<p>Charge Transfer Complex of Neostigmine with 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone: Synthesis, Spectroscopic Characterization, Antimicrobial Activity, and Theoretical Study</p>

Abstract

Background: Electron donor-acceptor interactions are important molecular reactions for the activity of pharmacological compounds. The aim of the study is to develop a charge transfer (CT) complex: synthesis, characterization, antimicrobial activity, and theoretical study. Method and Results: A solid CT complex of neostigmine (NSG) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was synthesized and characterized by infrared spectra, NMR, and UV-visible spectroscopy. The results confirm the formation of a CT complex. The stability of the CT complex between NSG and DDQ in acetonitrile was determined in solution via spectrophotometric measurement, ie, by calculating the formation constant, molar extinction coefficient, and different spectroscopic parameters. The stoichiometry of the formed NSG-DDQ complex was determined using Job's method. The absorption band of the NSG-DDQ complex can be used for the quantification of NSG. Conclusion: The DFT geometry optimization of NSG, DDQ, and the CT complex and the UV comparative study of both theoretical and experimental structures are presented. The experimental results confirm the charge transfer structure. The bacterial study shows that the NSG-DDQ complex has good antibacterial activity against both Gram-positive and Gramnegative bacteria as well as antifungal activity against Candida albicans.

Charge Transfer Complexes of Ketotifen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8-Tetracyanoquodimethane: Spectroscopic Characterization Studies

“…The ε AD and K C of the formed complexes were found to be (1.1 × 10 3 and 1.3 × 10 4 L mol −1 cm −1 ) for KT-DDQ and (0.2 × 10 3 and 2.56 × 10 3 L mol −1 cm −1 ) for KT-TCNQ. The high value of the association constant confirms the stability of the CT complexes, which is in line with the published literature on the association constants [ 13 , 14 ]. The stability of the formed 1:1 complex was higher with KT-TCNQ than with KT-DDQ.…”

“…In this work, the reaction of KT with DDQ or TCNQ to produce CT complexes was investigated. Previously, the concepts underlying the formation of CT complexes between electron donors and acceptors have been explored in detail [ 13 , 14 ]. The major chromogen with DDQ has a maximum absorbance in acetonitrile of 485 nm in the visible region.…”

“…CT complexes are also applied in biological systems, such as DNA binding [ 10 ] and anti-microbial, anti-fungal, and anti-tumor mechanisms [ 11 , 12 ]. CT interactions are associated with the formation of colored complexes, which absorb radiation in the visible regions and can be used for the quantitative estimation of drugs [ 13 , 14 ].…”

“…Density function theory (DFT) was used to characterize the molecules in the complexes based on their electronic structures and physicochemical properties, such as charge distribution, molecular electrostatic potential, energy variance among the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and the electronic chemical potential analysis of the CT complexes. DFT has previously been carried out to describe the physiochemical properties of various CT complexes [ 13 , 14 ] and is one of the most useful quantum calculation methods available, due to its reliability, low cost, and speed.…”

Charge Transfer Complex betweenO-Phenylenediamine and 2, 3-Dichloro-5, 6-Dicyano-1, 4-Benzoquinone: Synthesis, Spectrophotometric, Characterization, Computational Analysis, and its Biological Applications

“…The energy ( W ) of the dissociation parameter for the CTC indicates the nature of the [(OPD)(DDQ)] complex, and it was estimated with the help of energy ( E CT ), ionization energy referring to the OPD ( I D ), and electron affinity ( E A ) referring to the DDQ molecule 52 ( Table 1 ). …”