Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) ...spectroscopy and single crystal X-ray diffraction methods. The complexes
,
and recently synthesized Zn
(NCS)
(
= (
)-
,
,
-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex
were tested as potential catalysts for the ketone-amine-alkyne (KA
) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6-31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO-LUMO), the reactivity descriptors, such as chemical potential (
), hardness (
), softness (
), electronegativity (
) and electrophilicity index (
) have been calculated. The energetic behavior of the investigated compounds (
and
) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized Zn
(NCS)
complex
. DFT results show that compound
has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule.
Two new Zn(II) complexes bearing tridentate hydrazone‐based ligands with NNO or NNS donor atoms were synthesised and characterised by elemental analysis, infrared (IR) and nuclear magnetic resonance ...(NMR) spectroscopies, and single crystal X‐ray diffraction methods. These complexes, together with four previously synthesised analogues, having hydrazone ligands with a NNO donor set of atoms, were successfully employed as catalysts in the ketone‐amine‐alkyne (KA2) coupling reaction, furnishing tetrasubstituted propargylamines, compounds with unique applications in organic chemistry. DFT calculations at the CAM‐B3LYP/TZP level of theory were performed to elucidate the electronic structure of the investigated Zn(II) complexes, excellently correlating the structure of the complexes to their catalytic reactivity.
In this manuscript, the synthesis, characterization, and crystal structures of ZnII complexes bearing hydrazone ligands are described. The complexes were evaluated as possible catalysts in the ketone‐amine‐alkyne coupling reaction. Insights into the catalytic activity of the ZnII complexes were obtained by electronic structure investigations, using DFT calculations.
Two square?planar complexes, PtLCl (1) and PdLCl (2), were synthesized with quinoline-2-carboxaldehyde thiosemicarbazone ligand (HL), and characterized by IR and NMR spectroscopy and single crystal ...X-ray diffraction analysis. In both complexes, L- is coordinated tridentately via the same donor atom set, while the fourth coordination site is occupied by a chloride ion. However, the complexes are not isostructural due to different types of non-covalent intermolecular interactions. These interactions were analyzed using Hirshfeld surfaces and two-dimensional fingerprint plots.
Synthesis, characterization and magnetic properties of dinuclear double end-on azido bridged Ni(II) complex with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent. DFT-BS ...explanation of ferromagnetic exchange coupling in dinuclear Ni(II) complex.
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A dinuclear double end-on azido bridged Ni(II) complex Ni2L2(μ-1,1-N3)2(N3)2 (1) with the condensation product of 2-quinolinecarboxaldehyde and trimethylammonium acetohydrazide chloride (Girard’s T reagent) (HLCl) has been synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, magnetic measurements and DFT studies. In complex 1 intra-dimer ferromagnetic coupling between Ni2+ ions (J=+12.0(2)cm−1) and inter-dimer antiferromagnetic interaction (δ=−0.8(3)cm−1) were observed. DFT-BS calculations provided explanation of ferromagnetic exchange coupling in complex 1.
In this work, Pt(II) complexes of previously synthesized steroidal thiosemicarbazones were synthesized and characterized. The ligands and their metal complexes were studied by analytical and ...spectroscopic data (elemental analysis, IR, 1D-NMR and 2D-NMR, HSQC, HMBC, NOESY, COSY), the analysis of which enabled complete 1H and 13C assignments of each compound including E and Z isomers. All the synthesized ligands and complexes were screened for their cytotoxic and antimicrobial activity. The results demonstrate that the new steroidal thiosemicarbazone complexes were significantly less cytotoxic than the corresponding steroidal thiosemicarbazones. In addition, complexes showed lower antimicrobial activity than the standard drugs, similar to the activity of the starting thiosemicarbazones.
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► Kinetics and mechanism of coordination polymer multi-step thermal degradation. ► Kinetic parameters determination by using isoconversion as well as non-isoconversion techniques. ► ...Discussion of mechanisms of complex degradation steps by application of artificial compensation effect and Vyazovkin's algorithm. ► Correlation of mechanism with structure of coordination polymer.
Multi-step thermal degradation of coordination polymer Cd(N-Boc-gly)2(H2O)2n in non-isothermal conditions was studied. The kinetic parameters were determined from the thermal decomposition data using the isoconversion and non-isoconversion techniques. It was shown that the coordination polymer is stable up to 60°C, when the multi-step process of thermal dehydration, followed by steps of degradation, starts. The kinetic triplet for the step of dehydration was established as f(α)=3/2(1−α)2/31−(1−α)1/3−1, Einv=170.4±6.4kJmol−1 and Zinv=2.6×1023. The established kinetic model, known as “D3 model”, was confirmed by application criteria defined by Màlek, Perez-Maqueda et al. as well as Master plot method. Dehydration step is followed by two steps of dehydrated coordination polymer degradation. On the base of the dependence of Arrhenius parameters (Ea and Z) on conversion degree (α), the mechanisms of degradation were discussed. In this way it was shown that second and third steps of degradation of coordination polymer are complex involving more than one elementary step. The second step corresponds to the loss of two C6H5CH2O– fragments in two parallel steps. The third step of degradation, ascribed to the loss of two –C(O)NHCH2– fragments, is complicated by changing kinetically to diffusion control.
Abstract
Two new Zn(II) complexes bearing tridentate hydrazone‐based ligands with NNO or NNS donor atoms were synthesised and characterised by elemental analysis, infrared (IR) and nuclear magnetic ...resonance (NMR) spectroscopies, and single crystal X‐ray diffraction methods. These complexes, together with four previously synthesised analogues, having hydrazone ligands with a NNO donor set of atoms, were successfully employed as catalysts in the ketone‐amine‐alkyne (KA
2
) coupling reaction, furnishing tetrasubstituted propargylamines, compounds with unique applications in organic chemistry. DFT calculations at the CAM‐B3LYP/TZP level of theory were performed to elucidate the electronic structure of the investigated Zn(II) complexes, excellently correlating the structure of the complexes to their catalytic reactivity.
The structural and biological study of a series of
d-metal complexes with
N-heteroaromatic selenosemicarbazone type ligands was performed. The square–planar geometry of Pt(II) complex (
1) with ...2-pyridinecarboxaldehyde selenosemicarbazone and octahedral geometry of Co(III) complex (
5) with 2-quinolinecarboxaldehyde selenosemicarbazone were established by X-ray analysis.
Five new complexes of Pt(II), Pd(II), Co(III) and Ni(II) with 2-pyridine(quinoline)carboxaldehyde selenosemicarbazones were synthesized and characterized. Crystal structures of Pt(II) complex with the pyridine derivative and Co(III) complex with the quinoline derivative were determined. In all complexes the ligands were coordinated through N
2Se donor atom set forming either square–planar (Pt, Pd) or octahedral (Co, Ni) geometry. All complexes showed biological activity.
Thermal behavior of Co(II), Cd(II), and Zn(II) complexes with
N
-benzyloxycarbonylglycinato ligand was investigated using the results of TG, DSC and DTG analysis obtained at different heating rates ...(2.5 to 30 °C min
−1
), from room temperature to about 900 °C. Mechanisms of complex degradation, as well as enthalpies of the degradation processes were determined. It is shown that thermal stability of investigated complexes correlates with their crystal structures, especially with the presence of crystallization and coordinated water molecules. The values of dehydration enthalpies are discussed and correlated with composition of the complexes. Kissinger’s, Ozawa’s, and Friedman’s isoconversion methods were used for the determination of kinetic parameters: the pre-exponential factor
A
and the apparent activation energy
E
a
. For all three complexes and all steps of degradation, the values of kinetics parameters obtained by Kissinger’s and Ozawa’s methods are in good agreement. The results obtained by Friedman’s method showed that some decomposition steps are simple and some others are complex ones.
The kinetics of multi-step thermal degradation of Co(II) complex with
N
-benzyloxycarbonyl glycinato ligand Co(
N
-Boc-gly)
2
(H
2
O)
4
·2H
2
O, in non-isothermal conditions was studied using ...isoconversional and non-isoconversional methods. The degradation of complex occurs in three well-separated steps involving the loss of water molecules in first step followed by two degradation steps of dehydrated complex. The dependence of Arrhenius parameters on conversion degree showed that all observed steps of thermal degradation are very complex, involving more than one elementary step, as can be expected for most solid-state heterogeneous reactions with solid reactants and solid and gaseous products. It was shown that step 1, corresponding to the dehydration, involves a series of competitive dehydration steps of differently bound water molecules complicated by diffusion. Second step involves two parallel reactions related to the loss of two identical C
6
H
5
CH
2
O– ligand fragments complicated by the presence of products in gaseous state. Further degradation in step 3 corresponds to complex process with a change in the limiting stage, in this case from the kinetic to the diffusion regime, connected with the presence of gaseous products diffusing through the solid product.
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