Supramolecular interactions in a family of dinuclear helicates in the solid-state

Article abstract of DOI:10.1080/10610278.2020.1792906

Metallo-helicates are a commonly encountered assembly within supramolecular chemistry. Interest in these architectures stems from their inherent helical chirality which positions them for a diverse range of applications such as catalysis and non-linear optics (NLO). The current study uses Co(II) dinuclear double helicates as versatile supramolecular synthons. The ditopic ligand, L, features two tridentate quinolinyl-hydrazone binding sites imparting it with hydrogen bond donors and π-faces for secondary supramolecular interactions. Incorporation of L into [Co₂(L)₂]⁴⁺ helical assemblies results in a helical cationic supramolecular synthon with moieties predisposed to forming π-π stacking and hydrogen bond interactions. The single-crystal X-ray structures of [Co₂(L)₂]X₄ (X?=?ClO₄^?, BF₄^? and CF₃SO₃^?) revealed a variety of anion dependent hydrogen bond networks arising through the interaction of the hydrazide hydrogen with the anion. These interactions in turn strongly influence the nature of the π-π stacking interactions of the quinoline moieties which can be analysed via the Hirshfield surface.

Full text of DOI:10.1080/10610278.2020.1792906

Supramolecular Chemistry
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Supramolecular interactions in a family of
dinuclear helicates in the solid-state
Benjamin H. Wilson & Paul E. Kruger
To cite this article: Benjamin H. Wilson & Paul E. Kruger (2020): Supramolecular interactions
in a family of dinuclear helicates in the solid-state, Supramolecular Chemistry, DOI:
10.1080/10610278.2020.1792906
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SUPRAMOLECULAR CHEMISTRY
https://doi.org/10.1080/10610278.2020.1792906
ARTICLE
Supramolecular interactions in a family of dinuclear helicates in the solid-state
a,b
a
Benjamin H. Wilson
and Paul E. Kruger
a
MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Physical and Chemical Sciences, University of Canterbury,
b
Christchurch, New Zealand; Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
ABSTRACT
ARTICLE HISTORY
Received 30 April 2020
Accepted 30 June 2020
Metallo-helicates are a commonly encountered assembly within supramolecular chemistry.
Interest in these architectures stems from their inherent helical chirality which positions them for
a diverse range of applications such as catalysis and non-linear optics (NLO). The current study uses
Co(II) dinuclear double helicates as versatile supramolecular synthons. The ditopic ligand, L,
features two tridentate quinolinyl-hydrazone binding sites imparting it with hydrogen bond
KEYWORDS
Metallo-helicate;
coordination chemistry;
crystallography
4
+
donors and π-faces for secondary supramolecular interactions. Incorporation of L into [Co
helical assemblies results in a helical cationic supramolecular synthon with moieties predisposed to
forming π-π stacking and hydrogen bond interactions. The single-crystal X-ray structures of [Co
2 2
(L) ]
2
−
−
−
(
L) ]X (X = ClO , BF and CF SO ) revealed a variety of anion dependent hydrogen bond
2 4 4 4 3 3
networks arising through the interaction of the hydrazide hydrogen with the anion. These inter-
actions in turn strongly influence the nature of the π-π stacking interactions of the quinoline
moieties which can be analysed via the Hirshfield surface.
Introduction
their supramolecular interactions. It is this avenue of
research that has led to metallo-helicates becoming pro-
minent assemblies in crystal engineering and their use as
supramolecular synthons [34,35]. The ligands provide
a point of attachment functionality capable of forming
supramolecular interactions with neighbouring molecules
or counter anions. These functionalities may orient into
specific directions relative to one another upon coordina-
tion of the ligands to the metal ions to form the helical
structure, resulting in a highly directionally specific supra-
molecular synthon. Our group is concerned with the
synthesis of dinuclear M(II) helicates and mesocates [12–
Metallo-helicates are a widely studied form of metallo-
supramolecular assembly [1–3]. The combination of metal
centres and organic ligands has resulted in many double,
triple and quadruple stranded helicates that possess
a diverse range of properties such as redox activity [4–7],
fluorescence [8–11], spin crossover [12–22] and single-
molecule magnetism [9,23–25]. Furthermore, topologi-
cally complex circular helicates can be utilised as building
blocks for the synthesis of mechanically intertwined mole-
cular knot assemblies [26–28]. Much of the interest in
helicate structures stems from the intrinsic chirality
adopted by the twisted conformation of the bridging
ligands [29]. The helical chirality of these supramolecular
assemblies makes them highly suictable candidates for
DNA binding [10,30–32] or asymmetric catalysis [33].
Optimisation of the interaction of metallo-helicates with
chiral substrates requires a thorough understanding of
14,36,37]. Recently our attention has been focused on the
use of ligands incorporating the pyrazinyl-hydrazone
coordinating moiety. This work highlighted the applicabil-
ity of such dinuclear supramolecular assemblies as supra-
molecular synthons via the ability of the hydrazide (N)H to
act as a potent hydrogen bond donor [37]. Flexible
CONTACT Benjamin H. Wilson
bwilson@uwindsor.ca
Chemical Sciences, University of Canterbury, Christchurch, New Zealand
MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Physical and
Supplemental data for this article can be accessed here.
©
2020 Informa UK Limited, trading as Taylor & Francis Group

2
B. H. WILSON AND P. E. KRUGER
−
1
ligands derived from a succinic acid core featuring pyridyl-
hydrazone coordinating groups have been recently
reported to form dinuclear double helicates upon com-
plexation with Co(II) and displayed single-molecule mag-
netism and catalytic behaviour [25,33]. Herein we report
the synthesis of a related novel ligand, L, featuring the
quinolinyl-hydrazone coordinating moiety (Figure 1). The
introduction of a larger quinoline aromatic functionality
should introduce a greater tendency for π-π stacking [38].
In conjunction with the potent hydrazide hydrogen bond
donor [39–42,43], the incorporation of this ligand into
a Co(II) dinuclear double helicate results in a versatile
cationic supramolecular synthon. This work investigates
the variation of the crystal packing of these helicates upon
modulation of the counter anion and seeks to rationalise
the importance of hydrogen bonding and π-π interactions
on the resultant structures. Analysis of the Hirshfield sur-
faces provided further insight into the importance of the
supramolecular interactions occurring between com-
plexes in each of their crystal lattices.
heated from 10°C to 800°C at a rate of 1.5°C min . For C,
H, N analysis, samples were sent to Campbell
Microanalytical
Laboratories,
Otago
University,
Dunedin. Samples were dried to constant weigh before
analysis. Caution is advised when handling perchlorate
salts as they are potentially explosive.
Ligand synthesis
Succinyl hydrazide
Succinyl hydrazide was synthesised following a literature
preparation [44]. Diethyl succinate (2.8 mL, 17 mmol)
and hydrazine monohydrate (4.2 mL, 85 mmol) were
added sequentially to ethanol (10 mL) and the solution
was heated at reflux for 12 hours during which a white
crystalline precipitate formed. After cooling to room
temperature, the white precipitate was filtered and
washed with ethanol then diethyl ether (1.25 g,
11 mmol, 65% yield). M.pt. 158°C–160°C Lit. 166°C, δH
(400 MHz, [d ]-DMSO): 8.95 (s, 1 H, H ), 4.12 (s, 2 H, HNH),
6
NH
+
2
.23 (2 H, s, H ), ESI-MS: meas. 147.0877 ([M + H] ), [C
alkyl 4
+
H N O ] calc. 147.0877
1
1 4 2
Materials and methods
All reagents and solvents used were of reagent grade
unless otherwise stated and did not require further pur-
ification. In-house distilled water was used. Chemicals
were sourced from Sigma Aldrich and used as received.
All reactions were carried out in air unless otherwise
(N’1E,N’4E)-N’1,N’4-bis(quinolin-2-ylmethylene)
succinohydrazide, L
Quinoline-2-carbaldehyde 1.6 g, 10 mmol was dissolved
in ethanol (50 mL) at reflux. Succinic dihydrazide (0.5 g,
4.4 mmol) was added to give a brown suspension which
was heated at reflux overnight. The brown suspension
was then cooled to room temperature and filtered then
washed with boiling ethanol and oven dried for one hour
at 70 ⁰C to give a pale brown solid (1.1 g, 2.6 mmol, 60%
1
13
stated. H and
C NMR measurements were carried
out on an Agilent 400 MR spectrometer operating at
1
13
4
00 MHz for H and 101 MHz for
C. Chemical shift
values are given in parts per million (PPM). Melting
points were carried out on an Electrothermal melting
point apparatus and are uncorrected. FT-IR spectra for
organic compounds were recorded a Bruker ALPHA
Platinum ATR FT-IR spectrometer measuring in the
yield). M.pt. 255°C–260°C (decomposition), δ (400 MHz,
H
[d ]-DMSO) 11.70 (s, 1 H, HNH), 8.36 (m, 2 H, Hquinoline), 8.18
6
(1 H, s, Himine), 8.02 (m, 2 H, Hquinoline), 7.77 (t, J = 7.6, 1 H,
Hquinoline), 7.62 (m, 1 H, Hquinoline), 3.08 (s, 2 H, Halkyl), Low
−1
13
range 4000–450 cm . The following abbreviations
were used to describe the signals: s (strong), m (medium),
w (weak), br (broad). Mass spectrometry experiments
were carried out on a Bruker maXis 4 G time of flight
spectrometer operating in ESMS+ mode. Values are
given as MH+ (unless otherwise stated). TGA measure-
ments were performed on an Alphatech SDT Q600 TGA/
DSC under an inert nitrogen atmosphere. Samples were
solubility precluded analysis by C NMR, ESI-MS: meas.
2+
2+
213.0896 ([M + 2 H] ), [C H N O ] calc. 213.0897, IR:
2
4 22 6 2
−1
(νmax/cm ) 3062 (w), 2988 (w), 2950 (w), 2899 (w), 1669 (s)
1639 (w), 1588 (m), 1558 (w), 1519 (w), 1504 (m), 1458 (m),
1441 (m), 1429 (w), 1397 (s), 1349 (w), 1327 (w), 1311 (m),
1300 (m), 1237 (w), 1205 (m) 1153 (s), 1142 (s), 1113 (m),
1018 (w), 995 (w), 977 (m), 942 (s), 902 (m), 881 (w), 839 (s),
806 (s), 790 (m), 774 (m), 755 (s), 692 (w), 644 (w), 621 (m)
Figure 1. (colour online) The ligand, L, reported in this work featuring the hydrazone and quinoline moieties. The combination of
−
−
−
4
−
L with CoX (X = ClO , BF and CF SO ) results in the formation of a dinuclear double-stranded helicate of the generalised formula
2
4
3
3
[
Co (L) ]X , represented schematically.
2 2 4

SUPRAMOLECULAR CHEMISTRY
3
Complex synthesis
Co (L) ](ClO ) , 1
3197 (br., w), 2939 (br.,w), 1619 (m), 1589 (w), 1544 (m),
1
1
510 (m), 1436 (w), 1407 (w), 1382 (m), 1336 (w), 1244 (s),
224 (s), 1166 (s), 1140 (s), 1025 (s), 999 (m), 937 (m), 918
[
2
2
4 4
Co(ClO ) · 6H O (8.6 mg, 23.6 μmol) was dissolved in
4
2
2
(w), 871 (w), 829 (m), 786 (m), 753 (m), 698 (w), 634 (s),
acetonitrile (15 mL) and was stirred at room temperature.
L (10 mg, 23.6 μmol) was added to give a pale brown/
yellow suspension and stirred for approximately 5 hours to
give an orange/brown cloudy solution. The cloudy solution
was allowed to stand at room temperature for 2 hours and
then filtered to give a yellow/brown solution. Vapour diffu-
sion of benzene into the filtrate resulted in orange block
crystals suitable for single crystal X-ray diffraction. Found: C,
5
73 (m), 514 (m), 483 (m)
Results and discussion
The ligand, L, was synthesised following adapted litera-
ture procedures for analogous ligands [23]. The com-
plexes 1 to 3 were synthesised by complexing the
−
ligand, L, with the appropriate CoX salt (X = ClO 1,
2
4
40.53 H, 2.83, N, 11.52% [Co (C H N O ) ](ClO ) · 5(H
2 24 20 6 2 2 4 4 2
−
−
BF4 2 and CF SO3 3) in acetonitrile. In all cases, a pale
3
O)·0.25(CH CN)·0.25(C H ) requires: C, 40.46 H, 3.55 N,
3
6 6
1
yellow/orange solution was obtained, which upon
vapour diffusion of an appropriate anti-solvent resulted
in orange block crystals suitable for structural analysis
via single-crystal X-ray diffraction. All complexes were
susceptible to desolvation upon removal from the
mother liquor, highlighted by the TGA for 2 and 3 (TGA
for 1 was not performed as it contains perchlorate
anions). Furthermore, the elemental analysis revealed
a tendency for the complexes to undergo hydration
under ambient conditions prior to measurement.
Complex 1 was synthesised via vapour diffusion of ben-
zene into an acetonitrile solution and crystallised in the
−
11.56%, IR: (νmax/cm ) 3527 (w, br.) 290 (w, br.) 1617 (m)
1590 (w) 1554 (m) 1509 (m) 1435 (w) 1404 (w) 1381 (w)
1336 (M) 1299 (w) 1250 (w) 1213 (m) 1176 (m) 1062 (s, br.)
1000 (s) 931 (m) 871 (w) 832 (m) 786 (m) 755 (m) 621 (s)
[
Co (L) ](BF ) , 2
2 2 4 4
Co(BF ) · 6H O (8.6 mg, 23.6 μmol) was dissolved in acet-
4
2
2
onitrile (15 mL) and was stirred at room temperature.
L (10 mg, 23.6 μmol) was added to give a pale brown/
yellow suspension and stirred for approximately 5 hours to
give an orange/brown cloudy solution. The cloudy solution
was allowed to stand at room temperature for 2 hours and
then filtered to give a yellow/brown solution. Vapour diffu-
sion of diisopropyl ether into the filtrate resulted in orange
block crystals suitable for single crystal X-ray diffraction.
Found: C, 42.37 H, 3.36, N, 12.05% [Co (C H N
monoclinic space group P2 /n. The asymmetric unit is
1
comprised of two Co(II) centres bridged by two L ligands
coordinating in the expected tridentate fashion (Figure
1
, Figure 2 and S3).
2
20 24 6
Analysis of the C = O bond lengths confirms that the
O ) ](BF ) · 2.7(H O) requires: C, 42.31 H, 3.36 N, 12.36%, IR:
2
2
4 4
2
ligand is coordinating in the neutral keto form (table S2).
The relevant Co-N/O bond lengths and angles are sum-
marised in tables S3 and S4. The two high spin Co(II)
centres exist in a significantly distorted N O octahedral
−
1
(
(
(
(
(
(
νmax/cm ) 3579 (br., w), 3215 (br., w) 3048 (br., w), 1616
m), 1592 (w), 1545 (m), 1509 (s), 1436 (w), 1405 (w), 1381
m), 1337 (w), 1299 (w), 1250 (m), 1214 (w), 1177 (w), 1144
m), 1128 (m), 1017 (s), 992 (s), 936 (m), 872 (w), 835 (m), 786
m), 750 (m), 699 (w), 679 (w), 617 (w), 593 (w), 569 (w), 519
m), 486 (m)
4
2
coordination sphere with octahedral distortion para-
meters (Σ) of 152.8° and 143.3° for Co1 and Co2, respec-
tively [44]. The succinate backbones of the two ligands
are significantly twisted, resulting in the ligands adopt-
ing a helical conformation about the two Co(II) centres.
The geometric parameters for 1 are summarised in table
S5. The dinuclear double helicate in the asymmetric unit
exhibits P helical chirality while the M enantiomer is
generated via the action of the inversion centre present
in the centrosymmetric space group. The charge of the
[
Co (L) ](OTf) , 3
2 2 4
CoCl · 6H O (3.6 mg, 23.6 μmol) was dissolved in acet-
2
2
onitrile (5 mL). AgOTf (12.1 mg, 47.2 μmol) was added
resulting in the immediate formation of a white precipi-
tate. The solution was filtered into a suspension of
L (10 mg, 23.6 μmol) in acetonitrile (5 mL). The pale
brown/yellow suspension and stirred for approximately
4+
[Co (L) ] cation is balanced by four perchlorate anions,
2
2
5
hours to give an orange/brown cloudy solution. The
three of which are modelled as disordered over two
positions. We have previously reported the hydrazide
(N)H of a related pyrazinyl-hydrazone-based ligand to
be a potent hydrogen bond donor [37]. Three of the
hydrazide moieties of 1 participate in hydrogen bonding
interactions with the perchlorate anions while the fourth
participates in a hydrogen bonding interaction with
a water molecule, with (N)H···O distances ranging from
cloudy solution was allowed to stand at room tempera-
ture for 2 hours and then filtered to give a yellow/brown
solution. Vapour diffusion of m-xylene into the filtrate
resulted in orange block crystals suitable for single crys-
tal X-ray diffraction. Found: C, 38.24 H, 2.84, N, 10.39%
[
Co (C H N O ) ](CF SO ) · 3.75(H O) requires: C,
2 24 20 6 2 2 3 3 4 2
−1
3
8.30 H, 2.94 N, 10.31%, IR: (νmax/cm ) 3491 (br., w),

4
B. H. WILSON AND P. E. KRUGER
Figure 2. (colour online) Single crystal X-ray structure of 1, representative for this group of helicate complexes. Two ligands, L,
coordinate to the Co(II) centres in a tridentate manner via the quinolinyl and hydrazone nitrogen atoms and the hydrazone oxygen
atom. Hydrogen atoms, anions and solvent molecules omitted for clarity.
1
.905(6) to 2.15(1) Å (figure S6, table S6). The hydrogen
similar to 1 and are summarised in tables S3 and S4. The
atoms of the water molecule also participate in further
hydrogen bonding interactions with perchlorate anions,
resulting in the propagation of a hydrogen-bonding net-
work. This hydrogen-bonding network forms supramo-
lecular two-dimensional sheets in the crystallographic
ab-plane. The propensity of the quinoline moieties to
form intramolecular [45] and intermolecular [46–48] π-
stacked assemblies in metal hydrazone complexes is
established in the literature, the latter of which is exem-
plified by 1. Two forms of π-π stacking occur at either
end of each ligand strand of the helicate (Table S9). At
one end of a ligand strand, only the benzo rings of the
quinoline moiety over-lap with a π(centroid)···π(centroid)
separation of 3.509(4) Å. At the other end, the two
pyridyl and benzo rings of the quinoline moieties on
neighbouring complexes overlap with π(centroid)···π
high spin Co(II) centres exist in N O distorted octahedral
2
4
coordination spheres with Σ parameters of 139.9° and
136.3° for Co1 and Co2, respectively. Likewise, the succi-
nate backbone of the two ligands is significantly twisted
as detailed in table S5. Three of the hydrazide (N)H moi-
eties participate in hydrogen bond interactions with tet-
rafluoroborate anions while the fourth participates in
a hydrogen bond interaction with an acetonitrile mole-
cule, with (N)H···A (A = N, O) separations ranging from
1.871(2) to 2.277(5) Å (figure S7, table S7). In contrast to 1,
the tetrafluoroborate anions do not form bridging hydro-
gen bond interactions between neighbouring complexes,
resulting in the absence of a hydrogen bond network.
Therefore, while the anions of 1 and 2 have the same
geometry, the crystal packing is significantly different. The
predominant intermolecular interactions between neigh-
bouring complexes are via π-stacking and edge-to-face
(C)H···π interactions of the quinoline moieties. The (C)H
moiety in the 6-position of the quinoline ring forms a (C)
H···π interaction with the benzene ring of a neighbouring
quinoline moiety and vice versa in reciprocal fashion. Two
crystallographically unique pairs of this interaction occur
with H···π(centroid) separations ranging from 2.613(1) to
3.333(3) Å (Figures 3, S9 and table S10). A π-stacking
interaction occurs in a manner similar to that observed
in 1 where the two pyridine and benzene rings of the
quinoline moiety overlap to form a reciprocal interaction.
Two crystallographically unique types of this interaction
occur with π(centroid)···π(centroid) separations of 3.856(2)
and 3.744(2) Å (Figure 4). The combination of the π-
stacking and edge-to-face (C)H···π interactions results in
the formation of a two-dimensional supramolecular
sheet, similar to 1, however, with a pronounced
(
centroid) separations of 3.604(4) and 3.666(4) Å, respec-
tively (Figure 3). The propagation of these π-π stacking
interactions results in the formation of a supramolecular
two-dimensional sheet in the ac-crystallographic plane.
Complex 1 crystallised with a number of benzene and
acetonitrile solvent molecules in addition to one water
molecule, many of which are disordered and with partial
occupancy. However, only the water molecule partici-
pates in the interactions outlined above, responsible for
the observed crystal packing.
Complex 2 was synthesised via vapour diffusion of
diisopropyl ether into an acetonitrile solution and crystal-
lised in the triclinic space group P-1. The composition of
the asymmetric unit is broadly similar to 1 and contains
an isostructural dinuclear double helicate and therefore,
only a brief discussion of salient difference and similarities
will be given. The Co(II)-N/O bond lengths and angles are

SUPRAMOLECULAR CHEMISTRY
5
Figure 3. (colour online) (a) The two forms of π-π interactions occurring between the quinoline moieties on neighbouring dinuclear
helicates for 1. The π(centroid) are shown as red spheres while the π(centroid)···π(centroid) separations are shown in green and given
in Å. Hydrogen atoms, triflate anions and solvent molecules omitted for clarity. (b) The hydrogen-bonding network of 1 that results in
the propagation of a two-dimensional supramolecular sheet. The dinuclear helicates are shown in orange, the perchlorate anions in
purple and the water molecules in dark blue. The (N)H···O separations are shown in light blue. Perchlorate anions and solvent
molecules not participating in the illustrated interaction are omitted for clarity.
undulating nature. Much like 1, 2 crystallises with
a number of solvent molecules in the lattice. There are
two disordered acetonitrile solvent molecules and a water
molecule. However, only one acetonitrile molecule parti-
cipates in the hydrogen bond interactions outlined
above. The presence of acetonitrile and water molecules
is supported by TGA (figure S1). A 7.7% mass loss
between 45°C and 113°C can be attributed to complete
differences to the preceding complexes follows. The
Co(II)-N/O bond lengths and angles are broadly similar
to 1 and 2 and are summarised in tables S3 and S4. The
high spin Co(II) centres exist in N O distorted octahe-
2
4
dral coordination spheres with Σ parameters of 140.0°
and 132.0° for Co1 and Co2, respectively. Likewise, the
succinate backbone of the two L ligands is significantly
twisted as detailed in table S5. The charge balance is
provided by four triflate anions, three of which are dis-
ordered. Three of the hydrazide moieties of 3 participate
in hydrogen bond interactions with the triflate anions
while the fourth participates in a hydrogen bond inter-
action to a water molecule, with (N)H···O distances ran-
ging from 1.79(2) to 2.221(5) Å (figure S8, table S8). The
water molecule acts as a further hydrogen bond donor
to two symmetry generated triflate anions resulting in
the propagation of a hydrogen-bonding network in
desolvation of 2 · 2.8(MeCN)·0.2(H O) to give 2 (8.2%),
2
while the thermal decomposition of 2 occurs above
230°C.
Complex 3 was synthesised via vapour diffusion
of m-xylene into an acetonitrile solution and crystallised
in the triclinic space group P-1. The composition of the
asymmetric unit is broadly similar to 1 and 2 and con-
tains an isostructural dinuclear double helicate.
Therefore, only a brief discussion of similarities and

6
B. H. WILSON AND P. E. KRUGER
Figure 4. (colour online) (a) π-π and edge-to-face (C)H···π interactions occurring for 2 resulting in the propagation of a supramolecular
two-dimensional sheet with distances given in Å. The π(centroid) are shown as red spheres while the π(centroid)···π(centroid) and H···π
(centroid) separations are shown in green. Hydrogen atoms, triflate anions and solvent molecules not participating in the illustrated
interactions omitted for clarity. (b) The interdigitation of the undulating two-dimensional sheets for 2, shown alternating in orange
and green for clarity.
a similar fashion to 1. This results in the formation of
a hydrogen-bonding chain running approximately par-
allel to the crystallographic c-axis (Figure 5). In a similar
fashion to 2, the quinoline moieties of 3 participate in
both π-π stacking and edge-to-face (C)H···π interactions
acetonitrile molecules in the lattice, however, only one
water molecule participates in the interactions outlined
above, responsible for the observed crystal packing. This
solvent content is supported by TGA analysis (figure S2).
A gradual mass loss of 21.1% occurs between 73°C and
173°C followed by a more rapid mass loss of 3.8%
between 207°C and 258°C. It is postulated that upon
the removal of the crystals from the mother liquor, 1.5
acetonitrile molecules are lost to give 3 · 1.5(MeCN)·2(H2
O). The loss of two water molecules constitutes a mass
loss of 2.1% to give 3 · 1.5(MeCN), followed by the loss of
1.5 acetonitrile molecules which constitutes a mass loss
of 3.7% to give fully desolvated 3. A rapid mass loss
occurs after 360°C due to complex decomposition.
(
figure S10, Table S11). Two forms of π-staking interac-
tions between neighbouring complexes are present. The
first occurs with a π(centroid)···π(centroid) separation of
3
.556(3) Å. The second occurs with a π(centroid)···π(cen-
troid) separation of 3.836(3) Å in conjunction with an
edge-to-face C-H···π interaction. The combination of
these two π-stacking interactions results in the forma-
tion of a two-dimensional supramolecular sheet.
Complex 3 crystallises with a number of water and

SUPRAMOLECULAR CHEMISTRY
7
Figure 5. (colour online) The hydrogen-bonding network of 3 resulting in the propagation of a one-dimensional supramolecular chain. The
dinuclear helicate units are shown in orange, the triflate anions in purple and the water molecules in dark blue. The (N)H···O and (O)H···O
separations are shown in light blue. Triflate anions and solvent molecules not participating in the illustrated interactions are omitted for clarity.
To compare the intermolecular interactions of the com-
plexes in a more quantitative manner, the Hirshfield sur-
faces [49–51] for 1, 2 and 3 were calculated using Crystal
Explorer [52]. Mapping the dnorm (normalised contact
distance) onto the Hirshfield surface reveals the common-
ality in the hydrogen bonding of the hydrazide moiety of all
three complexes (Figures 6 and S11). Contacts with external
molecules shorter than the sum of the Van de Waals radius

8
B. H. WILSON AND P. E. KRUGER
Figure 6. (colour online) (a) The single-crystal x-ray structure and d
mapped onto the Hirshfield surface of the dinuclear helicate
norm
4+
[
Co (L) ] in 1. The red region of the Hirshfield surface (dnorm shorter than sum of Van de Waals radii) corresponds to the (N)H
2 2
hydrogen bond donor moiety. (b) The 2D fingerprint plot of 1 highlighting the regions corresponding to the three intermolecular
interactions of interest: (N)H···O hydrogen bonding, (C)H···π and π···π interactions. High frequency of d and d separation is shown in
e
i
pale green while low frequency dark blue. Hirshfield surface and 2D fingerprint plot were generated using Crystal Explorer [52].
are represented as red areas on the surface in the case of
complex 1, 2 and 3 occur around the (N)H moiety of the
hydrazide which act as a hydrogen bond donor. Contacts
with external molecules greater than the sum of the Van de
Waals radius are shown in blue. The normalised contact
fluorine atoms as the hydrogen bond acceptors, there is
a more diffuse single peak pattern arising from
H(internal)···O(external)
separations.
Furthermore,
a contribution to this diffuse peak pattern is also observed
from the H(internal)···N(external) separations due to the
presence of an acetonitrile molecule behaving as
a hydrogen bond acceptor to a (N)H hydrazide moiety. In
comparison, while 1 contains and acetonitrile solvent mole-
cule in the lattice, it does not act as a hydrogen bond
acceptor and therefore does not contribute to the peak
distance is defined by two parameters: d (the distance
e
from the surface to the nearest external nucleus) and di
(the distance from the surface to the nearest internal
nucleus of the molecule). The frequency of every d and d
e
i
combination can be summarised in a 2D fingerprint plot
(Figures 6 and S12) which can be broken down by element
pattern at low de and d values. Visualisation of the
i
type for clearer analysis of the intermolecular interactions.
H(internal)···C(external) and C(internal)···C(external) can be
used to compare the (C)H···π and π···π interactions (Figure
S14). Complexes 2 and 3 feature similar distributions of
H(internal)···C(external) and C(internal)···C(external) separa-
tions, commensurate with the similar (C)H···π and π···π inter-
actions occurring in the three structures. In the case of 1, the
The 2D fingerprint plots for all d and d interactions for 1, 2
e
i
and 3 have some similar features due to the shared types of
interactions occurring between the complexes in the lat-
tice. In particular, all the complexes share pronounced
‘
peaks’ at low d and d values, characteristic of hydrogen
e i
bonding interactions. To further analyse the 2D fingerprint
distribution
of
H(internal)···C(external)
and
plot several d and d combinations of different element
C(internal)···C(external) separations is larger which can be
rationalised by the presence of benzene molecules in the
structure which makes a signification addition to the
H(internal)···C(external) and C(internal)···C(external) separa-
tions which are otherwise similar to 2 and 3. Therefore,
when quantifying the intermolecular interactions based
on the 2D fingerprint plots of larger supramolecular assem-
blies, care must be taken to consider all molecules in the
crystal lattice and not just the complex and counter anions
of interest.
e
i
types were visualised (figures S13 and S14). Visualisation of
the H(internal)···A(external) where A is a suitable hydrogen
bond acceptor can be used to analyse hydrogen
bonding interactions. For complexes 1 and 3, the
H(internal)···O(external) separations contribute to a similar
double-peak pattern in the 2D fingerprint plot, predomi-
nantly through the (N)H···O hydrogen bonding interactions
of the hydrazide moieties with the perchlorate (1) or triflate
(2) anions (figure S13). However, in 3 which features

SUPRAMOLECULAR CHEMISTRY
9
Conclusion
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(
In conclusion, were reported the synthesis and structural
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tallisation had a drastic effect on the crystal packing of the
[
[
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−
−
complexes. In particular, despite ClO4 and BF4 posses-
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different, resulting in significantly different crystal pack-
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noline ring system towards π-π stacking resulted in the
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Disclosure statement
helicate
complexes.
Dalton
Trans.
2018;47
There are no conflicts to declare.
(
24):7965–7974.
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Funding
This work was supported by the MacDiarmid Institute for
Advanced Materials and Nanotechnology; Royal Society of
New Zealand [Marsden Fund]; University of Canterbury
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[Roper Scholarship].
ORCID
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Benjamin H. Wilson
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