Synthesis and crystal structure of bis(O-methyl hydrogenato carbonodithioate)-Pb(II): structural,optical and photocatalytic studies of PbS nanoparticles from the complex

Abstract

Lead(II) methyl xanthate [Pb(S₂COMe)₂] was synthesized and characterized by single crystal X-ray crystallography. The molecular structure showed a distorted tetrahedral geometry around Pb(II) with each monomeric unit linked with another through Pb···S interactions. The compound was used to prepare hexadecylamine capped PbS (HDA-PbS) and oleylamine capped PbS (OLA-PbS) nanoparticles. The PbS nanoparticles were indexed to the cubic PbS crystalline phase with particle sizes of 4.5 – 34.5?nm. The estimated optical bandgaps obtained from the tauc’s plots were 3.47 and 3.30?eV for HDA-PbS and OLA-PbS, respectively, which are blue shifted in comparison to bulk PbS. The photodegradation of methylene blue using PbS as photocatalyst shows that HDA-PbS have the best degradation efficiency of 77.70% after 240?min.     

Atomistic simulation reveals structural mechanisms underlying D614G spike glycoprotein-enhanced fitness in SARS-COV-2

D614G spike glycoprotein (sgp) mutation in rapidly spreading severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) is associated with enhanced fitness and higher transmissibility in new cases of COVID-19 but the underlying mechanism is unknown. Here, using atomistic simulation, a plausible mechanism has been delineated. In G614 sgp but not wild type, increased D(G)614-T859 Cα-distance within 65 ns is interpreted as S1/S2 protomer dissociation. Overall, ACE2-binding, post-fusion core, open-state and sub-optimal antibody-binding conformations were preferentially sampled by the G614 mutant, but not wild type. Furthermore, in the wild type, only one of the three sgp chains has optimal communication route between residue 614 and the receptor-binding domain (RBD); whereas, two of the three chains communicated directly in G614 mutant. These data provide evidence that D614G sgp mutant is more available for receptor binding, cellular invasion and reduced antibody interaction; thus, providing framework for enhanced fitness and higher transmissibility in D614G SARS-COV-2 mutant.     

ZnTBPPc光物理化学性质的溶剂化效应

The solvent viscosity dependence of the photophysical and photochemical properties of tetra(tert-butylphenoxy)phthalocyaninato zinc(II) (ZnTBPPc) is presented. The fluorescence quantum yields (ΦF) and Stern-Volmer′s constant (KSV) for ZnTBPPc fluorescence quenching by benzoquinone in all the solutions followed a semi-empirical law that depends only on the solvent viscosity. ΦF values vary between 0.08 in tetrahydrofuran (THF) and 0.14 in dimethylsulphoxide (DMSO). Triplet quantum yields (ΦT) and lifetimes (...     

Ruthenium complexes with lumazine derivatives: structural,electrochemical, computational and radical scavenging studies

In this research study, the formation and characterization of new ruthenium(II) and (III) complexes encompassing multidentate ligands derived from 6-acetyl-1,3,7-trimethyllumazine (almz) are reported. The 1:1 molar coordination reactions of trans-[RuCl₂(PPh₃)₃] with N-1-[1,3,7-trimethyllumazine]benzohydride (bzlmz) and 6-(N-methyloxime)-1,3,7-trimethyllumazine (ohlmz) formed a diamagnetic ruthenium(II) complex, cis-[RuCl₂(bzlmz)(PPh₃)] (1), and paramagnetic complex, cis-[Ru^IIICl₂(olmz)(PPh₃)] (2) [Holmz = 6-(N-hydroxy-N′-methylamino)-1,3,7-trimethyllumazine], respectively. These ruthenium complexes were characterized via physico-chemical and spectroscopic methods. Structural elucidations of the metal complexes were confirmed using single crystal X-ray analysis. The redox properties of the metal complexes were investigated via cyclic voltammetry. Electron spin resonance spectroscopy confirmed the presence of a paramagnetic metal centre in 2. The radical scavenging activities of the metal complexes were explored towards the DPPH and NO radicals. Quantum calculations at the density functional theory level provided insight into the interpretation of the IR and UV–Vis experimental spectra of 1.     

Coordination of di- and triimine ligands at ruthenium(II) and ruthenium(III) centers: structural,electrochemical and radical scavenging studies

Herein, we explore the coordination of di- and triimine chelators at ruthenium(II) and ruthenium(III) centers. The reactions of 2,6-bis-((4-tetrahydropyranimino)methyl)pyridine (thppy), N¹,N²-bis((3-chromone)methylene)benzene-1,2-diamine (chb), and tris-((1H-pyrrol-2-ylmethylene)ethane)amine (H₃pym) with trans-[Ru^IICl₂(PPh₃)₃] afforded the diamagnetic ruthenium(II) complex cis-[RuCl₂(thppy)(PPh₃)] (1) and the paramagnetic complexes [mer-Ru₂(μ-chb)Cl₆(PPh₃)₂] (2), and [Ru(pym)] (3), respectively. The complexes were characterized by IR, NMR, and UV–vis spectroscopy and molar conductivity measurements. The structures were confirmed by single crystal X-ray diffraction studies. The redox properties of the metal complexes were probed via cyclic- and squarewave voltammetry. Finally, the radical scavenging capabilities of the metal complexes towards the NO and 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radicals were investigated     

Solvent effects on the photochemical and fluorescence properties of zinc phthalocyanine derivatives

The effects of solvents on the singlet oxygen, photobleaching and fluorescence quantum yields for zinc phthalocyanine (ZnPc) and its derivatives; (pyridino)zinc phthalocyanine ((py)ZnPc), zinc octaphenoxyphthalocyanine (ZnOPPc) and zinc octaestronephthalocyanine (ZnOEPc), is presented. The effects of the solvents on the ground state spectra are also discussed. The largest red shift of the Q band was observed in aromatic solvents, the highest shift being observed for 1-chloronaphthalene. Higher singlet fluorescence quantum yields were observed in THF for ZnPc and ZnOPPC. Also in the same solvent phototransformation rather than photobleaching was observed for ZnOPPc. Split Q band in the emission and excitation spectra of ZnOPPc was observed in some solvents and this is explained in terms of the lowering of symmetry following excitation.     

Solvent Effects on the Spectral Properties of Rhodamine 6G: Estimation of Ground and Excited State Dipole Moments

Spectroscopic and photophysical behavior of Rhodamine 6G (R6G) in seven solvents are reported in this work. R6G monomers exhibit strong electronic absorptions (due to π*←π transitions) in the 529–539-nm region, and the band positions were shown to depend on the refractive indices of the respective solvents. The Stokes’ shifts displayed a linear dependence on solvent polarity, with values ranging between 19 nm (in benzene) and 28 nm (in water). R6G’s fluorescence quantum yields (Φ_F) are generally high (> 0.90), and this was ascribed to structural features (rigidity, planarity and presence of condensed rings) in the R6G molecule. These Φ_F values are shown to vary with solvent viscosity in accordance with the Förster–Hoffmann model. Fluorescence quenching of R6G by 1,4-benzoquinone was diffusion controlled and occurred via an electron transfer mechanism. Theoretical treatment of the fluorescence quenching data yielded fluorescence lifetime values, which were also shown to be solvent viscosity dependent. Ground-state and excited-state dipole moments of R6G were obtained semi-empirically via the analysis of solvatochromic data, and the values are found to be 0.69 D and 1.97 D, respectively.