Controlling π-πInteractions through coordination bond formation: Assembly of 1-d chains of acac-Based coordination compounds

Article abstract of DOI:10.1021/acs.cgd.1c00083

We present a new approach for the construction of 1-D chains of acac-based copper coordination compounds assembled through π-πaromatic interactions. We use 3-(phenylethynyl)pyridine derivatives as ligands that can establish aromatic interactions to intermolecularly bind the coordination compounds. The crystal networks of the free pyridines show that there is no control over aromatic interactions, since different interactions are present. On the other hand, the supramolecular behavior of the coordination compounds is very homogeneous since, in all of the crystal networks, the intended 1-D chains are present. Given the polarization of the aromatic rings due to coordination, reflected in the calculated molecular electrostatic potential maps, we gain control over the ?-πinteraction geometry, promoting a head to tail interaction between the coordinated 3-(phenylethynyl)pyridines. This strategy to constructing 1-D chains is reliable and reproducible; thus, these types of π-πaromatic interactions are a useful supramolecular tool to control the molecular assembly in the solid state.

Full text of DOI:10.1021/acs.cgd.1c00083

pubs.acs.org/crystal
Article
Controlling π−π Interactions through Coordination Bond Formation:
Assembly of 1‑D Chains of acac-Based Coordination Compounds
́
Rafael León-Zárate* and Jesus Valdés-Martínez*
Cite This: Cryst. Growth Des. 2021, 21, 3756−3769
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: We present a new approach for the construction of
1-D chains of acac-based copper coordination compounds
assembled through π−π aromatic interactions. We use 3-
(phenylethynyl)pyridine derivatives as ligands that can establish
aromatic interactions to intermolecularly bind the coordination
compounds. The crystal networks of the free pyridines show that
there is no control over aromatic interactions, since different
interactions are present. On the other hand, the supramolecular
behavior of the coordination compounds is very homogeneous
since, in all of the crystal networks, the intended 1-D chains are
present. Given the polarization of the aromatic rings due to
coordination, reflected in the calculated molecular electrostatic
potential maps, we gain control over the π−π interaction geometry, promoting a head to tail interaction between the coordinated 3-
(phenylethynyl)pyridines. This strategy to constructing 1-D chains is reliable and reproducible; thus, these types of π−π aromatic
interactions are a useful supramolecular tool to control the molecular assembly in the solid state.
through aromatic interactions (Figure 1). It was suggested that
this kind of aromatic interaction can be useful in the synthesis of
INTRODUCTION
■
Understanding and controlling intermolecular interactions are
fundamental in the design and synthesis of new crystalline
materials. Hydrogen1,2 and halogen3−6 bonds have been studied
and used extensively for this process due to their strength and
directionality; on the other hand, aromatic interactions are a less
explored and understood tool, and so, they have been used in a
smaller proportion. Control over aromatic interactions in crystal
networks has been carried out through a variety of approaches.
In his seminal paper, Grubbs used phenyl−perfluorophenyl
interactions to organize diphenylbutadiyne derivatives in crystal
networks for a subsequent solid-state reaction.7 This approach
has been widely used ever since; the MacGillivray8 and Sonoda9
groups used it to organize alkene derivatives in the solid state
Figure 1. Aromatic interactions between Hg(II) coordination
compounds derived from N-naphthalenyl(pyrazine)-2-carboxamide.12
and subsequently carry out a [2 + 2] photocyclodimerization,
10
́
́
and Valdes-Martinez along with his group reported the
synthesis of a designed asymmetric crystal network using
geometric considerations and this favored interaction.
new crystal networks. However, the phenomenon that allows its
presence was not explored; instead, other interactions seem to
be more critical in the construction of those crystal lattices. A
careful examination of the reported crystal networks shows that
there are Cl···Hg, Br···Hg, and O···Hg interactions that can be
responsible for bringing together the aromatic rings (Figure 2).
Bosch synthesized a crystal network using a different
approach; he used aromatic interactions between N-methylpyr-
idinium and phenyl rings.11 This aromatic interaction is present
even though the N-methylpyridinium moiety has a stronger
attraction to the triflate anion present in the crystal network.
Khavasi reported that Hg(II) coordination compounds
derived from N-naphthalenyl(pyrazine)-2-carboxamide organ-
ize in the crystal network through aromatic interactions;12 this
kind of ligand has three aromatic rings, and one of them
(pyrazine ring) forms a coordination bond with the Hg(II)
cation. The coordination compounds organize in the solid state
Received: January 22, 2021
Revised: May 4, 2021
Published: June 3, 2021
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769
© 2021 American Chemical Society
3756

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 2. Cl···Hg and O···Hg interactions in a crystal network of a Hg(II) coordination compound.12
Figure 3. Aromatic interactions between acetylacetonate-derived coordination compounds.17
Khavasi reported these long coordination bonds for similar
compounds,13−15 and Puddephatt and his group reported a
series of Hg(II) coordination compounds which reveal that long
coordination bonds direct the assembly of coordination
polymers.16 Therefore, the closeness of aromatic rings in the
crystal networks is not necessarily due to an attractive
interaction between them.
[MII(acac)2] leaving two coordination sites avaliable in a trans
geometry to obtain [MII(acac)2(L)2] complexes. These charge-
balancing anions will not disrupt the intended supramolecular
connectivity.
We decided to use Cu(II) cations as metal centers for their
interesting magnetic properties.37−39 Their usually unpredict-
able coordination geometry can be controlled very well through
acac-based ligands26,27,29,31,40,41 to give hexacoordinated and
octahedral complexes.
To complete the coordination sphere, we used
(phenylethynyl)pyridine derivatives as ligands for several
reasons. They contain two aromatic rings (phenyl (Ar) and
pyridine (Py)) separated by an alkyne group; due to the alkyne,
the distance between rings is large enough to minimize steric
crowding if the pyridine fragment coordinates to the bulky
[MII(acac)2] unit. The phenyl ring lacks functionalities capable
of establishing strong hydrogen bonds (Figure 4); instead, it is
para-substituted (H, F, Cl, Br, I) to see if there is a relationship
between the aromatic interactions formed and the substituent.
We used pyridine ligands substituted in the meta position; i.e.,
3-(phenylethynyl)pyridine derivatives. Pyridines substituted in
the para positions would have other aromatic interactions; i.e.,
halogen−π and acetylene−π, because of the steric hindrance
between the halogen atom and the acac derivative ligands, as
shown in Figure 3. With ortho-substituted pyridines, the steric
hindrance with acac ligands would not allow the presence of
aromatic interactions as designed for the construction of 1-D
chains because the aromatic rings would not be close enough to
interact in a head to tail fashion (Figure 5).
̈
On the other hand, Aakeroy and his group attempted to
synthesize crystal networks of coordination compounds organ-
ized through halogen bonds.17 Even though they were
unsuccessful, among their reported crystal structures there was
one in which the coordination compounds are held together by
aromatic interactions: phenyl−pyridine and bromine−pyridine
(Figure 3). Although this interaction geometry was not the goal
of that research, it is an example of the usefulness of aromatic
interactions as organizing tools in the solid state.
In addition, several authors have reported the synthesis of
extended metal-containing crystal networks through metal−
organic frameworks18−21 and coordination polymers22−24 and,
in a smaller proportion, through the use of intermolecular
interactions.
Particularly, the design and synthesis of 1-D chains of acac-
based coordination compounds (acac = acetylacetonate) has
been achieved with the use of hydrogen25−31 and halogen32−36
bonds, but its synthesis purposely made exclusively through π−π
aromatic interactions has not been done yet, to the best of our
knowledge.
RATIONALE
■
This paper reports the crystal structures of three
(phenylethynyl)pyridines (ligands) and seven coordination
compounds. We studied the crystal networks of the ligands
and coordination compounds to evaluate the effect of
coordination bond formation on the intermolecular aromatic
interactions between ligands.
We attempt to fill this gap and design 1-D chains of coordination
compounds organized through π−π aromatic interactions. We
decided to use [M(acac)2] units and (phenylethynyl)pyridines
as ligands to obtain trans-[M(acac)2(L)2] coordination
compounds and use them as building blocks. The use of acac-
based coordination compounds has various advantages, as noted
by Valdes-Martinez, Aakeroy, and others:33 i.e., acac-based
ligands act as bidentate chelates and with hexacoordinated
M(II) cations form the neutral square-planar compounds
25
30
́
EXPERIMENTAL SECTION
Chemicals. Iodobenzene (98%), 4-fluorobenzene (99%), 4-
chloroiodobenzene (99%), 4-bromoiodobenzene (98%), 1,4-diiodo-
́
̈
■
3757
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
chromatography column with a mixture of hexane and ethyl acetate
(9/1) as eluent.
3-(Phenylethynyl)pyridine (1). Iodobenzene (0.40 mL, 3.6 mmol),
PdCl2(PPh3)2 (0.087 g), CuI (0.031 g), and THF (10 mL) were placed
in a round-bottom flask under a nitrogen atmosphere followed by the
addition of 3-ethynylpyridine (0.301 g, 2.92 mmol) dissolved in DIPA
(2 mL). The product was isolated as an off-white solid (0.411 g, 78%,
mp 47−48 °C). FT-IR (ATR): νmax 2219 (CC) cm−1. 1H NMR (300
MHz, CDCl3): δ 8.77 (s, 1H), 8.54 (dd, J = 4.89, 1.68 Hz, 1H), 7.80 (dt,
J = 7.89, 1.93 Hz, 1H), 7.55 (m, 2H), 7.35 (m, 3H) and 7.26 (m, 1H)
ppm. 13C NMR (75 MHz, CDCl3): δ 152.35 (C2), 148.65 (C6),
138.50 (C4), 131.78 (C10, C14), 128.90 (C12), 128.54 (C11, C13),
123.12 (C5), 120.56 (C9), 92.75 (C8) and 86.05 (C7) ppm. HRMS
(DART): m/z [C13H10N]+ calculated 180.08132, found 180.08138.
3-((4-Fluorophenyl)ethynyl)pyridine (2). 4-Fluoroiodobenzene
(0.312 g, 1.41 mmol), PdCl2(PPh3)2 (0.035 g), CuI (0.013 g), and
THF (10 mL) were placed in a round-bottom flask under a nitrogen
atmosphere followed by the addition of 3-ethynylpyridine (0.162 g,
1.57 mmol) dissolved in DIPA (2 mL). The product was isolated as an
off-white solid (0.183 g, 59%, mp 87−89 °C). FT-IR (ATR): νmax 2216
(CC) cm−1. 1H NMR (300 MHz, CDCl3): δ 8.75 (s, 1H), 8.55 (dd, J
= 4.97, 1.69 Hz, 1H), 7.79 (dt, J = 7.92, 1.92 Hz, 1H), 7.52 (dd, J = 8.81,
5.33 Hz, 2H), 7.26 (m, 1H) and 7.06 (t, J = 8.68 Hz, 2H) ppm. 13C
NMR (75 MHz, CDCl3): δ 162.90 (d, J = 250.28 Hz, C12), 152.31
(C2), 148.74 (C6), 138.47 (C4), 133.74 (d, J = 8.42 Hz, C10, C14),
123.15 (C5), 120.41 (C3), 118.74 (C9), 115.91 (d, J = 22.14 Hz, C11,
C13), 91.66 (C8) and 85.78 (C7) ppm. HRMS (DART): m/z
[C13H9NF]+ calculated 198.07190, found 198.07169.
3-((4-Chlorophenyl)ethynyl)pyridine (3). 4-Chloroiodobenzene
(0.462 g, 1.94 mmol), PdCl2(PPh3)2 (0.060 g), CuI (0.019 g), and
THF (10 mL) were placed in a round-bottom flask under a nitrogen
atmosphere followed by the addition of 3-ethynylpyridine (0.237 g,
2.30 mmol) dissolved in DIPA (2 mL). The product was isolated as an
off-white solid (0.364 g, 88%, mp 84−86 °C) that was recrystallized
from toluene. FT-IR (ATR): νmax 2214 (CC) cm−1. 1H NMR (300
MHz, CDCl3): δ 8.75 (s, 1H), 8.54 (d, J = 3.28 Hz, 1H), 7.78 (dt, J =
7.93, 1.87 Hz, 1H), 7.45 (d, J = 8.50 Hz, 2H), 7.32 (d, J = 8.50 Hz, 2H)
and 7.27 (dd, J = 8.03, 4.76 Hz, 1H). 13C NMR (75 MHz, CDCl3):
152.31 (C2), 148.84 (C6), 138.49 (C4), 134.98 (C14), 132.98 (C10,
Figure 4. Reactants used for the synthesis of metal-containing 1-D
chains.
benzene (99%), 3-ethynylpyridine (98%), PdCl2(PPh3)2 (99%), CuI
(98%), copper(II) trifluoroacetylacetonate (Cu(tacac)2, 97%), copper-
(II) hexafluoroacetylacetonate (Cu(hacac)2, hydrate), diisopropyl-
amine (DIPA, 98%), and tetrahydrofuran (THF, 99%) were purchased
from commercial sources. All chemicals and solvents were used as
received.
Synthesis. General Procedure for the Synthesis of 3-
(Phenylethynyl)pyridine Derivatives. 4-X-iodobenzene (X = H, F,
Cl, Br, I; 1.2 equiv), PdCl2(PPh3)2 (5 mol %), CuI (5 mol %), and THF
(10 mL) were placed in a round-bottom flask under a nitrogen
atmosphere followed by the addition of 3-ethynylpyridine (1 equiv)
dissolved in DIPA (2 mL); the reaction was carried out at room
temperature overnight42 (Scheme 1). The reaction mixture was diluted
with CH2Cl2 (50 mL) and washed with K2CO3-saturated water (3 × 50
mL). The organic layer was separated and filtered over anhydrous
Na2SO4. The crude product was purified using an alumina
Figure 5. Possible 1-D chains of acac-based coordination compounds binding through π−π aromatic interactions. Pyridines substituted in ortho and
para positions have steric hindrance.
3758
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
a
,
Scheme 1. Synthesis of 3-(Phenylethynyl)pyridine and Its Derivatives42
a
The numbering scheme is the same for all of the free and coordinated pyridines.
Scheme 2. Synthesis of acac-Based Coordination Compounds Derived from 3-(Phenylethynyl)pyridines
C14), 128.91 (C11, C13), 123.16 (C5), 121.10 (C9) and 120.25 (C3)
ppm. HRMS (DART) m/z [C13H9NCl]+ calculated 214.04235, found
214.04130 m/z.
were obtained by slow evaporation of the solvent after a few days (mp
137−138 °C). FT-IR (ATR): νmax 1651 (C−O) and 2231 (CC)
cm−1.
3-((4-Bromophenyl)ethynyl)pyridine (4). 4-Bromoiodobenzene
(0.618 g, 2.18 mmol), PdCl2(PPh3)2 (0.073 g), CuI (0.021 g) and
THF (10 mL) were placed in a round-bottom flask under a nitrogen
atmosphere followed by the addition of 3-ethynylpyridine (0.204 g,
1.98 mmol) dissolved in DIPA (2 mL). The product was isolated as an
off-white solid (0.344 g, 67%, mp 92−94 °C) which was recrystallized
from toluene. FT-IR (ATR): νmax 2218 (CC) cm−1. 1H NMR (300
MHz, CDCl3): δ 8.75 (m, 1H), 8.55 (dd, J = 4.94, 1.64 Hz, 1H), 7.79
(dt, J = 7.90, 1.92 Hz, 1H), 7.50 (d, J = 8.47 Hz, 2H), 7.40 (d, J = 8.51
Hz, 2H) and 7.28 (m, 1H). 13C NMR (75 MHz, CDCl3): δ 152.35
(C2), 148.91 (C6), 138.54 (C4), 133.21 (C10, C14), 131.88 (C11,
C13), 123.28 (C9), 123.20 (C5), 121.60 (C9), 120.27 (C3), 91.68
(C8) and 81.17 (C7) ppm. HRMS (DART): m/z [C13H9NBr]+
calculated 257.99184, found 257.99110.
3-((4-Iodophenyl)ethynyl)pyridine (5). 1,4-Diiodobenzene (1.670
g, 5.06 mmol), PdCl2(PPh3)2 (0.164 g), CuI (0.089 g) and THF (10
mL) were placed in a round-bottom flask under a nitrogen atmosphere
followed by the addition of 3-ethynylpyridine (0.498 g, 4.83 mmol)
dissolved in DIPA (2 mL). The product was isolated as an off-white
solid (0.548 g, 37%, mp 133−135 °C) which was recrystallized from
toluene. FT-IR (ATR): νmax 2214 (CC) cm−1. 1H NMR (300 MHz,
CDCl3): δ 8.77 (d, J = 1.55 Hz, 1H), 8.57 (dd, J = 4.93, 1.70 Hz, 1H),
7.81 (dt, J = 7.93, 1.92 Hz, 1H), 7.72 (d, J = 8.36 Hz, 2H) and 7.27 (m,
3H) ppm. 13C NMR (75 MHz, CDCl3): δ 152.35 (C2), 148.92 (C6),
138.54 (C4), 137.78 (C10, C14), 133.24 (C11, C13), 123.19 (C5),
122.15 (C9), 120.27 (C3), 95.00 (C14), 91.81 (C8) and 87.45 (C7)
ppm. HRMS (DART): m/z [C13H9NI]+ calculated 305.97797, found
305.97758.
Cu(tacac)2(3-((4-fluorophenyl)ethynyl)pyridine)2 (7). Cu(tacac)2
(0.049 g, 0.14 mmol) and 2 (0.054 g, 0.27 mmol) were used. The
product dissolved in CH2Cl2 was placed in a screw-cap vial, and green
crystals were obtained by slow evaporation of the solvent after a few
days (mp 180−182 °C). FT-IR (ATR): νmax 1620 (C−O) and 2226
(CC) cm−1.
Cu(tacac)2(3-((4-chlorophenyl)ethynyl)pyridine)2 (8). Cu(tacac)2
(0.043 g, 0.12 mmol) and 3 (0.050 g, 0.23 mmol) were used. The
product dissolved in CH2Cl2 was placed in a screw-cap vial, and green
crystals were obtained by slow evaporation of the solvent after a few
days (mp 133−135 °C). FT-IR (ATR): νmax 1619 (C−O) and 2225
(CC) cm−1.
Cu(tacac)2(3-((4-bromophenyl)ethynyl)pyridine)2 (9). Cu(tacac)2
(0.051 g, 0.14 mmol) and 4 (0.071 g, 0.27 mmol) were used. The
product dissolved in CH2Cl2 was placed in a screw-cap vial, and green
crystals were obtained by slow evaporation of the solvent after a few
days (mp 171−172 °C). FT-IR (ATR): νmax 1619 (C−O) and 2224
(CC) cm−1.
Cu(hacac)2(3-((4-chlorophenyl)ethynyl)pyridine)2 (10). Cu-
(hacac)2 hydrate (0.059 g, 0.12 mmol anhydrous basis) and 3 (0.052
g, 0.24 mmol) were used. The product dissolved in CH2Cl2 was placed
in a screw-cap vial, and green crystals were obtained by slow
evaporation of the solvent after a few days (mp 177−178 °C). FT-IR
(ATR): νmax 1649 (C−O) and 2229 (CC) cm−1.
Cu(hacac)2(3-((4-bromophenyl)ethynyl)pyridine)2 (11). Cu-
(hacac)2 hydrate (0.045 g, 0.09 mmol anhydrous basis) and 4 (0.049
g, 0.19 mmol) were used. The product dissolved in CH2Cl2 was placed
in a screw-cap vial, and green crystals were obtained by slow
evaporation of the solvent after a few days (mp 171−172 °C). FT-IR
(ATR): νmax 1651 (C−O) and 2227 (CC) cm−1.
General Procedure for the Synthesis of Coordination
Compounds. The desired copper(II) salt (1 equiv) and 3-
(phenylethynyl)pyridine derivative (2 equiv) were placed in an agate
mortar, and drops of CH2Cl2 were added to assist in grinding (liquid-
assisted grinding, LAG) (Scheme 2). The grinding was stopped when a
change of color was observed. The products were dissolved in CH2Cl2,
and crystals were obtained by slow evaporation of the solvent after few
days.
Cu(hacac)2(3-((4-iodophenyl)ethynyl)pyridine)2 (12). Cu(hacac)2
hydrate (0.052 g, 0.10 mmol anhydrous basis) and 5 (0.063 g, 0.21
mmol) were used. The product dissolved in CH2Cl2 was placed in a
screw-cap vial, and green crystals were obtained by slow evaporation of
the solvent after a few days (mp 145−146 °C). FT-IR (ATR): νmax 1650
(C−O) and 2225 (CC) cm−1.
Cu(tacac)2(3-(phenylethynyl)pyridine)2 (6). Cu(tacac)2 (0.051 g,
0.14 mmol) and 1 (0.050 g, 0.28 mmol) were used. The product
dissolved in CH2Cl2 was placed in a screw-cap vial, and green crystals
The mixtures corresponding to Cu(tacac)2 + 5, Cu(hacac)2 + 1 and
Cu(hacac)2 + 2 did not produce the expected products: i.e., after the
3759
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 6. Reduced density gradient isosurface (s = 0.5) of the Cl···Cl interaction and its spike (blue dots) highlighted from all of the intramolecular
interactions in the unit cell (black dots) in the plot.
Figure 7. Halogen contacts and bonds in crystal networks of 3−5.
synthesis procedure we observed the segregated reactants in the bottom
of the screw-cap vials after slow evaporation of the CH2Cl2 solvent.
X-ray Crystallography. Single crystals of the compounds were
mounted in a random orientation on the tip of a glass fiber using epoxy
resin. Crystallographic data were collected using monochromatic Mo
Kα (λ = 0.71073 Å) radiation at 293(2) K for compounds 3−9 and
150(2) K for compunds 10−12 on a Bruker D8 Venture 208039-1 κ-
geometry diffractometer. Data were collected and refined using APEX2
v2014.1-1 for 3 and 5, APEX3 v2016.1 for 4 and 10, and APEX3
v2018.1−043 for 6−9, 11, and 12 and reduced with SAINT v8.34A for
3, 5, and 11, SAINT v8.37A for 4 and 10, and SAINT v8.38A44 for 6−9
and 12. Structures were solved by direct methods using SHELXS-2012
for 8 and 12, SHELXS-201445 for 4 and 10, SHELXT 2014 for 3 and 5,
and SHELXT 2014/546 for 6, 7, 9, and 11. All crystals were refined
against F2 by full-matrix least squares with SHELXL-2018/3.45 In all
cases, the non-hydrogen atoms were located in a difference electron
density map and refined anisotropically. Hydrogen atoms were
included at geometrically idealized positions and refined with the
rigid model. Table S1 in the Supporting Information provides
crystallographic details. Geometric values and figures were obtained
with OLEX2.47
For 3, the pyridine fragment of the 3-((4-chlorophenyl)ethynyl)-
pyridine is disordered in two positions; the first position has a chemical
occupancy equal to 57%.
For 4, the asymmetric unit has two crystallographically independent
3-((4-bromophenyl)ethynyl)pyridine molecules. For the computa-
tional procedure the geometry of one molecule was chosen arbitrarily,
since they are similar.
For 6−12, the Cu(II) cation of the coordination compound is in a
special position (inversion center). The asymmetric units contain half
of the coordination compound.
computational procedures and geometric measurements we used the
molecular structure with higher chemical occupancy.
Figures S21−S23 and S27 in the Supporting Information provide the
atom-numbering scheme of all crystallized compounds.
Computational Procedures. Geometries of single organic
molecules and coordination compounds were extracted from
experimental crystallographic data (3−12). For all molecules, hydrogen
atom positions were optimized while the other atoms were fixed for the
calculation of electron structures in Gaussian 1648 at the M062X/
def2TZVP41 level of theory with empirical dispersion (GD3),30,31 and
the results were visualized in GaussView 6.49 The molecular
electrostatic potential (MEP) at a specific point on the 0.002 au
isodensity surface is given by the potential energy (kJ/mol) that a
positive charge would experience at that point (on the surface, negative
values are shown in red and positive values in blue). MEP mapped on
the electron density surface was obtained with the cubegen utility of
Gaussian on a fine rectangular grid with 12 points/bohr.
To characterize the intramolecular interactions, AIM50,51 and
NCIplot52,53 analyses of the wave functions obtained in Gaussian
1648 were carried out with Multiwfn 3.754 for compounds 6, 7, and 12
and the results were visualized in VMD 1.9.4a38.55
To characterize the intermolecular interactions, the NCIplot56
analysis of the experimental X-ray structures of compounds 3−5 was
carried out with CRITIC257 through the promolecular approximation,
first over the complete unit cell and then over selected pairs of
molecules, allowing us to assign precisely the spikes that correspond to a
selected intermolecular interaction.
With CrystalExplorer17,58 we carried out calculations of Hirshfeld
surfaces for the experimental X-ray structures of compounds 6−12
(using Tonto59) and mapped them with the Shape Index60,61 property
to find aromatic interactions.
For 11, the 4-bromophenyl fragment is disordered in two positions;
the first position has a chemical occupancy equal to 59%. The two
trifluoromethyl groups are disordered in two positions, with the main
positions having chemical occupancies equal to 54% and 63%. For the
RESULTS AND DISCUSSION
■
Ligands 1−4 were prepared in good yields, and 5 was prepared
in modest yield via Pd-catalyzed Sonogashira cross-coupling
3760
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Table 1. Halogen Bonds and Contacts in Crystals 3−5
compound
interaction
distance (Å)
angle (deg)
symm code
3
4
5
C12−Cl1···Cl1
C12−Br1···Br2
C12−I1···N1
3.5108(7)
3.6258(4)
3.083(5)
91.16(6)
82.42(7)
177.8(2)
1 − x, 1/2 + y, 3/2 − z
1 − x, 1/2 + y, 3/2 − z
1/2 + x, y, −1/2 + z
Figure 8. Aromatic interactions found in the crystal networks of 3−5.
reactions (Scheme 1). We were able to grow single crystals and
determine the structures of three (3−5) ligands.
Table 2. Geometries of Aromatic Interactions in the Crystal
Networks of 3−5
Crystal Structure of Ligands. In the crystal networks of 3
and 4, there are halogen−halogen interactions (Cl···Cl and Br···
Br, respectively). The Cl···Cl interaction is 0.3% longer than the
sum of their van der Waals radii. However, according to the
NCIplot56 analysis of 3, the Cl···Cl contact is nevertheless a
stabilizing interaction, because it appears as a spike in the low-
density, low-gradient negative region of the s vs sing(λ2)ρ plot,
where s is the reduced density gradient (s = 1/2(3π2)1/3|∇ρ|/
distance
(Å)
angle
(deg)
interaction
symm code
x, 1 + x, z
x, 1 + y, z
x, −1 + y, z
3
4
a
CC···Cg(1)
3.519
3.577
3.540
b
Cl1···Cg(2)
CC···Cg(2)
c
Cg(1a)−Cg(1b)
Cg(2a)−Cg(2b)
Cg(1b)−Cg(2a)
C19−H19···Cg(1a)
Br2···Cg(2b)
3.826
3.874
3.916
2.796
3.684
2.2
3.6
4.2
ρ
4/3) and ρ is the electron density (Figure 6). In the plot, the
d
black dots correspond to all of the intermolecular interactions in
the unit cell and the Cl···Cl interaction is highlighted in blue.
In the crystal network of 5, the iodine atom of the phenyl
fragment forms a halogen bond with the nitrogen atom in the
pyridine fragment of an adjacent molecule (C12−I1···N1). This
interaction forms halogen-bonded chains. Figure 7 and Table 1
show the geometries of intermolecular interactions involving
halogen atoms in crystals 3−5. In these type of molecules the I···
N interaction is substantially stronger than Cl/Br···N; thus, in
the supramolecular outcome we observe halogen-bonded chains
in 5, unlike the case for compounds 3 and 4.
x, −1 + y, z
−x, 1/2 + y, 1/2 − z
1 − x, 1/2 + y, 3/2 − z
5
C5−H5···Cg(1)
2.953
2.903
1/2+x, 1-y, z
1/2+x, 1-y, z
C14−H14···Cg(2)
a
b
c
Cg(1) = Py. Cg(2)  Ar. Cg(1a) = Py (4a), Cg(1b) = Py (4b).
d
Cg(2a) = Ar (4a), Cg(2b) = Ar (4b).
−Br, −I) in the crystal networks of 3−5. In the three cases, these
interactions are different and it is not easy to establish the effect
that each halogen has on them.
The aromatic interactions in crystals 3−5 are different in the
three cases. In the crystal network of 3, there are three different
aromatic interactions and none of them are between aromatic
rings. These intermolecular interactions are halogen−π (Cl1···
Cg(2)), alkyne−π (CC···Cg(1)), and alkyne−π (CC···
Cg(2)). In the crystal network of 4, there is also a wide variety of
aromatic interactions. There are three π−π interactions between
aromatic rings: two between equal rings, i.e., pyridine−pyridine
(Cg(1a)−Cg(1b)) and phenyl−phenyl (Cg(2a)−Cg(2b))
fragments, and one between different aromatic rings, i.e.
pyridine−phenyl (Cg(1b)−Cg(2a)). There are halogen−π
(Br2···Cg(2b)) and C−H···π (C19−H19···Cg(1a)) interac-
tions. In the crystal network of 5, there are two different aromatic
interactions; both are C−H···π and are between equal rings, i.e.
pyridine−pyridine (C5−H5···Cg(1)) and phenyl−phenyl
(C14−H14···Cg(2)) fragments. In Figure 8 and Table 2 are
shown the geometries of aromatic interactions found in crystals
3−5.
Crystal Structure of Coordination Compounds. On the
other hand, the coordination compounds (6−12) have similar
molecular and supramolecular structures. The seven coordina-
tion compounds are neutral and are hexacoordinated with an
octahedral geometry. They have two acetylacetonate derivatives
as ligands coordinated to the Cu(II) ion through the oxygen
atoms, and the two remaining coordination sites in trans
positions are occupied by 3-(phenylethynyl)pyridine derivatives
bonded through the nitrogen atom in the pyridine fragment. All
of these coordination compounds crystallize in the monoclinic
system in space group P21/n except for 12, which crystallizes in
space group C2/c. In all seven cases, the asymmetric units
contain half of the coordination compound with the Cu(II) ion
in a crystallographic special position (inversion center).
According to the unit-cell similarity index62 (Π ≃ 0) we can
categorize these coordination compunds into three groups: 6
and 7 are isostructural63 with each other, the series 8−11 is
isostructural, and compound 12 is the third group. Four of the
seven coordination compounds are tacac derivatives, and three
We do not observe a clear trend relating the aromatic
interactions formed with the substitution with halogens (−Cl,
3761
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 9. Relative orientation of ligands 1−5 in coordination compounds 6−12.
are hacac derivatives (tacac = trifluoroacetylacetonate, hacac =
hexafluoroacetylacetonate). We obtained single crystals with all
3-(phenylethynyl)pyridine derivatives at least once.
interaction isosurface of the NCIplot analysis is assigned a color
in parentheses that corresponds to the spikes in their respective
plots.
Even though all of the complexes have the same coordination
geometry, the relative orientation of ligands 1−5 is not the same
in all of the cases: i.e., in the coordination compound 6 the 3-
(phenylethynyl)pyridine (1) ligand is not oriented toward the
region of least steric hindrance, and the same thing happens in
compounds 7 and 12 (Figure 9).
According to these analyses, in coordination compound 6
there are six intramolecular hydrogen bonds. By symmetry, there
are three different types of intramolecular hydrogen bonds
labeled as BCP1, BCP2, and BCP3. In 7, there are two
intramolecular hydrogen bonds (BCP1 and BCP2), while in 12
there are three different intramolecular hydrogen bonds (BCP1,
BCP2, and BCP3) (Figure 10).
Table 3 shows the interaction energy of each intramolecular
hydrogen bond calculated according to the approximations of
Lu64 and Espinosa65 in the context of AIM analysis for
coordination compounds 6, 7, and 12. The NCIplot analyses
show the same energy trend for the intramolecular hydrogen
bonds since the sign(λ2)ρ value is related to the interaction
The AIM and NCIplot52,53 analyses of the wave functions of
the coordination compounds 6, 7, and 12 reveal the intra-
molecular interactions responsible for the relative orientation,
toward the region of greater steric hindrance, of the ligands.
These analyses are visualized in the same spatial region, since
they complement each other. In Figure 10 the bond critical
points of the AIM analysis are labeled as BCP#; each relevant
3762
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 10. Intramolecular hydrogen bonds revealed by AIM+NCIplot analyses in compounds 6, 7, and 12.
Table 3. Energy Values of BCPs and Electron Densities (ρ) of the Intramolecular Interaction Surfaces
AIM analysis
energy (kJ/mol)
NCI plot analysis
compound
BCP
ρ (au)
V(r)(Eh)
Espinosa
Lu
sign(λ2)ρ (au)
6
BCP1
BCP2
BCP3
0.0073
0.0096
0.0045
−0.0044
−0.0060
−0.0025
−5.7
−7.9
−3.3
−3.7
−5.9
−1.1
−0.0073
−0.0096
−0.0045
7
BCP1
BCP2
0.0074
0.0088
−0.0044
−0.0054
−5.8
−7.1
−3.8
−5.1
−0.0074
−0.0088
12
BCP1
BCP2
BCP3
0.0007
0.0129
0.0155
−0.0004
−0.0091
−0.0113
−0.5
−11.9
−14.9
2.4
−8.9
−11.3
−0.0007
−0.0129
−0.0155
energy:53 i.e., the most negative value has the highest interaction
energy. The energy trend for the intramolecular hydrogen bonds
in compound 6 is BCP2 > BCP3 > BCP1, in compound 7 it is
BCP2 > BCP1, and in 12 it is BCP3 > BCP2 > BCP1.
3763
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 11. 1-D chains assembled through head to tail π−π interactions in crystal networks of tacac−based coordination compounds.
In these cases (6, 7, and 12) the hydrogens in positions ortho
to the nitrogen atom in the pyridine fragment form nonclassical
hydrogen bonds with the oxygen atoms of the acac-based
ligands. In compounds 6 and 7, the intramolecular hydrogen
bonds are established with the oxygens closer to the
trifluoromethyl groups because a second intramolecular
interaction is formed with the fluorine atoms in the
trifluoromethyl fragment as well.
neous. In the crystal networks of compounds 6−12, the metal-
containing building units; i.e. coordination compounds, are
assembled into 1-D chains through aromatic interactions
between the 3-(phenylethynyl)pyridine derivative ligands.
In compounds 6−11, the ligands engage in π−π interactions
in a head to tail fashion: i.e., the pyridine fragment in one
compound interacts with the phenyl fragment of another and
vice versa, while in complex 12 the π−π interactions are
established between phenyl rings. In Figures 11 and 12 are
Although the coordination compounds have different
conformations, their supramolecular behavior is very homoge-
3764
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 12. 1-D chains assembled through head to tail π−π interactions in crystal networks of hacac−based coordination compounds.
Figure 13. Hirshfeld surface mapped with Shape Index of compound 9, with the color and shape complementarity due to π−π aromatic interactions,
Cg(1)−Cg(2).
3765
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
Figure 14. Head to tail π−π interactions between ligands 3 in the crystal network of compound 10.
a
Table 4. Geometric Parameters of the Head to Tail π−π Aromatic Interactions and the Cu···Cu Distances for Compounds 6−12
b
c
d
coordination compound
Cg(1)−Cg(2) distance (Å)
θ angle (deg)
Cu···Cu distance (Å)
symm code
6
7
8
9
4.02
4.06
3.80
3.85
22.5
23.2
4.0
12.7534(9)
12.792(1)
13.742(3)
13.9606(8)
−x, −y, 1 − z
−x, −y, 1 − z
x, 1 + y, z
6.3
x, 1 + y, z
10
11
12
3.79
3.81
4.04
2.9
4.0
0.0
13.8073(4)
13.9668(9)
16.5951(7)
x, 1 + y, z
x, 1 + y, z
−1/2 + x, −1/2 + y, z
e
a
b
c
The empty row separates tacac- and hacac-based coordination compounds. Cg(1)−Cg(2) is the centroid to centroid distance. θ is the angle
between the interacting ring planes. Cu···Cu is the distance between Cu(II) ions inside the 1-D chains. Cg(2)−Cg(2) π−π aromatic interaction.
d
e
Figure 15. MEP maps of the free ligands 3−5 and coordination compounds 10−12.
shown the 1-D chains formed through these interactions in all of
these coordination compounds.
figure are shown those surfaces so that the regions in contact are
visible. This view allows a determination of the color and shape
complementarity due to π−π aromatic interactions.60 At the
bottom, the figure presents the dimer of coordination
compounds bound through these interactions, Cg(1)−Cg(2).
In Figure 14 are shown the π−π interactions in detail with the
geometric parameters used to characterize them.
We observed these interactions on the Hirshfeld surface
mapped with Shape Index thanks to the color and shape
complementarity between neighboring surfaces. For com-
pounds 6−11, the interaction geometries are the same and is
exemplified in Figure 13 by compound 9. The figure displays at
the top two adjacent Hirshfeld surfaces, which involve two
neighboring coordination compounds. In the middle of the
In Table 4 are given the values of geometric characterization
of the π−π aromatic interactions found in the crystal networks of
3766
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
these coordination compounds. In general, substitution with
halogen atoms on the phenyl fragment slightly shortens the
aromatic interaction distance, Cg(1)−Cg(2). The same
happens with the θ angle, which is smaller when there is a
halogen on the phenyl fragment: i.e., the interacting rings tend to
become coplanar. The Cu···Cu distance shows a slight increase
as the halogen atom increases in size. In complex 12 the distance
is the longest because the aromatic interaction formed is
different, Cg(2)−Cg(2).
In Figures 8, 11, and 12 are shown the differences in aromatic
interactions found in the crystal networks of the free ligands and
coordination compounds. While in the first case we do not have
control over aromatic interactions and we do not see any logical
trend through substitution with different halogens, in the second
case we observe the assembly of 1-D chains in all cases due to the
presence of the same aromatic interaction between the
coordination compounds. This gain in control is due to the
formation of the coordination bond, since the pyridine fragment
has to donate electron density to the copper(II) ion
(coordination bonds have an electrostatic and a covalent
component), which results in a polarization of the aromatic
rings different from that found in the free ligands.
all of the compounds. We can see that in all of the cases the most
negative electrostatic potential is over the halogen atom of the
phenyl fragment. This leads to the conclusion that the geometry
of the π−π interactions in compound 12 is due to the size of the
iodine atom, which does not allow coordination compounds to
approach each other closely and form a head to tail aromatic
interaction in the same way as for the other coordination
compounds.
We think that these electrostatic complementary aromatic
interactions can be used to synthesize new crystal networks with
pyridine derivatives different from those used here: i.e., we could
use various functional groups to bind the pyridine and phenyl
rings and it could be an interesting approach to control the
metrics of 1-D chains, that is, to control the Cu···Cu distance.
The phenyl ring must not be electron deficient, since the
pyridine fragment is an electron-deficient aromatic ring due to
coordination bond formation with the metal center. Finally, as
an auxiliary ligand there must be a charge-balancing anion with a
high electron-withdrawing effect and without the possibility to
disrupt aromatic interactions.
The molecular electrostatic potential (MEP) maps calculated
over the free ligands and the coordination compounds evince
the changes due to the coordination bond. In Figure 15 are
shown the MEP maps of the free ligands 3−5 and the
coordination compounds 10−12, and the values in the centroids
of the aromatic rings are highlighted. For example, the pyridine
fragment of the free ligand 3 has a value of −16 kJ/mol, while the
same fragment coordinated to the Cu(II) ion in complex 10 has
a value of 21.6 kJ/mol. The same happens with the free ligands 4
and 5, where the pyridine fragment negative electrostatic
potential changes to a positive value on coordination.
CONCLUSIONS
■
We synthesized metal-containing 1-D chains through π−π
aromatic interactions with meta-substituted pyridines and acac-
based ligands regardless of the orientation of the 3-
(phenylethynyl)pyridine ligands within the coordination
compounds or the changes in the acac-based ligands. However,
we found that the aromatic interactions are slightly sensitive to
substitution with halogen atoms: i.e., the interacting ring planes
tend to become coplanar and the centroid to centroid distance
shortens when there is a halogen atom on the phenyl fragment.
Through the formation of coordination bonds and the
changes in the polarization of aromatic rings that it entails, we
gain control over the π−π interaction geometry, promoting a
head to tail interaction between 3-(phenylethynyl)pyridine
derivatives ligands, thanks to electrostatic complementarity.
This approach to constructing 1-D chains is reliable and
reproducible. Thus, despite the lack of directionality, this type of
π−π aromatic interaction can be used as a supramolecular tool
to control molecular assembly in the solid state.
In Table 5 are given the values of the electrostatic potential on
the surface over the ring centroids of pyridine and phenyl
Table 5. MEP Values (kJ/mol) on the Surface of the Free
a
Ligands and the Coordination Compounds
fragment
compound
pyridine
phenyl
halogen
3
4
5
−16.0
−16.5
−16.2
−21.8
−21.1
−25.1
−34.8
−35.4
−32.6
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.cgd.1c00083.
6
7
8
9
−14.2
−8.2
−4.5
−3.6
−52.0
−26.1
−19.7
−19.1
N/A
−53.3
−37.7
−36.1
FT-IR, NMR, and MS spectra of 1−5, crystal, collection,
and refinement data of 3−12, NCIplot analysis of 3−5,
Hirshfeld surfaces of 6−12 mapped with Shape Index,
aromatic interactions on Hirshfeld surfaces of 6−8, 10,
and 11, and MEP maps of 6−9 (PDF)
10
11
12
21.6
23.5
29.0
−16.3
−14.9
−19.3
−36.1
−31.1
−30.2
a
The empty rows separate the free ligands and tacac- and hacac-based
compounds.
Accession Codes
CCDC 2039668−2039670 and 2053862−2053868 contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.
uk, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
1223 336033.
fragments and the halogen substituent on the phenyl fragment.
In the pyridine-fragment centroid, the values become less
negative for tacac-based coordination compounds and finally
become positive for the hacac-based complexes. It is clear that
hexafluoroacetylacetonate (hacac) promotes a greater polar-
ization of the pyridine fragment through the Cu(II) ion. In the
phenyl fragment, the electrostatic potential remains negative in
3767
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
effect of a single-atom change in the ligand. Dalton Trans. 2015, 44,
5488−5502.
(15) Khavasi, H. R.; Azizpoor Fard, M. π- π interactions affect
coordination geometries. Cryst. Growth Des. 2010, 10, 1892−1896.
(16) Azizpoor Fard, M.; Behnia, A.; Puddephatt, R. J. Coordination
chemistry of mercury (II) with 2-pyridylnitrones: monomers to
polymers. Dalton Trans. 2017, 46, 3579−3587.
(17) Aakeröy, C. B.; Schultheiss, N.; Desper, J.; Moore, C. Attempted
assembly of discrete coordination complexes into 1-D chains using
halogen bonding or halogen···halogen interactions. CrystEngComm
2007, 9, 421−426.
(18) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The
chemistry and applications of metal-organic frameworks. Science 2013,
341, 1230444.
AUTHOR INFORMATION
Corresponding Authors
Rafael León-Zárate − Instituto de Química, Universidad
Nacional Autónoma de México, 04510 Ciudad México,
México; orcid.org/0000-0003-3040-202X; Phone: +52
56224420; Email: raleon@comunidad.unam.mx
́
Jesus Valdés-Martínez − Instituto de Química, Universidad
Nacional Autónoma de México, 04510 Ciudad México,
México; orcid.org/0000-0002-8511-9662;
Email: jvaldes@unam.mx
■
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.cgd.1c00083
(19) Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi, E.;
Yazaydin, A.; Snurr, R. Q.; O’Keeffe, M.; Kim, J.; Yaghi, O. M. Ultrahigh
porosity in metal-organic frameworks. Science 2010, 329, 424−428.
(20) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.;
Eddaoudi, M.; Kim, J. Reticular synthesis and the design of new
materials. Nature 2003, 423, 705−714.
(21) Hanikel, N.; Prévot, M. S.; Fathieh, F.; Kapustin, E. A.; Lyu, H.;
Wang, H.; Diercks, N. J.; Glover, T. G.; Yaghi, O. M. Rapid cycling and
exceptional yield in a metal-organic framework water harvester. ACS
Cent. Sci. 2019, 5, 1699−1706.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the UNAM-DGAPA PAPIIT
(IN214919) program. R L.-Z. acknowledges CONACYT for the
scholarship received. We thank Andrés Aguilar-Granda for
technical support and Simón Hernández-Ortega and Rubén A.
Toscano for crystal data collection.
(22) Dorazco-González, A.; Martinez-Vargas, S.; Hernández-Ortega,
S.; Valdés-Martínez, J. Directed self-assembly of mono and dinuclear
copper (II) isophthalates into 1D polymeric structures. Design and an
unusual cocrystallization. CrystEngComm 2013, 15, 5961−5968.
(23) Dumitru, F.; Englert, U.; Braun, B. Orientational disorder in the
one-dimensional coordination polymer catena-poly [[bis (acetylaceto-
nato-κ2O, O’) cobalt (II)]-μ-1, 4-diazabicyclo [2.2.2] octane-κ2N1:N4].
Acta Crystallogr. 2016, E72, 548−551.
REFERENCES
■
(1) Beatty, A. M. Open-framework coordination complexes from
hydrogen-bonded networks: toward host/guest complexes. Coord.
Chem. Rev. 2003, 246, 131−143.
(2) Aakeröy, C. B.; Beatty, A. M. Crystal engineering of hydrogen-
bonded assemblies-a progress report. Aust. J. Chem. 2001, 54, 409−421.
(3) Cavallo, G.; Metrangolo, P.; Milani, R.; Pilati, T.; Priimagi, A.;
Resnati, G.; Terraneo, G. The halogen bond. Chem. Rev. 2016, 116,
2478−2601.
(24) Zahedi, M.; Shaabani, B.; Aygun, M.; Kazak, C. Construction of
̈
one dimensional Co (II) and Zn (II) coordination polymers based on
expanded N, N’-donor ligands. Inorg. Chim. Acta 2018, 469, 461−468.
(25) Aakeröy, C. B.; Desper, J.; Valdés-Martínez, J. Controlling
molecular and supramolecular structure of hydrogen-bonded coordi-
nation compounds. CrystEngComm 2004, 6, 413−418.
(4) Mukherjee, A.; Tothadi, S.; Desiraju, G. R. Halogen bonds in
crystal engineering: like hydrogen bonds yet different. Acc. Chem. Res.
2014, 47, 2514−2524.
(5) Priimagi, A.; Cavallo, G.; Metrangolo, P.; Resnati, G. The halogen
bond in the design of functional supramolecular materials: recent
advances. Acc. Chem. Res. 2013, 46, 2686−2695.
(26) Germán-Acacio, J. M.; Hernández-Ortega, S.; Aakeröy, C. B.;
Valdés-Martínez, J. Using Lewis acidity differences in chelating ligands
to control molecular structure and supramolecular assembly of Cu (II)
complexes. Inorg. Chim. Acta 2009, 362, 4087−4090.
(6) Metrangolo, P.; Meyer, F.; Pilati, T.; Resnati, G.; Terraneo, G.
Halogen bonding in supramolecular chemistry. Angew. Chem., Int. Ed.
2008, 47, 6114−6127.
(27) Aakeröy, C. B.; Scott, B. M. T.; Smith, M. M.; Urbina, J. F.;
Desper, J. Establishing amide··· amide reliability and synthon
transferability in the supramolecular assembly of metal-containing
one-dimensional architectures. Inorg. Chem. 2009, 48, 4052−4061.
(28) Aakeröy, C. B.; Schultheiss, N.; Desper, J. Directed supra-
molecular assembly of infinite 1-D M(II)-containing chains (M= Cu,
Co, Ni) using structurally bifunctional ligands. Inorg. Chem. 2005, 44,
4983−4991.
(7) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Dougherty, D. A.;
Grubbs, R. H. Phenyl-perfluorophenyl stacking interactions: A new
strategy for supermolecule construction. Angew. Chem., Int. Ed. Engl.
1997, 36, 248−251.
(8) Sinnwell, M. A.; Baltrusaitis, J.; MacGillivray, L. R. Combination of
argentophilic and perfluorophenyl-perfluorophenyl interactions sup-
ports a head-to-head [2+ 2] photodimerization in the solid state. Cryst.
Growth Des. 2015, 15, 538−541.
(9) Sonoda, Y.; Goto, M.; Tsuzuki, S.; Akiyama, H.; Tamaoki, N. [2+
2] Photodimerization and photopolymerization of diphenylhexatriene
crystals utilizing perfluorophenyl-phenyl stacking interactions. J.
Fluorine Chem. 2009, 130, 151−157.
(10) Serrano-Becerra, J. M.; Hernández-Ortega, S.; Morales-Morales,
D.; Valdés-Martínez, J. Bottom-up design and construction of a non-
centrosymmetric network through π-π stacking interactions. CrystEng-
Comm 2009, 11, 226−228.
(29) Aakeröy, C. B.; Hussain, I.; Forbes, S.; Desper, J. Versatile
Ligands for the Construction of Layered Metal-Containing Networks.
Aust. J. Chem. 2009, 62, 899−908.
́
(30) Kukovec, B.-M.; Malik, M.; Kodrin, I.; Aakeroy, C. B.; Đakovic,
M. Directed assembly of acac-based complexes by deliberately fine-
tuning electrostatic molecular-recognition events. Cryst. Growth Des.
2016, 16, 7308−7317.
́
(31) Borovina, M.; Kodrin, I.; Đakovic, M. Predicting supramolecular
connectivity of metal-containing solid-state assemblies using calculated
molecular electrostatic potential surfaces. Cryst. Growth Des. 2019, 19,
1985−1995.
(11) Bosch, E.; Radford, R.; Barnes, C. L. Donor- Acceptor
Interactions in Crystal Engineering. Org. Lett. 2001, 3, 881−883.
(12) Khavasi, H. R.; Kavand, S. π-Stacking synthon repetitivity in
coordination compounds. CrystEngComm 2016, 18, 4760−4764.
(13) Khavasi, H. R.; Rahimi, N. Fluorine-Substituted Ligands Induce
Structural Diversity of Coordination Compounds. ChemistrySelect.
2017, 2, 11314−11321.
́
(32) Gamekkanda, J. C.; Sinha, A. S.; Desper, J.; Đakovic, M.;
Aakeröy, C. B. The Role of Halogen Bonding in Controlling Assembly
and Organization of Cu (II)-Acac Based Coordination Complexes.
Crystals 2017, 7, 226.
́
(33) Borovina, M.; Kodrin, I.; Đakovic, M. Testing the limits of
halogen bonding in coordination chemistry. CrystEngComm 2018, 20,
539−549.
(14) Khavasi, H. R.; Sadegh, B. M. M. Influence of N-heteroaromatic
π−π stacking on supramolecular assembly and coordination geometry;
3768
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769

Crystal Growth & Design
pubs.acs.org/crystal
Article
(34) Rozhkov, A. V.; Novikov, A. S.; Ivanov, D. M.; Bolotin, D. S.;
Bokach, N. A.; Kukushkin, V. Y. Structure-Directing Weak Interactions
with 1,4-Diiodotetrafluorobenzene Convert One-Dimensional Arrays
of [MII(acac)2] Species into Three-Dimensional Networks. Cryst.
Growth Des. 2018, 18, 3626−3636.
(35) Stilinovic, V.; Grguric, T.; Pitesa, T.; Nemec, V.; Cincic, D.
Bifurcated and monocentric halogen bonds in cocrystals of metal (II)
acetylacetonates with p-dihalotetrafluorobenzenes. Cryst. Growth Des.
2019, 19, 1245−1256.
(36) Aakeröy, C. B.; Sinha, A. S.; Chopade, P. D.; Desper, J. Halogen
bonding or close packing? Examining the structural landscape in a series
of Cu (II)-acac complexes. Dalton Trans. 2011, 40, 12160−12168.
(37) Kahn, O. Chemistry and physics of supramolecular magnetic
materials. Acc. Chem. Res. 2000, 33, 647−657.
(38) Kusamoto, T.; Hattori, Y.; Tanushi, A.; Nishihara, H.
Intramolecular Ferromagnetic Radical-CuII Coupling in a CuII
Complex Ligated with Pyridyl-Substituted Triarylmethyl Radicals.
Inorg. Chem. 2015, 54, 4186−4188.
(56) Otero-De-La-Roza, A.; Johnson, E. R.; Contreras-García, J.
Revealing non-covalent interactions in solids: NCI plots revisited. Phys.
Chem. Chem. Phys. 2012, 14, 12165−12172.
(57) Otero-de-la Roza, A.; Johnson, E. R.; Luana, V. Critic2: A
̃
program for real-space analysis of quantum chemical interactions in
solids. Comput. Phys. Commun. 2014, 185, 1007−1018.
(58) Turner, M. J.; McKinnon, J. J.; Wolff, S. K.; Grimwood, D. J.;
Spackman, P. R.; Jayatilaka, D.; Spackman, M. A. CrystalExplorer17;
2017.
(59) Jayatilaka, D., Grimwood, D. J. Tonto: a fortran based object-
oriented system for quantum chemistry and crystallography; International
Conference on Computational Science, 2003; pp 142−151.
(60) Spackman, M. A.; Jayatilaka, D. Hirshfeld surface analysis.
CrystEngComm 2009, 11, 19−32.
(61) McKinnon, J. J.; Spackman, M. A.; Mitchell, A. S. Novel tools for
visualizing and exploring intermolecular interactions in molecular
crystals. Acta Crystallogr., Sect. B: Struct. Sci. 2004, B60, 627−668.
(62) Kalman, A.; Párkányi, L.; Argay, G. Classification of the
isostructurality of organic molecules in the crystalline state. Acta
Crystallogr., Sect. B: Struct. Sci. 1993, 49, 1039−1049.
(39) Kimura, S.; Uchida, H.; Kusamoto, T.; Nishihara, H. One-
dimensional magnetic chain composed of Cu II and polychlorinated
dipyridylphenylmethyl radical: temperature-dependent Jahn-Teller
distortion correlated to π-conjugation and magnetic properties. Dalton
Trans. 2019, 48, 7090−7093.
(63) https://dictionary.iucr.org/Isostructural_crystals.
(64) Emamian, S.; Lu, T.; Kruse, H.; Emamian, H. Exploring Nature
and Predicting Strength of Hydrogen Bonds: A Correlation Analysis
Between Atoms-in-Molecules Descriptors, Binding Energies, and
Energy Components of Symmetry-Adapted Perturbation Theory. J.
Comput. Chem. 2019, 40, 2868−2881.
(65) Espinosa, E.; Molins, E.; Lecomte, C. Hydrogen bond strengths
revealed by topological analyses of experimentally observed electron
densities. Chem. Phys. Lett. 1998, 285, 170−173.
́
(40) Gunawardana, C. A.; Sinha, A. S.; Desper, J.; Đakovic, M.;
Aakeröy, C. B. Supramolecular Chemistry of Some Metal Acetylacet-
onates with Auxiliary Pyridyl Sites. Cryst. Growth Des. 2018, 18, 6936−
6945.
̌
(41) Kodrin, I.; Borovina, M.; Smital, L.; Valdés-Martínez, J.; Aakeröy,
́
C. B.; Đakovic, M. Exploring and predicting intermolecular binding
preferences in crystalline Cu (II) coordination complexes. Dalton
Trans. 2019, 48, 16222−16232.
(42) Bosch, E.; Bowling, N. P.; Darko, J. The power of nonconven-
tional phenyl C-H··· N hydrogen bonds: Supportive crystal-packing
force and dominant supramolecular engineering force. Cryst. Growth
Des. 2015, 15, 1634−1641.
(43) APEX2 v2014.1-1, APEX3 v2016.1, APEX3 v2018.1-0; Bruker
AXS: Madison, WI, USA.
(44) SAINT v8.34A, SAINT v8.37A, SAINT v8.38A; Bruker AXS:
Madison, WI, USA.
(45) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta
Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8.
(46) Sheldrick, G. M. SHELXT − Integrated space-group and crystal-
structure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71,
3−8.
(47) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. OLEX2: a complete structure solution, refinement and
analysis program. J. Appl. Crystallogr. 2009, 42, 339−341.
(48) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G.
A.; Nakatsuji, H. et al. Gaussian 16, rev. a.03; Gaussian Inc.: Wallingford,
CT, 2016, 2.
(49) Dennington, R.; Keith, T. A.; Millam, J. M. GaussView, ver. 6.0.16;
Semichem Inc.: Shawnee Mission, KS, 2016,.
(50) Bader, R. F. W. A quantum theory of molecular structure and its
applications. Chem. Rev. 1991, 91, 893−928.
(51) Atoms in Molecules: A Quantum Theory; Oxford University Press:
New York, 1990.
(52) Johnson, E. R.; Keinan, S.; Mori-Sánchez, P.; Contreras-García,
J.; Cohen, A. J.; Yang, W. Revealing noncovalent interactions. J. Am.
Chem. Soc. 2010, 132, 6498−6506.
(53) Contreras-García, J.; Yang, W.; Johnson, E. R. Analysis of
hydrogen-bond interaction potentials from the electron density:
integration of noncovalent interaction regions. J. Phys. Chem. A 2011,
115, 12983−12990.
(54) Lu, T.; Chen, F. Multiwfn: a multifunctional wavefunction
analyzer. J. Comput. Chem. 2012, 33, 580−592.
(55) Humphrey, W.; Dalke, A.; Schulten, K. VMD: visual molecular
dynamics. J. Mol. Graphics 1996, 14, 33−38.
3769
https://doi.org/10.1021/acs.cgd.1c00083
Cryst. Growth Des. 2021, 21, 3756−3769