Bromine substituted aminonaphthoquinones: Synthesis, characterization, DFT and metal ion binding studies

Article abstract of DOI:10.1039/c6ra20970j

Bromine substituted aminonaphthoquinone ligands viz. 2-(2′-aminomethylpyridyl)-3-bromo-naphthalene-1,4-dione; (2MPA), 2-(3′-aminomethylpyridyl)-3-bromo-naphthalene-1,4-dione; (3MPA), 2-(2′-aminoethylpyridyl)-3-bromo-naphthalene-1,4-dione; (2EPA) and 2-(2′-aminomethylthiophenyl)-3-bromo-naphthalene-1,4-dione (2AMT) and 2-(2′-aminoethylthiophenyl)-3-bromo-naphthalene-1,4-dione (2AET) have been synthesized and characterized by single-crystal X-ray diffraction experiments in conjunction with long range corrected density functional theory. The heterocyclic amines on the naphthoquinone ring render diverse crystal structures. It has been shown that bromine substitution influences the planarity and mutual orientation of naphthoquinone and heterocycles in aminonaphthoquinone ligands. The 2MPA, 3MPA, 2EPA, 2AET aminonaphthoquinone ligands crystallize in the monoclinic space group whereas 2AMT led to the triclinic space group P1. Furthermore, molecular packing of 2MPA and 2EPA revealed dimeric structures while 3MPA and 2AMT are rendered with 'stair-case' arrangements of molecules. 2AET, when viewed down c-axis, showed a 'butterfly like' arrangement. A broad charge transfer band (400-600 nm) was observed in the UV-visible spectra of these ligands. Besides 2MPA and 2EPA exhibit remarkable selectivity toward Cu²⁺ ions, accompanied by a color change from orange to blue in methanol and methanol-water mixture.

Full text of DOI:10.1039/c6ra20970j

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ARTICLE
Bromine substituted aminonaphthoquinones: Synthesis,
Characterization, DFT and metal ion binding studies
†
a
a
b
a
Gunjan Agarwal , Dipali N. Lande , Debamitra Chakrovarty , Shridhar P. Gejji , Prajakta
a
a
a
GosaviꢀMirkute , Amit Patil , Sunita SalunkeꢀGawali*
’
Bromo substituted aminonaphthoquinone ligands viz. 2ꢀ(2 ꢀaminomethylpyridyl)ꢀ3ꢀbromoꢀnaphthaleneꢀ1,4ꢀ
’
’
dione; (2MPA), 2ꢀ(3 ꢀaminomethylpyridyl)ꢀ3ꢀbromoꢀnaphthaleneꢀ1,4ꢀdione; (3MPA), 2ꢀ(2 ꢀaminoethylpyridyl)ꢀ3ꢀbromoꢀ
naphthaleneꢀ1,4ꢀdione; (2EPA) and2ꢀ(2’ꢀaminomethylthiophenyl)ꢀ3ꢀbromoꢀnaphthaleneꢀ1,4ꢀdione (2AMT) and 2ꢀ(2’ꢀ
aminoethylthiophenyl)ꢀ3ꢀbromoꢀnaphthaleneꢀ1,4ꢀdione (2AET) have been synthesized and characterized by the singleꢀ
crystal Xꢀray diffraction experiments in conjunction with the dispersion corrected density functional theory. The
Received 00th January heterocyclic amines on the naphthoquinone ring render diverse crystal structures. It has been shown that bromine
2
0xx,
Accepted 00th January
0xx
substitution influences the planarity and mutual orientation of naphthoquinone and heterocycles in aminonaphthoquinone
ligands. The 2MPA, 3MPA, 2EPA, 2AET aminonaphthoquinone ligands crystallize in monoclinic space group whereas the
2
AMT led to the triclinic space group P-1. Furthermore molecular packing of 2MPA and 2EPA revealed dimeric structures
2
while 3MPA and 2AMT are rendered with ‘stair-case’ arrangements of molecules. The 2AET when viewed down cꢀaxis
showed a ‘butterfly like’ arrangement. A broad charge transfer band 400ꢀ600 nm was observed in the UVꢀVisible spectra of
DOI: 10.1039/x0xx00000x
www.rsc.org/
2+
these ligands. Besides 2MPA and 2EPA exhibit remarkable selectivity toward Cu ions accompanied by color change from
orange to blue in methanol and methanolꢀwater mixture.
recognised that electron attracting or donating substituent’s
1
5
modulate the redox properties of quinones. The molecular basis
of quinone toxicity suggested that enzyme catalyzed reduction to
semiquinone radicals is followed by reduction of oxygen to
Introduction
1
6ꢀ18
superoxide anion radicals
which regenerates the quinone. The
1
,4ꢀnaphthoquinones comprised of an amino or a
electron donor effect of amine substituent on1,4ꢀnaphthoquinones
and the hydrogen bond between the ꢀNH group and quinone
carbonyl groups significantly influences the electron acceptor
substituted amino group, have been focus of attention owing to
their use as therapeutics
1
,2
in a variety of medicinal an3d
biological
antimalarials
applications
encompassing antituberculars ,
19
capability of the quinone nucleus and subsequently electron
4
,5
6
7ꢀ9
anticancer agents , antitumor agents
,
transfer from the analyte to electroactive quinone nucleus. The
presence of nitrogen atom modulates electronic properties of
quinone which further induces structural modification of neutral
molecules or reduction intermediate. Optical characteristics of
quinone derivatives are governed by hydrogen bonding as well as
other intermolecular interactions. The present work aims deriving
the molecular insights accompanying the molecular interactions.
Aminonaphthoquinones owing to their biological
10
11,12
antifungal , antiparasitic and phytotoxic activities.
. The
biological activity of quinones stem from their ability to accept
one or two electrons to form the corresponding radical anion or
dianion species and their acid base behaviour
1
3,14
. It has been
a
Department of Chemistry, Savitribai Phule Pune University, Pune 411007,
Maharashtra, India; Fax: +912025693981 ; Tel:+912025601397 -Ext-531; E-
mail: sunitas@chem.unipune.ac.in
Central Instrumentation Facility, Savitribai Phule Pune University, Pune 411007,
Maharashtra, India
importance serveas chemical sensors. The functionalisation of
1,4ꢀnaphthoquinone with amines facilitate a variety of interaction
sites for metal ion binding. In this regard aminonaphthoquinones
b
2
0
are known to bring about intramolecular charge transfer (ICT)
transitions; the intensity of which largely depends on the
2
1
substituent attached to amine moiety in particular, the charge
density near nitrogen centre. The receptor molecules to be used as
chemosensors should absorb and emit at longer wavelengths and
show selective response to specific ions. It has been conjectured
that the amine moiety being an electron donor group when
present in the quinone ring at C(2) position facilitate a strong
1
13
†
Electronic Supplementary Information (ESI) available:FTꢀIR, H and C NMR, 2D
HSQC, UVꢀvisible spectra are presented in Fig.S1 through Fig.S8. Crystallogray figures
Fig.S9 through Fig.S13. UVꢀvisible spectra of 2EPA in various solvents Fig.S14. Job
plot Fig.S15, Fig.S16. Binding constant Fig.S17, Fig.S18. Competative metal ion
binding studies Fig.S19 through Fig.S21.FTꢀIR Table S1, NMR chemical shifts Table
S2 and S3. Crystallographic Table S4ꢀS23. DFT studies Table S24 through Table S28
CCDC 1446762 for 2MPA, 1446761 3MPA, 1446759 2AMT, 1446760 2EPA and
2
2.23
chargeꢀtransfer
(CT) from the electron donor amine
substituent to the carbonyl group, attributed to intramolecular
hydrogen bonding between carbonyl oxygen and the hydrogen of
1446920 for 2AET
*
the substituent pin C(1) position, which reflects as πꢀπ
absorption band in the visible region of its absorption spectrum.
See DOI: 10.1039/x0xx00000x
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ꢀ
1
ꢀ1
Naphthoquinone and anthraquinone based sensing by
functionalization of the quinone moiety using nitrogen containing
receptors such as amines for cation sensing for example, 1,2 and
vibrations observed at 1292 cm and 1250 ±9 cm in the
aminonaphthoquinones ligands. The ν
largest blueꢀshift of 56 cm for 2AET which decreases steadily
on traversing from 2EPA, 2MPA to 3MPA. The ligand 2AMT,
on the other hand shows a marginal decrease of 4 cm in 2AMT
compared to the 627 cm vibration in parent DBrNQ.
vibration reveals a
CꢀBr
ꢀ
1
2
4,25
1
,8ꢀdiaminoanthroquinoneshas been reported.
To this
incorporated into anthraquinone
as hydrogen bonding receptors have been employed for sensing
26.27
28,29
ꢀ1
direction ureas , thioureas
ꢀ
1
3
0,31
1
13
inorganic and organic anions
those include halide, acetate,
As shown in Scheme 2, H and C chemical shifts
1 13
malate, fumarate, tartarate, aconitate and citrate to distinguish
isomeric forms, since the urea forms strong hydrogen bonds.
Urea anthraquinone assemblies where in the metal cation
deprotonate the donor amine or amide have further been explored
were assigned based on the H,
C, DEPT, gHSQCAD
gDQCOSY experiments (Fig.S3ꢀFig.S7, Table S2 and Table S3
in ESI†).The proton chemical shift of –N(1)ꢀH(1) proton
observed at ~δ = 6.2 ppm in 3MPA, 2AMT and 2AET, however
it showed down field shift signal in 2EPA(δ = 7.12 ppm) as well
3
2
for metal ion detection . Likewise imidazole moiety serves as
33ꢀ35
13
excellent hydrogen bond donor in anion receptor systems
as 2MPA(δ = 7.91 ppm). The C chemical shifts in these ligands
where the reactivity of the NH proton can be tuned by varying the
electronic properties of the substituent at the ring. The presence
of a donor pyridine like nitrogen atom within the ring capable of
selectively binding cationic species converts imidazoles into
are affected significantly as evidenced from 2MPA, 3MPA and
3AMT emerge with the signals near 155.21, 134.11 and 148.99
ppm, respectively. Further 3MPA and 2MPA can be
distinguished from the C(15) and C(16) signals in 3MPA emerge
near δ = 148.99 and 149.18 ppm, respectively.
36ꢀ38
excellent metal ion sensors
. The naphthoquinone based
sensing has been focus of attraction for quite some time. The
naphthoquinone molecules substituted with heterocyclic
The UVꢀvisible spectra of all compounds and the
ꢀ4
starting materials DBrNQ were recorded at 5×10
M
3
9ꢀ43
44
45
amines
, thiourea and imidazole receptors have been
concentrations in DMSO (Fig.S8 in ESI†). The absorption in the
visible region was observed in the starting materials viz. DBrNQ
as well as in 2MPA, 3MPA, 2AMT, 2EPA, 2AET owing to a
2+
reported as sensors for metal cations such as Cu and the anions
as well. It has further been demonstrated that Schiff base of
46
ꢀ
47
aminonaphthoquinone acts as a dual sensor for F anion as well
fully conjugated cyclic dione system , where the πꢀπ* transitions
2+
2+
2+
asCo , Ni , and Cu cations. Naphthoquinone based probes are
are well pronounced in the UV region, sharp intense band near
336 nm of the starting material appears as a only as a hump in the
ligands studied in this work. The nonbonding electrons of the
amino group bring about nꢀπ* transition in the visible region. A
low energy band centred ~440ꢀ477 nm has been observed in the
visible, which is characteristic for the amino substituted quinones
which stem from charge transfer (CT) band and weak nꢀπ*
transitions of the carbonyl of the quinone.
4
4
also being used for sensing biomolecules such as arylamine Nꢀ
acetyltransferase(potential breast cancer biomarker). Bromine
containing chemosensors were scarce in the literature. With our
growing interest to develop naphthoquinone based redox active
chemosensors, in the present work we carried out the syntheses of
naphthoquinone based chemosensors, the thiophene and pyridyl
ring bearing bromo derivatives of 1,4ꢀnaphthoquinone (Scheme
1). These ligands have further been characterized in terms of,
molecular structure and their metal ion binding abilities
combining experiment with the density functional theory.
Scheme 2
Single crystal X-ray diffraction studies
Scheme 1
ORTEP plots of 2MPA, 3MPA, 2AMT, 2EPA and
2AET are shown in Fig.1 and the crystallography data has been
Results and discussion
summarized in Table 1. Except the 2AMT which crystallizes in
triclinic space group P-1,the rest of aminonaphthoquinone
ligands crystallize in monoclinic space group. The oxidation
number of aminonaphthoquinones can be gauged from the bond
The aminonaphthoquinone ligands were synthesized
with high % yield via Michael addition of respective amines to
the starting precursor 2,3ꢀdibromoꢀ1,4ꢀnaphthoquinone(DBrNQ)
as shown in the Scheme S1 in ESI†. There was formation of side
product observed in the synthesis of 2MPA and 3MPA and that
of 2MPA has been isolated and characterized as 2ꢀaminoꢀ3ꢀ
methylꢀ1,4ꢀnaphthoquinone. All the aminonaphthoquinones were
characterized by elemental analysis, FTꢀIR, H, C NMR,
gDQCOSY, DEPT, gHSQCAD NMR and single crystal Xꢀray
diffraction studies.
4
7ꢀ55
distance parameters in quinonoid ring
. The carbonyl bond
distances C(1)ꢀO(1) and C(4)ꢀO(2) are ~1.22Å in all
aminonaphthoquinone ligands except 3AMT the C(4)ꢀO(2)
distance is 1.24(2)Å. Thus, the ligands are in their oxidized form.
The C(3)ꢀN(1) and C(2)ꢀBr
distances respectively, were
1
13
observed to be ~1.32ꢀ1.34Å and ~1.88ꢀ1.90Å.
Aminonaphthoquinones are comprised of CꢀHꢁꢁꢁO, Nꢀ
HꢁꢁꢁO and others include CꢀHꢁꢁꢁN, NꢀHꢁꢁꢁN, CꢀHꢁꢁꢁCl, CꢀHꢁꢁꢁπ,
5
4,55
πꢁꢁꢁπ stacking interactions
. A charge transfer has also been
observed subsequent to these noncovalent interactions. The
chloro analogs containing pyridine functionalities studied in our
laboratory serve as chemosensor, which bind to metal ions via biꢀ
or tri ꢀdentate coordination depending on the planarity of the
FT-IR, NMR and UV-Visible studies
4
8ꢀ49
FTꢀIR spectra of aminonaphthoquinone ligands reveal
ligand.
These chemosensors are known for specific detection
ꢀ
2+
characteristic ꢀNꢀH stretching follows the order: 2EPA (3321 cm
of Cu ions in methanolꢀwater mixture, also are explored to
detect other metal ions under mild basic conditions in the
presence of triethylamine. Xꢀray crystallography experiments
further provide the coordination sites of the ligands. The present
endeavour concerns with how the bromo substitution influences
the planarity of naphthoquinone and the heteroatom rings in
aminonaphthoquinones.
1
1
ꢀ1
ꢀ1
ꢀ
)
)
> 2AMT (3284 cm ) > 3MPA (3267 cm ) > 2AET (3263 cm
ꢀ1
> 2MPA (3242 cm ) and sensitive to inter and intramolecular
hydrogen bonding interactions (cf Fig.S1, Fig.S2 and Table S1 in
ESI†). The carbonyl stretching frequency was observed at 1676
ꢀ
1
cm for the parent starting material DBrNQ, which exhibit a
ꢀ
1
frequency upꢀshift from 2 to 9 cm respectively except for the 2ꢀ
ꢀ
1
EPA in which a marginal shift of 4 cm in the opposite direction
can be noticed. The characteristic paranaphthoquinone (pꢀNQ)
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Intra as well as intermolecular hydrogen bonding interactions
are observed in the aminonaphthoquinone ligands studied in this
investigation. The hydrogen bond parameters including selected
bondꢀ distances and angles are given in Table 2. Except the
The torsion angle C(3)ꢀN(1)ꢀC(11)ꢀC(12) of 2EPA
turns out to be ꢀ94.8° whereas C(13)ꢀC(12)ꢀC(11)ꢀN(1) show a
deviation of ~10° from planarity. Molecules of 2EPA formed a
dimeric synthon via ‘head to head’ interactions through N(1)ꢀ
H(1)ꢁꢁꢁO(2) interactions portrayed in Fig.5. Furthermore the C(5)ꢀ
H(5)ꢁꢁꢁN(2)(ꢀx,1ꢀy,ꢀz) interactions render stability to pyridyl rings
of the dimer. Furthermore as shown in Fig.5 the polymer chain of
dimers are formed through Cꢀ(15)ꢀH(15)ꢁꢁꢁO(1) interactions.
2MPA, the rest of ligands suggest the presence of the N(1)ꢀ
H(1)ꢁꢁꢁO(2) intramolecular hydrogen bonding. The N(1)ꢀ
H(1)ꢁꢁꢁN(2) along with intramolecular H(1)ꢁꢁꢁBr(1) (2.515Å)
interactions are inferred in 2MPA. The bond angle ∠N(1)ꢀ
H(1)ꢁꢁꢁO(2) was observed to be ~ 114°, which shows a closure to
2
~105° in 3AMT compared to that for the sp amino nitrogen.
Fig.5
The intermolecular interactions with similar neighbouring
molecules, type of interaction and interplanar angles of
naphthoquinone ring with pyridine/thiophene ring are represented
in Table 3.
The torsion angle C(3)ꢀN(1)ꢀC(11)ꢀC(12) in 2AET is
83° and C(13)ꢀC(12)ꢀC(11)ꢀN(1) is 175°. Molecules of 2AET
facilitate polymeric chain through N(1)ꢀH(1)ꢁꢁꢁO(1) interactions
in addition to the C(14)ꢀH(14)ꢁꢁꢁBr(1) interactions. As shown in
Fig.6a, the polymeric chains of 2AET molecule further reveal Cꢀ
Hꢁꢁꢁπ interactions between benzenoid and thiophene rings, in
Fig.1
Table 1
particular
C(7)ꢀH(7)ꢁꢁꢁC(15)(3.61(3),
ꢀ1/2+x,1/2ꢀy,ꢀ1/2+z)
Table 2
interactions. When viewed down cꢀaxis (Fig.6b) the ‘butterfly
like’ arrangement can be noticed (with bromines = eyes, ethyl
thiophene = tentacles and naphthoquinone = wings of the
butterfly).
Table 3
Molecular interactions in 2MPA, 3MPA, 2AMT and 2EPA,
2AET’
Fig.6
The usual NꢀHꢁꢁꢁO intramolecular hydrogen bonding
Overlay Structures of 2MPA, 3MPA, 2AMT and 2EPA,
2AET
interaction is absent in 2MPA, instead the orientation of pyridyl
ring brings –NH proton vicinity of bromine facilitating NꢀHꢁꢁꢁN
intramolecular hydrogen bonding interactions. The dimer is
facilitated through head to tail orientation of 2MPA molecules via
C(5)ꢀH(5)ꢁꢁꢁO(2) (ꢀx,ꢀy,1ꢀz) interactions which subsequently
brings about the C(14)ꢀH(14)ꢁꢁꢁO(1) intermolecular hydrogen
bonding interaction(Fig.2) concomitant to Brꢁꢁꢁπ interactions
from neighbouring molecules specially by C(6) (3.517(8) Á, ½ꢀx,
Fig. 7 displays the orientation of pyridyl and thiophene
rings with the naphthoquinone. In 2MPA(Fig.7a) pyridyl ring is
nearly planar. The 2AMT and 3MPA reveal thiophene and
pyridyl ring oriented respectively, above and below the plane of
the naphthoquinone. A marginal variation in orientations. of
pyridyl and thiophene rings in the overlay structures of 2EPA and
2AET(Fig.7b) can be noticed. It should be remarked here that
ꢀ
½+y, ½ꢀz) and C(7)(3.297(7)Á).
chemosensingability to the metal ions and the biological activity
can be correlated to the ring planarity. The aminonaphthoquinone
ligands here facilitate either bidentate or tridentate coordination
with the metal ion. The tridentate coordination sites through O(2),
N(1) and N(2) is favored over the bidentate coordination in
Fig.2
The quinonoid oxygen O(1) of 3MPA further showed
bifurcated hydrogen bonding (Fig.3a). Polymeric chain of 3MPA
molecules is extended by C(8)ꢀH(8)ꢁꢁꢁO(2) and N(1)ꢀH(1)ꢁꢁꢁO(1)
interactions, with the pyridine moiety being placed on same side
of the chain (Fig.3a). The pyridyl rings of two neighbouring
chains orient in opposite directions with the polymer chains
stacked via C(1)ꢁꢁꢁO(2) (3.161(4), x,ꢀ1+y,z) contacts (Fig.3a). The
CꢁꢁꢁO stacked chains are further stabilized by the C(16)ꢀ
H(16)ꢁꢁꢁO(1)(x,ꢀ1+y,z)
interaction(Fig.3b). Pyridyl ring distances were observed to be
.047Å.
2MPA. On the other hand for 2EPA, the structure with the
additional –CH , one of the nitrogen N(2) will be further away
2
from O(2) and N(1) the bidentate coordination is preferred.
Fig.7
Hirshfeld surfaces
and
C(14)ꢀH(14)ꢁꢁꢁBr(1)(1ꢀx,ꢀy,2ꢀz)
To probe various molecular interactions, Hirshfeld
4
surfaces and their associated 2D finger print plots were derived
56
with the use of Crystal Explorer 3.1 employing the single
crystal Xꢀray data. The function dnorm is a ratio encompassing the
distances of any surface point to the nearest interior (di) and
Fig.3
TheC(3)ꢀN(1)ꢀC(11)ꢀC(12) dihedral angle in 2AMT
57ꢀ59
exterior (de) atom to the van der Waals radii of the atoms
.
turns out to be 73.3(4)°, which suggests the thiophene ring is
above the plane of naphthoquinone ring. The crystal network in
the 2AMT extends via headꢀtoꢀtail C(8)ꢀH(8)ꢁꢁꢁO(2) and N(1)ꢀ
H(1)ꢁꢁꢁO(1) interactions. A “stair-case like” polymeric chains
with the thiophene rings separated by C(15)ꢀ(H15)ꢁꢁꢁO(1)(ꢀ1+x,ꢀ
Figure 8a through 8d display surfaces those have been mapped
with the dnorm, shape index, curvedness and finger print plots of
aminonaphthoquinone ligands. For the crystal structure of the
hitherto ligands the Hirshfeld surface is unique and provide detail
insights of the crystal structure. A direct visual comparison
imparts intense red color around the NꢀH substituent of the
ligands which contribute largely toward NꢀHꢀꢀꢀO interactions (cf.
Figure 8a) except for the 2MPA. In addition to this CꢀHꢀꢀꢀO
contacts are be deciphered through the intense red spots within
1
+y,z) interactions down the bꢀaxis can further be noticed from
Figs.4a and 4b. As shown the slipped πꢀπ stacking have also been
inferred along polymeric chain down the aꢀaxis (Fig.4a), in
particular the benzenoid and quinonoid rings are stacked through
C(9)ꢁꢁꢁC(5)(3.66(1)Å) and C(7)ꢁꢁꢁC(4)(3.69(1)Å) contacts.
2EPA, 2MPA and 2AMT. The characteristic packing modes and
the ways in which the nearby molecules contact one another
further gauged through shape index and curvedness parameters.
Fig.4
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1
The shape index of all the molecules shows a red concave region
on the surface around the oxygen atoms as well as π cloud of
aromatic rings and a blue region around the hydrogen atoms. The
presence of CꢀHꢁꢁꢁπ and π-π stacking interactions in
aminonaphthoquinone derivatives further are evident from the
pattern of adjacent red and blue triangles those appear on the
shape index surfaces and relatively large and flat green region on
the same side of the molecule on the corresponding curvedness
surfaces (cf. Figure 8b and 8c). The breakdowns of fingerꢀprint
plots for all such structures are illustrated in Figure 8d. From the
FP plots, contributions from the NꢀHꢁꢁꢁO, CꢀHꢁꢁꢁO, CꢀHꢁꢁꢁπ, Cꢀ
HꢁꢁꢁN and πꢀ π stacking interactions can be segregated. Thus the
volume (V ), area (S ), globularity (G) and asphericity (ꢂ)
Table S25). The C(1)O(1) carbonyl stretching at 1651cm in
ꢀ1
2AMT shifts to 1641cm in the calculated vibration spectra of
2AET. As opposed to this the carbonyl stretching at the 1640 cm
in 2MPA shifts to higher wave number 1649 cm in the 3MPA
isomer. The aromatic proton shows a band ~2988 cm . The
inferences borne out from the present DFT calculations are also
ꢀ
1
ꢀ1
ꢀ
1
in consonance with the experimentally measured spectra.
1
H NMR chemical shifts (δ ) in 2MPA, 2AMT, 3MPA,
H
2EPA and 2AET in DMSO (as solvent) were simulated through
the SCRFꢀPCM theory. A comparison with the experiment is
given in Table S26. The H(1) proton participating in NꢀHꢁꢁꢁBr
interactions in 2MPA emerge with relatively large deshielding
(8.3 ppm) in the spectra. The signals of the corresponding proton
in the rest of aminonaphthoquinone derivatives facilitate the Nꢀ
H
H
parameters based on hirshfield surfaces have been calculated. The
6
0
following inferences are drawn. The term, globularity was
observed at ~0.764 for the aminonaphthoquinone derivatives
which suggest that the molecular surface is more structured, and
HꢁꢁꢁO interactions and appear at ~6.8 ppm. The alkyl protons
1
emerge with upꢀfield δ
H
signals in the calculated H NMR. These
inferences on the calculated
experiment.
δ
H
values concur with the
6
1,62
not a sphere. The asphericity
that provides measure of
anisotropy follows order : 2EPA (0.385) > 2AET (0.357) >
Frontier orbitals HOMO and LUMO (isosurface of
±0.04 au) in the aminonaphthoquinone ligands are portrayed in
Fig.12, Fig.13. The complimentarily in charge distributions
between HOMO and LUMO is transparent for 3MPA, 2AMT and
2MPA (0.317) > 3MPA (0.163) > 2AMT (0.136).
Fig.8
2AET. Here the HOMO extends over the entire molecule. On the
other hand, in 2MPA and 2EPA it has been largely localized near
naphthoquinone framework. The electronic spectra in the
presence of methanol were obtained using the TDꢀDFT theory.
The wavelength maxima, oscillator strengths and orbital
descriptors are summarized in Table S27. It is transparent that
the absorption band arising from the HOMO to LUMO transition
shows up near ~402 nm. The HOMOꢀLUMO energies, global
indices of reactivity viz., chemical potential (ꢃ), hardness (η),
electrophilicity (ω) of amino naphthoquinone derivative and its
anionic form are summarized in Table S28. A large separation
of HOMO and LUMO energies (ΔE) in the molecule imply the
reluctance toward the acceptance of electron in the LUMO while
the removal of an electron from the HOMO renders electronic
stability to the system. A large relative stability of 3MPA and
DFT Investigations
Optimized
structures
of
aminonaphthoquinone
derivatives from the wb97x based density functional theory are
depicted in Fig.9. Selected bondꢀ distances and angles are
compared with Xꢀray crystal data in Table S24. Except for the
NH bond bridging naphthoquinone and substituted pyridine
moiety of 2MPAwhich is up to 0.22 Å longer the overall
structural parameters agree well with those from the Xꢀray
experiments. A comparison of 2MPA and 2AMT shows that
carbonyl C(1)O(1) bond distances are shortened on substituting
the thiophene instead of pyridine. It may readily be discernible
that an increase of alkyl chain from methylene to ethylene
engenders the reversal of the trend and accordingly longer C=O
bond distances are predicted for 2AET compared to the 2EPA.
These inferences are consistent with those observed from the Xꢀ
ray crystal structure data. The bond angles show deviation
maximally up to 2° compared to the Xꢀray crystal structures.
The structures of aminonaphthoquinone derivative
2AET is thus evident. The anionic forms of these emerge with the
lower band gap energies relative to the corresponding neutral
systems.
To delve further in metal coordination we derive the
2+
structure of the Cu ꢀ2MPA complex, as a test example. As
pointed out earlier the HOMO (isosurfaces of 0.04 a.u.) of
2MPA largely resides on quinonoid ring of naphthoquinone
anions are also obtained within the framework of ωb97x/6ꢀ
moiety which on complexation extends over to the metal ion as
shown in Fig. 14. The ligand to metal charge transfer, therefore
can be inferred. These conclusions further may as well be
extended to other metal complexes studied in the present work.
Fig.9
31+G(d,p) theory which are portrayed in Fig.10. Selected bond
distances are given along with. As may readily be noticed the
anions reveal longer C=O or CꢀBr bond distances compared to
their neutral analogs with the elongation up to ~0.0238 Å was
predicted for 2MPA.
Structural ramifications in calculated vibration
frequencies and accompanying molecular interactions can be
probed through normal vibration analysis. Calculated frequencies
of 2MPA, 2AMT, 3MPA, 2EPA and 2AMT with those measured
in the experiment are compared in Table S25 and portrayed in
Fig.10
Fig.11
Fig.12
Fig.13
Fig.14
ꢀ
1
Fig.11(a) and 11 (b). The NꢀH stretching assigned to 3242 cm of
MPA engenders a large frequency up shift that amounts to ~73
2
ꢀ
1
cm on substitution of the ethyl group insteadof methyl as
in2EPA. The change of position of naphthoquinone to the 3
position of pyridine (in 3MPA) renders a blueꢀshift (upꢀshift) for
ꢀ
1
the NꢀH stretching (3283 cm ) vibration. A comparison of
AMT and 2AET further led to similar inferences. The effect of
2
pyridine or thiophene substitution on amino naphthoquinone
derivative shows its signature in NH stretching vibration which
shows the corresponding frequency shift in the opposite
directions in the methyl and ethyl substituted derivatives (cf
Chemosensor evaluation Studies
The metal ion binding studies of all the ligands have
been carried in methanol, methanolꢀwater mixture and in
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ARTICLE
presence of triethylamine. It has been observed that only 2MPA
and 2EPA showed colour change with specifically with few metal
ions. The colour of the ligand solution changed usually due to the
formation of metal complexes. Metal ions induced the
deprotonation of –NH and create the legating sites. The extra
stability of 3MPA and 2AET ligands do not favour the formation
metal complexes at room temperature (26°C), thus there is no
colour change was observed with the solvents used for this
studies in present investigation.
Visual detection of metal ions in methanol-triethylamine
The deprotonation of NꢀH of chemosensor was achieved by
addition of mild base such as triethylamine and thus several metal
ions could bind to the anionic chemosensor and the detectable
colour change could be visualized by naked eyes. In this
experiment, triethylamine was added prior to the addition of the
2+
2+
2+
metal ion solution, wherein only Cu , Ni and Co caused a
colour change in 2MPA (Fig.16b and Fig.17b). A new band
2+
2+
2+
2+
appeared in 600ꢀ800 nm for Cu , Ni , Zn , Co in methanol
Fig.18b), after addition of triethylamine. In addition the
enhancement of peak at ~330 nm was observed for most of the
(
Fig.15
2+
metal ions in presence of triethylamine. For Cu this peak was
shifted to 372 nm and 375 nm.
Table 4
Fig.15 showed the UVꢀvisible absorption spectra of
chemosensors 2MPA and 2EPA in methanol, in 1:1(v/v)
methanolꢀwater in the absence and presence of a mild base
triethylamine (TEA) while Fig.17 showed the UVꢀvisible spectra
of the chemosensor 2MPA in the presence of transition metal
ions in different solvents (The UVꢀvisible spectra of for 2EPA
are shown in Fig.S14 in ESI†). Table 4 showed the respective
maximum absorption wavelength which shows λmax at 455 nm in
case of 2MPA and 468 nm for 2EPA in methanol which
undergoes bathochromic shifts in other solvents (bathochromic
shift in presence of water ~475 nm and hyposochromic shift in
triethylamine. In UV region of the spectrum, the peak ~331 nm is
observed only in triethylamine while for other mixture of solvents
only a hump was observed, which was assigned to πꢀπ*
transition.
Visual detection of metal ions in methanol-water
2+
In 1:1 mixture of methanol: water, only Cu showed colour
change from orange to dark blue for 2MPA and dark green for
2
EPA (Fig.16c and Fig.17c). The colour change observed for
2+
Cu in pure organic solvent was (pale green) and it varied in
presence of water. Thus Chemosensor 2MPA effectively
2
+
differentiated the organic and aqueous media for Cu ions. The
visible absorption band of Chemosensor 2EPA appeared at λmax
2+
4
77 nm which on addition of Cu (1:1) underwent an immediate
visible colour change from orange to dark brown. Both
chemosensors 2MPA and 2EPA did not undergo any colour
2+
2+
2+
3+
change on addition of other metal ions like Ni , Zn , Co , Fe ,
2+
3+
2+
3+
2+
Mn , Cr , Hg , La and Cd in 2EPA in methanolꢀwater
mixture.
Metal ion binding studies
Visual detection of metal ions methanol-water-triethylamine
Metal ion binding studies were carried out in the
following solvent systems, i) in methanol, ii) in 1:1(v/v)
methanolꢀwater, iii) in presence of a mild base triethylamine
With the introduction of triethylamine to the methanolꢀwater
mixture Mn and Co showed variable colour shades for the
respective solutions (Fig.16d, Fig.17d). The UVꢀvisible spectra
Fig.18d) showed complete absence of the band in the ranges
00ꢀ800 nm and an enhancement of intensity of πꢀπ* transition
band at ~362 nm in the methanolꢀwaterꢀtriethylamine mixture.
2+
2+
(
TEA) in i) and ii) TEA was used to get the deprotonated form of
(
6
the chemosensor ligands which can be used to detect other metal
ions too. In typical experiments 2 ml of the chemosensor was
mixed with 2 ml of metal ion solutions at room temperature (26
°C) and 1 ml of triethylamine was added in chemosensor solution
in case of i) and ii) prior to the addition of metal ion solutions.
UVꢀvisible spectra of all solutions was measured using a typical
Stoichiometry, affinity constant, competitive binding of metal
ion of 2MPA and 2EPA
ꢀ4
concentration of 10 M. Photographs (Fig.16 for 2MPA, Fig.17
ꢀ3
for 2EPA) were obtained for 10 M solutions of the chemosensor
2
+,
2+,
2+,
2+,
3+,
2+,
3+,
2+,
3+
The binding stoichiometry of 2MPA and 2EPA
and metal ions (Cu Ni Zn Co Fe Mn Cr Hg La
and Cd ).
2
+
2+
2
+
(Fig.18) with Cu , Ni was determined by Job plot method.
2+
With 2MPA it is found to be 1:1 for Cu ions in methanol,
2
+
methanolꢀwater while it is 2:1 for Ni in methanol (Fig.19) and
Fig.16
2+
for Cu in methanolꢀwaterꢀtrimethylamine mixture (Fig.S15).
2
+
For 2EPA the stoichiometry was observed as 1:1 for Cu in
methanol, methanolꢀtrimethylamine and methanolꢀwater solvent
Fig.17
mixture (Fig.S16).
.
Fig.18
2
+
The binding constant of Cu ion has been determined
Fluorescence measurement) by SternꢀVolmer plot (Fig.S17 and
(
Visual detection of metal ions in methanol
Fig.S18) in methanol. The concentration of 2MPA/2EPA and
ꢀ
4
metal ion used for this experiment are respectively (5*10 ) and
The orange color solutions of 2MPA and 2EPA showed
colour changes on the addition of Cu , Ni and ions in 2MPA
Fig.16a) while 2EPA could differentiate colour change in
ꢀ
3
2+
2
+
2+
(1*10 M). The association constant (Ka) value obtained for Cu
ꢀ1 ꢀ1
was found to be 851 M for 2MPA and 6079 M for 2EPA
In the competitive binding of metal ions, in a typical
(
+
2+
Cu (blue) and Cu (dark green) (Fig.17a). The solutions of
ꢀ
4
2
+
2+
2+
2+
experiments 2MPA and 2EPA (5*10 M) was mixed with equal
2+ 2+ 2+ ꢀ4
Mn , Co and Zn of 2MPA and Ni become dark, while there
is no observable colour change was seen for the other metal ions.
The colour change was observed due to formation of coordination
complexes by deprotonation of NꢀH of the chemosensor ligand.
volume of Cu , Ni and Co (5*10 M). Noticeable colour
changes occur in solution mixture of metal ions (Fig.S19) for
2MPA and 2EPA as well as in UVꢀvisible and fluorescence
spectra of selected metal ion (Fig.S20 for 2MPA and Fig.S21 for
A new band was noticed for respectively at λ to 601 nm and
max
2
+
2
+
2EPA). Cu showed significant fluorescence quenching in both
6
20 nm for Cu solution.
2MPA and 2EPA while other metal ion only cause small changes
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R
d
S
o
C
no
A
t
d
a
v
d
a
ju
n
s
c
t
e
m
s
argins
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Journal Name
in fluorescence intensity. It was observed in competitive
ARTICLE
about 15 min. To this solution 1 mM, corresponding amines (1
mM = 0.104 ml of 2ꢀpicolylamine, 0.0103 ml 3ꢀpicolylamine,
0.126 ml of 2ꢀaminoethylpyridine, 0.103 ml of 2ꢀ
thiophenemethylamine, 0.120 ml of 2ꢀthiopheneethylamine) were
added drop wise. The reaction mixture was stirred for 24 hours at
room temperature (26°C) with constant magnetic stirring till
completion of the reaction monitored on TLC. The reaction
mixture was evaporated under reduced pressure and the residue
was column chromatographed over silica gel in methanol/toluene
2
+
2+
experiment, the Ni and Co competed to bind with 2MPA and
2+
2
EPA, however Cu dominate all other metal ion because of
higher binding constant.
Fig. 19
Conclusions
(1:9) system. The orange color solid products were obtained after
The aminonaphthoquinones containing different
evaporation of pure fraction from the column. In case of 2MPA a
light orange color fraction was obtained other than the main
product which was characterized as 2ꢀbromoꢀ3ꢀmethylꢀ1,4ꢀ
naphthoquinone.
heterocyclic amines were synthesized and characterized. Diverse
crystal network patterns have been noticed for differently
substituted heterocyclic rings. 2AMT and 3MPA reveal the
thiophene and pyridyl rings near normal to naphthoquinone ring
whereas the 2MPA shows pyridyl ring orients near planar
facilitatingtridentate coordination to metal ion(s). A bidentate
coordinationis preferred in case of 2EPA which can be attributed
Characterization
’
to an increased separation between NꢀH and pyridyl nitrogen..
2-(2 -aminomethyl)pyridyl-3-bromo-naphthalene-1,4-dione;
The separation being expected to be further increase in 2AET
2MPA
compared to 2EPA.The aminonaphthoquinone ligands possess a
variety of hydrogen bonding in addition to those arising from Cꢀ
Hꢁꢁꢁπ and πꢀπ stacking interactions. The close proximity of
pyridyl ring and –NH proton to Br atom in the 2MPA engenders
Dark orange crystals. Yield: 0.222 g (65%). m.p.:132ꢀ135°C.
Anal. Data calcd. for C16 Br (%): C, 55.99; H, 3.23; N,
8.16. Found(%): C, 55.83; H, 3.27; N, 7.95. FTꢀIR (KBr,
11 2 2
H O N
1
ꢀ
1
the largely deshielded (8.3 ppm) signal in H NMR spectra
ν
max(cm )): 3242, 3061, 1680, 1601, 1564, 1493, 1435, 1327,
compared to the rest of the ligands; the inference which has been
corroborated by the DFT computations.2MPA and 2EPA can be
1
6
292, 1250, 1207, 1134, 1039, 1001, 895, 829, 787, 758, 723,
1
3
79, 638, 573, 542, 489, 449. H NMR (CDCl , 499.81 MHz,
2
+
used for naked eye detection of Cu from organic and aqueous
media with the remarkable selectivity.
δ(ppm)): 8.65 ( d, J = 4.50 Hz, 1H, Ar) 8.16 (d, J = 7.50 Hz,
H,Ar), 7.72 (m, 2H, Ar), 7.64 (t, J = 7.50 Hz, 1H, Ar), 7.30 (d, J
8.00 Hz, 1H , Ar), 7.27 (t, J = 6.25 Hz, 1H, Ar), 7.91 (s, 1H, ꢀ
1
=
13
NH), 5.21 (d, J = 5.00 Hz, 2H). C NMR (CDCl
δ(ppm)): 49.21, 121.97, 122.87, 127.02, 127.15, 130.00, 132.54,
32.59, 134.89, 137.11, 146.50, 149.18, 155.21, 176.50, 180.54.
3
, 125.69 MHz,
Experimental Section
1
General Materials and Methods
UVꢀVis, (λmax, DMSO (nm)): 467.
Chemicals and reagents viz. 2ꢀ3ꢀdibromoꢀ1,4ꢀ
napthoquinone (DBrNQ), 2ꢀpicolylamine, 3ꢀpicolylamine, 2ꢀ
’
2
3
-(3 -aminomethyl)pyridyl-3-bromo-naphthalene-1,4-dione;
MPA
(
(
2’ꢀaminomethyl)thiophene, 2ꢀ(2’ꢀaminoethyl)pyridine, 2ꢀ
2ꢀaminomethyl)thiophene used were purchased from
Orange brown crystals. Yield: 0.301 g (88%).m.p.: 140.83°C.
Anal. Data calcd. forC16 Br (%): C, 55.99; H, 3.23; N,
.16. Found(%): C, 56.46; H,2.86; N, 8.37.FTꢀIR (KBr, νmax(cm
): 3267, 3109, 3022, 2951, 2602, 2260, 1955, 1684, 1631, 1595,
512, 1473, 1425, 1329, 1300, 1246, 1128, 1063, 1028, 964, 860,
17.54, 678, 634, 540, 499, 445. H NMR (CDCl
δ(ppm)): 8.62 (s, 1H, Ar), 8.57 (d, J = 4.50 Hz, 1H, Ar), 8.12 (d,
J = 7.50 Hz, 1H, Ar), 8.01 (d, J = 8.00 Hz,1H Ar), 7.70 (m, 2H,
Ar), 7.64 (t, J = 8.00 Hz,1H, Ar), 7.33 (t, J = 6.50 Hz,1H,Ar)
6.28 (s, ꢀNH ), 5.11 (d, J = 6.50 Hz 2H, ꢀCH
25.69 MHz,δ(ppm)): 46.73, 124.06, 126.94, 127.21, 127.37,
29.98, 132.27, 132.91,133.98, 135.12, 135.57, 146.36, 149.16,
49.435, 176.75, 180.08. UVꢀVis, (λmax, DMSO (nm)): 471.
SigmaꢀAldrich and used as received. The solvents used such
as dichloromethane, toluene, methanol are of analytical
11 2 2
H O N
ꢀ
8
grade were purchased from Merck Chemicals. CuCl
2
.2H
2
O,
1
)
NiCl .6H O, ZnCl2, CoCl .6H O HgCl2, triethylamine,
2
2
2
2
1
7
methanol and dichloromethane were obtained from Merck
chemicals. FeCl .6H was obtained from Qualigens
Chemicals. CrCl .6H O, CdSO , MnCl .4H O was obtained
from Fluka. LaCl .7H O was obtained from Thomas and
Baker. MilliꢀQ water was used for preparation of aqueous
1
3
, 499.81 MHz,
3
2
O
3
2
4
2
2
3
2
13
6
3
2
). C NMR (CDCl
3
,
solutions. Solvents were distilled by standard methods and
dried wherever necessary. Melting points of compounds was
determined using melting point apparatus (Makeꢀ
METTLER). The FTꢀIR spectra of all ligands was recorded
1
1
1
ꢀ1
between 4000ꢀ400 cm as KBr Fig.S1, Fig.S2 and Table S1
1
in ESI†) pellets on BRUKER Tensor 37 Spectrometer. H,
’
1
3
2-(2 -aminomethyl)thiophenyl-3-bromo-naphthalene-1,4-
dione; 2AMT
C, DEPT, HSQC, COSY NMR of all compounds were
recorded (Fig.S3 and Fig.S7 Table S2 and Table S3 in ESI†)
in DMSOꢀ , on Varian 500 MHz NMR instrument. TMS
tetramethylsilane) was used as the reference. UVꢀVisible
spectra of all ligands in CDCl was recorded from 200 nm to
00 nm on Shimadzu UV 1800 spectrophotometer (Fig.S8 in
d
6
°
Dark brown crystals. m. p.: 119.79 C. Yield: 0.337 g (97%).
Anal. Data calcd. for C15
.022, S, 9.21. Found C, 52.12; H, 2.87; N, 4.31; S, 8.67. FTꢀIR (
KBr, νmax(cm )): 3462, 3284, 3194, 3109, 3043, 3012, 2966,
920, 2850, 2594, 2455, 2283, 2083, 1990, 1894, 1867, 1685,
633, 1570, 1510, 1431, 1300, 1244, 1153, 1126, 1057, 1026,
60, 835, 781, 705, 623, 542, 447, 408. H NMR (CDCl , 499.81
(
10 2
H O NSBr(%): C, 51.73; H, 2.89; N,
3
4
8
ꢀ
1
ESI†). Elemental analysis was performed on Thermo
Finnigan EA 1112 Flash series Elemental.
2
1
8
1
3
Synthesis
MHz, δ(ppm)): 8.14 (d, J = 7.50 Hz, 1H, Ar), 8.03 (d, J = 7.00
Hz, 1H, Ar), 7.72 (t, J = 7.74 Hz, 1H, Ar), 7.64 (t, J = 7.50 Hz,
1H, Ar), 7.29 (t, J = 5.00 Hz, 1H, Ar), 7.07 (d, J = 3.00 Hz, 1H,
1
mM of 2ꢀ3ꢀdibromoꢀ1,4ꢀnapthoquinone (0.315 g) was
dissolved in 15 ml of dichloromethane and the mixture stirred for
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Page 7 of 57
Journal Name
Ar), 7.00 (t, J = 4.25 Hz 1H, Ar), 6.10 (s,ꢀNH), 5.25 (s, 2H, ꢀ
RSC Advances
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ARTICLE
empirical absorption correction for intensity data were carried out
by Bruker SADABS. The programs are integrated in APEX II
1
3
CH ). C NMR (CDCl , 125.69 MHz, δ(ppm)): 44.06, 125.91,
2
3
64
126.59, 126.74, 126.97, 127.09, 127.20, 129.86, 132.16, 132.65,
package. The data were corrected for Lorentz and polarization
1
34.86, 140.10, 146.00, 176.20, 180.00. UVꢀVis, (λmax, DMSO
effect. The structure was solved by Direct Method using SHELXꢀ
65
(
nm)): 463.
97. The final refinement of the structure was performed by fullꢀ
matrix leastꢀsquares techniques with anisotropic thermal data for
’
2
2
2
-(2 -aminoethyl)pyridyl-3-bromo-naphthalene-1,4-dione;
EPA
nonꢀhydrogen atoms on F . The nonꢀhydrogen atoms were
refined anisotropically whereas the hydrogen atoms were refined
at calculated positions as riding atoms with isotropic
displacement parameters. Molecular diagrams were generated
Dark red crystals, Yield: 0.342 g (96%). m. p: 127.60°C. Anal.
Data calcd. for C17 Br(%): C, 57.16; H, 3.66; N, 7.84.
Found(%): C, 57.21, H, 3.78, N, 7.47. FTꢀIR (KBr, νmax(cm )):
6
6
67
H
13
O
2
N
2
using ORTEPꢀ3
and Mercury programs.
Structural
6
5
68
ꢀ
1
calculations were performed using SHELXTL and PLATON .
3
1
7
321, 3192, 3032, 3003, 2937, 2875, 1992, 1892, 1672, 1610,
525, 1446, 1330, 1296, 1257, 1157, 1130, 1074, 1022, 993, 954,
86, 758, 727, 686, 653, 542, 497, 420. H NMR (CDCl
1
DFT Studies
3
, 300
69
Optimized structures were derived using the wB97x
based density functional theory employing the Gaussianꢀ09
MHz, δ(ppm)): 8.59 ( d, J = 5.00 Hz, 1H, Ar), 8.13 (d, J = 7.00
Hz, 1H, Ar), 8.00 (d, J = 7.00 Hz, 1H, Ar), 7.58ꢀ7.70 (m, 3H,
Ar), 7.21 ( d, J = 8.49 Hz, 1H, Ar), 7.18 (t, J = 3.75 Hz, 1H, Ar),
7
0
program. The internally stored 6ꢀ31G basis set with diffuse
functions added to on all the heavy atoms (designated as 6ꢀ
7
3
3
1
.12 (s, 1H, ꢀNH ), 4.32 (q, J = 6.33 Hz, 2H, ꢀCH ), 3.17 (t, J =
2
13
71
31+G(d,p) basis) have been used for optimizations. The
stationary point structures thus obtained were confirmed to be
local minima on the potential energy surfaces through vibrational
frequency calculations. Frontier orbitals were computed in the
same framework of theory.Time dependent Density Functional
Theory (TDꢀDFT) was employed to derive the electronic
spectra.To understand a charge transfer accompanying the
metal coordination we carried out computations on the Cu
complex of 2MPA as a model example.
2 3
.75 Hz, 2H, ꢀCH ). C NMR (CDCl , 125.69 MHz, δ(ppm):
8.05, 44.69, 122. 09, 123.65, 126.97, 127.13, 130.20, 132.44,
32.58, 134.86, 137.04, 146.60, 158.65, 176.31, 176.10, 180.45.
UVꢀVis, (λmax, DMSO (nm)): 477.
’
2
2
-(2 -aminoethyl)thiophenyl-3-bromo-naphthalene-1,4-dione;
AET
°
Dark brown crystals. m.p.: 115ꢀ116 C. Yield: 0.347 g (96%),
Anal. Data calcd. for C16
12 2
H O NSBr(%): C, 53.05 ; H, 3.33; N,
Metal ion binding studies, Jobs Plot and Competitive binding
experiment
3
.86; S, 8.85. Found (%): C, 53.25; H, 3.47; N, 3.93; S, 8.58.FTꢀ
ꢀ
1
IR (KBr, νmax(cm )) : 3263, 3063, 2960, 1857, 1674, 1610, 1541,
1
1
4
7
3
440, 1438, 1261, 1255, 1016, 603, 540, 495. H NMR (CDCl ,
99.81 MHz, δ(ppm)): 8.15 (d, J = 7.50 Hz, 1H, Ar), 8.02 (d, J =
.50 Hz, 1H, Ar), 7.72 (t, J = 7.50 Hz, 1H, Ar), 7.63 (t, J = 7.25
Metal ion binding studies were evaluated by following
methods, (i) in methanol solution of chemosensor and metal ions
ꢀ
4
ꢀ4
(
(
1*10 ) (ii) 1*10 M solution of (i) in presence of triethylamine,
ꢀ4
Hz, 1H, Ar), 7.20 (d, J = 4.99 Hz, 1H, Ar), 6.97 (t, J = 4.25 Hz,
iii) methanol (chemosensor (1*10 M) and water (metal ion,
1H, Ar). 6.92 (d, J = 4.99 Hz, 1H, Ar), 6.18 (s, 1H, ꢀNH), 4.18 (q,
ꢀ
4
ꢀ4
13
1*10 M) mixture and (iv)1*10 M solution of (iii) in presence
of triethylamine. In all methods 2 ml of chemosensor was mixed
with 2 ml of metal ion solution at room temperature (26 ⁰C). 1 ml
triethylamine was added in chemosensor solution in case of (ii)
and (iv) prior to addition of metal ion solution. UVꢀvisible and
fluorescence spectra of all solution were measured.
J = 6.66 Hz, 2H, ꢀCH
2
), 3.23 (t, J = 6.25 Hz, 2H, ꢀCH
2
),
C
NMR (CDCl
3
, 125.69 MHz, δ(ppm)): 31.45, 46.50, 124.72,
1
1
4
26.19, 127.12, 127.31, 127.41, 130.01, 132.51, 132.67, 135.05,
40.03, 146.50, 176.60, 180.23. UVꢀVis, (λmax, DMSO (nm)):
72.
Micro molar concentration (10ꢀ100 ꢃM) of
X-Ray Crystallographic Data Collection and Refinement of
the Structures
chemosensor and metal ion were used for Jobs plot experiment.
Solutions were prepared by varying concentration of
2
+
chemosensor and metal ions. Binding constant of Cu ion was
The Xꢀray quality red crystals of 2MPA, 3MPA,
ꢀ
4
determined by SternꢀVolmer plot. 5*10
M solution of
2AMT, 2EPA and 2AETwere obtained after evaporation of red
ꢀ
3
chemosensor and 1*10 M metal ion solution in methanol were
used to obtain the same.
For competitive binding of metal ions (5*10 M) with 2MPA
and 2EPA (5*10 M) equal volume were mixed and UVꢀvisible
spectra of all solution were measured
pure fraction from the column. Crystals of appropriate size were
chosen for data collection.
Data for all three compounds have been collected on
D8 Venture PHOTON 100 CMOS diffractometer using graphite
ꢀ
3
ꢀ
3
monochromatized MoꢀK
frame = 10 secs for 2MPA and 3MPA, 15secs for 2AMT, 20secs
for 2EPA respectively whereas CuꢀK radiation (1.5406 Å) with
α
radiation (λ = 0.7107 Å) with exposure
/
Acknowledgements
α
exposure/frame = 12 secs for 2AET respectively has been used.
The Xꢀray generator was operated at 50 kV and 30 mA for Moꢀ
K radiation and at 50 kV and 1 mA for CuꢀK . An initial set of
α α
cell constants and an orientation matrix were calculated from
total 24 frames and 60 frames for Mo and Cu source respectively.
The optimized strategy used for data collection consisted
SSG grateful to RGYI scheme of Department of
Biotechnology, New Delhi, India for Ref. No.
(BT/PR6565/GBD/27/456/2012) and Mr. Rishikesh Patil for
NMR spectra.
References
different sets of
ϕ and ω scans with 0.5° steps in ϕ/ω. Crystal to
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Oscillation / frame ꢀ0.5º, maximum detector swing angle = –
1
2
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This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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6
7
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Table 1 Single Crystal Xꢀray data for 2MPA, 3MPA, 3AMT, 2EPA and 2AET
Identification code
2MPA
3MPA
3AMT
1446759
2EPA
2AET
CCDC No
1446762
1446761
1446760
1446920
Empirical formula
Formula weight
C
16
H
11 Br N
2
O
2
C
16
H
11BrN
O
2 2
C
15
H
10BrNO
2
S
C
357.2
17
H
13BrN
2
O
2
16 2
C H12Br NO S
362.24
343.18
343.18
348.21
Temperature
296(2) K
296(2) K
296(2) K
296(2) K
296(2) K
Wavelength
1.54178 Å
0.71073 Å
0.71073 Å
0.71073 Å
1.54178 Å
Crystal system, space
group
Monoclinic, P21/n
Monoclinic, P21/c
Triclinic, P-1
Monoclinic, C2/c
Monoclinic, Cc
Unit cell dimensions
a = 4.9001(3)Å,
b = 14.5285(8) Å
β = 96.875(2)
a = 12.9287(2) Å,
b = 7.70260(10) Å
β= 109.1800(5)
a = 7.3322(2) Å
α = 91.4380(6)
a = 25.2419(4) Å,
b = 4.46860(10) Å,
β= 108.0900(8)
a = 23.3217(11) Å,
b = 4.4264(2) Å,
β = 91.381(3)
o
o
o
o
o
b = 7.7451(2) Å
o
c = 19.5250(10)
c = 14.6188(2) Å
β = 90.0420(7)
c = 27.7323(4) Å
c = 14.6193(7) Å
c = 12.5621(3) Å
o
γ = 96.9860(7)
707.86(3) Å
3
3
3
3
3
Volume
1380.01(13) Å
1375.00(3) Å
2973.47(9) Å
1508.73(12) Å
3
3
3
3
3
Z, Calculated density
Absorption coefficient
4, 1.652 Mg/m
4, 1.658 Mg/m
2, 1.634 Mg/m
8, 1.596 Mg/m
4, 1.595 Mg/m
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
ꢀ1
4.116 mm
688
2.995 mm
3.050 mm
2.773 mm
5.037 mm
F(000)
688
348
1440
728
Crystal size
0.46 × 0.11 × 0.063
mm
3.802 to 68.386
0.256 × 0.241 × 0.193
mm
2.873 to 28.535
0.268 × 0.143 × 0.122
mm
2.650 to 28.396
0.431 × 0.184 ×0.063
mm
3.029 to 28.277
0.180 × 0.119 × 0.103
mm
3.792 to 68.470
o
o
o
o
o
Theta range for data
collection
Limiting indices
ꢀ5 ≤ h ≤ 5, ꢀ17 ≤ k ≤
ꢀ17 ≤ h ≤17, ꢀ10 ≤ k ≤
10, ꢀ19 ≤ l ≤19
ꢀ9 ≤ h ≤ 9, ꢀ10 ≤ k ≤
10, ꢀ16 ≤ l ≤ 16
ꢀ33 ≤ h ≤ 33, ꢀ5 ≤ k ≤
5, ꢀ36 ≤ l ≤36
ꢀ28 ≤ h ≤ 28, ꢀ5 ≤ k ≤
5, ꢀ17 ≤ l ≤ 17
1
7, ꢀ23 ≤ l ≤ 23
Reflections collected /
unique
19383 / 2515[R(int) =
0.1625]
58520 / 3490 [R(int) =
0.0787]
25998 / 3546 [R(int) =
0.0688]
19705 / 3640 [R(int) =
0.0966]
7556 / 2600 [R(int) =
0.0646]
Completeness to theta =
9960 %
99.90%
100.00%
99.90%
99.10%
o
2
5.242
Refinement method
Fullꢀmatrix leastꢀ
squares on F
Fullꢀmatrix leastꢀ
squares on F
Fullꢀmatrix leastꢀ
squares on F
Fullꢀmatrix leastꢀ
squares on F
Fullꢀmatrix leastꢀ
squares on F
2
2
2
2
2
Data / restraints /
parameters
Goodnessꢀofꢀfit on F
2515 / 0 / 190
3490 / 0 / 190
3546 / 0 / 181
3640 / 0 / 199
2600 / 2 / 190
2
1.065
1.07
1.023
1.058
1.055
Final R indices [ I >
R
1
= 0.0811, wR
2
2
=
=
R
1
= 0.0501, wR
2
2
=
=
R
1
= 0.0553, wR
2
2
=
=
R
1
= 0.0625, wR
2
2
=
=
R
1
= 0.0623, wR
2
2
=
=
2sigma(I)]
0.2057
0.1206
0.1033
0.1064
0.1471
R indices (all data)
R
1
= 0.0978, wR
.2260
n/a
1.021 and ꢀ1.674e.Å
R
1
= 0.0650, wR
R
1
= 0.0977, wR
R
1
= 0.1200, wR
1
R = 0.0861, wR
0.1642
n/a
0
0.1281
n/a
0.1181
n/a
0.1240
n/a
Extinction coefficient
ꢀ3
ꢀ3
ꢀ3
ꢀ3
Largest diff. peak and hole
0.581 and ꢀ0.959 e.Å
0.700 and ꢀ0.625 e.Å
0.780 and ꢀ0.809 e.Å
0.322 and ꢀ0.623 e.Åꢀ3
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 10
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Table 2 Hydrogen bonding geometries of compounds
Com
DꢀHꢁꢁꢁA
DꢀH(Ǻ)
0.929
0.930
0.859
HꢁꢁꢁA(Ǻ)
2.511
DꢁꢁꢁA(Ǻ)
3.42(1)
3.43(1)
2.601(9)
∠DꢀHꢁꢁꢁA(°)
165.6
(
i)
2
MPA
C(5)ꢀH(5)ꢁꢁꢁO(2)
(
ii)
C(14)ꢀH(14)ꢁꢁꢁO(1)
2.647
142.6
(
intra)
N(1)ꢀH(1)ꢁꢁꢁN(2)
2.129
114.1
∠
C(3)ꢀN(1)ꢀC(11)ꢀC(12)
ꢀ177.2(7)
145.1
(iii)
3
MPA
N(1)ꢀH(1)ꢁꢁꢁO(1)
C(8)ꢀH(8)ꢁꢁꢁO(2)
0.860
0.930
0.930
0.930
0.860
2.290
2.298
2.536
2.689
2.126
3.036(4)
3.214(5)
3.347(4)
3.396(4)
2.570(4)
(iii)
168.2
(iii)
C(16)ꢀH(16)ꢁꢁꢁO(1)
146
(iv)
C(14)ꢀH(14)ꢁꢁꢁBr(1)
133.3
111.6
(intra)
N(1)ꢀH(1)ꢁꢁꢁO(2)
∠
C(3)ꢀN(1)ꢀC(11)ꢀC(12)
ꢀ85.1(5)
138.6
(iii)
2
2
AMT
EPA
N(1)ꢀH(1)ꢁꢁꢁO(1)
0.860
0.930
0.930
0.860
2.321
2.254
2.662
2.208
3.020(5)
3.163(4)
3.508(4)
2.577(3)
(iii)
C(8)ꢀ(H8)ꢁꢁꢁO(2)
165.7
151.5
105.7
73.3(4)
(v)
C(15)ꢀ(H15)ꢁꢁꢁO(1)
(intra)
N(1)ꢀH(1)ꢁꢁꢁO(2)
∠
C(3)ꢀN(1)ꢀC(11)ꢀC(12)
(
vi)
N(1)ꢀH(1)ꢁꢁꢁO(2)(
C(5)ꢀH(5)ꢁꢁꢁN(2)
0.861
0.929
2.230
2.570
2.987(3)
3.406(5)
146.8
149.8
vi)
(vii)
C(7)ꢀH(7)ꢁꢁꢁO(1)
0.929
0.930
0.861
2.621
2.707
2.099
3.403(4)
3.542(6)
2.575(4)
142.2
(viii)
C(15)ꢀ(H15)ꢁꢁꢁO(1)
149.8
(intra)
N(1)ꢀH(1)ꢁꢁꢁO(2)
114.2
∠
∠
C(3)ꢀN(1)ꢀC(11)ꢀC(12)
C(13)ꢀC(12)ꢀC(11)ꢀN(1)
ꢀ94.8(4)
ꢀ170.2(3)
133.2
(
ix)
2
AET
N(1)ꢀH(1)ꢁꢁꢁO(1)
C(14)ꢀH(14)ꢁꢁꢁBr(1)
0.86
0.93
0.86
2.13
2.912
2.12
2.79(2)
3.57(1)
2.58(2)
(ix)
128.7
(intra)
N(1)ꢀH(1)ꢁꢁꢁO(2)
113.6
∠
∠
C(3)ꢀN(1)ꢀC(11)ꢀC(12)
C(13)ꢀC(12)ꢀC(11)ꢀN(1)
83.0(2)
ꢀ175(1)
i)ꢀx,ꢀy,1ꢀz; ii) ꢀ1.5+x,1/2ꢀy,ꢀ1/2+z; iii) x,ꢀ1+y,z; iv) 1ꢀx,ꢀy,2ꢀz ; v) ꢀ1+x,ꢀ1+y,z; iv) ꢀx,1ꢀy,ꢀz;
vi) 1/2ꢀx,ꢀ1/2+y,1/2ꢀz ; vii) 1/2ꢀx,ꢀ1/2ꢀy,ꢀz ; viii) x,1ꢀy,ꢀ1/2+z; ix) x,1ꢀy,ꢀ1/2+z; x) x,2ꢀy,ꢀ1/2+z
1
1
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Table 3 Molecular interaction of aminonaphthoquinone ligands
Com
Type of interaction
Figure
Number of similar
Angle between naphthoquinone ring plane
neighbouring molecules and pyridine or thiophene ring plane(°)
2
3
2
MPA CꢀHꢁꢁꢁO, Brꢁꢁꢁπ
MPA NꢀHꢁꢁꢁO, CꢀHꢁꢁꢁO, CꢀHꢁꢁꢁBr, πꢁꢁꢁπ stacking Fig.S10
AMT NꢀHꢁꢁꢁO, CꢀHꢁꢁꢁO
Fig.S9
5
5
4
9
85
89
Fig.S11
2
2
EPA
AET
NꢀHꢁꢁꢁO, CꢀHꢁꢁꢁO, CꢀHꢁꢁꢁN
NꢀHꢁꢁꢁO, CꢀHꢁꢁꢁπ, CꢀHꢁꢁꢁBr
Fig.S12
Fig.S13
4
6
22.2
9
Table 4 Experimental UVꢀvisible absorption spectra of chemosensors 2MPA and 2EPA
Solvent systems
Methanol
Methanol+ TEA
Methanol+ Water
λ
max (nm) for 2MPA
λmax (nm) for 2EPA
468, 284
468, 280
477, 282
455, 284
437, 287
467, 272
Methanol+ TEA+ water 458, 362, 282
TEA 449, 331, 307
475, 282
465, 334, 287
1
2
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Scheme 1 Molecular Structures of aminonaphthoquinones under investigation
1
3
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O
1
27.154
8
.06
O
1
76.680 Br
126.971
.00
132.443
7.60
1
7
37.109
.72
8
176.200 Br
1
23.655
7.21
4.699
46.5004.32
137.041
.64
1
32.541 128.240
4
9.214
121.971
7.30
7
.18
7
5
.21
132.579
130.200
1
30.000 146.200
122.092
4
7
.72
132.154
1
134.894
N
7.64
7.69
34.856
8.59
1
80.537
H
155.215
8.16
1
7.91
180.454 N
58.653 N
149.600
1
1
27.020
H
O
N
7.27
1
8
.13
3
.17
38.052
22.874
127.131
7.15
O
2
MPA
8.65
49.182
2
EPA
1
O
1
27.209
.01
8
1
76.753
O
Br
1
8
26.967
.03
1
35.571
.70
126.943
146.362
176.200
7
132.278
1
7
32.908
.64
Br
4
8.727
.11
132.651
7.64
5
126.740
1
29.986
132.158
7
.70
126.596
7.07
4
4.057
1
35.119
124.067
5.25
1
34.867
129.859 146.000
1
80.084
N
H
1
33.985
7.33
1
8
27.371
.12
7.72
N
180.000
H
127.203
7.00
6.28
140.100
1
27.096
O
149.162
.62
149.435
8.57
8.14
6
.10
8
O
S
N
1
25.913
3MPA
C16
C15
7.29
2AMT
1
13
Scheme 2 H and C chemical shift (ppm) of aminonaphthoquinone ligands
1
4
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2MPA
3MPA
2AMT
2EPA
2
AET
Fig.1 ORTEP plots of 2MPA, 3MPA, 2AMT, 2EPA and 2AET. The ellipsoid was drawn with 50% of probability
1
5
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Fig.2 Molecular packing of 2MPA down aꢀaxis
a)
b)
Fig.3a) Polymeric chains of 3MPA molecules formed by C(8)ꢀH(8)ꢁꢁꢁO(2) and N(1)ꢀH(1)ꢁꢁꢁO(1) interaction,. b) Stacked polymeric chains of 3MPA
1
6
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a)
b)
Fig.4a) Molecular packing of 2AMT molecules down aꢀaxis, b) Molecular packing of 2AMT molecules down bꢀaxis, c) Polymeric chains formed by hydrogen
bonding separated by thiophene rings
a)
b)
Fig.5a) Neighboring molecules of EPA. b) Dimeric chains of 2EPA formed by CꢀHꢁꢁꢁO interaction
1
7
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a) b)
Fig.6 a) Molecular packing of 2AET molecules down bꢀaxis and b) down cꢀaxis
1
8
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a)2MPA(blue), 3MPA(yellow), 2AMT(green)
a) 2EPA(green), 2AET(Thiophene)
Fig.7 Overlay structures of a) 2MPA, 3MPA and 2AMT, b)2EPA and 2AET
1
9
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2
MPA
2EPA
3MPA
2AMT
2AET
a
b
c
d
Fig.8Hirshfeld surfaces mapped with (a) dnorm (b) shape index, (c) curvedness and (d) 2D finger print plots with di and dc ranging from 0.6 to 2.4 Å for
MPA, 2EPA, 3MPA, 2AMT and 2AET.
2
2
0
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a)
b)
c)
d)
e)
Fig.9 Optimized structures of (a) 2MPA, (b) 3MPA (c) 2AMT (d) 2EPA (e) AET. Atomic labelling scheme is shown.
2
1
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2MPA
3MPA
2EPA
2AMT
2
AET
Fig.10 Optimized structures of anionic form (a) 2MPA, (b) 3MPA (c) 2AMT (d) 2EPA (e) 2AET
2
2
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a)
b)
3600
3200
2800
1500
1000
500
0
0
8
6
0
5
00
80
1
2
3
000
000
000
1000
1500
2000
7
6
0
0
0
Calculated
2
MPA
Calculated
2
MPA
40
3
500
3000 -
1500
Wavenumber(cm )
1000
500
1
-1
Wavenumber(cm )
3600
3200
2800
1600
1200
800
90
0
5
1
0
5
1
8
6
4
0
Calculated
3MPA
00
00
60
0
0
000
3
MPA
000
30
Calculated
3
500
3000
2500
1500
1000
500
-
1
-1
Wavenumber (cm )
Wavenumber (cm )
3600
3200
2800
2400
1600
1200
800
0
0
6
4
2
0
0
0
60
40
20
2
4
6
00
00
00
200
4
00
00
Calculated
6
2AMT
2AMT
Calculated
3
500
3000
Wavenumber (cm )
2500
1500
1000
500
-1
-1
Wavenumber (cm )
2
3
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1600
1200
800
3500
3000
2500
9
8
7
6
5
4
0
0
90
80
70
60
50
0
2
4
6
8
0
0
0
0
0
2
00
00
00
00
00
00
4
600
800
2
EPA
2EPA
Calculated
Calculated
3600
3200
Wavenumber (cm )
2800-1
1500
Wavenumber (cm )
1000
500
-1
3500
3000
2500
2000
0
2000
1500
1000
500
0
2
7
6
5
4
3
0
7
0
0
0
0
00
2
4
6
00
0
Calculated
6
5
4
400
2
AET
0
0
0
00
00
6
8
1
00
00
Calculated
2AET
000
3500
3000
Wavenumber (cm )
2500
2000
1500
Wavenumber (cm )
1000
500
-
1
-1
Fig.11 Observed and optimized FTꢀIR spectra of 2MPA, 3MPA, 2AMT, 2EPA and 2AET. The spectra is shown in two regions for peaks a)ꢀNH , –CH and b)
C=O, ꢀCꢀN, ꢀCꢀBr.
–
2
4
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a)
HOMO
LUMO
b)
c)
d)
e)
Fig.12 HOMO and LUMO in a) 2MPA, (b) 3MPA (c) 2EPA (d) 2AMT (e) 2AET
2
5
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a)
HOMOꢀ1
HOMOꢀ2
HOMOꢀ3
LUMO+1
LUMO+2
LUMO+3
b)
HOMOꢀ1
LUMOꢀ1
HOMOꢀ2
HOMOꢀ3
LUMOꢀ3
LUMOꢀ2
2
6
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c)
HOMOꢀ1
HOMOꢀ2
HOMOꢀ3
LUMOꢀ1
LUMOꢀ2
LUMOꢀ3
d)
HOMOꢀ1
HOMOꢀ2
HOMOꢀ3
LUMOꢀ1
LUMOꢀ2
LUMOꢀ3
2
7
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e)
HOMOꢀ1
HOMOꢀ2
HOMOꢀ3
LUMOꢀ1
LUMOꢀ2
LUMOꢀ3
Fig.13 MOs namely, HOMOꢀ1, HOMOꢀ2 and HOMOꢀ3 and LUMO+1, LUMO+2 and LUMO+3 in a) 2MPA, (b) 3MPA, (c) 2AMT, (d) 2EPA, (e) 2AET
are also depicted. These enable one to assign the transition in the electronic spectra derived from the TDꢀDFT theory
2
8
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HOMO
LUMO
2
+
Fig. 14 HOMO and LUMO in 2MPAꢀCu complexes.
2
9
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