New Charge Transfer Complex between 4-Dimethylaminopyridine and DDQ: Synthesis, Spectroscopic Characterization, DNA Binding Analysis, and Density Functional Theory (DFT)/Time-Dependent DFT/Natural Transition Orbital Studies

Abstract

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.

Synthesis, Characterization, Antimicrobial, Density Functional Theory, and Molecular Docking Studies of Novel Mn(II), Fe(III), and Cr(III) Complexes Incorporating 4-(2-Hydroxyphenyl azo)-1-naphthol (Az)

“…Because they represent the physicochemical characteristics of a molecule (the electronic structure, vibrational spectra, dipole moment, polarizability, and other molecular properties), atomic charges play a significant role in molecules, , The atomic charges of the free ligand and its Cr­(III), Mn­(II), and Fe­(III) complexes in the current investigation were calculated using NBO analysis at the B3LYP/cc-pVQZ level of theory in ethanol as the solvent. The findings are presented in Figure and in the Supporting Information file.…”

Permittivity Threshold and Thermodynamics of Integer Charge-Transfer Complexation for an Organic Donor–Acceptor Pair

“…Benesi–Hildebrand analysis relies on a large excess of the acceptor or donor concentration, respectively, which results in a linearized expression from eq that relates CTC absorption, donor/acceptor concentration, and ε and K CT . This has been applied in several studies involving weak donor–acceptor CTCs but has been subject to debate regarding inaccuracy in determining formation constants. ,− An alternative approach is to use nonlinear regression to fit data directly to eq . − Although this approach does not place strict limits on the concentrations of individual species that should be used or make any fitting approximations, the following inequalities have been proposed to improve reliability for determinations of K CT and ε, assuming C D 0 > C A 0 : 0.1 C normalA 0 < C AD < 0.9 C normalA 0 .25em or .25em 0.1 / K < C normalD 0 < 0.9 / K 0.2 ≤ s ≤ 0.8 goodbreak0em1em⁣ s = C AD / C normalA 0 where s is the saturation fraction for the concentration of the complex with respect to the initial concentration of the limiting reagent and where it is suggested to analyze at least 75% of the saturation curve. , In essence, these recommendations ensure that there is curvature in a plot of Abs vs C D 0 , which makes it easier to simultaneously determine K CT and ε with greater accuracy. Finally, for improved accuracy in determining K CT and ε, it has been reported that 10–15 data points for a fit of Abs vs concentration should be included (which can be over a broad range of donor or acceptor concentrations) …”

Photoinduced Synthesis of Bis‐Sulfonyl γ‐Arylated Ketones via DMAP/DDQ‐Mediated Stereogenic Conjugated Addition of α‐Sulfonyl Chalcones with Benzylic Sulfones

“…Tigulla et al . used the electronic spectra to demonstrate the formation of the charge transfer DMAP/DDQ complex A [12b] between the DMAP radical cation and DDQ radical anion. A then initiates the formation of an α‐radical species (for 5 a ) to produce B via hydrogen abstraction.…”

“…Recently, Tigulla et al . developed density functional theory studies to investigate the charge transfer of a DMAP/DDQ complex [12b] . According to the association constant ( K CT ), molar absorptivity ( ϵ ), and spectroscopic parameters, stoichiometric quantities of DMAP and DDQ (1:1) could exhibit a high binding affinity to form a stable charge transfer complex.…”