UV–vis electronic
absorption spectroscopy was used to investigate
the new molecular charge transfer complex (CTC) interaction between
electron donor
O
-phenylenediamine (OPD) and electron
acceptor 2,3-dichloro-5,6-dicyano-
p
-benzoquinone
(DDQ). The CTC solution state analysis was carried out by two different
polarities. The stoichiometry of the prepared CTC was determined by
using Job’s, photometric, and conductometric titration methods
and was detemined to be 1:1 in both solvents (at 298 K). The formation
constant and molar extinction coefficient were determined by applying
the modified (1:1) Benesi–Hildebrand equation. The thermodynamic
parameter Δ
G
° result indicated that the
charge transfer reaction was spontaneous.The stability of the synthesized
CTC was evaluated by using different spectroscopic parameters like
the energy, ionization potential, oscillator strength, resonance energy,
dissociation energy, and transition dipole moment. The synthesized
solid CTC was characterized by using different analytical methods,
including elemental analysis, Fourier transform infrared, nuclear
magnetic resonance, TGA-DTA, and powder X-ray diffraction. The biological
evolution of the charge transfer (CT) complex was studied by using
DNA binding and antibacterial analysis. The CT complex binding with
calf thymus DNA through an intercalative mode was observed from UV–vis
spectral study. The CT complex produced a good binding constant value
(6.0 × 10
5
L.mol
–1
). The antibacterial
activity of the CT complex shows notable activity compared to the
standard drug, tetracycline. These results reveal that the CT complex
may in future be used as a bioactive drug. The hypothetical DFT estimations
of the CT complex supported the experimental studies.
A combined experimental
and theoretical study of the electron donor
4-dimethylaminopyridine (4-DMAP) with the electron acceptor 2, 3-dichloro-5,
6-dicyano-
p
-benzoquinone (DDQ) has been made in acetonitrile
(ACN) and methanol (MeOH) media at room temperature. The stoichiometry
proportion of the charge transfer (CT) complex was determined using
Job’s and photometric titration methods and found to be 1:1.
The association constant (
K
CT
), molar
absorptivity (ε), and spectroscopic physical parameters were
used to know the stability of the CT complex. The CT complex shows
maximum stability in a high-polar solvent (ACN) compared to a less-polar
solvent (MeOH). The prepared complex was characterized by Fourier
transform infrared, NMR, powder X-ray diffraction, and scanning electron
microscopy–energy-dispersive X-ray analysis. The nature of
DNA binding ability of the complex was probed using UV–visible
spectroscopy, and the binding mode of the CT complex is intercalative.
The intrinsic binding constant (
K
b
) value
is 1.8 × 10
6
M
–1
. It reveals a primary
indication for developing a pharmaceutical drug in the future due
to its high binding affinity with the CT complex. The theoretical
study was carried out by density functional theory (DFT), and the
basis set is wB97XD/6-31G(d,p), with gas-phase and PCM analysis, which
supports experimental results. Natural atomic charges, state dipole
moments, electron density difference maps, reactivity parameters,
and FMO surfaces were also evaluated. The MEP maps indicate the electrophilic
nature of DDQ and the nucleophilic nature of 4-DMAP. The electronic spectrum computed using time-dependent
DFT (TD-DFT) via a polarizable continuum salvation approach, PCM/TD-DFT,
along with natural transition orbital analysis is fully correlated
with the experimental outcomes.
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