Anion Recognition by Neutral Chalcogen Bonding Receptors: Experimental and Theoretical Investigations

Article abstract of DOI:10.1002/chem.201905786

The utilization of neutral receptors for the molecular recognition of anions based on chalcogen bonding (ChB) is an undeveloped area of host-guest chemistry. In this manuscript, the synthesis of two new families of sulfur, selenium, and tellurium-based ChB binding motifs are reported. The stability of the thiophene, selenophene, and tellurophene binding motifs has enabled the determination of the association constants for ChB halide anion binding in the polar aprotic solvent THF by ¹H, ⁷⁷Se, and ¹²⁵Te NMR experiments. Two different aromatic cores are used and one or two Ch-binding motifs are incorporated with the purpose of encapsulating the anion, offering up to two concurrent chalcogen bonds. Theoretical calculations and NMR experiments reveal that, for S and Se receptors, hydrogen-bonding interactions involving the acidic H atom adjacent to the chalcogen atom are energetically favored over the ChB interaction. However, for the tellurophene binding motif, the σ-hole interaction is competitive and more favored than the hydrogen bond.

Full text of DOI:10.1002/chem.201905786

A Journal of
Accepted Article
Title: Anion recognition by neutral chalcogen bonding receptors:
experimental and theoretical investigation
Authors: Encarnación Navarro-García, Bartomeu Galmés, María D
Velasco, Antonio Caballero, and Antonio Frontera
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Anion recognition by neutral chalcogen bonding receptors:
experimental and theoretical investigation
Encarnación Navarro-García,[a] Bartomeu Galmés,[b] María D. Velasco,[a] Antonio Frontera[b]* and
Antonio Caballero[a]*
Dedication ((optional))
Abstract: The utilization of neutral receptors for the molecular
recognition of anions based on chalcogen bonding (ChB) is an
undeveloped area of host–guest chemistry. In this manuscript, the
synthesis of two new families of sulfur, selenium and tellurium-based
ChB binding motifs are reported. The stability of the thiophene,
selenophene and tellurophene binding motifs has enabled the
determination of association constants for ChB halide anion binding
in the polar aprotic solvent THF by 1H-, 77Se- and 125Te-NMR
experiments. We have used two different aromatic cores and
incorporated one or two Ch-binding motifs with the purpose to
encapsulate the anion offering up to two concurrent chalcogen bonds.
Theoretical calculations and NMR experiments reveal that, for S and
Se receptors, hydrogen bonding interactions involving the acidic H-
atom adjacent to the chalcogen atom are energetically favored over
the ChB interaction. However, for the tellurophene binding motif, the
σ-hole interaction is competitive and more favored than the H-bond.
a IUPAC commission as “net attractive interaction between an
electrophilic region associated with a chalcogen atom in a
molecular entity and a nucleophilic region in another, or the same,
molecular entity”.[21] The ChB interaction is more directional than
hydrogen bonding (HB) and comparable to her sister halogen
bonding (XB), however the presence of two σ-holes (opposite to
both covalent bonds) confers to this interaction more possibilities
of binding and fine tuning of the σ-holes individually. Compared
to HB, both ChB and XB interactions have greater hydrophobicity
and they are less sensitive to solvent effects and pH.[22,23] The
binding strength of ChB is comparable to the ubiquitous HB and
its high directionality allows greater precision in three dimensional
spatial control. In fact, these distinctive characteristics of ChBs
have been used in crystal engineering,[24,25] pharmaceutics,[26]
catalysis,[27-29] anion transport,[30] self‐assembly processes[31] and
materials design.[32] However, studies of ChB interactions in
solution remain scarce.[33,20] For instance, Zibarev et al.[34] have
reported the association constants of dicyanotelluradiazole and
dicyanoselenadiazole with anions measured using optical
absorbance spectroscopy. Moreover, a systematic study in
solution of the ability of several benzotelluradiazole derivatives as
anionic receptor has been also reported.[35] Finally, Bryce’s group
has used benzylic selenocyanates for anion binding in the solid
state and solution, as evidenced by 13C and 77Se NMR
spectroscopy.[36]
In the solid state, several motifs have been used for the design of
supramolecular assemblies based on ChB interactions, including
benzoselenazoles/tellurazoles,[37] tellurazole N-oxides,[30] bis-
thiophenes/tellurophene,[38] etc.[39,40] However, the application of
ChB to anion recognition in solution is clearly an underdeveloped
area of host–guest chemistry.[41] However, a recent investigation
reported by Beer and collaborators have demonstrated the ability
of halogen and chalcogen bonding based receptors to recognize
anions in water.[42] The lack of progress in this area is likely due
to the chemical instability of compounds containing the heavier
chalcogen atoms, which are the ones exhibiting the most positive
σ-holes. Herein, we report the design and synthesis of several
sulfur, selenium and tellurium‐based ChB binding motifs that
allow us to analyze the association constants for ChB halide anion
binding in the polar aprotic organic solvent THF. The energetic
and geometric characteristics of the host-guest complexes have
been also studied theoretically using DFT calculations and
molecular electrostatic potential surface analysis. The influence
of the Ch-atom on the binding energies and geometries has been
also rationalized and it is found that for S-derivatives, the Ch-
bonds are not competitive compared to H-bonds whilst Se and
Te-derivatives exhibit higher tendency to form chalcogen bonding
interaction with the anionic guests.
Introduction
The hydrogen bond is undoubtedly the most important and
prevalent noncovalent interaction.[1-7] However, other elements
belonging to groups 14 to 17 of the periodic table have a similar
function.[8–13] The electron density distribution in covalently
bonded heavy atoms of groups 15 to 17 is anisotropic and
frequently presents regions of positive (σ-holes) and negative (σ-
lumps) electron density.[14–15] The location of the σ-hole is
opposite to the covalent bond and the number of σ-holes usually
coincides with the number covalent bonds formed by the main
group element.[16]
Chalcogen bonding (ChB) is a subgroup of the σ-hole family that
originates from the interaction between an electron rich atom or
group of atoms and the σ-hole of an element belonging to group
16.[17-20] In fact, chalcogen bonding has been recently defined by
[a]
Ms. Encarnación Navarro-García, Prof. Maria D. Velasco and Prof.
A. Caballero *
Departmento de Química Orgánica
Universidad de Murcia
Campus del Espinardo, 30100 Murcia, Spain
E-mail: antocaba@um.es
[b]
Mr. Bartomeu Galmés, and Prof. A. Frontera *
Department of Chemistry
Universitat de les Illes Balears
Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca, Spain
E-mail: toni.frontera@uib.es
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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We initially designed these receptors envisaging a possible
cooperativity effect from an ancillary anion–π interaction due to
the presence of the π-acidic surface, as shown in Scheme 1.
However, both experimental and theoretical results indicate that
a different binding mode operates in these systems due to the fact
that the σ-hole opposite to the most electron-withdrawing group is
more efficient (more positive electrostatic potential), as further
described below and analyzed theoretically.
Anion binding studies
The anion binding properties of Ch receptors 1–9 were evaluated
by 1H NMR spectroscopy in the presence of several anions (Cl–,
–
–
–
Br–, I–, NO3 , AcO–, H2PO4
and PF6 ) added as
tetrabutylammonium salts in CD3CN. Additionally, 77Se NMR or
125Te NMR experiments were performed in the receptor bearing
Se or Te atoms respectively.
1
The H NMR spectra of receptors 1–9 exhibit the characteristic
signals corresponding to the mono-substituted thiophene, -
selenophene, or tellurophene rings, which appears as two doublet
of doublets attributed to the Ha ( = 7.36-9.33 ppm), Hb ( = 7.37-
8.34 ppm) and one multiplet asigned to the Hc ( = 7.06-7.92 ppm)
protons. Those signals are more downfield shifted when the
molecular weight of the heteroatom increases and with the
presence of the electron-withdrawing perfluorobenzene rings. In
addition, receptors 1, 3, and 5 also showed the resonances
attributed to the monosubstituted benzene at the aromatic region
( = 7.20-7.63 ppm).
X–
X–
Ch
Ch
Ch
F5
F4
Scheme 1. Initially envisaged binding modes for the anion-complexes based on
cooperative ChB and anion–π interactions
Results and discussion
On the other hand, the 77Se NMR or 125Te NMR spectra of
receptors 3 and 5 respectively showed a singlet at (3) = 590 ppm
and  = 768 ppm while a triplet was observed in the
perfluorobenzene derivatives at (4) = 661 ppm, (6) = 919 ppm,
(8) = 660 ppm, (9) = 917 ppm.
Design and synthesis
The two families of ChB receptors used in this work are
represented in Scheme 2. The first family comprises receptors 1–
6 where only one ChB donor site is available. For this family we
have used two types of aromatic rings (phenyl and
pentafluorophenyl) to analyze the effect of their electronic nature
on the binding constants. The second family is constituted by
receptors 7-9 that are ditopic, so two concurrent ChBs can be
established upon complexation. These two families of receptors
allow us to analyze the influence of the Ch-atom on the anion-
binding ability of the receptors in addition to the effect of the
fluorination.
The Ch receptors 1–9 were synthesized via Stille coupling
reaction by treating the previously synthesized 2-(tributylstannyl)
-thiophene, -selenophene[43] or tellurophene[44] with the
corresponding iodobenzene or iodoperfluorobenzene ring in the
presence of the appropriate palladium catalysts (Scheme 2).
Receptors 1–9 were obtained in good yields and were fully
characterized using standard techniques: 1H NMR, 13C NMR and
FAB mass spectrometry (see supporting information, Figures S1
Thus, addition of the aforementioned set of anions to solutions of
the receptors 1–9 in tetrahydrofuran-d8 showed that the presence
–
–
–
of I–, NO3 , AcO–, H2PO4 and PF6 anions did not promote any
changes in their 1H NMR spectra even in a large excess On
contrary, the presence of Cl– and Br– anions promotes important
changes in their 1H NMR.
Firstly, we analyze the Cl– and Br– binding behaviour of the
monopodal receptors 1–6. The addition of an increasing amount
of Cl– and Br– anions to a solution of the receptors 1–6 in
tetrahydrofuran-d8 promotes an important and progressive
downfield shift only in the resonance attributed to the acidic H–
atom adjacent to the chalcogen atom Ha (= 0.06 – 0.14 ppm)
indicating hydrogen bonding interaction of this proton with the
anions. On the contrary, an upfield shift in the resonance of the
proton Hc was observed. The resonance of the proton Hb was
practically not modified by the presence of Cl– and Br– anions
(Figure 1a). Some important information was obtained from the
77Se NMR and 125Te NMR titration experiments. It was not
detected perturbation in the 77Se NMR of the receptor 3, bearing
the benzene ring with the addition of both Cl– (Figure 1b) or Br–
anion and therefore there are not evidences of the participation of
the selenium atom in the binding event. Importantly, the downfield
shift observed ( = 2.71 ppm) in the signal of the 125Te NMR
spectrum of the analogous receptor 5 suggests the participation
of the tellurium atom in the anion binding (Figure 1c).
The presence of the electron withdrawing pentafluorobenzene
ring in the selenophene based receptor 4 causes the activation of
the selenium atom. In contrast to the behaviour previously
observed for receptor 3, the addition of Cl– and Br– anion
promotes a downfield shift (Δδ ~ 1.2 ppm) of the triplet present in
the 77Se NMR spectrum of the receptor 4. The analogous
tellurophene based receptor 6 shows two different behaviours,
firstly, the addition of up to one equivalent of Br- or Cl- anion
promotes the downfield shift of the triplet attributed to the tellurium
to S69).
R5
I
Ch
Ch
SnBu3
I
i)
R5
1, Ch = S, R = H
2, Ch = S, R = F
3, Ch = Se, R = H
4, Ch = Se, R = F
5, Ch = Te, R = H
6, Ch = Te, R = F
F
F
F
ii)
F
F
I
F
F
Ch
Ch
7, Ch = S
8, Ch = Se
9, Ch = Te
F
Scheme 2. Synthesis of the Ch receptors 1-9. Reagents and conditions: i)
catalyst: Pd(PPh3)4 or Pd(PPh3)2Cl2. Solvents: THF, toluene or DMF, 3-72h. ii)
Pd(PPh3)4, toluene, 2-6 days.
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atom and the addition of more than one equivalent induces the
upfield shift of this signal (Figure 2a). This behaviour is consistent
with the recognition of two different anions with different binding
modes.
the proton Ha ( = 0.07-0.14 ppm) , while protons Hb and Hc
were practically not perturbed. The downfield shift observed in the
signals of the 77Se NMR and 125Te NMR spectra upon addition of
Cl– and Br– anion to the receptors 8 and 9 also suggest an
important contribution of the heteroatoms in the binding process.
As was observed in the monopodal analogue 6, two different
processes were observed upon addition of Cl- and Br- anions to
the dipodal receptor 9 (Figure 2b).
Taking into account the titration profiles obtained by the NMR
experiment, the association constants were obtained by fitting the
titration data to a 1:1 anion/receptor binding model in the
thiophene and selenophene based receptors 1–4 and 7–8 and 2:1
anion/receptor binding model in the tellurophene based receptors
6 and 9 with use of the Dynafit program[45] and are collected in
Table 1.
Table 1. Anion binding constants (Kass, M−1) of the Receptors 1–9 with Cl- and
Br- anions at 298 K in tetrahydrofuran-d8. The obtained errors are lower than
5%.
complex
1 + Cl–
1 + Br–
2 + Cl–
2 + Br–
3 + Cl–
3 + Br–
4 + Cl–
4 + Br–
5 + Cl–
5 + Br–
6 + Cl–
Kass (1H-NMR)
Kass (
77Se/125Te-NMR)
3.1
1.4
3.5
2.2
3.3
1.5
3.6
3.0
5.4
3.7
-
-
-
-
-
-
7.2
5.6
Figure 1. a) Changes in the 1H NMR of the receptor 6 with the addition of Cl-
anion. b) Changes in the 77Se NMR of the receptor 3 with the addition of Cl-
anion and c) Changes in the 125Te NMR of the receptor 5 with the addition of Cl-
anion.
14.3
8.4
K1=78
No fitting
K2=6.5
6 + Br–
K1= 20.8
K2= 1.36
K1=35.6
K2=9.2
7 + Cl–
7 + Br–
8 + Cl–
8 + Br–
9 + Cl–
5.5
3.7
5.8
4.2
-
-
7.2
4.4
Figure 2. Changes in the 125Te NMR of the receptor 6 (a) and 9 (b) with the
addition of Br- anion.
K1=51.1
K2=5.0
No fitting
9 + Br–
K1=14.0
K2=1.0
K1=12.7
K2=6.62
The same NMR titration experiments were also performed in the
dipodal receptor 7–9. The results were very similar to the obtained
for the monopodal analogues 1–6. Thus, H NMR titration of the
receptors 7–9, upon addition of Cl– and Br–, clearly indicated the
participation of the proton Ha solely in the anion-receptor binding,
as was evidenced by the downfield shift of the signal attributed to
1
The association constants calculated for the thiophene (1, 2 and
7) and selenophene (3, 4 and 8) based receptors are noticeably
lower than those obtained in tellurophene derivatives (5, 6 and 9).
On the other hand, the incorporation of pentafluorobenzene rings
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causes a slight increase in the association constants with respect
to the tetrafluorobenzene and also with the benzene derivatives.
Finally, the chloride anion shows greater affinity for the receptors
than the bromide anion.
atom adjacent to the chalcogen atom presents more positive MEP
value than that at the σ-hole of the chalcogen atom. In contrast,
for Te, the maximum MEP is located at the σ-hole. Therefore,
different binding mode can be anticipated. Second, as expected
the receptors with the pentafluorophenyl ring exhibit more positive
values of MEP both at the σ-hole and the H-atom than those with
the phenyl ring. As shown in Figure S72, the dihedral angle
between the aromatic rings is around 30º for all receptors. In this
conformation the second σ-hole at the chalcogen atom is not
accessible, as shown in Figure 3.
MEP surface analysis
From the aforementioned titrations it is clear that the H-atom
adjacent to the chalcogen atom in the five membered ring actively
participates in the binding mechanism. This strongly disagrees
with a binding mode where the anion is located over the aromatic
ring, as shown in Scheme 1, since this H-atom would be not
affected during the titrations. We have started the theoretical
analysis by computing the molecular electrostatic potential (MEP)
Therefore, for the pentafluorophenyl derivatives, we have also
computed the MEP surfaces using a perpendicular conformation
between both rings, in order to examine the influence of the C–C
surfaces of the receptors (see ESI for the computational methods). dihedral angle on the MEP values (see Figure 4).
The isosurface used for the MEP plots shown in Figures 3–6 is
0.001 a.u., which is the best estimate of the van der Waals surface.
However, for a set of receptors (1–6) we have also plotted the
MEP surfaces using two additional isosurfaces (0.002 and 0.0005
a.u.) that are represented in Figures S70 and S71 (see ESI).
Remarkably, the trends in the MEP values are the same, thus
giving reliability to the analysis commented below.
Figure 4. MEP surfaces of 2 (a) 4 (b) and 6 (c) monopodal receptors using a
C–C rotational angle of 90⁰. Isosurface 0.001 a.u.
This conformation is expected for the complexes where the anion
interacts with the receptor using a combination of ChB and anion–
π interactions. Interestingly, the σ-hole that points toward the
aromatic ring is hidden in S and Se receptors 2 and 4. Moreover,
the maximum of MEP is located at the H-atom that is adjacent to
the Ch-atom. The MEP analysis also shows that the Te derivative
6 presents similar values at both σ-holes (see Figure 4c). Overall,
the MEP surface analysis indicates that the anion will have a
preference for the interaction with both the H-atom and the
chalcogen’s σ-hole simultaneously rather than the anion–π and
ChB combination, especially taking into consideration that, at the
PBE0-D3(THF)/def2-TZVPP level of theory, the perpendicular
conformation is 1.2 kcal/mol less stable than the minimum in all
three receptors. Moreover, this MEP surface analysis strongly
agrees with the NMR titrations commented above, since the H-
Figure 3. MEP surfaces of 1 (a) 3 (c) and 5 (e) monopodal phenyl receptors
and 2 (b) 4 (d) and 6 (f) monopodal pentafluorophenyl receptors. The MEP
values at selected points of the surfaces are indicated in kcal/mol. Isosurface
atom in alpha to the Ch-atom is strongly affected by the addition
of the anion and, for S and Se receptors, the MEP is maximum at
these H-atoms. Moreover, for the Te receptor the MEP maximum
is located at the σ-hole, also in agreement with the 125Te NMR
experiments shown in Figure 2.
0.001 a.u.
For the dipodal receptors 7–9 (see Figure S73 for the optimized
geometries) we have also computed the MEP surfaces using two
conformations: (i) the global minima (Figure 5) that exhibit
dihedral angles between the rings ranging 15–17º and, (ii) fixed
The optimized structures of the monopodal receptors 1–6 are
shown in Figure S72 (ESI) and the MEP surfaces in Figure 3.
Some interesting issues can be deduced from the MEP surface
plots. First, for receptors with S and Se, the MEP values at the H-
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conformations (see Figure 6) with dihedral angles fixed at 90º and
with both five membered rings in a syn arrangement (see Scheme
1 right). In this conformation the anion would interact with the
receptor by means of a combination of ChB and anion–π
interactions. The MEP surfaces gathered in Figures 5 and 6 show
that the trends are similar to those previously described for the
monopodal receptors.
experimental 1H-NMR results commented above evidence that
the H-atom participates in the binding mechanism, that rule out
the formation of the combined anion–π/ChB complex. This aspect
is further studied below.
The σ-hole is imperceptible for the S-derivative in any of both
conformations and the positive MEP value at the adjacent H-atom
is significantly larger. For Se, the σ-hole is visible but also smaller
than that at the H-atom. Finally, the Te derivative presents the
largest and most intense σ-hole and it is the only one where the
MEP value at the H-atom is smaller than that at the Ch-atom. It is
worth emphasizing that the Kass values of Te-complexes with Cl–
and Br– are larger for the monopodal than dipodal receptors (see
Table 1), in line with the higher value of MEP at the σ-hole of the
monopodal receptor. This is likely due the stronger electron
withdrawing ability of the C6F5 group compared to the C6F4 one.
Figure 6. MEP surfaces of S, (a) Se (b) and Te (c) dipodal receptors. The MEP
values at selected points are indicated in kcal/mol. Isosurface 0.001 a.u.
Geometric and energetic analysis
We have optimized the geometries and calculated the binding
energies of chloride and bromide complexes with receptors 1–9,
(see ESI for details). Figure 7 shows the geometries for the
complexes of the first family of receptors interacting with Cl– anion
and those involving bromide are included in the ESI (Figure S74).
It can be observed that all Cl– complexes exhibit very modest
interaction energies, in agreement with the small association
constants. Interestingly, the H-bonding distance increases and
the Ch-bond distance decreases on going from the lighter to the
heavier chalcogen atom, in good agreement with the MEP surface
analysis. That is, the relative importance of the σ-hole interaction
increases on going from S to Te. Moreover, the binding energies
obtained for the fluorinated receptors are larger in absolute value
than those corresponding to the non-fluorinated ones, also in
agreement with the MEP analysis and experimental association
constants (see Table 1).
Figure 5. MEP surfaces of 7 (a) 8 (b) and 9 (c) dipodal receptors. The MEP
values at selected points of the surfaces are indicated in kcal/mol. Isosurface
0.001 a.u.
It is worth mentioning that for the Te receptor in the perpendicular
conformation, the MEP surface analysis shows that the most
favored binding mode should be the anion–π and two concurrent
ChBs, since the π-hole is accessible and of similar magnitude to
that pointing to the exterior of the cavity. Even though the energy
cost for rotating both tellurophene rings in THF is 3.3 kcal/mol,
this binding mode should be competitive. However, the
Figure 8 shows some representative complexes of the second
family of receptors interacting with Cl– and Br– anions (the rest is
included in the ESI, Figure S75). It can be observed that the
complexes where the anion interacts via HB and ChB interactions
(Figure 8a,b) are energetically favored with respect to those
where the anion is located inside the cavity, which is forming two
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concurrent ChBs and the ancillary anion–π interaction (Figure
8c,d).
Finally, we have also explored the possibility of the formation of
complexes with 2:1 anion/receptor stroichiometry for the
complexation of bromide with receptors 9, since the fitting of the
experimental data suggests the incorporation of two anions in the
tellurophene based receptor. Agreeably, we have found two
possible binding modes corresponding to 2:1 complex that are
represented in Figure 9. One of both is symmetric and each Br
forms concurrent hydrogen and chalcogen bonds. The other one
is energetically more favored and each Br– interacts with the
receptors in a different manner. That is, one Br– is bonded
combining Ch-bonding and anion–π interaction and the other one
simply interacts with the tellurophene establishing a H-bonding
interaction with Ha.
Figure 7. PBE0-D3/def2-TZVPP optimized geometries of monopodal
complexes with Cl–. Distances in Å. BSSE-corrected energies in THF.
Figure 9. (a,b) PBE0-D3/def2-TZVPP optimized geometries for two different
binding modes for receptor 9 interacting with Br–. Distances in Å and BSSE-
corrected energies in THF.
In fact, this binding mode is not favored for Br– exhibiting a positive
interaction energy, evidencing that the receptor is not able to
desolvate the anion. It can be observed that the ChB distances
are quite longer in these complexes, thus explaining the less
favorable binding energies. Moreover, in these ChBs/anion–π
complexes, there is a deformation of the receptor since the
exocyclic C–C bonds are bent toward the anion in an attempt to
reinforce the ChBs (see Figure 8c,d). It is interesting to note that
the binding energies of dipodal receptor 9·(Ch = Te, fluorinated)
with Cl– and Br– are weaker than those obtained for monopodal
receptor 6 (Ch = Te, R = F) in good agreement with the
experimental association constants (see Table 1).
Conclusions
In conclusion, we have prepared two families of sulfur, selenium
and tellurium-based ChB-donor motif capable of binding chloride
and bromide in THF. These families of receptors have allowed us
to analyze the effect of the chalcogen atom on the association
constants and also competition between H-bonding and
chalcogen bonding interactions. For the S and Se the HB
interactions are quite competitive whilst for tellurium the ChB
dominates. The comprehensive DFT study and especially the
MEP surface analysis allowed us to rationalize the experimental
findings since the 1H, 77Se and 125Te-NMR shifts agree well with
the MEP values at the σ-holes in H and Ch atoms of thiophene,
selenophene and tellurophene rings. These findings are expected
to be useful in the nascent field of molecular recognition of anions
based on neutral ChB donors, especially for those researchers in
the field working on the integration of ChB donor motifs into
receptors for molecular recognition and catalysis. Finally, future
directions of this work are the utilization of oxoanions, the analysis
of atropoisomerism in the receptors and to block the acidic H-
atom with appropriate alpha substituents on the heterocycles.
Figure 8. PBE0-D3/def2-TZVPP optimized geometries for two different binding
modes in dipodal complexes with Cl– (a,c) and Br– (b,d). Distances in Å. BSSE-
corrected energies in THF.
Acknowledgements
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Galmés, A. Juan-Bals, A. Frontera, G. Resnati, Chem. Eur. J. 2020, 26,
DOI: 10.1002/chem.201905498
We thank the MICIU/AEI (project CTQ2017-85821-R, RED2018-
102331-T and CTQ2017-86775-P FEDER funds) and the
Fundación Séneca Región de Murcia (CARM) (project
20819/PI/18) for financial support. We thank the CTI (UIB) for
computational facilities.
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Keywords: Chalcogen bonding • Supramolecular Chemistry •
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10.1002/chem.201905786
Chemistry - A European Journal
FULL PAPER
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FULL PAPER
The synthesis of three new families of
sulfur, selenium and tellurium-based
ChB binding motifs is reported herein.
The stability of the chalcophene
E. Navarro-García,[a] B. Galmés,[b] M. D.
Velasco[a], A. Frontera[b],* and A.
Caballero[a],
*
Page No. – Page No.
binding motifs has enabled the
determination of association constants
for ChB halide anion binding in the
polar aprotic solvent THF by 1H-, 77Se-
and 125Te-NRM experiments.
Anion recognition by neutral
chalcogen bonding receptors:
experimental and theoretical
investigation
This article is protected by copyright. All rights reserved.