcd for 8e+H+
(C48H51N2O22Zn): 1071.2225; found: 1071.2209.
1,2-Bis(b-d-galactopyranosyl)-4,5-dinitrobenzene (9b): Triethylamine
(100 mL) was added to a Schlenk flask containing compound 5b (4.00 g,
4.65 mmol) and dry methanol (140 mL). The yellow solution was stirred
at room temperature for 3 d, resulting in a pale yellow solid and yellow
solution. Filtration of the solid yields compound 9b (2.06 g, 84%, pale-
yellow solid) and no further purification was necessary. M.p. 185–1878C
1
(turned black as it melted); H NMR (400 MHz, [D6]DMSO): d=7.91 (s,
2H, aromatic CH), 5.28 (d, 2H, CH), 5.19 (d, 2H, CH), 4.94 (d, 2H,
CH), 4.67 (t, 2H, CH), 4.63 (d, 2H, CH), 3.69 (m, 6H, CH + OH), 3.51
(m, 4H, OH), 3.43 ppm (m, 2H, OH); 13C NMR (100.6 MHz,
[D6]DMSO): d=149.5, 136.3, 111.9 (aromatic C), 100.7, 75.8, 73.2, 69.9,
67.9, 60.2 ppm (CH); IR: n˜ =3512 (m), 3355 (w), 1594 (w), 1548 (m),
1524 (s), 1512 (m), 1464 (w), 1388 (w), 1368 (m), 1344 (m), 1284 (m),
1267 (m), 1220 (m), 1139 (m), 1076 (s), 1035 (s), 1020 (m), 986 (m), 925
(m), 903 (w), 889 (m), 867 (w), 815 (m), 785 (m), 753 (m), 701 (w), 683
(w), 671 (w), 648 (m), 615 cmÀ1 (m); UV/Vis (DMSO): lmax (e)=270
(8.05ꢂ103), 306 nm (7.00ꢂ103 cmÀ1 mÀ1); ESI-MS: m/z: 547.2 [M+Na]+,
1071.3 [2M+Na]+; elemental analysis calcd (%) for 9b (C18H24N2O16): C
41.44, H 4.65, N 5.28; found: C 41.23, H 4.61, N 5.34.
Glucose-functionalized zinc(II)–salphen (1e): Salphen 1e (94%, yellow
solid) was prepared by the same procedure and purification as for sal-
phen 1b. M.p. 249–2528C (decomposed at 2428C); 1H NMR (300 MHz,
[D6]DMSO): d=8.87 (s, 2H, CH=N), 7.71 (s, 2H, aromatic CH), 7.36 (d,
2H, aromatic CH), 7.23 (t, 2H, aromatic CH), 6.70 (d, 2H, aromatic
CH), 6.50 (t, 2H, aromatic CH), 5.28 (s, 2H, CH), 5.17 (s, 2H, CH), 5.12
(d, 2H, CH), 4.97 (d, 2H, CH), 4.88 (t, 2H, CH), 3.77 (m, 2H, CH), 3.48
(broad, 8H, OH), 3.21 ppm (m, 2H, CH); 13C NMR (100.6 MHz,
[D6]DMSO): d=171.9 (CH=N), 161.4, 146.9, 136.1, 134.1, 134.0, 123.0,
119.6, 112.9, 105.2 (aromatic C), 101.6, 77.5, 76.6, 73.4, 70.3, 61.1 ppm
(CH); IR: n˜ =3351 (m), 2873 (w), 1614 (s), 1532 (m), 1500 (m), 1465 (m),
1440 (m), 1436 (m), 1386 (m), 1346 (w), 1293 (m), 1280 (m), 1246 (w),
1172 (m), 1153 (m), 1095 (m), 1065 (s), 1040 (s), 1014 (s), 934 (w), 915
(w), 875 (m), 811 (w), 755 (m), 669 (m), 603 cmÀ1 (m); UV/Vis (metha-
nol): lmax (e)=242 (2.75ꢂ104), 297 (2.49ꢂ104), 342 (1.66ꢂ104), 394 nm
(2.68ꢂ104 cmÀ1 mÀ1); UV/Vis (solid): lmax =296, 404 nm; fluorescence
4,5-Diamino-1,2-bis(b-d-glucopyranosyl)benzene (10a): Compound 9a
(0.200 g, 0.381 mmol) was added to ethanol (20 mL) and the mixture was
purged with nitrogen for 15 min. Palladium on carbon (2 spatula tips)
and hydrazine (1.50 mL, 30.9 mmol) were then added to the flask under
nitrogen. The resulting mixture was stirred at 908C for 20 h until the so-
lution became clear and colorless. Raney nickel (2 spatula tips) was
added to the reaction flask under nitrogen and the mixture was refluxed
for an additional 1.5 h in order to use up all the remaining hydrazine.
After cooling down to room temperature, the catalyst was removed by
filtration through a Schlenk frit and a colorless filtrate was obtained. The
solvent was then removed under vacuum, yielding air-sensitive compound
10a (0.098 g, 55%, off-white solid). This compound was used without fur-
ther purification. Attempts to remove colored impurities resulted in fur-
ther decomposition, so it was best to purify at the next stage. 1H NMR
(400 MHz, [D6]DMSO): d=6.44 (s, 2H, aromatic CH), 5.16 (s, 2H, CH),
5.13 (s, 2H, CH), 5.05, (s, 2H, CH), 4.49 (d, 2H, CH), 4.35 (t, 2H, CH),
(methanol): lmax
= 507, lexc =394 nm; fluorescence (solid): lmax =527,
lexc =404 nm; ESI-MS: m/z: 735.2 [M+H]+, 757.2 [M+Na]+, 1471.6
[2M+H]+, 1495.5 [2M+Na]+; HR-ESI-MS: m/z: calcd for 1e+Na+
(C32H34N2NaO14Zn): 757.1199; found: 757.1217.
Galactose-functionalized zinc(II)–salphen (2e): Salphen 2e (90%, yellow
solid) was prepared by the same procedure and purification as for sal-
phen 1b. M.p. 253–2568C (decomposition started at 2408C); 1H NMR
(400 MHz, [D6]DMSO): d=8.86 (s, 2H, CH=N), 7.73 (s, 2H, aromatic
CH), 7.36 (d, 2H, aromatic CH), 7.22 (t, 2H, aromatic CH), 6.70 (d, 2H,
aromatic CH), 6.49 (t, 2H, aromatic CH), 5.15 (s, 2H, CH), 4.92 (t, 6H,
Chem. Eur. J. 2009, 15, 13456 – 13465
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M. J. MacLachlan et al.
4.22 (s, 4H, NH2), 3.67 (d, 4H, CH), 3.48 (broad, 2H, OH), 3.15 ppm
(broad, 6H, OH); 13C NMR (100.6 MHz, [D6]DMSO): d=139.4, 130.8,
107.5 (aromatic C), 104.0, 77.0, 76.2, 73.7, 69.7, 60.8 ppm (CH).
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10a. 1H NMR (400 MHz, [D6]DMSO): d=6.42 (s, 2H, aromatic CH),
4.96 (s, 2H, CH), 4.77 (s, 2H, CH), 4.53, (s, 2H, CH), 4.44 (d, 2H, CH),
4.34 (s, 2H, CH), 4.35 (s, 2H, CH), 4.24 (broad, 4H, NH2), 3.67 (s, 4H,
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Salphen–Metal Complexes
FULL PAPER
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Received: July 22, 2009
Published online: November 6, 2009
Chem. Eur. J. 2009, 15, 13456 – 13465
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13465