M.S.S. Adam, et al.
InorganicaChimicaActa499(2020)119212
thiourea derivatives is their toxicity [13]. Therefore, the exploration of
stringent problem; it has attracted enormous attention [14,15].
Organic molecules that contain heteroatoms such as N, S, O and P,
polar groups and π-electron have been mentioned to exhibit good
protection capacity. These compounds could be adsorbed on the surface
of the electrode forming a bond between π-electron cloud and metal
and/or the lone pair electrons of heteroatoms, thereby minimizing the
corrosion rate in the aggressive environments [16,17].
a 10 mm silica cells in a thermostatted cell holder in order to evaluate the
electronic absorption transitions of H2PHL, NiPHL and VOPHL and refer-
enced in the given solvent, water. Shimadzu FTIR-8101 Fourier Transform
Infrared spectrophotometer was involved to measure the stretching vi-
brational diagnostic bands of the studied compounds in the region from
4000 to 400 cm−1. Thermogravimetric analysis was accomplished by
Shimadzu TGA-50H thermal analyzer with flow of an inert carrier gas,
nitrogen gas, with flow rate 20 cm3 min−1 and heating rate 10 °C min−1
from 30 to 400 °C. Mass spectra were measured in m/z using waters Qtof
Micro YA263 mass spectrometer for the current complexes. A Jenway
conductivity meter model 4320 was applied to measure conductivities of
H2PHL, NiPHL and VOPHL in DMSO and DMF using an epoxy bodied
conductivity cell (consisting of two electrodes, shiny) at 25 °C (the tem-
perature was held by using a HAAKE model F3-k ultrathermostat
tives) to form stable packed neatly pincer chelates with metal ion
provides more inhibiting compound classes, i.e. dihydrazone ligands
and their metal-complexes. The complexation atmosphere of multi-
donating ligands with various valent metals ions, e.g. dihydrazone,
could play an essential action in the electro-catalytic reduction pro-
cesses with redox behavior. Some recent studies referred to that, the
metal-complexes show higher inhibition capacity than their corre-
with
0.2 °C). The cell constant calibration was carried out from 0.01 to
19.99. Magnetic susceptibility of the studied pincer chelates were mea-
sured by Gouy’s balance. The calibration was achieved by Pascal's contents
and Hg[Co(SCN)4] in order to get the diamagnetic correction. Values of
metal complexes have many utilities in analytical and medicinal chem-
istry [19,20]. Their metal pincer chelates were explored as high reactive
homogeneous/heterogeneous catalytic oxidation systems [20–22]. Con-
sequently, many fundamental researches highlighted on metal-ar-
oyldihydrazones as catalysts for various organic processes [21,22].
Investigation of oxide-metal pincer chelates, as homogeneous cata-
lysts, in the cross-coupling systems, e.g. Suzuki-Miyaura reactions need
more progress in literatures [23]. On the other hand, Ni-species are well
Ni-pincer chelates display an effective role as homogeneous catalysts
for cross-coupling processes of different organometallics and organo-
halides [26]. Oppositely, VIVO-species exhibited excellent catalytic
prediction of any chemical progresses. It is highly applicable for cor-
rosion protection systems [36–39]. DFT calculations were improved to
the studying materials, as well as their catalytic proposes [31,35].
most polar and less polar organic solvents [40]. Hence, incorporating of
polar p-sodium sulfonate group to the organic framework develops its
solubility in water and is of interest substantially in many organic
catalytic systems [32,41]. Here, it motivates us to synthesize aroyl di-
The different aspects ligand reacted with low and high velants of Ni2+
and VO2+ ions to form high stable M−complexes. The complexes are
applied as homogeneous catalysts in the oxidation of 1,2-cyclohexene
and Suzuki–Miyaura cross-coupling under substantial conditions,
moreover, as CO2-corrosive inhibiting reagents.
pH were determined using Metrohm 695 pH/ion meter to
0.005 units
0.2 °C.
at 25 °C in an ultrathermostat (HAAKE model F3-k) error range
A Thermo Scientific 9100 machine was used to estimate the melting or
decomposition point of the studied compounds.
2.2. Preparation of H2PHL (N,N-bis(4-sodium sulfonate-2-
hydroxybenzylidene)terephthalohydrazide)
Terephthaloldihydrazide is the permanent reagent to synthesize the
different aspects of ligand H2PHL, which was prepared with respect to
the reported method [4]. The preparation of terephthaloyl salicylidene
dihydrazone and its derivatives carried out by a common condensation
of salicylaldehyde derivatives with benzene-1,4-dicarbohydrazide [42].
laldehyde in 60 mL of H2O was added leisurely to an aqueous media of
1.94 g of trerphethalyldihydrazide (10.0 mmol, 60 mL). The mixture of
the components was kept with reflux for 3 h under stirring (100 °C). The
reaction completion was controlled by TLC to give pale yellow coloring
of the required ligand. The mixed ethanol/water solvents were taken
away by slow evaporation with a good amount of the rest, which col-
lected and washed with cooled ethanol. Then, it was dried in an oven
and it was quite pure for further workup.
1H NMR of diketone form (DMSO‑d6, 400.1 MHz): δ 6.89 (d,
3J = 8.3 Hz, 2H), 7.58 (d, 3J = 8.0 Hz, 2H), 7.85 (s, 2H), 8.11 (s, 4H),
8.72 (s, 2H), 11.28 (br s, 2H, NH) and 12.20 ppm (s, 2H, eCH = Ne).
Distinguished 1H NMR of the tautomers (dienole and keto-enole forms):
6.79 (d, 3J = 8.1 Hz), 7.65 (d, 3J = 7.9 Hz), 7.97 (s), 7.99 (d,
3J = 8.1 Hz, 2H) and 9.00 ppm (s).
13C NMR (100.6 MHz, DMSO‑d6, dept-135): δ 116.06 (CH), 118.08
(Cq), 127.19 (CH), 128.03 (CH), 128.32 (CH), 129.51 (CH), 140.97
(Cq), 148.97 (CH), 158.05 (Cq) and 162.64 ppm (CH, CH = N). (more
details of NMR spectra are shown in the Supplementary Materials in
Figs. S1-S3).
2. Experimental
2.3. Metal-complexes preparation (NiPHL and VOPHL)
2.1. Reagents and methodology
In water (50 mL), H2PHL (3.03 g, 5.0 mmol) was poured gently to an
aqueous atmosphere, 60 mL, of vanadyl acetylacetonate, VO(acac)2
(from Acros, 99%), or nickel acetate tetrahydrate or Ni
(OOCCH3)2·4H2O (from Merck, 98%) (2.65 g or 2.48 g, 10.0 mmol, re-
spectively). The resulted mixed ethanol/water solutions were warmed
up to 80 °C and kept under stirring within 3 h. The color of the reaction
contents was turned gradually into the corresponding coloring of the
desired dinuclear chelating complex. After cooling down, the solvents
were extracted in vacuum and the rest was collected and washed by
cooled ethanol and dried in vacuum. The crystalline shape of the
complexes was obtained by recrystallization in 30 mL H2O and then
dried in oven.
Chemical compounds and reagents are marketably presented from
Merck, Sigma-Aldrich and Acros. They applied in all chemical proposes
without additional treatments. A GMBH VarioEl model V2.3 Carbon,
Hydrogen and Nitrogen apparatus was operated to evaluate the ratio
percentages of Carbon, Hydrogen and Nitrogen atoms in their compounds.
NMR spectroscopy was estimated by a Bruker ARX400 multinuclear NMR
spectrometer at for hydrogen nuclei at frequencies 400.1 and for carbon
nuclei at frequencies = 100.6 MHz at 25 °C. Values of chemical shifts, δ, of
1H and 13C nuclei and the coupling constant values between H nuclei, JHH
,
are determined and given in ppm, respectively, for the ligand H2PHL.
Using JASCO machine as UV–Vis. spectrophotometer (model V-570) with
2