Halide ion recognition: Via chalcogen bonding in the solid state and in solution. Directionality and linearity

Article abstract of DOI:10.1039/c8ce01365a

Group 16 chalcogen atoms may exhibit Lewis acidic σ-holes which are able to form attractive supramolecular interactions with Lewis bases via chalcogen bonds (ChB). Interest in ChB is increasing rapidly; however, the potential for anion binding has not been fully explored. Herein we report on the application of chemically robust and stable benzylic selenocynates (1 and 2) for halide ion recognition in the solid state and in solution. Single crystal X-ray structural analysis of various cocrystals reveals structurally important Se?X^- (X = Cl, Br, I) chalcogen bonds. Changes in the ¹³C and ⁷⁷Se chemical shifts via NMR spectroscopy show how halide ion recognition influences the local electronic environment of the selenium atoms in solution. Deviations of the interaction from the extension of the C-Se covalent bond are quantified and assessed with the aid of computational chemistry.

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Halide ion recognition via chalcogen bonding in the solid state and
in solution. Directionality and linearity
Vijith Kumar,a Cesar Leroy,a and David L. Bryce*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Group 16 chalcogen atoms may exhibit Lewis acidic σ-holes which are able to form attractive supramolecular interactions
with Lewis bases via chalcogen bonds (ChB). Interest in ChB is increasing rapidly; however, the potential for anion binding
has not been fully explored. Herein we report on the application of chemically robust and stable benzylic selenocynates (1
and 2) for halide ion recognition in the solid state and in solution. Single crystal X-ray structural analysis of various
cocrystals reveals structurally important Se···X⁻ (X = Cl, Br, I) chalcogen bonds. Changes in the 13C and 77Se chemical shifts
via NMR spectroscopy shows how halide ion recognition influences the local electronic environment of the selenium
atoms in solution. Deviaꢀon of the interacꢀon from the extension of the C―Se covalent bond are quantified and assessed
with the aid of computational chemistry.
www.rsc.org/
nature of the nitrile group which promotes the formation of a
strong σ-hole on the chalcogen atom along the prolongation of
the NC–Se/Te bond.13 A detailed CSD survey of the previously
Introduction
In the sundry areas of supramolecular chemistry, crystal
engineering, materials science, and biochemistry, noncovalent
interactions are of key import for structural and functional
reasons. While conventional hydrogen bonding (HB) has long
been acknowledged as a vital interaction,1 halogen bonding
(XB) is also now recognized as a critical component of a variety
of supramolecular architectures.2 As with XB, chalcogen
bonding (ChB), is a subgroup of the σ-hole interactions. ChB
results from the interaction between an electrophilic region of
a Group 16 element (e.g., S, Se, Te) and an electron donor, and
has recently emerged as a promising parallel noncovalent
interaction.3 As a result of their strength and directionality,
comparable to HB and XB, chalcogen bonds have recently
taken on increased prominence in a range of fields including
crystal engineering, organic reactivity, supramolecular self-
assembly, and pharmaceuticals.4, 5, 6, 7
reported crystal structures of organic selenocyanates
confirmed this hypothesis, i.e., that most of the simple
aliphatic and aromatic organic selenocyanates do crystallise
with ChB interactions. In the absence of other Lewis bases, the
Se atom interacts with the N atom of a neighbouring
selenocyanate moiety.15 Recently, Fourmigué and co-workers
reported that benzylic selenocyanates are strong and
directional ChB donors for crystal engineering purposes, where
the chain-like motifs can be tuned into 1D extended structures
upon co-crystallization with 4,4-bipyridine as a ditopic ChB
acceptor.16
Although substantial evidence is growing which
demonstrates the existence of ChB in solid state, solution-
phase studies involving ChB are fewer. Recently, two elegant
studies demonstrating ChB-assisted anion recognition with
benzotelluradiazoles17a
and
5-(methylchalcogeno)-1,2,3-
Benzo-selenazoles/tellurazoles,8 bithiophenes,9 tellurazole
N-oxides,10 selenophtalic anhydrides,11 bistellurophene,12 and
triazole in macrocycles17b have been described. Although the
heavier chalcogens (Se, Te) are expected to have enhanced
ChB donor properties, their compounds can be susceptible to
oxidative decomposition, thus restricting the incorporation of
such elements into more complex systems and rendering
difficult studies of anion binding properties. Herein, we show
that benzylic selenocyanate derivatives are chemically robust
and stable ChB motifs for anion recognition (Fig. 1) that can
adapt their conformations to enable halide ion recognition in
solution and in the solid state. We also quantify the directional
relationships between the C―Se bond extension, the
maximum of the molecular electrostatic potential surface, and
the position of the ChB acceptor.
bis(benzimidazolium-selenomethyl)
derivatives13
were
considered as conceptually innovative motifs for the design of
ChB systems. Seleno/tellurocyanides are particularly appealing
candidates. They were originally identified several years ago
and re-explored recently14 due to the electron-withdrawing
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With this inspiration, we investigated the cocrystallisation
of ChB donors and with tetrabutylammonium halides
1
2
(iodide, bromide, and chloride). Cocrystallisation was
performed via diffusion of Et2O over an acetone solution of
both tectons (this produced crystals of better quality for
SCXRD analysis than did simple slow evaporation from
acetone); the amount of onium halide added in each case was
based on the number of Se donor sites available for ChB
formation (see the Experimental section for details). Complex
formation is preliminarily confirmed by PXRD analysis (see Fig.
2 and ESI S.2) and changes in the melting point of the complex
in comparison with pure individual tectons. Single-crystal X-ray
structural analysis of the complexes shows that ChB complexes
Fig. 1 Molecular structures of the benzylic selenocyanates (top) and
their MESP (bottom) with an isodensity of 0.02 a.u. (B3LYP with 6-
311G**) Red indicates negative charge density, and blue positive
charge density. A common scale was used to compare the surfaces
visually.
1⸱ (Bu4N)Br and 1⸱ (Bu4N)I crystallise in the monoclinic
space group P21/c with Z = 4 (Table 2). Both of the structures
exhibit similarity in the crystal packing, where the short and
directional Se···I⁻ and Se···Br⁻ ChBs are largely responsible for
the self-assembly of the two complementary modules. The
topology of the primary network is a good example of the
paradigm of the expansion of a ditopic starting module by a
halide linker moiety: 1 acts as a ditopic ChB-donor while onium
halides behave as strong ChB acceptors (Fig.3, ESI Fig.S5-S6).
The geometrical parameters describing the ChB contacts are
reported in Table 1.
Fig. 2 PXRD patterns of ChB donor
Experimental pattern of pure ChBD (A, red); experimental pattern of
pure (Bu4N)I (B, blue); experimental pattern of the (Bu4N)I
cocrystal obtained by solution crystallization (C, purple), simulated
, onium iodide, and cocrystal:
1
1
⸱
pattern of the
(D, black).
1⸱ (Bu4N)I cocrystal obtained by single-crystal structure
Fig. 3 Top: displacement ellipsoid plots (ellipsoids are drawn at the 50%
probability level) of chalcogen bonded complexes running along the
crystallographic b axis, 1⸱ (Bu4N)I (top left) and 1⸱ (Bu4N)Br (top right);
colour codes: grey, carbon; white, hydrogen; yellow, selenium; blue,
nitrogen; purple, iodine; brown, bromine (dashed black lines denote ChB).
Bottom: Hirshfeld surfaces plotted against dnorm for the cocrystals 1⸱ (Bu4N)I
(bottom left) and 1⸱ (Bu4N)Br (bottom right): the red colour highlights the
area of ChB formation.
Results and discussion
The bis and tetrakis benzylic selenocyanates (
1 and 2) are
prepared from their respective benzyl bromides and potassium
selenocyanates in DMF under an argon atmosphere (see
Experimental).18 Structural analysis of the pure donors via
single-crystal X-ray diffraction reveals that the crystal packing
is mainly driven by intramolecular Se⸱ ⸱ ⸱
interactions, resulting in a chain-like structure for
POXYEH,15 ESI Fig. S.3) and layered motifs in
PEYRET,16b ESI Fig. S.4). In the field of halogen bonding, ditopic
or tritopic structures have been recently considered for anion
recognition purposes due to their abilities to adapt their
conformational geometries.19
N
ChB
1
(ref. code
To test the generality and the robustness of ChB, we have
challenged the ditopic ChB donor 1 with the lighter onium chloride;
the cocrystal forms in the monoclinic space group I2/m with Z = 4,
with both 1 and onium chloride located on inversion centers (Table
2). Several attempts were made to obtain good quality crystals for
SCXRD analysis. A series of solvents and various crystallization
2
(ref. code
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a
The normalized contact Nc is defined as the ratio DXY/(rX+rY), where
DXY is the experimental distance between the selenium atom X and
halide anions Y and rX is the van der Waals radius for selenium (1.90)
and rY is the Pauling ionic radius of the halide anion Y (I⁻, 2.16; Br⁻,
1.95; Cl⁻, 1.81), respectively.
techniques were employed (see Table S.1 in the Electronic
Supplementary Information). Slow solvent evaporation, rapid
evaporation, slow cooling, vapour diffusion, and convection
crystallization in a narrow tube were attempted. Even in the best
cases, a soft multicrystalline material was obtained. The cocrystal
has a low melting point. In addition to these problems, one of the
n-butyl groups is disordered about a crystallographic mirror plane.
All of these factors contribute to the woeful Rint value (ESI).
Interestingly, donor 1 adapts its conformation and the chloride
anions behave as bidentate ChB acceptors (Fig. 4). The efficiency of
this coordination is further evidenced by the cocrystallisation of
The halide anions vary in size from 119 to 206 pm (fluoride to
iodide anions when octahedrally coordinated), and they can
template correspondingly different self-assembled structures.20 It
has been shown that the different halides can drive the formation
of different structures when involved in electrostatic interactions,
metal coordination, HB,21 and XB,22 and the same is noted here for
tetrakis substituted donor
2 with onium halides. Complex
ChB.
2
⸱
(Bu4N)I once again crystallises in the monoclinic space group
The “molecule in crystal” approach implicit in Hirshfeld surface
analysis was utilized to make quantitative comparisons between
contributions to crystal packing from various types of
P21/c with Z = 2, with both 2 and onium iodide located on the
inversion centers, and where the iodide ion acts as a bidentate ChB
acceptor and engages in short and directional Se···I⁻ ChBs with the 4
selenocyanate groups (Fig. 4; ESI Fig. S7). Unfortunately, we were
intermolecular contacts.23 This method enables the identification of
individual interactions throughout the electron density weighted
molecular surfaces or Hirshfeld surfaces. Hirshfeld surfaces of the
cocrystals are mapped with dnorm and the electrostatic potential
plotted on the Hirshfeld surface, where the ChB interactions are
visualized in red (Fig. 3 bottom; ESI S.5), depicts ChB formation in
the cocrystals. The analysis carried out for pure ChB donors and
cocrystals quantifies the intermolecular interactions and highlights
the contributions from Se···X⁻, C−N···H, and other short contacts
(ESI Fig. S11).
unable to obtain crystals of 2⸱ (Bu4N)Br and 2⸱ (Bu4N)Cl suitable
for SCXRD analysis; however, ChB-driven complex formation was
confirmed by solution NMR spectroscopy (vide infra; ESI S.4).
As a preliminary gauge of the ChB donor ability, molecular
electrostatic potential surfaces (MESP) were calculated for the pure
ChB donors and their cocrystals. The MESP maps were visualized
and traced over electron density surfaces with an isodensity of 0.02
a.u. (electron bohr−3). MESP surfaces of the pure ChB donors clearly
show the presence of two electropositive regions (dark blue) on
each Se atom (528.8 and 622.2 kJ/mol for 1 and 547.67 and 638.78
kJ/mol for 2 respectively); the region along the prolongation of the
electron withdrawing Se−CN bond is more posiꢀve than the region
along the extension of the Se−CH2 single bonds (Fig. 1 bottom, ESI
Fig. S.12, Table S.3). These positive regions, characteristic of σ-holes
on the chalcogen atoms, interact with the negative MESP surface on
the halide ions (red regions) functioning as electron donors (Fig. 5),
individually corresponding to the Se···Cl⁻, Se··· Br⁻, Se···I⁻ (Table 1)
chalcogen bonds differing slightly in length that increase with the
size of the halide ion. In addition, the C‒Se···X⁻ ChB angles range
from 170.86 to 174.88° (Table 1), deviating slightly from linearity,
akin to XB, the sister σ-hole interaction.24 The presence of the
halide induces a decrease in the VS,max on the Se atoms compared
to the free donor (ESI Table S.3).
Fig 4. Molecular structures represented as displacement ellipsoid plots
(ellipsoids are drawn at the 50% probability level) of chalcogen bonded
complexes 1⸱ (Bu4N)Cl (left) and 2⸱ (Bu4N)I (right) show the adaptation of
the geometry of the benzylic selenocyanate donors to interact with halide
ions; colour codes: grey, carbon; white, hydrogen; yellow, selenium; blue,
nitrogen; purple, iodine; green, chlorine (dashed black line denotes ChB).
All the observed ChBs are quite short and linear (Table 1), with
values similar to those reported for other chalcogen bonded
systems involving selenium derivatives.16b These features confirm,
once again, that the supramolecular synthon Se···X⁻ is strong and
reliable and that the onium halide ChB acceptor module is a very
efficient building unit to promote the formation of ChB adducts. In
addition to ChB, crystal packing is further stabilised by HB between
the nitrile N atom and hydrogens of the onium salts’ aliphatic
chains in all cocrystals.
Table 1. Summary of the C‒Se···X⁻ chalcogen bonding geometries
observed via SCXRD.
cocrystal
Se···X⁻ (Å)
C‒Se···X⁻ (˚)
Nc
3.506(1)
3.249(1)
3.192(2)
3.451(1)
3.511(1)
174.98(9)
174.40(2)
174.42(3)
171.92(1)
170.86(1)
0.86
0.84
0.86
0.85
0.86
1⸱ (Bu4N)I
1⸱ (Bu4N)Br
1⸱ (Bu4N)Cl
2⸱ (Bu4N)I
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Fig. 5 Electrostatic potential surface with an isodensity of 0.02 a.u. of
cocrystals: 1 with (Bu4N)Br (left); 1 with (Bu4N)Cl (right) (B3LYP with 6-
311G**) Red indicates negative charge density, and blue positive charge
density. A common scale was used so that the surfaces can be compared
visually.
Table 2. Selected crystallographic data and structural refinement details for the cocrystals.
Compound
1⸱ (Bu4N)I
1⸱ (Bu4N)Br
1⸱ (Bu4N)Cl
2⸱ (Bu4N)I
CCDC number
1849844
1849846
C21H40BrN2Se
479.42
1851129
1849845
Empirical formula
Molecular weight (g.mol-1)
C21H40N2SeI
526.41
C26H44ClN3Se2
592.01
C46 H82 I2 N6 Se4
1288.81
Crystal size (mm3)
0.24, 0.21, 0.15
0.25, 0.19, 0.12
0.24, 0.18, 0.17
0.26, 0.2, 0.14
Crystal system
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
I2/m
Monoclinic
P21/c
Space group
Temperature (K)
200
200
200
200
a (Å)
b (Å)
c (Å)
α(°)
β (°)
γ(°)
8.059(4)
14.506(6)
21.979(10)
90
7.8550(12)
14.479(2)
21.667(3)
90
12.5130(13)
14.1548(18)
17.6517(18)
90
12.145(4)
8.651(2)
26.550(8)
90
90.494(11)
90
90.775(3)
90
101.041(7)
90
96.341(7)
90
V (Å3)
2569(20)
4
2464.1(6)
4
3068.6(6)
4
2772.5(15)
2
Z
μ (mm−1
)
2.669
3.152
2.514
3.794
R_all, R_obs
0.045, 0.031
0.080, 0.075
0.110, 0.057
0.163, 0.146
0.152, 0.092
0.237, 0.198
0.055, 0.032
0.073, 0.067
wR2_all, wR2_obs
for the occurrence of ChB in solution. ChB causes a decrease in the
chemical shift (Δδ13C ranging from 0.85 to 2.84 ppm) upon the
formation of the C-Se···X⁻ moꢀf (Table 3). 77Se NMR is also highly
sensitive to changes in the electronic and structural environment.
As shown in Table 3, halide ion binding to ChB donors 1 and 2 in
DMSO-d6 resulted in large changes in the 77Se NMR chemical shifts,
ranging from -2.23 ppm (for 2.(Bu4N)I) to -9.56 ppm (for 2.(Bu4N)Cl).
A detailed quantum chemical investigation of the origins of these
shifts is beyond the scope of this communication; however, it is
clear that anion binding significantly affects the electronic
environment of the selenium donor atom.
Table 3. 13C and 77Se Chemical shift changes in solution (in ppm)
ChB donor
ChB acceptor
Δ
77
Δδ13C CH2
Se
(Bu4N)I
(Bu4N)Br
(Bu4N)Cl
(Bu4N)I
-7.12
-8.54
-9.75
-2.23
-5.85
-9.56
0.85
1.48
1.96
1.11
2.14
2.84
1
2
(Bu4N)Br
(Bu4N)Cl
0.25 M solutions of ChB donors in DMSO-d6 were used. δ77Se: 321.16
ppm, δ13C CH2: 32.79 ppm for 1; δ77Se: 311.12 ppm, δ13C CH2: 29.62
ppm for 2. The amount of ChB acceptor added was chosen in order
to form a solution containing equimolar amounts of ChB donor and
acceptor atoms.
Having established the involvement of ChB interactions in the anion
binding behaviour of selenium in the crystalline state, 13C and 77Se
NMR were used to qualitatively monitor halide binding in solution
(ESI S.4). The 13C chemical shift of the methylene carbon covalently
bonded to the selenium in the ChB donor can be a good indicator
Fig. 6 Local geometry of the ChB to selenium, indicating the angles between
the extension of the C-Se bond axis and: (i) the maximum of the ESP (θ); (ii)
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the Se...X- axis . VS,max and X- may or may not reside on the same side of
(ϕ)
the bond extension.
filtered using Whatman filter paper and dried overnight at 80° C.
96% yield, white solid.
1
Melting point: 149-152° C. H NMR (300 MHz, DMSO-d6) δ 7.37 (s,
A final point of interest concerns the linearity of the chalcogen
bonds and the geometrical relationship between the maximum of
the MESP, the extension of the C-Se bond axis, and the Se...X- axis
(Fig. 6; Table 4). In halogen-bonded systems, these three axes tend
to coincide closely, whereas there is growing evidence in the
literature24 for a misalignment of these in chalcogen-bonded
systems. For the ChB donors reported here, we observe a deviation
of VS,max from the extension of the C-Se bond axis of 16 to 18°; this
4H), 4.31 (s, 4H). 13C NMR (75 MHz, DMSO-d6): 138.4 (C=C), 129.6
(C-H), 105.4 (CN), 32.77 (CH2). 77Se NMR (DMSO-d6): 321.2 (2Se, s).
Synthesis of benzylic selenocyanate 2: A solution of potassium
selenocyanate (1.9 g, 13 mmol, 6 eq) in anhydrous DMF (25 mL) is
added dropwise over a period of 30 min to a solution of 1, 2, 4, 5-
tetrakis(bromomethyl) benzene (1 g, 2 mmol, 1 eq) under an argon
atmosphere. Upon addition, the solution turns pink and slowly
turns cloudy. The reaction was monitored by thin layer
chromatography (eluent petroleum ether/ether 1/2). After
completion of the reaction (typically 30 to 40 min), addition of 60
mL of warm water (40° C) precipitated an off-white solid. Further,
the solid was washed twice with 60 mL of warm water (40° C) in an
ultrasonic bath for 5 min. The solid was filtered using Whatman
filter paper and dried overnight at 80 °C. 95% yield, white solid.
Melting point: 158-163° C (decomposes). 1H NMR (300 MHz, DMSO-
d6) δ in ppm 7.38 (s, 2H), 4.45 (s, 8H). 13C NMR (75 MHz, DMSO-d6):
136.83 (C=C), 133.86 (C-H), 105.0 (CN), 29.6 (CH2). 77Se NMR
(DMSO-d6): 311.12 (4Se, s).
increases to 21 to 26° in the cocrystals (see angle
Furthermore, the Se...X- axis also deviates from the extension of the
C-Se bond axis by 5 to 9° ( in Fig 6), but not always necessarily
towards the presumably preferred binding site at VS,max An
θ in Fig 6).
ϕ
.
inspection of the crystal structures suggests that this is a steric
effect.
Table 4. Quantification of angular relationships in chalcogen bondsa
compound
interaction
|ϕ|, degrees
|θ|, degrees
1
2
n/a
n/a
16
18
n/a
n/a
NC‒Se···I⁻
NC‒Se···Br⁻
NC‒Se···Cl⁻
NC‒Se···I⁻
NC‒Se···I⁻
24
26
25
22
21
5.02
5.65
5.64
8.10
9.13
1⸱ (Bu4N)I
1⸱ (Bu4N)Br
1⸱ (Bu4N)Cl
2⸱ (Bu4N)I
Preparation of benzylic selenocyanate onium halide cocrystals
Benzene selenocyanates (1 and 2) and tetrabutyl ammonium
halides (iodide, bromide, and chloride) were dissolved separately in
acetone (2 equivalents of onium halides for ChB donor 1 and 4
equivalents of onium halides for ChB donor 2). The two solutions
were mixed in a small borosilicate glass vial which was placed in a
larger vial containing diethyl ether as a second less efficient solvent
and the system was sealed. Ether was allowed to diffuse until
crystals were formed. See also Table S.1 for additional conditions.
a. See Fig. 6 for definitions of the angles.
Conclusions
In summary, we have demonstrated the strong aptitude of benzylic
selenocyanates for the recognition of onium halides in the solid
state and in solution. Single-crystal X-ray diffraction shows that the
benzylic selenocyanate derivatives can adapt their conformations to
bind halide anions. Anion binding activity has been established
qualitatively in solution via 13C and 77Se NMR spectroscopy. Taken
together with other recent literature reports, 16 one may speculate
that benzylic selenocyanates may evolve into so-called ‘iconic’ ChB
donors, in parallel with the iodoperfluorobenzenes which are
widely used as iconic XB donors.
Powder X-ray studies
Crystalline powdered pure benzene selenocyanates, onium halides,
and cocrystals were individually packed in an aluminium sample
holder and data sets were collected on a Rigaku Ultima IV powder
diffractometer at 293 K (± 2) (CuKα1 radiation with a wavelength of
λ= 1.54056 Å). The measurements were carried out in focused
beam geometry with a step–scan technique in 2θ range of 5–50°.
Data were acquired by scintillation counter detector in continuous
scanning mode with a step size of 0.02°.
Experimental
Single crystal X-ray studies
Synthesis of benzylic selenocyanate 1: A solution of potassium
selenocyanate (0.8 g, 5.4 mmol, 2.7 eq) in anhydrous DMF (15 mL)
was added dropwise over a period of 30 min to a solution of α, α′-
The crystals were mounted on glass fibres with glue prior to data
collection. Crystals were cooled to 200 ± 2 K. The data were
collected on a Bruker AXS diffractometer equipped with MoKα
radiation (wavelength of λ= 0.7103 Å) with an APEX II CCD detector.
The raw data collection and processing were performed with the
Bruker APEX II software package. Structure solution and the
refinement details are provided in ESI S.3.
dibromo-p-xylene (0.5 g, 1.89 mmol,
1 eq) under an argon
atmosphere. Upon stirring, the solution gets cloudy. The reaction
was monitored by thin layer chromatography (eluent petroleum
ether/ether 1/2). After completion of the reaction (typically 45
min), addition of 60 mL of warm water (40° C) precipitated an off-
white solid. Further, the solid was washed twice with 50 mL of
warm water (40° C) in an ultrasonic bath for 5 min. The solid was
Solution NMR studies
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For 77Se, experimental setup and calibrations were performed using
selenous acid (1 M solution in D2O); the chemical shift of the Se
resonance was set to 1300.1 ppm. Exactly 0.25 M solutions of ChB
11. M. E. Brezgunova, J. Lieffrig, E. Aubert, S. Dahaoui, P.
Fertey, S. Lebègue, J. Angyan, M. Fourmigué and E.
Espinosa, Cryst. Growth Des., 2013, 13, 3283-3289.
12. S. Benz, J. López-Andarias, J. Mareda, N. Sakai and S.
Matile, Angew. Chem. Int. Ed., 2017, 56, 812-815.
13. P. Wonner, L. Vogel, M. Düser, L. Gomes, F. Kniep, B.
Mallick, D. B. Werz and S. M. Huber, Angew. Chem. Int.
Ed., 2017, 56, 12009-12012.
donors (1 and 2) in DMSO-d6 were used to measure the 77Se and 13
C
NMR spectra. 13C NMR spectra were referenced using the solvent
peak as a secondary reference. The amount of added ChB acceptor
was chosen in order to form a solution containing equimolar
amounts of ChB donor and ChB acceptor atoms (ESI S.4).
14. (a) K.-H. Linke and F. Lemmer, Z. Anorg. Allg. Chem., 1966,
345, 211-216; (b) T. M. Klapötke, B. Krumm and M. Scherr,
Inorg. Chem., 2008, 47, 7025-7028.
Acknowledgements
15. A. Lari, R. Gleiter and F. Rominger, Eur. J. Org. Chem., 2009,
2267-2274.
VK, CFL, and DLB thank Dr. Bulat Gabidullin, Dr. Glenn Facey,
and Dr. Peter Pallister for technical support and useful
discussions. DLB thanks NSERC for funding. We are grateful to
an anonymous reviewer for valuable feedback.
16. (a) H.-T. Huynh, O. Jeannin and M. Fourmigué, Chem.
Commun., 2017, 53, 8467-8469; (b) O. Jeannin, H.-T.
Huynh, A. M. S. Riel and M. Fourmigué, New J. Chem.,
2018, 42, 10502-10509.
17. (a) G. E. Garrett, G. L. Gibson, R. N. Straus, D. S. Seferos and
M. S. Taylor, J. Am. Chem. Soc., 2015, 137, 4126-4133; (b)
J. Y. C. Lim, I. Marques, A. L. Thompson, K. E. Christensen,
V. Félix and P. D. Beer, J. Am. Chem. Soc., 2017, 139, 3122-
3133.
References
1. (a) G. R. Desiraju and T. Steiner, The Weak Hydrogen Bond
in Structural Chemistry and Biology; OUP: Oxford, 1999;
(b) V. Kumar, T. Pilati, G. Terraneo, G. Ciancaleoni, A.
Macchioni, G. Resnati and P. Metrangolo, Angew.Chem.
2018, 130, 1341.
18. M. Hojjatie, S. Muralidharan and H. Freiser, Tetrahedron,
1989, 45, 1611-1622.
19. S. Scheiner, Chem.Eur. J., 2016, 22, 18850-18858.
20. (a) P. A. Gale and T. Gunnlaugsson, Chem. Soc. Rev., 2010,
39, 3595-3596; (b) P. A. Gale and R. Quesada Coord.
Chem. Rev., 2006, 250, 3219-3244.
2. (a) G. Cavallo, P. Metrangolo, R. Milani, T. Pilati, A. Priimagi,
G. Resnati and G. Terraneo, Chem. Rev., 2016, 116, 2478-
2601; (b) B. Li, S-Q. Zanga, L-Y. Wang and T. C. W. Mak,
Coord. Chem. Rev., 2016, 308, 1-21; (c) K. T. Mahmudov,
M. N. Kopylovich, M. F. C. G. da Silva and A. J. L. Pombeiro,
Coord. Chem. Rev., 2017, 345, 54-72; (d) M. K. Panda, S.
Ghosh, N. Yasuda, T. Moriwaki, G. D. Mukherjee, C. M.
21. (a) N. G. White and M. J. MacLachlan, Chem. Sci., 2015,
6,
6245-6249; (b) B. Hasenknopf, J.-M. Lehn, B. O. Kneisel, G.
Baum and D. Fenske, Angew. Chem., Int. Ed., 1996, 35
,
1838-1840.
Reddy and P. Naumov, Nat. Chem., 2015, 7, 65-72.
22. (a) V. Kumar, T. Pilati, G. Terraneo, F. Meyer, P.
Metrangolo and G. Resnati, Chem. Sci., 2017, , 1801-
3. (a) D. J. Pascoe, K. B. Ling and S. L. Cockroft, J. Am. Chem.
Soc., 2017, 139, 15160-15167; (b) L. Brammer, Faraday
Discuss, 2017, 203, 485-507.
8
1810; (b) J. Viger-Gravel, S. Leclerc, I. Korobkov and D. L.
Bryce, J. Am. Chem. Soc., 2014, 136, 6929-6942; (c) P. M. J.
4. (a) Y. Zhang and W. Wang, Crystals, 2018,
8, 163;
Szell, B. Gabidullin and D. L. Bryce, Acta Cryst. B, 2017, 73
,
doi:10.3390/cryst8040163 (b) S. K. Nayak, V. Kumar, J. S
Murray, P. Politzer, G. Terraneo, T. Pilati, P. Metrangolo
and G. Resnati, CrystEngComm, 2017, 19, 4955-4959.
153-164.
23. (a) M. A. Spackman and D. Jayatilaka, CrystEngComm,
2009, 11, 19-32. (a) S. K. Wolff, D. J. Grimwood, J. J.
McKinnon, M. J. Turner, D. Jayatilaka and M. A. Spackman,
CrystalExplorer; University of Western Australia, Perth,
2007.
5. (a) S. Benz, J. Mareda, C. Besnard, N. Sakai and S. Matile,
Chem. Sci., 2017, 8, 8164-8169; (b) K. T. Mahmudov, M. N.
Kopylovich, M. F. C. Guedes da Silva and A. J. L. Pombeiro,
Dalton Trans., 2017, 46, 10121-10138.
http:///hirshfeldsurface.net/CrystalExplorer
6. L. Chen, J. Xiang, Y. Zhao and Q. Yan, J. Am. Chem. Soc.,
2018, 140, 7079−7082.
24. P. Politzer, J. S. Murray, T. Clark and G. Resnati, Phys.
Chem. Chem. Phys., 2017, 19, 32166-32178.
7. S. P. Thomas, K. Satheeshkumar, G. Mugesh and T. N. Guru
Row, Chem. Eur. J., 2015, 21, 6793-6800.
8. (a) A. F. Cozzolino, P. J. W. Elder and I. Vargas-Baca, Coord.
Chem. Rev., 2011, 255, 1426-1438; (b) A. Kremer, A.
Fermi, N. Biot, J. Wouters and D. Bonifazi, Chem. Eur. J.,
2016, 22, 5665-5675.
9. A. Mishra, C.-Q. Ma and P. Bäuerle, Chem. Rev., 2009, 109
,
1141-1276.
10. P. C. Ho, P. Szydlowski, J. Sinclair, P. J. W. Elder, J. Kubel, C.
Gendy, L. M. Lee, H. Jenkins, J. F. Britten, D. R. Morim and
I. Vargas-Baca, Nat. Commun., 2016, 7, 11299-11309.
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DOI: 10.1039/C8CE01365A
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ARTICLE
Graphical abstract
Benzylic selenocyanates are versatile anion receptors which operate in solution and
in the solid state via chalcogen bonding interactions.
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