Assembly of high nuclearity clusters from a family of tripodal tris-carboxylate ligands

Article abstract of DOI:10.1016/j.poly.2016.04.029

A family of four tris-carboxylic acid ligands 1,3,5-tris(4′-carboxybiphenyl-2-yl)benzene (H₃L¹), 1,3,5-tris-2-carboxyphenylbenzene (H₃L²), 1,3,5-tris(4″-carboxy-para-terphenyl-2-yl)benzene (H₃L^3<

Full text of DOI:10.1016/j.poly.2016.04.029

Polyhedron xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Assembly of high nuclearity clusters from a family of tripodal
tris-carboxylate ligands
a
a
a
b
b
Stephen P. Argent , Irina Tarassova , Alex Greenaway , Harriot Nowell , Sarah A. Barnett ,
b
b
a,c
a
a,
⇑
Mark R. Warren , Chiu C. Tang , Christopher G. Morris , William Lewis , Neil R. Champness ,
a,c,
⇑
a,
⇑
Martin Schröder
a
, Alexander J. Blake
School of Chemistry, University of Nottingham, University Park, NG7 2RD, UK
Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
b
c
a r t i c l e i n f o
a b s t r a c t
0
1
Article history:
3
A family of four tris-carboxylic acid ligands 1,3,5-tris(4 -carboxybiphenyl-2-yl)benzene (H L ),
Received 31 March 2016
Accepted 18 April 2016
Available online xxxx
2
00
3
1
,3,5-tris-2-carboxyphenylbenzene (H
3
L ), 1,3,5-tris(4 -carboxy-para-terphenyl-2-yl)benzene (H
3
L )
0
4
and 1,3,5-tris(3 -carboxybiphenyl-2-yl)benzene (H
3
L ) have been synthesised and reacted with first
row transition metal cations to give nine complexes which have been structurally characterised by
X-ray crystallography. The ligands share a common design motif having three arms connected to a
benzene core via three ortho-disubstituted phenyl linkers. The ligands vary in length and direction of the
carboxylic acid functionalised arms and are all able to adopt tripodal conformations in which the three
Keywords:
High nuclearity cluster
Metal-directed assembly
Carboxylate bridging
Basic carboxylate
Crystal structure
1
2
arms are directed facially. The structures of [Zn
8
(
l
6
4
-O)(L )
4
(HCO ] (1a-Zn), [Co14(L )
(HCO (2-Ni), [Zn -O)
8 4 4 4 3 2
(DMF) ] (5-Ni), [Co (l -O) (L ) (DMF) (H O)]
2
)
2
(H
2
O)0.33(DMF)
2
6
2
(
(
l
3
-OH)
8
(HCO
(DMF)(H O)
6-Co) and Fe
2
)
2
(DMF)
(NO
4
(H
2
O)
6
]
(2-Co), [Ni14(L )
(
l
3
-OH)
8
2
)
2
(DMF)
4
(H O)
2
6
]
8 4
(l
3
2
4
(L )
4
2
4
3
)
2
] (3-Zn), [Ni
5
(
l
-OH)
4
(L )
2
(H
2
O)
6
4
4
(
(
3
(
l
3
-O)(L )
2
(H
2
O)(DMF)
2
)] (7-Fe) contain polynuclear clusters surrounded by ligands
1
–4 3ꢀ
1
L
)
in tripodal conformations. The structure of [Zn
2
(HL )
are partially deprotonated whilst {[Zn
(4-Zn) is a 2D coordination network containing {Zn (RCO (solv)
2
2 4
(DMF) ] (1b-Zn) shows it to be a binuclear
2
2ꢀ
2
complex in which the two ligands (HL )
N)]ꢁ6(DMF)}
3
(L )
2 2
(DMF)(H O)
} paddlewheel
(C H
5 5
n
2
)
2 4
units. The conformations of the ligand arms in the complexes have been analysed, confirming that the
shared ortho-disubstituted phenyl ring motif is a powerful and versatile tool for designing ligands able
to form high-nuclearity coordination clusters when reacted with transition metal cations.
Ó 2016 Elsevier Ltd. All rights reserved.
1
. Introduction
Multi-metallic coordination clusters are of interest from the
in the remaining sites being occupied by small hydroxy- and
oxo-ligands [8–10]. An alternative strategy is to use polytopic
ligands with closely spaced binding domains able to span multiple
metal cations. A ligand in which the binding domains are rigidly
pre-organised will help to overcome the entropic penalty associ-
ated with forming the high degree of order typical of polynuclear
clusters [11–13].
perspectives of both fundamental [1] and application-targeted [2]
chemistry. Examples have been shown to have interesting mag-
netic properties [3,4], to act as mimics for active sites of enzymes
[
5,6] or to have utility as structural building units for the design
and synthesis of metal–organic frameworks (MOFs) [7]. Strategies
used to promote the formation of high-nuclearity complexes
include incorporating bulky peripheral groups into ligands in order
to restrict the coordination number at metal centres, resulting
We have previously used polytopic carboxylate ligands with
aromatic spacers as linkers for the synthesis of a wide variety of
porous MOFs with applications in gas storage and separation
[14–17]. The formation of MOFs requires ligands with divergent
binding domains which lead to poly-dimensional networks. We
argued that the same chemical design elements could be used to
synthesise ligands with convergent binding domains which would
fulfil the requirements of a ‘pre-organisation’ strategy. We have
⇑
Corresponding authors at: School of Chemistry, University of Manchester,
Oxford Road, Manchester M13 9PL, UK.
E-mail addresses: neil.champness@nottingham.ac.uk (N.R. Champness),
m.schroder@manchester.ac.uk (M. Schröder), a.j.blake@nottingham.ac.uk
0
reported the tripodal ligand 1,3,5-tris(4 -carboxybiphenyl-2-yl)-
1
benzene
H
3
L
which binds Cd(II) cations to form a large
(
A.J. Blake).
http://dx.doi.org/10.1016/j.poly.2016.04.029
277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
0
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

2
S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
L1–4 with representations of their tripodal endo conformations highlighting key torsion angles / , /2 and /3 and intraligand carboxylate separation
1
Scheme 1. View of H
distance d.
3
polynuclear nano-sphere complex [Cd66
(
l
3
-OH)28
(
l
3
-O)16
(
l
5
-NO
3
)
12
-
4-(Ethoxycarbonyl)phenylboronic acid 12 and 3-(ethoxycarbonyl)-
phenylboronic acid 18 were purchased from Frontier Scientific.
Bromo-1-(2,3-dihydro-1H-naphtho[1,8-de]-1,3,2-diazaborinyl)-
benzene 11 was synthesised starting from 4-bromophenylboronic
acid 10 according to a literature method [21]. 1,3,5-Tris(2-bro-
1
(
L )20
(
l
2
-DMF)12ꢂ(DMF)
9
] with an unprecedented metallo-ligand
core–shell structure [18]. This threefold symmetric ligand features
three ortho-diphenylbenzene motifs which can orient the three
carboxylic acid binding domains either all to the same face of
the ligand (endo conformation) or one above and two below the
plane of the ligand (exo conformation). Both of these conforma-
tions were observed in the reported family of complexes of
0
mophenyl)benzene 15 was synthesised from 2 -bromoacetophe-
1
13
none 16 according to a literature method [22]. H NMR and
C
NMR spectra were measured on Bruker DPX400, AV400 and
AV(III)400 spectrometers. High-resolution electrospray mass
spectra were measured on a Bruker MicroTOF spectrometer.
MALDI-TOF mass spectra were measured using a Bruker Spec-
troflex III mass spectrometer with DCTB (trans-2-[3-(4-tert-butyl-
1
3ꢀ
(
L ) with Cd(II) cations. When the ligand adopts an endo confor-
mation the ligand can exhibit a propeller-like twist in its three
arms giving it chiral C symmetry. The pitch of this propeller twist
3
varies and dictates the distance d between the pendant carboxylate
groups (Scheme 1). The degree of twist can be defined by the
torsion angles / along the bonds between the central phenyl ring
phenyl)-2-methyl-2-propenylidene]malononitrile) as a matrix.
1
Where yields for complexation reactions have been given they
are calculated based on the mass of the solvated material as
indicated by interpretation of elemental analysis.
and three ortho-disubstituted phenyl rings [19]. A second torsion
2
angle
/
between the ortho-disubstituted phenyl rings and
carboxylic acid functionalised phenyl rings does not alter the
distance d between the three carboxylate groups, but it does influ-
ence their orientations.
2
.1.1. 1,3,5-Tris-2-methylphenylbenzene (9)
0
2
-Methylacetophenone 8 (20.0 g, 150.0 mmol) and trifluo-
We report herein a family of tris-carboxylic acid ligands H
3
L1–4
romethanesulfonic acid (2.50 g, 15.0 mmol) were added cautiously
to a round-bottom flask before being stirred and heated at 130 °C
under N for 24 h. During the course of the reaction a viscous black
2
mixture formed which solidified upon cooling to room tempera-
ture. The crude reaction mixture was quenched by addition of
water (5 cm ) before being extracted with dichloromethane which
4
was washed with water and brine, dried over MgSO and concen-
trated under reduced pressure. The resulting crude product was
recrystallised from chloroform and methanol giving 9 as a colour-
and their reactions with a variety of first-row transition metal
cations to explore the propensity of these tripodal ligands to form
1–4
polynuclear clusters. The ligands H
3
L
share the central design
principle in having three arms with pendant carboxylic acid moieties
attached to a central benzene ring via ortho-substituted phenyl
3
1
linkages. The new ligands differ from H
3
L in three ways: decreas-
ing or increasing the length of the spacers in the three arms of the
2
3
ligand (H
3 3
L and H L , respectively) or changing the location of the
phenylcarboxylic acid group from the para to the meta positions of
1
less crystalline solid (yield 16.0 g, 89%). H NMR (CD
d 7.24–7.35 (m, 15H), 2.40 (s, 9H). C NMR (CDCl
1
2
Cl
, 400 MHz) d
41.1, 140.9, 134.9, 130.0, 129.5, 128.1, 126.9, 125.4, 21.1. ESI-
2
, 400 MHz)
4
the linkages (H
3
L ). The resulting array of one two-dimensional
13
3
network and eight discrete complexes exhibits a variety of ligand
conformations, ancillary co-ligands and metal-coordination motifs.
+
TOF-HRMS: m/z Calc. for C27
H24: 348.1878. Found 348.1882 [M] .
Elemental Anal. Calc. for C27
H
24: C, 93.06; H, 6.94. Found: C,
ꢀ
1
9
2.89; H, 6.87%. ATR-FTIR (cm ): 3019 (w), 1423(m), 1389(w),
2
. Experimental
1
216(m), 1110(s), 754(s), 669(s).
2
.1. Synthesis
2
2
.1.2. 1,3,5-Tris-2-carboxyphenylbenzene (H
3
2
L ꢁ3(H O))
H
3
L1 was synthesised according to our previously described
method [18]. We report an improved synthesis of the previously
reported [20] ligand 1,3,5-tris-2-carboxyphenylbenzene
4
KMnO (8.00 g, 50.6 mmol) was added portion-wise over 5 days
to a stirred solution of 1,3,5-tris-2-methylphenylbenzene 9 (2.10 g,
6.0 mmol) and NaOH (2.10 g, 52.5 mmol) in a mixture of water
2
H
3
L .
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
3
3
3
(
60 cm ) and tert-butanol (60 cm ), with the temperature main-
solution concentrated under reduced pressure. The resulting resi-
due was dissolved in toluene (20 cm ), washed with water
3
tained at 55 °C. The mixture was then heated at 80 °C for 1 h before
the hot mixture was filtered and the filtrate concentrated under
reduced pressure. The solution was acidified with concentrated
HCl (10 cm ) resulting in precipitation of H
which was collected, washed with water and dried in vacuo (yield
.30 g, 60%). H NMR (CDCl
H), 7.53 (td, J = 7.6, 1.2 Hz, 3H), 7.40 (td, J = 7.2, 1.2 Hz, 3H), 7.34
dd, J = 7.2, 1.0 Hz, 3H), 7.18 (s, 3H). ESI-TOF-HRMS: m/z Calc. for
3
3
(4 ꢃ 20 cm ), brine (2 ꢃ 20 cm ), dried over MgSO
4
and concen-
trated under reduced pressure resulting in a grey solid, which
was recrystallised from chloroform and methanol to give Et
as white crystals (yield 150 mg, 44%). H NMR (CDCl ,
400 MHz) d 8.12 (d, J = 8.3 Hz, 6H), 7.48–7.32 (m, 15H), 7.31–7.17
(m, 6H), 7.08–6.92 (m, 9 H), 6.82 (s, 3H), 4.47 (d, J = 7.0 Hz, 6H),
3
2
3
3
L
as a white solid
3
L -
1
ꢁCHCl
3
3
1
1
3
(
C
3
, 400 MHz) d 7.94 (dd, J = 7.6, 1.0 Hz,
+
1.48 (t, J = 7.2 Hz, 9H). ESI-TOF-MS: m/z 1001.2 [M+Na] . Elemental
+
27
H
18
O
18Na: 461.001. Found 461.1004 [M+Na] . Elemental Anal.
Calc. for C27 O) : C, 65.85; H, 4.91. Found: C, 65.50; H,
18ꢁ(H
.57%. ATR-FTIR (cm ): 3444 (br), 2790 (m, br), 2490 (m, br),
Anal. Calc. for C69
4.66%.
H
54
O
6 3
ꢁCHCl : C, 76.53; H, 5.05. Found: C, 76.65; H,
H
18
O
2
3
ꢀ
1
4
1
0
0
3
680 (s), 1422(s), 1260 (s), 1070 (m), 754 (m), 669(m).
2.1.6. 1,3,5-Tris(4 carboxy-para-terphenyl-2-yl)benzene (H
3
L )
3
To a stirred suspension of Et
3
L ꢁCHCl
3
(100 mg, 0.0912 mmol)
in 2-propanol (20 cm ) was added saturated aqueous KOH
(1 cm ). The mixture was heated under reflux for 8 h resulting in
0
3
2
[
.1.3. Ethyl-4 -(1H-naphtho[1,8-de][1,3,2]diazaborinin-2(3H)-yl)-
1,1 -biphenyl]-4-carboxylate (13)
0
3
Bromo-1-(2,3-dihydro-1H-naphtho[1,8-de]-1,3,2-diazaborinyl)-
benzene 11 (2.40 g, 7.43 mmol), 4-(ethoxycarbonyl)phenylboronic
dissolution of all the material. The volume of solvent was reduced
3
to 10 cm under reduced pressure before the solution was acidified
3
acid 12 (2.40 g, 12.4 mmol), powdered tripotassium phosphate
with concentrated hydrochloric acid (5 cm ) resulting in formation
3
(
3.40 g, 20.7 mmol) and 1,4-dioxane (150 cm ) were added to a
of a white precipitate, which was collected and washed sequen-
3
round-bottom flask fitted with a condenser and heated at 80 °C
for 15 min under N . Pd(PPh (0.47 g, 0.41 mmol) was added to
the mixture which was purged with N for a further 15 min before
tially with water, methanol and diethyl ether to give H
3
L
as a
1
2
3
)
4
6
white solid (yield 51 mg, 62%). H NMR (DMSO-d , 400 MHz) d
2
8.02 (d, J = 8.4 Hz, 6H), 7.48–7.40 (m, 15H), 7.40–7.32 (m, 6H),
7.28 (t, J = 7.4 Hz, 3H), 7.01 (d, J = 7.5 Hz, 3H), 6.92 (d, J = 7.8 Hz,
being stirred at 80 °C for 2 days. The mixture was allowed to cool,
+
filtered and the filtrate concentrated under reduced pressure. The
6H), 6.72 (s, 3H). MALDI-TOF-MS: m/z 917.4 [M + Na] . Elemental
3
resulting residue was dissolved in chloroform (100 cm ), washed
Anal. calc. for C63
4.36%. ATR-FTIR (cm ): 3260 (br), 1670 (s), 1600 (m), 1320 (w),
1030 (s, br), 755 (s).
H
42
ꢀ1
O
6
: C, 84.54; H, 4.73. Found: C, 83.12; H,
3
3
with water (3 ꢃ 50 cm ) and brine (50 cm ) and concentrated
under reduced pressure to give brown solid, which was
recrystallised from chloroform and methanol to give 13 as large
yellow needles (yield 2.07 g, 71%). 1H NMR (CDCl
, 400 MHz) d
.25–8.04 (m, 2H), 7.85–7.67 (m, 6 H), 7.19 (dd, J = 7.3, 8.2 Hz,
a
0
4
3
2.1.7. 1,3,5-Tris(3 (ethoxycarbonyl)biphenyl-2-yl)benzene (Et
3
L )
0
8
2
2
1,3,5-Tris-2 -bromophenylbenzene 15 (500 mg, 0.921 mmol),
3-(ethoxycarbonyl)phenylboronic acid 18 (894 mg, 4.61 mmol),
H), 7.11 (d, J = 7.8 Hz, 2H), 6.48 (dd, J = 0.8, 7.3 Hz, 2H), 6.11 (s,
H), 4.45 (q, J = 7.2 Hz, 2H), 1.46 (t, J = 7.2 Hz, 3H). ESI-TOF-MS:
2 3 3 4
K CO (1.15 g, 8.30 mmol) and Pd(PPh ) (29 mg, 0.0249 mmol)
+
3
3
m/z 392.23 [M] . Elemental Anal. Calc. for C25
H21BN
2
O
2
: C, 76.55;
were added to a mixture of toluene (90 cm ), ethanol (10 cm )
3
H, 5.40; N, 7.14. Found: C, 76.51; H, 5.33; N, 7.26%. ATR-FTIR
and water (10 cm ) which was then heated at 70 °C and purged
ꢀ1
(
(
cm ): 3360 (s), 2900 (m), 1590 (s), 1580 (s), 1360 (m), 1260
s), 1080 (m), 756 (m, br), 728 (m).
2
with N for 15 min. The reaction mixture was stirred at 70 °C for
2 days before being allowed to cool. The reaction mixture was fil-
3
tered, and water (50 cm ) was added to the filtrate which was
0
0
2
.1.4. (4 -(Ethoxycarbonyl)-[1,1 -biphenyl]-4-yl)boronic acid (14)
extracted into toluene. The toluene extract was then washed with
0
3
3
To a stirred solution of ethyl-4 -(1H-naphtho[1,8-de][1,3,2]diaz-
aborinin-2(3H)-yl)-[1,1 -biphenyl]-4-carboxylate
.50 mmol) in THF (80 cm ) was added H
water (4 ꢃ 30 cm ) and brine (2 ꢃ 30 cm ), dried over MgSO
4
and
0
13
(1.00 g,
concentrated under reduced pressure to give an orange oil which
was purified by column chromatography (15% ethyl acetate in hex-
ane on silica) to give Et
3
3
2
2
SO
4
(2 M, 12.8 cm )
4
1
and the solution stirred overnight at room temperature resulting
in formation of a white precipitate. The solid was removed by fil-
3
L as a white solid (yield 387 mg, 56%). H
NMR (CDCl , 400 MHz) d 8.04 (t, J = 1.5 Hz, 3H), 7.89 (dt, J = 7.7,
3
3
tration and the filtrate was diluted with ethyl acetate (30 cm )
1.3 Hz, 3H), 7.27–7.43 (m, 12H), 7.00 (dt, J = 7.8, 1.3 Hz, 3H), 6.8
(d, J = 7.4 Hz, 3H), 7.76 (s, 3H), 4.39 (q, J = 7.1, 6H), 1.39 (t, J = 7.1,
3
and washed sequentially with water (4 ꢃ 50 cm ) and brine
3
(
2 ꢃ 25 cm ), dried over MgSO
4
, concentrated under reduced pres-
42 6
9H). ESI-TOF-HRMS: m/z Calc. for C51H O Na: 773.2879. Found
+
sure and triturated with pentane to give 14 as a pale yellow pow-
der (yield 0.541 g, 92%). 1H NMR (CDCl
, 400 MHz) d 8.82–8.66
m, 2H), 8.59 (d, J = 1.5 Hz, 2H), 8.43 (d, J = 8.2 Hz, 2H), 7.96–7.81
m, 2H), 4.60–4.40 (m, 2H), 1.53–1.41 (m, 3H). ESI-TOF-HRMS:
m/z Calc. for C15
Elemental Anal. Calc. for C15
6.65; H, 5.43%. ATR-FTIR (cm ): 3330 (s, br), 2980 (m), 1710
s), 1600 (s), 1270 (s, br), 1100 (s), 1000 (m), 735 (m), 722 (m).
42 6
773.2771 [M+Na] . Elemental Anal. Calc. for C51H O : C, 81.58;
3
H, 5.64. Found: C, 81.50; H, 5.22%.
(
(
0
4
2.1.8. 1,3,5-Tris(3 -carboxybiphenyl-2-yl)benzene (H
3
L )
+
3
L4 as
3
H16BO
4
: 271.1142. Found 271.1032 [M + H] .
The same synthetic method as for H
3
L was used to give H
a white solid. H NMR (DMSO-d , 400 MHz) d 7.88 (d, J = 7.53 Hz,
1
H
15BO
4
: C, 66.70; H, 5.60. Found: C,
6
ꢀ
1
6
(
3H), 7.81 (s, 3H), 7.47 (t, J = 7.72 Hz, 3H), 7.38–7.43 (m, 3H), 7.30
(t, J = 6.53 Hz, 3H), 7.06 (d, J = 7.40 Hz, 3H), 6.77 (d, J = 7.40 Hz,
+
3
H), 6.66 (s, 3H). ES-TOF-MS: m/z 689.7 [M + Na] . Elemental Anal.
00
2
.1.5. 1,3,5-Tris(4 (ethoxycarbonyl)-para-terphenyl-2-yl)benzene
30 6
calc. for C45H O : C, 81.07; H, 4.54. Found: C, 82.01; H, 4.89%.
3
chloroform solvate (Et
3
L ꢁCHCl
3
)
0
-O)(L1)
(20 mg, 0.030 mmol) and Zn(NO
1
,3,5-Tris-2 -bromophenylbenzene 15 (168 mg, 0.309 mmol),
2.1.9. [Zn
8
(l
4
4
(HCO
2
2
) (H
2
O)0.33(DMF)
2
]ꢁ7.75(DMF) (1a-Zn)
0
0
1
(
(
4 -(ethoxycarbonyl)-[1,1 -biphenyl]-4-yl)boronic
500 mg, 1.85 mmol), CsF (565 mg, 3.72 mmol) and tris(dibenzyli-
(DBA) ] were added to 1,4-diox-
ane (25 cm ) and heated at 80 °C under N for 15 min. Tri-tert-
acid
14
H
3
L
3
)
2
ꢁ6H (71 mg,
2
O
3
0.240 mmol) were dissolved in DMF (3 cm ) and heated in a sealed
vial at 85 °C for 3 days resulting in formation of large colourless
crystals with the shape of Clovis points [23]. Single crystals for
X-ray analysis were taken directly from the mother liquor. The
bulk sample was washed with fresh DMF, collected by filtration
and dried in vacuo to give 1a-Znꢁ2(DMF) as a white solid (yield
deneacetone)dipalladium(0) [Pd
2
3
3
2
butylphosphine (25.0 mg, 0.124 mmol) was added and the reaction
mixture stirred at 80 °C for 18 h before being allowed to cool. The
solid residue was removed by centrifugation and the resultant
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

4
S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
7
mg, 26%). Upon standing in the cooled DMF reaction mixture for
2.1.12. [Ni14(L2)
The same synthetic method was used as for 2-Co. H
0.030 mmol) and Ni(NO O (70 mg, 0.240 mmol). After 5 days
heating small green rhombic crystal plates were observed amongst
pale green amorphous material. Single crystals were manually
selected for X-ray analysis. Satisfactory analytical results for the
bulk material could not be obtained.
6
(l
3
-OH)
8
(HCO
) (DMF) (H
2 2 4 2
O)
6
]ꢁ24(DMF) (2-Ni)
1
1
more than 5 days the crystals were observed to re-dissolve.
NMR (CDCl , 400 MHz) d 8.22 (d-br, J = 7.8 Hz, 12H), 8.05 (s-br,
8H, DMF), 7.75 (d-br, J = 7.40 Hz, 12H), 7.24–7.43 (m, 48H), 7.18
H
3
L (20 mg,
3
3
)
2
ꢁ6H
2
4
(
(
d, J = 7.2 Hz, 12H), 6.67 (s, 12H), 5.69 (d-br, J = 8.3 Hz, 12H), 2.99
s, 36H, DMF), 2.92(s, 36H, DMF). MALDI-TOF-MS: m/z Calc. for
⁄
+
Zn
Elemental Anal. Calc. for Zn
3.95; H, 4.32; N, 2.90. Found: C, 63.80; H, 3.73; N, 2.27%. Most
abundant peak in simulated isotopic distribution at m/z 3258.2.
8
O(C45
H
27
O
6
)
4
(HCO
2
)(H
2
O): 3243.2. Found 3261.8 [M-HCO
2
-(solv)] .
8
O(C45 (HCO) (C NO)
H
27
O
6
)
4
2
3
H
7
8
: C,
⁄
2
.1.13. [Zn
The same synthetic method was used as for 1a-Zn, using H
10 mg, 0.0112 mmol), Zn(NO (16 mg, 0.0559 mmol)
8
(
l
4
-O)(L3)
4
(DMF)(H
2
O)
4
](NO
3
)
2
ꢁ16(DMF) (3-Zn)
6
L3
3
(
3
)
2 2
ꢁ6H O
3
and DMF (1.5 cm ). After 2 days colourless hexagonal plate
2.1.10. [Zn
2
(HL1)
(10 mg, 0.0150 mmol) and Zn(NO
2
(DMF)
4
]ꢁ2(DMF) (1b-Zn)
crystals (yield 18 mg) were obtained. Elemental Anal. Calc. for
1
H
3
L
3
)
2
ꢁ6H
2
O
(27 mg,
⁄
Zn
3
8
O(C63H
42
O
6
)
4
(NO
3
)
2
(H O)
2 6
(C
3
H
7
NO)10: C, 66.65; H, 4.96; N,
3
0
.090 mmol) were dissolved in DMF (1 cm ) into which was dif-
⁄
.31. Found: C, 63.20; H, 5.61; N, 3.14%. Closest plausible match
fused diisopropyl ether resulting in formation of large colourless
crystal plates amongst amorphous white materials. Single crystals
were taken directly from the mother liquor for X-ray analysis.
to the obtained analysis; the analysis is likely to be affected by
ambiguity in the identity of the coordinated counter ion.
2
.1.14. {[Zn
The same synthetic method was used as for 1a-Zn using H
O) (20 mg, 0.0407 mmol) and Zn(NO
ꢁ6H
3
(L2)
2
(DMF)(H
2
O)(C
5
H
5
N)]ꢁ6(DMF)}
n
(4-Zn)
2
2
.1.11. [Co14(L2)
6
((l
3
-OH)
8
(HCO
2
2 4
) (DMF) (H
2
O)
6
]ꢁ28(DMF) (2-Co)
ꢁ6H (69 mg,
3
L ꢁ3
1
(
H
2
3
)
2
2
O
(59 mg,
H
3
L
(20 mg, 0.030 mmol) and Co(NO
3
)
2
2
O
3
3
3
0
.203 mmol) in DMF (3 cm ) and pyridine (0.1 cm ) resulting in
0
.240 mmol) were dissolved in DMF (3 cm ) and heated in a
formation of colourless blocky crystals (yield 36 mg, 58%). Elemen-
tal Anal. Calc. for Zn (H O) (C N)(C NO)3.5: C,
5.06; H, 5.12; N, 4.16. Found: C, 55.43; H, 5.35; N, 3.92%.
sealed vial at 85 °C for 5 days resulting in formation of pink
rhombic crystal plates. Crystals for single crystal X-ray
analysis were taken directly from the mother liquor. The bulk
sample was washed with fresh DMF, collected by filtration,
washed with diethyl ether and dried in vacuo to give 2-Coꢁ8
3
(C27
H
18
O
6
)
2
2
6
H
5 5
3 7
H
5
2.1.15. [Ni
5
(
l
-OH)
4
(L2)
2
(H
2
O)
6
(DMF)
4
]ꢁ6(DMF) (5-Ni)
2
(
DMF) as a pink solid (yield 19 mg, 11%). Elemental Anal. Calc.
H
3
L ꢁ3(H
2
O) (10 mg, 0.0203 mmol) and Ni(NO
3
)
2
ꢁ6H
2
O (30 mg,
3
for Co14(OH)
6
8
(C45
H
27
O
6
)
6
(HCO
2
)
2
(H
2
O)
6
(C
3
H
7
NO)
4
ꢁ8(C
3
H
7
NO): C,
0.102 mmol) were dissolved in DMF (1.4 cm ) and heated in a
1.47; H, 4.49; N, 2.79. Found: C, 62.15; H, 4.03; N, 2.58%.
sealed vial at 80 °C for 5 days. Diisopropyl ether vapour was
t
Scheme 2. Synthesis of H
THF; (vi) (a) Pd (DBA)
ꢁCHCl
3
L2–4. Conditions: (i) CF
3
SO
3
H; (ii) KMnO
4
, KOH; H
2
O, BuOH (iii) 1,8-diaminonaphthalene, toluene; (iv) Pd(PPh
3 4
) , K
3 4 2 4
PO , 1,4-dioxane; (v) H SO ,
2
3
3
, CsF, 1,4-dioxane (b) KOH(aq), 2-propanol; (vii) CF
3
SO
3
H; (viii) (a) Pd(PPh
)
3 4
2
, K CO
3
, toluene, EtOH, H
2
O, (b) KOH(aq), 2-propanol.
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
5
diffused into the resultant green solution resulting in the formation
of a small number of green blocky crystals, which were taken
directly from the mother liquor for single crystal X-ray analysis.
absorption correction based on Gaussian integration over a multi-
faceted crystal model. The diffraction data for 4-Zn, 5-Ni and 7-Fe
were collected at Diamond Light Source, Beamline I19, on a Crys-
talLogic Kappa 4-circle diffractometer equipped with a Rigaku
Saturn 724 + CCD detector using synchrotron radiation with a
wavelength of 0.6889 Å [25]. The raw data were reduced and cor-
rected for Lorentz and polarisation effects using CrystalClear [26]
and corrected for the effects of adsorption using Scale imple-
mented in CrystalClear. The structures were solved by direct meth-
ods and refined by full-matrix least-squares using the SHELXTL
software package [27]. Details of the crystal structure refinements
can be found in the Supplementary information.
2
.1.16. [Co
8
(
l
4
-O)
4
(L4)
4
(DMF)
3
(H
2
O)]ꢁ3(H
2
O)ꢁ6(DMF) (6-Co)
ꢁ6H
.150 mmol) were dissolved in DMF (2 cm ) and heated in a sealed
4
3
H L
(20 mg, 0.030 mmol) and Co(NO
3
)
2
2
O
(44 mg,
3
0
vial at 80 °C for 2 days resulting in formation of small black block
crystals. Crystals were either taken directly from the mother liquor
for single crystal X-ray analysis or washed with fresh DMF,
collected by filtration and dried in vacuo to give 6-Coꢁ4(DMF) as
a
black solid (yield 27 mg, 24%). Elemental Anal. Calc. for
8 4 18 6 4 3 7 4 2
Co O (C27H O ) (C H NO) (H O)15: C, 50.72; H, 4.33; N, 2.40.
Found: C, 51.02; H, 3.60; N, 3.88%.
2.2.2. Powder X-ray diffraction
2
.1.17. [Fe
3
(
l
3-O)(L4)
2
(H
2
O)(DMF)
2
)]ꢁ10(DMF) (7-Fe)
ꢁnH O (45 mg) were
dissolved in DMF (2 cm ) and heated in a sealed vial at 80 °C for
days resulting in formation of very small brown lath-shaped
A dried sample of 6-Co was lightly ground before being loaded
4
3
H L
(20 mg, 0.030 mmol) and Fe(NO
3
)
3
2
into a 0.5 mm borosilicate capillary. High-resolution powder
diffraction data were collected at Diamond Light Source, Beamline
I11 using multi-analysing-crystal detectors (MACs) using radiation
with a wavelength of 0.826161 Å with the sample maintained at a
temperature of 273 K. A Pawley refinement [28] of the data was
performed using TOPAS-Academic [29] to extract the unit cell
parameters.
3
2
crystals amongst amorphous brown material. Crystals were taken
directly from the mother liquor for single crystal X-ray analysis.
2.2.1. Single crystal X-ray diffraction studies
Crystals were mounted under a film of Fomblin perfluo-
ropolyether on a Mitegen Micromount and flash-frozen under a
cold stream of N . Diffraction data for 1a-Zn, 1b-Zn, 2-Co, 2-Ni,
-Zn, and 6-Co were collected on a Rigaku Oxford Diffraction
3. Results and discussion
2
3
3.1. Ligand synthesis
SuperNova diffractometer equipped with an Atlas detector and
microfocus Cu source. The raw data were reduced and corrected
for Lorentz and polarisation effects using CrysAlisPro [24]; correc-
tions for the effects of adsorption were applied using a numerical
Ligands H
3 3 3
L1, H L3 and H L4 were all synthesised using
Pd-catalysed Suzuki cross-coupling reactions from the common
starting material 1,3,5-tris(2-bromophenyl)benzene 15 which
1
3ꢀ
Fig. 1. View of (a) overall structure and of (b) Zn
formate yellow; zinc black. View of (c) overall structure and of (d) packing of [Zn
8 4 4 2 4 3 2
highlighted in red. View of (e) overall structure and of (f) Zn O(RCO core in [Zn (l -O)(L ) (DMF)(H O) ](NO ) (3-Zn): colours as for (a). (Color online.)
8
O(RCO
2
)
4
core in [Zn
8 4
(l
-O)(L1)
4
(HCO
2
)
2
(H
2 2
O)0.33(DMF) ] (1a-Zn): ligands (L ) orange, green, red, blue; DMF orange;
1
1 3ꢀ
2
(HL )
2
(DMF) ] (1b-Zn): ligands (L ) purple, blue; DMF yellow; zinc black; hydrogen bonds
4
3
8
2
)
4
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

6
S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
itself was synthesised in good yield from the cyclotrimerization of
0
2
-bromoacetophenone 16 (Scheme 2). The triple cross-coupling
reactions involving this sterically-demanding substrate give at best
moderate yields with partially-reacted dehalogenated products
accounting for the remaining material. The extended biphenyl-
3
boronic acid intermediate 14 required to synthesise H
3
L
was
obtained by masking the boronic acid functionality of 4-bro-
mophenylboronic acid 10 using 1,8-diaminonaphthalene [21]
before cross-coupling the resulting fragment 11 with 4-(ethoxy-
carbonyl)phenylboronic acid 12 to give 13. The 1,8-diaminonaph-
thalene protecting group was subsequently removed by acid
hydrolysis to reveal the boronic acid functional group. After purifi-
1
3
4
cation, the triethyl-esters of ligands H
3 3 3
L , H L and H L were
hydrolysed with KOH, followed by an acidic work up to give the
2
3
tris-carboxylic acids. Ligand H L was synthesised by the threefold
oxidation of the methylphenyl functional groups of 1,3,5-tris-2-
0
methylphenylbenzene 9, which was synthesised from 2 -methy-
lacetophenone 8 using cyclotrimerization conditions analogous to
those used to obtain 15.
3
H
.2. Synthesis, structure and characterisation of complexes of ligands
3
L
1
–4
1
3
.2.1. [Zn
Reaction of H
8
(
l
4
-O)(L )
4
(HCO
2
) (H
2
2
O)0.33(DMF)
2
]ꢁ7.75(DMF) (1a-Zn)
1
3
L with Zn(NO
3
)
2
ꢁ6H O in DMF for 5 days at 85 °C
2
resulted in formation of a crop of large colourless crystals which
1
X-ray analysis showed to be [Zn
.75(DMF) (1a-Zn). The polynuclear cluster crystallises in the cen-
trosymmetric tetragonal space group I4 /a with one complete
complex in the asymmetric unit. Four three-blade paddlewheel
SBUs {Zn (RCO } [30] surround a -oxo anion which is coordi-
nated to the axial position of the central Zn(II) centre from each
paddlewheel (Fig. 1). Four ligands (L ) each in a tripodal endo
conformation straddle the four faces of the tetrahedral array of
SBUs with each of their carboxylate functional groups bound to a
different paddlewheel. The outer axial coordination sites on
Zn(II) within the four paddlewheels are bound by a disordered
8
(l
4
-O)(L )
4
(HCO
2 2 2
) (H O)0.33(DMF)
2
]ꢁ
7
1
2
2
)
3
l
4
1
3ꢀ
Fig. 2. View of (a) overall structure and of (b) Co14(RCO
2
)
18
(
l
3
-OH)
8
(HCO
ligands are
2
)
2
core in
2
1 3ꢀ
[
6 3 8 2 2 4 2 6
Co14(L ) (l -OH) (HCO ) (DMF) (H O) ] (2-Co): the three (L )
mixture of water, DMF and formate ligands and have coordination
coloured blue, green and purple; DMF yellow; formate orange; cobalt dark blue;
oxygen red; intramolecular hydrogen bonds shown as dashed red lines. (Color
online.)
1
numbers of either four or five. The central [Zn
8
O(L )
4
] unit has a
residual +2 charge which is balanced by the coordinated formate
anions resulting from decomposition of DMF during the reaction;
both anions are crystallographically modelled at partial occupan-
cies with the remainder of the charge likely balanced by unidenti-
of a binuclear complex [Zn
2
(HL1)
2
(DMF)
4
ꢀ
]ꢁ2(DMF) (1b-Zn) which
crystallises in the triclinic space group P1 with half of a complex
in the asymmetric unit. Two crystallographically identical five-
coordinate Zn(II) centres, 7.10 Å apart, are bound by a carboxylate
group from each of the two ligands which bridge between them;
the remaining carboxylic acid groups on the third arm of each
ligand remain protonated and uncoordinated. The first coordinated
carboxylate group binds in a monodentate mode [Zn1–O38 1.943(2) Å]
whilst the second group binds in a markedly asymmetric biden-
tate-chelating mode [Zn1–O78 1.982(2) Å, Zn1–O79 2.448(3) Å].
The remaining two coordination sites on each Zn(II) centre are
occupied by DMF ligands [Zn1–O1A 2.013(2) Å, Zn1–O1B 1.999
fied disordered components. Disregarding ligation by the latter,
1
each [Zn
8
O(L )
4
] unit has distorted tetrahedral symmetry and is
chiral as a result of all four tripodal ligands being twisted in the
same direction; as the space group is centrosymmetric, complexes
of both handedness occur in the unit cell in a 1:1 ratio.
1
A H NMR spectrum of 1a-Zn dissolved in CDCl
3
was measured
in order to probe the behaviour of the complex in solution. Six
peaks observed between 5.7 and 8.2 ppm are shifted from the
1
original peak positions observed for free H
are consistent with the retention of C
3
L
in d
6
-DMSO and
3
symmetry in the ligand
environment (Fig. S1). A MALDI mass spectrum of 1a-Zn deposited
from an acetonitrile solution contains a broad peak at m/z of
(
2) Å]. Considering only the four shorter Zn–O bonds, the Zn(II)
1
+
cations have distorted tetrahedral coordination geometries. The
3
8 4 2 2
261.8 which is assigned as [Zn O(L ) (HCO )(H O)] alongside a
1
2ꢀ
two bridging ligands (HL ) are in endo-tripodal conformations
with the uncoordinated carboxylic acid groups donating a hydro-
gen bond to the unbound oxygen atom of a monodentate carboxy-
late group of a neighbouring complex [O58ꢁ ꢁ ꢁO39 2.704(4) Å].
weaker unassigned peak at a higher m/z 3878.5 and several peaks
at lower m/z (Fig. S3).
(HL1)
3
.2.2. [Zn
2
2
(DMF)
4
]ꢁ2(DMF) (1b-Zn)
The role of heating in the formation of 1a-Zn was investigated
by diffusing diisopropyl ether into a fresh solution of H
1
2
3
L
and
3.2.3. [Co14(L )
6
(OH)
8
(HCO
(DMF)
L with Co(NO
resulted in formation of a crop of pink rhombic plate-like crystals
2
)
2
(DMF)
(H O)
ꢁ6H
4
(H
]ꢁ24(DMF) (2-Ni)
O in DMF for 5 days at 85 °C
2
O)
6
]ꢁ28(DMF) (2-Co) and
2
Zn(NO O at room temperature. This resulted in the precipi-
3
)
2
ꢁ6H
2
[Ni14(L )
6
(OH)
Reaction of H
8
(HCO
2
)
2
4
2
6
1
tation of small colourless single crystals amongst amorphous
material. X-ray analysis of the single crystals showed them to be
3
3
)
2
2
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
7
Table 1
Selected torsion angles, intramolecular distances, conformations and binding modes for complexes of H
L1–4
.
3
Torsion angles [°]
Distances [Å]
/1
range
/1
/2/3 range
/2/3
d range
d average Conformation and Harris notation
average
average
mode
1
a-Zn
[Zn
8
(
l
4
-O)(L1)
]ꢁ7.75(DMF)
4
(HCO
2
)
2
(H
2
O)0.33
46.5–66.1
59.8
42.1–69.5
57.7
5.02–5.45
5.18
endo
l
6
6.1
1
1
2
1
3
1
4
1
5
1
6
5
(DMF)
2
1
1
2
b-Zn
-Co
[Zn
2
(HL )
2
(DMF)
-OH)
]ꢁ28(DMF)
4
]ꢁ2(DMF)
48.9–57.9
46.9–103.5
53.8
65.5
44.6–55.1
30.3–57.4
50.7
42.8
6.27–6.47
3.79–6.31
6.38
4.93
exo
l
2
2.1
1
5.1
1
5.1
1
4.1
1
5.1
1
5.1
1
4.1
1
6.1
1
1
1
2
1
1
2
1
1
2
1
1
2
2
[Co14(L )
O)
6
(
l
3
8
(HCO
2
)
2
(DMF)
4
endo
endo
endo
endo
endo
endo
endo
l
5
5
4
5
5
4
6
1
2
1
1
3 4
1
(H
2
6
l
l
l
l
l
l
23
23
1
2
2
24
2 1
34 5
24
1
3
1
4
2
-Ni
[Ni14(L2)
6
(l
3
-OH)
8
(HCO
2
)
2
(DMF)
4
48.2–102.3
66.8
36.5–59.0
46.0
3.84–6.30
5.13
5.19
1
2
1
3 4 5
1 1
(H
2
O) ]ꢁ24(DMF)
6
23
23
2
2
24
2
1
34
1
5
24
3
1
4
3
4
5
6
7
-Zn
-Zn
-Ni
-Co
-Fe
[Zn
NO
{[Zn
(DMF)}
[Ni -OH)
(DMF)
[Co -O)
(H
[Fe
0(DMF)
8
(l
4
-O)(L3)
(DMF)(H
4
2
O)
4
]
61.2–69.3
40.6–56.8
42.3–88.4
40.9–45.9
39.6–50.2
67.6
49.0
59.3
43.6
45.7
46.1-58.5
25.4–59.7
36.7–83.6
44.2–55.8
57.7–73.3
54.3
49.0
53.7
50.2
64.4
5.14–5.26
3.41–7.93
3.88–6.19
4.07–4.23
4.23–4.33
2
2
2
2
2
1
3
1
1
1
1
1
4
1
5
3
3
1
3
1
6
(
3
)
2
ꢁ16(DMF)
2
3
(L )
2
(DMF)(H
2
O)(C
5
H
5
N)]ꢁ
(DMF)
]ꢁ
O)]ꢁ
O)(DMF)
)]ꢁ
3.44/7.60 exo
l
4
4.1
1
5.1
1
4.1
1
3.1
1
1
1
1
1
1
3
3
1
2
4
1
1
1
1
1
1
1
1
4
5
4
1
6
n
2
5
(l
4
(L )
2
(H
2
O)
6
4
5.40
4.15
4.29
endo
endo
endo
l
5
4
3
1
1
1
4
3
3
6
4
8
(l
4
4
(L )
4
(DMF)
3
(H
2
l
l
3
2
O)ꢁ6(DMF)
4
3
(
l
3
-O)(L )
2
(H
2
2
1
which X-ray analysis showed to be [Co14(L2)
DMF) (H O)
]ꢁ28(DMF) (2-Co). The analogous reaction of H
with Ni(NO
precipitate and small green rhombic crystals which X-ray analysis
showed to be an isostructural and isomorphous material
(OH)
(HCO
)
L
3.2.4. [Zn
(
l
-O)(L3)
(DMF)(H
O)
](NO
)
ꢁ16(DMF) (3-Zn)
2
with Zn(NO O in DMF
6
8
2
2
1
8
4
4
2
4
3
2
3
(
4
2
6
3
Reaction of elongated ligand H
for 3 days at 85 °C resulted in formation of a crop of colourless
hexagonal platy crystals which X-ray analysis showed to be
3
L
3
)
2
ꢁ6H
3
)
2
ꢁ6H
2
O resulted in a mixture of an amorphous green
3
[Zn
8
(l -O)(L )
4
4
(DMF)(H
O)
2 4
](NO
3
2
) ꢁ16(DMF) (3-Zn), an analogous
2
1
[
Ni14(L )
6
(OH)
8
(HCO
2
)
2
(DMF)
4
(H
2
O)
6
]ꢁ24(DMF) (2-Ni). The com-
3
octanuclear cluster to 1a-Zn obtained using ligand H L (Fig. 1).
ꢀ
The complex crystallises in the trigonal space group R3 and con-
tains a third of an octanuclear cluster in the asymmetric unit.
Although only one enantiomer of the chiral complex appears in
the refinement model, the structure is a racemic twin with a twin
fraction of 0.52(2). The [Zn
plexes crystallise in space group P1 with an asymmetric unit con-
taining one half of a tetradecanuclear M(II) cluster. The fourteen
six-coordinate M(II) cations have distorted octahedral geometries
and are arranged in an approximately planar elliptical array (mean
deviation from plane 0.662 Å, maximum deviation 1.024 Å) with
3
8
O(L )
4
] core of the cluster has the same
the cations being bridged by a mixture of
late oxygen atoms and formate anions (Fig. 2). The coordination
l
3
-OH groups, carboxy-
topology as 1a-Zn with four tripodal ligands in endo conformations
each spanning three of the four three-blade [Zn (RCO ] paddle-
2
2 3
)
spheres of the peripheral M(II) cations are completed by monoden-
wheels. The identity of the anions which balance the +2 charge
of the octanuclear core is ambiguous: coordinated ligands at the
axial positions three of the Zn(II) centres are modelled as a disor-
dered mixture of DMF and water whilst three disordered water
ligands are coordinated at the fourth Zn(II) centre. An electron
1
3ꢀ
tate DMF or water ligands. Three ligands (L ) in tripodal endo
conformations approach the cluster from above the plane of
the elliptic array and three approach from below. Each of the three
ligands in the asymmetric unit is bound to either four or five M(II)
cations in a different fashion via a mixture of monodentate,
bridging-monodentate, chelating-bidentate, bridging-bidentate
and bridging-tridentate coordination modes which are sum-
marised in Harris notation [31] in Table 1. The three tripodal
ligands on one face of the complex are twisted in the same sense
as each other whilst the three ligands on the other face are twisted
in the opposite sense. The complex includes two bridging-triden-
tate formate ligands formed from decomposition of DMF during
ꢀ3
density peak (1.10 e Å ) close to the three coordinated water
molecules suggests that the missing counter-ion may be a disor-
dered bidentate-chelating nitrate anion but no viable refinement
model could be developed.
Despite the elongation of the three arms in H
3
L3 compared with
3 8
H L , similar geometries of the Zn O cores in 1a-Zn and 3-Zn
1
demand the intramolecular carboxylate-carboxylate distances d
in the complexed ligands to have similar values (average distances
5.18 and 5.19 Å in 1a-Zn and 3-Zn, respectively). The longer arms
the reaction. The eight
3
l -OH groups all donate intramolecular
3
3ꢀ
1 3ꢀ
hydrogen bonds to coordinated oxygen donor atoms of adjacent
carboxylate or DMF ligands. The identity of the hydroxy functional
groups in 2-Ni is confirmed by the presence of electron density
peaks associated with the hydrogen atoms; these peaks are not
apparent in electron density map of 2-Co as a consequence of
weaker diffraction data (Table 2).
of (L )
compared to (L )
result in a steeper average pitch
of the propeller twist as observed by comparing the average
1
ortho-diphenybenzene torsion angles / in the two structures
(59.8° and 67.6° for 1a-Zn and 3-Zn, respectively).
2
3.2.5. {[Zn
3
(L )
2
(DMF)(H
2
O)(C
5
H
5
N)]ꢁ6(DMF)}
n
(4-Zn)
2
2
-Co was found to be sparingly soluble in CD
3
CN allowing the
Reaction of the shorter ligand H
3
L with Zn(NO
3
)
2
ꢁ6H
2
O in DMF
1
solution behaviour of the complex to be probed by H NMR spec-
troscopy. The spectrum is dominated by large solvent peaks for
and a small amount of pyridine for 3 days at 85 °C resulted in for-
mation of colourless blocky crystals which X-ray analysis showed
2
DMF, H
2
O and diethyl ether alongside which are broad peaks
to be a 2D-coordination network {[Zn
(DMF)}
contains three Zn(II) centres and two ligands (L )
3
(L )
2
(DMF)(H
2
O)(C
5
H
5
ꢀ
N)]ꢁ6
between 1.30 and 3.60 ppm indicating seven proton environments.
The number of environments is consistent with the ligands
n
(4-Zn). The network crystallises in space group P1 and
2
3ꢀ
in the
remaining in an approximately
C
3
symmetric environment
asymmetric unit, with both ligands in exo conformations. The
observed in 2-Co whilst their upfield shifts with respect to uncoor-
structure is a (4,4)-net consisting of four-bladed paddlewheels
1
3
dinated ligand H L dissolved in d
6
-DMSO are consistent with the
{Zn
2
(RCO
2
)
4 2
ꢁ(solv) } acting as four-connected nodes and ligands
2
3ꢀ
ligand being complexed to paramagnetic Co(II) [32].
(L ) acting as linkers (Fig. 3). Each ligand in the asymmetric unit
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

8
S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
Table 2
Experimental information for single crystal X-ray structures.
1
a-Zn
1b-Zn
2-Co
2-Ni
3-Zn
Chemical formula
C
209
H
173
9
N O3
8
Zn
8
C
108
H
110
4
N O
18Zn
2
C
368
H
408Co14
N
32
O
86
C
356
H
380
N28Ni14
O
82
342 382 32 8
C H N O69Zn
M
T (K)
r
4001.59
90
1884.75
90
7480.26
90
7184.80
90
5420.89
120
Crystal system
Space group
a (Å)
b (Å)
c (Å)
tetragonal
I4 /a
44.7465 (8)
44.7465 (8
37.5201 (14)
90
triclinic
P1ꢀ
10.0073 (7
13.7375 (6
19.2412 (9)
72.604 (4)
75.194 (5)
75.943 (5)
2400.3 (2)
1 (0.5)
triclinic
P1ꢀ
triclinic
P1ꢀ
trigonal
R3
31.3629 (5
31.3629 (5)
26.5627 (4)
90
90
120
22627.5 (7)
3 (0.333)
1
18.2047 (12
22.9068 (13
24.0347 (13)
109.198 (5)
97.386 (5)
107.639 (5)
8725.6 (10)
1 (0.5)
18.5540 (4
22.8380 (5
23.8366 (4)
108.7451 (17)
98.4091 (16)
107.482 (2)
8787.1 (3)
1 (0.5)
a
(°)
b (°)
(°)
90
90
c
3
V (Å )
Z (Z )
75125 (4)
16 (1)
0
Radiation type
Cu K
1.77
a
Cu K
1.19
a
Cu K
5.78
a
Cu K
1.46
a
Cu K
1.26
a
ꢀ
1
l
(mm )
Crystal size (mm)
Reflections collected
Independent reflections
0.37 ꢃ 0.11 ꢃ 0.03
76065
34810
14121
0.107
71.8
0.616
0.086
0.292
0.30 ꢃ 0.10 ꢃ 0.05
0.35 ꢃ 0.17 ꢃ 0.03
32507
15195
6981
0.159
47.2
0.476
0.173
0.453
1.24
0.28 ꢃ 0.19 ꢃ 0.05
79309
32464
21310
0.049
71.3
0.614
0.061
0.183
0.34 ꢃ 0.29 ꢃ 0.17
64262
20491
18751
0.022
76.9
0.632
0.053
0.159
9407
9407
8287
–
Reflections [I > 2r(I)]
R
h
(
int
maximum (°)
sin h/k)maximum (Åꢀ1)
74.7
0.626
0.057
0.144
1.11
9407
565
2
2
R [F > 2
r(F )]
2
wR(F ) [all data]
Goodness-of-fit (GOF) on F2
No. of reflections
0.97
34810
2124
1.04
32464
1719
1.03
20491
920
15195
1389
No. of parameters
No. of restraints
5362
0
2996
2184
856
Largest diff. Peak/hole (e Åꢀ3)
CCDC number
0.74, ꢀ0.90
0.70, ꢀ0.63
1.18, ꢀ0.94
1.24, ꢀ0.50
1.10, ꢀ0.40
1470101
1470096
1470098
1470104
1470099
4
-Zn
5-Ni
6-Co
7-Fe
Chemical formula
C
71
H
65
5
N O
17Zn
3
C
102
H
158
5
N16Ni O
38
C
297
H383Co
N
8 39
O
68
126 3 12 26
C H140Fe N O
M
T (K)
r
1675.67
90
1889.19
150
3489.38
120
2341.78
120
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1ꢀ
triclinic
P1ꢀ
trigonal
P 3ꢀ c1
21.658 (3)
21.658 (3)
44.608 (6)
90
90
120
18120 (6)
4 (0.333)
monoclinic
P2/c
27.1936 (14)
10.9124 (7)
36.7627 (19)
90
10.400 (12)
20.06 (3)
20.73 (3)
112.33 (3)
91.561 (11)
99.563 (19)
3927 (9)
14.8417 (5)
15.7060 (4)
21.3256 (6)
90.733 (2)
104.580 (3)
100.444 (2)
4722.4 (2)
2 (0.5)
a
(°)
b (°)
(°)
90
90
c
3
V (Å )
Z (Z )
10564.9 (10)
4 (1)
0
2 (1)
Radiation type
Synchrotron k = 0.6889 Å
0.99
Synchrotron k = 0.6889 Å
0.97
Cu K
6.18
a
Synchrotron k = 0.6889 Å
0.49
ꢀ
1
l
(mm
)
Crystal size (mm)
Reflections collected
Independent reflections
0.2 ꢃ 0.2 ꢃ 0.2
24631
8143
6127
0.082
20.8
0.500
0.121
0.393
0.05 ꢃ 0.02 ꢃ 0.02
61728
31529
22545
0.030
32.1
0.772
0.099
0.282
0.05 ꢃ 0.05 ꢃ 0.03
45639
10244
2121
0.375
74.4
0.625
0.143
0.458
0.96
0.05 ꢃ 0.03 ꢃ 0.01
12858
12858
8045
–
21.3
0.526
0.142
0.403
1.33
Reflections [I > 2
r
(I)]
R
h
(
int
maximum (°)
sin h/k)maximum (Åꢀ1)
2
2
R [F > 2
r(F )]
2
wR(F ) [all data]
Goodness-of-fit (GOF) on F2
No. of reflections
1.52
8143
823
1.06
31529
1233
10244
684
12858
1036
No. of parameters
No. of restraints
2224
2269
868
1961
Largest diff. Peak/hole (e Åꢀ3)
CCDC number
1.22, ꢀ1.20
2.17, ꢀ2.09
0.64, ꢀ0.51
1.56, ꢀ0.78
1470097
1470102
1470100
1470103
coordinates via two carboxylate groups to adjacent Zn(II) sites of a
single paddlewheel and a third carboxylate group is coordinated to
a different paddlewheel. Of the three types of paddlewheel in the
asymmetric unit, two are coordinated at adjacent sites by pairs
of carboxylate groups from two ligands, thus topologically making
them linkers, whilst the third type of paddlewheel is coordinated
by carboxylate groups from four different ligands, making it a
four-connected node. The axial Zn(II) coordination sites of the
four-connected paddlewheel units are occupied by pyridyl ligands,
with the axial coordination sites of the linking paddlewheels
occupied by DMF and water ligands. The centroid–centroid
distances between the four-connected nodes along the edges of
the (4,4) net are 21.0 and 20.7 Å and the internal angles of the
net are 112.1° and 67.2°. The (4,4) nets are stacked directly on
top of each other resulting in narrow pores containing disordered
solvent running through the holes in the nets.
The ability of ligand (L ) to coordinate at adjacent positions of
a Zn(II) paddlewheel is permitted by the 90° bite angle between
the carboxylate groups in the 1,3-bis-carboxyphenylbenzene unit,
a motif previously seen in a W-shaped tetracarboxylic acid ligand
2
3ꢀ
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
9
described by Zhang [33]. In 4-Zn the twist between the carboxylate
groups and phenyl rings described by torsion angle / (range
described in this work. Two of the carboxylate groups on each
ligand are oriented towards each other allowing them to bridge
3
2
5.4–59.7°) indicates unusually large deviations from planarity
3
between Ni(II) cations in the same triangular Ni array. The third
which are necessary to align the plane of the carboxylate groups
with the Zn-Zn axis of the paddlewheel moiety.
arm of each ligand and its pendant carboxylate group adopt highly
unusual near-perpendicular twists as described by torsion angles
1
3
/
(82.8° and 84.5°) and / (84.2° and 84.1°) which enable the
carboxylate groups to bridge the two Ni(II) cations at each end of
the structure. Torsion angles so close to 90° in these situations
are rare: a search of the CSD [34,35] using Mogul [36] returns no
other examples of transition metal bound phenylcarboxylates with
torsion angles greater than 80°; the next highest value reported is
2
3
.2.6. [Ni
Reaction of H
5
(
l
-OH)
4
(L ) (H
2 2
O)
6
(DMF)
4
]ꢁ6(DMF) (5-Ni)
2
3
L with Ni(NO
3
)
2
ꢁ6H
2
O in DMF for 5 days at 80 °C
did not result in the formation of a precipitate. Diisopropyl ether
was diffused into the resulting green solution leading to formation
of a small number of green block-like crystals which were shown
by X-ray analysis to be [Ni
5-Ni). The asymmetric unit in space group P1 contains one pen-
7
8.8° in a coordination framework containing Zn(II) and benzene-
2
5
(l-OH)
4
(L )
(H
2 2
6
O) (DMF)
4
]ꢁ6(DMF)
1
,3,5-tricarboxylic acid [37].
ꢀ
(
tanuclear cluster.
The five six-coordinate Ni(II) cations have distorted octahedral
geometries and lie in a plane (mean deviation from plane
3.2.7. [Co
Reaction of ligand H
at 80 °C resulted in formation of black block crystals which were
8
(
l
4
-O)
4
(L4)
4
(DMF)
3
(H
2
O)]ꢁ3(H
2
O)ꢁ6(DMF) (6-Co)
4
3
L with Co(NO
3
)
2
ꢁ6H O in DMF for 2 days
2
0
(
.002 Å) arranged as two isosceles triangles with a shared vertex
short edge average Niꢁ ꢁ ꢁNi distance 2.98 Å, long edge average
Niꢁ ꢁ ꢁNi distance 3.60 Å). A -OH group is found at the centre of
each Ni triangle whilst a -OH bridges two Ni(II) centres along
the short edge of each triangle. The two -OH groups direct their
hydrogen atoms towards the central phenyl rings of each ligand
4
shown by X-ray analysis to be [Co
3(H
trigonal space group P3c1 with one third of the complex in the
8
(
l
4
-O)
4
(L )
4
(DMF)
3
(H
2
O)]ꢁ
l
l
2
3
2
O)ꢁ6(DMF) (6-Co). The octanuclear cluster crystallises in the
ꢀ
3
4
3ꢀ
l
3
asymmetric unit. Four ligands (L ) in tripodal endo conforma-
tions surround a Co cubane core (Fig. 4) in which four vertices
4 4
O
2
3ꢀ
(
Hꢁ ꢁ ꢁring centroid distances 2.97 and 2.98 Å). A ligand (L ) strad-
are occupied by six-coordinate Co(III) cations with distorted octa-
hedral geometries whilst the other four vertices are occupied by
dles each face of the pentanuclear array with all six carboxylate
functional groups spanning two Ni(II) cations in bidentate-bridging
l
4
-O oxo anions (average Co–O bond length along cube edges
1.90 Å). Each of the four -O cube corners is coordinated to a
peripheral five-coordinate Co(II) cation with distorted trigonal
bipyramidal geometry resulting in a Co core isostructural with
2
3ꢀ
modes. The two ligands (L ) adopt identical endo conformations
with approximate C symmetry in contrast to the C symmetry
exhibited by the other ligands with tripodal endo conformations
l
4
S
3
8 4
O
2
Fig. 3. View of (a) structure of {[Zn
(
3 2
(L ) (DMF)(H
2 5
O)(C H
5
N)] (4-Zn) showing one repeat unit of the (4,4)-net highlighting the inter-node distances and angles: the ligands
2
3ꢀ
L ) are coloured yellow and purple; DMF yellow; pyridine grey; zinc black; oxygen red. (b) View of conformations and coordination environments of the two ligands
in the asymmetric unit of 4-Zn with phenyl-carboxylate torsion angles / highlighted. View of (c) overall structure and of (d) Ni (l-OH) (RCO ) (H O) core in
5 4 2 6 2 6
3
2
[
Ni
5
(l-OH)
4
(L )
2
(H
2
O)
6
(DMF)
4
] (5-Ni): ligands are coloured blue, green; DMF yellow; nickel purple; oxygen red; hydrogen bonds red dashed lines; O–Hꢁ ꢁ ꢁphenyl face
3
interactions grey dashed lines. (e) Conformations and coordination environments of one ligand from 5-Ni with phenyl-carboxylate torsion angles / highlighted. (Color online.)
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

1
0
S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
a cluster containing mono-functional benzoate ligands reported by
Christou et al. [38]. The carboxylate groups of all four ligands coor-
dinate in a bidentate-bridging fashion with three of their oxygen
atoms chelated to the same central Co(III) cation and the other
oxygen atom of each carboxylate coordinated to a peripheral
Co(II) cation. This tris-chelating coordination mode is made
possible by the meta-substitution pattern of the carboxylic acid
4
functional groups in H
3
L
in contrast to the para-substitution
1
3
3 3 .
found in H L and H L This geometry means that in 6-Co, despite
ligand (L ) having a shallow propeller pitch (described by an
average torsion angle / of 43.6°), the intra-ligand distances d
4
3ꢀ
1
between the carboxylate carbon atoms are very short with an aver-
age value of 4.15 Å. Each meta-substituted phenyl ring of the
4
3ꢀ
ligands (L ) within 6-Co is involved in an aromatic p–p stacking
interaction with the equivalent ring of a neighbouring ligand (ring
centroid–centroid distance 4.62 and 4.29 Å, centroid-ring mean
plane distance 3.72 and 3.90 Å) with a total of six such interactions
occurring across the complex. The assignment of the oxidation
states of the cobalt atoms is confirmed by bond-valence sum
analysis [39,40] indicating an average valence of +3.12 for the
inner six-coordinate cations and an average valence of +2.01 for
the outer five-coordinate cations. The requirement for atmospheric
2
O to oxidise the Co(II) starting material during formation of the
mixed valence species 6-Co was confirmed by an attempted
reaction in oxygen-free conditions: no precipitate was formed even
after heating the reaction mixture at 80 °C for 5 days.
The molecular packing in the structure of 6-Co features alter-
nating offset trigonal layers of clusters resulting in a hexagonal
close-packed arrangement of the roughly spherical species
(Fig. S4). The packing leaves large intermolecular cavities con-
nected by small hexagonal channels running parallel to the c-axis.
The total fraction of potential void space in the structure after
removal of all non-coordinated solvent and exchange of coordi-
nated DMF for water is calculated as 30.6% by PLATON [41] using
a 1.20 Å probe after input of a manually modified structure file. A
bulk sample of 6-Co was solvent-exchanged with acetone and
dried in air before a PXRD pattern was measured. The pattern indi-
cated retention of crystallinity and was indexed to give a unit cell
showing good agreement with that of the single crystal X-ray
structure (Fig. S5). The observation that this large supramolecular
complex is stable to solvent exchange and solvent loss is explained
by the large numbers of weak intermolecular aromatic p-p stack-
ing and edge-face interactions. Each cluster makes in total six
stacking interactions and three edge-face interactions with its six
neighbours, giving a total of nine stabilising contacts per molecule.
4
3
.2.8. Fe
3
(l
3
2
-O)(L ) (H
2
O)(DMF)
2
)]ꢁ10(DMF) (7-Fe)
4
Reaction of ligand H
for 2 days at 80 °C resulted in formation of small brown crystals
3
L
with Fe(NO O (n = 6–9) in DMF
3
)
3
ꢁnH
2
amongst an amorphous precipitate. Single crystals taken
directly from the mixture were shown by X-ray analysis to be
4
[
3
Fe (l
3
-O)(L )
2
(H
2
O)(DMF)
2
)]ꢁ10(DMF) (7-Fe). The trinuclear
cluster crystallises in the monoclinic space group P2/c with one
complete complex in the asymmetric unit. The core of the cluster
adopts the common [Fe O(RCO ) ] basic carboxylate motif previ-
3 2 6
ously seen in both discrete complexes [42,43] and as a 6-connected
connectors in MOFs [44,45]. Three iron centres in an isosceles tri-
angular array (Feꢁ ꢁ ꢁFe distances 3.262(3), 3.338(2) and 3.339(2) Å)
surround a central
3
l -O with which they are approximately co-pla-
nar (mean deviation from Fe
3
O plane 0.006 Å). The iron centres are
all 6-coordinate and have distorted octahedral geometries com-
prising four carboxylate oxygen atoms from different groups, the
oxo oxygen atom and a neutral water molecule or DMF oxygen
Fig. 4. View of (a) overall structure and (c) Co
O) (L ) (DMF) (H
4 4 3 2
8
(
l
4
-O)
O)] (6-Co): ligands are coloured orange, blue, purple and green;
DMF yellow; cobalt (III) dark teal; cobalt(II) purple; oxygen red. View of (b) overall
4 2 8 4
(RCO )12 core in [Co (l -
4
3
4
3 3 2 6 3 2 2 2
structure and (d) Fe (l -O)(RCO ) core in [Fe (l -O)(L ) (H O)(DMF) )] (7-Fe):
ligands are coloured blue and orange; DMF yellow; iron(II) green; iron(III) brown;
4
3ꢀ
atom. A ligand (L ) in a tripodal endo conformation caps each
side of the triangular array, with the edges of the triangle bridged
oxygen red. (Color online.)
Please cite this article in press as: S.P. Argent et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.04.029

S.P. Argent et al. / Polyhedron xxx (2016) xxx–xxx
11
by a carboxylate group from each ligand. Both tripodal ligands are
twisted in the same sense, resulting in a chiral complex, but the
structure is a racemic mixture [twin fraction 0.279(6)] with com-
plexes of both chiralities represented in the unit cell. Bond-valence
sum analysis [39,40] of the three iron centres leads to the identifi-
cation of mixed oxidation states with Fe1 (BVS sum + 2.92) and
Fe2 (BVS sum + 2.89) being assigned as Fe(III) and Fe3 (BVS sum + 2.12)
being assigned as Fe(II). The mixed oxidation state arrangement
results in 7-Fe being a charge-balanced neutral complex, but the
absence of an associated counterion in the structure cannot be
used to support the assignment owing to the disorder in the
remainder of the unit cell. The structure of 7-Fe permits a clear
view of the influence of the mixed oxidation states on the bond
six ligands in endo conformations act in multiple bridging modes
between M(II) cations. The differing conformations of the ligands
in these complexes allow them to saturate all the M(II) coordina-
tion sites of the low symmetry clusters. Reaction of the shorter
2
ligand H
a
3
L
with Ni(NO
3
)
2
ꢁ6H
2
O at 85 °C resulted in formation of
2
pentanuclear cluster [Ni
5
(l
-OH)
4
(L )
(Ni-5) where the ligands (L ) are in endo conformations with
approximate C symmetries. The stereochemical requirements of
the Ni core results in both ligands exhibiting unprecedented
2
(H O)
2 6
(DMF)
4
]ꢁ6(DMF)
2
3ꢀ
s
5
torsion angles close to perpendicular between the central phenyl
1
ring and phenylcarboxylate arm (/ , 82.8° and 84.5°), and also
between the phenylcarboxylate ring and carboxylate functional
3
group (/ , 84.2° and 84.1°).
lengths and geometries of the Fe
3
O core; in many reported
Reaction of meta-substituted ligand H
3
L4 with Co(NO
3
)
2 2
ꢁ6H O
examples of mixed oxidation state cores the clusters are located
on crystallographic special positions, thereby obscuring the impor-
tant deviations from perfect threefold symmetry by showing only
average atomic positions [46]. This is only the third example in
the Cambridge Structural Database of a ligand able to bind in a
bridging mode between multiple coordination positions of an
at 80 °C resulted in formation of a mixed oxidation state octanu-
4
clear cluster [Co
8
(l -O)
4
4
(L )
(DMF) (H
4 3 2
O)]ꢁ3(H O)ꢁ6(DMF) (6-Co)
2
4
3ꢀ
in which four ligands (L ) in endo conformations surround a
Co(III) cubane core. The meta-substitution pattern of ligand
makes it possible for the three carboxylate groups to adopt
4 4
O
4
3
H L
the tris-chelating mode necessary to coordinate to the compact
cluster. The potentially porous bulk material features multiple
intramolecular aromatic stacking and edge-face interactions and
retained its crystallinity and packing structure upon solvent
[
3 2 6
M O(RCO ) ] cluster [47,48] and the first example of a ligand able
to bridge three positions. The stabilisation conferred upon the
complex by the match between the ligand and cluster geometries
offers enhanced opportunities to investigate and exploit the rich
electrochemistry and magnetochemistry of this motif in its roles
as an SBU [45], enzyme mimic [48] and catalyst [49].
exchange with acetone. Reaction of the same meta-substituted
4
ligand H
3
L
with Fe(NO
3
)
3
ꢁnH
-O)(L )
in which a ligand caps each triangular face of the Fe
2
O at 80 °C resulted in formation of
4
a trinuclear cluster [Fe
3
(l
3
(H
2 2
O)(DMF)
2
)]ꢁ10(DMF) (7-Fe)
3
O core. The
iron centres in the cluster have mixed oxidation states with two
Fe(III) cations and one Fe(II) cation resulting in a charge-neutral
complex. This is the first example of a tritopic ligand able to cap
the faces of the ubiquitous basic carboxylate M O species leading
3
to the possibility stabilising a wider variety of these widely studied
motifs.
4
. Conclusions
The family of tris-carboxylic acid ligands H
3
L1–4 reported herein
by acting as tripodal
1
has built upon the earlier promise of H
3
L
polytopic ligands to form a wide variety of polynuclear metallo-
clusters when complexed with the first-row transition metal
centres Fe(II/III), Co(II/III), Ni(II), Cu(II) and Zn(II). The threefold
symmetric ligands share a common ortho-substitution pattern in
the attachment of their three arms to a central 1,3,5-substituted
phenyl core. This motif has shown itself to be a versatile tool for
the construction of polynuclear clusters, allowing the ligands to
position their three carboxylic acid binding sites in close proximity
to each other. The distance d between the binding sites in the semi-
rigid ligands is seen to vary to match the geometric demands of the
cluster, with carboxylate carbon–carbon separations varying
between 3.84 and 7.93 Å across the nine transition metal complex
structures described.
Acknowledgements
We thank EPSRC UK (award numbers EP/K038869, EP/I011870),
ERC (ERC-2008-AdG 226593 to MS) and General Motors for fund-
ing. NRC acknowledges the receipt of a Royal Society Wolfson
Merit Award. We thank Sihai Yang for help collecting synchrotron
PXRD data.
Appendix A. Supplementary data
Reaction of ligand H
3
L1 with Zn(NO
3
)
2
ꢁ6H
2
O at 85 °C resulted in
CCDC 1470096–1470104 contain the supplementary crystallo-
graphic data for complexes 1–7. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/10.
1
formation of an oxo-centred octanuclear cluster [Zn (l -O)(L )
8 4 4
(
(
HCO
L )
2
)
2
(H
2
O)0.33(DMF)
2
]ꢁ7.75(DMF) (1a-Zn) with four ligands
1
3ꢀ
each coordinated to a three-blade {Zn (RCO } paddle-
2
2 3
)
wheel. Reaction of the same metal and ligand at ambient temper-
ature resulted in a different binuclear complex [Zn
1
2
(HL )
2
(DMF)
4
]ꢁ
2
(DMF) (1b-Zn) containing coordinatively unsaturated ligands
1
2ꢀ
3
1
016/j.poly.2016.04.029.
(HL ) . Reaction of extended ligand H
3
L
with Zn(NO
3
)
2
ꢁ6H
2
O at
8
5 °C resulted in formation of an isostructural octanuclear cluster
3
[
Zn
8 4
(l
-O)(L )
4
(DMF)(H
O)
2 4
](NO
3
)
2
ꢁ16(DMF) (3-Zn) and demon-
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