Naphthaldehyde-derived ligands: Synthesis and their Ni(II) ion complexation

Article abstract of DOI:10.1007/s00706-013-1079-3

Three novel diazacrown ether ligands, namely 17-, 18-, and 20-membered O₂N₂-donor macrocycles derived from 3,3′-[butane-1, 4-diylbis(oxy)]bis(2-naphthalenecarbaldehyde), were prepared and characterized by ¹H and ¹³C NMR spectroscopy and mass spectra. Their host-guest interaction with Ni(II) was studied in DMSO-d ₆ using ¹H NMR spectroscopy. The stoichiometry of the complex in each case in the concentration range examined was determined to be 1:1 using the continuous variation method (Job's plot). The 17-membered O₂N₂-donor macrocycle in which the two nitrogen atoms are tethered by three methylene units binds Ni(II) more strongly than the other two macrocycles do. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00706-013-1079-3

Monatsh Chem (2014) 145:275–279
DOI 10.1007/s00706-013-1079-3
ORIGINAL PAPER
Naphthaldehyde-derived ligands: synthesis and their Ni(II) ion
complexation
•
Naim H. Al-Said Shehadeh Mizyed
•
•
Abdullah G. Al-Sehemi Amani M. Kleeb
Received: 10 January 2013 / Accepted: 28 August 2013 / Published online: 1 October 2013
Ó Springer-Verlag Wien 2013
Abstract Three novel diazacrown ether ligands, namely
17-, 18-, and 20-membered O2N2-donor macrocycles
derived from 3,30-[butane-1,4-diylbis(oxy)]bis(2-naphtha-
hard metal ions (alkali and alkaline earth metals), and
crowns which contain soft donor atoms such as sulfur
atoms that bind transition and heavy metal ions [1]. The
complexing ability of azacrown ethers towards a given ion
depends among other factors on the size of the cavity [2].
The complexation of the 14- to 17-membered O2N2-donor
macrocycles with Ni(II) is dominated by the cavity size [3].
Azacrown ethers have vital functions as synthetic receptors
in molecular recognition processes that are similar to those
in certain biological systems [1]. Most of enzymes exert
their biological activities at some stage during their com-
plexation with an appropriate metal. Nickel is an essential
trace element for many biological processes including ur-
eases [4, 5], hydrogenases, CO dehydrogenases, and
coenzyme F430 [5]. We were therefore interested in
developing synthetic strategies to gain easy access to a
variety of naphthalene azacrown ethers. Previously, a novel
and convenient procedure for the formation of Mannich
bases containing naphthalene rings was reported by our
group [6–8]. The synthesis and complexation ability with
both metal ions and C60 were reported as well as their
biological activities [9]. As part of the extension of this
project, we herein report a convenient and expeditious
method for synthesizing three novel azacrown ethers 1–3
(Fig. 1) and investigating their complexation with nick-
1
lenecarbaldehyde), were prepared and characterized by H
and 13C NMR spectroscopy and mass spectra. Their host–
guest interaction with Ni(II) was studied in DMSO-d6
using 1H NMR spectroscopy. The stoichiometry of the
complex in each case in the concentration range examined
was determined to be 1:1 using the continuous variation
method (Job’s plot). The 17-membered O2N2-donor mac-
rocycle in which the two nitrogen atoms are tethered by
three methylene units binds Ni(II) more strongly than the
other two macrocycles do.
Keywords Diazacrown ethers ꢀ
17-membered O2N2-donor macrocyles ꢀ Job’s plot ꢀ
Ni(II) complexation
Introduction
Azacrown ethers have complexation properties that are
intermediate between crown ethers, which mainly complex
1
el(II) in DMSO-d6 solution using H NMR spectroscopy.
N. H. Al-Said (&) ꢀ A. M. Kleeb
Department of Applied Chemical Sciences, Faculty of Science
and Arts, Jordan University of Science and Technology (JUST),
P.O. Box 3030, Irbid 22110, Jordan
Results and discussion
e-mail: naim@just.edu.jo
In general, macrocyclic Schiff bases prepared by conden-
sation reactions between equimolar amounts of diamines
and aliphatic dicarbonyl compounds are commonly unsta-
ble [10, 11]; nevertheless, these macrocyclic ligands can be
synthesized by the template method [12]. On the contrary,
S. Mizyed
Chemistry Department, Yarmouk University, Irbid, Jordan
A. G. Al-Sehemi
Chemistry Department, Faculty of Science, King Khalid
University, Abha, Saudi Arabia
123

276
N. H. Al-Said et al.
Scheme 1
O
O
OH
R
=
=
(
(
)
4a
R
R
COOH
CO2Me
CH2 NH
n
NH
a
)
4b
1 (n = 3), 2 (n = 4), 3 (n = 6)
b
Fig. 1 Structures of novel azacrown ethers 1–3
O
O
Schiff bases prepared from aromatic diamines and aliphatic
dicarbonyl compounds are more stable and can be isolated
as free ligands. For example, the condensation of acetyl
acetone with an equimolar amount of 2,6-diaminopyridine
in methanol in the presence of catalytic amounts of
hydrochloric acid affords the corresponding [2 ? 2] mac-
rocycle [10, 11].
R
R
=
=
=
( )
e
CO2M
5
R
R
R
c
( )
6
CH2OH
CHO
d
(7)
e
O
O
The synthesis of the novel azacrown ethers 1–3 is shown
in Scheme 1. The commercially inexpensive 3-hydroxy-2-
naphthoic acid was used as the starting material to prepare
dialdehyde 7. The dialdehyde intermediate 7 was synthe-
sized from the corresponding diester 5 by a sequence of
reduction followed by oxidation of the resultant primary
dialcohol 6. Diester 5 was prepared from 3-hydroxy-2-
naphthoic acid which was converted to its corresponding
methyl ester 4 [12, 13], followed by tethering the hydroxyl
group to four methylene units by reacting with 1,4-dibro-
mobutane to form the two ether linkages in diester 5. The
preparation of diester 5 in refluxing acetonitrile for 30 h
afforded the expected product in low yield (50–60 %). On
the other hand, the product was isolated in excellent yield
(90 %) and shorter reaction time (6 h) when the reaction
NH CH2 NH
n
n = 3
n = 6
)
(
)
,
(n = 4) (
3
,
1
2
a) MeOH, H2SO4, 65 °C, 20 h; b) Br-(CH2)4-Br, K2CO3, DMF, 80 °C; c)
LiAlH4, THF, 0 °C; d) PCC, CH2Cl2, rt; e) H2N(CH2)nNH2 (n = 3, 4, or 6),
EtOH, CHCl3, rt to 50 °C (2 h), then NaBH4, rt to 50 °C (0.5 h).
observed at 1675 cm-1 in the IR spectrum of the starting
material disappeared.
The oxidation of dialcohol 6 to the corresponding dial-
dehyde 7 was investigated. Among the reported oxidation
methodologies, pyridinium chlorochromate (PCC) in
dichloromethane produced the expected dialdehyde in a
1
was conducted in dimethylformamide at 80 °C. The H
1
NMR spectrum of diester 5 displayed a singlet signal at
d = 4.25 ppm attributed to the O-CH2 protons of the ether
moiety. Furthermore, the two inner methylene protons
were displayed at 2.18 ppm. The 13C NMR spectrum dis-
played the two methylene carbons at 68.3 and 26.1 ppm.
The carbonyl group was observed at 167.0 ppm. The ESI–
MS showed the molecular ion peak at m/z = 459.2
(M?H), consistent with molecular formula C28H27O6.
The synthesis of dialdehyde 7 was achieved from the
precursor intermediate 5 by a sequence of reduction fol-
lowed by oxidation. Therefore, a solution of compound 5 in
THF was added dropwise to LiAlH4 in THF to afford the
good yield (85 %). The H NMR spectrum of the dialde-
hyde displayed the aldehydic proton (CHO) signal at
10.63 ppm. The two methylene units were observed as two
singlets of equal intensity at 4.32 and 2.22 ppm. The 13C
NMR spectrum indicated the presence of 13 signals
including the aldehyde groups at 190.3 ppm. Furthermore,
the methylene carbon signals were displayed at 68.1 and
26.2 ppm. The ESI–MS showed the (M?H)? peak at
m/z = 499.2, corresponding to the molecular formula
C26H23O4.
With the dialdehyde 7 in hand, the stage was set for the
connection of the two aldehyde groups by flexible linkers
of different lengths through 1,n-diaminoalkanes. The major
problem encountered in the formation of the diazacrown
ether was the solubility of 7, which was insoluble in
methanol and ethanol. A combination of chloroform and
ethanol was found to be a suitable solvent mixture to
enhance the solubility of the dialdehyde. Thus, 1,6-diami-
nohexane in ethanol was added to the dialdehyde dissolved
in a mixture of chloroform and ethanol (1:1). Then the
1
dialcohol 6 after normal work-up. The H NMR spectrum
of the dialcohol 6 displayed O-CH2-Ar protons at
d = 4.68 ppm. The carbon of the O-CH2-Ar was observed
at 67.3 ppm in the 13C NMR spectrum. The ESI–MS
showed the (M?H)? peaks at m/z = 403.2, corresponding
to the molecular formula C26H27O4. The IR spectrum dis-
played an absorption band at 3323 cm-1 attributed to the
–OH stretching; in addition, the carbonyl absorption band
123

Naphthaldehyde derived ligands
277
Fig. 2 Benesi–Hildebrand plot
1
of H NMR chemical shift data
for the Ni(II):1 system
Jobs plot for 1:Ni(II)
0.5
0.45
0.4
Table 1 K values for Ni(II) complexes with ligands 1, 2, and 3
Ligand
Kassoc
R2
0.35
0.3
1 (n = 3)
2 (n = 4)
3 (n = 6)
819 32
776 39
518 26
0.98
0.97
0.97
0.25
0.2
0.15
0.1
0.05
0
resulting mixture was heated under reflux for 2 h, cooled to
room temperature before NaBH4 was added. After that, the
mixture was stirred for 1 h at room temperature, heated at
reflux for 2 h, cooled to room temperature, and water was
added to destroy the excess NaBH4. The diazacrown ether
3 was produced in 58 % yield. The other diazacrown ethers
1 and 2 were similarly prepared. The spectroscopic data of
the newly prepared compounds 1–3 fit the proposed
structures. For example, the 13C NMR spectrum of com-
pound 1 displayed five signals at d = 26.4, 30.8, 48.2,
51.1, and 66.9, representing the methylene groups.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X1
Fig. 3 1:1 Job’s plot for the 1:Ni(II) complex
Complex formation between Ni(II) and compounds 1, 2,
1
or 3 was studied using H NMR spectroscopy. The 1:1
complexation process between Ni(II) and diazacrown ether
1 (n = 3) in DMSO-d6 solution is depicted as
4.3
4.25
4.2
4.15
4.1
4.05
4
3.95
3.9
3.85
3.8
NiðIIÞ þ 1 ꢀ NiðIIÞ : 1
δ /ppm
The association constant K shown below can be
determined using the NMR version of the Benesi–
Hildebrand treatment [13].
Fig. 4 Chemical shift changes of compound 1 owing to complexa-
tion with Ni(II). The concentration of Ni(II) increases from A to H
Job’s plot for the 1:Ni(II) complex. The other ligands
showed similar behavior.
Dd=½NiðIIÞꢁ ¼ ꢂ K Dd þ KDdmax
A plot of Dd/[Ni(II)] against Dd for Ni(II) with
diazacrown ether 1 is shown in Fig. 2. The values of
K at 298 K, listed in Table 1, are determined from the
slopes of the corresponding Benesi–Hildebrand figures of
compounds 1–3. The stoichiometry of the complex in each
case in the concentration range examined was determined
to be 1:1 using the mole ratio method and continuous
variation method (Job’s plot). Figure 3 shows a typical 1:1
It is evident that the benzylic protons next to the N
atoms are mostly deshielded by Ni(II), whereas the other
protons are less affected by the complex formation as
shown in Fig. 4. This observation is consistent with com-
plex formation in which the Ni(II) guest is included in the
cavity of the host and is coordinated to the N atoms. The
relatively small changes seen in the chemical shift of the
other protons provide additional support for this view.
123

278
N. H. Al-Said et al.
The resultant mixture was heated to 80 °C for 6 h. The
reaction mixture was cooled to room temperature and then
poured to 100 cm3 ice water. The resulting solution was
extracted with dichloromethane (3 9 50 cm3). The com-
bined dichloromethane extract was dried, filtered, and
concentrated. The product was re-precipitated by addition
of ethanol to afford a pale yellow precipitate of diester 5
(9.50 g, 83 %). M.p.: 145–146 °C; 1H NMR (CDCl3):
d = 2.18 (s, 4H), 3.90 (s, 6H), 4.25 (s, 4H), 7.22 (s, 2H),
7.35 (t, J = 7.6 Hz, 2H), 7.49 (t, J = 7.4 Hz, 2H), 7.70 (d,
J = 8.2 Hz, 2H), 7.79 (d, J = 8.1 Hz, 2H), 8.27 (s, 2H)
ppm; 13C NMR (CDCl3): d = 26.0, 52.3, 68.3, 107.8,
122.2, 124.4, 126.6, 127.6, 128.4, 128.8, 132.8, 136.3,
155.1, 166.9 ppm; ESI–MS: m/z = 459.2 (MH?).
The data shown in Table 1 reveal that ligand 1 binds the
Ni(II) slightly stronger than ligand 2 does, which in turn
binds the metal stronger than ligand 3 does. Looking at the
cavity sizes of these ligands leads to the conclusion that as
the cavity size increases, the stability of the complex
decreases. Ligand 1 appears to have the optimum cavity
size to include Ni(II). It seems to us that the entropy factor
has an additional effect, because the larger cavity size
needs more energy for the pre-organization step of the
complexation process.
Conclusion
3,30-[Butane-1,4-diylbis(oxy)]bis(2-naphthalenemethanol)
(6, C26H26O4)
1
The H NMR spectroscopic investigation reveals that the
stoichiometry of the Ni(II) complexation with 17-, 18-, and
20-membered O2N2-donor macrocycles is 1:1 using the
mole ratio method. The 17-membered O2N2-donor mac-
rocycle in which the two nitrogen atoms are tethered by
three methylene units was found to attract Ni(II) more
strongly than the other two do.
A solution of 4.60 g diester 5 (10.0 mmol) in 150 cm3 THF
was added dropwise to a stirred solution of 0.86 g LiAlH4
(20.0 mmol) in 100 cm3 THF cooled in an ice bath. The
reaction mixture was then stirred and heated under reflux
for 0.5 h, after which it was cooled again to 0 °C and
2 cm3 ethyl acetate was added dropwise. The resultant
mixture was poured into 100 cm3 of an aqueous H2SO4
solution, then the product was extracted by ethyl acetate
(3 9 100 cm3). After drying over Na2SO4 and filtering, the
ethyl acetate was evaporated to afford diol 6 as a yellow
solid (3.00 g, 75 %). M.p.: 195 °C; IR (KBr): vꢀ = 3322,
3048, 2925, 2871, 1630, 1602, 1498, 1450 cm-1; 1H NMR
(DMSO-d6): d = 2.01 (s, 4H), 4.19 (s, 4H), 4.68 (s, 4H),
7.29 (s, 2H), 7.32 (t, J = 7.5 Hz, 2H), 7.40 (t, J = 7.4 Hz,
2H), 7.76 (d, J = 8.1 Hz, 2H), 7.81 (d, J = 8.0 Hz, 2H),
7.86 (s, 2H) ppm; 13C NMR (DMSO-d6): d = 25.6, 58.4,
67.2, 105.4, 123.5, 125.1, 125.7, 126.4, 127.3, 128.2,
132.5, 133.3, 154.3 ppm; ESI–MS: m/z = 402.2 (M?).
Experimental
All fine chemicals were used as purchased. Ethyl acetate
and hexane were distilled prior to use. Dichloromethane
(CH2Cl2), acetonitrile (CH3CN), and triethylamine (Et3N)
were distilled from calcium hydride under nitrogen atmo-
sphere before use. Tetrahydrofuran (THF), ethyl ether
(Et2O), and 1,4-dioxane were distilled from sodium ben-
zophenone ketyl under nitrogen prior to use. Methanol
(MeOH) was distilled from magnesium methoxide. Melt-
ing points were determined using an electrothermal digital
melting point apparatus. IR spectra were recorded using a
3,30-[Butane-1,4-diylbis(oxy)]bis-
(2-naphthalenecarbaldehyde) (7, C26H22O4)
1
Nicolet Impact 410 FT-IR spectrophotometer. The H and
A solution of 2.15 g PCC (10 mmol) in 50 cm3 dichloro-
methane was added dropwise to a stirred solution of 1.00 g
diol 6 (2.5 mmol) in 50 cm3 dichloromethane. The resul-
tant mixture was stirred at room temperature for 5 h, and
then the reaction mixture was passed through a silica gel
column and eluted with dichloromethane. The dichloro-
methane was evaporated to afford dialdehyde 7 (0.85 g,
85 %) as a yellow solid. M.p.: 195–196 °C; IR (KBr):
vꢀ = 3055, 2950, 2854, 1689, 1627, 1590, 1494,
13C NMR spectra were recorded at 400 and 100 MHz
respectively, using a Bruker Avance III instrument.
Chemical shifts were recorded as d values in ppm. Spectra
were taken in DMSO-d6, CDCl3, or C6D6 and the peaks
due to the residual protons of DMSO (2.50 ppm for 1H and
39.43 ppm for 13C), CDCl3 (7.26 ppm for 1H and
77.00 ppm for 13C), and C6D6 (7.16 ppm for 1H and
128.06 ppm for 13C) were used as references if TMS was
not available. Mass spectra were measured on an API 3200
instrument using an ESI probe.
1
1449 cm-1; H NMR (CDCl3): d = 2.22 (s, 4H), 4.32 (s,
4H), 7.22 (s, 2H), 7.39 (t, J = 7.4 Hz, 2H), 7.54 (t,
J = 7.4 Hz, 2H), 7.74 (d, J = 8.4 Hz, 2H), 7.88 (d,
J = 8.0 Hz, 2H), 8.40 (s, 2H) ppm; 13C NMR (CDCl3):
d = 26.2, 68.1, 107.3, 124.9, 125.8, 126.9, 128.0, 129.5,
130.2, 131.1, 137.8, 157.1, 190.3 ppm; ESI–MS m/z =
399.2 (MH?).
Dimethyl 3,30-[butane-1,4-diylbis(oxy)]bis-
(2-naphthalenecarboxylate) (5, C28H26O6)
1,4-Dibromobutane (5.40 g, 25.0 mmol) and 13.80 g
potassium carbonate (100.0 mmol) were added to a stirred
solution of ester 10.00 g 4 (50.0 mmol) in 150 cm3 DMF.
123

Naphthaldehyde derived ligands
279
6,7,8,9,10,11,12,13,14,15,23,24,25,26-Tetra-
decahydrodinaphtho[2,3-b:20,30-n][1,16,5,12]-
J = 7.3 Hz, 2H), 7.58 (s, 2H), 7.68 (d, J = 8.2 Hz, 2H),
7.71 (d, J = 8.2 Hz, 2H) ppm; 13C NMR (C6D6):
d = 26.4, 30.8, 48.2, 51.1, 66.9, 106.1, 123.9,126.3,
126.6, 129.5, 130.2, 131.5, 134.7, 156.4 ppm; ESI–MS:
m/z = 441.2 (MH?).
dioxadiazacycloicosine (3, C32H38N2O2)
A solution of 4 % (v/v) 1,6-diaminohexane in ethanol
(1.7 cm3) was added at 0.3 cm3/h to a stirred solution of
0.10 g dialdehyde 7 (0.25 mmol) in 25 cm3 chloroform
and 25 cm3 ethanol. The resultant mixture was heated
under reflux for 2 h, then it was kept at room temperature
for 0.5 h. NaBH4 (0.038 g, 1.0 mmol) was added and the
mixture was heated to reflux for 1 h. Water (25 cm3) was
added and the products were extracted using chloroforme
(3 9 50 cm3). The combined chloroform extract was dried
over Na2SO4, filtered, and then the chloroform was
evaporated. The residue was purified by column chroma-
tography eluting with methanol/25 % ammonia (9.9:0.1,
v/v) to afford the product 3 (0.07 g, 58 %). M.p.:
156–157 °C; IR (KBr): vꢀ = 3394, 3052, 2927, 2848,
Complex formation
To obtain the association constants (K) corresponding to
complex formation, changes in the chemical shifts (Dd) as
a function of [Ni(II)] were determined. Amounts of 2 mg
of the host compound (1, 2, or 3) were dissolved in
2.00 cm3 of DMSO-d6. A 0.60-cm3 portion of this solution
was transferred into an NMR tube, to which were added
portions of NiCl2 solution prepared using the ligand solu-
tion as a solvent to eliminate the dilution effect. At least
8–10 data points were collected for each run, and each run
was conducted in duplicate. The changes in chemical shifts
(Dd) were plotted against [Ni(II)] for each run, and the
resulting mole ratio plots level off at around a 1:1 ratio of
Ni(II) and 1, 2,or 3, indicating the formation of a 1:1
complex in each case. The stoichiometry of each complex
was confirmed using the method of continuous variation
(Job’s plot). Figure 3 shows a typical 1:1 Job’s plot for the
1:Ni(II) complex. The other ligands showed similar
behavior. To calculate K values, the slopes and the inter-
cepts obtained from linear regression analyses of the
Benesi–Hildebrand plot were used (Fig. 2).
1631, 1598, 1594, 1502, 1456 cm-1 1H NMR (C6D6):
;
d = 1.06 (s, 4H), 1.24 (t, J = 6.4 Hz, 4H), 1.41 (s, 4H),
2.40 (t, J = 6.4 Hz, 4H), 3.35 (s, 4H), 3.76 (s, 4H), 6.68 (s,
2H), 6.98 (t, J = 7.4 Hz, 2H), 7.08 (t, J = 7.5 Hz, 2H),
7.40 (s, 2H), 7.43 (s, 2H), 7.44 (s, 2H) ppm; 13C NMR
(C6D6): d = 26.5, 26.7, 29.7, 48.9, 49.7, 67.6, 106.1,
124.0, 126.2, 126.7, 129.4, 129.5, 131.5, 134.5, 156.3 ppm;
ESI–MS: m/z = 483.3 (M?H).
6,7,8,9,10,11,12,13,21,22,23,24-Dodecahydrodinaph-
tho[2,3-b:20,30-l][1,14,5,10]dioxadiazacyclooctadecine
(2, C30H34N2O2)
Using the same general procedure as for 3, reaction of 7
with 1,4-diaminobutane afforded the product 2 (0.085 g,
75 %). M.p.: 157–158 °C; IR (KBr): vꢀ = 3324, 3054,
Acknowledgments We thank the Deanship of Research at Jordan
University of Science and Technology for financial support.
2930, 1630, 1600, 1504, 1460 cm-1 1H NMR (C6D6):
;
References
d = 1.62 (s, 4H), 1.68 (s, 4H), 2.70 (s, 4H), 3.64 (s, 4H),
3.98 (s, 4H), 6.97 (s, 2H), 7.27 (t, J = 7.4 Hz, 2H), 7.37 (t,
J = 7.4 Hz, 2H), 7.60 (s, 2H), 7.78 (d, J = 8.1 Hz, 2H),
7.72 (d, J = 8.2 Hz, 2H) ppm; 13C NMR (C6D6):
d = 26.3, 27.8, 49.3, 50.6, 67.4, 106.3, 124.0, 126.3,
126.6, 129.4, 129.9, 131.2, 134.6, 156.4 ppm; ESI–MS:
m/z = 455.5 (MH?).
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¨
8,9,10,18,19,20,21,22,23,24-Decahydro-7H-dinaph-
tho[2,3-b:20,30-k][1,5,9,13]dioxadiazacycloheptadecine
(1, C29H32N2O2)
Using the same general procedure as for 3, reaction of 7
with 1,3-diaminopropane afforded the product 1 (0.08 g,
73 %). M.p.: 204–205 °C; IR (KBr): vꢀ = 3321, 3051,
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3.95 (s, 4H), 6.95 (s, 2H), 7.27 (t, J = 7.4 Hz, 2H), 7.37 (t,
123