Anion Coordination of Bis-bisurea Ligands: Aggregation of Dihydrogen Phosphate Anion into Oligomers and Infinite Chains

Article abstract of DOI:10.1002/zaac.201500243

A series of alkanediyl-spaced bis-bisurea ligands (L²-L⁴) were synthesized and their anion coordination behavior studied. These ligands form interesting complexes with polymeric and oligomeric dihydrogen phosphate aggregates in the s

Full text of DOI:10.1002/zaac.201500243

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DOI: 10.1002/zaac.201500243
Anion Coordination of Bis-bisurea Ligands: Aggregation of Dihydrogen
Phosphate Anion into Oligomers and Infinite Chains
Biao Wu,*[a] Cuirong Huo,[a] Shaoguang Li,[b] Yanxia Zhao,[a] and Xiao-Juan Yang[a]
Keywords: Oligourea; Dihydrogen phosphate; Anion clusters; Anion coordination; NMR spectroscopy; UV/Vis spectroscopy
Abstract. A series of alkanediyl-spaced bis-bisurea ligands (L2–L4)
molecules. Meanwhile, two different dihydrogen phosphate-water
were synthesized and their anion coordination behavior studied. These
oligomers, (H2PO4)6·(H2O)4 and (H2PO4)4·(H2O)2, were observed in
ligands form interesting complexes with polymeric and oligomeric di- the complexes with the ligands L3 and L4. In addition, solution anion
hydrogen phosphate aggregates in the solid state. The ligands L2 and
binding properties of the ligands were studied by H NMR and UV/
Vis spectroscopy.
1
–
L3 coordinate with H2PO4 anions to form a unique molecular “neck-
–
lace” with an infinite (H2PO4 )n chain and surrounding ligand
3, 4 and 6) are also known, albeit much rarer.[6–8] Baruah et
Introduction
–
al. obtained a cyclic hexamer, (H2PO4 )6, with a 1-(5-meth-
The supramolecular chemistry of anions has expanded
rapidly in recent years not only for application purposes related
to health, environment, or new materials, but also for the un-
derstanding of the underlying principles of anion coordina-
tion.[1] Phosphate ions have physiological relevance in energy
storage and signal transduction, in addition to being a struc-
tural component in teeth and bones; thus the detection and
ylthiazol-2-yl)-3-phenylthiourea ligand.[9] Very recently, Cus-
–
telcean et al. reported tetrameric and hexameric H2PO4 clus-
ters bound by bis-bisurea ligands, together with a CSD survey
–
on the aggregation of H2PO4 anion and summary of different
types of phosphate clusters.[3e] In our previous work, the ag-
gregation of phosphate ions, such as to a (HPO4·H2PO4)3–
pair[3c] or a [(HPO4)2]4– dimer,[3d] was also observed with
urea-based ligands.
binding of inorganic phosphate (H2PO4 /HPO42–/PO43–) as
–
well as the analogous organic species (ATP/ADP etc.) has
aroused much interest.[2–4] However, due to its large size and
complicated protonation states, the coordination of phosphate
is still a challenge. Most literature reports have focused on the
We have been interested in the anion coordination chemistry
of the tetrahedral sulfate and phosphate ions by using oligourea
receptors.[3a,10] Recently, we developed a strategy to design
oligourea ligands for sulfate/phosphate coordination by mim-
icking the metal-oligopyridine coordination.[3a,5,10b] Such li-
–
protonated dihydrogen phosphate H2PO4 (and occasionally
monohydrogen phosphate HPO42–), while studies on the bind-
3–
3–
ing of the orthophosphate PO4 are relatively rare.[3a,4d,5]
gands showed very good affinity to the trivalent PO4 ion
owing to a combination of chelate effect and conformational
complementarity. By deliberate choice of the spacer of oligo-
bisurea ligands, we were able to construct a series of novel
supramolecular structures based on orthophosphate coordina-
tion, such as the first anion triple helicate, A2L3 (“A” denotes
anion), from an ethylene-spaced bis-bisurea (L1, Scheme 1)[10b]
and the A4L4 tetrahedral cage from a tris-bisurea ligand.[5a]
Interestingly, varying the spacer of bis-bisurea ligand to prop-
ane-1,3-diyl (L2, Scheme 1) led to a mono-bridged A2L3 motif
rather than the expected meso-helicate structure.[5b]
It is known that, with both proton donors and acceptors,
dihydrogen phosphate anion prefers to gather into oligomeric
and polymeric aggregates.[6] Several groups have reported
such aggregates bound by urea-based receptors.[3e,4b,7] For ex-
ample, Fabbrizzi et al. designed a chiral bisurea receptor,
–
which bound a 1D H2PO4 chain formed through hydrogen
–
bonds between two adjacent H2PO4 ions.[4b] Besides the infi-
–
nite chains and networks, discrete (H2PO4 )n clusters (n = 2,
* Prof. Dr. B. Wu
E-Mail: wubiao@nwu.edu.cn
To further explore the anion coordination properties of such
bis-bisureas, we synthesized a series of analogous ligands with
different alkanediyl spacers and terminal functional groups.
Herein, we report the binding of these ligands (L2–L4,
[a] Key Laboratory of Synthetic and Natural Functional
Molecule Chemistry of the Ministry of Education
College of Chemistry and Materials Science
Northwest University
Xi’an 710069, P. R. China
–
[b] State Key Laboratory for Oxo Synthesis & Selective Oxidation
Lanzhou Institute of Chemical Physics
Chinese Academy of Sciences
Scheme 1) towards dihydrogen phosphate ion (H2PO4 ), which
shows interesting aggregation to form both infinite chain and
discrete clusters. In addition, the binding of the spherical chlor-
ide ion was also studied. The solid-state structures of the anion
complexes and their solution binding properties are presented.
Lanzhou 730000, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201500243 or from the au-
thor.
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pounds which could template the synthesis of rotaxanes as well
as provide proton conduction pathways for applications in fuel
cells and sensors.[4b]
Figure 1. Crystal structure of complex 1 (TBA+ cations are omitted
Scheme 1. Structures of ligands L1–L4.
–
for clarity). (a) Two H2PO4 anions are coordinated by one ligand. (b)
n–
The polymerized (H2PO4)n linear chain. (c) Space fill representation
of the molecular “necklace”. The non-interacting atoms and groups are
omitted for clarity.
Results and Discussion
Moreover, in complex 1, two terminal aromatic rings in one
Synthesis and Crystal Structures of the Anion Complexes
ligand are not coplanar and the ligand strands reveal helical
The new ligands L3 and L4 were synthesized by similar pro-
cedures to those employed for L1 and L2,[5b,10b] from p-nitro-
phenylisocyanate or butylisocyanate and 1,1Ј-(butane-1,4-
diyl)- or 1,1Ј-(ethane-1,2-diyl)-bis(3-(2-aminophenyl)urea),
respectively (see Supporting Information for details). The
phosphate complexes were synthesized by treating these li-
gands with certain phosphate salts under different conditions.
n–
features. Along the (H2PO4)n chain, two kinds of enantio-
mers could be seen as shown in Figure S1 (Supporting Infor-
mation). Their permutation is alternate, which makes the crys-
tal racemic. The 3D packing characters can be seen in Figure
S1b, in which the polymeric phosphate chains are located at
the center of the ligand circles and other intermolecular cavi-
ties were filled with TBA+ cations.
(TBA)2[(H2PO4)2L2] (1)
(TBA)2[(H2PO4)2L3] (2)
Ligand L2 could be well dissolved in acetone in the presence
of (TBA)H2PO4 (TBA = tetrabutylammonium cation). Slow
vapor diffusion of diethyl ether into this solution yielded single
crystals suitable for X-ray crystallography with the formula
(TBA)2[(H2PO4)2L2] (1). Complex 1 crystallizes in the mono-
clinic space group C2/c. The asymmetric unit contains one di-
hydrogen phosphate monoanion, half molecule of ligand L2,
Slow diffusion of diethyl ether into a 1,2-dichloroethane
solution of the longer ligand L3 and (TBA)H2PO4 yielded
yellow crystals of the dihydrogen phosphate complex
(TBA)2[(H2PO4)2L3] (2), which shows a similar “necklace”
–
structure to complex 1. The bis-bisurea ligand L3 and H2PO4
anion adopt a similar 1:2 binding mode.
L3 with the butylene spacer displays an AGG-cis conforma-
–
and one TBA+ countercation. Each H2PO4 ion is bound by
–
tion that surrounds the anions. Two H2PO4 ions are bound to
one bisurea domain through four hydrogen bonds [N···O dis-
tances range from 2.801(3) Å to 3.039(3) Å, 2.922 Å on
average; N–H···O angles from 134° to 162°, 150° on average;
Figure 1 and Table S2, Supporting Information]. The TBA+
ion has no direct contribution for anion binding. As shown in
Figure 1a, the twisty AA-cis ligand is further connected by a
pair of short N···O interactions [N···O distance: 3.118(4) Å] of
the terminal nitro groups, forming a molecular “circle” that
four urea NH groups by eight hydrogen bonds (N···O distances
range from 2.769 to 3.033 Å, average 2.923 Å, and N–H···O
angles from 148° to 161°, average 155°; Figure 2 and Table
S3, Supporting Information). A one-dimensional infinite anion
–
–
embraces two H2PO4 anions. These two H2PO4 ions are
linked by a pair of PO–H···O=P hydrogen bonds [O···O dis-
tance: 2.622(3) Å; O–H···O angle: 172°], and are further poly-
merized with adjacent dihydrogen phosphate ions through
intermolecular O–H···O hydrogen bonds [O···O distance:
2.573(3) Å; O–H···O angle: 164°] to yield an infinite anion
n–
chain (Figure 1b). This (H2PO4)n chain strings the ligand
circles to form a unique molecular “necklace” (Figure 1c). The
polymerization (and oligomerization) of the protonated phos-
Figure 2. Crystal structure of complex 2 (TBA+ cations are omitted
for clarity). (a) Top view. (b) Side view of the expanded (H2PO4 )n
–
phate ions could be seen in some inorganic or organic com- chain and the surrounding ligands.
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chain is also observed in the crystal structure resulting from the The structure of complex 3 is similar to that reported by Cus-
self-polymerization of the dihydrogen phosphate anion (O···O telcean with analogous bis-bisurea ligands.[3e] However, due to
distances range from 2.617 to 2.628 Å, average 2.620 Å; the different rigidity of the spacer, there are some differences
O–H···O angles from 152° to 179°, average 172°).
between the two complexes. The more rigid ligands (with p-
phenylene spacer) in the latter case take a more linear confor-
mation and thus span the “dumbbell” [longer side of the
(TBA)3[(H2PO4)3(H2O)2L3] (3)
–
(H2PO4 )6 cluster], whereas in complex 3, each of the bent
Treatment of L3 with an excess of (TBA)H2PO4 in aceto-
nitrile followed by diffusion of diethyl ether afforded big
ligands encloses one “end-cap” of the anion hexamer. As a
result, in the p-phenylene-spaced complexes all of the four
water molecules are located at the end-cap positions, whereas
in complex 3 a pair of H2O molecules (O21) act as bridges to
yellow crystals of
a complex with the composition
(TBA)3[(H2PO4)3(H2O)2L3] (3). Crystal structure of complex
3 reveals that the ligand has an improved adoptability by the
introduction of the butylene spacer. The ligand L3 switches
from a “C”-shaped AGG-cis conformation (in complex 2) to
a stretched, “U”-shaped AGG-cis conformation, with a much
elongated distance between the two terminal nitro groups
(from 4.1 Å in 2 to 14.0 Å). A precious “dumbbell” like
–
link the two internal anions of the (H2PO4 )6 hexamer. In both
cases, it may be viewed that these water molecules terminated
further aggregation of the anions, leading to the discrete hexa-
mer. In the extended structure, adjacent ligand molecules are
connected with each other through weak CH···O interactions
(Figure S2).
–
(H2PO4 )6 hexamer is sandwiched by two antiparallel ligand
molecules, as shown in Figure 3. Three of the anions are linked
to each other by hydrogen bonds into the end-caps and a pair
of hydrogen bonds bridge them together serving as the handle.
(TBA)4[(H2O)2(H2PO4)4L4] (4)
Compared to L1–L3, ligand L4 has two flexible butyl tails
instead of carrying the rigid p-nitrophenyl terminal groups.
The crystallinity of the ligand with anions then varies. Initial
–
The O···O distances between the H2PO4 ions range from
2.587 to 2.631 Å, average 2.601 Å; the OH···O angles from
155° to 175°, average 167°. To the best of our knowledge,
there are only three examples of discrete dihydrogen phosphate
hexamer clusters reported to date. One was found with a cryp-
tand ligand[6b] and the other two were reported by Custelcean
very recently by using rigid p-phenylene-bridged bis-bisurea
ligands. The four terminal dihydrogen phosphate ions at the
end-cap positions are coordinated by eight urea groups from
two ligands by sixteen direct hydrogen bonds (eight for each
anion; N···O distances range from 2.689 to 3.018 Å, average
2.898 Å; NH···O angles from 147° to 167°, average 160°; Fig-
ure 3 and Table S4, Supporting Information). On the other
3–
attempts to synthesize PO4 anion complexes with Na+ or K+
counterions had been unsuccessful, but we eventually got sin-
–
gle crystals by using tetrabutylammonium salt of H2PO4 . The
complex (TBA)4[(H2O)2(H2PO4)4L4] (4) was isolated as yel-
¯
low crystals (space group P1, Figure 4). The asymmetric unit
–
contains one half of ligand L4, two H2PO4 ions, two TBA+
countercations, and one H2O molecule. The ligand adopts a
trans conformation with an “S” shape (the N–C–C–N torsion
angle of the middle ethylene spacer is 180°).
–
hand, the two “internal” H2PO4 ions do not form direct
hydrogen bonds with the ligand; they contact only with the
terminal anions and two water molecules.
Figure 3. Crystal structure of complex 3 (TBA+ cations are omitted Figure 4. Crystal structure of complex 4 (TBA+ cations are omitted
–
–
for clarity). (a) Top view. (b) Side view. (c) The (H2PO4 )6 hexamer for clarity). (a) The binding mode of L4 with (H2PO4 )4·(H2O)2 cluster.
–
linked by hydrogen-bonding interactions between the diprotonated
phosphate anions.
(b) Connectivity between H2PO4 ions.
The dihydrogen phosphate ions aggregate to a zigzag tetra-
Notably, there are four H2O molecules surrounding the meric (H2PO4)4 cluster, which is similar to that observed with
–
(H2PO4 )6 hexamer in the crystal structure. Each of them links the p-phenylene-spaced ligand by Custelcean.[3e] However, a
–
two H2PO4 ions via two hydrogen bonds (O···O distances are close inspection again reveals significant differences. In the
–
2.846 and 2.962 Å for O22, and 3.139 and 3.248 Å for O21). latter case the terminal and internal H2PO4 ions are inter-
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linked by three hydrogen bonds, while the two internal anions ditionally, the terminal nitrophenyl groups of the ligand con-
are bound by two hydrogen bonds (resulting in the nect with another ligand by C–H···O bonds, leading to a one
AϵA=AϵA mode). In comparison, in the (H2PO4)4 tetramer dimensional infinite chain in the extended orientation (Figure
of complex 4 all of the anions are interlinked by double S4, Supporting Information). The two adjacent terminal benz-
hydrogen bonds (A=A=A=A mode; O···O distances between ene rings are parallel and form a π···π stacking interaction
–
H2PO4 ions are in the range 2.505–2.662 Å, and O–H···O (3.532 Å), whereas the TBA+ countercations are located in be-
angles from 119° to 174°). There are two water molecules in tween two layers of ligands (Figure S5).
4, which connect the “pending” oxygen atoms of two phos-
–
phate ions (O···O distances between H2PO4 and H2O are
2.619 Å and 2.646 Å, the O–H···O angle 174° and 177°) as
(TBA)2[Cl2L4] (6)
well as a carbonyl oxygen atom of the ligand (O···O distance
Slow diffusion of diethyl ether into an acetone solution of
2.862 Å, O–H···O angle 149°) in a μ3-bridging fashion. Thus
L4 and excess TBACl yielded yellow crystals of the chloride
the aggregation of the anions may also be viewed as
complex (TBA)2[Cl2·L4] (6). The structure of this complex is
(H2PO4)4(H2O)2 cluster.
Each of the terminal H2PO4– ions of the tetramer is chelated
very similar to that of 5, with two chloride ions being coordi-
nated by one L4 molecule through eight hydrogen bonds
by a bisurea arm by N–H···O bonding (N···O distances are
(N···Cl distances range from 3.259 to 3.264 Å, and N–H···Cl
2.679, 2.799 and 2.798 Å respectively, average 2.759 Å;
angles from 140° to 155°, Figure 6 and Table S7). However, it
can be seen that the hydrogen bonds are somewhat weaker
N–H···O angles are 171°, 169°, and 160° respectively, average
167°, Figure 4 and Table S5, Supporting Information). Taking
the trans conformation of the two bisurea arms, ligand L4
than those in complex 5, which might result from the lack of
the electron-withdrawing nitrophenyl groups in ligand L4. The
readily serves as a bridge between two (H2PO4)4 tetramers.
difference of complex 6 from 5 is the packing mode of the
To this end, complex 4 represents a linear 1D ACP (anion
ligands: there are no stacking interactions in 6 (see Figure S6).
coordination polymer), in which the (H2PO4)4 clusters function
as coordination nodes.[11] Notably, the TBA+ countercations
are also involved in the anion binding through weak
C–H···O interactions (C···O distances range from 3.167 to
3.747 Å; Figure S3).
(TBA)2[Cl2L3] (5)
In addition to the phosphate complexes 1–4, we were also
able to isolate two chloride complexes (5 and 6) with the bis-
bisurea ligands. Light yellow crystals of the complex
(TBA)2[Cl2L3] (5) were obtained from L3 and TBACl in 1,2-
dichloroethane and diethyl ether. Complex 5 consists of one
ligand molecule that adopts an AGA-trans conformation and
two chloride anions bound at both sides of the ligand by the
bisurea entities. Each chloride anion is coordinated by four
hydrogen bonds (N···Cl distances are 3.242 and 3.252 Å, and
N–H···Cl angles are 142° and 160°; Figure 5 and Table S6). In
our previous work we reported similar dichloride complexes
with a related, rigid naphthylene-spaced bis-bisurea ligand.[11]
The average NH···Cl distance in complex 5 is slightly shorter
(by 0.013–0.063 Å) than those in the previous work.[11,12] Ad-
Figure 6. Crystal structure of complex 6 (TBA+ cations are omitted
for clarity).
1
Solution Anion Binding Studies by H NMR and UV/Vis
Spectroscopy
Solution binding properties of the ligands L2–L4 toward di-
hydrogen phosphate and chloride anions were investigated by
–
1H NMR and UV/Vis techniques. For ligand L2 and H2PO4
anion, in the 1H NMR titration experiments using
(TBA)H2PO4 in [D6]DMSO-5% H2O (v/v), all of the NH sig-
nals shifted gradually until 2.0 equiv. of anions were intro-
–
duced, indicating a 1:2 assembly of L2 and H2PO4 at the
NMR concentration. The saturated spectrum is identical to that
of complex 1 dissolved in [D6]DMSO-5% H2O (Figure 7, Fig-
ure S7). Compared with the free ligand, the NH groups in
complex 1 showed moderate downfield shifts (Δδ = 0.63–
1.24 ppm; Figure 7). The shifts of the H7 and H8 protons (Δδ
= 0.59 or –0.07 ppm) were observed due to the variation of
intramolecular hydrogen bonds on these protons, respectively.
There are no obvious changes for the TBA+ part, implying
that the electrostatic attractions have little effect on the anion
binding. In the UV/Vis titration (3ϫ10–5 M of L2 in DMSO-
Figure 5. Crystal structure of the dichloride complex 5 (TBA+ cations
are omitted for clarity).
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–
5% H2O v/v), the H2PO4 anion (as TBA+ salt) induced ba- identical chemical shifts to those observed for L3 and
–
thochromic shifts and reached a plateau at 2.0 equiv. of added 2.0 equiv. of H2PO4 ions (Figure S10). In the titration of L4
guest. The 1:2 (host/guest) binding stoichiometry was further with (TBA)H2PO4, when the anion was continuously added,
confirmed by the Job’s plot.
all of the four NH signals of the ligand shifted downfield
(Figure S16). However, the spectrum did not reach saturation
when 2.0 equivalents of the H2PO4 ions were added, and the
–
NH signals kept shifting with the addition of more anions.
1H NMR titration of L3 and L4 with Cl– anions (Figures
S12, S19, Supporting Information) was carried out and the as-
sociation constants calculated (Table 1). The signals of NH
protons showed slight and gradual downfield shifts with the
addition of Cl– ions, and the changes were not finished after
2.0 equivalents of Cl– ions were added. The binding stoichio-
metry was determined to be 1:2 (ligand to anion) by the Job’s
plot method (Figures S13, S20). Moreover, other anions were
also screened for ligands L3 and L4 by 1H NMR spectroscopy.
Figure 7. 1H NMR spectra of free ligand L2, complex 1, and L2
(2.0ϫ10–3 M) with 2.0 equiv. of (TBA)H2PO4 in [D6]DMSO-5% H2O
(v/v).
–
2–
When 1.0 equiv. of F–, H2PO4 , or SO4 (as TBA+ salts) ions
were added to the solution of L3, the NH signals were broad-
ened or even disappeared (Figures S8, S15), while L4 showed
only moderate changes, with a maximal downfield move of
0.9 ppm for the NH signals (Figure S15). The anion binding
properties of ligand L3 were further studied by UV/Vis spec-
troscopy. Among various anions examined, the addition of
–
In the case of L3, when H2PO4 ions (as TBA salt) were
titrated, the four sets of NH signals shifted to downfield grad-
ually and the changes reached 0.65–1.78 ppm upon addition of
–
2.0 equivalents of H2PO4 ions (Figure 8). With more added
2–
–
SO4 anion caused the largest bathochromic shift, while
H2PO4 , the signals of NHs showed no further changes, sug-
–
AcO–, BzO–, H2PO4 , and F– resulted in slight changes and
gesting a 1:2 binding mode, which is in agreement with the
Job’s plot curve (Figure S9). The association constants were
determined using the WinEQNMR program (errors are less
than 10% in all cases; see SI for details)[11,13] and the values
other anions showed almost no change (Figure S22). These
results are in agreement with the NMR studies.
1
are summarized in Table 1. On the other hand, the H NMR
spectrum of complex 2 ([D6]DMSO-5% H2O) showed nearly
Conclusions
We have studied the anion binding properties of four alkane-
diyl-linked bis-bisurea ligands. Several complexes of di-
hydrogen phosphate were isolated in the solid state, which dis-
play interesting aggregation of the anion into infinite chain and
discrete clusters. These include a unique molecular necklace,
–
in which the anions polymerize to an infinite (H2PO4 )n chain
that strains the nearly circular ligand molecules, and two dif-
ferent types of dihydrogen phosphate-water oligomers,
–
–
(H2PO4 )6·(H2O)4 and (H2PO4 )4·(H2O)2. Solution anion-bind-
ing behavior was studied by NMR and UV/Vis spectroscopy.
The presented work may serve to understanding the principles
of phosphate coordination and provide guidance for future re-
ceptor design.
Experimental Section
1
Figure 8. Change of H NMR signals of urea NH groups on L3 with
Synthesis of Ligands L3 and L4: Detailed synthetic processes for
–
addition of H2PO4 ions in [D6]DMSO-5% H2O (v/v).
ligands L3 and L4 are given in the Supporting Information.
L3: Light yellow solid. M.p.: 235 °C. 1H NMR (400 MHz,
Table 1. Association constants log Ka (M–1) for receptors L3 and L4
towards H2PO4– and Cl– in [D6]DMSO-0.5% water at 298 K obtained [D6]DMSO, ppm): δ = 9.86 (s, 2 H, Hd), 8.25 (s, 2 H, Hc), 8.18 (d, J
1
by H NMR titrations (errors Ͻ 10%).
= 8.8 Hz, 4 H, H8), 7.88 (s, 2 H, Hb), 7.70 (d, J = 8.8 Hz, 4 H, H7),
7.54 (d, 2 H, J = 7.6 Hz, H3), 7.50 (d, 2 H, J = 7.6 Hz, H6), 7.05 (m,
4 H, H4+H5), 6.57 (s, 2 H, Ha), 3.11 (s, 4 H, H2), 1.47 (s, 4 H, H1).
13C NMR (100 MHz, [D6]DMSO, ppm): δ = 155.9 (CO), 152.7 (CO),
146.7 (C), 140.9 (C), 125.2 (C), 124.9 (CH), 124.8 (CH), 123.2 (CH),
117.3 (CH), 38.9~40.1 (CH2 is overlapped by solvent peak), 29.3
–
H2PO4
Cl–
log K1
log K2
log K1
log K2
L3
L4
4.31
4.61
1.61
0.86
4.68
4.67
1.03
0.67
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Soc. Rev. 2009, 38, 506–519; d) K. Bowman-James, A. Bianchi,
(CH2). IR (KBr): ν˜ = 3294, 3218, 3096, 1652, 1605, 1551, 1497, 1338,
1301 cm–1. C30H28N10O8: calcd. C 54.88; H 4.30; N 21.33%; found:
C 54.92; H 4.48; N 21.45%. ESI-MS: m/z 100%, 683.2 [M–H]–;
55.2%, 719.2 [M + Cl]–.
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1
L4: Off white solid. M.p.: 276 °C. H NMR (400 MHz, [D6]DMSO,
ppm): δ = 7.89 (s, 2 H, Hb), 7.69 (s, 2 H, Hc), 7.60 (d, J = 7.2 Hz, 2
H, H2), 7.39 (d, J = 11.2 Hz, 2 H, H5), 6.99 (t, J = 7.2 Hz, 2 H, H3),
6.92 (t, J = 7.2 Hz, 2 H, H4), 6.60 (s, 2 H, Ha), 6.54 (s, 2 H, Hd),
3.18 (b, 4 H, H1), 3.00 (d, J = 4.8 Hz, 4 H, H6), 1.34 (d, J = 6 Hz, 2
H, H7), 1.28 (t, J = 6 Hz, 2 H, H8), 0.87 (t, J = 6.8 Hz, 3 H, H9). 13
C
NMR (400 MHz, [D6]DMSO, ppm): δ = 156.6 (CO), 155.8 (CO),
133.2 (C), 130.4 (C), 124.8 (CH), 124.1 (CH), 122.7 (CH), 122.5 (CH),
31.9 (CH2), 19.7 (CH2), 13.9 (CH3). IR (KBr): ν˜ = 3302, 3107, 2955,
2933, 2868, 1644, 1568, 1481, 1447, 1260 cm–1. C26H38N8O4: calcd.
C 59.30; H 7.27; N 21.28%; found: C 59.32; H 7.27; N 21.27%. ESI-
MS: m/z 100%, 561.3 [M + Cl]–; 32.24%, 525.3 [M–H]–.
Synthesis of Anion Complexes 1–6: The anion complexes were syn-
thesized by the following general procedure: Ligand L3 or L4
(0.5 mmol) was dissolved in certain organic solvent (2 mL) in the pres-
ence of (TBA)H2PO4 or TBACl (1 mmol) (TBA = tetrabutylammo-
nium cation). Slow vapor diffusion of diethyl ether into this solution
yielded single crystals of 1–6 suitable for X-ray diffraction.
X-ray Crystallography: Diffraction data were collected with a Bruker
SMART APEX II diffractometer at 150 K with graphite-monochro-
mated Mo-Kα radiation (λ = 0.71073 Å) for complex 1 and at 296 K
for complexes 2–6. An empirical absorption correction using SADABS
was applied for all data. The structures were solved by direct methods
using the SHELXS program. All non-hydrogen atoms were refined
anisotropically by full-matrix least-squares on F2 by the use of the
SHELXL program. Hydrogen atoms bonded to carbon and nitrogen
were included in idealized geometric positions with thermal parameters
equivalent to 1.2 times those of the atom to which they were attached.
Some restrictions, such as DFIX and DAMP, have been used for the
structures of 2, 4, and 5. In addition, the protons of one water molecule
are not included in complex 3. Crystal data and refinement details for
complexes 1–6 are summarized in Table S1 (Supporting Information).
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1050795, CCDC-1050796, CCDC-1050797, CCDC-
1050798, CCDC-1050799, and CCDC-1050800 (Fax: +44-1223-336-
033; E-Mail: deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk)
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Supporting Information (see footnote on the first page of this article):
Experimental details including synthesis of the ligands, crystallo-
graphic data, NMR and UV/Vis spectroscopic data.
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Acknowledgements
[11] J. Wang, S. Li, P. Yang, X. Huang, X.-J. Yang, B. Wu, Cryst-
This work was supported by the National Natural Science Foundation
of China (21271149 and 21325102).
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