Investigating the solid state hosting abilities of homo- and hetero-valent [Co7] metallocalix[6]arenes

Article abstract of DOI:10.1039/c2dt12229d

A family of homo-valent [Co(ii)₇(OH)₆(L ₁)₆](NO₃)₂ (1), [(MeOH) ₂?Co(ii)₇(OH)₆(L₁) ₆](NO₃)₂ (2) (where L₁H = 2-iminomethyl-6-methoxyphenol) and hetero-valent [(NO₃) ₂?Co(iii)Co(ii)₆(OH)₆(L₂) ₆](NO₃)·3MeCN (4) (where L₂H = 2-iminophenyl-6-methoxyphenol) complexes possess metallic skeletons describing planar hexagonal discs. Their organic exteriors form double-bowl shaped topologies, and coupled with their 3-D connectivity, this results in the formation of molecular cavities in the solid state. These confined spaces are shown to behave as host units in the solid state for guests including solvent molecules and charge balancing counter anions. Magnetic susceptibility measurements on 2 and 4 reveal weak ferro- and ferrimagnetism, respectively. The utilisation of other Co(ii) salt precursors gives rise to entirely different species including the mononuclear and trinuclear complexes [Co(ii)(L ₂)₂] (5) and [Co(iii)₂Na(i)₁(L ₃)₆](BF₄) (6) (where L₃H = 2-iminomethyl-4-bromo-6-methoxyphenol).

Full text of DOI:10.1039/c2dt12229d

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PAPER
Investigating the solid state hosting abilities of homo- and hetero-valent [Co7]
metallocalix[6]arenes†
a
a
a
b
b
Seán T. Meally, Cecelia McDonald, Patrick Kealy, Stephanie M. Taylor, Euan K. Brechin and
a
Leigh F. Jones*
Received 21st November 2011, Accepted 14th February 2012
DOI: 10.1039/c2dt12229d
A family of homo-valent [Co(II) (OH) (L ) ](NO ) (1), [(MeOH) ⊂Co(II) (OH) (L ) ](NO ) (2)
7
6
1 6
3 2
2
7
6
1 6
3 2
(
where L H = 2-iminomethyl-6-methoxyphenol) and hetero-valent [(NO ) ⊂Co(III)Co(II) (OH) (L ) ]-
1
3 2
6
6
2 6
(
NO )·3MeCN (4) (where L H = 2-iminophenyl-6-methoxyphenol) complexes possess metallic skeletons
3
2
describing planar hexagonal discs. Their organic exteriors form double-bowl shaped topologies, and
coupled with their 3-D connectivity, this results in the formation of molecular cavities in the solid state.
These confined spaces are shown to behave as host units in the solid state for guests including solvent
molecules and charge balancing counter anions. Magnetic susceptibility measurements on 2 and 4 reveal
weak ferro- and ferrimagnetism, respectively. The utilisation of other Co(II) salt precursors gives rise to
entirely different species including the mononuclear and trinuclear complexes [Co(II)(L ) ] (5) and
2
2
[
Co(III) Na(I) (L ) ](BF ) (6) (where L H = 2-iminomethyl-4-bromo-6-methoxyphenol).
2
1
3 6
4
3
1
2
rarity and potential applications as multifunctional magnetic
Introduction
13
materials. To this end we recently reported a family of hepta-
nuclear [M ] (M = Ni(II), Zn(II)) pseudo metallocalix[6]arene
host–guest complexes whose self-assembled double-bowl topol-
ogies resulted in molecular cavities able to accommodate various
The design and synthesis of self-assembled molecular flasks and
containers capable of encapsulating smaller guest molecules con-
tinues to fascinate the scientific community. This is due to their
potential applications in both the solution and solid state.
7
1
14
guest solvent molecules.
2
Examples of their use in solution include anion sensing and
Herein we present an extension of this work by showing that
we are now able to produce the cobalt analogues of this family
and for the first time encourage solid state molecular cavity
ingression of anionic guests using a mixed-valence [Co(III)-
3
4
sequestration, catalytic organic transformations, enzyme
5
6
7
mimetics, drug delivery and medical diagnostics. In the solid
state interests lie in their potential as gas storage and separation
8
vessels, and as containers for magnetic nanoparticles towards
Co(II) ] double-bowl. Crystallographic information on com-
6
9
imaging. Indeed both organic and metal–organic molecular
plexes 1–4 and 5–6 are documented in Table 1 and S1† respect-
ively. Bond valence sum (BVS) calculations are provided in
Table S2†.
1
5
flasks/containers are well known in the literature. Their for-
mations are driven by a synergistic combination of non-covalent
interactions (π–π stacking, H-bonding, ion pairing etc.) in the
former, and a subtle blend of covalent (metal–ligand bonding)
and non-covalent pairings in the latter. The well reported bowl-
Results and discussion
1
0
like calix[n]arene cyclophanes (n = 3, 4, 5, 8 etc.) and their
Firstly we highlight the synthesis and characterisation of the
double-bowl complexes [Co(II) (OH) (L ) ](NO ) (1) and
(MeOH) ⊂Co(II) (OH) (L ) ](NO ) (2) (Fig. 1 and 2), built
using the ligand 2-iminomethyl-6-methoxyphenol (L H)
11
metallocalix[n]arene structural relations are examples that high-
light these differences. Moreover, both of these classes of
materials have been reported in the literature to exhibit many of
the applications noted above.
7
6
1 6
3 2
[
2
7
6
1 6
3 2
1
(
Scheme 1 (top)). The molecular cavities remain empty in 1
Our own work in this field details the solid state guest engage-
ment of highly paramagnetic polynuclear host units, due to their
while they are able to accommodate MeOH guests in 2. Both
complexes comprise a central Co(II) ion (Co1) surrounded by six
outer ring Co(II) ions (Co2 and symmetry equivalent, s.e.),
−
a
which are all connected via μ -bridging OH anions (O1 and
3
School of Chemistry, National University of Ireland Galway, University
s.e.) to form a planar, body-centred, hexagonal core. This
Road, Galway, Ireland. E-mail: leigh.jones@nuigalway.ie; Tel: +353
0
91-49-3462
{Co(II) } topology is known in the literature, however no solid
7
b
16
EaStCHEM School of Chemistry, Joseph Black Building, University of
Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, Scotland
†
state host–guest properties have been described previously. The
−
six singly deprotonated L ligands bridge the six outer Co(II)
1
Electronic supplementary information (ESI) available. CCDC
1
2
1
ions via the η :η :η :μ-bonding motif. These ligands sit alternately
8
43603–843606, 854829 and 854830. For ESI and crystallographic data
8+
in CIF or other electronic format see DOI: 10.1039/c2dt12229d
above and below the {Co(II) (OH) } plane to form a pseudo
7 6
5610 | Dalton Trans., 2012, 41, 5610–5616
This journal is © The Royal Society of Chemistry 2012

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Table 1 Crystallographic data for complexes 1–4
1
2·2MeOH
3
4·3MeCN
a
Formula
C
54
H
66
N
8
O
24Co
7
C
56
H
66
N
8
O
26Co
7
C
14
H13NO
2
90 87 12 7
C H N O27Co
M
W
1623.66
Trigonal
P3ˉc1
1679.68
Trigonal
P3ˉc1
227.25
Orthorhombic
P2
2181.23
Monoclinic
/c
Crystal system
Space group
1
2
1
2
1
C
2
a/Å
b/Å
c/Å
α/°
β/°
γ/°
V/Å
14.110(2)
14.110(2)
22.770(5)
90
90
120
14.041(2)
14.041(2)
23.036(5)
90
90
120
6.0471(6)
9.0763(12)
20.933(3)
90
90
90
29.2767(15)
12.9879(5)
24.4043(9)
90
92.797(2)
90
3
3926.0(11)
2
3933.1(11)
2
1148.9(3)
4
9268.5(7)
4
Z
T/K
150(2)
0.7107
1.373
1.511
150(2)
0.7107
1.418
1.513
150(2)
0.7107
1.314
150(2)
0.7107
1.563
b
λ /Å
D
c
/g cm−
3
−1
μ(Mo-Kα)/mm
0.088
1.306
Meas./indep. (Rint) refl.
2353/1767(0.0295)
0, 143
0.2796
0.0851
1.211
2362/2188(0.0184)
2, 153
0.2221
0.0695
1.194
2000/1347(0.0486)
0, 143
0.1874
0.0751
1.015
8489/5388(0.0684)
2, 617
0.1693
0.0697
1.052
Restraints, parameters
c
wR
2
(all data)
d,e
R
1
2
Goodness of fit on F
a
b
c
2
o
2
2
2 2 1/2
d
e
Includes guest molecules. Mo-Kα radiation, graphite monochromator. wR
2
= [∑w(|F
| − |F
c
|) / ∑w|F
o
| ]
.
For observed data.
R
1
o
= ∑||F |
−
c o
|F || / ∑|F |.
Fig. 2 Space-filled representations of the two crystallographically
unique guest MeOH molecules lying within the molecular cavities
formed by two double-bowl [Co(II) ] units in complex 2.
7
Fig. 1 (a) Crystal structure of 1 as viewed perpendicular (a) and paral-
lel (b) to the planar {Co(II) } core. (c) Schematic representation of the
EtOH molecules cannot satisfy the three-fold symmetry pattern
7
double-bowl topology in 1 and its analogues. Colour code (used
throughout this work): purple (Co), red (O), blue (N), grey (C). H-atoms
and anions omitted for clarity.
shown by the linear MeOH guests in 2, as dictated by their iden-
tical P3ˉ1/c space groups). This is consistent with that observed
for the Ni(II) and Zn(II) analogues. Complexes 1 and 2 crystal-
lise in the trigonal P3ˉc1 space group and only differ in terms of
14
their guest occupancy and therefore are analogous with respect
metallocalix[6]arene double-bowl (Fig. 1b and c). Crystallo-
graphic inspection of these molecular bowls shows dimensions
to their packing arrangement (Fig. 3). The 1D [Co(II)
in their unit cells are connected via H-bonds to adjacent [Co(II)
stacks ([Co(II) plane distances: 11.39 (1) and
11.52 Å (2)), propagated by multiple interactions between the
7
] columns
]
7
(base × depth × rim diameter) of (Å): 6.27 × 3.96 × 12.89 (1)
7
]
plane⋯[Co(II) ]
7
and 6.25 × 4.08 × 12.12 (2), respectively.
−
The molecular cavities formed by the 1D pseudo superimpo-
sable columns in the crystal of 2 act as molecular hosts by
encapsulating two disordered MeOH guest molecules which are
sequestered from the reaction medium. The first methanol guest
is disordered over three sites, lying on the 3-fold axis that runs
NO
3
counter anions and the individual [Co(II) ] moieties (e.g.
7
O4⋯H5(C5) = 2.406 Å in 1; O4⋯H7(C7) = 2.431 Å in 2).
More specifically each heptanuclear unit is H-bonded to twelve
−
NO
counter anions which in turn connect to six other [Co(II)
]
3
7
15
48 18
units thus creating (6,12)-connected nets with (4 )
topologies.
(4 .6 )-alb
2
perpendicular to the [Co(II) ] plane through the central Co(II)
7
centre. The second MeOH guest has 2-fold disorder and lies at
the boundary of the molecular cavity in 2, sitting perpendicular
In order to further probe the hosting abilities of the heptanuc-
lear hosts and to attract more intriguing guests, we decided to
to the [Co(II) ] plane (Fig. 2). Interestingly the molecular cavities
modify L
H at the imine position via introduction of a phenyl
1
7
in 1 remain guest free, choosing not to accommodate EtOH
solvent molecules – presumably due to steric effects and/or crys-
tallographic restraints (i.e. perhaps the kinked nature of the
group, in order to modulate its second order coordination sphere
2+
behaviour upon primary {M(II)
(OH) (L) }
7 6 6
planar disc for-
H (3))
mation. The ligand 2-iminophenyl-6-methoxyphenol (L
2
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Fig. 4 Crystal structure of the mixed-valent complex [(NO
3 2
) ⊂Co(III)-
Co(II) (OH) (L ](NO )·3MeCN (4) as viewed parallel (left) and per-
6
6
2
)
6
3
−
pendicular (right) to the {Co(III)Co(II)
6
} plane. Guest NO
3
anions are
space-fill represented.
Scheme 1 Top: Schematic of the ligands L
Br) used in this work. Bottom: Crystal structure of the ligand 2-imino-
phenyl-6-methoxyphenol (L H (3)) as viewed perpendicular (left) and
along the plane (right) of the phenolic ring. Colour code: grey (C), blue
N), red (O), black (H). Majority of the hydrogen atoms omitted for
clarity. Dashed line represents the intramolecular H-bonding interaction
in L H, measured at O1A(H1A)⋯N1 = 1.887 Å.
1 3
H (R = H) and L H (R =
2
(
2
Fig. 5 View of a NO −
Co(III)Co(II) ] unit in 4. Intermolecular interactions between the host
anion occupying one half of a double-bowl
3
[
6
and guest are represented as dashed lines. Actual distances are given in
the main text.
Complex 4 (Fig. 4) differs to its [M(II) ] siblings in that its
7
central Co ion is in the +3 oxidation state, as confirmed by bond
length and charge balance considerations and BVS analysis
(
{
Table S2†). The metal–oxygen core of the molecule is thus
9+
Co(III)Co(II) (OH) } . As a result of this extra +1 charge,
6 6
−
complex 4 is able to accommodate two of its three counter NO3
anions within its double-bowl cavities which is driven by the
resultant {Co(III)Co(II) (OH) (L ) } ⋯NO electrostatic inter-
3+
−
6
6
2 6
3
Fig. 3 Left: Packing observed in [Co(II)
viewed down the c axis of the unit cell, highlighting the 1D columns
observed in (and 2). Right: Crystal packing observed in
(MeOH) ⊂Co(II) (OH) (L ](NO (2). The MeOH guests are space-
fill represented.
7 6 1 6 3 2
(OH) (L ) ](NO ) (1) as
actions. Indeed this observation is a first for such pseudo metal-
localix[6]arene systems. It should also be noted that complex 4
1
is the only polymetallic complex to be isolated using ligand L H
[
2
7
6
)
1 6
)
3 2
2
(
3), having previously produced only monomeric species of Re,
18–20
The two symmetry equivalent NO3− guests are
Ru and Co.
held in position via their O-atoms (O10–12) by four interactions
can be easily synthesised (see the Experimental section for
details) through the Schiff base condensation of o-vanillin and
aniline. L H crystallises in the orthorhombic P2 2 2 space
group (Z = 4) and possesses an intramolecular H-bond between
the phenolic proton (H1A) and the imine nitrogen atom (N1),
giving a distance of O1A(H1A)⋯N1 = 1.887 Å and hydrogen
bond angle of 144.9°. Furthermore the imino-phenyl and phenol
in the form of two long C–H⋯O contacts from the phenyl ring
−
of the L
ligands (C28(H28)⋯O11 = 2.969 Å; C38(H38)
2
⋯O10 = 2.653 Å) and three H-bonds formed with donor protons
2
1 1 1
−
(H1, H2 and H3H) of the bridging μ
-OH ions within the {Co(III)-
3
Co(II) } core (O1(H1)⋯O11 = 2.280 Å; O2(H2)⋯O11 =
6
1.916 Å and O3(H3H)⋯O10 = 1.802 Å), giving H-bond angles
of 123.60, 146.98 and 170.50°, respectively (Fig. 5). The
C–H⋯O interactions described here are made possible by the
rings of L H (as perhaps expected) twist away slightly from one
2
another (via the imine bridge) to give a staggered conformation
with a torsion angle (C10–C9–N1–C8) of 30°. Although struc-
staggered conformation of the two aromatic rings (phenolic
−
versus imine-phenyl) of each L
ligand upon metallation
2
tural analogues to L H (3) have been crystallographically
(torsion angles now ranging from ∼49 to 76° cf. 30° in unbound
H); thus giving rise to a more distorted double-bowl shape
compared to our [M(II) ] analogues. Moreover the role of the
imine-phenyl groups in 4 should not be underestimated in terms
of driving the observed anion inclusion, thus highlighting the
importance of ligand choice/design and the resulting cavity size
and shape in this work.
2
17
reported with various substituents on the imino-phenyl ring,
we present here the first crystal structure of this particular ligand
Scheme 1). Upon reaction with Co(NO ) ·6H O and NaOH in
L
2
7
(
3
2
2
MeOH the first example of a mixed-valence analogue of our [M
II) ] double-bowl pseudo metallocalix[6]arenes, [(NO ) ⊂Co(III)
(
7
3 2
Co(II) (OH) (L ) ](NO )·3MeCN (4), is formed.
6
6
2 6
3
5612 | Dalton Trans., 2012, 41, 5610–5616
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Fig. 7 Crystal structure of [Co(II)(L
2
2
) ] (5) highlighting the close
proximity of neighbouring monomers within the H-bonded chains (left)
and between the chains (right). H-bonding shown using dashed lines.
Fig. 6 Crystal packing illustrations of 4 as viewed across the ab plane
−
(left) and down the a axis (right) of the unit cell. Only guest NO
3
anions are shown here (in space-fill mode).
In terms of intermolecular connectivity between the individual
[
Co(III)Co(II) ] units the O-atoms (O12 and s.e.) of the guest
6
−
NO3 anions form close contacts with aromatic (H10) and ali-
phatic (H29C) ligand protons (C10(H10)⋯O12 = 2.439 Å, C29
−
(
H29C)⋯O12 = 2.627 Å). The third NO3 counter ion lies
outside the confines of the double-bowls and acts as another con-
nector of multiple [Co(III)Co(II) ] units via C–H⋯O interactions,
6
through the aromatic ligand protons (H3, H4 and H21) at dis-
tances of C3(H3)⋯O14′ = 2.449 Å, C4(H4)⋯O14 = 2.564 Å
and C21(H21)⋯O13 = 2.357 Å. Interestingly the individual
double-bowl [Co(III)Co(II) ] units in 4 do not stack upon one
6
another to form the enclosed molecular cavities observed in the
1
4
related [M(II) ] host–guest analogues. Instead these units lie
7
perpendicular to one another within the unit cell and pack in
wave-like rows along the c-axis. These individual rows arrange
in a parallel fashion along the a direction of the unit cell with
alternating wave phases (Fig. 6). Complex 4 is only the second
2
1
mixed-valence {Co(III)Co(II) } structure to be reported and is
6
the first to show such solid state host–guest behaviour. Interest-
ingly the formation of 4 in relation to 1 and 2 represents (to our
knowledge) the first example whereby Co(II) oxidation is
observed while the exact polymetallic core structure is retained.
The production of 4 prompted our focus to shift towards solid
state guest inclusion of other counter anions using our [Co(III)-
Fig. 8 Crystal structures of [Co(III) Na(I) (L ) ](BF ) (6) as viewed
2
1
3 6
4
perpendicular (top) and parallel (bottom) to the V-shaped plane of the
molecule. Colour code: purple (Co), yellow (Na), red (O), blue (N),
green (Br) and grey (C). H-atoms and anions omitted for clarity.
interacting with four near monomeric neighbours. The superim-
posable rows propagating along c are also involved in inter-
chain H-bonding (along the ab cell plane), again using aromatic
2+
2−
Co(II)(L ) ] “vessel”. The first candidate was the O-rich SO4
2
6
anion in the hope of interaction with our H-rich planar core (con-
taining six OH− bridges). We were also curious to know what
would occur when we added a doubly negative anion. However
−
L2 protons (H18, H8) and Ophen (O2) and OMe (O4) donor
atoms (C18(H18)⋯O2′ = 2.571 Å; C8(H8)⋯O3′ = 2.491 Å)
(Fig. S2†).
2
−
SO4 cavity ingression was not observed. Indeed the synthesis
of [Co(II)(L ) ] (5) (crystallising in the monoclinic P2 /c space
Undeterred by the unexpected production of 5, we decided to
2
2
1
attempt to incorporate the tetrahedral BF4− counter anion within
group upon reaction of CoSO ·7H O, L H and NaOH in MeOH)
4
2
2
does not contain our anion and instead comprises a single dis-
torted tetrahedral Co(II) ion (Co1) bound by two crystallographi-
cally unique L2− ligands. These ligands chelate the Co(II) ion via
their imine N atoms (N1 and N2) and Ophen atoms (O2 and O4)
with bite angles of 94.32° (N1–Co1–O2) and 96.51° (N2–Co1–
O4). The {Co(II)(L ) } moieties in 5 are arranged in superimpo-
the {Co(II/III) } complexes of 1, 2 and 4 by repeating their
7
general synthetic preparations using the Co(BF ) ·6H O salt pre-
4
2
2
cursor. Our thoughts were that by incorporating this particular
anion we would perhaps: (1) modify the crystal space group and
the size and shape of the resultant molecular cavity and/or (2)
−
2
2
encourage the proton-acceptor F-atoms of the BF4 anion to
occupy the molecular cavities via interactions with the OH−
bridging protons located within. However, this approach again
failed, and instead the complex [Co(III) Na(I) (L ) ](BF ) (6)
sable rows along the c axis of the unit cell. These are held
together via multiple H-bonds between aromatic protons (H11
−
and H12 from same L ) and O
(O2) and OMe (O3) oxygen
2
phen
2
1
3 6
4
atoms as shown in Fig. 7 (O2⋯H11′(C11′) = 2.660 Å;
2.568 Å). On closer inspection the
H-bonding in 5 is extensive with each monomeric unit
was formed. Complex 6 (Fig. 8) crystallises in the monoclinic
C2/c space group in ∼25% yield and comprises a V-shaped
metal–oxygen core whereby a central Na(I) ion (Na1) sits in
O3⋯H12′(C12′)
=
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Fig. 9 Crystal packing observed in 6 as viewed along the c axis.
Hydrogen atoms omitted for clarity. Colour code: yellow (Na), purple
(Co), red (O), dark blue (N), grey (C), green (Br), dark green (B), light
blue (F).
between two Co(III) centres (Co1 and s.e.). Six L3− ligand units
bridge the {Co(III) Na(I)} core in 6, two of which chelate the
2
Co(III) ions (bite angle: N2–Co1–O4 = 91.36°); one per crystallo-
−
graphically unique ion. The remaining four L ligands bridge
3
Fig. 10 Plots of χ
M
T vs. T obtained from polycrystalline samples of 2
1
2
1
the Co(III) –Na(I) vertices, two via the η :η :η :μ-coordination
(
●) and 4 (○) measured in an applied field of 0.1 T. Inset: Plot of
M/Nμ vs. H/T for 2 (●) and 4 (○) at 2, 4 and 7 K, in fields between
.5–7.0 T. Solid lines are a guide to the eye
1
2
−
mode and two via the η :η :μ-bridging mode (Fig. 8). The BF
4
B
anions in the unit cell of 6 sit above the central Na(I) centres
0
(
B1⋯Na1 = 4.537 Å) and partake in hydrogen bonds via the
ligand protons (H18B and H8) and the F-atoms (F1 and F2) with
Solution studies on 2 and 4
distances of F1⋯H18B(C18) = 2.915 Å and F2⋯H8(C8) =
2
.442 Å. These interactions along with their symmetry equiva-
UV-visible solution studies on 2 and 4 in MeCN and MeOH
each show transitions at ∼260, ∼230 and ∼200 nm and are
indicative of π → π* excitations. Absorptions observed at wave-
lengths centred on the 350–365 nm region in both MeOH and
MeCN solutions of 2 and 4 are attributed to n → π* excitations
lents effectively connect the individual {Co(III) Na(I)} units in 6
2
which pack in the common brickwall fashion along the ab plane
of the unit cell. These 2-D sheets then lie parallel to one another
along the c axis and each is inverted with respect to their neigh-
bouring wall (Fig. 9).
(Fig. S5 and S6†). ESI-MS measurements on a MeOH solution
of 2 gave a parent peak at m/z = 777.8 which is consistent with
2+
the [Co(II) (OH) (OMe) (L ) ] fragment. Indeed similar brid-
7
2
4
1 6
Magnetic susceptibility studies
ging ligand substitutions have been observed in previously
16b
reported analogues.
The behaviour of 4 in a MeCN solution
Magnetic susceptibility studies on 2 and 4 were performed in the
gave rise to major fragments at (m/z) 623.7, 966.6 and 1995.1,
5
–300 K temperature range in an applied field of 0.1 T (Fig. 10).
which are attributed rather neatly to the presence of the [Co(III)
Both show similar behaviour at high temperatures with broad
maxima (at ∼100 K) reflecting the effects of spin–orbit coupling.
At ∼40 K however the two curves diverge. For 2 the value of
3
+
2+
Co(II) (OH) (L ) ] , [Co(III)Co(II) (OH) (L ) ]+(NO )}
and
respectively
Fig. S7†). It should be noted here that although the solubility of
6
6
2 6
6
+
6
2 6
3
[
(
Co(III)Co(II) (OH) (L ) ]+(NO ) }
species,
6
6
2 6
3 2
χ T increases with decreasing temperature reaching a value of
M
3
−1
1, 2 and 4 (and all other previously reported [M(II) ] (M = Ni,
7
∼
20.2 cm K mol at 5 K, suggestive of weak ferromagnetic
exchange, while that for 4 decreases with temperature reaching
Zn) siblings) were adequate for UV-vis and MS evaluations,
their poor solubility at higher concentrations unfortunately rules
out any solution state host–guest measurements (i.e. NMR titra-
tion studies).
3
−1
∼
13.9 cm K mol at 5 K, indicating weak antiferromagnetic
exchange. This analysis is corroborated by examining the
low temperature field-dependence of the magnetisation (Fig. 10
–
inset) which shows that for the same temperature and field, the
magnetization value of complex 2 is always larger than that of
complex 4. An examination of the crystal structure of 4 reveals
Conclusions
that the Co–O–Co angles in the magnetic [Co(II) ] wheel fall
The production of the metallocalix[6]arene [Co(II) ] discs 1 and
6
7
into two distinct categories: those on the outer rim (OR) are in
the range 105.5–107.4° and those on the inner rim (OH) are in
the range 95.5–96.3°. The former are expected to propagate anti-
ferromagnetic interactions and the latter ferromagnetic inter-
2 highlights the consistent and reproducible nature of our
recently reported [M(II) ] (M = Co, Ni, Zn) family of host–guest
7
14
complexes. Indeed the reproducibility, stability and retainment
of this core topology, despite moving across the 1st row of the
22,23
23
actions.
On moving from complex 4 to complex 2 the inner
d-block, is extremely rare with respect to polynuclear assemblies.
rim μ -bridging OH ions now also bridge to the paramagnetic
central ion and these Co–O–Co angles are also in the range
By varying the ligand employed we are able to encourage the
accommodation of guest anionic species and the formation of
analogous compounds containing different oxidation state distri-
butions (e.g. complex 4). These changes also have a dramatic
effect upon the observed magnetic properties, switching antifer-
romagnetic exchange in the mixed-valence complex to ferromag-
netic exchange in the homo-valent complex. Attempts at
3
(94.0–98.0°) expected for ferromagnetic exchange. The con-
clusion therefore is that the larger outer rim angles dominate the
exchange in 4 leading to overall weak antiferromagnetic
exchange but the larger number of smaller inner rim angles
present in 2 result in global ferromagnetic exchange.
5614 | Dalton Trans., 2012, 41, 5610–5616
This journal is © The Royal Society of Chemistry 2012

View Article Online
replacing the anion failed, and instead gave rise to the very
different complexes 5 and 6. These latter findings highlight the
fine balance that exists between the formation of different com-
plexes and how the identity of the product is dependent upon (1)
the starting materials present (the type and the number), (2) the
reaction conditions and (3) the crystallisation methods. In this
particular case it is apparent that the presence of the NO3− anion
(m), 1438(m), 1407(w), 1334(m), 1304(m), 1241(m), 1221(s),
1168(w), 1091(w), 1073(m), 1032(m), 1012(m), 959(m), 858
(w), 829(w), 784(w), 743(s), 683(w). UV/vis data [λmax, nm (εm,
3
3
−1
−1
10 dm mol cm ) in MeOH: 352 (20.4), 262 (44.6), 233
(90.8); [CH CN]: 352 (20.3), 262 (48.8), 230 (107.3), 200
3
(107.7).
has significant bearing on [Co ] double-bowl pseudo metallo-
7
calix[6]arene formation.
Preparation of 2-iminophenyl-6-methoxyphenol (L H) (3)
2
17b
Modified from published methods: To a solution of o-vanillin
Experimental section
3
(
2.0 g, 13.14 mmol) in EtOH (40 cm ) was added distilled
3
aniline (2.0 cm , 21.94 mmol), yielding a bright orange solution.
Variable-temperature, solid state direct current (dc) magnetic sus-
ceptibility data down to 1.8 K were collected on a Quantum
Design MPMS-XL SQUID magnetometer equipped with a 7 T
dc magnet. Diamagnetic corrections were applied to the
observed paramagnetic susceptibilities using Pascal’s constants.
Each sample was encased in an Eicosane matrix to prevent tor-
quing. CHN microanalysis was carried out at the School of
Chemistry, NUI Galway. ESI-MS was carried out using a Waters
LCT Premier XE system coupled with a Waters E2795 separ-
ations module.
The solution was refluxed for 2 hours after which the solvent
was removed in vacuo. This yielded a dark orange oil. To the oil
3
was added a 1 : 1 Et O–acetone mix (total volume of 50 cm )
2
and the solvent again removed in vacuo. The dark orange oil per-
3
sisted and thus Et O (50 cm ) only was added to the oil yielding
2
a golden orange solution. The desired solid product (bright
orange) soon began to crystallise out of solution. The mixture
was placed in a fridge overnight (at a temperature of ∼2–3 °C) to
encourage further crystallisation of the desired product. The
solid was isolated via filtration over a sintered glass frit and
All solvents and reagents were used as received without
further purification. Caution: Although no problems were
encountered in this work great care must be taken when working
with the potentially explosive nitrate salts.
washed with the minimum volume of cold Et O. The product
2
was received as bright orange crystalline blocks/plates in 83%
yield. Elemental analysis calculated for C H N O (%): C
14 13 1 2
7
3.98, H 5.77, N 6.17; found: C 73.64, H 5.36, N 5.77. FT-IR
−1
(
cm ): 2955(w), 2909(w), 2837(w), 1612(s), 1586(m), 1462(s),
1409(w), 1361(w), 1329(w), 1250(s), 1194(s), 1090(w), 1075
m), 1023(w), 999(w), 966(s), 910(w), 886(w), 857(w), 832(w),
[
Co(II) (OH) (L ) ](NO ) (1)
7 6 1 6 3 2
(
3
3
To a conical flask (100 cm ) containing 30 cm of EtOH was
1
8
10(m), 781(s), 765(s), 735(s), 724(s), 689(s). H NMR:
added Co(NO ) ·6H O (0.25 g 0.86 mmol), NaOH (0.034 g,
3
2
2
(
500 MHz, CDCl ): δ 13.60 (s, 1H, OH), δ 8.62 (s, 1H, H–
3
0
0
2
.86 mmol) and 2-iminomethyl-6-methoxyphenol (0.14 g,
.86 mmol). The resultant dark purple solution was agitated for
h and then filtered. Purple hexagonal crystals of 1 were
CvN), δ 7.66 (m, 8H, Ar), δ 2.95 (s, 3H, CH –O). UV/vis data
3
3
3
−1
−1
[
(
λmax, nm (ε , 10 dm mol cm )] in MeOH: 312 (16.8), 278
m
13.2), 225 (25.5); [CH CN]: 309 (17.6), 277 (17.5), 226 (30.7),
3
obtained upon slow evaporation of the filtrate after 1 week in 5%
yield. Elemental analysis calculated for C H N O Co (%): C
2
07 (25.1).
5
4
66
8
24
7
3
9.95, H 4.10, N 6.90; found: C 40.02, H 3.88, N 6.86. FT-IR
−1
(cm ): 3429(w), 3067(w), 2931(w), 2038(w), 1628(m), 1604
(m), 1561(w), 1475(m), 1457(m), 1407(m), 1335(m), 1305
(s),1241(m), 1221(s), 1670(m), 1149(w), 1091(m), 1074(m),
[
(NO
3
)
2 6 6 2 6 3
⊂Co(III)Co(II) (OH) (L ) ](NO )·3MeCN (4)
To a solution of Co(NO ) ·6H O (0.25 g, 0.86 mmol) in MeOH
3
2
2
1
013(m), 961(m), 883(w), 859(m), 830(w), 787(m), 743(s).
3
(
(
30 cm ) was added 2-iminophenyl-6-methoxyphenol (L H)
0.195 g, 0.86 mmol) initially affording a dark red-coloured,
2
transparent solution, which gradually adopted a darker colour as
stirring proceeded. Solid NaOH (0.034 g, 0.86 mmol) was then
added resulting in the solution adopting a golden red–brown
appearance. The solution was stirred for a further 5 h after which
it was filtered, to yield a dark red–brown mother liquor. The
product 4 was allowed to crystallise from the mother liquor via
slow solvent evaporation. Complex 4 was received as dark red–
brown crystalline blocks in 15% yield. Elemental analysis calcu-
lated for C H N O Co (loss of all MeCN) (%): C 49.02, H
[
(MeOH)
2
⊂Co(II)
7 6 1 6 3 2
(OH) (L ) ](NO ) (2)
To a solution of Co(NO ) ·6H O (0.25 g, 0.86 mmol) in MeOH
(
0
and the solution stirred at ambient temperature for 3 hours. The
solution was then filtered to afford a dark red–brown mother
liquor which was allowed to slowly evaporate to encourage crys-
tallisation. Aliquots of the mother liquor were also diffused with
3
2
2
3
30 cm ) was added 2-iminomethyl-6-methoxyphenol (0.142 g,
.86 mmol). Solid NaOH (0.034 g, 0.86 mmol) was then added
84
78
9
27
7
−1
diethyl ether (Et O) towards better quality crystals suitable for
3.82, N 6.13; found: C 48.85, H 3.68, N 6.16. FT-IR (cm ):
3361(w), 1610(s), 1589(s), 1559(m), 1464(s), 1390(s), 1345(m),
1297(s), 1233(s), 1188(s), 1102(m), 1078(m), 1038(w), 1022
(w), 972(m), 907(w), 848(w), 776(s), 733(s), 694(s). UV/vis
2
X-ray analysis. Dark brown/black hexagons of 2 were obtained
both from slow evaporation and diethyl ether diffusion of the
mother liquor with a combined yield of 30%. Elemental analysis
calculated for C H N O Co (%): C 40.04, H 3.96, N 6.67;
3
3
−1
−1
data [λmax, nm (ε , 10 dm mol cm )] in MeOH: 364
56
66
8
26
7
m
−1
Found: C 40.22, H 3.68, N 6.95. FT-IR (cm ): 3622(w),
427(w), 2911(w), 2812(w), 1626(m), 1603(w), 1561(w), 1457
(27.6), 276 (97.4), 226 (122.9, 204 (149.6); [CH CN]: 360
3
3
(32.2), 273 (97.4), 224 (164.5), 200 (226.4).
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 5610–5616 | 5615

View Article Online
[Co(II)(L
2
)
2
] (5)
J. Serpell, N. L. Kilah and P. D. Beer, Chem.–Eur. J., 2010, 16 (44),
13082–13094.
4
5
M. Yoshizawa, J. K. Klosterman and M. Fujita, Angew. Chem., Int. Ed.,
2009, 48, 3418–3438 and references therein.
(a) W. P. Jencks, Catalysis in Chemistry and Enzymology, McGraw-Hill,
New York, 1969; (b) R. Breslow, Acc. Chem. Res., 1995, 28, 146–153;
(c) A. Kirby, Angew. Chem., Int. Ed. Engl., 1996, 35, 706–724.
O. Danylyuk and K. Suwinska, Chem. Commun. (Feature Article), 2009,
To a solution of CoSO ·7H O (0.25 g, 0.89 mmol) in MeOH
4
2
3
(
25 cm ) was added L H (0.202 g, 0.89 mmol). The solution
2
was stirred to afford complete dissolution of the solid material.
Solid NaOH (0.036 g, 0.89 mmol) was then added which
resulted in a dark red–brown solution. This solution was then
stirred for a further 3 h under ambient conditions after which it
was filtered to yield a dark red–brown solution. The solution was
then placed in a fridge (at ∼4 °C). Dark red–brown crystalline
blocks of 5 were isolated from the mother liquor in moderate
yield (20%) after 4 days. Elemental analysis calculated (%) for
C H N O Co : C 65.73, H 4.73, N 5.47; found: C 65.71, H
6
7
5799–5813.
M. V. Rekharsky, T. Mori, C. Yang, Y. Ho Ko, N. Selvapalam, H. Kim,
D. Sobransingh, A. E. Kaifer, S. Liu, L. Isaacs, W. Chen, S. Moghaddam,
M. K. Gilson, K. Kim and Y. Inoue, Proc. Natl. Acad. Sci. U. S. A., 2007,
104 (52), 20737–20742.
8
(a) S. J. Dalgarno, P. K. Thallapally, L. J. Barbour and J. L. Atwood,
Chem. Soc. Rev., 2007, 36, 236–245; (b) P. K. Thallapally, B. P. McGrail,
S. J. Dalgarno, H. T. Schaef, J. Tian and J. L. Atwood, Nat. Mater., 2008,
2
8
24
2
4
1
−1
7, 146–150.
4
(
1
8
.64, N 5.68. FT-IR (cm ): 1602(s), 1578(s), 1539(m), 1487
m), 1463(m), 1431(s), 1386(m), 1356(w), 1323(m), 1228(s),
186(s), 1106(m), 1076(m), 1028(w), 999(w), 980(m), 905(w),
66(w), 852(m), 786(m), 773(m), 762(m), 743(s), 691(s).
9
I. Imar, J. Hernando, D. Ruiz-Molina and D. Maspoch, Angew. Chem.,
Int. Ed., 2009, 48, 2325–2329.
1
0 For examples see: (a) T. Heinz, D. M. Rudkevich and J. Rebek Jr,
Nature, 1998, 394, 764–766; (b) F. Perret and A. W. Coleman, Chem.
Commun. (Feature Article), 2011, 47, 7303–7319.
1
1 (a) J. L. Atwood, E. K. Brechin, S. J. Dalgarno, R. Inglis, L. F. Jones,
A. Mossine, M. J. Paterson, N. P. Power and S. J. Teat, Chem. Commun.,
010, 46, 3482–3486; (b) S. M. Taylor, G. Karotsis, R. D. McIntosh,
[
Co(III)
2
Na(I)
1
(L
3 6 4
) ](BF ) (6)
2
3
S. Kennedy, S. J. Teat, C. M. Beavers, W. Wernsdorfer, S. Piligkos,
S. J. Dalgarno and E. K. Brechin, Chem.–Eur. J., 2011, 17, 7521–7530;
(c) S.-Y. Yu, H. Huang, H.-B. Liu, Z.-N. Chen, R. Zhang and M. Fujita,
Angew. Chem., Int. Ed., 2003, 42, 686–690.
2 (a) H. Amouri, C. Desmarets, A. Bettoschi, M. N. Rager, K. Boubekeur,
P. Rabu and M. Drillion, Chem.–Eur. J., 2007, 13, 5401–5407;
To an EtOH solution (25 cm ) of Co(BF ) ·6H O (0.25 g,
0
4
2
2
.73 mmol) was added L H (0.179 g, 0.73 mmol). The solution
3
was stirred for 5 min before NaOH (0.029 g, 0.73 mmol) was
added to afford an opaque brown solution. The solution was
further stirred for 5 h and then filtered affording a dark red–
brown mother liquor. Following the lack of crystallisation of 6,
the solution was allowed to evaporate to dryness to afford a
brown–black residue. This solid was then redissolved in MeCN
10 cm ) from which X-ray quality crystals of 6 were obtained
in 25% yield) upon Et O diffusion after 2 weeks. Elemental
1
(b) E. Pardo, K. Bernot, F. Lloret, M. Julve, R. Ruiz-Garcia, J. Pasan,
C. Ruiz-Perez, D. Cangussu, V. Costa, R. Lescouezec and Y. Journaux,
Eur. J. Inorg. Chem., 2007, 4569–4573; (c) R. G. Harrison, J. L. Burrows
and L. D. Hansen, Chem.–Eur. J., 2005, 11, 5881–5888.
3 References (a) and (b) here formed part of a Chem. Soc. Rev. themed
issue on Hybrid Materials which should also be considered here.
(a) M. Clemente-Leon, E. Coronado, C. Marti-Gastaldo and
F. M. Romero, Chem. Soc. Rev., 2011, 40, 473–497; (b) J. Yuan, Y. Xu
and A. H. E. Muller, Chem. Soc. Rev., 2011, 40, 640–655.
4 (a) S. T. Meally, C. McDonald, G. Karotsis, G. S. Papaefstathiou,
E. K. Brechin, P. W. Dunne, P. McArdle, N. P. Power and L. F. Jones,
Dalton Trans., 2010, 39, 4809–4816; (b) S. T. Meally, G. Karotsis,
E. K. Brechin, G. S. Papaefstathiou, P. W. Dunne, P. McArdle and
L. F. Jones, CrystEngComm, 2010, 12, 59–63.
1
1
3
(
(
2
analysis calculated (%) for C H N O B F Br Co Na : C
5
4
54
6
12
1
4
6
2
1
3
(
8.47, H 3.23, N 4.98; found: C 38.26, H 3.44, N 5.03. FT-IR
−1
cm ): 1628(s), 1590(w), 1546(w), 1463(m), 1452(m), 1435(s),
354(w), 1342(w), 1307(s), 1238(s), 1217(m), 1189(w), 1098
m), 1080(m), 1052(m), 1027(m), 1018(m), 978(m), 960(w),
35(w), 874(m), 851(w), 834(m), 825(m), 787(m), 758(m), 689
s), 666(w).
1
(
9
(
1
5 (a) D. Altermatt and I. D. Brown, Acta Crystallogr., 1985, B41, 244–247;
(b) I. D. Brown, Chem. Rev., 2009, 109, 6858–6919.
6 For examples see: (a) S.-H. Zhang, Y. Song, H. Liang and M.-H. Zeng,
CrystEngComm, 2009, 11, 865–872; (b) L.-Q. Wei, B.-W. Li, S. Hu and
1
M.-H. Zeng, CrystEngComm, 2011, 13, 510–516.. Note: The {Co(II)
4
-
Acknowledgements
Co(III) } analogue to this work has previously been observed and
3
should be noted here: A. Ferguson, A. Parkin, J. Sanchez-Benitez,
K. Kamenev, W. Wernsdorfer and M. Murrie, Chem. Commun., 2007,
3473–3475.
7 (a) C. Albayrak, B. Koşar, S. Demir, M. Odabaşoğlu and
O. Büyükgüngör, J. Mol. Struct., 2010, 963, 211–218; (b) G.-Y. Yeap,
S.-T. Ha, N. Ishizawa, K. Suda, P.-L. Boey and W. A. K. Mahmood, J.
Mol. Struct., 2003, 658, 87–100.
The authors would like to thank the NUI Galway Millennium
Fund (LFJ), the Irish Research Council (IRCSET) Embark Fel-
lowship (SM) and the NUI Galway College of Science Fellow-
ship (CMcD) for funding. EKB acknowledges the support of the
EPSRC and the Leverhulme Trust.
1
18 Sh. Yue, J. Li Zh., H. Yu, Q. Wang, X. P. Gu and Sh. L. Zang,
Russ. J. Coord. Chem., 2010, 36 (7), 547–551.
19 P. Viswanathamurthi, N. Dharmaraj and K. Natarajan, Synth. React.
Inorg. Met.-Org. Chem., 2000, 30, 1273–1286.
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5616 | Dalton Trans., 2012, 41, 5610–5616
This journal is © The Royal Society of Chemistry 2012