trans-N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine and its thioxanthenyl derivative as potential host compounds for the separation of anilines through host?guest chemistry principles

Article abstract of DOI:10.1007/s10847-020-01002-0

In this work, we investigate the potential of separating mixtures of the guest solvents aniline (ANI), N-methylaniline (NMA) and N,N-dimethylaniline (DMA) by means of host?guest chemistry principles employing two novel host compounds, namely trans-N,N′-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX) and trans-N,N′-bis(9-phenyl-9-thioxanthenyl)cyclohexane-1,2-diamine (1,2-DAT). These aniline solvents may exist in such mixtures since NMA and DMA are often prepared from ANI by alkylation methods, and reaction yields are seldom quantitative. Owing to their similar boiling points, ranging from 184 to 196 oC, the more usual distillation techniques for their separation are challenging. After recrystallization experiments of the two host compounds from various combinations of these anilines, it was revealed that host?guest chemistry certainly has the potential to serve as an alternative separation strategy for such mixtures. Equimolar ANI/DMA solutions proved most successful, where both 1,2-DAX and 1,2-DAT showed near-quantitative selectivity for DMA (90%). Both single crystal diffraction and thermal analyses were employed in order to understand the preferential behaviour displayed by each host compound.

Full text of DOI:10.1007/s10847-020-01002-0

Journal of Inclusion Phenomena and Macrocyclic Chemistry
https://doi.org/10.1007/s10847-020-01002-0
ORIGINAL ARTICLE
trans-N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine
and its thioxanthenyl derivative as potential host compounds
for the separation of anilines through host‒guest chemistry principles
Benita Barton1 · Daniel V. Jooste1 · Eric C. Hosten1
Received: 13 February 2020 / Accepted: 27 May 2020
© Springer Nature B.V. 2020
Abstract
In this work, we investigate the potential of separating mixtures of the guest solvents aniline (ANI), N-methylaniline (NMA)
and N,N-dimethylaniline (DMA) by means of host‒guest chemistry principles employing two novel host compounds, namely
trans-N,N′-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX) and trans-N,N′-bis(9-phenyl-9-thioxanthenyl)
cyclohexane-1,2-diamine (1,2-DAT). These aniline solvents may exist in such mixtures since NMA and DMA are often
prepared from ANI by alkylation methods, and reaction yields are seldom quantitative. Owing to their similar boiling points,
ranging from 184 to 196 ºC, the more usual distillation techniques for their separation are challenging. After recrystalliza-
tion experiments of the two host compounds from various combinations of these anilines, it was revealed that host‒guest
chemistry certainly has the potential to serve as an alternative separation strategy for such mixtures. Equimolar ANI/DMA
solutions proved most successful, where both 1,2-DAX and 1,2-DAT showed near-quantitative selectivity for DMA (90%).
Both single crystal difraction and thermal analyses were employed in order to understand the preferential behaviour dis-
played by each host compound.
Keywords Host‒guest · Xanthenyl · Inclusion · Selectivity · Separation · Aniline
Introduction
N,N-dimethylaniline (DMA) serves as an intermediate in the
manufacture of dyes such as Crystal Violet [2, 3]. NMA is
typically synthesized through the methylation of ANI with
methanol, but this process is prone to selectivity concerns
since the product (NMA) is more reactive than ANI, result-
ing in the formation of DMA due to overalkylation. Further-
more, upon heating, NMA and DMA undergo rearrange-
ment to form unwanted p- and o-toluidine [4]. More recently,
vapour phase methylation of aniline using Sn-MFI molecular
sieves (tin silicalite-1) has been successful as an alternative
aniline alkylation strategy; the molar ratio of SiO2 and SnO2
may be varied. Using this process, the aniline conversion is
usually increased which, in turn, leads to either an increase
or reduction in the production of NMA and DMA, depend-
ent on this SiO2/SnO2 ratio [5].
Industrially, aniline (ANI) is a valuable chemical that has
applications in over 300 diferent products, with one of the
more important of these being in the production of methyl-
ene diphenyl diisocyanate (MDI) [1]. MDI exists in three
isomeric forms, with the 4,4′-isomer being the most valu-
able: reaction with alcohols produces the commercially-
important rigid polyurethane. ANI is additionally employed
as an intermediate in the manufacture of dyes and pigments,
as well as antidegradants in rubber processing. N-Methy-
laniline (NMA) is used as an antiknock agent to adjust
the octane number in the production of many fuels, while
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10847-020-01002-0) contains
supplementary material, which is available to authorized users.
The separation of these aniline compounds (ANI, NMA
and DMA) when they are found in mixtures, as would be the
case when ANI is alkylated, is challenging owing to simi-
larities in their boiling points (184.1, 196.2 and 193.5 °C,
respectively), and methods other than fractional distillation
are therefore appealing. An alternative separation strategy
that may be considered to achieve this goal is host‒guest
* Benita Barton
benita.barton@mandela.ac.za
1
Department of Chemistry, Nelson Mandela University,
6031 Port Elizabeth, South Africa
Vol.:(0123456789)
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Journal of Inclusion Phenomena and Macrocyclic Chemistry
chemistry. This feld of science utilizes crystalline host com-
pounds (typically the larger of the involved molecular spe-
cies) to encapsulate the guest (the smaller species) through
non-covalent interactions between the host and guest [6–8].
These interactions are more usually π···π, XH···π and hydro-
gen bonding in nature, dependent on the characteristics of
the two interacting species, though many other interaction
types have been noted in the literature. Naturally, in order
to facilitate separation in this context, the host compound
is required to display preferential behaviour towards only
one guest component in the presence of such mixtures.
Host–guest chemistry presents an attractive alternative
protocol for the separation of such compounds, especially
since the host compounds are readily recycled in the process
after removal of the enclathrated guest components through
distillation.
Guests in mixtures, however, need not necessarily be
related as isomers in order for the host to behave discrimi-
natorily. As illustrations, our group has reported on the
clear selectivity of various host materials when presented
with aromatic/aliphatic [12] or ketone/alcohol/amine [13]
combinations.
In this work, we report on the selectivity behaviour
of two novel host compounds, trans-N,N′-bis(9-phenyl-
9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX) and
trans-N,N′-bis(9-phenyl-9-thioxanthenyl)cyclohexane-
1,2-diamine (1,2-DAT), when these were recrystallized
from various mixtures of ANI, NMA and DMA, in order
to ascertain whether separations of these guest compounds
are feasible by means of host‒guest chemistry principles
(Scheme 1). NMR spectroscopy, single crystal X-ray dif-
fraction (SCXRD) and thermal analyses (TA) were selected
as the analytical methods of choice with which to analyse
any complexes formed in this work, as appropriate. Note that
ANI/NMA/DMA guest combinations have been considered
by our group previously, employing alternative known host
compounds, namely (−)-(2R,3R)-2,3-dimethoxy-1,1,4,4-
tetraphenylbutane-1,4-diol (DMT) [14], (+)-(2R,3R)-
1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) [15],
N,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine and N,N′-
bis(9-phenyl-9-thioxanthenyl)ethylenediamine [16]. In this
way, both DMT and TETROL were revealed to possess poor
selectivity in these conditions, while the two ethylenedi-
amine derivatives were observed to be more capable.
Many investigations have been carried out that employ
this method of separation. As examples, Nassimbeni et al.
assessed the potential of three diol host compounds to efect
the separation of various lutidine isomers with much suc-
cess[9], while Caira and co-workers considered xylenol iso-
mer separations using a cyclohexane host derivative [10].
Furthermore, Ni(NCS)2(para-phenylpyridine)4, a Werner
complex, was shown by Barbour and Lusi [11] to be selec-
tive for ortho-xylene when present in a vaporous mixture of
the three xylenes.
Scheme 1 Molecular structures
of host compounds 1,2-DAX
and 1,2-DAT, as well as guests
ANI, NMA and DMA
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Experimental
189770) software was used to analyse the crystal struc-
tures [21]. Thermogravimetric (TG) and diferential scan-
ning calorimetry (DSC) traces were obtained using a Per-
kin Elmer STA6000 Simultaneous Thermal Analyser and
analysed using Perkin Elmer Pyris 13 Thermal Analysis
software. An empty ceramic pan was used as a reference,
and the same open pan was subsequently employed for the
sample run. High purity nitrogen was the purge gas, and
all samples were heated from approximately 30 to 300 °C
General methods
All chemicals and solvents were purchased through
1
Merck and used as received. H- and 13C-NMR spectra
were obtained by means of a 400 MHz Bruker Avance
Ultrashield Plus 400 Spectrometer (CDCl3 was the deuter-
ated solvent). Melting points were carried out on a Stu-
art SMP10 digital melting point apparatus and these are
uncorrected. Infrared analyses were conducted on a Bruker
Tensor 27 Fourier Transform Infrared spectrometer, and
data analysed by means of OPUS data analysis software.
Gas chromatography (GC) was performed by means of
an Agilent Technologies 7890 A gas chromatograph sys-
tem ftted to an Agilent Technologies 5975 C VL MSD
mass spectrometer (MS) with a Triple Axis Detector, or a
YoungLin 6500 GC system with FID as detector, and data
were analysed using Agilent MSD Productivity Chem-
Station E.02.01.1177 and Delta 5.5 acquisition software,
respectively. High purity helium was the carrier gas. An
Agilent J&W GC DB-1MS column with a length of 30
m, a diameter of 0.25 mm and a flm thickness of 0.25
µm was applicable. This method involved heating the
oven to 50 °C, with zero hold time, and then initiating an
immediate ramp of 15 °C min− 1 to 200 °C, and culminat-
ing with a hold time of 1 min. The split ratio was 20:1
and inlet temperature 250 °C. Single crystal X-ray dif-
fraction (SCXRD) experiments were performed at 200 K
(for 1,2-DAX·ANI, 1,2-DAX·DMA and 1,2-DAT·DMA)
or 296 K [1,2-DAT·2(ANI), 1,2-DAT·2(NMA)] using a
Bruker Kappa Apex II difractometer with graphite-mon-
ochromated Mo Kα radiation (λ = 0.71073 Å). APEXII
[17] was used for data collection and SAINT [17] for cell
refnement and data reduction. The structures were solved
using SHELXT-2018/2 [18] and refned by least-squares
procedures using SHELXL-2018/3 [19] with SHELXLE
[20] as a graphical interface. All non-hydrogen atoms were
refned anisotropically, and the carbon-bound hydrogen
atoms were added in idealized geometrical positions in a
riding model. The nitrogen-bound H atoms were located
on a diference Fourier map and refned freely, where pos-
sible, or otherwise in calculated positions. Data were cor-
rected for absorption efects using the numerical method
implemented in SADABS [17]. Crystallographic data
for these novel complexes were deposited at the Cam-
bridge Crystallographic Data Centre {{CCDC-1982613
(1,2-DAX·ANI), 1982614 (1,2-DAX·DMA), 1982615
[1,2-DAT·2(ANI)], 1982616 [1,2-DAT·2(NMA)] and
1982617 (1,2-DAT·DMA)}}. Mercury CSD 3.10.2 (Build
at a heating rate of 10 °C min− 1
.
Synthesis of host compounds 1,2‑DAX and 1,2‑DAT
1,2-DAX and 1,2-DAT were synthesized according to
known procedures [22] in three distinct steps (Scheme 2):
trans-N,N′-Bis(9-phenyl-9-xanthenyl)
cyclohexane-1,2-diamine (Scheme 2, X = O)
9-Phenylxanthen-9-ol This compound was prepared
according to a general Grignard addition procedure. Mag-
nesium turnings (2.4318 g, 0.1001 mol), bromobenzene
(15.3602 g, 0.0978 mol) and xanthone (16.0083 g, 0.0816
mol) in anhydrous THF yielded a gum which was crystal-
lized and recrystallized from CH2Cl/petroleum ether to
aford 9-phenylxanthen-9-ol (13.8731 g, 62%) as a white
solid, mp 158–162 °C (lit.,[22] mp 159 °C); vmax (solid)/
cm−1 3548 (OH) and 1600 (Ar C=C); δH(CDCl3)/ppm
2.71 (1H, s, OH), 7.09 (2H, t, ArH), 7.23 (3H, d, ArH) and
7.30–7.45 (8H, m, ArH); δC(CDCl3)/ppm 70.46 (PhCOH),
116.43 (ArC), 123.58 (ArC), 126.25 (ArC), 126.77 (ArC),
127.22 (quaternary ArC), 128.00 (ArC), 129.05 (ArC),
148.00 (quaternary ArC) and 149.71 (quaternary ArC).
9-Phenylxanthen-9-ylium perchlorate Perchloric
acid
(6.8952 g, 0.0686 mol) was added dropwise to a chilled,
stirred solution of 9-phenylxanthen-9-ol (12.0199 g, 0.0439
mol) in a mixture of dichloromethane (250 mL) and diethyl
ether (250 mL). Stirring was continued for 10 min before
the resulting yellow precipitate was collected using vacuum
fltration and washed with diethyl ether to yield 9-phenylx-
anthen-9-ylium perchlorate (13.7007 g, 0.0384 mol, 87%)
as a yellow solid, mp 285–287 °C (lit.,[22] mp 283–286 °C);
vmax (solid)/cm−1 1597 (Ar C=C); δH(CDCl3)/ppm 7.79–
7.82 (5H, m, ArH), 7.94 (2H, t, ArH), 8.19 (2H, d, ArH),
8.43 (2H, d, ArH) and 8.52 (2H, t, ArH).
trans‑N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-di-
amine (1,2-DAX) 9-Phenylxanthen-9-ylium perchlorate
(7.9050 g, 0.0222 mol), in CH2Cl2 (250 mL), was added
to trans-1,2-cyclohexanediamine (1.2651 g, 0.0111 mol),
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Scheme 2 Synthetic strategy
X
X
O
towards 1,2-DAX and 1,2-DAT
1) PhMgBr
2) H
OH
Xanthone (X = O)
Thioxanthone (X = S)
9-Phenylxanthen-9-ol (X = O)
9-Phenylthioxanthen-9-ol (X = S)
HClO4
X
H2N
NH2
1,2-DAX (X = O)
1,2-DAT (X = S)
ClO4
9-Phenylxanthen-9-ylium perchlorate (X = O)
9-Phenylthioxanthen-9-ylium perchlorate (X = S)
also in CH2Cl2 (30 mL). The reaction mixture was stirred
at room temperature for 30 min whereafter triethylamine (5
mL, 3.630 g, 0.0359 mol) was added, resulting in a colour
change from orange to colourless. Following an additional
30 min of stirring, the solution was washed with water and
the organic layer dried over anhydrous Na2SO4. The solvent
was removed under reduced pressure and the residue crys-
tallized and recrystallized from ethanol/CH2Cl2 to aford
trans-N,N′-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-di-
amine (1,2-DAX) (6.1411 g, 9.798 mmol, 88%) as a white
solid, mp 227–230 °C; vmax (solid)/cm−1 3271 (NH), 3070
(ArCH), 3028 (ArCH), 2920 (alkyl CH), 2856 (alkyl CH)
and 1601 (Ar C=C); δH(CDCl3)/ppm 0.26–0.53 (2H, m,
cyclohexyl H), 0.54–0.79 (4H, m, cyclohexyl H), 1.01–1.21
(2H, m, cyclohexyl H), 1.92–2.09 (2H, m, NHCH), 2.18
(2H, br s, NH) and 6.88–7.37 (26H, m, ArH); δC(CDCl3)/
ppm 25.02 (CH2), 33.91 (CH2), 57.36 (NHCH), 59.76 (qua-
ternary CNH), 115.90 (ArC), 116.10 (ArC), 122.84 (ArC),
123.30 (ArC), 126.29 (ArC), 127.59 (ArC), 128.00 (ArC),
128.18 (ArC), 130.73 (ArC), 130.84 (ArC), 150.45 (qua-
ternary ArC), 150.78 (quaternary ArC) and 151.72 (qua-
ternary ArC). After recrystallization from o-xylene, a 1:1
complex was obtained. [Found: C, 85.44; H, 6.82; N, 3.72.
C44H38N2O2·C8H10 (1:1) requires C, 85.27; H, 6.61; N,
3.82%.]
trans-N,N′-Bis(9-phenyl-9-thioxanthenyl)
cyclohexane-1,2-diamine 1 (Scheme 2, X = S)
9-Phenylthioxanthen-9-ol This compound was also pre-
pared by means of a general Grignard addition procedure.
Magnesium turnings (2.7332 g, 0.1125 mol), bromoben-
zene (16.6532 g, 0.1061 mol) and thioxanthone (10.0113 g,
0.0472 mol) in anhydrous THF yielded a gum-like residue
which was crystallized and recrystallized from benzene/
petroleum ether to aford 9-phenylthioxanthen-9-ol (8.5690
g, 63%) as a mustard yellow solid, mp 103–106 °C (lit.,[22]
mp 105–106 °C); vmax (solid)/cm−1 3297 (OH) and 1589 (Ar
C=C); δH(CDCl3)/ppm 2.85 (1H, s, OH), 6.96–7.07 (2H,
m, ArH), 7.15–7.25 (3H, m, ArH), 7.28–7.47 (6H, m, ArH)
and 8.06 (2H, d, ArH); δC(CDCl3)/ppm 77.02 (PhCOH),
126.13 (ArC), 126.52 (ArC), 126.69 (ArC), 126.97 (ArC),
127.34 (ArC), 127.80 (ArC), 128.09 (ArC), 131.64 (quater-
nary ArC), 140.01 (quaternary ArC) and 143.41 (quaternary
ArC).
9-Phenylthioxanthen-9-ylium
perchlorate Perchloric
acid (14.1440 g, 0.1408 mol) was added dropwise to a
chilled, stirred solution of 9-phenylthioxanthen-9-ol
(6.0066 g, 0.0207 mol) in a mixture of CH2Cl2 (50 mL)
and diethyl ether (50 mL). Following an additional 5 min
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
of stirring, the resulting intense red precipitate was col-
lected using vacuum fltration and washed with diethyl
ether to yield 9-phenylthioxanthen-9-ylium perchlorate
(6.2753 g, 0.0168 mol, 81%) as a red solid, mp 238–
240 °C (decomp.) [lit.,[22] mp 239 °C (decomp.)]; vmax
(solid)/cm− 1 1591 (Ar C = C); δH(CDCl3)/ppm 7.59–7.61
(2H, m, ArH), 7.77–7.79 (3H, m, ArH), 8.01 (2H, t,
ArH), 8.27 (2H, d, ArH), 8.35 (2H, t, ArH) and 8.84 (2H,
d, ArH).
encourage the process. Resultant solids were collected by
vacuum fltration, washed with petroleum ether to remove
any guest solvent adhering to the crystal surfaces, and dried
under vacuum fltration. The dried crystals were analysed by
means of 1H-NMR spectroscopy (CDCl3 was the deuterated
solvent) to establish whether inclusion of the guest by the
host species had taken place and, if so, the overall host:guest
(H:G) ratio through integration of relevant host and guest
resonance signals on this spectrum.
trans-N,N′-Bis(9-phenyl-9-thioxanthenyl)cyclohex-
Mixed guest solvent experiments
ane-1,2-diamine
(1,2-DAT) 9-Phenylthioxanthen-
9-ylium perchlorate (3.0135 g, 0.0081 mol), in CH2Cl2,
was added to a solution of trans-1,2-cyclohexanediamine
(0.4685 g, 0.0041 mol), also in CH2Cl2 (30 mL), and the
solution stirred for 30 min. A portion of triethylamine
(4.4 mL, 3.194 g, 0.0316 mol) was then added which
resulted in a colour change of the solution from deep red
to orange. Stirring at room temperature was continued for
30 min before the solution was washed with water and the
organic layer dried over anhydrous Na2SO4. The solvent
was removed under reduced pressure, yielding an orange
gum which was crystallized and recrystallized from etha-
nol/CH2Cl2 to aford trans-N,N′-bis(9-phenyl-9 thiox-
anthenyl)cyclohexane-1,2-diamine (1,2-DAT) (1.4138
g, 2.146 mmol, 52%) as a cream solid, mp 175–181 °C;
vmax (solid)/cm− 1 3269 (NH), 3054 (ArCH), 2913 (alkyl
CH), 2848 (alkyl CH) and 1588 (Ar C = C); δH(CDCl3)/
ppm 0.37–0.59 (2H, m, cyclohexyl H), 0.62–0.98 (4H,
m, cyclohexyl H), 1.03–1.29 (2H, m, cyclohexyl H),
1.99–1.21 (2H, m, NHCH), 2.36 (2H, br s, NH) and
6.74–7.39 (26H, m, ArH); δC(CDCl3)/ppm 25.32 (CH2),
34.08 (CH2), 58.10 (NHCH), 65.29 (quaternary CNH),
124.76 (ArC), 124.91 (ArC), 125.38 (ArC), 125.81
(ArC), 126.25 (ArC), 126.62 (ArC), 126.66 (ArC),
127.40 (ArC), 128.724 (ArC), 132.13 (ArC), 132.22
(ArC), 138.54 (quaternary ArC) 138.80 (quaternary ArC)
and 150.43 (quaternary ArC). After recrystallization
from p-xylene, a 1:1 complex was obtained. [Found: C,
81.88; H, 6.82; N, 3.38; S, 8.03. C44H38N2S2·C8H10 (1:1)
requires C, 81.64; H, 6.32; N, 3.66; S, 8.38%.]
Using equimolar binary and ternary mixtures of ANI, NMA
and DMA
Equimolar guest/guest competition experiments were car-
ried out in order to ascertain whether either of the host
compounds possessed selectivity for any one of the guests
present in various binary and ternary combinations of these
guest solvents. This was accomplished by dissolving the
host (~ 0.05 g) in such mixtures (made up of 5 mmol of
each guest). The capped vials were stored at 0 °C and, once
crystallization occurred, the crystals treated as in the sin-
gle solvent experiments. Analyses to obtain the amounts
of each guest compound present in the host crystals was
accomplished by means of GC-MS (with CH2Cl2 as the dis-
solution solvent) and not 1H-NMR spectroscopy owing to
the overlapping of guest/guest and/or host/guest resonance
signals on the 1H-NMR spectra. All experiments were car-
ried out in duplicate for confrmatory purposes.
Using binary mixtures of ANI, NMA and DMA where their
concentrations were sequentially varied
In these binary guest/guest (GA and GB) competition
experiments, the molar ratio of each guest solvent present
was varied sequentially between approximately 10:90 and
90:10 mol%, and the host compound dissolved in these
mixtures. The vials were capped and stored at 0 ºC so that
crystallization could occur, and the solid fltered under
vacuum, washed and dried, analogously to the procedure
for the equimolar guest/guest experiments. Here, both the
solution (the liquid guest mixture from which crystalliza-
tion occurred) and the so-formed crystals were analysed
using GC-MS which allowed for the determination of the
amounts of both GA and GB in both of these phases (XA
and XB, and ZA and ZB, respectively). A plot of ZA (or ZB)
against XA (or XB) resulted in host selectivity profles,
a manner of visually establishing the host behaviour as
guest concentrations changed. The selectivity coefcient
(K), a measure of the host selectivity, was determined by
means of employing the equation KA:B = (ZA/ZB) × (XB/
XA) where XA+ XB = 1 [23].
Single guest solvent experiments
The host compounds were recrystallized independently from
each of ANI, NMA and DMA. This was achieved by plac-
ing each host material (~0.05 g) in a glass vial and dissolv-
ing it in an excess of the liquid guest; heat was applied to
facilitate dissolution in need. The vials were capped and left
to stand at ambient temperature and pressure after which
recrystallization occurred within 1–3 days. Should crystalli-
zation not have been successful during this time, the capped
vial was then placed in a refrigerator set to 0 °C to further
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Mixed guest solvent experiments
Results and discussion
Using equimolar binary and ternary mixtures of ANI, NMA
and DMA
Synthesis of host compounds 1,2‑DAX and 1,2‑DAT
Novel host compounds 1,2-DAX and 1,2-DAT were pre-
pared in three distinct steps using methods that have been
reported on a prior occasion [22]. This involved a Grignard
addition reaction (phenylmagnesium bromide) on either
xanthone or thioxanthone (Scheme 2), as applicable. The
resultant alcohols were subsequently reacted with perchlo-
ric acid to aford highly coloured crystalline perchlorate
salts, which were then treated with trans-cyclohexane-
1,2-diamine to yield the required compounds in moderate
to excellent yields.
Recrystallization of the host compounds from the various
equimolar combinations of ANI/NMA/DMA resulted in
mixed complexes in each instance; both hosts, additionally,
demonstrated selectivity behaviour. These data are summa-
rised in Table 2. Note that the experiments were conducted
in duplicate, and tabulated ratios are averages; percentage
estimated standard deviations (%e.s.d.s) are provided in
this table in parentheses. Furthermore, bold numbering was
employed to distinguish the preferred guest species in each
experiment for each host compound.
Overall, some similarities are evident in the selectiv-
ity behaviour of the two host compounds (Table 2). Upon
recrystallization of 1,2-DAX from ANI/NMA, NMA was
favoured (66.5%); 1,2-DAT also preferred NMA in these
conditions but the selectivity for this guest was much
reduced here (51.1%). Results from ANI/DMA mixtures
were striking in that both host compounds almost exclusively
selected DMA [91.8% (1,2-DAX) and 90.3% (1,2-DAT)].
Therefore, ANI was consistently discriminated against when
the solutions employed were ANI/NMA and ANI/DMA. In
the absence of ANI, 1,2-DAX displayed an enhanced prefer-
ence for DMA (82.5%) while 1,2-DAT difered and preferred
NMA (61.7%). The selectivity of both hosts for these guests,
as obtained from the ternary mixture experiment, was there-
fore in the same order (DMA>NMA>ANI) and, addition-
ally, the extent of selectivity was similar for both (80.1, 10.8,
9.1 compared with 80.3, 12.9, 6.8%).
Single guest solvent experiments
The H:G ratios after 1H-NMR analysis of the crystals ema-
nating from the recrystallization experiments of each host
independently from ANI, NMA and DMA are summarized
in Table 1.
Both host compounds were efcient for the enclathra-
tion of each of the three aniline solvents (Table 1). While
1,2-DAX unfailingly preferred the 1:1 H:G ratio, 1,2-DAT
formed 1:2 complexes with ANI and NMA, but a 1:1 ratio
was also obtained when this host was recrystallized from
DMA.
Table 1 H:G ratiosa of
Guest
1,2-DAX
1,2-DAT
complexes formed when
1,2-DAX and 1,2-DAT were
recrystallized from ANI, NMA
and DMA
These results indicate that both host compounds may
serve as separation agents for such guest mixtures, particu-
larly when ANI/DMA combinations arise from synthetic
procedures.
ANI
NMA
DMA
1:1
1:1
1:1
1:2
1:2
1:1
aDetermined using 1H-NMR
spectroscopy, with CDCl3 as the
deuterated solvent
Table 2 Applicable G:G
ANI
NMA
x
DMA
Guest ratios (%e.s.d.sc)
(for 1,2-DAX)
Guest ratios (%e.s.d.sc)
(for 1,2-DAT)
ratiosa of complexes formed
when 1,2-DAX and 1,2-DAT
were recrystallized from the
equimolar mixed anilinesb
x
x
33.5:66.5 (0.8)
48.9:51.1 (0.6)
x
x
x
8.2:91.8 (0.7)
9.7:90.3 (0.6)
x
x
17.5:82.5 (0.6)
61.7:38.3 (0.8)
x
9.1:10.8:80.1 (0.4:0.1:0.5)
6.8:12.9:80.3 (0.5:0.7:1.1)
aDetermined using GC-MS with CH2Cl2 as the dissolution solvent
bOverall H:G ratios, obtained using 1H-NMR spectroscopy, were 1:1 in all cases with the exception of the
mixed complex obtained when 1,2-DAT was recrystallized from ANI/NMA (overall H:G 1:2)
cPercentage estimated standard deviations (%e.s.d.s)
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Using binary mixtures of ANI, NMA and DMA where their
concentrations were sequentially varied
Analogous experiments with 1,2-DAT showed the selec-
tivity of this host, in each case, to be guest concentration-
dependent (in stark contrast to the results obtained for 1,2-
DAX, where selectivity was for one guest only, irrespective
of concentration). Figure 2a shows that at lower concentra-
tions of NMA ([NMA]≤30.4), 1,2-DAT displayed a pref-
erence for ANI, and the average KNMA:ANI value calculated
was 0.2 for the three experiments in question. However, as
the concentration of NMA in the solution increased, the
host selectivity changed in favour of this guest. The aver-
age selectivity coefcient for the remainder of the experi-
ments ([NMA] ≥ 53.3%) was 1.1, alluding to a marginal
NMA preference at higher NMA concentrations: when the
guest mixture contained 63.5 and 82.5% NMA, the crys-
tals had 67.6 and 84.6% of this guest, respectively. From
the DMA/ANI and DMA/NMA binary guest experiments
(Figures b and c, respectively), the host was consistently
selective for DMA at higher DMA concentrations (≥48.6
and 60.5%, respectively): when the DMA/ANI solution com-
prised 48.6% DMA or more, the average K value was 9.8
in favour of DMA (a solution with 48.6% DMA aforded
crystals containing 88.9% of this guest). The converse was
true also: at low concentrations of DMA, ANI (Fig. 2b) and
NMA (Fig. 2c) were selected. In the former case, when the
concentration of ANI in solution was equal to or greater
than 72.3%, KDMA:ANI was calculated to be 0.5. In the lat-
ter case, when [NMA]≥47.4%, the average KDMA:NMA was
0.6, and here the host selectivity change (in favour of DMA)
Selectivity profles, upon performing host recrystalliza-
tion experiments from binary mixtures of ANI, NMA
and DMA but changing the mol% of each guest in these
mixtures, are provided in Fig. 1a‒c (1,2-DAX) and 2a‒c
(1,2-DAT). Figure 1a shows that 1,2-DAX discriminated
against ANI in favour of NMA across the entire concentra-
tion range, with an average K value of 2.2 calculated. When
the mother liquor contained 57.2% NMA, the crystals of
the so-formed complex possessed a signifcant amount of
this guest (74.7%). In DMA/ANI and DMA/NMA binary
mixtures (Fig. 1b and c, respectively), the host selectivity
was signifcantly and consistently in favour of DMA, and the
average K values were calculated to be 14.2 and 3.7, respec-
tively. Even at low mother liquor concentrations of DMA in
the DMA/ANI experiment (10.7%, Fig. 1b), the resultant
crystals already contained 80.4% of this guest. Increasing
the DMA content in solution after this point facilitated a
gradual increase of DMA in the crystals: when 91.6% of the
solution was DMA, the crystals contained almost exclusively
DMA (98.5%). As alluded to by the K values obtained from
the DMA/ANI (14.2) and DMA/NMA (3.7) experiments,
the extent of selectivity of 1,2-DAX for DMA was reduced
when ANI was replaced by NMA. For example, when the
mother liquor contained 26.6% DMA, the resultant crystals
possessed only 62.8% of this guest.
1
1
(a)
(b)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X(NMA)
X(DMA)
1
(c)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.1
0.2
0.3
0.4
0.5
X(DMA)
0.6
0.7
0.8
0.9
1
Fig. 1 Host selectivity profles obtained for 1,2-DAX in the presence of a NMA/ANI, b DMA/ANI and c DMA/NMA binary mixtures
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
(a)
1
1
(b)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X(NMA)
X(DMA)
1
(c)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.1
0.2
0.3
0.4
0.5
X(DMA)
0.6
0.7
0.8
0.9
1
Fig. 2 Host selectivity profles obtained for 1,2-DAT in the presence of a NMA/ANI, b DMA/ANI and c DMA/NMA binary mixtures
occurred at DMA concentrations above 60.5% (where the
average KDMA:NMA value was calculated to be 4.1).
group, and the DMA complex in C2/c. Furthermore, this
last complex shared host packing type with the two 1,2-DAX
complexes. Disorder was observed in both 1,2-DAX·ANI
and 1,2-DAX·DMA, with the guest species positioned
around a two-fold rotational axis. Furthermore, the hydro-
gen atom on the host nitrogen was disordered over two
positions in both complexes. All three complexes with 1,2-
DAT also experienced disorder, and two diferent non-sym-
metrical orientations were possible for the guest species in
1,2-DAT·2(ANI). However, the disorder in the DMA com-
plex was due to the guest being positioned near a symmetry
element resulting in this disorder being symmetry generated,
whilst NMA in 1,2-DAT·2(NMA) was severely disordered:
three guest components (G1, G2, and G3) were present in the
unit cell, with one [G1 MJ (major disordered component)
and G1 MN (minor disordered component)] oriented in two
directions (s.o.f.’s of 0.529 and 0.471, respectively), while
the remaining two guest molecules experienced disorder
owing to a symmetry element (s.o.f.’s of 0.50 each for G2
and G3). Additionally, the nitrogen-bound hydrogen atoms
of the host were disordered in the ANI and DMA complexes
of 1,2-DAT.
In conclusion, of the two host compounds, 1,2-DAX may
be regarded as superior in its selectivity behaviour, and may
certainly behave as an efcient separating agent, especially
in the presence of mixtures of ANI and DMA, irrespective
of the concentrations of either guest present (Fig. 1b). 1,2-
DAT is less discerning in these conditions, and its selectivity
behaviour is dependent on guest concentration, regardless
of the types of guest anilines present in the binary mixture.
Single crystal X‑ray difraction (SCXRD) analyses
The three single solvent complexes formed by 1,2-DAT and
the aniline guests were subjected to SCXRD analyses, while
only the ANI- and DMA-containing inclusion compounds
of 1,2-DAX produced crystals of suitable quality for this
analytical technique; the crystal quality of 1,2-DAX·NMA
was inappropriate. Table 3 summarises the relevant crystal-
lographic data that were thus obtained. Both 1,2-DAX·ANI
and 1,2-DAX·DMA crystallized in the monoclinic crystal
system and C2/c space group, and experienced isostruc-
tural host packing as is evident from the unit cell dimen-
sions provided in this table. Similarly, all three complexes
of 1,2-DAT crystallized in the monoclinic crystal system,
1,2-DAT·2(ANI) and 1,2-DAT·2(NMA) in the I2/a space
Host‒guest packing diagrams are provided for
1,2-DAX·ANI (as representative of the three complexes
sharing host‒guest packing type), 1,2-DAT·2(ANI) and
1,2-DAT·2(NMA) in Fig. 3a‒c (left), respectively, together
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Table 3 Crystallographic data for 1,2-DAX·ANI, 1,2-DAX·DMA, 1,2-DAT·2(ANI), 1,2-DAT·2(NMA) and 1,2-DAT·DMAa
1,2-DAX·ANIb
1,2-DAX·DMAb
1,2-DAT·2(ANI)
1,2-DAT·2(NMA)
1,2-DAT·DMAb
Chemical formula
Formula weight (g/mol)
Crystal system
C44H38N2O2·C6H5N C44H38N2O2·C8H11N C44H38N2S2·2(C6H5N) C44H38N2S2·2(C7H9N) C44H38N2S2·C8H11N
717.87
Monoclinic
C2/c
747.94
Monoclinic
C2/c
841.10
Monoclinic
I2/a
873.19
Monoclinic
I2/a
780.06
Monoclinic
C2/c
Space group
µ (Mo Kα)/mm−1
0.073
0.075
0.159
0.156
0.167
a/Å
b/Å
c/Å
α/°
14.2367(9)
14.2099(9)
19.6234(13)
90
14.2849(7)
14.2602(6)
19.6725(9)
90
21.2117(14)
9.1358(5)
24.4234(17)
90
18.950(2)
15.0422(19)
33.561(4)
90
15.4768(9)
13.9742(7)
19.3645(10)
90
β/°
92.451(3)
90
3966.2(4)
4
90.302(2)
90
4007.3(3)
4
104.641(5)
90
4579.2(5)
4
97.784(7)
90
9478.4(19)
8
91.465(2)
90
4186.7(4)
4
γ/°
V/Å3
Z
F (000)
Temp (K)
Restraints
Nref
1520
200
42
4932
1592
200
0
5013
1776
296
16
5765
3712
296
102
11873
552
1656
200
0
5199
Npar
276
296
249
296
R
wR2
S
0.0487
0.1353
1.02
0.0427
0.1197
1.04
0.0738
0.2568
1.05
0.0630
0.2135
1.03
0.0432
0.1207
1.03
Θ min, max/°
Tot. data
Unique data
2.0, 28.4
37253
4932
2.0, 28.3
54421
5013
1.7, 28.7
62581
5765
1.5, 28.4
129352
11873
7663
2.0, 28.3
32707
5199
Observed data
3594
4058
3758
4270
[ I>2.0σ(I) ]
Rint
Completeness
0.023
1.000
0.022
1.000
0.028
1.000
0.033
1.000
0.023
1.000
Min. and Max. resd. dens.
–0.24, 0.24
–0.18, 0.29
–0.57, 0.61
–0.50, 0.49
–0.54, 0.41
(e/Å3)
a1,2-DAX·NMA was characterised by poor crystal quality, and SCXRD analysis was not possible for this complex.
bThese three complexes experienced isostructural host packing.
with void diagrams (right), which were prepared by remov-
ing each guest species and recalculating the spaces remain-
ing using a probe radius of 1.2 Å.
A close analysis of the host‒guest interactions responsi-
ble for guest retention was subsequently undertaken in each
case.
The guest components in 1,2-DAX·ANI, 1,2-DAX·DMA
and 1,2-DAT·DMA all occupied isolated cavities in the host
crystal (Fig. 3a) while both ANI and NMA were accom-
modated in channels in 1,2-DAT (Fig. 3b and c). It is clear
from these fgures that the preferred guest for both host com-
pounds, DMA, was always found in discrete cavities and the
host packing, too, was identical in each; a prior report by
Caira et al. [24] associated this accommodation type (dis-
crete cavities) with enhanced complex stability.
1,2-DAX interacted with both ANI and DMA by means
of numerous but very weak (host)π···π(guest) interactions
ranging between 5.082(5) and 5.946(5), and 4.970(1) and
5.911(2) Å, respectively. Furthermore, ANI also experienced
a classical hydrogen bond with this host [Fig. 4, 3.413(9)
Å, 164(3)º], where ANI behaved as an acceptor, while an
interaction of this kind with DMA was absent. However,
DMA was additionally involved in two (guest)CH···π(host)
contacts [2.94 Å (140º), 2.93 Å (141º)] and also a (guest)
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 3 Host‒guest packing (left) and void (right) diagrams for a 1,2-DAX·ANI (as representative for the three isostructural complexes), b
1,2-DAT·2(ANI) and c 1,2-DAT·2(NMA)
ArH···HAr(host) interaction. Overall, DMA therefore expe-
rienced a greater number and type of interactions with the
host, in accordance with the preference of 1,2-DAX for this
guest.
evident in the ANI and NMA complexes [4.999(6)–5.884(8)
Å]. A further fve XH···π bonds, absent in 1,2-DAT·2(ANI),
were also observed in 1,2-DAT·2(NMA). Two of these
occurred between the NH group of one guest moiety and the
π system of another guest molecule (2.73 and 2.47 Å, 164
and 148°). A single (guest)CH···π(host) contact was also evi-
dent in the 1,2-DAT·DMA complex (2.91 Å, 141°). Notably,
classical host–guest hydrogen bonds were absent in all three
With respect to those complexes formed by 1,2-DAT, a
large number of weak host–guest π···π interactions were wit-
nessed in all three, ranging between 4.771(3) and 5.981(2) Å,
while guest–guest interactions of this kind were additionally
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 4 A classical host‒guest
hydrogen bond (green) present
in 1,2-DAX·ANI; here, ANI
serves as the acceptor and the
host compound as the donor
molecule
inclusion compounds, but an abundance of other short con-
tacts was observed, ranging from 2.31 to 2.87 Å (134–169°),
while guest–guest short contacts ranged between 1.87 and
3.231(2) Å (108–164°). The preference of 1,2-DAT for
DMA, upon close analyses of these interactions, is there-
fore not clear from these SCXRD data alone. However, as
noted before, DMA was the only guest to be accommodated
in cavities, while ANI and NMA occupied unconstricted and
infnite channels in the crystal, an observation that may be
responsible for the host preference for DMA, owing to the
enhanced thermal stability associated with discrete cavity
occupation [24].
close agreement (Table 4). Finally, the host melt occurred
between 227.2 and 229.1 ºC (the peak temperatures obtained
from the host melt endotherms).
The thermal traces obtained for the three complexes with
1,2-DAT (Fig. 6a‒c) were strikingly more convoluted than
those for 1,2-DAX: 1,2-DAT·2(ANI) released the guest in
what appeared to be two or more indistinct steps, and the host
melt was not discernable on the trace. A similar scenario was
observed for both 1,2-DAT·2(NMA) and 1,2-DAT·DMA,
with the absence of a clear host melt endotherm on each.
Additionally, the experimentally obtained mass losses for
these complexes upon complete guest removal were signif-
cantly lower than those calculated. An explanation for these
discrepancies may be that the TG (the red trace), with its
continual downward slope in each instance, ensured dif-
culty in determining the temperatures at which guest loss
was complete. However, the endotherm peak temperatures,
as was the case for the complexes of 1,2-DAX, correlated
satisfactorily with the host selectivity order noted before
[DMA (157.1 ºC) > NMA (125.1 ºC) > ANI (110.2 ºC)].
The observation of Caira et al. [24] that host‒guest com-
plexes display increased relative thermal stabilities when
guests are retained in cavities compared with those where
these are accommodated in channels is therefore supported
by the results of experiments in this current investigation
(DMA was the only guest to be accommodated in discrete
cavities by 1,2-DAT, while ANI and NMA occupied uncon-
stricted and infnite channels; the complex containing DMA
did indeed possess a higher thermal stability (Tp 157.1 ºC)
Thermal [thermogravimetric (TG), its derivative (DTG)
and diferential scanning calorimetry (DSC)] analyses of all
of the complexes formed in this investigation were subse-
quently conducted in order to confrm the thermal stability
predictions that have been alluded to before. Figure 5a‒c
and 6a‒c are the overlaid thermal traces thus obtained upon
heating of the samples from approximately room tempera-
ture to 300 ºC.
Table 4 summarises the relevant thermal data from
Figs. 5a‒c and 6a‒c.
The guest release processes for the complexes with 1,2-
DAX, largely, occurred in a single step (Fig. 5a‒c). The
endotherm peak temperatures (blue trace) representing this
process (Tp) decreased in the order DMA (181.8 ºC)>NMA
(173.2 ºC)>ANI (164.8 ºC), which correlates exactly with
selectivity observations made before. Furthermore, expected
and measured mass losses for these 1:1 complexes were in
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 5 Thermal (TG, DTG and DSC) traces for a 1,2-DAX·ANI, b 1,2-DAX·NMA and c 1,2-DAX·DMA
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 5 (continued)
than 1,2-DAT·2(ANI) (Tp 110.2 ºC) and 1,2-DAT·2(NMA)
(Tp 125.1 ºC).
favoured DMA (irrespective of its concentration), the behav-
iour of the sulfur-containing host depended on guest con-
centration, only preferring that guest that was present in
increased amounts. SCXRD analyses were used to under-
stand the host selectivity for DMA: 1,2-DAX experienced a
greater number and type of host‒guest interactions with this
guest, while the preference of 1,2-DAT for DMA was less
clear using this analytical technique. However, thermal anal-
yses undoubtedly showed that the relative thermal stabilities
of the complexes were in the order DMA>NMA>ANI for
both host compounds, which correlated exactly with their
selectivity behaviours when recrystallized from such guest
mixtures. 1,2-DAX and 1,2-DAT may therefore be employed
successfully to purify various mixtures of ANI/NMA/DMA.
Conclusion
This work sought to answer the question as to whether host‒
guest chemistry may be employed in order to separate ANI/
NMA/DMA mixtures using either 1,2-DAX and 1,2-DAT,
novel compounds, as hosts. Such mixtures are industrially
relevant since NMA and DMA are synthesized from ANI.
It was revealed that both host compounds possess enhanced
selectivities for DMA, more especially when recrystallized
from equimolar binary mixtures where the other guest was
ANI (ANI:DMA 8.2:91.8 and 9.7:90.3 for 1,2-DAX and
1,2-DAT, respectively). Furthermore, 1,2-DAX fared sig-
nifcantly better than 1,2-DAT if the molar amounts of DMA
in binary mixtures were varied: while 1,2-DAX consistently
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 6 Thermal (TG, DTG and DSC) traces for a 1,2-DAT·2(ANI), b 1,2-DAT·2(NMA) and c 1,2-DAT·DMA
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
Fig. 6 (continued)
Table 4 Relevant thermal data
Guest
1,2-DAX
Tp
1,2-DAT
for complexes formed by 1,2-
DAX and 1,2-DAT
a
a
Mass loss
Mass loss
Tp
Mass loss
Mass loss
/ºC
observed/%
expected/%
/ºC
observed/%
expected/%
ANI
NMA
DMA
164.8
173.2
181.8
12.9
14.6
17.7
12.9
14.6
16.2
110.2, 172.2
125.1
157.1
17.7
13.0
13.7
22.0
24.5
15.5
aTp is the endotherm peak temperature that represents the guest release process, is where guest loss is most
rapid, and may be used as a measure of relative thermal stability
Supplementary information
References
1. Kahl, T., Schröder, K.-W., Lawrence, F.R., Marshall, W.J., Höke,
H., Jäckh, R.: Ullmann’s Encyclopedia of Industrial Chemistry,
7th edn. Weinheim, VCH (2011) Germany
Crystallographic data for the novel complexes were depos-
ited at the Cambridge Crystallographic Data Centre,
where SCXRD analyses were possible {{CCDC-1982613
(1,2-DAX·ANI), 1982614 (1,2-DAX·DMA), 1982615
[1,2-DAT·2(ANI)], 1982616 [1,2-DAT·2(NMA)] and
1982617 (1,2-DAT·DMA)}}. These data may be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
2. Mamytov, K.Z., Beisenbayev, O.K., Shvets, V.F., Syrmanova,
K.K.: The Multifunctional Automobile Gasoline Additive on the
Basis of Amino-Aromatic Hydrocarbons and Oxygen-Containing
Compounds. Eurasian Chem.-Technol. J. 14, 249–252 (2012)
3. Taber, D.F., Meagley, R.P., Supplee, D.: A colorful grignard reac-
tion: preparation of the triarylmethane dyes from 4-bromo-N,N-
dimethylaniline. J. Chem. Educ. 73, 259–260 (1996)
4. Badr, M., Aly, M.: Molecular rearrangements. Part IV. Aryl
(Alkyl) Amines (1), thermal rearrangement of N-Benzyl-N-meth-
ylaniline. Can. J. Chem. 52, 293–298 (1974)
Acknowledgements Financial support is acknowledged from the Nel-
son Mandela University and the National Research Foundation (NRF).
5. Niphadkar, P.S., Joshi, P.N., Gurav, H.R., Deshpande, S.S.,
Bokade, V.V.: Synthesis of N-methylaniline by aniline alkylation
with methanol over Sn-MFI molecular sieve. Catal. Lett. 133,
175–184 (2009)
1 3

Journal of Inclusion Phenomena and Macrocyclic Chemistry
6. Atwood, J.L., Suslick, K.S., Lehn, J.-M.: Comprehensive Supra-
molecular Chemistry: Supramolecular Reactivity and Transport:
Bioinorganic Systems. Elsevier, Amsterdam (1996)
and DMT, in the presence of two diferent classes of aromatic
guest compounds. Tetrahedron 74, 4754–4760 (2018)
16. Barton, B., de Jager, L., Hosten, E.C.: Comparing the host behav-
iour of N,N’-bis(9-phenyl-9-thioxanthenyl)ethylenediamine and
N,N’-bis(9-phenyl-9-xanthenyl)ethylenediamine in the presence of
various alkylated aromatic and aniline guests: crystal engineering
considerations. CrystEngComm. 21, 4387–4400 (2019)
17. Bruker, A.X.S., APEX2, S.A.D.A.B.S., Bruker, S.A.I.N.T.:
A.X.S., Madison, WI (2010)
7. Atwood, J.L., Steed, J.W.: Encyclopedia of Supramolecular Chem-
istry. CRC Press, Marcel Dekker, Inc. New York (2004)
8. Steed, J.W., Atwood, J.L.: Supramolecular,&Nbsp;Chemistry.
Wiley, New Yok (2009)
9. Samipillai, M., Batisai, E., Nassimbeni, L.R., Weber, E.: Separa-
tion of lutidines by enclathration. CrystEngComm 17, 8332–8338
(2015)
18. Sheldrick, G.M.: SHELXT-integrated space-group and crystal
structure determination. Acta Crystallogr. A 71, 3 (2015)
19. Sheldrick, G.M.: Crystal structure refnement with SHELXL. Acta
Crystallogr. C 71, 3 (2015)
10. Caira, M.R., Nassimbeni, L.R., Vujovic, D., Toda, F.: Separation
of xylenols by inclusion. J. Phys. Chem. 13, 75–79 (2000)
11. Lusi, M., Barbour, L.J.: Solid–vapor sorption of xylenes: prior-
itized selectivity as a means of separating all three isomers using
a single substrate. Angew. Chem. Int. Ed. Engl. 51, 3928–3931
(2012)
20. Hübschle, C.B., Sheldrick, G.M., Dittrich, B.: ShelXle: a Qt
graphical user interface for SHELXL. J. Appl. Crystallogr. 44,
1281 (2011)
12. Barton, B., de Jager, L., Hosten, E.C.: Host behaviour of N,N’-
Bis(9-phenyl-9-thioxanthenyl)ethylenediamine in the presence of
aromatic and aliphatic fve-membered heterocyclic guests: selec-
tivity correlations with Hirshfeld surface analyses. Cryst. Growth
Des. 19, 1268–1281 (2019)
21. Mercury 3.10.2: (Build 189770), http://www.ccdc.cam.ac.uk/
mercury/. Accessed 2019.]
22. Barton, B.: Host–Guest Chemistry: The Synthesis and Assessment
of Host Compounds Based on the 9-Arylxanthenyl and Related
Systems. University of Port Elizabeth, Port Elizabeth (1996)
23. Sykes, N.M., Su, H., Weber, E., Bourne, S.A., Nassimbeni, L.R.:
Selective enclathration of methyl- and dimethylpiperidines by
fuorenol hosts. Cryst. Growth Des. 17, 819–826 (2017)
24. Tanaka, K., Hori, K., Tsuyuhara, S., Motoki, S., Shide, S.,
Arakawa, R., Caira, M.R.: Role of halogen bonding in clathrate
formation of tetra- and hexasalicylides derived from halogenated
salicylic acids. Tetrahedron 69, 1120–1127 (2013)
13. Barton, B., Dorfing, S.-L., Hosten, E.C.: Inclusion ability of
host TETROL [(+)-(2R,3R)-1,1–4,4-tetraphenylbutane-1,2,3,4-
tetraol] for selected saturated cyclic and aromatic alcohol, ketone
and amine guest compounds. J. Incl. Phenom. Macrocycl. Chem.
95, 331–340 (2019)
14. Barton, B., Hosten, E.C., Pohl, P.L.: Host (–)-(2R,3R)-2,3-dimeth-
oxy-1,1,4,4-tetraphenylbutane-1,4-diol and guests aniline,
N-methylaniline and N,N-dimethylaniline: a selectivity study.
Aust. J. Chem. 71, 133–141 (2018)
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
15. Barton, B., de Jager, L., Dorfing, S.-L., Hosten, E.C., McCleland,
C.W., Pohl, P.L.: Host behaviour of related compounds, TETROL
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