Synthesis and structural characterisation of new bifunctional o-hydroxyacetophenones - Potential linker molecules for coordinative framework construction

Article abstract of DOI:10.5560/ZNB.2013-2332

Two new linker-type molecules 1a and 1b composed of o-hydroxyacetophenone coordinative groups attached to linear ethynylene or 1,4-phenylenediethynylene spacer units have been synthesized and structurally characterised. An X-ray crystallographic study for both compounds has shown structures with strong intramolecular hydrogen bonds fitting in the model of 'Intramolecular Resonance Assisted Hydrogen Bond (IRHAB)'. Initial coordination experiments with Cu(II) were performed and the resulting materials characterised by PXRD. The similarity of the copper coordination between these compounds and copper(II) acetylacetonate complexes was demonstrated by XPS measurements. Based on the evidence of these studies, and on elemental analysis, the formation of the corresponding coordination polymers comprising Cu(II) and the linkers has been proposed.

Full text of DOI:10.5560/ZNB.2013-2332

Synthesis and Structural Characterisation of New Bifunctional
o-Hydroxyacetophenones – Potential Linker Molecules for Coordinative
Framework Construction
Jo¨rg Hu¨bschera, Michael Gu¨nthelb, Robert Rosina, Wilhelm Seichtera, Florian Mertensb,
and Edwin Webera
a
Institut fu¨r Organische Chemie, TU Bergakademie Freiberg, Leipziger Str. 29, D-09596
Freiberg/Sachsen, Germany
Institut fu¨r Physikalische Chemie, TU Bergakademie Freiberg, Leipziger Str. 29, D-09596
b
Freiberg/Sachsen, Germany
Reprint requests to Prof. Edwin Weber. Fax: +49 3731-39-3170.
E-mail: edwin.weber@chemie.tu-freiberg.de
Z. Naturforsch. 2013, 68b, 214 – 222 / DOI: 10.5560/ZNB.2013-2332
Received December 19, 2012
Two new linker-type molecules 1a and 1b composed of o-hydroxyacetophenone coordinative
groups attached to linear ethynylene or 1,4-phenylenediethynylene spacer units have been synthe-
sised and structurally characterised. An X-ray crystallographic study for both compounds has shown
structures with strong intramolecular hydrogen bonds fitting in the model of ‘Intramolecular Reso-
nance Assisted Hydrogen Bond (IRHAB)’. Initial coordination experiments with Cu(II) were per-
formed and the resulting materials characterised by PXRD. The similarity of the copper coordination
between these compounds and copper(II) acetylacetonate complexes was demonstrated by XPS mea-
surements. Based on the evidence of these studies, and on elemental analysis, the formation of the
corresponding coordination polymers comprising Cu(II) and the linkers has been proposed.
Key words: o-Hydroxyacetophenone, Synthesis, Crystal Structure, X-Ray Photoemission, X-Ray
Diffraction
Introduction
not or only marginally been applied as coordina-
tive groups of linker molecules. This is the case for
Coordination polymers have been established as an the bidentate ligand o-hydroxyacetophenone and its
important class of compounds with promising appli- derivatives which are well known for their efficiency
cations in the fields of catalysis [1 – 3], sensors [4, in the complexation of transition metal ions, espe-
5] and gas sorption [6 – 8]. Due to their modular cially of Cu(II) [17 – 19]. Remarkably, there is only
development, relevant properties such as framework one early note in the literature dealing with physico-
topology and pore size are flexibly adjustable by the chemical properties of Cr(III), Co(II) and Ni(II)
choice of eligible metal ions and the specific de- polychelates of a related linker-type molecule fea-
sign of the organic linker molecules, which com- turing a 4,40-(4,40-biphenylylenebisazo)di(2-hydroxy-
bine several coordination active functions. Outstand- acetophenone) structure [20]. But, apart from that,
ing efficiency in the complexation of metal ions show no further investigations about the applicability of
linker molecules comprising chelate functions. Numer- o-hydroxyacetophenone-containing linker molecules
ous coordination polymers containing organic compo- have been reported. In addition, tecton-type molecules
nents with chelate active functions such as carboxy- having salicylic aldehyde terminal functionalities in-
late [9, 10], phosphate [11] and dithiocarbamate [12], stead of o-hydroxyacetophenone moieties attached
but also more complex structures including bisimida- to a linear segment, thus bearing structural resem-
zoles [13, 14], bispyrimidines [15] and dioximes [16] blance to a potential linker molecule, proved to be
have been reported. Nevertheless, there are still open very useful in the formation of ordered surface nano-
opportunities for usage of chelate units that have structures [21 – 25], but without being applied in the
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
215
starting from 4-bromophenol and trimethylsilylacety-
lene (TMSA) or 2-methylbut-3-yn-2-ol (MEBYNOL)
as the base materials. As shown in Scheme 2, in the
first step 4-bromophenol was acetylated with acetic
anhydride to give 5 and then subjected to a Fries re-
action [26] yielding 5-bromo-2-hydroxyacetophenone
(4), which was one of the components for the fol-
lowing cross-coupling reaction. This reaction was car-
ried out with TMSA (method A) or MEBYNOL
(method B) using the Sonogashira-Hagihara coupling
conditions [27] to produce 3a and 3b, respectively,
which were subsequently deblocked ending up with
5-ethynyl-2-hydroxyacetophenone (2) as the key inter-
Scheme 1. Formula structures of the compounds studied.
construction of coordination polymers. These basic mediate. Further cross-coupling of 2 with the bromide
principles gave the motivation to focus our attention 4 or 1,4-diiodobenzene yielded the target linker com-
on related linker molecules with terminal chelating ponents 1a and 1b, respectively.
o-hydroxyacetophenone groups such as 1a and 1b
(Scheme 1).
Crystal structures of 1a and 1b
In the present paper, we describe the synthesis of
these compounds and discuss their crystal structures.
Crystal and refinement data for the studied com-
We also show preliminary results obtained from PXRD pounds are summarised in Table 1, while geometrical
and XPS investigations including elemental analysis parameters for intermolecular contacts are listed in Ta-
for the corresponding complexes of 1a and 1b with ble 2. Perspective views of the molecular structures in-
Cu(II) which are suggestive of the formation of coor- cluding the numbering of atoms are shown in Fig. 1.
dination polymers.
Packing diagrams of 1a and 1b are presented in Figs. 2
and 3, respectively.
The presence of a strong intramolecular hydro-
gen bond formed between the phenolic hydrogen
atoms and the oxygen atoms of the acetyl group, be-
ing a characteristic feature of 2-hydroxyacetophen-
Results and Discussion
Synthesis of 1a and 1b
ones [28 – 30], is also shown in the crystal structures
˚
The title compounds 1a and 1b (Scheme 1) have of 1a and 1b [O1···O2 2.515(2) and 2.564(1) A, O1–
been synthesised using a multi-step reaction sequence H1···O2 146 and 145◦ for 1a and 1b, respectively].
Scheme 2. Synthetic pathway for the preparation of the linker molecules.
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
Fig. 1. Perspective views of 1a (a) and
1b (b) including the numbering of atoms.
Displacement ellipsoids are at the 50%
probability level. Hydrogen bonds are
presented as dotted lines.
Table 1. Crystal data and numbers perti-
nent to data collection and structure refine-
ment of the compounds studied.
Compound
1a
1b
C26H18O4
394.40
monoclinic
C2/c
Empirical formula
Formula weight, g mol−1
Crystal system
C18H14O4
294.29
orthorhombic
Pbca
Space group
˚
a, A
7.0835(3)
12.5830(5)
16.3032(6)
90.00
1453.13(10)
4
38.1541(10)
5.5751(2)
9.0955(3)
94.9530(10)
1927.51(11)
4
˚
b, A
˚
c, A
β, deg
3
˚
V, A
Z
F(000), e
616
1.35
0.1
824
1.36
0.1
D
calcd,g cm−3
µ(MoKα ), mm−1
Data collection
Temperature, K
100(2)
153(2)
θrange, deg
2.5 – 28.1
1.1 – 28.9
Index ranges h, k, l
−9/9, −16/16, −21/20
12 030 / 1776 / 0.0344
1324
−51/51, −7/7, −12/12
12 485 / 2539 / 0.0224
2097
Refls. measd / unique / Rint
Refls. observed [I > 2σ(I)]
No. of refined parameters
R1 /wR2 (all data)a,b
Weighting scheme A / Bb
S (Goodness of fit on−F3 2)c
102
138
0.0653 / 0.1296
0.0639 / 0.630
1.038
0.30 / −0.24
0.0506 / 0.1259
0.0895 / 0.8722
1.068
0.37 / −0.18
˚
Final ∆ρmax/min, e A
a
b
R1 = Σ||Fo| − |F ||/Σ|Fo|; wR2 = [Σw(Fo2 − F2)2/Σw(Fo2)2]1/2, w = [σ2(Fo2) +
c
c
(AP)2 + BP]−1, where P = (Max(Fo2,0) + 2F2)/3;
S = [Σw(Fo2 − F2)2/(nobs
−
c
c
c
nparam)]1/2
.
The molecular structure element H–O–C=C–C=O of C(5)–C(6) of the aromatic ring in 1a and 1b [1.369(2),
˚
1a and 1b (Fig. 1) correlates with the concept of the 1.375(2) A] may be ascribed to a similar phenomenon.
so-called ‘Intramolecular Resonance Assisted Hydro- The tolane derivative 1a crystallises in the or-
gen Bond (IRAHB) formation’ [31], which suggests thorhombic space group Pbca with the asymmetric
a synergistic mutual reinforcement of intramolecular part of the unit cell containing one half of the molecule,
hydrogen bonding due to π-electron delocalisation, but e. g. the molecule adopts inversion symmetry (Fig. 1a).
its significance has lately been disputed [32].
The approximately planar geometry of the molecule
Irrespective of this point being at issue, an increase indicates perfect delocalisation of the π-electron sys-
˚
of the bond lengths C(1)–C(2) [1.412(2), 1.410(2) A] tem. Contrary to expectations, the crystal structure
˚
and C(7)–O(2) [1.236(2), 1.234(1) A] corresponds to lacks arene stacking. Instead, the C=O units of the
˚
˚
a decrease in the C(2)–C(7) bond length [1.477(2) A] acetyl groups are sandwiched at a distance of ca. 3.2 A
for 1a and 1b, respectively, indicating a potential reso- between the aromatic rings of adjacent molecules,
nance effect since these bond lengths deviate signif- which suggests the presence of π(C=O) · · · π(arene)
icantly from those found in the crystal structure of interactions [34]. The molecules are associated by
acetophenone [33]. Also, the shortening of the bond a close network of C–H···O hydrogen bonds [35]
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
217
Fig. 2. Packing diagram of 1a viewed
down the crystallographic c axis. Hydro-
gen bonds are marked as broken lines.
Fig. 3. Packing diagram of 1b viewed
down the crystallographic c axis (perspec-
tive view).
Table 2. Geometric parameters for inter-
molecular contacts in compounds 1a and
1b.
˚
Interaction
Symmetry code
Distances, A
Angle, deg
D–H···A
D–H
D···A
H···A
1a
O1–H1···O2
C5–H5···O2
C8–H(8C)···O1
C7–O2···cg(A)a
C7–O2···cg(A)a
1b
x, y, z
0.84
0.95
0.98
2.515(2)
3.248(2)
3.393(2)
1.77
2.30
2.53
146
176
148
x, 1.5−y, −0.5+z
0.5−x, 0.5+y, z
−0.5+x, y, 0.5−z
0.5+x, y, 0.5−z
1.236(2) 3.634(2) 3.826(1) 71.8(1)
1.236(2) 3.700(2) 3.336(1) 97.2(1)
O1–H1···O2
C8–H(8A)···O2
C5–H(5)···C(13)b
x, y, z
0.84
0.98
0.95
2.564(1)
3.394(1)
3.394(1)
1.83
2.61
2.61
145
137
137
0.5−x, 1.5−y, 1−z
−x, 1+y, 1.5−z
a Cg means the centre of the aromatic ring. Ring A: C(1). . . C(6); b to achieve a reasonable
hydrogen bond geometry, an individual atom instead of the ring centre was chosen as an
acceptor site.
◦
[C(5)–H(5)···O(2) 2.30 A, 176 , C(8)–H(8C)···O(1) coplanar but twisted by an angle of 14.9(2)◦ with re-
˚
◦
˚
2.53 A, 148 ] (Fig. 2).
spect to the central arene ring. The ethynyl parts are
Recrystallisation of 1b from ethyl acetate yielded slightly bent so that the molecule adopts an S-shaped
colourless plates of the monoclinic space group C2/c distortion along its main axis.
with one half of the molecule in the asymmetric part
A view of the crystal structure down the b axis
of the unit cell (Fig. 1b). According to inversion sym- (Fig. 3) reveals stacking-like packing of molecules
metry, the terminal aromatic rings of the molecule are with a lateral displacement of consecutive molecules,
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
indicating that the crystal structure lacks π···π arene
interactions. Molecular association is restricted to only
˚
one weak hydrogen bond [C(8)–H(8A)···O(2) 2.61 A,
137◦] and C–H···π(arene) interactions [36]. The incli-
nation between molecules of adjacent stacks indicates
that the crystal structure of 1b is stabilised by van der
Waals forces and close packing of molecules rather
than by directed non-covalent bonding.
Preparation and structural characterisation of
coordination polymers
Fig. 4. PXRD data of the plain linker molecule 1a (a),
the metal-organic compound Cu(1a) (b) and the precursor
[Cu(NH3)4]SO4 (c).
Considering the known efficiency of o-hydroxy-
acetophenone to complex the Cu(II) ion [17 – 19], the
linker-type molecules 1a and 1b were tested regarding
the formation of corresponding coordination polymers.
For this to do, Pfeiffer’s method [37] was used with
[Cu(NH3)4]SO4 acting as a precursor. This tetrammine
complex was synthesised by treatment of an aqueous
solution of CuSO4 with aqueous ammonia. The fol-
lowing polymerisation was realised by a solvothermal
synthesis between the copper complex and the linkers
1a and 1b at 100 ◦C to yield Cu(1a) and Cu(1b). Ele-
mentary analyses of both materials indicate a 1 : 1 ratio
between linker molecule and copper(II) ion.
Fig. 5. PXRD data of the plain linker molecule 1b (a),
the metal-organic compound Cu(1b) (b) and the precursor
[Cu(NH3)4]SO4 (c).
Crystals suitable for X-ray diffraction analysis, giv-
ing structural information on the nature of the coor-
dination polymers, could not be obtained. Therefore indicate the presence of two solid phases. In contrast,
a number of other characterisation methods were ap- the reflections for Cu(1b) are sharp and furthermore
plied to provide some structural information as demon- shifted to smaller angles compared to 1b. As expected,
strated in the following.
this shift is a sign of an expanded unit cell. After the
coordination polymers have been formed, reflections
of the reactants are not observed anymore.
PXRD analysis
By using powder X-ray diffraction (PXRD) it is pos- X-Ray photoemission
sible to trace the progress of the chemical reaction via
comparing the diffraction data of Cu(1a) or Cu(1b)
To furnish proof of the presence of copper within
with the one of the reactants. Figures 4 and 5 show the the compounds and to analyse the coordination sphere
PXRD data of each compound in the reaction batch of the metal centres we used XPS (X-ray photoelec-
of the copper precursor with 1a and 1b, respectively. tron spectroscopy) as the characterisation method of
In each case, the PXRD data of the reactants are dis- choice. According to the literature, a specific signal
played next to the one of the synthesised metal-organic for the binding energy of 2p core level electrons of
compound.
copper (spin 3/2) should appear in the spectrum at
The differences between the PXRD of the reactants 932.7 eV (934.5 eV for CuO) [38 – 40]. For the com-
and the coordination polymers Cu(1a) and Cu(1b) can pounds Cu(1a) and Cu(1b) prepared as thin films, the
be traced back to a change in crystal structure, and respective values of 934.3 and 934.9 eV were measured
a loss of reflections marks the completed conversion (Fig. 6). In copper compounds with acetylacetonate-
of the starting materials. In the case of Cu(1a), both like ligands, a spin-orbital splitting occurs for the Cu
broad and sharp reflections are recorded which seem to 2p core level electrons. This effect can be used to gain
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
219
tion by single-crystal X-ray analysis shows strong in-
tramolecular hydrogen bonding between OH and car-
bonyl groups of the two compounds typical for the
o-hydroxyacetophenone moiety. Bond lengths within
the H–O–C=C–C=O structural fragment suggest the
applicability of the IRAHB concept. The packing of
the molecules of both compounds in the crystal in-
volve networks of C–H···O and C–H···π interactions
while remarkably lacking π···π arene stacking con-
tacts. Solvothermal syntheses were carried out with
1a or 1b and copper(II) ions leading to the corre-
sponding coordination polymers Cu(1a) and Cu(1b).
Because X-ray single-crystal structural analyses could
not be conducted, basic information needed to be de-
rived from elemental analysis, PXRD and XPS mea-
surements. Owing to the nature of the used precursor
molecules and the results obtained from the XPS and
elemental analysis, a square-planar coordination ge-
ometry for the copper(II) centres can be postulated.
Assuming this kind of coordination geometry
also found in analogous Cu(II) acetylacetonate com-
plexes [41], the present coordination polymers are
bound to possess a completely planar one-dimensional
coordination assembly. Since the copper(II) ions
therein still have two coordinative vacancies, the
formed chains could become interesting building
blocks in the design of higher-dimensional coordina-
Fig. 6. Photoemission spectra of the compounds Cu(1a) and
Cu(1b) (prepared as thin layers) in the range of the emitted
radiation of the 2p3/2 core level electrons. The fitted Gauss-
Lorentzian functions can be used for quantitative analysis.
Table 3. Measured XPS data of Cu(1a) and Cu(1b) in the
Cu 2p region. Listed are the binding energies of the 2p3/2
electrons in eV. In parentheses are the FWHM values. (The
signals are listed by increasing binding energies according to
Fig. 6).
Signal
Cu(1a)
Cu(1b)
1
2
3
934.3 (3.415)
939.0 (3.045)
943.6 (4.463)
934.9 (2.018)
939.7 (3.255)
944.7 (3.591)
information on the state of coordination in the com- tion polymers, which may be achieved by adding spe-
pound. Like it is found for the binding energies of cop- cific oligodentate molecules. Other metal ions may
per(II) acetylacetonate, there are three signals shown also be used. The molecules 1a and 1b may also be
in Fig. 6. This signal pattern can be explained by using suitable tectons for the construction of porous mate-
a cluster model which assumes strong hybridisation ef- rials (HBNs) [42]. These networks are interesting ob-
fects for Cu 3d and C 2p electrons as well as O 2px jects for the stimulation of future research.
and C 2px electrons [41]. The split orbital energies are
correlated to 2p53d10L1-hybridised states, and bond-
Experimental Section
ing and anti-bonding states of 2p53d10L2 and 2p53d9,
where L is the corresponding ligand. The correspond- General
ing electron binding energies are listed in Table 3.
Melting points: Kofler melting point microscope (uncor-
A quantitative comparison between the two satellites
rected). IR: Nicolet FT-IR 510. 1H and 13C NMR (inter-
and the main signals leads to a ratio of approximately
nal standard TMS, δ in ppm): Bruker AVANCE DPX 500.
1 : 1 : 2 for both compounds.
MS (ESI): QUATTRO-LC (positive ion) and ESQUIRE-
LC (solvent: chloroform). Elemental analysis: Heraeus
CHN rapid analyser. Column chromatography: silica gel 60
Conclusions
(0.040 – 0.063 mm, Merck). TLC-analysis: aluminium sheets
precoated with silica gel 60 F254 (Merck).
Using a Pd-catalysed coupling process in the key re-
action step, the new linker molecules 1a and 1b fea-
turing terminating o-hydroxyacetophenone groups at-
tached to rigid linear ethynylene and arene building
Reagents and materials were obtained from commercial
suppliers (Fisher Scientific, ABCR, Aldrich) and were used
without further purification. The solvents were purified using
units have been synthesised. Structural characterisa- standard procedures. Solvents for the Sonogashira-Hagihara
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J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
coupling reactions were deoxygenated prior to use by ultra- δ = 26.6, 31.4, 65.4, 80.7, 92.8, 113.5, 118.6, 119.3, 134.1,
sound (20 min) while bubbling argon through the solution.
139.2, 162.0, 204.1. – MS (GC-MS): m/z = 218 (calcd.
218.09 for C13H14O3, [M]+). – C13H14O3: calcd. C 71.54,
H 6.47; found C 71.40, H 6.67.
Preparation of 4-bromophenyl acetate (5) and
5-bromo-2-hydroxyacetophenone (4)
Preparation of 5-Ethynyl-2-hydroxyacetophenone (2)
Both compounds were synthesised according to the lit-
erature [26]. 4-Bromophenyl acetate (5) was isolated as
a colourless oil (97%) and 5-bromo-2-hydroxyacetophenone
(4) as a pale-yellow solid (75%, m. p. 58 ◦C).
Method A. To a solution of 5-(trimethylsilylethynyl)-
2-hydroxyacetophenone (3a) (2.3 g, 9.9 mmol) in THF
(20 mL), KOH (0.56 g, 10 mmol) dissolved in methanol
(20 mL) was added. After having been stirred for 24 h at
room temperature, the solution was diluted with diethyl
ether and washed with diluted hydrochloric acid and wa-
ter. The organic layer was dried and the solvent removed
in vacuo to yield 1.5 g (95%) of a yellow solid which
was crystallised from n-hexane-CH2Cl2 (3 : 1). – M. p.
Synthesis of o-hydroxyacetophenones 3a and 3b (General
procedure)
The respective aryl bromide and the corresponding ter-
minal alkyne were dissolved in degassed diisopropylamine.
To this solution, the catalyst, being composed of triphenyl-
phosphane (2 mol-%), copper(I) iodide (3 mol-%) and
trans-dichlorobis(triphenylphosphane)palladium(II) (2 mol-
%), was added, and the mixture was stirred under reflux un-
til completion of the reaction (TLC analysis). Evaporation
of the solvent followed by column chromatography and/or
crystallisation yielded the pure compounds. Specifications
for each compound are given below.
110 ◦C. – IR (KBr): νmax = 1641, 2107, 2931, 3265 cm−1
.
–
1H NMR (500 MHz, CDCl3): δ = 2.63 (3 H, s, CH3),
3.03 (1 H, s, CH), 6.93 (1 H, d, 3J = 8.65 Hz, Ar-H),
7.56 (1 H, dd, 3J = 8.65 Hz, 4J = 2.05 Hz, Ar-H), 7.88 (1
H, d, 4J = 2.05 Hz, Ar-H), 12.38 (1 H, s, OH). – 13C
NMR (125 MHz, CDCl3): δ = 26.6, 76.3, 82.4, 112.7, 118.8,
119.4, 134.8, 139.6, 162.6, 204.0. – MS (GC): m/z = 160
(calcd. 160.05 for C10H8O2, [M]+). – C10H8O2: calcd. C
74.99, H 5.03; found C 74.48, H 5.34.
5-(Trimethylsilylethynyl)-2-hydroxyacetophenone (3a)
Method B. 5-(3-Hydroxy-3-methylbutyn-1-yl)-2-hydro-
xyacetophenone (3b) (5.0 g, 22.9 mmol) was dissolved in
toluene (50 mL), and KOH (3.85 g, 68.8 mmol) was added.
The solution was refluxed for 3 h, acidified with conc.
hydrochloric acid (100 mL) and filtered. The filtrate was
extracted with methylene chloride (250 mL), the combined
organic layers dried over anhydrous Na2SO4 and evaporated
to dryness. The resulting residue was purified by column
chromatography (SiO2; n-hexane-CH2Cl2, 6 : 1) to yield
1.7 g (47%) of a yellow solid corresponding to the data
given above.
5-Bromo-2-hydroxyacetophenone (4) (5.0 g, 23.4 mmol),
trimethylsilylacetylene (2.4 g, 24.3 mmol) and the catalyst
in diisopropylamine (150 mL) were reacted for 4 h under
the coupling conditions. Purification by column chromatog-
raphy (SiO2; n-hexane-ethyl acetate, 3 : 1) yielded 2.3 g
(43%) of a yellow solid. – M. p. 158 ◦C. – IR (KBr):
ν
max = 1638, 2113, 2930, 3263 cm−1. – 1H NMR (500 MHz,
CDCl3): δ = 0.26 (9 H, s, CH3), 2.66 (3 H, s, CH3), 6.98
(1 H, d, 3J = 8.65 Hz, Ar-H), 7.61 (1 H, d, 3J = 8.65 Hz,
Ar-H), 7.92 (1 H, s, Ar-H), 12.39 (1 H, s, Ar-H). – 13C
NMR (125 MHz, CDCl3): δ = 0.1, 26.6, 70.5, 87.1, 113.8,
118.9, 119.6, 134.0, 139.1, 162.3, 204.1. – MS (GC-MS):
m/z = 232 (calcd. 232.09 for C13H16O2Si, [M]+).
Synthesis of 1a and 1b
The general procedure for the synthesis of 3a and 3b ap-
plies.
5-(3-Hydroxy-3-methylbut-1-ynyl)-2-hydroxyacetophenone
(3b)
5,50-(Ethyne-1,2-diyl)bis(2-hydroxyacetophenone) (1a)
5-Bromo-2-hydroxyacetophenone (4) (5.0 g, 23.4
mmol), 2-methylbut-2-yn-2-ol (2.0 g, 24.3 mmol) and the
5-Ethynyl-2-hydroxyacetophenone (2) (3.0 g, 18.8
catalyst in diisopropylamine (150 mL) were reacted for mmol), 5-bromo-2-hydroxyacetophenone (4) (3.85 g,
4 h under the coupling conditions. Purification by column 18 mmol) and the catalyst were reacted in diisopropylamine
chromatography (SiO2; n-hexane-ethyl acetate, 8 : 1) yielded (100 mL) under the coupling conditions. Purification by
3.9 g (77%) of an orange solid which was crystallised from column chromatography (SiO2; n-hexane-ethyl acetate, 8 : 1)
cyclohexane. – M. p. 55 ◦C. – IR (KBr): νmax = 1651, 2224, yielded 2.2 g (40%) of a yellow solid which was crystallised
2984, 3307 cm−1. – 1H NMR (500 MHz, CDCl3): δ = 1.63 from n-hexane. – M. p. 205 ◦C. – IR (KBr): νmax = 1641,
(6 H, s, CH3), 2.58 (1 H, s, OH), 2.63 (3 H, s, CH3), 6.91 1948, 2920 cm−1. – 1H NMR (500 MHz, CDCl3): δ = 2.67
(1 H, d, 3J = 8.60 Hz, Ar-H), 7.48 (1 H, dd, 3J = 8.60 Hz, (6 H, s, CH3), 6.97 (2 H, d, 3J = 8.65 Hz, Ar-H), 7.61
4J = 2.05 Hz, Ar-H), 7.80 (1 H, d, 4J = 2.05 Hz, Ar-H), (2 H, dd, 3J = 8.65 Hz, 4J = 2.00 Hz, Ar-H), 7.92 (2 H,
12.35 (1 H, s, OH). – 13C NMR (125 MHz, CDCl3): d, 4J = 2.00 Hz, Ar-H), 12.39 (2 H, s, OH). – 13C NMR
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221
(125 MHz, CDCl3): δ = 26.7, 87.1, 113.8, 118.9, 119.6, X-Ray structure determination
134.0, 139.1, 162.3, 204.0. – MS (GC-MS): m/z = 295
(calcd. 294.09 for C18H14O4, [M]+). – C18H14O4: calcd. C
73.46, H 4.80; found C 73.37, H 4.99.
Suitable single crystals were obtained by slow cooling of
solutions of 1a and 1b in n-hexane and ethyl acetate, respec-
tively. Information concerning the crystallographic data and
the structure refinement is summarised in Table 1. The in-
tensity data were collected on a Bruker APEX II diffrac-
5,50-[Benzene-1,4-diyl-di(ethyne-2,1-diyl)]bis(2-hydroxy-
acetophenone) (1b)
˚
tometer with MoKα radiation (λ = 0.71073 A) using ω- and
φ-scans. Intensities were corrected for background, Lorentz
and polarisation effects. Preliminary structure models were
derived by an application of Direct Methods [43, 44] and
were refined by full-matrix least-squares calculations based
on F2 for all reflections [45, 46]. All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were in-
cluded in the models in calculated positions and were refined
as constrained to bonding atoms.
CCDC 859743 and 859744 contain the supplementary
crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Data Centre via
www.ccdc.cam.ac.uk/data request/cif.
5-Ethynyl-2-hydroxyacetophenone (2) (2.0 g, 12 mmol),
1,4-diiodobenzene (1.9 g, 5.8 mmol) and the catalyst were
reacted in diisopropylamine (50 mL) under the coupling con-
ditions. The residue was treated with refluxing diluted hy-
drochloric acid, filtered and crystallised from chloroform to
yield 0.8 g (34%) of a colourless solid which was crystallised
from ethyl acetate. – M. p. 253 ◦C. – IR (KBr): νmax = 1644,
2214, 3031 cm−1. – 1H NMR (500 MHz, [D6]DMSO):
δ = 2.67 (6 H, s, CH3), 6.97 (2 H, d, 3J = 8.60 Hz, Ar-
H), 7.54 (4 H, s, Ar-H), 7.64 (2 H, dd, 3J = 8.60 Hz,
4J = 2.10 Hz, Ar-H), 8.03 (2 H, d, 4J = 2.10 Hz, Ar-H),
12.09 (2 H, s, OH). – 13C NMR (125 MHz, [D6]DMSO):
δ = 27.8, 87.7, 90.5, 112.8, 118.3, 120.8, 122.4, 131.3,
134.5, 138.4, 160.9, 203.4. – MS ((–)-ESI): m/z = 393
Powder X-ray diffraction analysis
2
(calcd. 394.12 for C26H18O4, [M–H]−). – C26H18O4· /3
Compounds Cu(1a) and Cu(1b) were desolvated with
dichloromethane and dried under vacuum. Both powders
were pestled to get a homogeneous composition. The inten-
sity data were collected on a PANalytical PW3040/60 X’Pert
H2O: calcd. C 76.83, H 4.79; found C 76.53, H 4.58.
General procedure for the synthesis of coordination
polymers
˚
Pro diffractometer with CuKα radiation (λ = 1.5418 A). The
measurements were carried out in reflexion mode, and wide-
angle values were recorded from 5 to 70◦ with a step size of
0.01◦.
To a solution of CuSO4·5H2O in water, an aqueous solu-
tion of ammonia was added until the initially formed light-
blue precipitate dissolved giving a dark-blue solution of
[Cu(NH3)4]SO4. The organic compound dissolved in ace-
tonitrile was then added dropwise, and the solution was
stirred for 30 min at 100 ◦C. The resulting flocculent pre-
cipitate was separated by filtration, then washed with water
and acetonitrile. Finally the precipitate was desolvated with
dichloromethane.
X-Ray photoelectron spectroscopy
Samples of the compounds Cu(1a) and Cu(1b) were pre-
pared as thin films on a silicon wafer to obtain planar sur-
faces. AlKα radiation was used as photo electron excita-
tion source during the measurement. Electric charging ef-
fects were compensated with the help of a flood gun, and any
residual charging effect which leads to a shift of the spectra
was corrected mathematically. The main value in the C 1s re-
gion was adjusted to that of aromatic carbon signals with the
binding energy value of 284.8 eV. The analysis was carried
out with the software CasaXPS from Casa Software Ltd.
Preparation of Cu(1a)
20.5 mg (0.082 mmol) of CuSO4·5H2O and 25 mg
(0.085 mmol) of 1a were reacted as given above to yield
22.9 mg of a green solid. – C18H12CuO4: calcd. C 60.76,
H 3.40; found C 61.29, H 3.87.
Acknowledgement
Preparation of Cu(1b)
This work was performed within the Cluster of Excellence
‘Structure Design of Novel High-Performance Materials via
8.1 mg (0.032 mmol) of CuSO4·5H2O and 16.5 mg Atomic Design and Defect Engineering (ADDE)’, which is
(0.042 mmol) of 1b were reacted as given above to yield financially supported by the European Union (European Re-
5.4 mg of a light-green solid. – C26H16CuO4: calcd. C 68.49, gional Development Fund) and by the Ministry of Science
H 3.54; found C 68.37, H 3.71.
and Art of Saxony (SMWK).
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222
J. Hu¨bscher et al. · Bifunctional o-Hydroxyacetophenones
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