Assignment of the electronic transition of phenothiazine radical cation in the visible region– a resonance Raman spectroscopy and theoretical calculation investigation

DFT and MD investigations of the biomolecules of phenothiazine derivatives: interactions with gold and water molecules and investigations in search of effective drug for SARS-CoV-2

Theoretical analyses of two phenothiazine derivatives, 10-[3-(dimethylamino)-2-methylpropyl]phenothiazine-2-carbonitrile (CYM) and 2-[4-[3-(2-chlorophenothiazin-10-yl)propyl]piperazin-1-yl]ethanol (PAZ) are reported using density functional theory (DFT) and molecular dynamics (MD) simulations. Spectroscopic studies, different electronic and chemical parameters are predicted. Red and yellow in electrostatic potential plot is in rings and oxygen atom in PAZ and C≡N and rings in CYM are sensitive to nucleophilic attacks. The blue in hydrogen atoms refer to electrophilic attack in both PAZ and CYM. Stability of the protein-ligand complex formed with these derivatives and angiotensin-converting enzyme 2 (ACE2) was investigated using MD simulation. Radius of gyration of C-alpha atom of 6VW1 displayed the conformational convergence toward a compact structure leading to stable 6VW1-ligand complex which are also in agreement with root mean square fluctuation (RMSF) values. Localized area predicts reactive sites for Au and H₂O molecules interaction with these compounds for further practical applications. Charge density is localized on both molecules and also tries to move toward Au-Au dimer and water molecule and such they are expected to contribute to the sensing performance. Communicated by Ramaswamy H. Sarma.

Force-Induced Turn-On Persistent Room-Temperature Phosphorescence in Purely Organic Luminogen

Research of purely organic room-temperature phosphorescence (RTP) materials has been a hot topic, especially for those with stimulus response character. Herein, an abnormal stimulus-responsive RTP effect is reported, in which, purely organic luminogen of Czs-ph-3F shows turn-on persistent phosphorescence under grinding. Careful analyses of experimental results, coupled with the theoretical calculations, show that the transition of molecular conformation from quasi-axial to quasi-equatorial of the phenothiazine group should be mainly responsible for this exciting result. Furthermore, the applications of stylus printing and thermal printing are both successfully realized, based on the unique RTP effect of Czs-ph-3F.

Theoretical study on the sensing mechanism of a coumarin-based fluorescent probe for biological thiols

The sensing mechanism of a reported fluorescence probe for cysteine, homocysteine and glutathione (Yin et al., 2018) has been investigated by time-dependent density functional theory. Experimental absorption and emission spectra of the probe before and after thiol addition were reproduced well by theoretical calculations, which validated the rationality of the method. Optimized geometries showed that the probe molecule had distinctly different geometries in its ground and excited states. It corresponded to the photoisomerization process and explained the weak fluorescence of the probe molecule. Moreover, by the potential energy curve scan, photoisomerization was further confirmed to be a spontaneous process with a barrier that barely existed. Frontier orbital analysis indicated that this photoinduced isomerization of the probe molecule derived from the antibonding character for lowest unoccupied molecular orbital at its CC double bond. In contrast, probe-thiol complexes exhibited similar geometries in their ground and excited states, which was responsible for the strong fluorescence of the probe with thiols. Due to distinct excited-processes, the probe can be used to sense thiols by monitoring the fluorescent change.