Blue prismatic crystals of mononuclear CuII(O2CH)2(Py)3 (Py = pyridine, C5H5N), 1, were prepared from reaction solution containing dry pyridine and dinuclear Cu2II(O2CH)4(Py)2. When a portion of ...solution together with crystals was exposed to air moisture, crystals of 1 dissolved in mother liquid. Simultaneously, blue needles of 2, i.e. covalently linked one-dimensional chain structure with formula Cu(O2CH)2(Py)2n·nH2O, grew out of the solution. The process lasted few minutes and was observed under optical microscope. The conversion from 1 to 2 takes place also outside of solution in the solid state. Single crystal X-ray diffraction data were collected at 150 K for 1 and after that for 2, originating from the same reaction solution. This paper reports the structures of both compounds. Alternative synthesis method of 2 arising from a mixture of copper methanoate and pyridine is also reported.
The synthesis and characterization of two polymorphic modifications of new cobalt coordination compound with 2-aminopyridine are reported. Acetate and 2-aminopyridine ligands in both structures are ...lying
cis about the metal centre. The main reason for asymmetry of acetate ligand chelate bonding in both modifications are intra- and intermolecular hydrogen bonds.
The synthesis and characterization of two polymorphic modifications of new cobalt coordination compound with 2-aminopyridine are reported. The modifications were prepared by the reaction of a solution of cobalt acetate tetrahydrate and 2-aminopyridine. The crystal structures of both polymorphic modifications have been determined by single-crystal X-ray diffraction analysis. The structures of both modifications are quite similar. In both of them the Co
2+ is six coordinated by four
O atoms from two bidentate chelate acetate ligands and by two
N atoms from two 2-aminopyridine molecules. Acetate and 2-aminopyridine ligands are lying
cis about the metal centre. The most important difference is in asymmetry of acetate ligand chelate bonding and in H-bonding network. Compounds exhibit an extensive system of intra and intermolecular hydrogen bonding. Magnetic properties of both modifications were studied between 2
K and 300
K giving the result
μ
eff
=
4.6 BM for modification
I and
μ
eff
=
4.7 BM for modification
II in paramagnetic region.
A novel
paddle-wheel type of a tetranuclear copper(II) carboxylate is reported. The compound {Cu
2(OOCC
5H
11)
4(urea)}
2 shows strong antiferromagnetic properties that were compared with related ...isolated dinuclear and polymeric compounds Cu
2(OOCC
5H
11)
4(urea)
2, Cu
2(OOCC
5H
11)
4
n
, respectively. A solid-to-solid phase transition for {Cu
2(OOCC
5H
11)
4(urea)}
2 was observed by magnetic measurement and analysed for the whole series {Cu
2(OOCC
m
H
2
m
+
1
)
4(urea)}
2 (
m=6–11) by TG and DTA measurements.
A series of compounds of formula {Cu
2(OOCC
m
H
2
m
+
1
)
4(urea)}
2 (
m=5–11) have been characterized. X-ray structure analysis for the hexanoate compound reveals a new type of tetranuclear dicopper(II) tetracarboxylate, where the central coordination sphere in {Cu
2(OOCC
5H
11)
4(urea)}
2 is composed of two dinuclear dicopper tetracarboxylates, connected via two inter-dinuclear Cu–O coordination bonds at a distance 2.222(2) Å through the apical positions of two dimers. Urea molecules (Cu–O 2.114(2) Å) occupy both outside apical positions of the resulting tetranuclear units. A strong antiferromagnetic behaviour has been shown for {Cu
2(OOCC
5H
11)
4(urea)}
2 (−2
J=261.4(4) cm
−1), and compared with related isolated dinuclear and polymeric hexanoate compounds Cu
2(OOCC
5H
11)
4(urea)
2, Cu
2(OOCC
5H
11)
4
n
, respectively. Only small differences in the magnetic susceptibility have been found, while EPR spectroscopy showed significantly different results for all three hexanoate compounds, also with the dicopper tetracarboxylate central core and square-pyramidal CuO
4O chromophores. A solid-to-solid phase transition for {Cu
2(OOCC
5H
11)
4(urea)}
2 was observed by magnetic measurement and analysed for the whole series {Cu
2(OOCC
m
H
2
m
+
1
)
4(urea)}
2 by TG, DTA, and variable temperature XRD studies.
Compound Cu
2(μ-L)
4(HL)
2 (
1) (HL
=
2-pyridone) shows the dinuclear cage structure with four triatomic N–C–O bridges (
paddle wheel) and monodentate apical 2-pyridones. The EPR spectra show six ...signals, as suggested for
S
=
1 spin state and
D
=
0.293
cm
−1
<
hν
=
0.320
cm
−1. Compound
1 is compared with related mixed pyridin-2-olato-methanoato complex Cu
2(μ-HCO
2)
2(μ-L)
2(HL)
2 (
2a), showing similarly strong antiferromagnetism (2
J
=
−334 (
1), −324
cm
−1 (
2a)).
A novel dinuclear complex Cu
2(μ-L)
4(HL)
2 (
1) was isolated from starting 2-pyridone (HL) via a resonance and a tautomeric transformation. Each copper centre is in a square-pyramidal coordination sphere, defined by two oxygen atoms (Cu–O4 1.978(5), Cu–O11 1.964(4)
Å) and two nitrogen atoms (Cu–N2 2.003(5), Cu–N3 2.007(5)
Å) of four bridging deprotonated pyridin-2-olates and an oxygen atom on the top from a neutral 2-pyridone (Cu–O2 2.227(5)
Å), analogous to tetracarboxylate
paddle-wheel complexes. Compound
1 was compared with mixed pyridin-2-olato/methanoato analogues Cu
2(μ-HCO
2)
2(μ-L)
2(HL)
2
·
2CH
3CN (
2) and Cu
2(μ-HCO
2)
2(μ-L)
2(HL)
2 (
2a) (
2a is an air stable form obtained from
2 outside mother-liquid). The EPR spectra of air stable
1 and
2a show three signals
H
z1
,
H
⊥2 and
H
z2
, typical for the binuclear systems with spin
S
=
1, both revealing strong antiferromagnetism 2
J
=
−334 (
1) and −324
cm
−1 (
2a). Interestingly, only for
1 additional
H
⊥1 signal at 100
mT is noticed (
D(
1)
=
0.293
cm
−1
<
hν
=
0.320
cm
−1
<
D(
2a)
=
0.347
cm
−1). On the other hand, several broad signals in the 100–450
mT region, only in the high temperature spectrum for
2a are observed. These results are in agreement with the magnetic susceptibility analysis.
Monomeric Cu(O
2CH)
2(2-mpy)
2, dimeric Cu
2(μ-O
2CH)
4(2-mpy)
2 and two polymeric complexes of alternate monomeric and dimeric building blocks, {Cu(μ-O
2CH)
2(2-mpy)
2Cu
2(μ-O
2CH)
4}
n
(2-mpy
=
...2-methylpyridine) and {Na
2Cu(μ-O
2CH)
2(O
2CH)
2Cu
2(μ-O
2CH)
4}
n
, have been characterized. A very strong antiferromagnetic (AFM) interaction is found for all the complexes with
paddle-wheel building blocks Cu
2(μ-O
2CH)
4 (2
J
=
444–482
cm
−1), attributed to the methanoate intra-binuclear bridges. This strong AFM coupling also plays an important role in the EPR signals of the two polymeric complexes, and differs structurally, especially with the monomer-dimer intra-chain bridges.
Several copper(II) methanoato complexes, namely mononuclear Cu(O
2CH)
2(2-mpy)
2 (
1) (2-mpy
=
2-methylpyridine), binuclear Cu
2(μ-O
2CH)
4(2-mpy)
2 (
2), and the polynuclear {Cu(μ-O
2CH)
2(2-mpy)
2Cu
2(μ-O
2CH)
4}
n
(
3) and {Na
2Cu(μ-O
2CH)
2(O
2CH)
2Cu
2(μ-O
2CH)
4}
n
(
4), have been synthesized. The mononuclear complex
1 is formed by two asymmetric chelate methanoate anions and two 2-methylpyridine molecules, giving a highly distorted ‘elongated octahedral’ coordination sphere. Complex
1 decomposes outside the mother-liquid, transforming into a regular isolated binuclear
paddle-wheel complex
2 with four intra-binuclear bridging methanoates and two axial 2-mpy ligands. The polynuclear complex
3 is formed of alternate mononuclear and binuclear building blocks resembling the central cores of
1 and
2, but with significant differences, especially for the methanoates of the mononuclear units. The oxygen atom of the mononuclear unit in the octahedral axial position in
3 is simultaneously coordinated to the axial position of the binuclear
paddle-wheel central core, thus enabling a chain type of structure. A chain of alternate mononuclear and binuclear building blocks, as in the neutral compound
3, are found as well in the ionic polymeric compound
4, though two types of bridges are found in
4, while there is only one type in
3. Namely, the axial position of the octahedral mononuclear unit in
4 is occupied by the methanoate oxygen atom that is already a part of the binuclear
paddle-wheel unit, while one equatorial methanoate from the mononuclear unit serves as a triatomic bridge to the axial position of the binuclear building block. A very strong antiferromagnetic interaction is found for all the complexes with the
paddle-wheel building blocks Cu
2(μ-O
2CH)
4
2–
4 (−2
J
=
444–482
cm
−1), attributed to the methanoate intra-binuclear bridges. On the other hand, this strong antiferromagnetism, found already at room temperature, reduces the intensity of the EPR
S
=
1 spin signals reported for the isolated
paddle-wheel complex
2. For the polymeric
3, only the spin
S
=
½ signals are found in the EPR spectra, and they are assigned to the mononuclear building blocks. No signals with a clear origin are however seen in the room temperature EPR spectrum of the polymeric analogue
4, only the
S
=
½ signals in the low temperature spectra. This feature is suggested to be due to a specific influence between the adjacent
S
=
1 (binuclear) and
S
=
½ (mononuclear) species via their bridges.
Magnetic interactions in a new copper(II) carboxylate complex {Cu
2(O
2CH)
4}{Cu(O
2CH)
2(2-methylpyridine)
2} were studied with the aim of better understanding magneto-structural correlation in a ...quasi 1-D spin arrangement. The only magnetic ions in the structure (Cu
2+,
S=1/2) form chains of dimer–monomer units. Copper ions in dimers are bridged by four carboxylate groups with an antiferromagnetic exchange coupling
J/
k
B=−320
K. Susceptibility of the monomer copper ions follows Curie 1/
T law down to 20
K. Below 20
K the susceptibility abruptly decreases due to the antiferromagnetic coupling between monomers.
Three new copper (II) acetate complexes with nicotinamide (nia) were synthesized analyzed and characterized by standard chemical and physical methods and tested for fungicidal activity The crystal ...and molecular structures of the compounds Cu
2 (O
2CCH
3)
4 (nia) (1B) and Cu
2 (O
2CCH
3)
4 (nia)
2 (2) were determined by X-ray diffraction Both consist of binuclear units of bridging tetracarboxylate type however they differ in the bonding mode of nicotinamide molecules They are bonded at the apical positions of the dimers and connect them in an infinite chain in 1B On the other hand the dimers remain isolated in the structure of the compound 2 It seems that compound 1B is the first example where a nicotinamide molecule acts as a bidentate bridging ligand The results of EPR spectra agree with the dimeric nature of the complexes Dissolved in water or DMSO the compounds completely stop mycelial growth at a concentration of 50×10
−3 mol l
−1 Less concentrated solutions (up to 10×10
−3 mol l
−1) show weaker fungicidal activity.
The chemistry of copper(II) is widely described in the literature due to its importance in various
fields of research and because of the relative ease in the synthesis of new compounds. The
...magnetochemistry is one of these fields. However the results obtained with 'the magnetic methods'
e. g. EPR and magnetic susceptibility, that may enable important insight in the properties of the
compounds, are very often ambiguous. The structural correlation of the wide range of copper(II)
complexes with the magnetic analysis can fulfil some gaps in this area. A series of copper(II)
complexes, synthesized in our lab during the last decade, is discussed.
The novel copper(II) coordination compound, Cu2(O2CH)4(nia)2 (nia = nicotinamide), was isolated from the reaction mixture containing Cu2(OH)2CO3, nicotinamide, methanoic acid and ethanol. The new ...complex was characterized by X-ray single crystal diffraction and other standard physico-chemical methods. The structure contains binuclear centrosymmetric molecules in which two central atoms are bridged by four methanoate bridges forming a paddle-wheel structure type. The fifth coordination site completing the distorted square pyramid around copper is occupied by aromatic nitrogen of nicotinamide. The molecules pack together via hydrogen bonds resulting in a formation of extended supramolecular sheets. The results of other physical measurements are also in a complete agreement with the obtained structure.
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