The synthesis and characterization of a dinuclear bis(thiosemicarbazone) cobalt complex Co2L2(NCS)2 is reported. This complex exhibits significant catalytic activity for hydrogen production in DMF by ...using triethylammonium (Et3NHBF4) as the proton source. Cyclic voltammetry data allowed a maximum turnover frequency of 130 s−1 for 1 m proton concentration to be determined. The catalytic nature of the process and the production of dihydrogen were confirmed by gas analysis during controlled potential electrolysis experiments. Quantum chemical calculations show that the complex displays a ligand‐assisted metal‐centered reactivity and supports a catalytic mechanism involving ligand‐based reduction and protonation steps followed by metal‐centered processes.
Center of attraction: A dinuclear cobalt complex based on a thiosemicarbazone ligand is an efficient electrocatalyst for hydrogen evolution reactions. The catalytic mechanism involves ligand‐based reductions alternating with protonation steps consistent with an unusual ligand‐assisted metal‐centered reactivity (see scheme).
We report herein the synthesis and characterization of a new mononuclear nickel complex based on a thiosemicarbazone ligand that exhibits an electrocatalytic behavior for H2 evolution in DMF using ...trifluoroacetic acid (TFA) as the proton source. Catalysis is observed at quite small overpotential values and a maximum turnover frequency (TOFmax) of 3080 s−1 was extrapolated for 1 m proton concentration using the foot‐of‐the wave analysis of cyclic voltammetry data. Gas analysis during controlled potential electrolysis experiments confirmed the catalytic nature of the process and production of dihydrogen with 80 % faradaic yield. Quantum chemical calculations indicate that the catalytic mechanism involves first ligand‐based reduction and protonation steps followed by metal‐centered processes.
Nickel‐centered: A mononuclear nickel complex based on a thiosemicarbazone ligand ranks among the best molecular H2‐evolving electrocatalysts in DMF in the catalytic Tafel plot. The catalytic mechanism involves ligand‐based reduction and protonation steps followed by metal‐centered processes.
A series of water-soluble sodium salts of 3-formyl-4-hydroxybenzenesulfonic acid thiosemicarbazones (or sodium 5-sulfonate-salicylaldehyde thiosemicarbazones) containing different substituents at the ...terminal nitrogen atom (H, Me, Et, Ph) and their copper(ii) complexes have been prepared and characterised by elemental analysis, spectroscopic techniques (IR, UV-vis,
H NMR), ESI mass spectrometry, X-ray crystallography and cyclic voltammetry. The proligands and their copper(ii) complexes exhibit moderate water solubility and good stability in aqueous environment, determined by investigating their proton dissociation and complex formation equilibria. The copper(ii) complexes showed moderate anticancer activity in established human cancer cell lines, while the proligands were devoid of cytotoxicity. The anticancer activity of the copper(ii) complexes correlates with their ability to induce ROS accumulation in cells, consistent with their redox potentials within the biological window, triggering the activation of antioxidation defense mechanisms in response to the ROS insult. These studies pave the way for the investigation of ROS-inducing copper(ii) complexes as prospective antiproliferative agents in cancer chemotherapy.
Simple reaction procedure, boiling of an equimolar mixture of Re(Cl)(CO)
3
(dppv) (dppv—
cis
-1,2-bis(diphenylphosphino)-ethene), 2-(2-pyridyl)benzimidazole (pbi), and TlClO
4
in
o
-dichlorobenzene ...solution, leads to two, chromatographically separable, isomers of Re(CO)
2
(dppv)(pbi) complex. The obtained species, the yellow-emissive
OC
-6–54 and the orange-emissive
OC
-6–53 isomers, have been identified using FT-IR,
1
H NMR, and
31
P NMR spectroscopy and their structures confirmed by means of X-ray investigations. According to obtained crystallography results, the investigated isomers differ mainly in the arrangement of the 2-(2-pyridyl)benzimidazole anion in their structures. Diverse arrangement of the dppv and pbi ligand around the central
cis
-Re(CO)
2
+
core results in well-pronounced changes in luminescence properties of the studied luminophores. According to results from performed DFT and TDA-DFT computations, the
OC
-6–54 isomer emission occurs from the intra-ligand excitation localized mainly within the pbi ligand. In contrary to that, the
OC
-6–53 isomer emission indicates some metal-to-ligand charge-transfer character associated with the charge transfer from the Re(CO)
2
(dppv)
+
fragment to the pbi ligand. Moreover, both isomers exhibit different character of their emission decays, mono-exponential and bi-exponential for the
OC
-6–54 and
OC
-6–53 ones, respectively. In the view of obtained DFT/TDA-DFT results, this has been explained by the presence of an additional excited dark state, operative only in the case of the
OC
-6–53 isomer and associated with the charge transfer from the Re(CO)
2
(pbi) fragment to the dppv ligand.
Scalarane sesterterpenoids emerged as interesting bioactive natural products which were isolated extensively from marine sponges and shell-less mollusks. Some representatives were also reported ...recently from superior plants. Many scalarane sesterterpenoids displayed a wide spectrum of valuable properties, such as antifeedant, antimicrobial, antifungal, antitubercular, antitumor, anti-HIV properties, cytotoxicity and stimulation of nerve growth factor synthesis, as well as anti-inflammatory activity. Due to their important biological properties, many efforts have been undertaken towards the chemical synthesis of natural scalaranes. The main synthetic challenges are connected to their complex polycyclic framework, chiral centers and different functional groups, in particular the oxygenated functional groups at the C-12 position, which are prerequisites of the biological activity of many investigated scalaranes. The current work addresses this problem and the synthesis of 17-oxo-20-norscalaran-12α,19-
-lactone is described. It was performed via the 12α-hydroxy-
-isocopal-13(14)-en-15-al obtained from (-)-sclareol as an accessible starting material. The tetracyclic lactone framework was built following an addition strategy, which includes the intramolecular Michael addition of a diterpenic acetoacetic ester and an intramolecular aldol condensation reaction as key synthetic steps. The structure and stereochemistry of the target compound have been proven by X-Ray diffraction method.
In terrestrial plants, strigolactones act as multifunctional endo- and exo-signals. On microalgae, the strigolactones determine akin effects: induce symbiosis formation with fungi and bacteria and ...enhance photosynthesis efficiency and accumulation of biomass. This work aims to synthesize and identify strigolactone mimics that promote photosynthesis and biomass accumulation in microalgae with biotechnological potential. Novel strigolactone mimics easily accessible in significant amounts were prepared and fully characterized. The first two novel compounds contain 3,5-disubstituted aryloxy moieties connected to the bioactive furan-2-one ring. In the second group of compounds, a benzothiazole ring is connected directly through the cyclic nitrogen atom to the bioactive furan-2-one ring. The novel strigolactone mimics were tested on Chlorella sorokiniana NIVA-CHL 176. All tested strigolactones increased the accumulation of chlorophyll b in microalgae biomass. The SL-F3 mimic, 3-(4-methyl-5-oxo-2,5-dihydrofuran-2-yl)-3H-benzothiazol-2-one (7), proved the most efficient. This compound, applied at a concentration of 10−7 M, determined a significant biomass accumulation, higher by more than 15% compared to untreated control, and improved the quantum yield efficiency of photosystem II. SL-F2 mimic, 5-(3,5-dibromophenoxy)-3-methyl-5H-furan-2-one (4), applied at a concentration of 10−9 M, improved protein production and slightly stimulated biomass accumulation. Potential utilization of the new strigolactone mimics as microalgae biostimulants is discussed.
A series of neutral mononuclear lanthanide complexes Ln(HL)2(NO3)3 (Ln = La, Ce, Nd, Eu, Gd, Dy, Ho) with rigid bidentate ligand, HL (4′-(1H-imidazol-1-yl)biphenyl-4-carboxylic acid) were synthesized ...under solvothermal conditions. The coordination compounds have been characterized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis. According to X-ray diffraction, all the complexes are a series of isostructural compounds crystallized in the P2/n monoclinic space group. Additionally, solid-state luminescence measurements of all complexes show that Eu(HL)2(NO3)3 complex displays the characteristic emission peaks of Eu(III) ion at 593, 597, 615, and 651 nm.
The asymmetric units of the isostructural compounds (1,4,8,11-tetraazacyclotetradecane-κ
4
N
)nickel(II) tetraiodidocadmate(II), Ni(C
10
H
24
N
4
)CdI
4
(
I
), and triiodido-1κ
3
I
...-μ-iodido-(1,4,8,11-tetraazacyclotetradecane-2κ
4
N
)cadmium(II)zinc(II), CdZnI
4
(C
10
H
24
N
4
) (
II
) (C
10
H
24
N
4
= 1,4,8,11-tetraazacyclotetradecane, cyclam,
L
), consist of the centrosymmetric macrocyclic cation
M
(
L
)
2+
M
= Ni
II
or Zn
II
with the metal ion lying on a twofold screw axis, and the tetraiodocadmate anion CdI
4
2−
located on the mirror plane. In
I
, the anion acts as an uncoordinated counter-ion while in
II
it is bound to the Zn
II
atom
via
one of the iodide atoms, thus forming an electroneutral heterobimetallic complex Zn(
L
)(CdI
4
). The Ni
II
and Zn
II
ions are coordinated in a square-planar manner by the four secondary N atoms of the macrocyclic ligand
L
, which adopts the most energetically stable
trans
-III conformation. The CdI
4
2−
anions in
I
and
II
are structurally very similar and represent slightly deformed tetrahedrons with average Cd—I bond lengths and I—Cd—I angles of
ca
2.79 Å and 109.6°, respectively. The supramolecular organization of the complexes under consideration in the crystals is very similar and is determined by the hydrogen-bonding interactions between the secondary amino groups of the ligand
L
in the
M
(
L
)
2+
cations and iodide atoms of the CdI
4
2−
anion. In particular, the alternating cations and anions form chains running along the
b-
axis direction that are arranged into di-periodic sheets oriented parallel to the (101) and (\overline{1}01) planes. Because both kinds of sheets are built from the same cations and anions, this feature provides the three-dimensional coherence of the crystals of
I
and
II
.
3-Arylsydnones bearing fluorine and bromine atoms on the benzene ring were synthesized from N-nitroso-2-fluorophenylglycines and characterized by NMR spectroscopy. These were employed further in ...synthesis of the corresponding 1-(2-fluorophenyl)pyrazoles by 1,3-dipolar cycloaddition reaction with dimethyl acetylenedicarboxylate (DMAD) as activated dipolarophile. The sydnones as reaction intermediates were characterized by single crystal X-ray diffraction analysis showing interesting features such as halogen bonding as an important interaction in modeling the crystal structure.
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