New heavy metal ion-selective macrocyclic ligands with mixed-donor atoms and their extractant properties

Article abstract of DOI:10.1080/00958972.2010.494303

Synthetic procedures for new macrocyclic diamides with N₂S ₄O_3- and N₂S₅O_3-donors were given. The corresponding macrocyclic ligands were prepared by reaction of NaBH4 with the macrocyclic d

Full text of DOI:10.1080/00958972.2010.494303

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New heavy metal ion-selective
macrocyclic ligands with mixed-donor
atoms and their extractant properties
Halıt Kantekın a , Meltem B. Kiliçaslan a , Fatma Ağin a , Hakan
Alp b & Ümmühan Ocak a
a Department of Chemistry , Karadeniz Technical University ,
Trabzon 61080, Turkey
b Maçka Vocational School, Karadeniz Technical University ,
Maçka, Trabzon 61080, Turkey
Published online: 09 Jul 2010.
To cite this article: Halıt Kantekın , Meltem B. Kiliçaslan , Fatma Ağin , Hakan Alp & Ümmühan
Ocak (2010) New heavy metal ion-selective macrocyclic ligands with mixed-donor atoms
and their extractant properties, Journal of Coordination Chemistry, 63:11, 1921-1932, DOI:
10.1080/00958972.2010.494303
To link to this article: http://dx.doi.org/10.1080/00958972.2010.494303
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Journal of Coordination Chemistry
Vol. 63, No. 11, 10 June 2010, 1921–1932
New heavy metal ion-selective macrocyclic ligands with
mixed-donor atoms and their extractant properties
_
_
˘
HALIT KANTEKIN*y, MELTEM B. KILICASLANy, FATMA AGINy,
¸
¨
¨
HAKAN ALPz and UMMUHAN OCAKy
yDepartment of Chemistry, Karadeniz Technical University, Trabzon 61080, Turkey
zMac¸ ka Vocational School, Karadeniz Technical University, Mac¸ ka,
Trabzon 61080, Turkey
(Received 31 December 2009; in final form 3 March 2010)
Synthetic procedures for new macrocyclic diamides with N2S4O3- and N2S5O3-donors were
given. The corresponding macrocyclic ligands were prepared by reaction of NaBH4 with the
macrocyclic diamides in the presence of boron triflouride ethyl etherate in dry tetrahydrofuran.
The solvent extraction method was used to evaluate metal-ion binding properties of the new
ligands. The values of the extraction constants (log Kex) and the complex compositions were
determined for the extracted complexes. The solvent extraction experiments suggested that the
reduced N2S5O3-donor macrocycle has Agþ selectivity compared to Pb2þ, Co2þ, Ni2þ, Mn2þ
and Cd2þ for chloroform as organic solvent.
,
Keywords: Extraction constant; Mixed-donors; Macrocyclic ligand; Extractability; Selective
extraction
1. Introduction
Macrocyclic multidentate ligands with an appropriate combination of ring size, identity
and placement of donors exhibit a good extraction selectivity for the desired metal ions
[1]. These compounds have been used for processes, such as separation of ions by
transport through artificial and natural membranes, liquid–liquid phase transfer
reactions, preparation of ion-selective electrodes, and isotope separation [2, 3].
Since crown ethers were first recognized by Pedersen as having selective metal-ion
binding properties [4, 5], various crown ethers have been prepared and their
complexation behaviors are studied extensively. Coordination chemistry of mixed
nitrogen, oxygen, and sulfur donor macrocycles has also been an area of increasing
interest over the past 15 years. These ligands are of interest as they offer coordination of
both hard donor N-ligands and soft donor, and potential p-acceptor S-ligands [6, 7].
The selectivity of alkali and alkaline earth metal ion extraction with macrocycles
containing oxygen donors, primarily crown ethers, is correlated with its radius [8].
In metal extraction with macrocycles containing nitrogen–sulfur–oxygen donors, many
*Corresponding author. Email: halit@ktu.edu.tr
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ꢀ 2010 Taylor & Francis
DOI: 10.1080/00958972.2010.494303

1922
H. Kantekin et al.
factors exert influence on the extraction process, any of which may become crucial.
The number of heteroatoms and their donor abilities may be decisive or the rigidity
of the macrocyclic structure may be of primary importance. There are many examples
of selective metal extraction with crown ethers having sulfur and nitrogen
donors [9–12].
In previous studies, we have investigated the solvent extraction properties of some
macrocyclic ionophores containing mixed donors for heavy metals [13, 14]. In this
study, we present solvent extraction properties of one of a series of macrocyclic ligands
with N, S, and O mixed donors for Cd2þ, Pb2þ, Mn2þ, Ni2þ, Co2þ, and Agþ.
2. Experimental
2,3-Dibenzo-7,10,13-trioxa-4,16-dithia-1,19-diazanonadecane (1) was synthesized in
our laboratory according to the procedure described previously [15]. NaBH4, boron
trifluoride ethyl etherate, tetrahydrofuran (THF), chloroacetyl chloride (2), dichlor-
omethane, chloroform, picric acid, Pb(NO3)2, Co(NO3)2 ꢀ 6H2O, Ni(NO3)2 ꢀ 6H2O,
Cd(NO3)2 ꢀ 4H2O, Mn(NO3)2, ꢀ 4H2O, and AgNO3 were the analytical grade reagents
purchased from Merck. Demineralized water was used in extraction experiments. The
solvents were saturated with each other before use in order to prevent volume changes
of the phases during extraction.
IR spectra were recorded on a Perkin Elmer 1600 FT-IR spectrophotometer using
1
KBr pellets or NaCl disc. H- and 13C-NMR (nuclear magnetic resonance, NMR)
spectra were recorded on a Varian Mercury 200 MHz spectrometer in CDCl3 or
DMSO, and chemical shifts are reported (ꢀ) relative to Me4Si as internal standard.
Mass spectra (MS) were measured on a Micromass Quattro LC/ULTIMA LC-MS/MS
spectrometer. Elemental analyses were determined by a LECO Elemental Analyser
(CHNS O932). Melting points were measured on an electrothermal apparatus and are
uncorrected. The spectrophotometric measurements were carried out with a Unicam
uv2 UV-Vis spectrophotometer. In solvent extraction experiments Grant SS 30-type
shaker with thermostat was used.
2.1. Preparation of N,N0-[oxybis(ethane-2,1-diyloxyethane-2,1-diylthio-2,
1-phenylene)]bis(2-chloroacetamide) (3)
A solution of 1 (3.1 g, 7.59 mmol) in dry benzene (38 mL) and anhydrous Na2CO3
(2.41 g, 22.77 mmol) under argon was prepared and the mixture was placed in an ice
bath. A solution of 2 (1.72 g, 15.18 mmol) in dry benzene (76 mL) was added dropwise
for approximately 2 h where the temperature of the solution was kept at 0–5ꢁC and
continually stirred at room temperature overnight. Then the mixture was filtered and
the solvent was evaporated under reduced pressure to get a cream-like oily product. The
crude product was crystallized from methanol. Yield: 1.12 g (26%), m.p.: 73–75ꢁC.
Anal. Calcd for C24H30N2O5S2Cl2: C, 51.33; H, 5.3; and N, 4.99. Found: C, 51.15; H,
4.28; N, and 6.21. IR (KBr pellets, cmꢂ1): 3288 (N–H), 3057 (Ar–H), 2889–2923 (C–H),
1671 (C¼O), 1220–1109 (O–CH2). 1H-NMR (CDCl3): ꢀ 9.73 (s, 2H, NH–C¼O),
8.41 (d, 2H, Ar–H), 7.58 (t, 2H, Ar–H), 7.34 (d, 2H, Ar–H), 7.12 (t, 2H, Ar–H), 4.45

Heavy metal ion-selective
1923
(s, 4H, CH2–Cl), 3.53 (t, 12H, O–CH2), and 3.21 (t, 4H, S–CH2). 13C-NMR (CDCl3):
164.09 (O¼C–CH2), 140.07 (Ar–C), 135.90 (Ar–C), 130.07 (Ar–C), 124.89 (Ar–C),
120.00 (Ar–C), 112.8 (Ar–C), 70.54–69.39 (O–CH2), 43.42 (N–CH2), and 35.55
(S–CH2). (FAB) MS m/z ¼ 561 [M]þ.
2.2. Preparation of 6,7,8,9,10,12,13,15,16,26,27-decahydro-22H,29H-
dibenzo[k,w][1,4,7,10-16,19,25,13,22]trioxatetrathiadiazacycloheptacosine-
23,30(24H,31H)-dione (5)
A solution of 3 (0.2 g, 0.356 mmol), dry K2CO3 (0.197 g, 1.42 mmol) and 1,2-etandithiol
(4) (0.033 g, 0.356 mmol) in dry acetonitrile (50 mL) was stirred under argon at room
temperature for 72 h. At the end of this period, the mixture was filtered and the filtrate
was evaporated under reduced pressure to get light yellow oily product. Yield: 0.18 g
(84%). Anal. Calcd for C26H34N2O5S4: C, 53.60; H, 5.84; and N, 4.81. Found: C, 53.02;
H, 5.28; N, 5.03. IR (NaCl disc, cm-1): 3303 (N–H), 3058 (Ar–H), 2921–2862 (C–H),
1
1690 (C¼O), 1201–1112 (OCH2). H-NMR (CDCl3): ꢀ 9.75 (s, 4H, NH), 8.37(d, 2H,
Ar–H), 7.55 (m, 4H, Ar–H), 7.36 (d, 2H, Ar–H), 3.72 (s, 4H, O¼C–CH2), 3.54 (t, 8H,
O–CH2), 3.11 (t, 4H, S–CH2), 2.95 (s, 8H, S–CH2). 13C-NMR (CDCl3) ꢀ: 168.55
(C¼O), 138.64 (Ar–C), 133.14 (Ar–CH), 128.51 (Ar–C), 126.14 (Ar–C), 124.30 (Ar–C),
123.79.12 (Ar–C), 71.03 (O–CH2), 41.45 (N–CH2), and 34.76 (S–CH2). (EI) MS
m/z ¼ 583 [M þ 1]þ.
2.3. Preparation of 6,7,9,10,12,13,15,16,23,24,26,27,30,31-tetradecahydro-22H,
29H-dibenzo-[k,w][1,4,7,10,16,19,25,13,22]trioxatetrathiadiazacyclohepta-
cosine (6)
A solution of 5 (0.15 g, 0.258 mmol) in dry THF (9 mL) was stirred at room temperature
under argon until it dissolves and the mixture was placed in an ice bath. NaBH4
(0.088 g, 2.322 mmol) was added to the mixture being stirred at 0–5ꢁC under argon.
Boron trifluoride ethyl etherate (0.40 g, 2.84 mmol) was added dropwise for approx-
imately 3 h where the temperature was kept constant overnight. At the end of this
period, one or two drop(s) of water was added to the solution and the release of H2 gas
was seen and then the solution was neutralized using aqueous NaOH (20%) until the
pH value of the mixture becomes 8–9. THF was evaporated under reduced pressure
and the residue was extracted with 50 mL of chloroform. The extract was dried over
anhydrous MgSO4 and the solvent was evaporated under reduced pressure to obtain the
oily product. Yield 0.08 g (57%). Anal. Calcd for C26H38N2O3S4: C, 56.31; H, 6.85;
and N, 5.05. Found: C, 55.87; H, 6.38; and N, 5.42. IR (NaCl disc, cmꢂ1): 3358 (N–H),
3061 (Ar–H), 2922–2856 (C–H), 3061, and 1282–1193 (C–O). 1H-NMR (CDCl3):
ꢀ 7.76 (d, 2H, Ar–H), 7.46 (t, 2H, Ar–H), 6.92 (m, 4H, Ar–H), 5.71 (s, 2H, NH), 3.53
(t, 12H, O–CH2), 2.98 (t, 4H, N–CH2), and 2.94 (t, 12H, S–CH2). 13C-NMR (CDCl3):
ꢀ 148.29 (Ar–C), 135.85 (Ar–C), 131.55 (Ar–CH), 130.02 (Ar–C), 116.27 (Ar–C), 116.18
(Ar–C), 69.68–68.83 (O–CH2), 42.09 (N–CH2), and 34.85 (S–CH2). (FAB) MS
m/z ¼ 555 [M þ 1]þ.

1924
H. Kantekin et al.
2.4. Preparation of 6,7,8,9,10,12,13,15,16,26,27-decahydro-22H,29H-diben-
zo[k,w][1,4,7,10-16,19,25,13,22]trioxapentathiadiazacycloheptacosine-
23,30(24H,31H)-dione (8)
A solution of 3 (0.8 g, 1.426 mmol), dry K2CO3 (0.786 g, 5.70 mmol), and mercap-
toethylsulfide (7) (0.20 g, 1.426 mmol) in dry acetonitrile (54 mL) was stirred under
argon at room temperature for 72 h. At the end of this period, the mixture was filtered
and the filtrate was evaporated under reduced pressure to get light yellow product.
Yield: 0.55 g (60%). Anal. Calcd for C28H38N2S5O5: C, 52.34; H, 5.91; and N, 4.36.
Found: C, 52.79; H, 5.98; and N, 3.99. IR (NaCl disc, cmꢂ1): 3307 (N–H), 3049 (Ar–H),
1
2920–2862 (C–H), 1682 (C¼O), and 1240–1111 (OCH2). H-NMR (CDCl3): ꢀ 8.36 (s,
2H, NH), 7.93 (d, 2H, Ar–H), 7.52 (t, 2H, Ar–H), 6.80 (m, 4H, Ar–H), 3.82 (s, 4H,
O¼C–CH2), 3.78 (t, 12H, O–CH2), and 2.38 (m, 12H, S–CH2). (FAB) MS m/z ¼ 681
[M þ K]þ.
2.5. Preparation of 6,7,9,10,12,13,15,16,23,24,26,27,30,31-tetradecahydro-22H,29H-
dibenzo-[k,w][1,4,7,10,16,19,25,13,22]trioxapentathiadiazacycloheptacosine (9)
A solution of 8 (0.520 g, 0.809 mmol) in dry THF (110 mL) was stirred at room
temperature under argon until it dissolves and the mixture was placed in an ice bath.
NaBH4 (0.277 g, 7.281 mmol) was added to the mixture being stirred at 0–5ꢁC under
argon. Boron trifluoride ethyl etherate (1.26 g, 8.94 mmol) was added dropwise through
a dropping funnel for approximately 3 h where the temperature was kept constant
overnight. At the end of this period, one or two drop(s) of water was added to the
solution and H2 gas was evolved and then the solution was neutralized using aqueous
NaOH (20%) until the pH value of the mixture is in the range 8–9. THF was
evaporated under reduced pressure and the residue was extracted with 50 mL of
chloroform. The extract was dried over anhydrous MgSO4 and the solvent was
evaporated under reduced pressure to get the oily product. Yield 0.43 g (88%). Anal.
Calcd for C28H42N2S5O3: C, 54.72; H, 6.84; and N, 4.56. Found: C, 54.98; H, 6.52; and
N, 4.18. IR (NaCl disc, cmꢂ1): 3360 (N–H), 3064 (Ar–H), 2955–2854 (C–H), and
1279–1199 (CH2–O). 1H-NMR (CDCl3): ꢀ (ppm) 7.63 (d, 2H, Ar–H), 7.46 (t, 2H,
Ar–H), 6.93 (m, 4H, Ar–H), 5.42 (s, 2H, NH), 3.55 (t, 12H, O–CH2), 3.11 (t, 4H,
N–CH2), and 2.88 (s, 16H, S–CH2). 13C-NMR (CDCl3): ꢀ 148.59 (Ar–C), 136.72
(Ar–C), 130.34 (Ar–CH), 117.12 (Ar–C), 117.01 (Ar–C), 110.04 (Ar–C), 70.55–69.83
(O–CH2), 42.81 (N–CH2), and 35.56 (S–CH2). (FAB) MS m/z ¼ 615 [M þ 1].
2.6. Extraction method
The previous method was used in the extraction experiment [16]. An organic solution
(10 mL) of ligand (7.5 ꢃ 10ꢂ5 mol Lꢂ1) and an aqueous solution (10 mL) containing
1.25 ꢃ 10ꢂ5 mol Lꢂ1picric acid and 1 ꢃ 10ꢂ2 mol Lꢂ1 metal nitrate were placed in a
stoppered flask and shaken for 2 h at 25.0 ꢄ 0.1ꢁC. This period of shaking was enough
to establish equilibrium between the two phases. Dichloromethane and chloroform
were used as organic solvents. The resulting mixtures were allowed to stand for at least
2 h at that temperature in order to complete the phase separation. The concentration of
picrate ion remaining in the aqueous phase was then determined spectrophotometrically

Heavy metal ion-selective
1925
at 355 nm. Blank experiments showed that no picrate extraction occurred in the absence
of the ligand.
The extractability (E%) was determined based on absorbance of picrate in aqueous
solutions. The extractability was calculated from the following equation:
ꢀ
ꢁ
ðA0 ꢂ AÞ
E% ¼
ꢃ 100,
ð1Þ
A0
where A0 is the absorbance in the absence of ligand and A the absorbance in the
aqueous phase after extraction.
The dependence of the distribution ratio D of the cation between the aqueous phase
and the organic phase upon ligand concentration was examined. The range of the ligand
concentration was 2.5 ꢃ 10ꢂ6 ꢂ 7.50 ꢃ 10ꢂ5 mol Lꢂ1
.
The general extraction equilibrium is assumed to be given by the following equation.
Mnaqþ þ n Picꢂ þ m Lorg $ ½MðPicÞnðLÞmꢅorg
,
ð2Þ
where ‘‘aq’’ denotes aqueous solution and ‘‘org’’ organic solution. The following
logarithmic expression is valid for the above extraction system.
logfD=½Picꢂꢅng ¼ log Kex þ m log½Lꢅ:
ð3Þ
The plot of log {D/[Picꢂ]n} as a function of log [L] should give a straight line with a
slope of m and log Kex can be calculated from the intercept by using equation (3).
3. Results and discussion
The preparations of four macrocyclic ligands containing nitrogen, sulfur, and oxygen
donors 5, 6, 8, and 9 are shown in scheme 1. The new ligands were characterized by a
1
combination of elemental analysis, IR, H-NMR, 13C-NMR, and MS spectral data.
Reaction of 1 with chloroacetylchloride in dichloromethane at 0–5ꢁC under
argon afforded N,N0-[oxybis(ethane-2,1-diyloxyethane-2,1-diylthio-2,1-phenylene)]-
bis(2-chloroacetamide) (3) in a Schlenk system in 26% yield. In the IR spectrum of
3, the disappearance of aromatic primary–NH2 vibrations of 1 after introduction of
amide function, and presence of –NH, C¼O group stretching vibrations at 3288 and
1671 cmꢂ1, respectively, confirmed the proposed structure. In the 1H-NMR spectrum of
3, the singlet at ꢀ ¼ 4.45 ppm corresponded to methylene protons between C¼O and Cl
groups. The protons of –NH were observed at ꢀ ¼ 9.73 ppm as a singlet. The C¼O of 3
gave a carbon resonance at ꢀ ¼ 164.09 ppm in the 13C-NMR spectrum. The MS of 3
displayed the expected molecular ion peak at m/z ¼ 561 [M]þ in the MS obtained using
the (EI) MS technique.
The reaction of 3 with ethane-1,2-dithiol and 4-fold excess of anhydrous K2CO3 in
dry acetonitrile at room temperature under argon afforded 6,7,8,9,10,12,13,
15,16,26,27-decahydro-22H,29H-dibenzo[k,w][1,4,7,10–16,19,25,13,22]-trioxatetrathia-
diazacycloheptacosine-23,30(24H,31H)-dione (5) in 84% yield. The IR spectrum of 5 is
almost identical to that of 3 with small changes in wave numbers. The formation
of macrocycle was confirmed by the appearance of a new resonance for S–CH2

1926
H. Kantekin et al.
O
O
O
S
S
NH
2
O
2
Cl
Cl
+
NH
2
2
1
dry
benzene
Na2CO3
O
O
S
S
HN
HN
Cl
O
O
Cl
O
3
HS
SH
HS
S
SH
4
7
O
O
O
O
S
S
HN
HN
S
S
O
O
S
HN
HN
S
S
O
S
O
S
O
O
5
8
NaBH4
dry THF
Bortrifluoridethylether
NaBH4
dry THF
Bortrifluoridethylether
O
O
S
S
HN
HN
S
S
O
O
S
S
HN
HN
S
S
O
O
S
6
9
Scheme 1. Synthetic pathways to the new macrocyclic ligands used in this study.
1
at ꢀ ¼ 2.95 ppm in the H-NMR spectrum. The 13C-NMR spectrum of 5 indicated
new resonance for S–CH2 carbons at ꢀ ¼ 34.76 ppm when compared with the 13C-NMR
spectrum of 3. The MS of 5 displayed the expected molecular ion peak at m/z ¼ 583
[M þ 1]þ.

Heavy metal ion-selective
1927
The reduced macrocycle 6,7,9,10,12,13,15,16,23,24,26,27,30,31-tetradecahydro-
22H,29H-dibenzo[k,w][1,4,7,10,16,19,25,13,22]trioxatetrathiadiazacycloheptacosine (6)
was obtained (57% yield) from 5 by using sodium borohydride–boron trifluoride ethyl
etherate in dry THF at 0–5ꢁC under argon. Analytical and spectroscopic data of 6
clearly confirmed the reduction reaction. In the IR spectrum of 6, the stretching
vibrations belonging to C¼O in 5 were absent after reduction. Disappearance of the
singlets at ꢀ ¼ 3.72 ppm in the ꢁ-bisamide macrocyclic 6 and appearance of a singlet at
ꢀ ¼ 5.71 ppm for –NH and a triplet at ꢀ ¼ 2.98 ppm for –NCH2 confirmed the proposed
structure. The disappearance of the C¼O signals, along with the appearance of a new
peak at ꢀ ¼ 42.09 ppm for N–CH2 in the 13C-NMR spectrum of 6 can be taken as clear
evidence for the formation of reduced macrocycle. The expected molecular ion peak for
6 was observed at m/z ¼ 555 [M þ 1]þ.
The reaction of 3 with 2,20-dithioethanethiol and 4.5-fold excess of anhydrous K2CO3
in dry acetonitrile at room temperature under argon afforded 6,7,8,9,10,12,13,15,16,
26,27-decahydro-22H,29Hdibenzo[k,w][1,4,7,10,16,19,25,13,22]trioxapentathiadiazacy-
cloheptacosine-23,30(24H,31H)-dione (8) in 60% yield. The IR spectrum of 8 is almost
identical to that of 3 with small changes in wave numbers. The formation of macrocycle
was confirmed by appearance of a new resonance for S-CH2 at ꢀ ¼ 2.38 ppm as
multiplet in the 1H-NMR spectrum of 8 in CDCl3. The MS of 8 displayed the expected
molecular ion peak at m/z ¼ 681 [M þ K]þ.
The reduced macrocycle 6,7,9,10,12,13,15,16,23,24,26,27,30,31-tetradecahydro-22H,
29H-dibenzo[k,w][1,4,7,10,16,19,25,13,22]trioxapentathiadiazacycloheptacosine (9) was
obtained from 8 by using sodium borohydride–boron trifluoride ethyl etherate in dry
THF at 0–5ꢁC under argon in 88% yield. Analytical and spectroscopic data of 9 clearly
confirmed the success of the reduction. In the IR spectrum of 9, the stretching
vibrations belonging to C¼O group at 1682 cmꢂ1 in 8 were absent after reduction. The
disappearance of the singlets at ꢀ ¼ 8.36 ppm in 8 and appearance of a singlet at
ꢀ ¼ 5.42 ppm for –NH and a triplet at ꢀ ¼ 3.11 ppm for –NCH2 confirmed the proposed
structure. The disappearance of the C¼O signals, along with appearance of a new peak
at ꢀ ¼ 42.81 ppm for NCH2 in the 13C-NMR spectrum of 9 can be taken as a clear
evidence for formation of reduced macrocycle. The expected molecular ion peak for
9 was observed at m/z ¼ 615 [M þ 1]þ.
3.1. Extraction of metal picrates
Ni2þ, Mn2þ, Co2þ, Agþ, Cd2þ, and Pb2þ picrates were used in extraction studies.
The experiments were carried out at 25 ꢄ 0.1ꢁC with the solution of the ligands in
chloroform and dichloromethane.
The extractability of Ni2þ, Mn2þ, Co2þ, Agþ, Cd2þ, and Pb2þ picrates from the
aqueous phase into the chloroform phase by ligands is given in table 1. Ligand 3
extracts only Agþ effectively with 66.3%. Co2þ is extracted below 2.0% in this case.
This result shows that the polyether with an open ring, 3, shows important selectivity
for Agþ. Similar results were obtained for Hg2þ picrate with the similar diamide
compound without the oxyethylene moiety [16]. In the previous study, the extractability
was found only for Agþ at 5.2% with the diamide compound containing only sulfur
donors [16]. However, the introduction of three oxygen donors into the structure causes

1928
H. Kantekin et al.
Table 1. The extractability of aqueous metal picrates for 3, 5, 6, 8, and 9 into the chloroform phase.a
Extractability (%)
Metal ion
3
5
6
8
9
Ni2þ
Mn2þ
Co2þ
Agþ
51.0
51.0
51.0
3.5 ꢄ 0.1
51.0
51.0
51.0
51.0
5.0 ꢄ 0.3
1.5 ꢄ 0.1
2.0 ꢄ 0.1
5.4 ꢄ 0.2
51.0
51.0
51.0
1.2 ꢄ 0.9
51.0
51.0
66.3 ꢄ 0.5
51.0
87.4 ꢄ 0.7
9.7 ꢄ 0.9
22.8 ꢄ 0.5
82.4 ꢄ 0.2
87.1 ꢄ 0.9
Cd2þ
Pb2þ
51.0
51.0
51.0
51.0
51.0
aTemperature: 25.0 ꢄ 0.1ꢁC; aqueous phase (10 mL); [picꢂ] ¼ 1.25 ꢃ 10ꢂ5 mol Lꢂ1
,
organic phase (10 mL);
[L] ¼ 7.50 ꢃ 10ꢂ5 mol Lꢂ1; the values and SDs calculated from three independent extraction experiments.
Table 2. The extractability of aqueous metal picrates for 3, 5, 6, 8, and 9 into the dichloromethane phase.a
Extractability (%)
Metal ion
3
5
6
8
9
Ni2þ
Mn2þ
Co2þ
Agþ
4.3 ꢄ 0.1
13.7 ꢄ 0.2
5.2 ꢄ 0.4
80.4 ꢄ 0.5
51.0
51.0
51.0
51.0
62.0 ꢄ 0.2
43.6 ꢄ 0.1
51.0
87.2 ꢄ 0.6
3.5 ꢄ 0.6
49.1 ꢄ 0.4
37.2 ꢄ 0.1
10.6 ꢄ 0.3
4.5 ꢄ 0.1
51.0
51.0
83.4 ꢄ 0.5
92.1 ꢄ 0.5
51.0
10.5 ꢄ 0.2
10.0 ꢄ 0.1
93.2 ꢄ 0.8
33.1 ꢄ 0.2
10.2 ꢄ 0.1
Cd2þ
Pb2þ
51.0
4.1 ꢄ 0.1
51.0
aTemperature: 25.0 ꢄ 0.1ꢁC; aqueous phase (10 mL); [picꢂ] ¼ 1.25 ꢃ 10ꢂ5 mol Lꢂ1
,
organic phase (10 mL);
[L] ¼ 7.50 ꢃ 10ꢂ5 mol Lꢂ1; the values and SDs calculated from three independent extraction experiments.
an increment in the extractability of Agþ with 66.3%. Ligand 5 did not effectively
extract all metal cations; the extractability was only 3.5% for Mn2þ
.
It is clear that 6, which is the reduced form of 5, extracted all the tested metal cations
to chloroform except for Co2þ. This result shows that the reduced form in the
extraction with chloroform is less selective for Agþ with the macrocyclic diamide. As
seen from table 1, the extractability of Agþ (87.4%) increased compared to that of the
corresponding diamide 5. Ligand 8 has only one more sulfur donor than 5. However,
this increase in the number of sulfurs causes a pronounced effect in the extraction
efficiency of Agþ picrate. Agþ was extracted by 82.4% to the chloroform phase with 8,
while the extraction efficiency was below 1.0% with 5. This indicates the importance of
the number of donors in the macrocycle during the transport of Agþ. Another
interesting result seen from table 1 is the selective extraction of Agþ picrate with 9.
Ligand 9 is the reduced form of 8 and shows better selectivity for Agþ with respect to 6,
which has one less sulfur donor. Therefore, the results confirm that the number and the
kind of donors and their location in the cavity of the macrocyclic ligand are very
important in selective extraction. These are in agreement with the results for crown
ether ligands with mixed donors [8].
As seen from table 2, which shows the extractability results of the ligands to the
dichloromethane phase, 3 extracted all metal cations except Cd2þ, showing that
dichloromethane causes less selectivity in the extraction of the tested metal cation than
chloroform. When tables 1 and 2 are compared, it can be seen that dichloromethane is

Heavy metal ion-selective
1929
Table 3. The relationship between the composition and extraction constants for the
complexes of 6 and 9.
Ligand
Metal ion
6
9
a
b
a
(L : M)a
3 : 1
1 : 1
(log Kex
20.29
14.22
)
(L : M)b
3 : 1
(log Kex
17.54
–
)
(L : M)a
3 : 1
(log Kex
19.74
–
)
Agþ
Pb2þ
–
–
aDichloromethane.
bChloroform.
more effective in the extraction of Agþ picrate with respect to chloroform with 5 with
10.0% to the dichloromethane phase and 6 extracted all the metal cations to the
dichloromethane phase except Co2þ. The extractability of Ni2þ, Mn2þ, and Pb2þ
increased for dichloromethane with respect to chloroform with 6, showing that solvent
is important in the extraction efficiency. The values of extractability (%) in
dichloromethane increased to 62.0 and 43.6 for Ni2þ, and Mn2þ, respectively. We
found an increment in the extraction of Ni2þ, Mn2þ, and Co2þ with dichloromethane
with respect to chloroform for an aromatic macrocyclic ligand bearing nitrogen–sulfur
mixed donors [17]. The same effect was valid for Pb2þ and Cd2þ in the previous study
[17]. In this study, we obtained similar results except for Cd2þ with 6. Ligand 8
extracted all the metal cations with various extractability values (%)to dichlor-
omethane. The highest value was 93.2% for Agþ and the lowest value belongs to Co2þ
with 4.5%. When the extraction results of 5 and 8, diamide macrocycles, are compared,
5 is more selective but not as effective for Agþ, showing that the cavity size and the
number of donors of the macrocycle with nitrogen–sulfur–oxygen mixed donors are
significant in selective metal cation transport. Recently, we showed that diamide
macrocyclic ligands have more selectivity than the corresponding reduced macrocycles
[17, 18]. The extraction selectivity results of 5 and 6 agree with that of our previous
results. However, table 2 shows opposite results for 8 and its reduced form 9. The
reduced ligand (9) shows better selectivity for Agþ with respect to that of the
corresponding diamide 8 for dichloromethane. Another interesting result belongs to
Co2þ. As seen from table 2, 9 extracted Co2þ to dichloromethane in 83.4%, while the
same ligand extracted it to chloroform below 1.0% (table 1). It is clear that the solvent
has pronounced effect in the extraction of Co2þ ion with 9.
Table 3 gives the relationship between composition and extraction constants for the
complexes of 6 and 9 with Pb2þ and Agþ for chloroform and dichloromethane; 3 : 1
complex composition was obtained with these macrocycles for Agþ. However, the
log Kex value was higher for dichloromethane than chloroform. As seen from table 3, we
could not calculate the log Kex value for some cases in the extraction of Pb2þ because of
irregular evolution between log {D/[Picꢂ]n} and log [L]. The macrocycle (6) carrying
N2O3S4 donors transports Pb2þ to dichloromethane as a 1 : 1 complex, but the same
ligand forms the 3 : 1 complex with Agþ. The log Kex values for Pb2þ and for Agþ
complexes are 14.22 and 20.29, respectively. Agþ is extracted better than Pb2þ with 6 in
dichloromethane. This result is also confirmed by the extractability results of this ligand
in table 1. In table 3, the right-hand side shows the complex composition and extraction
equilibrium constants for the Agþ complex of 9 in dichloromethane. It is clear that the

1930
H. Kantekin et al.
6
5
4
3
2
1
0
Slope:3.1
–5.5
–5
–4.5
–4
log (L)
Figure 1. Log{D/[Picꢂ]n} vs. log [L] for the extraction of Ag picrate to dichloromethane phase with 9.
extraction equilibrium constant (log Kex) is lower for Agþ than 6. However, the complex
composition is the same 3 : 1 in this case. These results suggest that the extraction
constant depends on both the kind of solvent and the structure of the cation.
In order to determine the composition of extracted complexes, the effect of
changing ligand concentration over the distribution ratio at constant picrate concen-
tration was investigated. The plot of log {D/[Picꢂ]n} as a function of log [L] gave a
straight line with a slope of m and log Kex was calculated from the intercept by
equation (3). Figure 1 shows, in the case of dichloromethane, the evolution of log
{D/[Picꢂ]n} while increasing the concentration of 9 at constant picrate concentration
and the slope is calculated as 3.1, showing that the complex composition of extracted
species is 3 : 1(L : M) for Agþ.
Complex compositions were also confirmed with the molar ratio method. For this,
the extractability (%) of the ligands was plotted against the ratio of [ligand]/[metal].
Figure 2 shows the molar ratio plot for Agþ ion with 9, where the organic solvent was
dichloromethane and it clearly shows the formation of the 3 : 1 complex.
4. Conclusion
We have obtained two new macrocyclic diamides containing N2S4O3- and N2S5O3-
donors. These macrocyclic ligands were prepared by reaction of NaBH4 with
macrocyclic diamides in the presence of boron trifluoride ethyl etherate in dry THF.
The solvent extraction method was used to evaluate metal-ion binding properties of the
new ligands. Table 3 gives the relationship between composition and extraction
constants for the complexes of 6 and 9 with Pb2þ and Agþ for chloroform and
dichloromethane. Ligand 8 extracted all the metal cations with various extractability

Heavy metal ion-selective
1931
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
(L)/(M)
Figure 2. Dependence of extractability (%) of 9 on the concentration of Agþ in the extraction with
dichloromethane.
values (%)to dichloromethane. The highest value was 93.2% for Agþ, whereas the
lowest value belongs to Co2þ with 4.5%. When the extraction results of 5 and 8, which
are diamide macrocycles, are compared, 5 is more selective but not as effective for Agþ.
Acknowledgment
This study was supported by the Research Fund of Karadeniz Technical University,
Project no: 2004.111.002.6 (Trabzon/Turkey).
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