The synthesis of the first Ag(I) complexes with ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) is presented. The reaction of AgClO4 with the ligand in a molar ratio of 1:1 gives a bis(ligand) ...complex AgL2ClO4 (1) in the presence of 4-formylbenzonitrile, monoperiodic polymer {AgL2ClO4}n (2). Characterization involved IR spectroscopy, conductometric measurements, thermogravimetric analysis, antioxidant tests, powder, and single crystal X-ray diffraction. Structural analysis revealed ligand coordination in a monodentate manner through the nitrogen atom of the pyrazole ring in both complexes. Complex 1 displayed a linear coordination environment for Ag(I), whereas, in complex 2, square-planar coordination was achieved with the additional involvement of two oxygen atoms from bridging perchlorate anions. Notably, the thermal properties of both isomers are found to be nearly identical. The significant antioxidant activity of the isomer with a reverse-oriented pyrazole-type ligand suggests its potential relevance in biological studies.
•Synthesis of Fe3O4 nanoparticles and surface modification with CA, DEX and APTES.•The correlation of the SAR with the magnetite surface-modifier intrinsic properties.•Biosensors construction by ...modification of SPC electrodes with coated magnetite.•The relationship of biosensor efficiency with surface-modifier of SPC electrodes.•Development of the electroanalytical procedure for the determination of dopamine.
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The citric acid (CA), dextran (DEX) and (3-aminopropyl)triethoxysilane (APTES) are frequently used ligands for surface modification of magnetite nanoparticles to improve their colloidal stability and biocompatibility for use in biomedicine. Here we report the synthesis, surface modification of magnetite (Fe3O4) nanoparticles and analysis of the influence of coating materials on heating efficiency in magnetic hyperthermia, as well as on electrochemical sensing toward the detection of neurotransmitter dopamine (DOP). Spherical magnetite nanoparticles (~13 nm) were prepared by co-precipitation and surface-modified with CA, APTES and DEX. The hyperthermia tests revealed that Fe3O4@APTES resulted in the highest specific absorption rate (SAR) of 67.2 W/g. The engineered sensor, by surface modification of screen-printed carbon (SPC) electrodes with Fe3O4@APTES, showed linear response with DOP in the concentration range of 1−200 μM and a low detection limit of 34.3 nM. Besides, the sensor offered remarkable selectivity, repeatability and reproducibility. Application of SPC-, Fe3O4-, Fe3O4@CA- and Fe3O4@DEX-modified SPC electrode resulted in lower electrocatalytic activity compared with Fe3O4@APTES/SPC. The obtained results indicate the effects of a surface modifier especially that Fe3O4@APTES, alone and combining with SPC electrodes, can serve as an agent in various types of biomedical applications, like hyperthermia and electrochemical sensing of biologically active compounds such as DOP.
Four new coordination compounds of Cu(II) were synthesized with ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) and different co-ligands. In the reaction of warm methanolic solutions of CuX
2
·
...n
H
2
O (X = Cl,
n
= 2; X = Br,
n
= 0; X = NO
3
,
n
= 3) and the ligand in mole ratio 1:2, bis(ligand) complexes Cu(L)
2
Cl
2
(
1
), Cu(L)
2
Br
2
(
2
) and Cu(L)
2
(NO
3
)
2
(
3
) were obtained. Unlike this, reaction of CuCl
2
with the ligand in the presence of LiOAc yielded to the formation of dimeric complex of the formula Cu(L)(OAc)
2
2
(
4
), with four acetate ions as bridging ligands. In all these complexes, ligand L is coordinated in a monodentate manner through N2 nitrogen atom. The coordination environment in the dimeric complex is octahedral, while in the monomeric complexes the central atom is tetra-coordinated. The molar conductivity data in DMF show that the acetate ions in the dimeric complex are coordinated even in solution. In the monomeric compounds, the molar conductivity data increase in the order
1
<
2
<
3
. Since the applicability of the coordination compounds depends on their thermal properties, the thermal decomposition of the complexes was followed by simultaneous TG–DSC measurements. The thermal stability of the monomeric compounds in flowing argon increases in the reverse order as the molar conductivity data. The course of the decomposition is different in the case of the nitrato-compound (
3
). The decomposition of
3
is followed by a strong exothermic heat effect due to the presence of nitrate ion which is a strong oxidation agent. The decomposition of the other complexes is endothermic, taking place in more or less overlapped reactions. The decomposition of the compounds is completed to 600 °C.
The reactions of pyrazole derivative, i.e., ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) with zinc halogenides in methanolic solution and zinc nitrate and zinc acetate in acetonic solution ...are described. The formulae of synthesized compounds are ZnL2Cl2 (1), ZnL2Br2 (2), ZnL2I2·0.5MeOH (3), Zn(L)2(H2O)4(NO3)2 (4), and {ZnL(OAc)2}2 (5). Two complexes are obtained in form of single crystals: ZnL2Br2 (2) and Zn(L)2(H2O)4(NO3)2 (4). Their crystal and molecular structure were determined by single-crystal X-ray structure analysis. The FTIR spectra of compounds prove the complex formation with all five zinc salts. The complexes are characterized by conductometric and thermoanalytical measurements, and their antioxidative activity was also tested by the scavenging effect on the DPPH radical. Conductometric results, solvolytic stability, and antioxidative activity of the compounds are in correlation.
Pyrazole (pz)‐derived ligands can, besides exhibiting a strong coordination ability toward different metal ions, exhibit a great diversity in their coordination geometry and nuclearity, which can be ...achieved by varying the type and position of the pz substituents. The present study reports the synthesis and crystal structure of two binuclear complexes, namely bis(μ‐4‐nitro‐1H‐imidazol‐1‐ide‐5‐carboxylato)‐κ3N1,O:N2;κ3N2:N1,O‐bisaqua(dimethylformamide‐κO)copper(II), Cu2(C4HN3O4)2(C3H7NO)2(H2O)2, (II), and bis(μ‐4‐nitro‐1H‐imidazol‐1‐ide‐5‐carboxylato)‐κ2N1,O:N2;κ2N2:N1,O‐bistriaquacobalt(II) dihydrate, Co2(C4HN3O4)2(H2O)6·2H2O, (III). These compounds represent rare examples of metal complexes comprising 3,4‐substituted pz derivatives as a bridging ligand and also the first crystal structures of transition‐metal complexes with ligands derived from 4‐nitropyrazole‐3‐carboxylic acid. Recently, the crystal structures of the same ligand in the neutral and mixed neutral/anionic forms have been reported. We present here the third form of this ligand, where it is present in a fully deprotonated anionic form within a salt, i.e. ammonium 4‐nitropyrazole‐3‐carboxylate, NH4+·C4H2N3O4−, (I). Single‐crystal X‐ray diffraction revealed that in the present complexes, the CuII and CoII centres adopt distorted square‐pyramidal and octahedral geometries, respectively. In both cases, the N,N′,O‐coordinated pz ligand shows simultaneously chelating and bridging coordination modes, leading to the formation of a nearly planar six‐membered M2N4 metallocycle. In all three crystal structures, the supramolecular arrangement is controlled by strong hydrogen bonds which primarily engage the carboxylate O atoms as acceptors, while the nitro group adopts the role of an acceptor only in structures with an increased number of donors, as is the case with CoII complex (III). The electrostatic potential, as a descriptor of reactivity, was also calculated in order to examine the changes in ligand electrostatic preferences upon coordination to metal ions.
The title structures represent rare examples of metal complexes comprising a 3,4‐disubstituted pyrazole derivative as a bridging ligand and the first crystal structures of metal complexes with a 4‐nitropyrazole‐3‐carboxylic acid‐based ligand.
Abstract
C
10
H
9
BrN
2
, orthorhombic,
P
2
1
2
1
2
1
(no. 19),
a
= 5.9070(3) Å,
b
= 9.2731(7) Å,
c
= 17.5641(14) Å,
V
= 962.09(12) Å
3
,
Z
= 4,
R
gt
(
F
) = 0.0504,
wR
ref
(
F
2
) = 0.0947, ...T = 293(2) K.
Abstract
C
4
H
2
N
3
BrO
4
·H
2
O, monoclinic,
P
2
1
/
c
(no. 14),
a
= 7.177(2) Å,
b
= 10.999(3) Å,
c
= 10.414(3) Å,
β
=
100.145
(
11
)
∘
$100.145{(11)}^{\circ }$
,
V
= 809.3(4) Å
3
,
Z
= 4,
R
...g
t
${R}_{\mathrm{g}\mathrm{t}}$
(
F
) = 0.0379,
w
R
r
e
f
$w{R}_{\mathrm{r}\mathrm{e}\mathrm{f}}$
(
F
2
) = 0.0714, T = 200 K
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