Deliberate boxes and accidental wheels

Article abstract of DOI:10.1039/c4dt03089c

This report describes systems which combine the structural and reactive motifs of a dinucleating terpyridine-aminomethylpyridine ligand, L, with the coordination preferences and flexibilities of particular divalent metal ions to form a series of closely r

Full text of DOI:10.1039/c4dt03089c

Dalton
Transactions
PAPER
Deliberate boxes and accidental wheels†
Cite this: Dalton Trans., 2015, 44,
Gurpreet Kaur, Matthew I. J. Polson and Richard M. Hartshorn*
4200
This report describes systems which combine the structural and reactive motifs of a dinucleating terpyri-
dine-aminomethylpyridine ligand, L, with the coordination preferences and flexibilities of particular di-
valent metal ions to form a series of closely related box structures in a deliberate fashion. The ligand also
produces unprecedented decanickel wheel complexes. Halogen to aromatic hydrogen interactions may
be important in stabilising the decanickel wheel structures.
Received 7th October 2014,
Accepted 16th January 2015
DOI: 10.1039/c4dt03089c
www.rsc.org/dalton
Introduction
Results and discussion
Ligand synthesis
Nature uses metal centres as both structural and reactive units
1
–5
in larger structural arrays. For example, the shapes and bio- The terpyridine–aminomethylpyridine ligand L (Scheme 1),
logical functions of zinc finger proteins and many enzymes was prepared by reaction of 2-aminomethylpyridine with a
result from a combination of the structural features of the brominated terpyridine derivative, following an essentially
ligands and the coordination preferences of metal ions, while standard terpyridine synthesis and a subsequent radical
the function of the photosynthetic reaction centre is intimately bromination reaction. The yields of the bromination reactions
tied to the relative positions of the redox centres and cofactors were variable, but the crude product mixture could be readily
6
–8
within the protein scaffold.
Our goal is to explore how the resubmitted to the reaction conditions if the bromination
structural features of ligands and coordination chemistry can yield was low, and any residual 4′-(2′′′-toluyl)-2,2′:6′,2″-ter-
be used to control the assembly of polynuclear complexes con- pyridine could be removed in the final chromatographic
taining both redox active metal ions and labile metal ions purification.
bearing exchangeable ligands.
2
,2′:6′,2″-Terpyridine derivatives and their complexes have
been extensively studied molecules since the early 20th
century, due to their luminescence, spin crossover and redox
properties, which have potential uses in charge storage, solar
9
–14
cells and photocatalysis.
Terpyridines are excellent ligands,
providing tridentate metal binding domains with high affinity
for many metal ions and limited possibilities for formation of
1
5–20
different stereoisomers.
Thus a terpyridine ligand will
bind in a meridional fashion to an octahedral metal ion and,
depending on the relative amounts of metal and ligand that
are present, a second ligand may bind as well.
In this paper we describe the synthesis of a terpyridine
ligand that has an appended bidentate metal-binding domain
and subsequent coordination chemistry in which molecular
boxes have been prepared in a deliberate fashion.
Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch
8
140, New Zealand. E-mail: richard.hartshorn@canterbury.ac.nz;
Fax: +64 3 364 2110; Tel: +64 3 364 2874
Electronic supplementary information (ESI) available: Crystallographic detail.
†
CCDC 1011648, 1011574, 1011644, 1011645 and 1039222. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/c4dt03089c
Scheme 1 Ligand L, contains tridentate and bidentate metal ion
binding domains which have been used to prepare molecular boxes.
4200 | Dalton Trans., 2015, 44, 4200–4206
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Dalton Transactions
Paper
Boxes
Ligand L contains a tridentate terpyridine binding site which
was designed to act either as a structural component through
formation of a typical bis-terpyridine complex, or as a site at
which to bind a metal ion bearing exchangeable ligands. The
2
-aminomethylpyridine binding site allows binding of another
metal ion, again carrying exchangeable ligands that could lead
to catalytic activity, as shown in Scheme 1.
Adding a bidentate binding domain to a terpyridine
scaffold results in formation of a new class of ligand in which
the denticity and geometric preferences of the metal binding
domains may be used to control the outcomes of synthetic
2
1–24
reactions.
Thus a metal ion such as Fe(II), with a strong
preference for an octahedral geometry will link two terpyridine
units and leave the bidentate site in each of the two ligands
free for coordination to other more coordinationally flexible
metal ions such as Zn(II). Such metal ions can be coordinated
to the aminomethylpyridine ‘tail’ of the ligand, giving either
an exposed catalytic site or a means to link two ML2 units
together through an additional metal centre with an incom-
plete ligand sphere.
2+
6+
Fig. 2 UV-visible spectra of the [Fe(L)
2
]
(blue) [Fe
2
Zn
2
(L)
4
Cl
2
]
(red)
6
+
and [Zn
4
(L)
4
(OAc)
2
]
(green) box complexes.
The preparation and isolation of the FeL2 complex is
straight forward, as might be expected. Addition of Zn(II) salts
−
to solutions of the FeL2 complex, in the presence of [PF ]
6
6
+
ions, resulted in the formation of a [Fe Zn (L) Cl ] box
2
2
4
2
complex (Fig. 1).
Given that the coordination chemistry of Zn(II) is notable
for its variability in coordination number and geometry, we
attempted to prepare similar box complexes in which both
kinds of coordination site are occupied by Zn(II) ions. The
resulting structure is also shown in Fig. 1, and this reveals that
acetate ligands can also be bound to the Zn(II) ions in the
bidentate sites.
6+
Fig. 3 The [Fe
2
Zn
2
(L)
4
(tpt)]
box complex. The solvent and anions
have been omitted for clarity.
6
+
The isolation of the [Zn L (OAc) ] box also enabled us to
4
4
2
examine and eliminate the possibility of metal scrambling in
6
+
the two [Fe Zn (L) X ] mixed metal systems. This possibility
2
2
4 2
1
(
ε
561 = 670 L mol− cm−1) than the Fe(II)-containing boxes, and
was discounted on the basis of the UV-vis measurements
and molar absorptivity data (Fig. 2). The absorbance at
the Fe Zn L complex has a molar absorptivity (ε
= 28 700
2
2
4
561
L mol− cm ) slightly larger than twice the extinction coeffi-
1
−1
5
61 nm can be assigned principally to the Fe(II)-bis(terpyri-
cient of the FeL
2
complex (ε561 = 13 200 L mol− cm ), there
1
−1
2
5,26
dine) chromophore based on literature precedent.
Since
6
+
must be little or no scrambling of metal ions either within or
between boxes in a sample.
the [Zn
4
L
4
(OAc)
2
]
box complex is much more weakly coloured
The bis-bidentate bridging ligand terephthalate was also
deliberately encapsulated in the middle of the Fe Zn L box to
2
2 4
produce the complex where the terephthalate ion (tpt) replaces
−
−
the Cl /OAc ligands in the coordination sphere of the Zn(II)
ions (Fig. 3). Collectively, these structures invite speculation
that it may be possible to bind and react molecules within
these boxes.
In the solid state, each box shaped assembly is surrounded
by PF6− anions. In particular, two of the six PF6 ions are
located immediately above and below the box complexes and
have two F⋯H–N hydrogen bonds to the amine groups of the
box (Fig. 4). Presumably, the location of these anions helps
direct the monodentate ligand on the Zn(II) centre towards the
centre of the box structure.
−
6
+
6+
Fig. 1 The [Fe
2
Zn
2
(L)
4
Cl
2
]
(left) and [Zn
4
L
4
(OAc)
2
]
(right) box com-
plexes. The solvent and anions have been omitted for clarity.
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Paper
Dalton Transactions
Fig. 4 Hydrogen bonding between PF −
boxes and the coordinated amine groups of the boxes.
ions above and below the
6
Fig. 6 Thermogravimetric analyses of the wheel complexes
16+
16+
[Ni10L10Br (H O) ]
4
2
6
(red) and [Ni10L10Cl (H O) ]
4
2
6
(black).
6
+
6+
[
Fe
2
Zn
2
(L)
4
Cl
2
]
(left) and [Zn
4
(L)
4
(OAc)
2
]
(right) box complexes. The
solvent and spectator anions have been omitted for clarity.
ring varies from 29.296 to 26.515 Å and the wheel is 15.349 Å
deep. The Ni(II) ions in the wheel are well separated from each
other, both in space and through bonds.
Wheels
The Br− ion that is present inside the wheel cavity appears
In contrast to the results from Zn(II) complex formation,
attempts to prepare Ni(II) complexes of L using NiBr led to to be held tightly due to a number of hydrogen bonds and
2
−
isolation of the remarkable decanickel wheel complex other atomic interactions. Fifteen uncoordinated Br ions are
1
6+
−
[Ni10
L
10Br
4
(H
2
O)
6
]
, shown in Fig. 5, with a Br ion in its also present in the crystal lattice. The structure of the complex
centre. Each six-coordinate Ni(II) ion is bound to the terpyri- contains approximately 160 water molecules, randomly present
dine moiety of one ligand, the aminomethylpyridine ‘tail’ of in and around the wheels. These water molecules link the
the terpyridine ligand bound to a neighbouring Ni(II) ion, and wheels in a 3D network by the hydrogen bond interactions
either a Br− ion (on two of the ten Ni(II) ions), a water ligand between various atoms. Thermogravimetric analysis (Fig. 6) is
(on six Ni(II) ions) or a disordered mixture of the two (on two consistent with the presence of ∼160 water molecules, as the
Ni(II) ions). Thus each ligand reaches around to the next Ni(II) wheels lose approximately 30% of their mass as they are being
ion from the outside of the wheel, with the terpyridine units heated to 100 °C. Samples dried in vacuum rapidly lose their
nearer to the centre of the wheel.
crystallinity when heated through this temperature range, as do
The wheel is approximately circular with an inner cavity dia- samples being heated during attempts to measure melting points.
1
6+
meter measured between the symmetry equivalent hydrogen
With NiCl , a similar wheel structure ([Ni L Cl (H O) ]
)
2
10 10
4
2
6
−
atoms of 7.696 to 6.016 Å and distances between symmetry forms (Fig. 7). Cl ions occupy all of the Ni(II) coordination
equivalent Ni of 18.933 to 20.218 Å. The outer diameter of the sites in which Br− ions were found in the first wheel. The
−
remaining six Ni(II) ions have water ligands, as in the Br struc-
ture described above.
In the middle of the wheel, the smaller size of the Cl− ion
means it is disordered over two positions, each with half occu-
pancy. This reduction in size also causes the wheel to become
−
more elliptical, elongating to 7.748 Å along the axis of the Cl
ion sites, and compressed to 5.686 Å in the perpendicular direc-
tion, with Ni to Ni distances of 18.880 to 20.274 Å and rim to
rim distances of 29.886 to 24.551 Å. If even trace amounts of
−
Br ion are present in solution, crystals are isolated in which a
−
−
Br ion is at the centre of the wheel, while four Cl ions are
attached to Ni(II) ions and another 15 are present in the lattice.
−
−
The preference for binding Br over Cl in the cavity, seems
to be due to the size of the Br− ion being the correct size to
allow H-bonding with all of the ten hydrogen atoms which
point into the cavity from the wheel. The off-centre distri-
bution of the Cl− ions over two positions within the wheel
maximizes the number and strength of H-bonding interactions
that the Cl− ion can make with the wheel, given its smaller,
and less optimal, size. This in turn leads to a more elliptical
1
6+
Fig. 5 [Ni10
L
10Br
4
(H
2
O)
6
]
viewed down the a axis. The solvent
waters, anions and ligand disorder have been omitted for clarity.
4202 | Dalton Trans., 2015, 44, 4200–4206
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Paper
resultant creamy yellow suspension was treated with o-tolu-
aldehyde (1.2 g, 10 mmol) and the mixture was stirred overnight
at room temperature under nitrogen. A solution of dry
ammonium acetate (15.8 g) in 2 : 1 ethanol–acetic acid
(
190 mL) was then added and the clear brown mixture
obtained was heated at reflux for 5 hours. The resulting
orange-yellow reaction mixture was cooled to room tempera-
ture and treated with ice (500 g) and water (2 L) to give a yellow
precipitate. The precipitate was collected by filtration. Recrys-
tallisation from ethanol gave pure 4′-(2′′′-toluyl)-2,2′:6′,2″-terpyri-
dine as pale yellow crystals. Yield: 2.5 g (68%); m.p.146–152 °C;
1
3
H NMR (CDCl ): δ = 8.72 (d, 2H, H6,6″), 8.71 (d, 2H, H3,3″),
8
.49 (s, 2H, H3′,5′), 7.90 (t, 2H, H4,4″), 7.30–7.36 (m, 6H, H5,5″,
1
3
toluyl), 2.38 (s, 3H, CH3); C NMR (CDCl ): 156.5, 155.6, 152.2,
3
1
1
49.4, 139.9, 137.1, 135.4, 130.7, 129.7, 128.5, 126.2, 124.1,
+
21.9, 121.6, 20.7 (CH
′-{2′′′-(Bromomethyl)phenyl}-2,2′:6′,2″-terpyridine. 4′-(2′′′-
Toluyl)-2,2′:6′,2″-terpyridine (2.0 g, 6.1 mmol) and purified
3
); ESI-MS m/z: [M + H] 324.13.
4
16+
Fig. 7 [Ni10
L
10Cl
4
(H
2
O)
6
]
viewed down the a axis. The solvent
waters, anions and ligand disorder have been omitted for clarity. The N-bromosuccinimide (1.2 g, 6.5 mmol) were added to a dry
−
two Cl ions shown in the centre of the structure have only half
three-necked round bottom flask while flushing with N2.
occupancy.
Freshly distilled CCl
4
(150 ml) was also transferred to the
. The solution was
three-necked flask while flushing under N
2
irradiated with a tungsten lamp for about 5 hours after adding
a catalytic amount of dibenzoyl peroxide (0.002 g). The mixture
was heated to 25 °C for 12 hours under N . The reaction
2
mixture was cooled to room temperature and filtered. The fil-
trate was concentrated under vacuum to give the crude bromi-
nated product, 4′-{2′′′-(bromomethyl)phenyl}-2,2′:6′,2″-terpyridine
shape as the Cl− wheel distorts make these H-bonds stronger.
This CH⋯X tight binding of an appropriately sized central
halide by multiple aromatic C–H groups has been exploited in
other systems such as the triazolophane macrocycles which
2
7
have been used as anion sensors.
as a yellow oil, which was used directly because of its tendency to
1
decompose. Yield = 2.2 g (90%); H NMR (CDCl
3
) δ = 8.72 (d,2H),
Conclusions
8
7
1
1
.71 (d, 2H), 8.58(s, 2H), 7.91 (t,2H), 7.58 (d,1H), 7.58 (d,1H),
13
.35–7.44 (m,5H), 4.45 (s, 2H, CH Br); C NMR (CDCl ) 156.2,
A new terpyridine-aminomethylpyridine ligand has been syn-
thesised and yields complexes in which the coordination prefer-
ences of the metal ions control the structure of the complex and
provide exchangeable sites with the potential for future catalytic
function. Reactions with Fe(II) and Zn(II) yield four metal centre
boxes with Fe(II) being solely structural and Zn(II) ions offering
coordination sites which can be occupied by different ligands
without disturbing the structure. The exchangeable ligands
point in towards a hydrophobic, aromatic rich environment.
When the Ni(II) ions bind to both sites of the ligand, an
unprecedented decanuclear structure is formed. The structure
has ten exchangeable sites around the wheel pointing out. A
bound Br− ion occupies the central position in the wheel in
2
3
55.8, 150.5, 149.5, 140.1, 137.3, 135.3, 131.2, 130.4, 129.2, 129.0,
+
24.2, 121.8, 121.7, 31.8 (CH
′-[2′′′-{(2-pyridylmethyl)aminomethyl}phenyl]-2,2′:6′,2″-
terpyridine (L). (2-Aminomethyl)pyridine (0.53 g, 4.9 mmol)
was dissolved in dry CH CN (100 mL), with stirring, followed
by the addition of K CO (0.68 g, 4.9 mmol). The mixture was
2
Br); ESI-MS: m/z [M + H] 402.0612.
4
3
2
3
stirred for 10 min at 35 °C. 4′-{2′′′-(bromomethyl)phenyl}-
,2′:6′,2″-terpyridine (2.0 g, 4.9 mmol) was added to the stir-
2
ring solution. The resulting mixture was heated to 50 °C for 4
days under a reflux condenser, filtered and the filtrate was
taken to dryness under vacuum. The residual oil was a crude
product containing L, unreacted amine and 4′-(2′′′-toluyl)-
−
2,2′:6′,2″-terpyridine. Yield (crude): 2.0 g (95%).
preference to an exchangeable Cl ion.
The F⋯H–N interactions enhance the stability of the boxes
and the Br/Cl⋯C–H interactions play a significant role in the
structures of the wheels.
Experimental
Synthesis
4
′-(2′′′-Toluyl)-2,2′:6′,2″-terpyridine. 2-Acetylpyridine (2.4 g,
0 mmol) was added to a solution of potassium t-butoxide
3.36 g, 30 mmol) in freshly distilled dry THF (160 mL) and the
2
(
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Paper
Dalton Transactions
20Zn 36·5H
L was purified by alumina column chromatography. Initial C 44.71, H 3.40, N 9.40. Calcd for C112
92
H N
2
Fe
2
Cl
2
P
6
F
2
O
−1
elution with DCM removed any unreacted 4′-(2′′′-toluyl)- (%): C 44.97, H 3.44, N 9.36. IR (KBr, cm ) 3340 s, 2368 w,
,2′:6′,2″-terpyridine. L was eluted with a 0.5% MeOH–DCM 1844 w, 1611 m, 1535 w, 1468 w, 1368 w, 1040 w, 794 s, 626 w,
mixture. The eluate was taken to dryness and pure L was col- 558 m, 497 w, 458 w.
lected as a pale yellow fine powder. Yield 1.2 g (60%); m. [Zn L (OAc) ](PF ) ·2CH CN. A methanolic solution of
p. 125–127 °C; Elemental analysis: Found (%): C 78.34, H 5.61, Zn(OAc)
N 16.61, Calcd C28 (%): C 78.44, H 5.42, N 16.34; nolic solution of L (0.010 g, 0.023 mmol), resulting in a pale
2
4
4
2
6 6
3
2
2
·2H O (0.01 g, 0.046 mmol) was mixed with a metha-
23 5
H N
1
H NMR (500 MHz, CDCl ): δ = 8.68 (d, J = 8, 2H, H3,3″), 8.65 yellow solution. The solution was then treated with a con-
3
(d, J = 4, 2H, H6,6″), 8.54 (s, 2H, H3′,5′), 8.34 (d, J = 5, 1H, Hc), centrated methanolic solution of ammonium hexafluorido-
7
.86 (td, 2H, H4,4″), 7.65 (d, J = 8, 1H, H3″), 7.42–7.38 (m, 4H, phosphate. Later addition of an excess of cold water resulted in
H5′′′,6′′′,4″,e), 7.34 (td, 2H, H5,5″), 7.23 (d, J = 8, 1H, Hf), 6.98 formation of a white precipitate. The precipitate was collected
1
3
(
t, J = 5, 1H, Hd), 3.85 (d, 4H, Ha,b); C NMR (500 MHz) following centrifugation, and washed with methanol and
1
1
58.3, 156.1 (2C), 155.3 (2C), 150.9, 149.2 (2C), 149.0, 139.9, ether. Vapour diffusion of di-isopropyl ether into an aceto-
36.8 (2C), 136.3, 135.9, 129.9–129.8 (2C), 128.7, 127.5, 123.8 nitrile solution of the white precipitate produced colourless
(
2C), 122.3, 121.9, 121.6 (2C), 121.3 (2C), 53.9, 50.5; IR (KBr, blocks of X-ray quality crystals within two days. Yield 0.012 g,
−
1
cm ) 3140 m, 3055 m, 2925 m, 2854 m, 1585 s, 1567 ssh, 63%; m.p. 245–248 °C; Elemental analysis: Found (%):
1
9
541 msh, 1466 s, 1393 w, 1335 m, 1264 m, 1131 w, 992 m, C 46.17, H 3.34, N 9.37, Calcd C116H N Zn O P F ·2H O
98 20 4 4 6 36 2
07 w, 851 m, 762 s, 652 w, 627 m, 508 w, 467 w; ESI-MS: m/z (%): C 46.40, H 3.42, N 9.34; 1H NMR (DMSO) δ = 8.86 (d,2H),
+
2+
+
[M + H ] 430.202, [M + 2H ] 215.605, [2M + H ] 859.396.
8.83 (d,2H), 8.69 (d, 3H), 8.23 (d,3H), 7.85 (s, 1H), 7.67 (t, 2H),
[
FeL ](PF ) ·4H O. FeCl ·2H O (0.05 g, 0.025 mmol) in 7.54–7.46 (m, 5H), 7.17 (d, 1H), 6.98 (t, 1H), 3.80 (s, 2H), 3.76
2
6 2
2
2
2
methanol was added to a solution of L (0.02 g, 0.05 mmol) in (s, 2H); IR (KBr, cm− ) 3675 w, 3340 s, 2542 w, 1866 w, 1603 s,
methanol to give a purple solution, immediately. The solution 1575 w, 1549 w, 1478 s, 1419 w, 1371 w, 1325 w, 1248 m, 794 s,
was heated for 1 h while stirring and then cooled to room 764 w, 739 w, 658 w, 559 s, 469 w; UV-vis (CH CN): λ
1
3
max
temperature, followed by addition of few drops of a concen- (ε) = 275 (111 200), 287 (96 800), 322 (63 400), 561 (670) nm
trated methanolic solution of ammonium hexafluorido- (L mol− cm ).
1
−1
phosphate. An excess of cold water was also added to enhance [Fe Zn L C H O ](PF ) . (NH ) Fe(SO ) ·6H O (9 mg,
2
2
4
8
4
4
6 6
4 2
4 2
2
the precipitation of complex. The purple complex was collected 0.035 mmol) in methanol (1 mL) and L (30 mg, 0.070 mmol)
from the aqueous solution following centrifugation, washed in chloroform (1 mL) were mixed, producing a purple solution.
with ether–methanol (2 : 1) solution, and dried under a N2 Excess sodium terephthalate (70 mg) in water (5 mL) was
stream. Yield 0.030 g, 75%; m.p. 255–260 °C; Elemental added. After stirring for 30 min, Zn(NO
analysis Found (%): 52.41, 4.13, 10.61, Calcd 0.070 mmol) in methanol (1 mL) was added. The mixture was
C H N FeP F ·4H O (%): 52.63, 4.26, 10.97. heated at reflux for 8 h and then cooled to room temperature.
CN) δ: 160.0, 157.8, 153.2, 149.8, 148.9, 138.8, A few drops of saturated ammonium hexafluoridophosphate in
37.5, 132.1, 131.1, 130.9, 130.4, 129.7, 127.4, 124.4, 124.0, methanol and cold water (20 mL) were used to precipitate the
3 2 2
) ·6H O (20 mg,
C
H
N
C
H
N
5
6
46 10
2
12
2
1
3
C NMR (CD
3
1
1
1
−
1
23.3, 122.8, 51.7, 49.7; IR (KBr, cm ) 3635 s, 3064 w, 1608 m, complex. The precipitate was collected by centrifugation,
573 w, 1613 m, 1545 w, 1469 m, 1423 w, 1365 m, 1288 s, 1163 washed with an ether–methanol (2 : 1) solution, and dried
w, 1056 w, 1028 w, 1000 s, 830 vs, 790 w, 754 m, 654 w, 558 s, under a stream of N
2
. X-ray quality single crystals (square
2
+
4
97 w, 458 w; ESI-MS (CH CN): m/z [Fe + 2L] 457.1623, purple plates) were formed by slow diffusion of ethyl acetate
3
2+
2+
[
Fe + 2L + PF6 + H] 530.1483, [Fe + 2L] 305.1106; UV-vis into an acetonitrile solution over a period of 3 weeks.
CH CN): λmax (ε) = 275 (45 800), 287 (47 900), 322 (34 200), 561 Yield 0.056 g, 60%. M.P. >280 °C. UV-vis (CH CN): λmax (ε) =
13 200) nm (L mol cm ). 275 (88 300), 287 (94 830), 322 (71 800), 561 (24 720) nm
Fe Zn Cl ](PF ·4H O. FeCl
(
(
3
3
−
1
−1
2 2
·2H
O (0.05 g, 0.025 mmol) (L mol− cm ). IR (neat, cm ) 3340 s, 2368 w, 1844 w,
1
−1
−1
[
2
2
L
4
2
6
)
6
2
in methanol (1 mL) was added to L (0.02 g, 0.05 mmol) in 1698 w, 1557 s, 1551 m, 1504 w, 1381 w, 1020 w, 823 s, 789 s,
chloroform (1 mL) to give a purple solution. The resulting 653 w, 556 m, 447 w. Elemental analysis: found (%): C 47.42,
purple solution was treated with an excess of ZnCl
methanol. The mixture was heated for 1 h with stirring and (%): C 47.28, H 3.37, N 9.19.
then cooled to room temperature, followed by addition of few [Ni10L10Br (H O) ]Br ·68H O. NiBr ·3H O (0.008 g,
2 2 92 2 2 8 4 4 6 2
·2H O in H 3.72, N 8.89. calcd for C112H N20Fe Zn C H O P F36·3H O
4
2
6
16
2
2
2
drops of saturated ammonium hexafluoridophosphate in 0.029 mmol) in water (10 mL) was added to L (0.006 g,
methanol. An excess of cold water was added to enhance the 0.014 mmol) in methanol–chloroform (4 : 1, 5 mL), and the
precipitation of complex. The complex was collected by cen- resulting solution was heated at reflux for 30 min. The volume
trifugation, washed with an ether–methanol (2 : 1) solution, of the yellow green solution of the complex was reduced to
and dried under a stream of N
fragile purple plates) were formed by slow evaporation of an ation resulted in the formation of pale green X-ray quality crys-
acetonitrile solution. Yield 0.056 g, 60%. M.P. >280 °C. UV-vis tals (blocks) over a period of 3 weeks. Yield 0.009 g, 90%.
2
. X-ray quality single crystals 1 mL by rotavap. The solution was filtered, and slow evapor-
(
CN): λmax (ε) = 275 (88 900), 287 (95 800), 322 (73 200), 561 IR (KBr, cm− ) 3645 w, 3190 s, 1605 s, 1550 w, 1470 m, 1417 w,
1
(
(
CH
28 700), nm (L mol cm ). Elemental analysis found (%): 1302 w, 1247 m, 1162 w, 1055 w, 1016 s, 890 w, 772 s, 645 w,
3
−
1
−1
4204 | Dalton Trans., 2015, 44, 4200–4206
This journal is © The Royal Society of Chemistry 2015

Dalton Transactions
Paper
5
98 w, 548 w, 516 w, 499 w, 481 w, 465 w. Elemental ana- phosphorus atom, occupying at least two closely spaced sites.
lysis: found (%): C 43.91, H 4.86, N 9.18%. Calcd for The nitrate anion is involved in hydrogen bonding to the nitro-
C
280
H
230
N
50Ni10Br20·68H
2
O (7705.19) (%): C 43.65, H 4.80, gen atoms coordinated to the zinc atoms, and is disordered
over two sites. This was modelled as disordered over two equal
N 9.09.
occupancy sites, with isotropic thermal parameters fixed at
the value of the central phosphorus atom. The OLEX2 solvent
X-ray crystallography
X-Ray data were collected on an Oxford-Agilent Supernova mask was used to correct for the remaining unidentified
6
+
instrument with a focused microsource Cu Kα [λ = 1.5405 Å] solvent molecules as above. [Fe Zn L Cl ] was solved and
2
2
4
2
radiation and an ATLAS CCD area detector. CCDC 1039222, refined with the complex of interest, three independent PF
6
1
011648, 1011574, 1011644 and 1011645 contain the sup- anions, two half occupancy water molecules and two partial
plementary crystallographic data for this paper.
occupancy ethyl acetate molecules (0.2 and 0.3 occupancy) in
and the asymmetric unit. No mask was required for this structure.
6+
16+
The
[Fe
2
Zn
2
L
4
(tpt)] ,
4 2 6
[Ni10L10Br (H O) ]
1
6+
[
4 2 6
Ni10L10Cl (H O) ]
structures contained significant amounts
of disordered solvent molecules. This was handled systemati-
cally for the two wheel structures. First, a phase solution was
found and the structure of interest was determined and
refined anisotropically for all non-hydrogen atoms. Hydrogen
atoms were calculated as riding atoms with thermal para-
meters dependant on the riding atom for all carbon atoms.
For all non-carbon atoms with hydrogens except for solvent
molecules, the hydrogens were located in the electron differ-
ence map, and allowed to refine at a fixed distance from the
heteroatom, with a thermal parameter dependant on the
riding atom. Solvent water atoms and counterions were
inserted into the model as isolated, isotropic atoms where
there was sufficient electron density, sufficiently distant from
other solvent waters/counterions, and their occupancies were
allowed to refine. This used about 60 water molecules of some
Notes and references
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1
6+
occupancy in the asymmetric unit of [Ni L Br (H O) ] and
1
0
10
4
2
6
16+
4 2 6
[Ni10L10Cl (H O) ]
. Estimates of these numbers were included
in the formula used for the final absorption correction, but not
in the final atom count. Counterions were distinguished from
solvent waters by the electron density, and were refined aniso-
tropically. No attempt was made to model co-occupancy of a
partial counterion with a solvent water. Once a stable refine-
ment had been achieved, water molecules with an occupancy of
less than one were deleted from the model and the OLEX2
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molecules and the additional, highly disordered regions occu- 10 E. S. Bazhina, M. E. Nikiforova, G. G. Aleksandrov,
pied by solvent water which had not been modelled. The
remaining water molecules were refined as isotropic oxygen
atoms, without hydrogens, due to the lack of electron density to
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electrons corrected for in the mask (180 waters) approximately 12 D. N. Chirdon, W. J. Transue, H. N. Kagalwala, A. Kaur,
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6
+
[
Zn L (OAc) ] was solved and refined with the complex of
4 4 2
−
interest, three well-ordered PF
6
anions and one acetonitrile 13 G. Singh Bindra, M. Schulz, A. Paul, R. Groarke, S. Soman,
solvent molecule in the asymmetric unit as above. A solvent
mask was used to remove a small, but poorly order void in the
J. L. Inglis, W. R. Browne, M. G. Pfeffer, S. Rau,
B. J. MacLean, M. T. Pryce and J. G. Vos, Dalton Trans.,
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3
model (187 Å ).
6
+
2 2 4
[Fe Zn L (tpt)] was solved and refined with the complex 14 U. S. Schubert, H. Hofmeier and G. R. Newkome, in Modern
−
of interest, four well-ordered PF6 anions and one acetonitrile
Terpyridine Chemistry, Wiley-VCH Verlag GmbH & Co.
KGaA, 2006, pp. 1–6, 37–38.
solvent molecule in the asymmetric unit as above. The final
−
PF
6
anion and a single nitrate anion were poorly ordered, 15 M. A. Bork, H. B. Vibbert, D. J. Stewart, P. E. Fanwick and
−
with the PF6 anion being rotationally disordered about the
D. R. McMillin, Inorg. Chem., 2013, 52, 12553–12560.
This journal is © The Royal Society of Chemistry 2015
Dalton Trans., 2015, 44, 4200–4206 | 4205

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4206 | Dalton Trans., 2015, 44, 4200–4206
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