The lowest energy excited states of the binuclear silver(I) halide complexes, Ag2(dmb)2X2. Metal-centered or charge transfer states?

1994 ◽  
Vol 72 (3) ◽  
pp. 705-713 ◽  
Author(s):  
Daniel Piché ◽  
Pierre D. Harvey
Keyword(s):  
Charge Transfer ◽  
Solid State ◽  
Excited States ◽  
Silver Halide ◽  
Molecular Orbital Calculations ◽  
Isocyanide Ligands ◽  
Visible Spectra ◽  
Halide Complexes ◽  
The Media ◽  
Uv Visible

The nature of the lowest energy excited states of the Ag2(dmb)2X2 complexes (X = Cl, Br, I; dmb = 1,8-diisocyano-ρ-menthane) have been addressed both experimentally and theoretically. It is shown that the lowest energy excited states of the complexes are charge transfer states from the silver-halide frame to the isocyanide ligands (M/XLCT) based upon UV-visible spectra and emission polarization ratio measurements, and extended Hückel molecular orbital calculations (EHMO). The metal-centered dσ* → pσ bands have been observed in the higher energy region of the spectra (232–242 nm). The complexes are luminescent (440 ≤ λe ≤ 480 nm) both in a glass and in the solid state at 77 K where the emission lifetimes, τe, range from 20 to 90 µs, which depend upon the nature of the halide (for the solid state data) and the media. No emission is observed at room temperature.

CHAMELEON GROUND STATE AND EXCITED STATES OF EDT-TTF-IM-F4TCNQ RADICAL DYAD IN DIFFERENT ENVIRONMENTS

2012 ◽  
Vol 11 (03) ◽  
pp. 505-525 ◽  
Author(s):  
YUHUA ZHOU ◽  
KAI TAN ◽  
XIN LU
Keyword(s):  
Charge Transfer ◽  
Solid State ◽  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Solvent Polarity ◽  
Functional Study ◽  
Polar Solvents ◽  
Model Calculations ◽  
A Charge

We have performed a systematic density functional study on the ground-state electronic structure and excited states of a representative D-σ-A dyad, i.e. EDT-TTF-Im-F4TCNQ π-radical, in vacuo and in different conventional solvents (toluene, THF, DMF and DMSO) by using some popular hybrid density functionals (B3LYP, M05, M05-2X, PBE0 and BMK). It has been shown that the M05 and B3LYP functionals perform the best in predicting the intramolecular charge-transfer (ICT) pertaining to both the ground state and excited states of the dyad. The amphoteric dyad is liable to solvent-promoted ICT from its EDT-TTF-Im donor (D) to F4TCNQ acceptor (A), adopting a charge-unseparated ground state D-A• in vacuo, a partially zwitterionic ground state [D-A]• in nonpolar toluene solvent, and a fully zwitterionic ground state D•+-A- in such polar solvents as THF, DMF and DMSO. Owing to its solvent-dependent chameleon ground state, excited states of the dyad in solvents also exhibit remarkable dependence on solvent polarity, as revealed by TDDFT calculations. Furthermore, cluster model calculations revealed that intermolecular charge-transfer readily occurs between the dyads, accounting for the observed zwitterionic charge state in solid state and solid-state semiconductivity.

scholarly journals Study of interaction of metal ions with methylthymol blue by chemometrics and quantum chemical calculations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zolaikha Rasouli ◽  
Mehdi Irani ◽  
Sonia Jafari ◽  
Raouf Ghavami
Keyword(s):  
Charge Transfer ◽  
Metal Ions ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Multivariate Curve Resolution ◽  
Molar Ratio ◽  
Ligand Charge Transfer ◽  
Visible Spectra ◽  
Uv Visible ◽  
Methylthymol Blue

AbstractIn this study, we determine the acidity constants of methylthymol blue (MTB) and association constants of its complexes with the ZnII, CuII, and FeII metal ions (MIs), through theoretical and experimental means. The complexes were characterized using UV–Visible absorption spectroscopy combined with soft/hard chemometrics methods and quantum chemical calculations. Quantum chemical calculations revealed that electronic transitions in the UV–Visible spectra of MTB have mixed n → π* and π → π* characters. The results of molar ratio and multivariate curve resolution alternating least squares (MCR-ALS) revealed the formation of successive 1:2 and 1:1 complexes (MI:MTB) for the ZnII and CuII systems. However, the formation of successive 1:1 and 2:1 complexes are suggested for FeII by the molar ratio and MCR-ALS. The majority of transitions observed in the UV–Visible spectra of the Zn(MTB) and Cu(MTB) complexes have ligand-to-ligand charge transfer (LLCT) characters. However, the transitions in the UV–Visible spectrum of the Fe(MTB) complex have LLCT and metal-to-ligand charge transfer (MLCT) characters. For the Fe2(MTB) complex, the lowest energy transition of has an LLCT character. However, its higher energy transitions are a mixture of LLCT, MLCT, and metal-to-metal charge transfer (MMCT) characters. The correlation between experimental and computed wavelengths revealed that the 1:1 complexes of ZnII and CuII prefer square pyramidal geometries. However, the FeII complexes always show octahedral geometry.

Charge Transfer Device Detectors for Analytical Optical Spectroscopy—Operation and Characteristics

1987 ◽  
Vol 41 (7) ◽  
pp. 1114-1125 ◽  
Author(s):  
R. B. Bilhorn ◽  
J. V. Sweedler ◽  
P. M. Epperson ◽  
M. B. Denton
Keyword(s):  
Charge Transfer ◽  
Solid State ◽  
Dark Count ◽  
New Class ◽  
Element Size ◽  
Detector Element ◽  
Uv Visible ◽  
Charge Transfer Device ◽  
Operation Characteristics ◽  
Transfer Device

This article is the first in a two-part series describing the operation, characteristics, and application of a new class of solid-state multichannel UV-visible detectors. In this paper, charge transfer devices (CTDs) are described. Detector characteristics pertinent to spectroscopic application—including quantum efficiency, read noise, dark count rate, and available formats—are emphasized. Unique capabilities, such as the ability to nondestructively read out the detector array and the ability to alter the effective detector element size by a process called binning, are described. CTDs with peak quantum efficiencies over 80% and significant responsivity over the wavelength range of 0.1 nm to 1100 nm are discussed. Exceptionally low dark count rates, which allow integration times of up to many hours and read noises more than two orders of magnitude lower than those read by commercially available PDA detectors, contribute to the outstanding performance offered by these detectors.

On the ground and excited state dipole moments of planar vs. twisted nitroaniline analogues

1991 ◽  
Vol 69 (3) ◽  
pp. 550-557 ◽  
Author(s):  
Hemant K. Sinha ◽  
Keith Yates
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Charge Distribution ◽  
Excited States ◽  
Reasonable Agreement ◽  
Dipole Moments ◽  
Molecular Orbital Calculations ◽  
Adequate Explanation ◽  
Excited State Dipole Moments ◽  
State Charge

Planar and conformationally twisted p-nitroaniline (PNA) and N,N-dimethyl-p-nitroaniline (DMPNA) systems have been subjected to electric field study (electrochromism) to understand their charge transfer characteristics in the ground and excited states. The observed values of ground and excited state dipole moments suggest that twisting of either the donor (D) with respect to the acceptor (A) or vice versa can have a large impact on the resultant charge distribution, particularly on the excited state charge distribution. These observations remarkably support the TICT hypothesis and minimum overlap rule, as proposed by Grabowski et al. Simple molecular orbital calculations provide adequate explanation for the observed changes in the dipole moment and reasonable agreement has been found in each case studied. Key words: electrochromism, dipole moments, charge transfer.

Infrared and UV-visible spectra of layer semiconductors Gas, GaSe and GaTe

1977 ◽  
Vol 38 (10) ◽  
pp. 1293-1299 ◽  
Author(s):  
U. Giorgianni ◽  
G. Mondio ◽  
P. Perillo ◽  
G. Saitta ◽  
G. Vermiglio
Keyword(s):  
Visible Spectra ◽  
Uv Visible

Synthesis and Photochemical Properties of Re(I) Tricarbonyl Complexes Bound to Thione and Thiazole-2-ylidene Ligands

2020 ◽  
Author(s):  
Matthew Stout ◽  
Brian Skelton ◽  
Alexandre N. Sobolev ◽  
Paolo Raiteri ◽  
Massimiliano Massi ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Ligand Exchange ◽  
Ligand Substitution ◽  
Bidentate Ligand ◽  
The Other ◽  
Ligand Exchange Reaction ◽  
Multiple Products ◽  
Ligand Charge Transfer ◽  
Photochemical Properties

<p>Three Re(I) tricarbonyl complexes, with general formulation Re(N^L)(CO)<sub>3</sub>X (where N^L is a bidentate ligand containing a pyridine functionalized in the position 2 with a thione or a thiazol-2-ylidene group and X is either chloro or bromo) were synthesized and their reactivity explored in terms of solvent-dependent ligand substitution, both in the ground and excited states. When dissolved in acetonitrile, the complexes bound to the thione ligand underwent ligand exchange with the solvent resulting in the formation of Re(NCMe)<sub>2</sub>(CO)<sub>3</sub>X. The exchange was found to be reversible, and the starting complex was reformed upon removal of the solvent. On the other hand, the complexes appeared inert in dichloromethane or acetone. Conversely, the complex bound to the thiazole-2-ylidene ligand did not display any ligand exchange reaction in the dark, but underwent photoactivated ligand substitution when excited to its lowest metal-to-ligand charge transfer manifold. Photolysis of this complex in acetonitrile generated multiple products, including Re(I) tricarbonyl and dicarbonyl solvato-complexes as well as free thiazole-2-ylidene ligand.</p>

Charge Transfer Between CO22+ and Ar or Ne at Collision Energies 3-10 eV

2003 ◽  
Vol 68 (1) ◽  
pp. 178-188 ◽  
Author(s):  
Libor Mrázek ◽  
Ján Žabka ◽  
Zdeněk Dolejšek ◽  
Zdeněk Herman
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Ground State ◽  
Scattering Method ◽  
Translational Energy ◽  
Centre Of Mass ◽  
Energy Distributions ◽  
Zener Model ◽  
Beam Scattering ◽  
Product Ions

The beam scattering method was used to investigate non-dissociative single-electron charge transfer between the molecular dication CO22+ and Ar or Ne at several collision energies between 3-10 eV (centre-of-mass, c.m.). Relative translational energy distributions of the product ions showed that in the reaction with Ar the CO2+ product was mainly formed in reactions of the ground state of the dication, CO22+(X3Σg-), leading to the excited states of the product CO2+(A2Πu) and CO2+(B2Σu+). In the reaction with Ne, the largest probability had the process from the reactant dication excited state CO22+(1Σg+) leading to the product ion ground state CO2+(X2Πg). Less probable were processes between the other excited states of the dication CO22+, (1∆g), (1Σu-), (3∆u), also leading to the product ion ground state CO2+(X2Πg). Using the Landau-Zener model of the reaction window, relative populations of the ground and excited states of the dication CO22+ in the reactant beam were roughly estimated as (X3Σg):(1∆g):(1Σg+):(1Σu-):(3∆u) = 1.0:0.6:0.5:0.25:0.25.

scholarly journals Zn(II) Heteroleptic Halide Complexes with 2-Halopyridines: Features of Halogen Bonding in Solid State

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3393
Author(s):  
Mikhail A. Vershinin ◽  
Marianna I. Rakhmanova ◽  
Alexander S. Novikov ◽  
Maxim N. Sokolov ◽  
Sergey A. Adonin
Keyword(s):  
Solid State ◽  
Quantum Yield ◽  
Crystal Packing ◽  
Halogen Bonding ◽  
Molecular Complexes ◽  
Substituted Pyridines ◽  
Halide Complexes

Reactions between Zn(II) dihalides and 2-halogen-substituted pyridines 2-XPy result in a series of heteroleptic molecular complexes [(2-XPy)2ZnY2] (Y = Cl, X = Cl (1), Br (2), I (3); Y = Br, X = Cl (4), Br (5), I (6), Y = I, X = Cl (7), Br (8), and I (9)). Moreover, 1–7 are isostructural (triclinic), while 8 and 9 are monoclinic. In all cases, halogen bonding plays an important role in formation of crystal packing. Moreover, 1–9 demonstrate luminescence in asolid state; for the best emitting complexes, quantum yield (QY) exceeds 21%.

scholarly journals Unusual piezochromic fluorescence of a distyrylpyrazine derivative crystals: phase transition through [2 + 2] photocycloaddition under UV irradiation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Young-Jae Jin ◽  
Hyosang Park ◽  
Byung-Chun Moon ◽  
Jae Hong Kim ◽  
Wang-Eun Lee ◽  
...  
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Uv Irradiation ◽  
Mechanical Grinding ◽  
Green Color ◽  
H Nmr ◽  
Uv Visible ◽  
Stacking Structure ◽  
Orange Color ◽  
Molecular Stacking

AbstractThe piezochromic fluorescence (FL) of a distyrylpyrazine derivative, 2,3-diisocyano-5,6-distyrylpyrazine (DSP), was investigated in this study. Depending on the recrystallization method, DSP afforded two different crystals with green and orange FL emission. The orange color FL emission crystal (O-form) was easily converted to the green color FL emission one (G-form) by manual grinding. The G-form was also converted to a slightly different orange color FL emission crystal (RO-form) by a weak UV irradiation. When the RO-form was ground again, the G-form was regenerated. The FL colors changed between the G- and RO-forms over several ten times by repeated mechanical grinding and UV irradiation. The FL, UV–visible, 1H-NMR and XRD results showed that the O (or RO)-to-G transformation induced by mechanical stress results from the change of degree of molecular stacking from dense molecular stacking structure to relatively loose molecular stacking structure, whereas the G-to-RO reconversion by UV irradiation results from return to dense molecular stacking structure again due to lattice movement (lattice slipping) allowed by photocycloaddition in solid-state.

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