scholarly journals Chelating Mechanisms of Transition Metals by Bacterial Metallophores “Pseudopaline and Staphylopine”: A Quantum Chemical Assessment

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 56 ◽  
Author(s):  
Ghassan Ghssein ◽  
Samir Matar
Keyword(s):  
Excited States ◽  
Quantum Chemical ◽  
Density Functional ◽  
Ionic Species ◽  
Active Centers ◽  
Functional Theory ◽  
Ligand Charge Transfer ◽  
Td Dft ◽  
Vibration Spectroscopy ◽  
Quantum Chemical Computations

In bacterial pathology, metallophores fabricated by bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa are exported to surrounding physiological media via a specific process to sequester and import metals, resulting in enhanced virulence of the bacteria. While these mechanisms are understood at qualitative levels, our investigation presents a complementary original view based on quantum chemical computations. Further understanding of the active centers in particular was provided for pseudopaline and staphylopine metallophores, which were described chemically and with vibration spectroscopy. Then, for complexes formed with a range of transition metal divalent ions (Ni, Cu, and Zn), description and analyses of the frontier molecular orbitals (FMOs) are provided, highlighting a mechanism of metal-to-ligand charge transfer (MLCT), based on excited-states calculations (time-dependent density functional theory (TD-DFT)) at the basis of the delivery of the metallic ionic species to the bacterial medium, leading eventually to its enhanced virulence. Such investigation gains importance especially in view of stepwise syntheses of metallophores in the laboratory, providing significant progress in the understanding of mechanisms underlying the enhancement of bacterial pathologies.

Spectroscopic trends in a series of Re(I) α-diimine complexes as a function of the antenna/photoisomerizable ligands: a TD-DFT and MS-CASPT2 study

2014 ◽  
Vol 92 (10) ◽  
pp. 979-986 ◽  
Author(s):  
Megumi Kayanuma ◽  
Chantal Daniel ◽  
Etienne Gindensperger
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Density Functional ◽  
Time Dependent ◽  
Functional Theory ◽  
B3lyp Level ◽  
Ligand Charge Transfer ◽  
Td Dft ◽  
Energy Domain ◽  
Diimine Complexes

The absorption spectra of 11 rhenium(I) complexes with photoisomerizable stilbene-like ligands have been investigated by means of density functional theory (DFT). The electronic structures of the ground and excited states were determined for [Re(CO)3(N,N)(L)]+ (N,N = bpy (2,2′-bipyridine), phen (1,10-phenanthroline), Me4phen (3,4,7,8-tetramethyl-1,10-phenanthroline), ph2phen (4,7-diphenyl-1,10-phenanthroline), or Clphen (5-chloro-1,10-phenanthroline); L = bpe (1,2-bis(4-pyrydil)ethylene), stpy (4-styrylpyridine), or CNstpy (4-(4-cyano)styrylpyridine)) at the time–dependent (TD) DFT/CAM-B3LYP level of theory in vacuum and acetonitrile to highlight the effects of both antenna N,N and isomerizable L ligands. The TD-DFT spectra of two representative complexes, namely [Re(CO)3(bpy)(stpy)]+ and [Re(CO)3(phen)(bpe)]+, have been compared with MS-CASPT2 spectra. The TD-DFT spectra obtained in vacuum and acetonitrile agree rather well both with the ab initio and experimental spectra. The absorption spectroscopy of this series of molecules is characterized by the presence of three low-lying metal to ligand charge transfer (MLCT) states absorbing in the visible energy domain. The nature of the isomerizable ligands (bpe, stpy, or CNstpy) and the type of antenna ligands (bpy, phen, and substituted phen) control the degree of mixing between the MLCT and intraligand excited states, their relative energies, as well as their intensities.

Luminescence properties and optimized structural conformations of the S0, S1 and T1 states of a tetranuclear formamidinate complex based on AuI and AgI metal ions

2019 ◽  
Vol 75 (7) ◽  
pp. 985-989
Author(s):  
Wayne Hsu
Keyword(s):  
Metal Ions ◽  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Metal Salts ◽  
Time Dependent ◽  
Functional Theory ◽  
Planar Conformation ◽  
Ligand Charge Transfer ◽  
Td Dft

N,N′-Bis(pyridin-4-yl)formamidine (4-pyfH) was reacted with AuI and AgI metal salts to form a novel tetranuclear complex, tetrakis[μ-N,N′-bis(pyridin-4-yl)formamidinato]digold(I)disilver(I), [Ag2Au2(C11H9N4)2] or [Au x Ag4–x (4-pyf)4] (x = 0–4), 1, which is supported by its metallophilicity. Due to the potential permutation of the coordinated metal ions, six different canonical structures of 1 can be obtained. Complex 1 shows an emission at 501 nm upon excitation at 375 nm in the solid state and an emission at 438 nm upon excitation at 304 nm when dispersed in methanol. Time-dependent density functional theory (TD-DFT) calculations confirmed that these emissions can be ascribed to metal-to-ligand charge transfer (MLCT) processes. Moreover, the calculations of the optimized structural conformations of the S0 ground state, and the S1 and T1 excited states are discussed and suggest a distorted planar conformation for the tetranuclear Au2Ag2 complex.

scholarly journals Macroscopic quantum electrodynamics and density functional theory approaches to dispersion interactions between fullerenes

2020 ◽  
Vol 22 (40) ◽  
pp. 23295-23306
Author(s):  
Saunak Das ◽  
Johannes Fiedler ◽  
Oliver Stauffert ◽  
Michael Walter ◽  
Stefan Yoshi Buhmann ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Excited States ◽  
Quantum Electrodynamics ◽  
Density Functional ◽  
Dispersion Interactions ◽  
Functional Theory ◽  
Electronically Excited States ◽  
Macroscopic Quantum ◽  
Td Dft ◽  
Electronically Excited

Van der Waals potentials determine supramolecular structures of molecules in ground and long-lived electronically excited states. We investigate how macroscopic quantum electrodynamics can be used to efficiently describe such potentials based on (TD)DFT-derived polarizabilities.

A density functional theory and spectroscopic study of intramolecular quenching of metal-to-ligand charge-transfer excited states in some mono-bipyridine ruthenium(II) complexes

2014 ◽  
Vol 92 (10) ◽  
pp. 996-1009 ◽  
Author(s):  
Shivnath Mazumder ◽  
Ryan A. Thomas ◽  
Richard L. Lord ◽  
H. Bernhard Schlegel ◽  
John F. Endicott
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Charge Transfer ◽  
Excited States ◽  
Lower Energy ◽  
Density Functional ◽  
Dimethyl Sulfide ◽  
Intramolecular Electron Transfer ◽  
Functional Theory ◽  
Ligand Charge Transfer

The complexes [Ru(NCCH3)4bpy]2+ and [Ru([14]aneS4)bpy]2+ ([14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane, bpy = 2,2′-bipyridine) have similar absorption and emission spectra but the 77 K metal-to-ligand charge-transfer (MLCT) excited state emission lifetime of the latter is less than 0.3% that of the former. Density functional theory modeling of the lowest energy triplet excited states indicates that triplet metal centered (3MC) excited states are about 3500 cm−1 lower in energy than their 3MLCT excited states in both complexes. The differences in excited state lifetimes arise from a much larger coordination sphere distortion for [Ru(NCCH3)4bpy]2+ and the associated larger reorganizational barrier for intramolecular electron transfer. The smaller ruthenium ligand distortions of the [Ru([14]aneS4)bpy]2+ complex are apparently a consequence of stereochemical constraints imposed by the macrocyclic [14]aneS4 ligand, and the 3MC excited state calculated for the unconstrained [Ru(S(CH3)2)4bpy]2+ complex (S(CH3)2 = dimethyl sulfide) is distorted in a manner similar to that of [Ru(NCCH3)4bpy]2+. Despite the lower energy calculated for its 3MC than 3MLCT excited state, [Ru(NCCH3)4bpy]2+ emits strongly in 77 K glasses with an emission quantum yield of 0.47. The emission is biphasic with about a 1 μs lifetime for its dominant (86%) emission component. The 405 nm excitation used in these studies results in a significant amount of photodecomposition in the 77 K glasses. This is a temperature-dependent biphotonic process that most likely involves the bipyridine-radical anionic moiety of the 3MLCT excited state. A smaller than expected value found for the radiative rate constant is consistent with a lower energy 3MC than 3MLCT state.

BIS(BIPYRIDYL)-RU(II)-1-BENZOYL-3-(PYRIDINE-2-YL)-1H-PYRAZOLE AS POTENTIAL PHOTOSENSITISER: EXPERIMENTAL AND DENSITY FUNCTIONAL THEORY STUDY

2017 ◽  
Vol 79 (5-3) ◽  
Author(s):  
Wun-Fui Mark-Lee ◽  
Febdian Rusydi ◽  
Lorna Jeffery Minggu ◽  
Takashi Kubo ◽  
Mohammad Kassim
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Density Functional ◽  
Energy Levels ◽  
Spectroscopic Techniques ◽  
Functional Theory ◽  
Injection Process ◽  
Highest Occupied Molecular Orbital ◽  
Ligand Charge Transfer ◽  
Td Dft

Ru(II) complexes, [Ru(bpy)2(m-R-L)](PF6)2 where bpy = 2,2’-bipyridyl and  m-R-L= 1-(meta-R)-benzoyl-3-(pyridine-2-yl)-1H-pyrazole derivatives (R = H, CH3 and Cl) abbreviated as RuL, Ru(m-CH3-L) and Ru(m-Cl-L) complexes, respectively, were synthesized and characterized with spectroscopic techniques namely, infrared, UV-Vis and nuclear magnetic resonance (NMR), photoluminescence and mass spectroscopy. Density functional theory (DFT) and time-dependent (TD) DFT calculations were carried out to study the structural and electronic features of the molecules. These Ru(II) complexes exhibit photo-electronic properties required for a photosensitiser in a TiO2-catalysed photoelectrochemical (PEC) cell. In-depth understanding of the R-L fragment functionality is important to tune the photo-electronic properties of the Ru(II) complex. The highest-occupied molecular orbital (HOMO) is mainly localized at the Ru(II) centre, while the LUMO is dominantly spread across the R-L ligand. The Ru(II) complexes showed favourable metal-to-ligand charge transfer (MLCT) energy levels, which are comparably higher than the conduction band of TiO2 to facilitate electron injection process. Among the Ru(II) complexes, Ru(m-Cl-L) comparatively possesses the highest photoluminescence quantum yield and has the potential to be applied as photosensitiser in PEC systems.

A new phosphorescent heteroleptic cuprous complex with a neutral 2-methylquinolin-8-ol ligand: synthesis, structure characterization, properties and TD–DFT calculations

2017 ◽  
Vol 73 (6) ◽  
pp. 486-491 ◽  
Author(s):  
Rong-Er Shou ◽  
Li Song ◽  
Wen-Xiang Chai ◽  
Lai-Shun Qin ◽  
Tian-Gen Wang
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Low Cost ◽  
Structure Characterization ◽  
Yellow Emission ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Ligand Charge Transfer ◽  
Td Dft ◽  
Cuprous Complex

Luminescent CuI complexes have emerged as promising substitutes for phosphorescent emitters based on Ir, Pt and Os due to their abundance and low cost. The title heteroleptic cuprous complex, [9,9-dimethyl-4,5-bis(diphenylphosphanyl)-9H-xanthene-κ2 P,P](2-methylquinolin-8-ol-κ2 N,O)copper(I) hexafluorophosphate, [Cu(C10H9NO)(C39H32OP2)]PF6, conventionally abbreviated as [Cu(Xantphos)(8-HOXQ)]PF6, where Xantphos is the chelating diphosphine ligand 9,9-dimethyl-4,5-bis(diphenylphosphanyl)-9H-xanthene and 8-HOXQ is the N,O-chelating ligand 2-methylquinolin-8-ol that remains protonated at the hydroxy O atom, is described. In this complex, the asymmetric unit consists of a hexafluorophosphate anion and a whole mononuclear cation, where the CuI atom is coordinated by two P atoms from the Xantphos ligand and by the N and O atoms from the 8-HOXQ ligand, giving rise to a tetrahedral CuP2NO coordination geometry. The electronic absorption and photoluminescence properties of this complex have been studied on as-synthesized samples, whose purity had been determined by powder X-ray diffraction. In the detailed TD–DFT (time-dependent density functional theory) studies, the yellow emission appears to be derived from the inter-ligand charge transfer and metal-to-ligand charge transfer (M+L′)→LCT excited state (LCT is ligand charge transfer).

SPECTROSCOPIC AND QUANTUM-CHEMICAL INVESTIGATION OF TESTOSTERONE PROPIONATE, A COMMONLY MISUSED ANABOLIC STEROID

2021 ◽  
Author(s):  
Nikola Ristivojević ◽  
◽  
Dušan Dimić ◽  
Marko Đošić ◽  
Stefan Mišić ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Testosterone Propionate ◽  
Anabolic Steroids ◽  
Chemical Methods ◽  
Dft Methods ◽  
Functional Theory ◽  
Quantum Chemical Methods ◽  
Td Dft ◽  
Ir And Raman

Anabolic steroids are a group of commonly counterfeit substances used by individuals who want to gain weight and muscles. Testosterone propionate (TP), an ester analog of testosterone, belongs to this group and its spectroscopic analysis is important especially when it is improperly labeled and misused. In this contribution quantum chemical methods, at the B3LYP/6- 311++G(d,p) level of theory, were applied for the prediction of the vibrational (IR and Raman) and UV-VIS spectra of TP. The applicability of the chosen level of theory was proven based on the comparison between experimental and theoretical bond lengths and angles. The most prominent bands in the IR and Raman spectra were assigned and correlated with the calculated ones. The electronic spectra were also analyzed and the assignments were made based on the Time-Dependent Density Functional Theory (TD-DFT) calculations. The orbitals included in the most intense transitions were visualized and possible solvent effects were discussed. The presented results proved the applicability of the DFT methods for the prediction of spectra that could lead to the counterfeit substances determination.

Quantum Mechanics / Extremely Localized Molecular Orbital Embedding Strategy for Excited-States. 1. Coupling to Time-Dependent Density Functional Theory

2020 ◽  
Author(s):  
Giovanni Macetti ◽  
Alessandro Genoni
Keyword(s):  
Density Functional Theory ◽  
Quantum Mechanics ◽  
Excited States ◽  
Quantum Chemical ◽  
Density Functional ◽  
Time Dependent ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Large Systems ◽  
Dependent Density

The QM/ELMO (quantum mechanics / extremely localized molecular orbital) method is a recently developed embedding technique in which the most important region of the system under exam is treated at fully quantum mechanical level, while the rest is described by means of transferred and frozen extremely localized molecular orbitals. In this paper, we propose the first application of the QM/ELMO approach to the investigation of excited-states and, in particular, we present the coupling of the QM/ELMO philosophy with Time-Dependent Density Functional Theory (TDDFT). The proposed TDDFT/ELMO strategy has been subjected to a series of preliminary tests that were already considered for the validations of other embedding TDDFT methods. The obtained results show that the novel technique allows the accurate description of local excitations in large systems by only including a relatively small group of atoms in the region treated at fully quantum chemical level. Furthermore, it was observed that, even using functionals that do not take into account long-range corrections, the method enables to avoid the presence of artificial low-lying charge-transfer states that may affect traditional TDDFT calculations. Finally, through the application to a reduced model of the Green Fluorescent Protein, it was proved that the TDDFT/ELMO approach can be also successfully exploited to investigate local electronic transitions in large systems and that the accuracy of the results can be improved by including a sufficient number of fragments/residues that are chemically crucial in the quantum mechanical region. This work paves the way to further extensions of the QM/ELMO philosophy for the study of local excitations in extended systems, suggesting the coupling of the QM/ELMO approach with other quantum chemical methods for excited-states, from the simplest ΔSCF techniques to the most advanced and computationally expensive multi-references methods.

scholarly journals Synthesis, optical and electrochemical study of bipolar heterocyclic systems, including 1,2,4-oxadiazole moiety

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
D. G. Selivanova ◽  
O. A. Mayorova ◽  
A. A. Gorbunov ◽  
A. N. Vasyanin ◽  
M. V. Dmitriev ◽  
...  
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Time Dependent ◽  
Electrochemical Studies ◽  
Absorption Data ◽  
Functional Theory ◽  
Conjugation Chain ◽  
Td Dft ◽  
Triplet Excited States ◽  
New Compounds

AbstractTwo new 3,5-dihetarylsubstituted 1,2,4- oxadiazoles 8 a,b, including N-alkyl substituted carbazole and thiophene moieties, were synthesized as potential components of materials for organic electronics devices. Optical and electrochemical properties of all new compounds were investigated. On the basis of the experimental UV absorption data, the values of bandgap energies equal to 3.44 eV (8a) and 3.05 eV (8b) were determined. The values of their ionization potentials, HOMO levels (−5.62 eV for 8a, −5.46 eV – for 8b), as well as their electron affinity levels, LUMO levels (−2.2 eV for 8a, −2.4 eV – for 8b), were calculated from the results of electrochemical studies. The energy of the triplet excited states of 8 a,b was defined with the help of time-dependent density functional theory (TD-DFT), comprising 2.68 eV (8a) and 2.32 eV (8b), where the greatest value of this parameter was for the compound with a shorter conjugation chain.

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