Dioxygen Activation by an in situ Reduced CuII Hydrazone Complex

Article abstract of DOI:10.1002/ejic.201500556

A Cu^II hydrazone complex has been synthesized that can be reduced in situ in boiling methanol to give the corresponding Cu^I complex. The latter complex readily activates dioxygen under ambient conditions, as was unambiguously shown by isotopic labeling studies. As a consequence of the dioxygen activation, the thienyl moiety appended to the hydrazone ligand is easily oxidized in β position (C-H→C-O), finally leading to a change in the coordination environment of the central metal ion. All relevant complexes have been structurally characterized by single-crystal X-ray diffraction analyses. The hydrazone ligand applied in this study does not mimic a biologically relevant coordination motif in copper-containing oxygenases. Nonetheless, the reactivity of the Cu^I complex resembles that found in many oxygenases, indicating that hydrazone ligands may be well-suited for the generation of novel bioinspired oxidation catalysts. A Cu^II complex of a hydrazone ligand with N,N,S-donor functionality is reported that, after in situ reduction, is able to activate dioxygen, leading to a hydroxylation of the ligand and finally resulting in the formation of a Cu^II complex of a hydrazone ligand acting as an N,N,O-donor.

Full text of DOI:10.1002/ejic.201500556

FULL PAPER
DOI:10.1002/ejic.201500556
II
Dioxygen Activation by an in situ Reduced Cu
Hydrazone Complex
[
a]
[a]
[b]
Christian Radunsky, Jutta Kösters, Matthias C. Letzel,
[c]
[a]
[d]
Sivathmeehan Yogendra, Christian Schwickert, Sinja Manck,
[d]
[a]
[c]
Biprajit Sarkar, Rainer Pöttgen, Jan J. Weigand,
Johannes Neugebauer,[ and Jens Müller*
b,e]
[a]
Dedicated to F. Ekkehardt Hahn on the occasion of his 60th birthday
Keywords: Bioinorganic chemistry / Oxygen activation / Copper complexes / Hydrazones
A CuII hydrazone complex has been synthesized that can be
reduced in situ in boiling methanol to give the corresponding
Cu complex. The latter complex readily activates dioxygen
central metal ion. All relevant complexes have been structur-
ally characterized by single-crystal X-ray diffraction analy-
ses. The hydrazone ligand applied in this study does not
I
under ambient conditions, as was unambiguously shown by mimic a biologically relevant coordination motif in copper-
I
isotopic labeling studies. As a consequence of the dioxygen
activation, the thienyl moiety appended to the hydrazone li-
gand is easily oxidized in β position (C–HǞC–O), finally
leading to a change in the coordination environment of the
containing oxygenases. Nonetheless, the reactivity of the Cu
complex resembles that found in many oxygenases, indicat-
ing that hydrazone ligands may be well-suited for the gener-
ation of novel bioinspired oxidation catalysts.
Introduction
from this ligand and CuCl ·2H O is able to activate di-
2 2
oxygen during recrystallization from methanol, resulting in
the hydroxylation of the thienyl moiety in β position. In
general, copper complexes are well-known for their di-
oxygen activation capability, both biologically relevant and
Copper complexes with hydrazone-containing ligands
are well-established bioactive compounds. In addition to
showing possible anticancer and antitubercular activity,
[
1]
[2]
they are known nucleic acids intercalators and may func-
tion as artificial nucleases.[ We recently devised a family
of tridentate hydrazone-based ligands with N,N,N-, N,N,O-
or N,N,S-donor capability for various applications, e.g. as
[6]
biomimetically. Numerous enzymes with copper active
3]
sites are known, including galactose oxidase (with a mono-
nuclear copper site), dopamine β monooxygenase (compris-
ing an uncoupled dinuclear copper center), and tyrosinase
chromogenic sensors[ or in metal-mediated base pairs.
4]
[5]
[7]
(with a coupled dinuclear copper site), to name just a few.
In this context, we developed the hydrazone-based thienyl-
containing ligand 2 comprising a potential N,N,S-donor en-
vironment (Scheme 1). Interestingly, the complex derived
The activation process typically proceeds via reduction of
the dioxygen molecule by either one or two Cu center(s),
I
II
[8]
resulting in the formation of Cu and either superoxide or
[
9]
peroxide. Even the formation of a bis-μ-oxo dicopper(III)
[
10]
[
a] Institut für Anorganische und Analytische Chemie,
Westfälische Wilhelms-Universität Münster,
Corrensstraße 28/30, 48149 Münster, Germany
E-mail: mueller.j@uni-muenster.de
complex is possible.
We report here our investigation of
the apparent dioxygen activation by a mononuclear Cu
complex.
II
http://www.muellerlab.org/
[
[
b] Organisch-Chemisches Institut, Westfälische Wilhelms-
Universität Münster,
Corrensstraße 40, 48149 Münster, Germany
c] Fachrichtung Chemie und Lebensmittelchemie, Technische
Universität Dresden,
01062 Dresden, Germany
[
[
d] Institut für Chemie und Biochemie, Freie Universität Berlin,
Fabeckstraße 34/36, 14195 Berlin, Germany
e] Center for Multiscale Theory and Computation, Westfälische
Wilhelms-Universität Münster,
Corrensstraße 40, 48149 Münster, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201500556.
Scheme 1. Synthesis of the N,N,S-donor ligand 2. Conditions: a)
16 h, 135 °C, 76%; b) EtOH, cat. AcOH, 50 min, 60 °C, 80%.
Eur. J. Inorg. Chem. 2015, 4006–4012
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Results and Discussion
in agreement with the above-mentioned DFT calculations
in the gas phase. In this case, the Cu ion adopts a distorted
tetrahedral coordination geometry. However, taking into
II
The N,N,S-donor ligand 2 was synthesized following a
[
5]
two-step procedure reported previously (Scheme 1). Start-
ing from 2-chloropyridine and methylhydrazine, a substitu-
tion reaction led to the formation of 2-(1-methylhydrazin-
yl)pyridine 1. In the following, ligand 2 was formed by an
acid-catalyzed condensation reaction of the hydrazine de-
rivative 1 and 2-thiophenecarbaldehyde.
consideration the effective atomic radii of 2.93 Å (Cu) and
[13]
2.50 Å (S),
these two atoms are engaged in a weakly
bonding interaction. This interaction would explain the pre-
II
ferred orientation of the thienyl moiety towards the Cu
ion. Accordingly, the coordination environment of Cu
II
may also be described as distorted trigonal bipyramidal
with N2h, Cl1 and Cl2 occupying the equatorial positions.
In this case, the trigonality index τ, describing the transition
between trigonal bipyramidal and square pyramidal geome-
Reaction of ligand 2 with CuCl ·2 H O in methanol solu-
2
2
tion led to a 1:1 complex of ligand and transition metal ion.
Upon recrystallization in methanol under argon atmo-
sphere, single crystals suitable for X-ray diffraction analysis
were obtained. The molecular structure of the neutral com-
[14]
try, amounts to 0.05.
Upon recrystallization of the amorphous complex 3 from
boiling methanol (rather than from dry methanol at ambi-
ent temperature under argon), a color change took place
from green to dark brown. Single crystal X-ray diffraction
analysis revealed that the brown product comprises a thi-
enyl moiety oxidized at its β position, i.e. 3-hydroxyl-thi-
plex [Cu(2)Cl ] (3) is shown in Figure 1. Table 1 lists rel-
2
evant bond lengths and angles. The thienyl moiety is disor-
dered over two positions (site occupancy factor 90:10; rota-
tion around the C3h–C2t bond), with the majority of the
residues oriented as displayed in Figure 1. DFT calculations
indicate that in the gas phase both conformations are al-
most isoenergetic, with the one favored in the solid state
being disfavored by only 1.6 kJmol . The Cu ion is coor-
dinated by N1p, N2h, Cl1, and Cl2. Moreover, it is engaged
in a long contact with the thienyl sulfur atom S1t
II
enyl. In the resulting Cu complex 4, the oxidized ligand 2Ј
acts as an N,N,O-donor. The unit cell contains two crystal-
lographically independent molecules of 4, one of which is
shown in Figure 2. Relevant bond lengths and angles are
–
1
II
II
listed in Table 2. The Cu ion is coordinated in a square-
[
Cu1···S1t, 3.2409(2) Å]. Previously reported values for the
planar fashion by N1p, N2h, O3t and Cl1. The molecule of
hydration is not coordinated to the metal ion. The distance
II
distance between a Cu ion and a coordinating thienyl sul-
fur atom amount to 3.014(4) Å and 2.335(2) Å, respec-
II
between the two crystallographically independent Cu ions
[
11]
tively.
In those complexes, the thienyl moiety had been
amounts to 12.2823(5) Å, the shortest Cu···Cu distance is
incorporated into a macrocyclic ligand though, thereby pre-
orienting the sulfur ligand in a way that determines its coor-
dination to the metal ion. Assuming van-der-Waals radii of
found between neighboring crystallographically identical
II
Cu ions [4.4286(2) Å].
1
.4 Å (Cu) and 1.8 Å (S),[12] the long contact of 3.2409(2) Å
is at the border of the sum of the van-der-Waals radii and
may therefore be considered non-bonding, which would be
Figure 2. Molecular structure of the metal complex in [Cu(2Ј)Cl]·
2
H O (4) (molecule 2 according to Table 2). Displacement ellipsoids
are drawn at the 50% probability level.
2
Figure 1. Molecular structure of [Cu(2)Cl ] (3). Displacement ellip-
soids are drawn at the 50% probability level.
Table 2. Selected bond lengths and angles of compound 4.
Distance [Å] or angle [°]
Molecule 1
Table 1. Selected bond lengths, interatomic distances and angles of
compound 3.
Molecule 2
Cu1–N1p
Cu1–N2h
Cu1–Cl1
Cu1–O3t
N1p–Cu1–O3t
N2h–Cu1–Cl1
N1p–Cu1–Cl1
O3t–Cu1–Cl1
1.973(2)
1.974(2)
2.2415(8)
1.909(2)
174.25(9)
177.24(8)
97.06(7)
88.61(7)
1.984(3)
1.965(2)
2.2334(9)
1.912(2)
173.5(1)
176.67(8)
97.30(8)
89.15(7)
Distance [Å]
Angle [°]
Cu1–N1p
Cu1–N2h
Cu1–Cl1
Cu1–Cl2
Cu1···S1t
1.9564(1)
2.0018(1)
2.1860(1)
2.2401(1)
3.2409(2)
N1p–Cu1–S1t
N2h–Cu1–Cl1
N1p–Cu1–Cl2
N2h–Cu1–Cl2
S1t–Cu1–Cl2
Cl1–Cu1–Cl2
146.18(3)
148.89(1)
129.92(2)
98.95(1)
75.50(1)
102.91(2)
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The different coordination modes of ligands 2 and 2Ј in to g = 2.1789, g = 2.0661 (3) and g = 2.0716, g = 2.1540
Ќ
ʈ
Ќ
ʈ
compounds 3 and 4 have a significant influence on the UV/ (4), respectively (Figure S3, Supporting Information).
Vis spectra of the complexes (Figure 3, Table 3). Upon for-
Cyclic voltammetry was applied to investigate the influ-
mation of 4, the absorption bands experience a batho- ence of the ligands 2 and 2Ј on the redox properties of the
chromic shift from 250 and 290 nm to 275 and 312 nm, central Cu ion. The cyclic voltammograms of 3 and 4 are
respectively. TD-DFT calculations help to approximately shown in Figure S4, electrochemical data summarized in
assign the absorption bands. It should be noted though that Table S2 (Supporting Information). Complex 3 undergoes a
especially for the shorter-wavelength transitions, this assign- quasireversible Cu-centered redox process at E1/2 = –41 mV,
ment is not unambiguous. As the calculations indicate (see with a cathodic peak at –163 mV and the corresponding
Supporting Information for details), some of the absorption anodic peak at 81 mV. In the case of complex 4, this redox
bands have different underlying electronic transitions. Inter- process tends to become irreversible. With cathodic and an-
estingly, dǞd transitions appear not to be involved, as the odic peaks at –195 mV and 80 mV, the half-potential
frontier orbitals are mainly of Cl 3p character.
amounts to E1 = –57 mV. Hence, complexation by 2Ј
makes the Cu ion marginally less oxidizing than complex-
/2
II
ation by 2.
To elucidate the source of the oxygen atom O3t intro-
duced into the thienyl moiety upon formation of compound
4, recrystallization of complex 3 was repeated in the pres-
ence of isotopically labeled potential oxygen sources. When
18
refluxing complex 3 in a mixture of dry methanol and O-
18
labeled water (H2 O), the product obtained does not show
any incorporation of 18O. As can be seen from Figure 4,
the experimentally determined mass of the reaction product
(
Figure 4, a) does not match the one calculated under the
18
assumption of an incorporation of O (Figure 4, c). To
make sure that the peak around m/z = 297 results from the
presence of 65Cu rather than from O, Figure S5 (Support-
ing Information) shows a detailed depiction of this section
Figure 3. UV/Vis spectra of complexes 3 (black line) and 4 (red
line) in MeOH/DMSO (9:1) at 15 °C.
18
An investigation of the magnetic properties of 3 and 4 of the mass spectrum. The high-resolution mass spectrum
II
65
confirm that both complexes comprise a Cu ion with one clearly indicates that this peak derives from a Cu-contain-
unpaired electron, as indicated by the magnetic moments of ing complex. Hence, water can be excluded as the source of
1
.83(1) μ and 1.84(1) μ , respectively. Figure S1 (Support- the oxygen atom O3t in ligand 2Ј. When performing the
B B
ing Information) shows the respective plots of the magnetic recrystallization from refluxing methanol in the presence of
susceptibility. Interestingly, complex 3 shows antiferromag- gaseous 18
O , the reaction product contains O-labeled li-
18
2
netic behavior below a Néel temperature of TN = 5.3(5) K. gand. Figure 4 (b) clearly shows that the experimentally de-
The temperature-independent magnetic susceptibility termined mass spectrum now matches the one calculated
–
4
–1
18
amounts to χ = 4.60(1)ϫ10 emumol . In contrast, com- assuming an incorporation of O.
0
plex 4 does not display any magnetic order. Its temperature-
independent magnetic susceptibility amounts to χ
The incorporation of 18O during the reaction is also indi-
cated by IR spectroscopy. Figure 5 depicts a representative
.895(1)ϫ10 emumol . Both compounds exhibit slightly cutout of the IR spectra and the assigned ν vibration
negative Weiss constants [complex 3: Θ = –3.2(5) K; com- band of complex 4 and O-labeled 4 with the shift induced
plex 4: Θ = –0.5(5) K] that are indicative of weak antiferro- by O labeling. The full IR spectra are shown in Figures
=
0
–
4
–1
2
C–O
18
P
18
P
magnetic interactions in the paramagnetic domain. As the S6 and S7 (Supporting Information). It is known that com-
shortest intermolecular Cu···Cu distance in 3 [5.6226(3) Å] plexes with low symmetry often display vibrations which
[15]
is larger than that in 4 [4.4286(2) Å], the antiferromagnetic are interfered by the contribution of several modes. The
–
1
[16]
order in complex 3 cannot be explained by direct Cu···Cu band near 1400 cm is assigned to the νC–O vibration for
–1
18
–1
interactions. It is probably due to superexchange via the 4 (1416 cm ) and O-labeled 4 (1408 cm ) and originates
18
weakly bonding thienyl moieties (Figure S2, Supporting In- predominately from that mode. The observed O-shift of
formation). EPR spectra of complexes 3 and 4 confirm their Δν = 8 cm–1 to lower wavenumbers furthermore supports
different coordination environments. The g values amount these findings. Moreover, according to an analysis of the
2
–1
Table 3. UV/Vis spectroscopic data of complexes 3 and 4 in MeOH/DMSO (9:1) at 15 °C (λmax/nm, ε/cm μmol in parentheses), calcu-
lated absorption wavelengths and approximate assignments based on TD-DFT (CAMY-B3LYP/TZP) calculations.
3
Calcd. λ [nm] Assignment
4
Calcd. λ [nm]
Assignment
SOMO
2
2
4
50 (12.7)
90 (12.0)
00 (3.12), 414 (2.99) 444
304
346
n
Cl Ǟπ*, πǞnClSOMO
275 (15.2)
312 (15.9)
400 (16.5), 414 (16.6)
273
290, 296
379
n
n
ClǞ (nCl
SOMO
, π*)
πǞπ*
(π, nCl)ǞnCl
Cl ǞnCl
, πǞπ*
SOMO
πǞπ*
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Figure 4. Sections of ESI-Orbitrap mass spectra of the products obtained upon refluxing complex 3 in a) a mixture of methanol and
1
8
O or b) in methanol under an atmosphere of 18
18
H
2
O
2
. c) For comparison, the calculated mass spectrum of O-labeled complex 4 is
given as well.
harmonic vibration frequencies of the computed structure plexes[6] but is much less known for Cu complexes. Hence,
II
I
of complex 4, the normal mode with the most significant we probed the applicability of Cu complexes of ligand 2 in
–
1
C–O stretching character is found at 1436 cm , which is the context of dioxygen activation. Reaction of compound
in very good agreement with the experimental value. Upon 2 with CuI led to the formation of a dimeric complex of
1
6
18
exchange of O by O, the calculations predict this fre- the composition [Cu(2)I] (5). The molecular structure of 5
2
–
1
quency to shift to 1427 cm . Again, the computed value of was confirmed by single-crystal X-ray diffraction analysis.
Δν of 9 cm nicely agrees with the experimental value of It is shown in Figure 6. Relevant bond lengths and angles
–
1
–
1
8
cm .
are listed in Table 4.
Figure 5. Section of the IR spectra of 4 (red) and the corresponding
18
O-labeled derivative (black).
Thus, molecular oxygen is activated, finally resulting in
an oxidation of the thienyl moiety of the ligand. Oxygen
activation is a well-known phenomenon for Cu com- soids are drawn at the 50% probability level.
2
Figure 6. Molecular structure of [Cu(2)I] (5). Displacement ellip-
I
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II
I
Table 4. Selected bond lengths and angles of compound 5.
forming the Cu complex in situ to its reactive Cu analog.
II
The oxidation of alcohols by Cu complexes is not unprece-
Distance [Å]
Angle [°]
[
18]
dented.
Cu1–N1p
Cu1–N2h
Cu1–S1t
Cu1–I1
Cu1–I1Ј
Cu1···Cu1Ј
2.047(2)
2.131(2)
3.1181(3)
2.6164(3)
2.6031(3)
2.8479(4)
N1p–Cu1–S1t
N2h–Cu1–I1Ј
N1p–Cu1–I1
N2h–Cu1–I1
S1t–Cu1–I1
I1–Cu1–I1Ј
146.27(7)
128.00(4)
115.18(5)
109.56(5)
85.47(5)
Conclusions
We have reported here the in situ reduction of a CuII
complex comprising a hydrazone-based ligand with an
N,N,S-donor environment, followed by dioxygen activation
113.867(9)
I
by the resulting Cu complex. As a result, the thienyl moiety
The thienyl moiety in 5 is disordered over two positions.
In the two symmetry-related ligands displayed in Figure 7,
both orientations are indicated. The disorder suggests that
the Cu1···S1t interaction is not strong enough to induce a
preference for a Cu1–S1t-bonded state. Nonetheless, the
Cu1···S1t distance amounts to 3.1181(3) Å, which is below
the sum of the van-der-Waals radii[ and smaller than the
within the tridentate N,N,S-donor ligand is hydroxylated in
its β position. Even though not catalytic, this finding indi-
cates that hydrazone ligands may be suited for the genera-
tion of novel bioinspired copper-containing oxidation cata-
lysts.
12]
II
corresponding distance in the Cu -containing complex 3.
I
Experimental Section
Materials and Methods: H and 13C NMR spectra were recorded
completed by a long cuprophilic interaction with a bond on Bruker Avance (I) 400 and Avance (III) 400 spectrometers with
The coordination geometry of the Cu ion is similar to the
I
one in compound 3. In the dimeric Cu complex 5, it is
1
length of 2.8478(5) Å.[
17]
an internal standard relative to TMS (δ = 0 ppm) for measurements
in CDCl . In case of using [D ]DMSO and [D ]MeOH, the residual
3
6
4
solvent signal was used as an internal standard. The atom-number-
ing scheme used in the list of NMR chemical shifts given below is
identical to the one used in Figure 1. Electrospray ionization ex-
periments (ESI-TOF) for compounds 1 and 2 were performed using
the oa-TOF mass spectrometer MicrOTOF (Bruker Daltonik
GmbH, Bremen, Germany). The MicrOTOF was equipped with a
standard ESI source. All mass spectra are quasi-internally mass
calibrated by the measurement of an infused calibrant (ammonium
formate) prior to the compound of interest. ESI-MS spectra for
compounds 3–6 were measured on an LTQ Orbitrap XL (Thermo
Scientific, Bremen, Germany), equipped with the static nanospray
probe (slightly modified to use self-drawn glass nanospray capillar-
ies, spray voltage 1.0–1.4 kV, capillary temperature 200 °C, tube
lens approx. 50–120 V). The scan type settings used for the analysis
are: analyzer: Fourier transform mass spectrometer (FTMS) op-
erating full range mode from 200–2000 m/z; resolution:
1
00,000 FWHM (full width at half maximum); polarity: positive.
Figure 7. Section of an ESI-Orbitrap mass spectrum of the product
obtained upon stirring complex 6 in methanol under aerobic condi-
tions (top) and calculated mass of the oxidized complex (bottom).
18
Infrared (IR) spectra for compounds [Cu(2Ј)Cl] and O-labeled
Cu(2Ј)Cl] were recorded using a Bruker Vertex 70 instrument with
[
–
1
a resolution of 1 cm and 32 scans. An ATR cell (diamond) was
used for recording IR spectra. The intensities are reported relative
to the most intense peak and are given in parenthesis using the
following abbreviations: vw = very weak, w = weak, m = medium,
s = strong, vs. = very strong. The elemental analyses were recorded
on a Vario EL III CHNS analyzer. Single crystal X-ray diffraction
Probably as a result of the dimeric arrangement and be-
cause of strong Cu–I bonds, compound 5 is unreactive
towards molecular oxygen. Hence, it is not oxidized even in
refluxing methanol under aerobic conditions.
Reaction of ligand 2 with CuCl led to the formation of
α
data were collected with graphite-monochromated Mo-K radia-
the monomeric complex [Cu(2)Cl] (6). Compound 6 is tion (λ = 0.71073 Å) on an Xcalibur system or a Bruker APEX
highly reactive towards molecular oxygen even at ambient diffractometer. The structures were solved by direct methods and
2
temperature, as indicated by the mass spectrum of the oxid- were refined by full-matrix, least-squares on F by using the
SHELXTL and SHELXL-97 programs.[ Crystallographic data
19]
1
ized complex (Figure 7) and by the fact that its H NMR
are reported in Table S1 (Supporting Information). CCDC-
031112 (for 3), -1031113 (for 4), and -1031114 (for 5) contain the
spectrum shows broad signals only (Figure S17, Supporting
Information), indicative of the formation of a paramagnetic
1
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Cyclic vol-
tammetry measurements were performed on a Metrohm/Eco
Chemie PGSTAT30 instrument vs. ferrocenium/ferrocene using a
II
Cu species.
Hence, it can be concluded that the dioxygen activation
observed for the CuII complex 3 in fact proceeds via a Cu
intermediate. As the oxidation of the ligand takes place only
I
once the complex has been refluxed in methanol, it is safe silver reference electrode and a platinum counter electrode. The
to assume that methanol acts as the reducing agent, trans- magnetic property measurements were carried out with a Quantum
Eur. J. Inorg. Chem. 2015, 4006–4012
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Design Physical Property Measurement System using a Vibrating
Sample Magnetometer. The measurements were performed in the
temperature range of 3–300 K with flux densities up to 10 kOe.
EtOH (40 mL) was added slowly. The resulting suspension was
stirred for 3 h at ambient temperature. The solid was filtered off,
washed with Et O and dried in vacuo, yield 80% (1.28 g,
2
9.044 mg of complex 3 and 19.220 mg of complex 4 were packed
3.67 mmol). Single crystals of compound 3 were obtained by crys-
in polypropylene capsules and affixed to a brass sample holder rod
for the measurements. All structures have been optimized using un-
restricted Kohn–Sham DFT with the TPSS exchange–correlation
tallizing the amorphous compound from dry methanol under an
atmosphere of Et
m/z 314.96527: calcd. for
314.96516. C11 CuN S (351.74): calcd. C 37.6, H 3.2, N 12.0;
2
O and argon. MS (ESI-Orbitrap, positive mode)
+
11 3
C H11ClCuN S [M–Cl] , found
[
20]
functional
within the resolution-of-the-identity (RI) approxi-
H
11Cl
2
3
[21]
mation with the Turbomole program version 6.5.
The def2-
found C 37.6, H 3.1, N 12.0. Due to the paramagnetic nature of 3,
no NMR spectra have been recorded.
TZVP basis has been employed in these calculations.[ Vibrational
frequencies have been calculated with TPSS/def2-TZVP as well.
For comparison, test optimizations using either TPSS with D3 dis-
22]
[Cu(2Ј)Cl] (4): Complex 3 (1.16 g, 3.32 mmol) was dissolved in a
methanol/water mixture (3:1, 36 mL) and refluxed for 5 min under
ambient atmosphere. Single crystals of compound 4 were obtained
by slow evaporation of the solvent over one week. The product was
[
23]
[24]
persion correction or the B3LYP hybrid functional have been
carried out, but resulted in insignificant structural differences. All
complexes have been calculated as neutral molecules with a doublet
occupation; spin contamination was found to be very low (typical
filtered, washed with Et
tals 14% (153 mg, 0.464 mmol). IR (300 K, ATR): ν˜ = 1830 (w),
767 (vw), 1647 (vw), 1611 (s), 1577 (w), 1552 (m), 1517 (m), 1487
m), 1463 (w), 1443 (m), 1428 (w), 1416 (vs), 1395 (w), 1336 (m),
307 (w), 1206 (w), 1192 (vw), 1164 (m), 1145 (w), 1109 (w), 1083
w), 1052 (vw), 1046 (w), 1036 (vw), 1010 (s), 986 (vw), 962 (m),
18 (w), 864 (w), 850 (w), 822 (m), 770 (w), 755 (s), 729 (w), 693
2
O and dried in vacuo, yield of single crys-
2
values for ϽS Ͼ: ca. 0.752 for TPSS calculations, ca. 0.754 for
1
(
1
(
B3LYP calculations). Additional single-point calculations have
been carried out using the Coulomb-attenuating method functional
[
25]
CAMY-B3LYP making use of Yukawa-type range-separation,
and the range-separated hybrid functional ωB97.[ Excitation en-
26]
9
[
27]
ergies have been calculated using ADF (CAMY-B3LYP/TZP),
–
1
(
m), 660 (w), 637 (vw) cm . MS (ESI-Orbitrap, positive mode) m/z
and Q-CHEM (ωB97/6-31G*)[ using the unrestricted TDDFT
formalism. CAMY-B3LYP calculations in ADF have been per-
formed with the full exchange–correlation kernel, making use of
28]
+
294.98311: calcd. for C11
3
H10CuN OS [M – Cl] , found 294.98351.
11
C H
10ClCuN OS·0.5H O (340.3): calcd. C 38.8, H 3.3, N 12.4;
3
2
found C 38.8, H 3.0, N 12.3. Due to the paramagnetic nature of 4,
no NMR spectra have been recorded.
[
29]
the xcfun library.
Oscillator strengths have been obtained from
the dipole-length representation. Spectra are obtained from stick
spectra of oscillator strengths at vertical excitation energies, to
which a Gaussian broadening of 0.2 eV has been applied.
18O-Labeled [Cu(2Ј)Cl]: Complex 3 (20 mg, 57 μmol) was dried
overnight in vacuo. After flushing the reaction vial with argon, dry
MeOH (3 mL) and doubly distilled, degassed water (1 mL) were
added. The mixture was refluxed for 5 min, cooled to ambient tem-
2
9
1
-(1-Methylhydrazinyl)pyridine (1): 2-Chloropyridine (7.5 mL,
0 mmol) and methylhydrazine (30 mL) were refluxed for 16 h at
35 °C. Excess methylhydrazine was removed in vacuo and CH Cl
2 2
1
8
perature, and the argon was replaced by
2
O . Single crystals were
obtained by slow evaporation of the solvent over a duration of five
days. IR (300 K, ATR): ν˜ = 1979 (w), 1833 (vw), 1656 (vw), 1644
(
K
80 mL) was added. The reaction mixture was quenched with
CO (21 g, 15 mmol) and stirred for 30 min. After filtration, the
solvent was removed and the orange oily product dried in vacuo,
2
3
(
w), 1611 (m), 1577 (w), 1553 (m), 1518 (w), 1488 (vs), 1464 (w),
1442 (m), 1428 (w), 1408 (m), 1393 (w), 1337 (s), 1308 (w), 1254
vw), 1207 (w), 1164 (m), 1145 (w), 1110 (w), 1085 (vw), 1042 (w),
010 (m), 962 (m), 918 (w), 863 (w), 851 (w), 822 (w), 756 (vs), 693
1
yield 76% (8.43 g, 68.5 mmol). H NMR (CDCl
=
1
3
): δ = 8.14 (dd, J
4.9 Hz, 0.9 Hz, 1 H, H6p); 7.45 (ddd, J = 8.7 Hz, 7.1 Hz, 1.9 Hz,
H, H4p); 6.92 (d, J = 8.7 Hz, 1 H, H3p); 6.58 (m, 1 H, H5p);
(
1
–
1
13
(vw), 685 (w), 659 (w), 644 (vw) cm . MS (ESI-Orbitrap, positive
4
.02 (s, 2 H, NH
2
); 3.23 ppm (s, 3 H, CH
3 3
). C NMR (CDCl ): δ
1
8
+
mode) m/z 296.98775: calcd. for C11
96.98776.
3
H10CuN OS [M – Cl] , found
=
161.2 (C2p); 147.3 (C6p); 137.1 (C4p); 112.8 (C5p); 107.2 (C3p);
2
4
1.0 ppm (C4h). MS (ESI-TOF, positive mode) m/z 124.0869:
+
calcd. for C
124.96 ): calcd. C 57.7, H 7.4, N 33.6; found C 57.9, H 7.2, N
3.5.
E)-2-[1-Methyl-2-(thiophen-2-ylmethylene)hydrazinyl]pyridine (2):
6
H
9
N
3
[M + H] , found 124.0855. C
6
H
9
N
3
·0.1H
2
O
[Cu(2)I] (5): A suspension of CuI (88 mg, 0.46 mmol) in MeOH
2
(
3
(10 mL) was treated with a solution of compound 2 (100 mg,
460 μmol) in MeOH (10 mL). After stirring for 2 h at ambient tem-
perature, the suspension was filtered and washed with Et
product was dried at 40 °C and obtained in 82% yield (153 mg,
76 μmol). The signals in the NMR spectra of this compound are
broadened out, probably due to a paramagnetic impurity. Hence,
2
O. The
(
To a solution of compound 1 (0.99 g, 8.0 mmol) in EtOH (50 mL),
acetic acid (0.7 mL) and 2-thiophenecarbaldehyde (0.76 mL, 0.91 g,
3
8
.1 mmol) were added. The reaction mixture was stirred at 60 °C
for 50 min and then frozen in liquid nitrogen. After storage at
26 °C for 16 h, the solid was filtered off and washed with water.
1
no coupling constants can be given. H NMR (CDCl
1 H, H6p); 8.12 (1 H, H3h); 7.76 (1 H, H5t); 7.54 (1 H, H4p);
7.47 (2 H, H3t, H4t); 7.07 (1 H, H5p); 6.89 (1 H, H3p); 3.64 (3 H,
3
): δ = 8.30
(
–
1
The product was dried in vacuo, yield 80% (1.39 g, 6.41 mmol). H
NMR (CDCl ): δ = 8.20 (dd, J = 4.9 Hz, 1.7 Hz, 1 H, H6p); 7.80
s, 1 H, H3h); 7.67 (d, J = 8.6 Hz, 1 H, H3p); 7.59 (ddd, J = 8.7 Hz,
1
3
CH
3
) ppm. C NMR (CDCl
C2t); 138.0 (C4p); 132.9 (C3h); 129.6 (C5t); 127.4 (C4t); 127.0
C3t); 115.5 (C5p); 108.5 (C3p); 31.3 ppm (C4h). MS (ESI-
11CuN
[M – I] , found 279.99642. C H CuIN S (407.74): calcd. C 32.4,
3
): δ = 154.6 (C2p); 146.0 (C6p); 139.1
3
(
(
(
7.1 Hz, 1.7 Hz, 1 H, H4p); 7.24 (d, J = 5.0 Hz, 1 H, H5t); 7.15 (d,
Orbitrap, positive mode) m/z 279.99642: calcd. for C11
H
3
S
J = 3.6 Hz, 1 H, H3t); 7.03 (dd, J = 5.0 Hz, 3.6 Hz, 1 H, H4t);
+
13
6.77 (m, 1 H, H5p); 3.63 ppm (s, 3 H, CH
3
). C NMR (CDCl
3
):
11 11
3
H 2.7, N 10.3; found C 32.6, H 2.6, N 10.0.
Cu(2)Cl] (6): To a suspension of CuCl (108 mg, 1.10 mmol) in
0 mL of MeOH a solution of compound 2 (237 mg, 1.09 mmol)
δ = 157.4 (C2p); 146.8 (C6p); 142.1 (C2t); 137.6 (C4p); 128.9 (C3h);
1
2
27.3 (C3p); 126.4 (C3t); 125.5 (C5t); 115.5 (C4t); 109.9 (C5p);
[
1
9.5 ppm (C4h). MS (ESI-TOF, positive mode) m/z 218.07464:
+
calcd. for C11
H
12
N
3
S [M + H] , found 218.07434. C11
H
11
N
3
S
in 10 mL of MeOH was added. After stirring for 90 min at ambient
temperature the product was filtered, washed with MeOH and
dried in vacuo. Because of the high reactivity towards molecular
(217.29): calcd. C 60.8, H 5.1, N 19.3; found C 60.5, H 5.1, N 19.1.
[
Cu(2)Cl ] (3): Compound 2 (1.00 g, 4.61 mmol) was dissolved in
2
1
EtOH (30 mL). A solution of CuCl
2
·2H
2
O (772 mg, 4.57 mmol) in
oxygen, the yield was not determined. The H NMR spectroscopic
Eur. J. Inorg. Chem. 2015, 4006–4012
4011
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
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Published Online: July 20, 2015
Eur. J. Inorg. Chem. 2015, 4006–4012
4012
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim