Self-assembly of Dinuclear Double-stranded Copper(II) Helicates with 3-Ethoxy-2-hydroxyphenyl Substituted Diimines. Synthesis, Molecular Structure, and Host-guest Recognition of H2O

Article abstract of DOI:10.1002/zaac.201500547

Reaction of equimolar amounts of Cu(OAc)₂·H₂O and bis[4-(3-ethoxysalicylideneamino)phenyl]methane (H₂L¹) or bis[4-(3-ethoxysalicylideneamino)phenyl]sulfide (H₂L²) in a 1:1 THF/MeOH mixture leads to the formation of structure-analogous Cu^II helicates of the composition [{Cu₂L₂}(H₂O)₂}]·4H₂O. The helicates form left- and right-handed hydrogen bonded strands using the bound water molecules as glue. Finally, a compact 3D arrangement of the molecules is achieved by weak π...π and CH...π interactions. The Cu^II ions possess a strongly distorted tetrahedral arrangement with a N₂O₂ donor set of the involved diimines. In addition, the molecular structure of the ligand H₂L² was determined and solution studies of the complex formation using UV/Vis and ESI-MS were performed.

Full text of DOI:10.1002/zaac.201500547

Journal of Inorganic and General Chemistry
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Zeitschrift für anorganische und allgemeine Chemie
DOI: 10.1002/zaac.201500547
Self-assembly of Dinuclear Double-stranded Copper(II) Helicates with
3-Ethoxy-2-hydroxyphenyl Substituted Diimines. Synthesis, Molecular
Structure, and Host-guest Recognition of H2O
Norman Kelly,[a] Johanna Schulz,[a] Kerstin Gloe,[a] Thomas Doert,[a] Karsten Gloe,*[a]
Marco Wenzel,[a] Margret Acker,[a] and Jan J. Weigand*[a]
Dedicated to Professor F. Ekkehardt Hahn on the Occasion of His 60th Birthday
Keywords: Schiff bases; Copper; Self-assembly; Helicates; Host-guest recognition
Abstract. Reaction of equimolar amounts of Cu(OAc)2·H2O and cules as glue. Finally, a compact 3D arrangement of the molecules is
bis[4-(3-ethoxysalicylideneamino)phenyl]methane (H2L1) or bis[4-(3- achieved by weak π···π and CH···π interactions. The CuII ions possess
ethoxysalicylideneamino)phenyl]sulfide (H2L2) in a 1:1 THF/MeOH
a strongly distorted tetrahedral arrangement with a N2O2 donor set of
mixture leads to the formation of structure-analogous CuII helicates of the involved diimines. In addition, the molecular structure of the ligand
the composition [{Cu2L2}(H2O)2}]·4H2O. The helicates form left- and
H2L2 was determined and solution studies of the complex formation
right-handed hydrogen bonded strands using the bound water mole- using UV/Vis and ESI-MS were performed.
two arms with bidentate metal binding sites which are linked
Introduction
by different flexible spacer units, mainly diphenyl methane,
diphenyl ether, and diphenyl sulfide.[5,6] Numerous transition
metal helicates with bis(2-pyridylimine) ligands are described
in the literature.[7] Their molecular structure and resulting
properties strongly depend both on the involved components
and the chosen experimental conditions. We have shown that
CuII sulfate forms hexanuclear circular meso-helicates with
bis(2-pyridylimine) derivatives,[8] whereas AgI perchlorate re-
acts with these ligands to single-stranded helicates, metallo-
cycles, and coordination polymers depending on the experi-
mental conditions.[9] Another related structural motif in this
context is represented by the bis(2-hydroxyarylimine) ligand
type.[10] In this case neutral double-stranded helicates with CuII
and ZnII have been isolated and characterized.[11–14] The intro-
duction of methoxy or ethoxy substituents in 3-position of the
aryl function leads to potentially four binding cavities for
metal ions in the helicate, two with a N2O2 and two with an
O4 coordination sphere.
The isolated complexes are either homodinuclear {CoII,
CuII, ZnII with N2O2 donor set}[15,16] or heterotetranuclear
{N2O2: CuII / O4: GdIII} double-stranded helicates.[17,18]
As part of our ongoing studies in this research field we have
synthesized the 3-ethoxy-2-hydroxyphenyl-substituted di-
imines H2L1 and H2L2 having diphenyl methane or diphenyl
sulfide spacer units, respectively (Scheme 1).
Helical structures play an important role in nature. Such in-
herently chiral systems are essential for life. For example, the
DNA double helix is responsible for the genetic information in
all living organisms; other natural macromolecules, like RNA,
peptides or proteins, form also helical assemblies, which are
involved in different biological processes. Now supra-
molecular chemistry allows the design and the synthesis of
interesting artificial helical systems by molecular recognition
and self-assembly of suitable building blocks using coordinate
bonding in combination with different weak noncovalent inter-
actions.[1] Especially metal based di- and polynuclear helicates
in a double-, triple-, and quadruple-stranded or circular ar-
rangement have been of great interest and the number of rel-
evant publications is always rising.[2–4] Such structural motifs
are characterized by specific stereochemical, electronic, cata-
lytic, magnetic, or optic properties applicable in biology, medi-
cine, chemistry, and materials science.
Among the discrete helical systems mentioned above, transi-
tion metal complexes with multifunctional Schiff base ligands
are widely employed. Typical examples are compounds having
* Prof. Dr. K. Gloe
Fax: +49-351-463-31478
E-Mail: karsten.gloe@chemie.tu-dresden.de
* Prof. Dr. J. J. Weigand
E-Mail: jan.weigand@tu-dresden.de
[a] Department of Chemistry and Food Chemistry
TU Dresden
H2L1 was first described in 2004 by Novitchi et al.[18]
whereas H2L2 was synthesized for the first time within this
work. In order to better understand molecular recognition and
self-assembly processes of these potential helicands their com-
plex formation with CuII was studied. In this paper we report
01062 Dresden, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201500547 or from the au-
thor.
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Molecular Structure of H2L2
The molecular structure of the ligand H2L2 is shown in Fig-
ure 1. The ligand is arranged in the enol-imine form and has a
typical characteristic V-shape similar to related diimine ligands
with different linker functions (–S–, –O–, –CH2–) and chang-
ing substituents in 3- and 5-position.[19,20] It is interesting to
note, that upon cooling of the solid ligand a color change is
observed indicating a thermochromism between both tauto-
mers as observed previously for similar ligands.[20,21]
Scheme 1. Structural formulas of studied diimines H2L1 and H2L2.
the crystal structures of H2L2 and the neutral dinuclear
double-stranded CuII helicates [{Cu2(L1)2}(H2O)2]·4H2O and
[{Cu2(L2)2}(H2O)2]·4H2O. Both CuII complexes have an anal-
ogous molecular structure and show remarkable host-guest re-
cognition of water, which is a requirement for the observed
hydrogen bonded linkage of the helicates.
Figure 1. ORTEP drawing of the molecular structure of H2L2 (50%
probability level).
Results and Discussion
The asymmetric unit of H2L2 contains four independent li-
gand molecules with slightly different bond lengths and angles.
The molecules are stabilized by two strong intramolecular
hydrogen bonds OH···N between the hydrogen atoms of the
OH groups and the imine nitrogen atoms. In the different li-
gands the OH···N distances ranges between 1.81 Å and 1.86 Å
and for the O–H–N angles values between 144° and 147° are
observed. The molecules are organized in V-shaped assemblies
as a result of C–H···O hydrogen bonds (2.44–2.72 Å), π–π in-
teractions (3.77–3.80 Å; 4.58 Å, 4.59 Å) between aromatic
rings of spacer and phenyl substituents, and C–H···π interac-
tions (2.67–3.49 Å) between the terminal phenyl substituents
(Figure 2). A dense 3D packing motif results from the linkage
of opposite arranged V-shaped assemblies in groups of four
different ligands by weak C–H···O hydrogen bonds (2.68 Å,
2.69 Å) (Figure 3).
Synthesis of H2L1, H2L2, and their CuII Helicates
The hexadentate Schiff bases H2L1 and H2L2 were synthe-
sized by the standard Schiff base condensation of 4,4Ј-
diaminodiphenyl methane and 4,4Ј-diaminodiphenyl sulfide
with 3-ethoxy-2-hydroxy-benzaldehyde in ethanol, respec-
tively (Scheme 2). This synthetic route was already used by
Novitchi et al. for the synthesis of H2L1.[18] In our case the
procedure was slightly modified by using a small excess of 3-
ethoxy-2-hydroxy-benzaldehyde. Reaction of both Schiff base
ligands with Cu(OAc)2·H2O in a THF/methanol mixture
(v/v = 1:1) gave the brown structure-analogous double-
stranded CuII helicates with comparable composition,
[{Cu2(L)2}(H2O)2]·4H2O, in moderate yields. Single crystals
suitable for X-ray crystallography were obtained by slow dif-
fusion of diethyl ether (H2L2) or diethyl ether/hexane (v/v =
1:1) (helicates) into corresponding solutions of the products.
Scheme 2. Synthetic routes for the ligands H2L1 and H2L2 as well as for the complexes [{Cu2(L1)2}(H2O)2]·4H2O and
[{Cu2(L2)2}(H2O)2]·4H2O.
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Molecular Structure of the CuII Helicates
The molecular structure of the CuII complex with H2L1 is
depicted in Figure 4. The complex of the composition
[{Cu2(L1)2}(H2O)2]·4H2O forms a neutral dinuclear double-
stranded helicate. The two CuII ions in the molecule are coor-
dinated in a strongly distorted tetrahedral arrangement by the
N2O2 donor set based on two deprotonated ligand molecules
in the helicate. Such a distorted tetrahedral arrangement of the
central CuII atom is indicated by the parameter τ4,[22] which
are 0.50 for Cu1 and 0.52 for Cu2. The bond lengths Cu–O are
slightly shorter (1.89 Å and 1.90 Å) than the Cu–N distances
(1.96 Å and 1.97 Å). These results are in agreement
with related CuII complexes recently published in the litera-
ture.[5,14–16,18] However, the Cu···Cu separation is with 11.53 Å
significantly shorter as in the structure related helicates (the
data are given in Table S11, Supporting Information). The heli-
cal twist of the ligands around the two central CuII atoms,
defined by the dihedral angle Cu(1)–N(1)–N(2)–Cu(2), is
169.4°. Two weak intramolecular π···π contacts (3.99 Å and
4.06 Å) and one CH···π (3.41 Å) interaction between the aro-
matic spacer groups of the two ligand molecules contribute to
the stabilization of the helicate.
Figure 2. Different molecules of H2L2 and their intermolecular inter-
actions.
Figure 3. Packing views of the four different molecules of H2L2.
An interesting observation is that the isolated CuII helicate
recognizes and binds two water molecules, O5 and O6, by
hydrogen bonds in the two peripheral cavities with O4 donor
set (Figure 4 and Figure 5). The resulting bifurcated O–H···O
bonds are relatively strong with distances of 2.07 Å and 2.61 Å
as well as 2.12 Å and 2.50 Å (Table 1). Additional, partially
disordered, water molecules are connected to these tightly-
bonded solvent molecules so that hexameric water clusters
are found (Figure 5). These water clusters can be regarded as
glue which ties adjacent helicates to one-dimensional strands
(Figure 6).
Figure 4. ORTEP drawing of the molecular structure of
[{Cu2(L1)2}(H2O)2]·4H2O (50% probability level).
Figure 5. Linking pattern of two helicate molecules based on the formation of hexameric water clusters (hydrogen atoms of disordered H2O are
not shown).
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Table 1. Intramolecular hydrogen bonds /Å,° in [{Cu2(L1)2}(H2O)2]·
4H2O. Symmetry operator (1–x, y, 1/2–z) generates equivalent atoms
that are marked with #.
It should be mentioned, that the short distances between
Cu(1) and peripheral aromatic units (3.88 Å) indicate a weak
CuII···π contact, which additionally stabilizes the assembly.
However, in the case of the second metal ion Cu(2) such inter-
actions are not observed.
Altogether, the discussed interactions between the strands
lead to the formation of 2D layers. From that compact 3D
assemblies are formed by weak CH···π interactions [C(28)–
H(28)···Cg(8)] between neighboring layers.
D–H···A
D–H
H···A
D···A
D–H···A
O(5)–H(51)···O(3)#
O(5)–H(51)···O(4)#
O(6)–H(61)···O(1)#
O(6)–H(61)···O(2)#
0.82
0.82
0.82
0.82
2.07
2.61
2.50
2.12
2.812(4)
3.306(2)
3.191(2)
2.855(3)
151
144
143
149
The molecular structure of the CuII helicate with H2L2 looks
very similar to that with H2L1 (Figure S2, Supporting Infor-
mation). In comparison to [{Cu2(L1)2}(H2O)2]·4H2O Cu–N
and Cu–O bond lengths (Table S5) and related angles are only
slightly different. Consequently, the CuII ions show also a
strongly distorted tetrahedral arrangement. The interesting re-
cognition of a water molecule by the outer O4 cavity is ob-
served, too. It seems and this is somewhat surprising, the influ-
ence of the spacer element, –S– instead of –CH2–, between the
imine arms is only marginal.
Figure 6. Strand-like arrangement of linked helicates in the packing
of [{Cu2(L1)2}(H2O)2]·4H2O.
The O···O distances within the water clusters are in the
range of 2.63 Å to 3.38 Å indicating a comparatively stable
interlinking. Recently, Constable et al. found a similar molecu-
lar recognition behavior for a water molecule by the 1:1 com-
Solution Studies of Complex Formation of CuII with H2L1
and H2L2
In order to characterize the complex formation of CuII with
plex of CuII with N,NЈ-(1R,2R)-(–)-1,2-cyclohexylenebis(3- the diimine ligands H2L1 and H2L2 in solution UV/Vis spec-
ethoxysalicylideneamine).[23,24] In this case the interaction troscopic studies combined with electrospray ionization mass
with a second complex molecule can be achieved by hydrogen spectroscopy measurements were performed. The goal was to
bonding of naphthalene-2,6-dicarboxylic acid with both water determine the composition of the formed complexes in solution
molecules bound by the CuII complex.[24]
Figure 7 shows three different representations of the packing
and compare it with the results in the solid state.
Figure 8 shows the UV/Vis spectra of H2L1 at changing
motif of the CuII helicate. In the isolated achiral crystal a race- concentration ratios of CuII and ligand in THF/methanol (v/v
mic mixture of both left- and right-handed enantiomers is pres- = 1:1). The absorption spectrum of H2L1 exhibits three bands
ent. There are weak intermolecular π···π and CH···π interac- at 230 nm, 280 nm, and 322 nm and a shoulder at about
tions involving the aromatic spacer groups, the peripheral 360 nm. Upon addition of CuII the ligand band at 230 nm de-
phenyl rings and the ethoxy substituents of adjacent strands creases and is red-shifted about 10 nm, while the band at
(Figure S1, Supporting Information). These interactions are 280 nm shows only a slight red-shift and passes into the shoul-
generated by the partial displacement of neighboring complex der. In contrast to this, the decreasing absorption band at
molecules in the strands. Most of them are characterized by 322 nm undergoes a bathochromic shift about 22 nm. The ad-
long Cg···Cg or Cg···H distances and great displacement angles dition of CuII leads also to a new broad absorption band at
β or γ. Only the interaction C(30)–H(30A)···Cg(7) (Cg···H 410 nm which is representative for the formed CuII complex.
2.72 Å; γ ≈ 2°) is stronger.
Using Job’s method it is possible to conclude on the composi-
Figure 7. Different views of the packing in [{Cu2(L1)2}(H2O)2]·4H2O (H2O molecules and hydrogen atoms are not shown).
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tion of the complex.[25] The resulting Job plot at 410 nm has a high extraction capability of both ligands for CuII at pH =
a maximum in absorbance for the CuII complexation with 7.7. That is also a proof of sufficient complex stability and
H2L1 at xCu = 0.5. This value points to a preferred formation of lipophilicity of the relevant extracted complexes in solution.[26]
1:1 complex species between CuII and H2L1 under the chosen The experimental details are given in the Supporting Infor-
experimental conditions. Furthermore, the absorption spectra mation (Table S13).
show several isosbestic points at 242 nm, 257 nm, and 388 nm,
The latter is saturated at xCu = 0.5, which demonstrates the
formation of a 1:1 complex, too. However, the saturation of
the two other isosbestic points take place at xCu = 0.35 indicat-
ing the presence of a second complex species in the solution.
Conclusions
Two dinuclear double-stranded CuII helicates with analo-
gous structure were synthesized and characterized in solution
and solid state. Each central CuII atom is coordinated in a
strongly distorted tetrahedral arrangement by a N2O2 donor set
of two ligand molecules. The helical orientation of the ligands
leads to the formation of two peripheral cavities having an O4
donor set, which is pre-organized for the recognition and bind-
ing of H2O through hydrogen bonding. Besides the hydrogen-
bond donor function to the ligand the H2O guest molecule can
act also as a hydrogen-bond acceptor towards two further H2O
molecules in the lattice. Finally, hexameric water clusters are
formed which allow the self-assembling of the helicates in
polymeric strands. These strands interact among each other by
weak hydrogen bonds and π–π contacts. In the packing the
strands are oriented alternately left- and right-handed resulting
in an achiral crystal.
UV/Vis and ESI-MS studies in THF/methanol (v/v = 1:1)
are consistent with the crystallographic results and show for
both ligands also the preferred formation of 2:2 complex spe-
cies in solution.
Experimental Section
Methodology: Elemental analyses were performed with an EA 3000
Euro Vector (HEKATECH) and a Vario Micro Cube (Elementar). The
melting points were determined with a Melting Point M-560 (Büchi).
The NMR spectra were measured with a DRX-500 (Bruker). For UV/
Vis studies a Lambda 25 (Perkin-Elmer) spectrophotometer was used.
Mass spectra were recorded with an ESQUIRE-detector (Bruker)
operated in positive or negative ion electrospray ionization mode.
Synthesis of H2L1: The ligand was synthesized according to a slightly
modified method described in the literature.[23] To a solution of 4,4Ј-
diaminodiphenylmethane (0.99 g, 5.00 mmol) in ethanol (50 mL) an
ethanol solution (10 mL) of 3-ethoxy-2-hydroxy-benzaldehyde (1.99 g,
12.00 mmol) was added. The mixture was heated to reflux for 5 h.
Figure 8. UV/Vis spectra (top) and Job plot (410 nm) (bottom) for
complexation of ligand H2L1 (orange) with copper acetate (blue) in
II
THF/methanol (v/v = 1:1). [H2L1] + [CuII] = 2.5ϫ10–5 m (xCu
=
0…1), t = 30 min.
The ESI-MS spectrum of a sample solution in THF/meth- After cooling, the orange precipitate was filtered off, washed with eth-
anol and diethyl ether and dried in air. Yield: 1.61 g, 65%. C31C30N2O4
(494.58 g·mol–1): C 75.08 (calcd. 75.28); H 6.01 (6.11); N 5.68
(5.66)%. M.p.: 160 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ = 13.80
(s, 2 H), 8.62 (s, 2 H), 7.22–7.26 (m, 8 H), 6.97–7.01 (m, 4 H), 6.85
anol with xCu = 0.5 shows the presence of a 2:2 (Cu:L) com-
plex species based on two peaks at m/z = 557.3 ([2HL+2Cu]2+)
and m/z = 1113.4 ([HL+L+2Cu]+). This result corresponds
with the 2:2 (Cu:L) composition of the crystalline complex and
emphasizes the high stability of the dinuclear complex both in
the solid state and in solution. Comparable data are obtained
also for H2L2 (Figure S6, Supporting Information).
3
3
(t, JH,H = 8.5 Hz, 2 H), 4.14 (q, JH,H = 6.9 Hz, 4 H), 4.02 (s, 2 H),
3
1.49 (t, JH,H = 7.1 Hz, 6 H). 13C NMR (500 MHz, CDCl3, 25 °C):
162.0 (2 CH), 151.7 (2 Cq), 147.7 (2 Cq), 146.3 (2 Cq), 139.9 (2 Cq,),
129.9 (4 CH), 123.7 (2 CH), 121.3 (4 CH), 119.2 (2 Cq), 118. 5 (2 CH),
116.1 (2 CH), 54.6 (2 CH2), 41.0 (CH2), 14.9 (2 CH3) ppm. UV/Vis:
λmax (lg ε): 322 nm (4.264). ESI-MS: m/z = 495.3 [M + H]+; 517.3
Preliminary liquid-liquid extraction experiments using the
extraction system Cu(NO3)2-NaNO3-HEPES buffer-H2O/li-
gand-CHCl3 with H2L1 (81%) and H2L2 (97%) demonstrate [M + Na]+; 492.9 [M – H]–.
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Synthesis of H2L2: To a solution of 3-ethoxy-2-hydroxy-benzaldehyde CCDC-1402162 [Cu2(L1)2] (Fax: +44-1223-336-033; E-Mail:
(1.83 g, 11.00 mmol) in ethanol (40 mL) an ethanol solution (20 mL) deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
of 4,4Ј-diaminodiphenyl sulfide (1.08 g, 5.00 mmol) was added. The
Supporting Information (see footnote on the first page of this article):
mixture was stirred at room temperature for 12 h. The orange precipi-
tate was filtered off, washed with ethanol and diethyl ether and dried
in air. Suitable single crystals were obtained by slow diffusion of di-
Crystallographic data and Figures and Tables of intramolecular interac-
tions in [{Cu2(L1)2}(H2O)2]·4H2O and [{Cu2(L2)2}(H2O)2]·2H2O;
plots of solution studies of complex formation of CuII with H2L1 and
H2L2 and liquid-liquid extraction data of CuII by H2L1 and H2L2.
ethyl ether into a solution of H2L2 in dichloromethane (10 mg, 1 mL).
Yield: 2.25 g, 88%. C30C28N2O4S (512.62 g·mol–1): C 70.67 (calcd.
70.29); H 5.69 (5.51); N 5.61 (5.26); S 5.97 (6.26)%. M.p.: 181 °C.
1H NMR (500 MHz, CDCl3, 25 °C): δ = 13.58 (s, 2 H), 8.63 (s, 2 H),
7.38–7.41 (m, 4 H), 7.23–7.25 (m, 4 H), 6.98–7.01 (m, 4 H), 6.86 (t,
Acknowledgements
3
3
3JH,H = 8.2 Hz, 2 H), 4.14 (q, JH,H = 6.9 Hz, 4 H), 1.49 (t, JH,H
=
The authors thank the Bundesministerium für Bildung und Forschung
(BMBF project 02NUK014A) and the German Federation of Industrial
Research Associations (AIF/ZIM project KF2807202RH3) for finan-
cial support.
7.1 Hz, 6 H). 13C NMR (500 MHz, CDCl3, 25 °C): 162.6 (2 CH),
151.6 (2 Cq), 147.7 (2 Cq), 147.2 (2 Cq), 134.3 (2 Cq), 132.1 (4 CH),
123.8 (2 CH), 122.1 (4 CH), 119.1 (2 Cq), 118.6 (2 CH), 116.3 (2 CH),
64.6 (2 CH2), 14.9 (2 CH3) ppm. UV/Vis: λmax (lg ε): 348 nm (4.515).
ESI-MS: m/z = 513.3 [M + H]+.
References
Synthesis of [{Cu2(L1)2}(H2O)2]·4H2O: A THF solution of H2L1
(20 mg, 0.04 mmol, 4 mL) was overlayered with a solution of cop-
per(II) acetate monohydrate (8 mg, 0.04 mmol) in methanol (4 mL).
Suitable single crystals were obtained by slow diffusion of di-
ethyl ether/hexane (v/v = 1:1) after one week. The brown-colored crys-
tals were filtered off, washed with ethanol and diethyl ether, and were
air-dried. Yield: 13 mg, 57%. C62H68Cu2N4O14 (1220.33 g·mol–1):
C 61.23 (calcd. 61.02); H 5.50 (5.62); N 4.39 (4.59)%. ESI-MS: m/z
= 557.3 [2HL+2Cu]2+, 1113.4 [HL+L+2Cu]+, 1111.1 [2 L+2Cu-H]–.
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sized using the same experimental procedure as above. Yield: 17 mg,
72%. C60H64Cu2N4O14S2 (1256.40 g·mol–1): C 57.36 (calcd. 57.36);
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X-ray Structure Determinations: Crystals employed for the X-ray
determination were obtained directly from the respective reaction solu-
tions and were used without further drying. Intensities were collected
with a Kappa Apex II CCD diffractometer (Bruker AXS) with ω and
ψ scans to approximately 26° (2Θmax) at 200(2) or 296(2) K using
graphite-monochromated Mo-Kα radiation generated from a sealed
tube (0.71073 Å). The Apex Suite[27] program package was used for
data collection, integration and data reduction. Multi-scan empirical
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was performed with SHELXL using the SHELXle user interface.[30,31]
In general, ordered non-hydrogen atoms with occupancies greater than
or equal to 0.5 were refined anisotropically; partial occupancy solvent
oxygen atoms were refined isotropically. Carbon-bound hydrogen
atoms were included in idealized positions and refined using a riding
model. Oxygen-bound hydrogen atoms that were structurally evident
in the difference Fourier map were included and refined with bond
length and angle restraints. Parameters for data collection and structure
refinement data for all structures are summarized in Table S10 (Sup-
porting Information). ORTEP[32] depictions of the three structures are
given in Figure 1, Figure 4 and Figure S2, selected bond lengths and
angles in Table 1 and Tables S1–S9.
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Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1402160 (H2L2), CCDC-1402161 [Cu2(L2)2], and
Z. Anorg. Allg. Chem. 2015, 2215–2221
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Zeitschrift für anorganische und allgemeine Chemie
[27] Apex Suite (V. 2014.4), Bruker AXS Inc., Madison, WI, USA, [30] SHELXL, G. M. Sheldrick, Program for the Refinement of Crystal
Structures, Göttingen, Germany, 2013.
[31] C. B. Hübschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crystallogr.
2011, 44, 1281–1284.
2014.
[28] SADABS, G. M. Sheldrick, Bruker AXS Area Detector Scaling
and Absorption Correction, Göttingen, Germany, 2008.
[29] SHELXS-97, G. M. Sheldrick, Program for the Solution of Crystal
Structures, Göttingen, Germany, 1997.
[32] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
Received: June 26, 2015
Published Online: September 7, 2015
Z. Anorg. Allg. Chem. 2015, 2215–2221
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© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim