Synthesis and extraction results of new halide terminated 2-alkyl-p-tert-butylcalix[4]arenes bearing phosphine oxides or ketones on the narrow rim

Article abstract of DOI:10.1016/j.tet.2015.12.038

The synthesis of lower rim tetraphosphorylated and tetraketone calix[4]arenes with haloalkyl groups tethered to a single methylene bridge and their utilization as extraction agents for rare earth elements are reported. Synthesis of these new functionalized calix[4]arene species has been achieved in good to modest yields, and extraction of nine lanthanide nitrates has been explored using these novel calix[4]arene species. The tetraphosphorylated calix[4]arenes show better lanthanide extraction efficiency than their ketone counterparts, especially for europium (III). These experiments demonstrate that inclusion of a substituent tethered to the methylene bridge does not significantly reduce the extraction efficiency of these new calix[4]arene ligands as compared to similar unsubstituted ligands in literature, making them important precursors in the development of functionalized stationary phases for separation of lanthanides. Development of similar CMPO-bearing narrow rims and new solid-phase extraction materials for the solid-liquid separation of lanthanides remains the subject of future work.

Full text of DOI:10.1016/j.tet.2015.12.038

Accepted Manuscript
Synthesis and extraction results of new halide terminated 2-alkyl-p-tert-
butylcalix[4]arenes bearing phosphine oxides or ketones on the narrow rim
Sreejit R. Menon, Joseph A.R. Schmidt
PII:
S0040-4020(15)30286-6
10.1016/j.tet.2015.12.038
TET 27364
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 6 November 2015
Revised Date: 15 December 2015
Accepted Date: 17 December 2015
Please cite this article as: Menon SR, Schmidt JAR, Synthesis and extraction results of new halide
terminated 2-alkyl-p-tert-butylcalix[4]arenes bearing phosphine oxides or ketones on the narrow rim,
Tetrahedron (2016), doi: 10.1016/j.tet.2015.12.038.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Synthesis and extraction results of new halide terminated 2-alkyl-p-tert-butylcalix[4]arenes
bearing phosphine oxides or ketones on the narrow rim
Sreejit R. Menon, Joseph A. R. Schmidt*
Department of Chemistry & Biochemistry
School of Green Chemistry & Engineering
College of Natural Sciences & Mathematics
The University of Toledo
2801 W. Bancroft St. MS 602
Toledo, Ohio 43606-3390, USA
*Corresponding author. Tel.: +1-419-530-1512; Fax: +1-419-530-4033
Email address: Joseph.Schmidt@utoledo.edu
Keywords:
f-block elements, separation of lanthanides, 2-substituted haloalkyl calix[4]arenes,
tetraphosphorylated calix[4]arenes, liquid-liquid extraction
1

ACCEPTED MANUSCRIPT
Abstract:
The synthesis of lower rim tetraphosphorylated and tetraketone calix[4]arenes with haloalkyl
groups tethered to a single methylene bridge and their utilization as extraction agents for rare
earth elements are reported. Synthesis of these new functionalized calix[4]arene species has been
achieved in good to modest yields, and extraction of nine lanthanide nitrates has been explored
using these novel calix[4]arene species. The tetraphosphorylated calix[4]arenes show better
lanthanide extraction efficiency than their ketone counterparts, especially for europium (III).
These experiments demonstrate that inclusion of a substituent tethered to the methylene bridge
does not significantly reduce the extraction efficiency of these new calix[4]arene ligands as
compared to similar unsubstituted ligands in literature, making them important precursors in the
development of functionalized stationary phases for separation of lanthanides. Development of
similar CMPO-bearing narrow rims and new solid-phase extraction materials for the solid-liquid
separation of lanthanides remains the subject of future work.
1. Introduction:
The rare earth elements (REEs), composed primarily of the fifteen lanthanides, find broad
application in many modern devices, ranging from use as magnets in wind turbines, hard drives,
and air conditioners to incorporation in hybrid car batteries.1,2 These elements have proven
indispensable to the sustainable and green world approach prevalent in modern society.3 China
has been a key player in REE production over the past several decades. Recent decisions to
significantly reduce export quotas of these valuable minerals to ostensibly meet Chinese
domestic requirements has resulted in increased tariffs and thereby an economic driving force to
look for alternative sources of REEs.4 Isolation and purification of REEs from mineral deposits
has always been a lengthy and laborious task for the mining industry. Separation techniques
currently employed for this processing generate undesirably large quantities of waste due to the
chemical treatments that are necessary to process the raw ore and subsequently separate
individual REEs, contributing significantly to their cost.5 In addition to their production from
raw ores, the idea of recovering REEs from stored nuclear waste is quite attractive. High-level
nuclear wastes (HLWs), obtained as secondary waste after separation of uranium or plutonium
2

ACCEPTED MANUSCRIPT
from a nuclear reactor’s depleted fuel are composed of fission products including minor actinides
like Am and Cm, as well as lanthanides including Nd, Gd, Eu, and Sm.6,7 The recovery of
lanthanides at this stage of nuclear waste management will not only help meet lanthanide
production requirements, but will also reduce the total quantity of waste requiring long term
storage.7 Another potentially valuable source of lanthanides involves their recovery from
outdated electronic devices and materials that have completed their functional lifetime. The
effective utilization of each of these lanthanide sources requires improved methods and
techniques that will in turn lead to better, cleaner, and more economical processes for the
separation and isolation of REEs.1
Over the past decade, much effort has been invested toward improving the separation of
lanthanides.8,9 Primarily, research in this field has focused on liquid–liquid extraction (LLE)
techniques employing coordinating solvents, ionic liquids, or multivalent coordinating ligands
assembled on scaffolds such as calixarenes to separate these elements from other metals and
earthly impurities.7,9 In general, many of the LLE studies previously disclosed have shown
significantly improved extraction efficiencies compared to the currently employed industrial
separation techniques.8,10-12 Despite these advances, these new methods still suffer from the
general drawbacks affiliated with LLE, including high solvent and ligand cost and large
quantities of chemical waste.
Calixarenes have been widely employed in extraction chemistry over the last two decades.7,13-15
These cyclic oligomers are readily produced via the condensation of t-butylphenol with
formaldehyde under basic conditions.16 The cup-shaped macrocyclic structure of a calixarene
provides sites for easy modification and functionalization on its upper and lower rims (Figure 1),
making it attractive as a scaffold/platform for attachment of monovalent ligating units. The
3

ACCEPTED MANUSCRIPT
incorporation of several monovalent ligating units to a single rigid calixarene core results in the
formation of a multivalent ligand system. Calixarene-based ligands have proven to be useful for
applications in the biomedical field, including ion and molecular recognition.13-15 They have also
been used in metal recovery and waste treatment as highly selective and efficient extraction
agents for alkali, transition, and heavy metals due to their ability to effectively chelate these
metal ions strongly.7,17,18 Upper and lower rim-functionalized calixarenes have displayed
excellent extraction efficiency in various LLE processes. In particular, calixarenes with amines,
amides, esters, ketones, or phosphine oxides on the lower rims have proven to be very effective
in the areas of ion recognition and LLE.10,19-21 Tailoring the groups present on the lower rim has
led to successful extraction of alkaline, alkaline earth, or transition metals, and has also been
successful in the extraction and separation of lanthanides and actinides from radioactive
wastes.19,20,22,23 Despite their excellent extraction capabilities, calixarenes are often overlooked
industrially due to the financial drawbacks inherent with LLE. For the separation of lanthanides,
this is often a laborious, time-consuming process accompanied by difficulty in layer separation
due to the formation of emulsions. Also, LLE is not a green process as large quantities of organic
solvents are necessary, resulting in significant amounts of waste, subsequently requiring further
treatment or disposal and thus increasing costs.5-7
Given the limitations of LLE, several investigators have explored the related solid phase
extraction (SPE) approach.24 SPE provides numerous advantages, including reduced volumes of
organic solvents, capacity for large-scale separations, and automation of the extraction process,
making it a much more economical and greener process. Functionalized calixarenes have been
made heterogeneous by immobilization on solid supports, including silica and polymers such as
polystyrene through reactions to covalently link their lower or upper rims to the solid support.24-
4

ACCEPTED MANUSCRIPT
26
Unfortunately, attachment via the upper or lower rims has significantly reduced the ability of
these ligands to effectively coordinate to metal centers, resulting in drastically reduced extraction
efficiencies attributed to reduced flexibility in these molecules. In order to mitigate the
detrimental effects resulting from covalent linkage to these solid supports, our group is
investigating the methylene bridges on the calixarenes as the point of attachment. We believe
that covalent attachment through these methylene units will have little or no effect on the
conformational flexibility of the calixarene in the resultant material. Fantini demonstrated a
simple one-pot synthetic route to selectively monofunctionalize a methylene bridge of
calix[4]arenes.27 In collaboration with Fantini, our group previously designed and demonstrated
synthetic routes to 2-(ω-haloalkyl)-calix[4]arenes with 3-6 carbon spacer alkyl chains.28 The
longer five-carbon and six-carbon alkyl tethers are preferred as they will help to physically
separate the functionalized calix[4]arene ligand from a solid support like silica upon which they
will be immobilized in the future, thereby minimizing interactions between the ligand, an
extracted metal ion and the surface of the solid support. Herein, we detail the incorporation of
coordinating ligands such as phosphine oxides and ketones at the lower rim of the
aforementioned 2-functionalized haloalkyl-calix[4]arenes. Furthermore, we report the utilization
of these new molecules in LLE experiments involving lanthanide nitrate solutions as a means to
investigate the effect of the long alkyl tail at the methylene bridge on extraction efficiencies of
lower rim coordinating groups. These new ligands will be further modified at their halide
terminated end and will ultimately be immobilized on solid supports through this modified end in
our future efforts to produce improved materials for SPE of lanthanides.
5

ACCEPTED MANUSCRIPT
Figure 1. Calix[4]arene: (i) flat line drawing with numbering, (ii) three dimensional perspective,
and (iii) similarity to a basket.
Scheme 1. Synthesis of 2-(ω-chloroalkyl)-tetramethoxy-p-tert-butylcalix[4]arenes. 28
Scheme 2. Synthesis of 2-(ω-chloroalkyl)-tetrahydroxy-p-tert-butylcalix[4]arenes.
6

ACCEPTED MANUSCRIPT
Scheme 3. Synthesis of 2-(ω-chloroalkyl)-tetra-(diphenylphosphonylmethyl)-p-tert-
butylcalix[4]arenes.
Scheme 4. Synthesis of 2-(ω-iodoalkyl)-tetra-(pivaloylmethyl)-p-tert-butylcalix[4]arenes.
7

ACCEPTED MANUSCRIPT
Figure 2. Percent extraction (%E) for the lanthanide ions with ligands 5, 6a and 6b;
concentration of ligand (CL=2.5×10–2 M) in dichloromethane, concentration of lanthanide
nitrates (CLn=1×10–4 M) in 1 M HNO3.
8

ACCEPTED MANUSCRIPT
2. Results and discussion
2.1. Synthesis and characterization
Synthesis of 2-(ω-chloroalkyl)-tetramethoxy-p-tert-butylcalix[4]arenes 3a and 3b (Scheme 1)
proceeded as reported by our group in 2009.28 To extend that work, we sought to functionalize
the narrow lower rim with suitable coordinating ligands for lanthanide ions, such as phosphine
oxides or ketones. Ligands bearing oxygen donor atoms like phosphine oxides, phosphonates,
amides, carboxylic acids, and ketones on the lower rims have been extensively investigated in
extraction and separation of actinides and rare earth metals in the last two decades.7 As noted in
previous studies, hydroxyl groups on the lower rims can be readily transformed to the desired
phosphine oxide or keto groups.29,30 Thus, the tetramethoxy-calix[4]arenes 3a and 3b were first
subjected to exhaustive demethylation using BBr3 in CH2Cl2 overnight, followed by basic
hydrolysis to yield the 2-(ω-chloroalkyl)-tetrahydroxy-p-tert-butylcalix[4]arenes 4a and 4b
1
(Scheme 2). The H NMR spectra of 4a and 4b each showed a resonance for the hydroxyl
protons at
δ 10.32 ppm, while the absence of a resonance for the methoxy protons indicated
complete conversion. The NMR spectra (collected in CDCl3) showed that 4a and 4b each adopt a
full cone conformation in solution, due to the strong hydrogen bonding now present at the lower
rim unlike the tetramethoxy derivatives 3a and 3b, which were fluxional in solution.28
Furthermore strong broad peaks at ~3185 cm–1 in the IR spectra also confirmed the presence of
hydroxyl groups on the lower rim.
Simple Williamson etherification of 1 and 4 with Ph2P(O)CH2OTs using NaH as the base in
toluene yielded the crude tetraphosphorylated species 5, 6a, and 6b in poor to moderate
conversion after extended heating for 6 days (Scheme 3).29 The incorporation of the bulky
diphenylphosphine oxide groups at the lower rim resulting in a sluggish reaction. Examination of
9

ACCEPTED MANUSCRIPT
the crude material by NMR showed the presence of partially phosphinylated species, but did not
reveal any peaks attributable to side products as might be expected from an elimination reaction
to form an alkene at the terminus of the alkyl tether. Silica column purification yielded pure 5,
6a, and 6b, each of which was identified using 1H, 13C and 31P NMR spectroscopy in CDCl3. The
1H NMR spectra showed multiplets at 7.60–7.90 ppm and 7.10–7.40 ppm, corresponding to the
lower rim diphenyl phosphine oxide moieties. The most notable resonances in the 13C NMR
spectra were the methylene carbon resonances adjacent to the phosphorus atoms (–CH2P(O)Ph2),
1
appearing as two doublets at 71.7 and 71.4 ppm with large JPC coupling constants (77.1 Hz).
3
Additionally two doublets between 152 and 154 ppm were observed, corresponded to JPC
coupling of the quarternary carbons (C–O–CH2P). Two phosphorus resonances were observed in
the 31P NMR spectra, consistent with the presence of two non-equivalent phosphorus atoms in
these molecules. These results confirmed the cone conformation in solution for these molecules,
which is maintained due to the steric bulk of the diphenyl phosphine oxide ligands now attached
on the lower rims, making it impossible to fit through the calix[4]arene core and preventing
conformational fluxionality. Additionally, the various NMR spectra verified the Cs symmetry of
6a and 6b resulting from the single methylene functionalized alkyl tether in those species. These
reaction products were further confirmed by mass spectrometry with the observation of [M+H]+
peaks and IR spectroscopy, which showed a peak at 1197 cm–1 corresponding to P=O
vibrations.31
The tetraketone species 7, 8a and 8b were synthesized by extended heating of 1 and 4 in dry
acetone along with K2CO3 and 1-bromopinacolone for 6 days (Scheme 4).30 KI was also added to
the reaction mixture in order to increase the rate of the substitution reaction utilizing the
Finkelstein effect. The resulting products were crystallized from ethanol to yield pure 8a and 8b
10

ACCEPTED MANUSCRIPT
1
in modest yields. The identities of these compounds were confirmed by H and 13C NMR
spectroscopy with diagnostic resonances including the 13C peaks for the carbonyl carbon (C=O)
and the methylene carbon adjacent to the carbonyl group (–CH2C(O)–). As in the previous cases,
these molecules also adopt a cone conformation in solution, as confirmed by the NMR
spectroscopic data in CDCl3. Mass spectrometry revealed the presence of an iodo-terminated
tether instead of the expected chloro-terminated tether, as indicated by the higher mass [M+Na]+
peak observed for 8a and 8b, which was attributed to a simultaneous Finkelstein reaction taking
place at the tether’s end.28 IR spectroscopy further confirmed the presence of the keto group
bound to the lower rim with the characteristic C=O vibrations appearing at ~1720 cm–1. All of
the new molecules described herein are summarized in Table 1.
2.2. Liquid-liquid extraction of lanthanides
The LLE experiments carried out in this study are based on HSAB theory, wherein a hard acid,
the trivalent lanthanide ion (Ln3+), is coordinated by dative interactions from a hard donor atom
like oxygen in P=O or C=O groups present on the lower narrow rim of the calix[4]arene
ligand.32,33 The extraction efficiency of these new phosphine oxide (6) and ketone (8) based
calix[4]arene ligands toward nine lanthanide nitrates was studied and the results are summarized
in Figures 2 and S1, respectively (see Supporting Information). These results were compared to a
related previous study20 and also provide the groundwork for the future development of these
ligands for separation and isolation of lanthanides in heterogeneous systems. The data reported
herein provides a direct comparison of the effect of the 2-position haloalkyl tail on the extraction
ability of the lower rim substituted calix[4]arenes with coordinating phosphine oxide and ketone
groups compared to the native unsubstituted calix[4]arenes.
11

ACCEPTED MANUSCRIPT
Figure 2 shows the percent extraction (%
E
) results for the new lower rim phosphine oxide
molecules 6a and 6b in the LLE of lanthanide nitrates in aqueous 1 M HNO3 solution to the
organic dichloromethane phase (CH2Cl2). The %
E of these trivalent metal ions was also
determined from experimental extraction data obtained using the native lower rim phosphine
oxide molecule 5, which has been previously reported in the literature.20 Figure 2 clearly
demonstrates that Eu3+ is favored over other ions across the lanthanide series. In general, the
percent extraction of Eu3+ with 5 is quite comparable to the reported value20 (red bar in Figure
2), while it can be seen that ligands 6a and 6b show slightly reduced extraction efficiencies for
Eu3+ compared with 5. The extraction efficiency of the ligands toward Eu3+ decreases in the order
5>6a>6b, showing that the calix[4]arenes with increasing number of carbon atoms in the
haloalkyl tail experience a slight reduction in extraction efficiency. This order is maintained for
all the lanthanide ions studied in this work. This decreased extraction efficiency of the alkyl
tailed species compared to the unsubstituted species can be attributed to a number of factors:
unfavorable spatial orientation of the four coordinating P=O groups on the lower rim due to the
presence of the 2-position alkyl tail, hindering flexibility/mobility of the diphenyl phosphine
oxide groups adjacent to the methylene bridge having the tail, and also the possibility of the
highly flexible tail bending into the cavity made by the lower rim P=O ligands, thereby
preventing the lanthanide ions from entering the lower cavity and reducing the coordinative
interactions with the oxygen atoms. The order of extraction of these rare earth metal ions
decreases as follows: Eu3+>Sm3+>Gd3+>Pr3+>La3+>Gd3+>Dy3+≥Yb3+>Nd3+>Ce3+. A number of
factors such as electronics, size of the metal ion, steric effects, and spatial orientation of
coordinating groups of the ligands all working in tandem could impact the selectivity observed
during extraction. As shown in Figure 2, as the size of the metal ion decreases from La3+ to Eu3+,
12

ACCEPTED MANUSCRIPT
the extraction efficiency increases, with Ce3+ and Nd3+ being slight outliers. However, this trend
reverses upon moving from Eu3+ to Yb3+ as the size of the metals continues to decrease. This
data indicates that the cavity formed by the orientation of the four phosphine oxide groups on the
lower rim provides the perfect size for Eu3+ coordination by the oxygen atoms of P=O. The
reduced extraction efficiency moving away from Eu3+ in either direction shows that as the metal
becomes larger or smaller, the ionic radius and cavity size mismatch reduces the utility of these
ligands. Slight deviations from this trend with other metal ions highlight the fact that not just the
size, but also the electronics of these metal ions, is important, with both working in tandem to
determine the ability of each ligand to extract a certain metal ion. The high selectivity for Eu3+
observed with ligands 6a and 6b, as clearly demonstrated by the large difference in
D values
(Table 2) and lower extraction efficiency of these ligands toward other trivalent metal ions, can
be developed as a useful technique in the separation of Eu3+ from mixtures of lanthanide ions in
future work.
The same set of trivalent lanthanide ions was subjected to LLE using the ketone-functionalized
lower rim calix[4]arene ligands 7, 8a, and 8b. The results of these extractions are depicted in
Figure S1 (see Supporting Information). The extraction efficiencies of ketone derivatives are in
striking contrast to the results obtained for the phosphine oxide lower rims. Virtually no
extraction occurred for the nine lanthanide ions tested (Table S1). The cavity size formed by the
orientation of these carbonyl groups, governed by their bulky t-butyl groups, and the
significantly reduced polarity of the C=O bonds compared to the P=O bonds in the phosphine
oxide groups both contribute to the lack of effective extraction. Furthermore, no complex
formation was observed when lanthanum nitrate or praseodymium nitrate hexahydrate was added
to a methanol solution of 7 or 8a and stirred at room temperature overnight, whereas complex
13

ACCEPTED MANUSCRIPT
formation was seen with both 5 and 6a.31 From the results obtained, ketone derivatives have
proven to be a poor choice as extracting agents for lanthanide ions.
In summary, the incorporation of a haloalkyl-tail on the 2-position of a calix[4]arene decreases
its extraction ability slightly, but could prove to be a very useful tool in the separation of
lanthanides once these tail-ends are immobilized on a solid support in the development of new
heterogeneous materials. Overall, the phosphine oxide derivatives worked substantially better
than the ketone derivatives and high selectivity for europium was achieved with the diphenyl
phosphine oxide lower rims 6a and 6b.
3. Conclusion
New calix[4]arene ligands 4a and 4b were successfully synthesized and used as precursors to
make functionalized calix[4]arene derivatives incorporating four phosphine oxides (6a and 6b)
or tert-butylketones (8a and 8b) on their lower rims. Each of these molecules was fully
characterized using NMR techniques, mass spectrometry, and IR spectroscopy. The new ligands
(6a, 6b, 8a and 8b) were then used in LLE studies with nine lanthanide nitrates. The phosphine
oxide derivatives showed selectivity among the various lanthanides as well as excellent
extraction efficiency for Eu3+. The phosphine oxide calix[4]arene derivatives with haloalkyl tails
(6a and 6b) showed slightly lower extraction efficiencies compared to the non-tail species 5;
however, all the phosphine oxide species are far better extracting agents than the ketone
derivatives. These experiments thus demonstrated that the presence of an alkyl tail attached to
the methylene bridge of a calix[4]arene does not significantly reduce its extraction efficiency
compared to the unsubstituted analogues, making these functionalized calix[4]arenes useful
precursors for the development of new heterogeneous supports unlike calix[4]arenes with
substituents attached to the upper or lower rims, which display significantly reduced extraction
14

ACCEPTED MANUSCRIPT
efficiencies. These new 2-position substituted calix[4]arenes with lower rim phosphine oxides
will hence be further utilized in our group to develop new heterogeneous materials for the
effective separation of lanthanides. Similarly the group plans to synthesize the CMPO analogues
on the narrow rim of calix[4]arenes and immobilize them onto solid supports.
4. Experimental section
4.1. Materials and reagents
Compounds 1,34 2, 3a,28 3b,28 529 and 730 were synthesized as previously reported. Schlenk and
glove box techniques were used in the synthesis of compounds 4a, 4b, 6a, 6b, 8a and 8b. The
following reagents were used as received from commercial suppliers: methanol, ethanol,
dichloromethane, pentane, sodium carbonate, potassium carbonate, potassium iodide, methyl
iodide, n-butyllithium (1.6 M in hexane), 1-bromo-5-chloropentane, 1-bromo-6-chlorohexane,
boron tribromide (BBr3), diphenylchlorophosphine, 1-bromopinacolone and silica gel (porosity:
60 Å, particle size: 40–63 µm). Sodium hydride (NaH) in mineral oil (60% by weight) was
washed with pentane under N2 atmosphere, placed under vacuum to remove solvents/volatiles
after washing, and taken into the glove box to be stored for further use. Tetrahydrofuran was
dried and purified by distillation from Na/benzophenone ketyl solution. Reaction solvents
including dichloromethane and toluene were dried over 4 Å molecular sieves with an MBraun
solvent purification system. Acetone for reaction was dried by stirring over dry calcium sulfate
overnight and cannula filtered under nitrogen. Ph2P(O)CH2OTs was synthesized under ambient
conditions as reported in literature.35 All of the lanthanides tested (La3+, Ce3+, Pr3+, Nd3+, Sm3+,
Eu3+, Gd3+, Dy3+, Yb3+) were used as nitrate salts and purchased from Strem Chemicals. The
15

ACCEPTED MANUSCRIPT
spectrophotometric determination of lanthanides was carried out in the presence of Arsenazo
(III) indicator.36,37
4.2. Instruments and apparatus
1
A 400 MHz Varian or 600 MHz Inova NMR spectrometer was used to obtain the H NMR and
13C NMR spectra at 399.9 MHz or 599.9 MHz and 100.6 MHz or 150.8 MHz, respectively, at
ambient temperature. A Varian 400 MHz spectrometer was used to record 31P NMR data at
161.9 MHz at ambient temperature and referenced to 0.0 ppm externally using a 5% solution of
H3PO4 in D2O. The NMR spectra were acquired in CDCl3 unless otherwise specified. NMR
spectra of 2, 3a and 3b made use of a 3:1 CDCl3/CD3CN solution containing NaI (1 g in 80 ml)
1
13
as reported in our group’s earlier work.27,28 The H and C NMR shifts are reported relative to
CHCl3 (7.26 ppm) and CDCl3 (77.3 ppm), respectively. High-resolution time-of-flight or
quadrupole mass spectra were obtained from electrospray ionization carried out at the Mass
Spectrometry Laboratory at the University of Illinois, Urbana, IL. Methanol was used to prepare
the electrospray samples. A Thermo Scientific Evolution 300 UV–vis spectrophotometer was
used to record the UV–vis spectra. IR spectra were recorded using a Perkin Elmer Spectrum 2
FT-IR spectrometer. Melting points of compounds were taken in a Uni-Melt capillary melting
point apparatus.
4.3. General
procedure
for
synthesis
of
2-(ω-chloroalkyl)-tetrahydroxy-p-tert-
butylcalix[4]arenes (4a and 4b)
To a 250 ml Schlenk flask kept in an acetone-dry ice bath (–37 °C) containing 3 (1–10 g)
dissolved in dry dichloromethane under nitrogen, 10 equivalents of boron tribromide (BBr3)
were added slowly using a syringe.38 The pale yellow solution turned brown in color over the
16

ACCEPTED MANUSCRIPT
period of addition of BBr3. This reaction was allowed to stir for 2 h in the acetone-dry ice bath
and further allowed to stir overnight for about 12 h at room temperature. The pale brown solution
was then poured over ice and neutralized with sodium bicarbonate to give a pH of 7–8. The
CH2Cl2 layer was washed twice with sodium bicarbonate solution, followed by two water
washes. The collected aqueous layers were back extracted with CH2Cl2 and combined with the
organic fraction. The organic fraction was then dried over MgSO4, filtered and concentrated on a
rotavap to yield an off-white solid.
4.3.1 2-(5-Chloropentyl)-tetrahydroxy-p-tert-butylcalix[4]arene (4a)39
Reagents: 3a (9.0 g, 11 mmol); BBr3 (10.6 mL, 111 mmol); CH2Cl2 (120 mL). Yield: 7.6 g
1
4
(91%); mp 214–218 °C; H NMR (399.9 MHz, CDCl3):
δ
10.32 (s, 4H), 7.13 (d, 2H, JHH=2.0
4
4
4
Hz), 7.10 (d, 2H, JHH=2.0 Hz), 7.08 (d, 2H, JHH=2.0 Hz), 7.02 (d, 2H, JHH=2.0 Hz), 4.51 (t,
1H, 3JHH=7.6 Hz), 4.28 (d, 1H, 2JHH=14.0 Hz), 4.27 (d, 2H, 2JHH=14.0 Hz), 3.54 (t, 2H, 3JHH=7.2
2
2
3
Hz), 3.53 (d, 1H, JHH=14.0 Hz), 3.52 (d, 2H, JHH=14.0 Hz), 2.22 (q, 2H, JHH=7.2 Hz), 1.79
3
3
(quint, 2H, JHH=7.2 Hz), 1.54 (quint, 2H, JHH=7.2 Hz), 1.38 (m, 2H), 1.24 (s, 18H), 1.23 (s,
18H); 13C{1H} NMR (100.6 MHz, CDCl3):
δ
147.0, 146.9, 144.6, 144.5, 131.2, 128.0, 127.7,
127.5, 126.2, 126.1, 125.5, 121.9, 45.3, 35.8, 34.5, 34.3, 33.0, 32.9, 32.7, 32.4, 31.7, 27.5,
27.1; IR (cm–1): 3189 (str, b, O–H), 2869 (m), 1483 (m), 1462 (m), 1395 (m), 1364 (w), 1202
(w), 1122 (w); ESI-HRMS calcd: C49H66ClO4 [M+H]+: 753.4650, found: 753.4644.
4.3.2 2-(6-Chlorohexyl)-tetrahydroxy-p-tert-butylcalix[4]arene (4b)
Reagents: 3b (10.0 g, 12.2 mmol); BBr3 (11.6 mL, 122 mmol); CH2Cl2 (120 mL). Yield: 7.9 g
1
4
(84%); m.p. 219–221 °C; H NMR (599.9 MHz, CDCl3):
δ
10.32 (s, 4H), 7.15 (d, 2H, JHH=2.4
4
4
4
Hz), 7.12 (d, 2H, JHH=2.4 Hz), 7.10 (d, 2H, JHH=2.4 Hz), 7.05 (d, 2H, JHH=2.4 Hz), 4.53 (t,
17

ACCEPTED MANUSCRIPT
1H, 3JHH=7.2 Hz), 4.31 (d, 1H, 2JHH=13.2 Hz), 4.29 (d, 2H, 2JHH=13.8 Hz), 3.56 (t, 2H, 3JHH=7.2
2
2
3
Hz), 3.56 (d, 1H, JHH=13.2 Hz), 3.54 (d, 2H, JHH=13.8 Hz), 2.23 (q, 2H, JHH=7.2 Hz), 1.80
3
(quint, 2H, JHH=7.2 Hz), 1.46 (m, 4H), 1.39 (m, 2H), 1.27 (s, 18H), 1.26 (s, 18H); 13C{1H}
NMR (100.6 MHz, CDCl3):
δ 147.0, 146.9, 144.6, 144.5, 131.3, 128.0, 127.8, 127.5, 126.2,
126.1, 125.5, 122.0, 45.3, 35.7, 34.5, 34.3, 33.0, 32.8, 32.3, 31.8, 31.7, 31.6, 29.0, 27.9, 27.0; IR
(cm–1): 3183 (str, b, O–H), 2867 (m), 1482 (m), 1463 (m), 1393 (w), 1362 (w), 1201 (w), 1121
(w); ESI-HRMS calcd: C50H68ClO4 [M+H]+: 767.4806, found: 767.4796.
4.4. General procedure for synthesis of 2-(ω-chloroalkyl)-tetra-(diphenylphosphonylmethyl)-p-
tert-butylcalix[4]arenes (6a and 6b)
Syntheses of compounds 6a and 6b were carried out similarly to the published synthesis of tetra-
(diphenylphosphonylmethyl)-p
-tert-butylcalix[4]arene 5.29 In a 250 ml flask under nitrogen, a
suspension of 4a or 4b (1–8 g) and NaH (6 equivalents) in dry toluene was refluxed for 6 h.
After cooling to ambient temperature, Ph2P(O)CH2OTs, synthesized as given in the literature,
was added to the suspension and refluxed for 6 days. Water (10 ml) was added to the brown-
colored reaction mixture under nitrogen to quench any unreacted NaH at the end of the sixth day.
The organic toluene layer was then washed twice with water, dried over MgSO4, filtered, and the
toluene was removed under reduced pressure on a rotavap to yield a brown crystalline powder.
Purification using silica column flash chromatography (pentane:ethyl acetate:methanol;
8:1.5:0.5) gave a fine crystalline white solid after concentration of the isolated pure column
fraction, which was monitored by thin layer chromatography (TLC).
4.4.1 2-(5-Chloropentyl)-tetra-(diphenylphosphonylmethyl)-p-tert-butylcalix[4]arene (6a)
18

ACCEPTED MANUSCRIPT
Reagents: 4a (4.1 g, 5.4 mmol); NaH (0.81 g, 33 mmol); Ph2P(O)CH2OTs (10.4 g, 27.2 mmol);
toluene (160 mL). Yield: 2.7 g (31%); mp >250 °C; 1H NMR (399.9 MHz, CDCl3):
δ
7.85–7.68
4
4
and 7.35–7.19 (m, 40H, PPh2), 6.50 (d, 2H, JHH=2.4 Hz), 6.41 (d, 2H, JHH=2.4 Hz), 6.32 (d,
4
2
3
2H, 4JHH=2.4 Hz), 6.28 (d, 2H, JHH=2.4 Hz), 5.35 (d, 2H, JHH=15.2 Hz), 5.19 (t, 1H, JHH=7.2
2
2
Hz), 5.17 (s, 4H), 5.15 (d, 2H, JHH=15.2 Hz), 4.87 (d, 2H, JHH=13.2 Hz), 4.85 (d, 1H,
3
2
2
2JHH=13.0 Hz), 3.50 (t, 2H, JHH=6.8 Hz), 2.79 (d, 2H, JHH=13.2 Hz), 2.58 (d, 1H, JHH=13.0
3
Hz), 1.87 (m, 2H), 1.79 (quint, 2H, JHH=6.8 Hz), 1.54 (m, 4H), 0.95 (s, 18H), 0.92 (s, 18H);
3
13C{1H} NMR (100.6 MHz, CDCl3):
δ
153.3 (d, JPC=4.0 Hz, quaternary
C
–O), 152.9 (d,
3JPC=4.0 Hz, quaternary C–O), 145.0, 144.9, 136.8, 133.8, 133.6, 133.5, 132.6, 132.4, 132.3 (d,
3
1JPC=95.8 Hz, quaternary Ar), 131.4 (d, JPC=10.8 Hz, Ar), 131.3 (d, 2JPC=9.1 Hz, Ar), 131.2 (d,
4JPC=3.3 Hz, Ar), 128.6 (d, 4JPC=5.4 Hz, Ar), 128.5 (d, 2JPC=7.7 Hz, Ar), 128.4 (d, 3JPC=11.2 Hz,
1
1
Ar), 124.9, 124.8, 121.7, 71.7 (d, JPC=77.1 Hz, –
C
H2P(O)Ph2), 71.3 (d, JPC=77.1 Hz, –
C
H2P(O)Ph2), 45.5, 36.8, 33.9, 33.8, 33.0, 32.9, 32.2, 31.5, 31.4, 27.9, 27.8; 31P{1H} NMR
(161.9 MHz, CDCl3):
δ
26.8, 26.0; IR (cm–1): 2986 (m), 1592 (w), 1479 (m), 1362 (w), 1197 (m,
P=O), 1120 (m), 1102 (w); ESI-HRMS calcd: C101H110ClO8P4 [M+H]+: 1609.6840, found:
1609.6755.
4.4.2 2-(6-Chlorohexyl)-tetra-(diphenylphosphonylmethyl)-p-tert-butylcalix[4]arene (6b)
Reagents: 4b (4.5 g, 5.9 mmol); NaH (0.84 g, 35 mmol); Ph2P(O)CH2OTs (11.3 g, 29.3 mmol);
toluene (160 mL). Yield: 2.3 g (24%); mp >250 °C; 1H NMR (399.9 MHz, CDCl3):
δ
7.86–7.69
4
4
and 7.37–7.22 (m, 40H, PPh2), 6.51 (d, 2H, JHH=2.4 Hz), 6.42 (d, 2H, JHH=2.4 Hz), 6.32 (d,
4
2
3
2H, 4JHH=2.4 Hz), 6.29 (d, 2H, JHH=2.4 Hz), 5.36 (d, 2H, JHH=15.2 Hz), 5.19 (t, 1H, JHH=6.8
2
2
Hz), 5.18 (s, 4H), 5.14 (d, 2H, JHH=15.2 Hz), 4.88 (d, 2H, JHH=13.2 Hz), 4.86 (d, 1H,
19

ACCEPTED MANUSCRIPT
3
2
2
2JHH=13.2 Hz), 3.52 (t, 2H, JHH=6.4 Hz), 2.78 (d, 2H, JHH=13.2 Hz), 2.60 (d, 1H, JHH=13.2
Hz), 1.87 (m, 2H), 1.74 (quint, 2H, 3JHH=6.4 Hz), 1.57 (m, 2H), 1.43 (m, 4H), 0.95 (s, 18H), 0.93
3
(s, 18H); 13C{1H} NMR (100.6 MHz, CDCl3):
δ
153.4 (d, JPC=4.0 Hz, quaternary
C
–
3
O), 153.0 (d, JPC=4.0 Hz, quaternary
C–O), 145.1, 145.0, 137.0, 133.9, 133.8, 133.5, 132.7,
1
3
2
132.5, 132.4 (d, JPC=95.8 Hz, quaternary Ar), 131.5
(
d, JPC=11.2 Hz, Ar), 131.4
(
d, JPC=9.1
4
3
2
Hz, Ar), 131.3
(
d, JPC=5.3 Hz, Ar
), 128.7
(
d, JPC=10.8 Hz, Ar), 128.6
(
d, JPC=7.4 Hz, Ar),
4
1
128.5
(
d, JPC=5.4 Hz, Ar
)
, 125.0, 124.9, 121.9, 71.7 (d, JPC=77.1 Hz, –
C
H2P(O)Ph2), 71.4 (d,
1JPC=77.1 Hz, –
27.3; 31P{1H} NMR (161.9 MHz, CDCl3):
C
H2P(O)Ph2), 45.6, 36.9, 34.9, 34.0, 33.9, 33.1, 33.0, 32.3, 31.6, 31.5, 30.1, 28.7,
26.9, 26.1; IR (cm–1): 2986 (m), 2868 (m), 1592
δ
(m), 1479 (m), 1362 (w), 1197 (m, P=O), 1120 (m), 1104 (w); ESI-HRMS calcd:
C102H112ClO8P4 [M+H]+: 1623.6996, found: 1623.6973.
4.5. General procedure for the synthesis of 2-(ω-iodoalkyl)-tetra-(pivaloylmethyl)-p-tert-
butylcalix[4]arenes (8a and 8b)
Compounds 8a and 8b were synthesized in a similar manner to that described for 7.30
A
suspension of 4a or 4b and potassium carbonate (12 equivalents) in dry acetone was refluxed for
6 h under nitrogen. To this suspension, 1-bromopinacolone (6 equivalents) along with potassium
iodide (6 equivalents) was added and refluxed for 6 days. The reaction mixture was poured into
ice water and extracted with CH2Cl2. This CH2Cl2 layer was washed with 3% H2SO4 (50 ml)
solution followed by two portions of water (40 ml). The CH2Cl2 layer was dried over MgSO4,
filtered, and concentrated using a rotavap to yield a yellow-colored crude solid. This solid was
then crystallized from cold ethanol in a freezer overnight. The resulting solid was washed with
cold ethanol to yield a fine off-white crystalline solid.
20

ACCEPTED MANUSCRIPT
4.5.1 2-(5-Iodopentyl)-tetra-(pivaloylmethyl)-p-tert-butylcalix[4]arene (8a)
Reagents: 4a (5.0 g, 6.7 mmol); K2CO3 (11.0 g, 79.6 mmol); 1-bromopinacolone (3.6 ml, 27
1
mmol); KI (4.5 g, 27 mmol); acetone (120 mL). Yield: 1.9 g (24%); mp 218–224 °C; H NMR
3
2
(399.9 MHz, CDCl3): δ 6.99–6.54 (m, 8H), 5.38 (t, 1H, JHH=6.6 Hz), 5.24 (d, 2H, JHH=13.0
2
2
2
Hz), 5.21 (d, 2H, JHH=13.0 Hz), 5.18 (d, 2H, JHH=13.2 Hz), 5.15 (d, 2H, JHH=13.2 Hz), 4.95
2
2
2
(d, 2H, JHH=12.4 Hz), 4.89 (d, 1H, JHH=13.0 Hz), 3.17 (d, 2H, JHH=12.4 Hz), 3.16 (t, 2H,
3
3
3JHH=7.2 Hz), 3.15 (d, 1H, 2JHH=13.0 Hz), 1.96 (q, 2H, JHH=6.6 Hz), 1.82 (quint, 2H, JHH=6.6
Hz), 1.47 (m, 4H), 1.21 (s, 18H), 1.18 (s, 18H), 1.07 (s, 18H), 1.06 (s, 18H); 13C{1H} NMR
(100.6 MHz, CDCl3):
δ 211.7, 211.2, 153.7, 153.2, 144.7, 144.6, 136.7, 133.9, 133.8, 133.7,
125.4, 125.3, 124.9, 122.0, 75.2, 74.7, 42.8, 36.1, 34.7, 34.1, 34.0, 33.9, 33.7, 32.2, 32.1, 31.7,
31.6, 31.3, 27.4, 26.7, 26.6, 26.5; IR (cm–1): 2986 (m), 1720 (m, C=O), 1602 (m), 1480 (m),
1368 (m), 1123 (w), 1046 (w), 991 (w); ESI-HRMS calcd: C73H105INaO8 [M+Na]+: 1259.6752,
found: 1259.6743.
4.5.2 2-(6-Iodohexyl)-tetra-(pivaloylmethyl)-p-tert-butylcalix[4]arene (8b)
Reagents: 4b (7.7 g, 10 mmol); K2CO3 (16.6 g, 120 mmol); 1-bromopinacolone (5.5 ml, 41
1
mmol); KI (6.8 g, 41 mmol); acetone (160 mL). Yield: 3.0 g (24%); mp 219–227 °C; H NMR
3
2
(399.9 MHz, CDCl3): δ 7.01–6.55 (m, 8H), 5.36 (t, 1H, JHH=6.8 Hz), 5.26 (d, 2H, JHH=13.2
2
2
2
Hz), 5.24 (d, 2H, JHH=13.2 Hz), 5.22 (d, 2H, JHH=12.8 Hz), 5.21 (d, 2H, JHH=12.8 Hz), 4.97
2
2
2
(d, 2H, JHH=12.0 Hz), 4.91 (d, 1H, JHH=12.0 Hz), 3.18 (d, 2H, JHH=12.0 Hz), 3.17 (t, 2H,
3
3
3JHH=7.2 Hz), 3.17 (d, 1H, 2JHH=12.0 Hz), 1.97 (q, 2H, JHH=6.8 Hz), 1.81 (quint, 2H, JHH=6.8
Hz), 1.41 (m, 6H), 1.23 (s, 18H), 1.20 (s, 18H), 1.08 (s, 18H), 1.07 (s, 18H); 13C{1H} NMR
(100.6 MHz, CDCl3): 211.7, 211.2, 153.7, 153.2, 144.6, 144.5, 136.7, 133.8, 133.7,
21

ACCEPTED MANUSCRIPT
133.6 (quaternary aromatic carbons), 125.4, 125.3, 124.9, 122.0, 75.2, 74.7, 42.9, 36.2, 34.9,
34.2, 34.0, 33.7, 33.6, 32.2, 32.1, 31.7, 31.6, 30.8, 29.3, 28.4, 26.7, 26.6, 26.5; IR (cm–1): 2967
(m), 2686 (m), 1721 (m, C=O), 1600 (m), 1479 (m), 1364 (m), 1123 (w), 1044 (w), 989 (w);
ESI-HRMS calcd: C74H107INaO8 [M+Na]+: 1273.6908, found: 1273.6896.
4.6. Liquid-liquid extraction of lanthanide nitrates
Simple LLE (Eq. 1) was performed with the aqueous phase comprised of lanthanide nitrate (10–4
M) in HNO3 (1 M) and the organic phase composed of calix[4]arene ligands 5,20 6a, 6b, 7, 8a or
8b in dichloromethane (2.5×10–2 M). A one milliliter aliquot of each phase was stirred in a
stoppered vial at RT for 12 h. The two phases were allowed to separate over 2 h.
(1)
UV–vis spectrophotometry with the Arsenazo III indicator was used to determine the percentage
extraction (%
E
), with absorbance measured at 655 nm.20,37 With the much higher concentration
of Arsenazo III than that of the metal ion, we assume complete complexation. The extraction
percentages (%E) were calculated using the formula:
ꢃ
ꢁ
ꢄ
ꢅꢄ
ꢂ − ꢂ
%ꢀ = 100 ×
ꢁ
(2)
ꢃ
ꢂ − ꢂ
where A0 is the absorbance of Arsenazo III solution without cation, A1 is the concentration of
Arsenazo III solution with a known concentration of cation before extraction, and
22
A is the

ACCEPTED MANUSCRIPT
concentration remaining after extraction.37,40 The ratio of concentration of metal ion in organic
phase to concentration of metal ion in aqueous phase gives the distribution ratio (D), represented
in Eq. (3).
D
characterizes the extractability of these ligands. If %
E
is stated as Eq. (4),
distribution coefficients (
D) can be calculated as shown in Eq. (5):
ꢁꢇꢄꢈꢉꢊ
ꢆ =
(3)
(4)
(5)
ꢁꢇꢄꢋꢌ
ꢁꢇꢄꢈꢉꢊ
ꢁꢇꢄꢈꢉꢊ + ꢁꢇꢄꢋꢌ
ꢆ
%ꢀ = 100 ×
= 100 ×
1 + ꢆ
%ꢀ
ꢆ =
ꢁ
ꢄ
100 − %ꢀ
23

ACCEPTED MANUSCRIPT
Table 1. Summary of new ligands.
Compound
L
X
Isolated yield (%) m.p. (°C)
H
H
–(CH2)5Cl
–(CH2)6Cl
–(CH2)5Cl
–(CH2)6Cl
91
84
31
24
23
24
214–218
219–221
>250
>250
218–224
219–227
4a
4b
6a
6b
8a
8b
–P(O)Ph2
–P(O)Ph2
–C(O)C(CH3)3 –(CH2)5I
–C(O)C(CH3)3 –(CH2)6I
Table 2. Distribution coefficients (
D) for the extraction of lanthanides by phosphine oxide-
calix[4]arenesa from an aqueous phase (CLn=1×10–4 M, 1 M HNO3).
Ligand La3+
Ce3+
0.17
Pr3+
0.46
Nd3+
0.18
Sm3+
0.46
Eu3+
2.09
Gd3+
0.35
Dy3+
0.23
Yb3+
0.22
0.40
5
(4.00)b
1.26
0.20
0.16
0.15
0.13
0.21
0.17
0.15
0.13
0.36
0.32
0.27
0.27
0.20
0.18
0.16
0.12
6a
6b
0.96
aFor all phosphine oxide-calix[4]arenes, (CL=2.5×10–2 M) in dichloromethane.
bRef. 20.
25

ACCEPTED MANUSCRIPT
References
(1)
Weber, R. J.; Reisman, D. J. Rare Earth Elements: A Review of Production,
Processing, Recycling, and Associated Environmental Issues; US EPA, 2012.
(2)
(3)
Bünzli, J.-C. G. Acc. Chem. Res 2006, 39, 53-61.
Goonan, T. G. Rare Earth Elements--End Use and Recyclability; US Department
of the Interior, US Geological Survey, 2011.
(4)
(5)
(6)
(7)
(8)
Jacoby, M.; Jiang, J. Chem. Eng. News 2010, 88, 9-12.
Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Elsevier, 2012.
Bruno, J.; Ewing, R. C. Elements 2006, , 343-349.
Dam, H. H.; Reinhoudt, D. N.; Verboom, W. Chem. Soc. Rev. 2007, 36, 367-377.
Yaftian, M.; Burgard, M.; Matt, D.; Dieleman, C.; Rastegar, F. Solvent Extr. Ion
2
Exch. 1997, 15, 975-989.
(9)
Tkac, P.; Vandegrift, G. F.; Lumetta, G. J.; Gelis, A. V. Ind. Eng. Chem. Res.
2012, 51, 10433-10444.
(10) Ohto, K.; Yano, M.; Inoue, K.; Nagasaki, T.; Goto, M.; Nakashio, F.; Shinkai, S.
Polyhedron 1997, 16, 1655-1661.
(11) Koma, Y.; Watanabe, M.; Nemoto, S.; Tanaka, Y. J. Nucl. Sci. Technol. 1998, 35
,
130-136.
(12) de María Ramírez, F.; Tosheva, T.; Tashev, E.; García-Villafaña, E.; Shenkov, S.;
Varbanov, S. Polyhedron 2013, 56, 123-133.
(13) Harrowfield, J. M.; Mocerino, M.; Peachey, B. J.; Skelton, B. W.; White, A. H. J.
Chem. Soc., Dalton Trans. 1996, 1687-1699.
(14) Barboso, S.; Carrera, A. G.; Matthews, S. E.; Arnaud-Neu, F.; Böhmer, V.;
Dozol, J.-F.; Rouquette, H.; Schwing-Weill, M.-J. J. Chem. Soc., Perkin Trans. 2 1999, 719-724.
(15) Ludwig, R. Fresenius' J. Anal. Chem. 2000, 367, 103-128.
(16) Gutsche, C. D. Calixarenes: an introduction; Royal Society of Chemistry, 2008.
(17) Böhmer, V. Angew. Chem. Int. Ed. 1995, 34, 713-745.
(18) Creaven, B. S.; Donlon, D. F.; McGinley, J. Coord. Chem. Rev. 2009, 253, 893-
962.
(19) Beer, P. D.; Drew, M. G.; Grieve, A.; Kan, M.; Leeson, P. B.; Nicholson, G.;
Ogden, M. I.; Williams, G. Chem. Commun. 1996, 1117-1118.
(20) Arnaud-Neu, F.; Browne, J.; Byrne, D.; Marrs, D.; McKervey, M.; O'Hagan, P.;
Schwing-Weill, M.; Walker, A. Chem. Eur. J. 1999, 5, 175-186.
(21) Beer, P. D.; Brindley, G. D.; Fox, O. D.; Grieve, A.; Ogden, M. I.; Szemes, F.;
Drew, M. G. J. Chem. Soc., Dalton Trans. 2002, 3101-3111.
(22) Jeunesse, C.; Dieleman, C.; Steyer, S.; Matt, D. J. Chem. Soc., Dalton Trans.
2001, 881-892.
(23) Jeunesse, C.; Armspach, D.; Matt, D. Chem. Commun. 2005, 5603-5614.
(24) Böhmer, V.; Dozol, J.-F.; Grüttner, C.; Liger, K.; Matthews, S. E.; Rudershausen,
S.; Saadioui, M.; Wang, P. Org. Biomol. Chem. 2004,
(25) Jain, V.; Pandya, R.; Pillai, S.; Agrawal, Y.; Kanaiya, P. J. Anal. Chem. 2007, 62
104-112.
(26) Hamid, S. A.; Tarmizi, A. A. A.; Ali, M.; Salhin, A.; Saad, B. Clean 2008, 36
498-503.
(27) Scully, P. A.; Hamilton, T. M.; Bennett, J. L. Org. Lett. 2001,
2, 2327-2334.
,
,
3, 2741-2744.
26

ACCEPTED MANUSCRIPT
(28) Hertel, M. P.; Behrle, A. C.; Williams, S. A.; Schmidt, J. A.; Fantini, J. L.
Tetrahedron 2009, 65, 8657-8667.
(29) Dieleman, C.; Loeber, C.; Matt, D.; De Cian, A.; Fischer, J. J. Chem. Soc., Dalton
Trans 1995, 3097-3100.
(30) Arnaud-Neu, F.; Collins, E. M.; Deasy, M.; Ferguson, G.; Harris, S. J.; Kaitner,
B.; Lough, A. J.; McKervey, M. A.; Marques, E. J. Am. Chem. Soc. 1989, 111, 8681-8691.
(31) de María Ramírez, F.; Varbanov, S.; Bünzli, J.-C. G.; Scopelliti, R. Inorg. Chim.
Acta 2011, 378, 163-168.
(32) Nash, K. L. Solvent Extr. Ion Exch. 1993, 11, 729-768.
(33) Ionova, G.; Ionov, S.; Rabbe, C.; Hill, C.; Madic, C.; Guillaumont, R.; Krupa, J.
Solvent Extr. Ion Exch. 2001, 19, 391-414.
(34) Gutsche, C. D.; Iqbal, M.; Stewart, D. J. Org. Chem 1986, 51, 742-745.
(35) Silveira, C. C.; Rinaldi, F.; Guadagnin, R. C. Eur. J. Org. Chem. 2007, 2007
4935-4939.
(36) Savvin, S. Talanta 1961,
,
8, 673-685.
(37) Vatsouro, I.; Serebryannikova, A.; Wang, L.; Hubscher-Bruder, V.; Shokova, E.;
Bolte, M.; Arnaud-Neu, F.; Böhmer, V.; Kovalev, V. Tetrahedron 2011, 67, 8092-8101.
(38) McOmie, J. F.; Watts, M.; West, D. E. Tetrahedron 1968, 24, 2289-2292.
(39) Hardman, M. J.; Thomas, A. M.; Carroll, L. T.; Williams, L. C.; Parkin, S.;
Fantini, J. L. Tetrahedron 2011, 67, 7027-7034.
(40) Chu, H.; He, L.; Jiang, Q.; Fang, Y.; Jia, Y.; Yuan, X.; Zou, S.; Li, X.; Feng, W.;
Yang, Y. J. Hazard. Mater. 2014, 264, 211-218.
27

ACCEPTED MANUSCRIPT
TOC Synopsis:
New 2-substituted haloalkyl tetraphosphorylated and tetraketone calix[4]arenes were synthesized
and used to understand the effect on extraction of lanthanide ions in comparison to known
literature. With distinct selectivity for europium and differential affinity for metals across the
lanthanide series, these new ligands should prove to be useful precursors for the development of
solid phase extraction materials.
28

ACCEPTED MANUSCRIPT
TOC Graphical abstract
Captions
Scheme 1. Synthesis of 2-(ω-chloroalkyl)-tetramethoxy-
Scheme 2. Synthesis of 2-(ω-chloroalkyl)-tetrahydroxy-
p
-tert-butylcalix[4]arenes. 28
p
-tert-butylcalix[4]arenes.
Scheme 3. Synthesis of 2-(ω-chloroalkyl)-tetra-(diphenylphosphonylmethyl)-p-tert-
butylcalix[4]arenes.
Scheme 4. Synthesis of 2-(ω-iodoalkyl)-tetra-(pivaloylmethyl)-p-tert-butylcalix[4]arenes.
Figure 1. Calix[4]arene: (i) flat line drawing with numbering, (ii) three dimensional perspective,
and (iii) similarity to a basket.
Figure 2. Percent extraction (%E) for the lanthanide ions with ligands 5, 6a and 6b;
concentration of ligand (CL=2.5×10–2 M) in dichloromethane, concentration of lanthanide
nitrates (CLn=1×10–4 M) in 1 M HNO3.
Table 1. Summary of new ligands.
Table 2. Distribution coefficients (D) for the extraction of lanthanides by phosphine oxide-
calix[4]arenesa from an aqueous phase (CLn=1×10–4 M, 1 M HNO3).
29