A new phenanthrene-based bis-oxime chemosensor for Fe(III) and Cr(III) discrimination

Article abstract of DOI:10.1016/j.tet.2012.03.089

The synthesis of two new 2,7-disubstituted phenanthrene-based bis oximes is described. The ability of these two compound for complexing heavy metal cations have been studied and complexation constants and complex stoichiometry for Cr³⁺ and Fe³⁺ complex have been determined. The fluorescent properties of ligand 2 make this compound able to act as a sensor able to discriminate between Cr³⁺ and Fe³⁺. Detection limits for these two cations have been evaluated.

Full text of DOI:10.1016/j.tet.2012.03.089

Tetrahedron 68 (2012) 4882e4887
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A new phenanthrene-based bis-oxime chemosensor for Fe(III) and Cr(III)
discrimination
b
a
,
a
b
a
*
Virginia Bravo , Salvador Gil , Ana M. Costero , María N. Kneeteman , Ursula Llaosa ,
b
a
a
Pedro M.E. Mancini , Luís E. Ochando , Margarita Parra
Instituto de Reconocimiento Molecular y Desarrollo Tecnol oꢀ gico (IDM), Centro Mixto Universidad Polit ꢀe cnica de Valencia, Universitat de Val ꢁe ncia, Dr. Moliner 50,
a
4
6100 Burjassot, Spain
b
Departamento de Química Org aꢀ nica, Facultad de Ingeniería Química, UNL, Santiago del Estero 2829, 3000 Santa Fe, Argentina
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of two new 2,7-disubstituted phenanthrene-based bis oximes is described. The ability of
these two compound for complexing heavy metal cations have been studied and complexation constants
Received 23 December 2011
Received in revised form 7 March 2012
Accepted 21 March 2012
Available online 5 April 2012
3þ
3þ
and complex stoichiometry for Cr and Fe complex have been determined. The fluorescent properties
3þ
3þ
.
of ligand 2 make this compound able to act as a sensor able to discriminate between Cr and Fe
Detection limits for these two cations have been evaluated.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Chemosensor
Dioxime
Chromium
Iron
Fluorescence
1
. Introduction
induces a change in at least one physical property of the second.
Sensors based on ion-induced changes in fluorescence are espe-
cially suitable as they are easy to use and give an instantaneous
The design and synthesis of new chemosensors for heavy and
11,12
3þ 3þ
transition metal cations is an important subject in the field of su-
pramolecular chemistry.
sistently demonstrated their potential in a variety of fields, such as
biological probes, environmental sensors, food safety, etc. and
response with high sensitivity.
Because Fe and Cr are de-
1e3
Optical sensors for cations have con-
scribed as two of the most efficient fluorescence quenchers among
the transition metal ions, a fluorescence signal transduction oc-
4
,5
13
currence on chelation was expected.
6
,7
new ligands are developed continuously. Trivalent form of iron
and chromium are essential elements for life because they play vital
roles in structural, catalytic and regulatory aspects of biological
systems. On the other hand, chromium is an environmental pol-
lutant and its build-up due to various industrial and agricultural
activities is a matter of concern. Particular interest merits the
control of water pollution by chromium salts in areas where the
tanning industry is relevant as it is the case of South American
rivers. It is known that the Fe and Cr sensors are usually coming
by interference between them, and then sensitive and selective
During the last few years, our research group has been in-
terested in studying chemosensors containing biphenyl units in
their structures where the recognition process is coupled to the
14,15
signaling action.
In these chemosensors, changes in the color-
imetric or fluorescence properties were based on the modification
in the dihedral angle between both aromatic rings induced by the
complexation event. On the other hand, introduction of different
substituents on the biphenyl system gives rise to strong modifica-
8
,9
3
þ
3þ
16,17
tions in both, optical and electrochemical properties.
Going a forward step we decided to study the influence that the
increment of rigidity in the system has on the chemosensor be-
havior and for this reason now we report the behavior of two (2,7-
disubstituted phenanthrene-9,10-dione)-based chemosensors
(1e2). As binding site two oxime groups were attached at the 9 and
10
detection of these metal ions still need to be developed.
One of the best approaches toward the development of che-
mosensors consists in coupling a binding site with a signaling
subunit in such a way that the coordination event in the former
10 positions of the aromatic systems. It is clearly established that
oxime groups acts as ligands for cation complexation by formation
1
8,19
of five or six-membered chelate rings.
Thus, phenanthrene-
*
Corresponding author. Tel.: þ34 963 543 135; fax: þ35 963 543 831; e-mail
address: salvador.gil@uv.es (S. Gil).
9,10-dioximate and related compounds containing long alkyl
0
040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.089

V. Bravo et al. / Tetrahedron 68 (2012) 4882e4887
4883
chains at the 2,7 positions have been used in complexing some
2
0,21
transition metal cations.
describes a method based on the formation of metal complexes by
-benzyl dioxime supported on sodium dodecyl sulfate-coated
In addition, one recent publication
a
alumina. In this procedure, metals, such as Cu, Ni, Pb, Co, and Fe
can be analyzed in one run by carrying out the simultaneous sep-
2
2
aration and quantification of them.
2
2
. Results and discussion
.1. Synthesis and X-ray structure
Ligands 1 and 2 were easily prepared as described in Scheme 1,
starting from phenanthrene-9,10-dione, which under nitration
0
conditions, gives 4,4 -dinitro derivative 3 in 61% yield as yellow
crystals from MeOH. Reduction of dinitro groups to amino groups
course under standard conditions with a 69% yield. For the syn-
thesis of dioxime compounds 1 and 2, it was necessary to optimize
the reaction conditions, especially the solvent and base, because it
is usual a dehydration process in the reaction progress and mono-
dioxime can be isolated as secondary product. Finally, successful
transformation into bis-oxime 1 was performed using an excess of
hydroxylamine hydrochloride in a mixture of pyridine and ethanol
(
1:8) as co-solvents under reflux (2 days), with 64 and 66% yield,
23,24
respectively.
The bis-dioxime, under these conditions, is
obtained as a mixture of isomers being the thermodynamically
more stable E,E-isomer highly predominant.
Fig. 1. (a, top) Zigzag conformation of 4 molecules with water molecules as a bridge.
(b, bottom) Two types of H-bonds.
ꢂ
ꢂ
through a water molecule (N2eO3¼3.018 A and O2eO3¼2.940 A),
where O3 is the oxygen atom of the water molecule (Fig. 1b). The
different zigzag networks are also connected through hydrogen
bond interactions. In this case, the interactions are established
2
between the NH group of one molecule and the O]C group of the
other, being both molecules in the same plane (bond length of
ꢂ
N1eO1¼3.003 A).
2.2. Complexation and sensing experiments
Scheme 1. Synthesis of ligands 1 and 2.
The UVevis spectrum of the oxime 1 (1.0ꢀ10ꢁ mol dm ) in
5
ꢁ3
As the vicinal dioxime showed to be a quite sensitive group,
direct reduction of 1 to 2 was not tested. Thus, the synthesis of 2
was carried out from compound 4 under the same conditions
proved useful in the preparation of ligand 1. As previously, com-
pound 2 was obtained as a mixture, being major the E,E-isomer. The
parent compound 4 was obtained by reduction of 3 with sodium
sulfide. Compound 4 was isolated as blue crystals that were suitable
for X-ray diffraction. The crystal structure determination process
revealed that the single molecule is essentially flat with standard
bond distance and angle values. However, a water molecule ap-
pears as a crystallization molecule, that induces a crystal packing
with hydrogen bonds between the 2,7-diamino-9,10-phenan-
threnequinone molecules (4) among them and with the water
molecules. As a result of these interactions, molecules with two
different orientations (A and B) are alternately present in a zigzag
network. Molecules A and B are interconnected through water
molecules. The connection is due to the presence of hydrogen
DMSO/MeOH (9:1) showed three bands at 264, 292 and 345 nm
ꢁ1
ꢁ1
with ε¼11,100, 11,040 and 10,920 M cm , respectively. On the
ꢁ5
ꢁ3
other hand, compound 2 (1.0ꢀ10 mol dm ) in CH
3
CN/MeOH
ꢁ
1
ꢁ1
(9:1) showed a band at 330 nm (ε¼15,570 M cm ) with
ꢁ
1
ꢁ1
a shoulder at 417 (ε¼1460 M cm ) nm. In addition, 2 exhibits
fluorescence emission at
l
em¼515 nm ( exc¼417 nm).
l
In order to know the influence that the amino groups had in the
fluorescent properties of 2, a simple theoretical energy minimiza-
tion of ligand 2 was carried out by using the HF-3-21G basis set. The
obtained results shows that the lone pair on the amino nitrogen are
placed in a deeper MO (HOMO-2, ꢁ9.66 eV) than oxyme’s both lone
pairs and
p
bonds (ꢁ7.70 and ꢁ9.66 eV). As a consequence the
amino groups seem not to be involved in a PET process. This hy-
pothesis was experimentally corroborate. Thus, a clear quenching
of the fluorescence was observed when the fluorescence spectrum
of compound
Supplementary data).
2 was registered under acid conditions (see
bonds (Fig. 1a) formed between the NH
orientation A with the O]C group of a molecule in orientation B
2
group of a molecule in
The ability of ligands 1 and 2 in cation complexation was studied
with Cr and Fe , as their nitrate salts. As can be seen in Fig. 2,
3
þ
3þ

4884
V. Bravo et al. / Tetrahedron 68 (2012) 4882e4887
1
1
.4
.2
1
0
0
0
0
.8
.6
.4
.2
0
250
260
270
280
290
wavelength (nm)
1
1
1
.6
.4
.2
1
0
0
0
0
.8
.6
.4
.2
0
300
350
400
wavelength (nm)
450
500
Fig. 2. (up) UVevis titration spectra of 1 with Cr3 in (1.0ꢀ10 mol dm ) DMSO/
þ
ꢁ5
ꢁ3
MeOH (9:1); (bottom) UVevis titration spectra of 2 with Cr3 in (1.0ꢀ10ꢁ5 mol dm
þ
ꢁ3
)
DMSO/MeOH (9:1).
a strong hyperchromic effect was observed in the UV spectrum of 1
3
þ
upon the gradual addition (0e30 equiv) of a solution of Cr in
DMSO/MeOH (9:1). A 1:1 stoichiometry was evaluated for the
complex following the method of continuous variations (see
Supplementary data) with
a complexation constant of log
ꢁ
5
ꢁ3
2
5
Fig. 3. Fluorescence titration spectra of ligand 2 (1.0ꢀ10 mol dm ) in DMSO/MeOH
3 3þ
þ
b¼3.7ꢂ0.1 as determined by the Specfit programe. By contrast
(9:1) (
l
exc¼417 nm) with (up) Cr and (bottom) Fe
.
ligand 2 gave rise to different results probably due to the presence
of the amino groups. In this case a 1:2 stoichiometry is observed for
the complex with a complexation constant of log
b
¼6.2ꢂ0.2.
Even though, the modifications in the UV spectrum observed
with ligand 2 are smaller than those observed with ligand 1 it
presents the additional advantage of its fluorescent properties that
allow to use it as a fluorescent sensor. Thus, Fig. 3 shows the fluo-
bands corresponding to the OeH of quinonodioximes appear at
ꢁ1
2917 and 2848 cm . In the complex, a broad band centered at
ꢁ
1
3219 cm appears. This band could be assigned to an ammo-
nium group generated by a proton transfer from the oxime group
in the presence of the metal. This idea is supported by the ab-
sence of the OeH bands. On the other hand, the C]N band in the
rescence emission (
l
exc¼417 nm) changes of 2 in DMSO/MeOH
ꢁ
5
ꢁ3
3þ
(
9:1) solution (1.0ꢀ10 mol dm ) upon the addition of Cr . The
ꢁ1
addition of the salt gives rise up to a 62% enhancement of the
complex appears at higher values 1653 cm whereas the NeO
ꢁ1
fluorescence. It is well established that some metal complexes with
band is shifted to lower values (958 cm ). These data suggest
that the cations are bound to the oxygen of the oximate
2
6
oximes can involve deprotonation of the C]NeOH group and in
ligand 2, this proton could protonate the aniline moiety. However
the enhancement of the fluorescence cannot be related to this
possible effect because it has been established that protonation of
ligand 2 induces the quenching of the fluorescence. On the other
hand, the complex stoichiometry seems to play an important role in
the emission properties of the complex. This fact was demonstrated
by carrying out complementary complexation studies with Fe
UV experiments with this cation showed a 1:1 stoichiometry with
a complexation constant of log
2
7
moieties.
In relation with de 1:1 complex formed between ligand 1 and
Cr3 it was observed in the IR spectrum that the strongest modi-
þ
fication appears in the C]N band that is shifted toward lower
ꢁ
1
ꢁ1
values (from 1579 cm in the free ligand to 1506 cm in the
complex). This fact suggest that the C]N groups are involved in the
3
þ
28
.
metal coordination. On the other hand, the observed stoichiom-
3
þ
etry in the complex formed between 2 and Fe suggests a complex
3
þ
b¼4.4ꢂ0.1. In this case, no en-
with a similar geometry that those showed by 1 Cr
.
hancement of the fluorescence was observed and only quenching
due to the heavy atom effect was produced.
These data suggests that the observed increment in the fluo-
rescence in the 1:2 complex could be related to the different type of
complex formed in these case when it is compared with the 1:1
complex.
To gain information about the selectivity exhibit by ligand 2,
other cations of interest were studied but they gave no appreciable
response (Fig. 4).
To have information about the different complexes, IR spectra
of ligand 2 and its Cr3 complex were registered. The free ligand
þ
ꢁ
1
shows bands at ca. 3470 and 3338 cm that correspond to the
aniline moiety and at 1602 (C]N) and 1017 cm (NeO) that are
due to the oxime group. In addition the characteristic absorption
ꢁ
1

V. Bravo et al. / Tetrahedron 68 (2012) 4882e4887
4885
0
0
0
.6
.4
.2
0
under reflux. The resulting mixture was stirred under reflux for
0 min. The dark blue crystals formed were filtered and recrystal-
lized from hot methanol for obtained 0.544 g of (4) (yield 68%). IR
3
ꢁ
1
1
(
KBr)
NMR (300 MHz, solvent DMSO-d
7.75 (2H, d, J¼7.8 Hz, H-H-4 and H-5), 7.06 (2H, J¼7.8 Hz, H-3 and H-
), 6.25 (4H, 2-NH ).
n
(cm )¼3580, 3300, 1580, 1505, 1345, 1090, 738, 711.
H
6
):
d
¼8.05 (2H, br s, H-1 and H-8),
6
2
-
-
-
-
0.2
0.4
0.6
0.8
4.4. Synthesis of 2,7-dinitro-9,10 phenanthrenequinone
dioximes (1)
Hydroxylamine hydrochloride (8 g), pyridine (16 mL) and 3
(0.50 g, 1.68 mmol) in ethanol (95%, 100 mL) was stirred under
Cr
Cu
Ni
Al
Ru
Co
Zn
Fe
reflux for 48 h; a colour change from yellow-orange to dark occurs.
After two additionally hours at room temperature, pyridine hy-
drochloride as colorless needles was filtrated. Water (100 mL) ad-
dition at room temperature to the filtrate led to a green
precipitated, which was purified from aqueous methanol to give
Fig. 4. Metal-ion selectivity of ligand 2.
Thus, ligand 2 is a sensor able to distinguish between Cr3þ and
Fe3 due to the different stoichiometry of the complexes, giving rise
þ
1
dioxime 1 (0.352 g, 64% yield). H NMR (500 MHz, solvent DMSO-
to a different fluorescence response. From fluorescence titrations,
detection limits of 140 mM for the sensing of Fe and of 400 mM for
d
8
6
):
d
¼10.07 (2H, br s, eOH), 8.54 (2H, d, J¼2.0 Hz, H-1 and H-8),
3þ
.51 (2H, d, J¼7.5 Hz, H-4 and H-5), 8.36 (2H, dd, J¼7.5 and 2.0 Hz,
3
þ
Cr can be attained.
. Conclusions
Two new 2,7-disubstituted phenanthrene-based bis oximes
have been prepared and their heavy metal cation complexation
ability has been explored. Ligand 2 give rise to different complex
stoichiometries depending on the cation. Thus, a 1:2 2 Cr com-
plex is formed, whereas a 1:1 stoichiometry is observed for 2 Fe
13
H-3 and H-6). C NMR (125 MHz, solvent DMSO-d
6
): 148.4, 141.5,
þ
1
35.7, 133.6, 128.1, 125.6, 119.8. HRMS (M ꢁH): found 327.0367,
3
calcd for C14
7 4 6
H N O 327.0366.
4.5. Synthesis of 2,7-diamino-9,10 phenanthrenequinone
dioximes (2)
.
3þ
.
3þ
Hydroxylamine hydrochloride (8 g), pyridine (16 mL) and 4
.
(0.50 g, 2.10 mmol) in ethanol (95%, 100 mL), was stirred under
Complex stoichiometry has strong influence on the fluorescent
properties of 2 and, for this reason; this ligand can be used in the
discrimination of these two cations: Cr induced an enhancement
reflux for 48 h; a colour change from yellow-orange to dark occurs.
After 2 h at room temperature, pyridine hydrochloride, as long
colorless needles, was filtered off. Upon addition of water (100 mL)
at room temperature to the filtrate, and one week left in refrigerator
a few amount of a green precipitate was filtered off. Then, the so-
lution was extracted with ethyl acetate, the combined organic
phases washed with water and brine, dried with sodium sulfate and
the solvent evaporated to give a solid residue that was purified
from aqueous methanol to give dioxime 2 (0.371 g, 66% yield). IR
3
þ
3
þ
of the fluorescence whereas Fe gives rise to a quenching.
4
4
. Experimental section
.1. General procedures and materials
All reagents commercially available were used without purifi-
ꢁ
1
1
1
13
(KBr)
NMR (300 MHz, solvent CD
Br s, eOH), 7.37 (2H, d, J¼7.0 Hz, H-4 and H-5), 7.22 (4H, m, H-1, H-3,
n
(cm )¼3580, 3569, 1685, 1578, 1509, 1090, 739, 711.
H
cation. H and C NMR spectra were recorded with the deuterated
solvent as the lock and residual solvent as the internal reference.
High-resolution mass spectra were recorded in the positive ion
mode on a VG-AutoSpec. UVevis spectra were recorded using
a 1 cm path length quartz cuvette. All measurements were carried
out at 293 K (thermostated). Fluorescence spectra were carried out
in a Varian Cary Eclipse Fluorimeter.
3
CN):
d
¼8.60 (1H, Br s, eOH), 8.36 (1H,
1
3
H-6, H-8). C NMR (125 MHz, solvent DMSO): 148.4, 141.5, 135.7,
33.6, 128.1, 125.6, 119.8.
1
4.6. Titration experiments
Binding constants of ligand 1 and 2 toward cations were eval-
4
.2. Synthesis of 2,7-dinitro-9,10 phenanthrenequinone
2
9,30
uated by UVevis and fluorescence titrations in acetonitrile. Typi-
(
3)
ꢁ
5
cally, 10 M solutions of the receptors in DMSO/MeOH (9:1) (3 mL)
were titrated by adding 0.5 equiv aliquots of the envisaged cations
In a two necked flask, 9,10-phenanthrenequinone (3.00 g,
in CH
3
CN and registering the UVevis or fluorescence spectrum
was calculated by fitting all
15.625 mmol) was placed in a mixture of fuming nitric acid (40 mL)
after each addition. The value of log K
spectrophotometric titration curves with the SPECFIT program.
c
and 95e98% sulfuric acid (4 mL). After 45 min refluxing a yellow
solid was obtained. This solid was recrystallized from acetic acid for
2
5
2
9,30
obtained 2.825 g of yellow crystals identified as (3) (yield 61%).
1
H NMR (300 MHz, solvent DMSO-d
6
):
d
¼8.79 (2H, d, J¼7.8 Hz, H-4
4.7. X-ray structure analysis of compound 4
and H-5), 8.78 (2H, d, J¼2.0 Hz, H-1 and H-8), 8.64 (2H, dd, J¼7.8
and 2.0 Hz, H-3 and H-6).
Intensity measurements were made on an Oxford Xcalibur Nova
diffractometer using a blue prismatic single crystal of dimensions
4
.3. Synthesis of 2,7-diamino-9,10 phenanthrenequinone (4)
0.80ꢀ0.30ꢀ0.10 mm. Graphite-monochromated Cu-K
a
radiation
ꢂ
(l
¼1.54184 A) and
u-scan technique was used. Data collection was
To a stirred solution of sodium sulfide (0.70 g, 9.0 mmol) in the
carried out at room temperature (293 K). Three reference re-
flections were measured every 2 h as an intensity and orientation
check and no significant fluctuation was noticed during the col-
lection of the data. Lorentz-polarization correction was made.
minimum amount of hot water, sodium carbonate (0.72 g) was
slowly added. The resulting solution was added to 2,7-dinitro-9,10
phenanthrenequinone (3) (1.0 g, 3.36 mmol) in methanol (20 mL)

4886
V. Bravo et al. / Tetrahedron 68 (2012) 4882e4887
The crystal structure was solved by direct methods using the
phenanthrenequinone molecules, among them and with the water
molecules are summarized in Table 3. Additional crystallographic
data (bond lengths and angles, anisotropic displacement parame-
ters, hydrogen coordinates and torsion angles, excluding structure
factors) for this structure have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication number
CCDC 853490. These data can be obtained via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.uk free
of charge, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: þ44 1223
31
SHELX system and refined by full-matrix least-squares tech-
31
2
niques on F . The non-hydrogen atoms were refined anisotropi-
cally. All the hydrogen atoms were geometrically constructed with
fixed displacements parameters. Molecular graphic of the structure
3
2
(
Fig. 5) was made with ORTEP and graphic showing the H-bond
3
3
packing (Fig. 1) were made with MERCURY. Solution, refinement,
geometrical calculations and graphics was performed with the
WinGX package.34
336033.
Table 2
Atomic coordinates (ꢀ10 ) and equivalent isotropic displacement parameters
ij
4
ꢂ
2
3
(
A ꢀ10 ) for 4. U(equiv) is defined as one third of the trace of the orthogonalized U
tensor
x
y
z
U(equiv)
O(3)
C(10)
C(4)
C(1)
C(9)
C(14)
C(5)
C(11)
C(12)
C(8)
C(2)
C(3)
N(2)
N(1)
O(1)
C(6)
C(13)
C(7)
O(2)
3342(8)
1446(5)
3253(6)
1123(5)
2502(6)
146(5)
7046(6)
3759(4)
4235(4)
4201(4)
3756(4)
4205(4)
4231(4)
3309(4)
3310(4)
3303(4)
4735(4)
4760(5)
3722(4)
3788(4)
5144(3)
3752(5)
3768(5)
3288(4)
5247(3)
ꢁ630(20)
1551(13)
1611(12)
ꢁ656(12)
2631(13)
233(6)
40(2)
44(2)
41(2)
40(2)
45(2)
53(2)
49(2)
47(2)
49(2)
44(2)
50(2)
75(2)
64(2)
60(2)
54(2)
47(2)
57(2)
74(2)
ꢁ1715(13)
2660(14)
2594(13)
1516(13)
4802(13)
ꢁ1814(13)
ꢁ547(14)
5680(13)
ꢁ1717(12)
ꢁ3717(10)
4688(14)
ꢁ637(14)
5772(14)
ꢁ1447(11)
4272(5)
699(5)
ꢁ280(5)
2878(5)
1846(5)
2947(6)
5639(5)
ꢁ1608(4)
1599(4)
4635(6)
ꢁ597(5)
3909(6)
3532(4)
Fig. 5. Molecular structure with crystallographic numbering scheme for compound 4.
Atoms have been drawn with thermal ellipsoids set at a 50% probability level.
Information concerning crystallographic data collection is
summarized in Table 1. Atomic coordinates and equivalent isotropic
displacement parameters for non-hydrogen atoms are shown in
Table 2. Hydrogen bonds between the 2,7-diamino-9,10
Table 3
ꢂ
Summary of intermolecular H-bond distances (A)
Atom 1
Atom 2
‘Symm.
op. 1’
‘Symm. op. 2’
Length
Length-VdW
1
2
O3
O3
O2
N2
x, y, z
x, y, z
x, y, z
1ꢁx, 1/2þy,
2.940
3.018
ꢁ0.100
ꢁ0.052
Table 1
Crystal data and structure refinement for 4
1
/2ꢁz
3
N2
O3
x, y, z
1ꢁx, ꢁ1/2þy,
3.018
ꢁ0.052
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C
14
H
10
N
2
O
2
þH
2
O
1/2ꢁz
256.26
293(2) K
1.54184 A
Monoclinic
P2 /c
4
5
6
N1
O1
O2
O1
N1
O3
x, y, z
x, y, z
ꢁx, 1ꢁy, ꢁ1ꢁz
ꢁx, 1ꢁy, ꢁ1ꢁz
ꢁx, 1ꢁy, ꢁ1ꢁz
3.003
3.003
2.940
ꢁ0.067
ꢁ0.067
ꢁ0.100
ꢂ
ꢁx, 1ꢁy,
ꢁ
1ꢁz
1
ꢂ
¼90ꢃ
Unit cell dimensions
a¼13.324(3) A
a
ꢂ
ꢃ
b¼16.067(2) A
b¼97.778(13)
ꢂ
¼90ꢃ
c¼5.3951(7) A
g
ꢂ
3
Acknowledgements
Volume
Z
Density (calculated)
Absorption coefficient
F (000)
1144.3(3) A
4
3
1.487 Mg/m
0.882 mm
536
The authors thank the AECID (A/026355109) and DGICYT (MAT
009-14564-C04-3) and SCSIE from Universitat de Valencia. V.B.
thanks the University of Valencia for a fellowship.
ꢁ
1
2
3
Crystal size
0.80ꢀ0.30ꢀ0.10 mm
ꢃ
q
range for data collection
3.35e64.13
Index ranges
Reflections collected
Independent reflections
Completeness to
Absorption correction
ꢁ15ꢄhꢄ15, ꢁ14ꢄkꢄ18
ꢁ5ꢄlꢄ5
Supplementary data
3854
1720 [R(int)¼0.0696]
89.8%
Semi-empirical from equivalents
q
¼64.13ꢃ
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2012.03.089.
Max. and min. transmission 0.9169 and 0.5387
Refinement method
2
Full-matrix least-squares on F
References and notes
Data/restraints/parameters 1720/0/172
Goodness-of-fit on F2
0.692
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Final R indices [I>2
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Largest diff. peak and hole 0.286 and ꢁ0.352 e A
s
(I)]
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1