作者: Johnson, Kristen N. ; Nandi, Goutam ; Kashi, Chiranjeevulu ; Sireesha, Pedaballi ; Hipps, K. W. ; Chilukuri, Bhaskar ; Mazur, Ursula ; Gurdumov, Kirill

Understanding the interactions between mols. on surfaces is crucial for advancing technologies in sensing, catalysis, and energy harvesting.In this study, we explore the complex surface chem. resulting from the interaction of Co(II)octaethylporphyrin (CoOEP) and iodine, I₂, both in solution and at the phenyloctane/highly oriented pyrolytic graphite (HOPG) interface.In pursuit of this goal, we report results from electrochem., NMR and UV-vis spectroscopy, X-ray crystallog., scanning tunneling microscopy (STM), and d. functional theory (DFT).Both spectroscopic methods of anal. confirmed that at and above the stoichiometric ratio of one CoOEP to one I₂ the reaction product was metal-centered Co^III(OEP)I.X-ray crystallog. verified that a single iodine is bonded to each cobalt ion in the triclinic P1 system.The surface chem. of CoOEP and I₂ is complicated and remarkably dependent on the iodine concentrationSTM images of CoOEP and I₂ in phenyloctane on HOPG at low halogen concentrations (1:<2 Co/I ratios) presented random individual Co(OEP)I mols. weakly adsorbed onto a hexagonal (HEX) CoOEP monolayer.Images of 1:≥2 Co/I ratio solutions showed phase-segregated HEX CoOEP and pseudorectangular (REC) Co(OEP)I incorporating one solvent mol. per Co(OEP)I.The REC structure formed in long parallel rows with the number of rows increasing with increasing solution I₂.In this case, the presence of CoOEP on the surface was attributed to the spontaneous reduction of Co(OEP)I by the graphite substrate.DFT calculations indicate that the REC Co(OEP)I:PhO form is energetically more stable than the HEX form of Co(OEP)I on HOPG.Exptl. STM images and DFT calculated adsorption energies support our interpretation of the observed structures.

2025-03-10·Inorganic Chemistry

Remarkable Increase in the Rate of Trans–Cis Photoisomerization of Os(II)-Terpyridine Complexes via Oxidation and Reduction

Article

作者: Maity, Dinesh ; Baitalik, Sujoy ; Ganguly, Tanusree ; Abedin, Tuhin

Luminescent homoleptic Os(II)-terpyridine complexes comprising stilbene-appended naphthalene, anthracene, and pyrene motifs are designed in this work, and their photophysical, electrochemical, and photoisomerization behaviors are extensively investigated. All complexes exhibit intense spin-allowed singlet metal-to-ligand charge transfer (¹MLCT) bands in the visible (496-500 nm) and weaker spin-forbidden singlet-to-triplet ³MLCT transitions in the 600-700 nm range. They display moderate emission at room temperature with lifetimes in the range of 84.5-112.5 ns. Electrochemical studies reveal a reversible Os²⁺/Os³⁺ oxidation couple within 0.93-0.96 V, alongside multiple reversible or quasi-reversible reduction peaks associated with terpyridine units in between -1.10 and -1.85 V. The stilbene motifs facilitate reversible trans-cis photoisomerization under alternative treatment with visible and UV light, enabling the complexes to function as photomolecular switches in the near-infrared domain. Interestingly, a remarkable increase in the rate of photoisomerization has been achieved via oxidation as well as reduction of the complexes, which, in turn, induces multistep switching involving reversible oxidation-reduction and trans-cis isomerization. Computational investigations are also conducted on all three conformations {trans-trans (t-t), trans-cis (t-c), and cis-cis (c-c)} of the complexes to gain insight into their electronic structures and for accurate assignment of their absorption and emission spectral bands.

2025-03-01·Physica Scripta

Soliton, breather and double-layer structures formation of ion acoustic waves in weakly magnetized non-thermal plasmas

作者: Biswas, Akash ; Majee, Debakinandan

AbstractThe dynamics of the obliquely propagating weakly nonlinear ion acoustic waves are investigated in a collisionless weakly magnetized plasmas in the context of the Cairns distributed non-thermal electrons. A three-dimensional Korteweg de-Vries (KdV) equation, colloquially known as the Laedke-Spatschek (LS) equation, has been shown to describe the dynamics of the nonlinear wave. Analytical solutions depending on the physical parameters predict solitary, periodic and breather like structures. Interestingly, at a critical value of the non-thermal parameter, the dynamics is found to be governed by a modified LS equation which is conditionally Painlevé integrable. Exact analytical solution with the help of Bäcklund transformation reveals that the modified LS equation supports a double-layer, sawtooth-like periodic and breather-like structures. The results are discussed in the context of astrophysical observations in the auroral region.

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