The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)

2003 ◽  
Vol 68 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Stanislav Záliš ◽  
Antonín Vlček ◽  
Chantal Daniel
Keyword(s):  
Excited States ◽  
Substitution Effect ◽  
Electronic Transitions ◽  
Ligand Field ◽  
Metal Carbonyls ◽  
Electron Density Redistribution ◽  
Time Resolved ◽  
Model Complex ◽  
Td Dft ◽  
Time Resolved Infrared Spectroscopy

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.

scholarly journals Towards Iron(II) Complexes with Octahedral Geometry: Synthesis, Structure and Photophysical Properties

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5991
Author(s):  
Mohamed Darari ◽  
Antonio Francés-Monerris ◽  
Bogdan Marekha ◽  
Abdelatif Doudouh ◽  
Emmanuel Wenger ◽  
...  
Keyword(s):  
Excited States ◽  
Photophysical Properties ◽  
Octahedral Geometry ◽  
Ligand Field ◽  
Unexpected Result ◽  
Quintet State ◽  
Dft Modeling ◽  
Ligand Charge Transfer ◽  
Td Dft ◽  
Polypyridine Complexes

The control of ligand-field splitting in iron (II) complexes is critical to slow down the metal-to-ligand charge transfer (MLCT)-excited states deactivation pathways. The gap between the metal-centered states is maximal when the coordination sphere of the complex approaches an ideal octahedral geometry. Two new iron(II) complexes (C1 and C2), prepared from pyridylNHC and pyridylquinoline type ligands, respectively, have a near-perfect octahedral coordination of the metal. The photophysics of the complexes have been further investigated by means of ultrafast spectroscopy and TD-DFT modeling. For C1, it is shown that—despite the geometrical improvement—the excited state deactivation is faster than for the parent pseudo-octahedral C0 complex. This unexpected result is due to the increased ligand flexibility in C1 that lowers the energetic barrier for the relaxation of 3MLCT into the 3MC state. For C2, the effect of the increased ligand field is not strong enough to close the prominent deactivation channel into the metal-centered quintet state, as for other Fe-polypyridine complexes.

scholarly journals Time-Resolved Infrared Spectroscopy in Supercritical Fluids

1999 ◽  
Vol 19 (1-4) ◽  
pp. 133-139 ◽  
Author(s):  
Michael W. George ◽  
Martyn Poliakoff ◽  
Xue-Zhong Sun ◽  
David C. Grills
Keyword(s):  
Infrared Spectroscopy ◽  
Supercritical Fluids ◽  
Room Temperature ◽  
Noble Gas ◽  
Fast Time ◽  
Metal Carbonyls ◽  
Time Resolved ◽  
Organometallic Reactions ◽  
Time Resolved Infrared Spectroscopy ◽  
First Time

We have used fast Time-resolved Infrared Spectroscopy (TRIR) to probe organometallic reactions in supercritical fluids on the nanosecond time-scale. This has allowed us to identify, for the first time in solution at room temperature, organometallic noble gas complexes which are formed following irradiation of metal carbonyls in supercritical noble gas solution. We have found that these complexes are surprisingly stable and have comparable reactivity to organometallic alkane complexes. We have also studied the coordination of CO2 to metal centres in supercritical CO2 (scCO2) and provide the first evidence for the formation and reactivity of ɳ1-O bound metal CO2 complexes in solution at or above room temperature.

scholarly journals Direct observation by time-resolved infrared spectroscopy of the bright and the dark excited states of the [Ru(phen)2(dppz)]2+ light-switch compound in solution and when bound to DNA

2016 ◽  
Vol 7 (5) ◽  
pp. 3075-3084 ◽  
Author(s):  
Fergus E. Poynton ◽  
James P. Hall ◽  
Páraic M. Keane ◽  
Christine Schwarz ◽  
Igor V. Sazanovich ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Excited States ◽  
Direct Observation ◽  
Time Resolved ◽  
Time Resolved Infrared Spectroscopy

Strikingly different TRIR spectra are recorded for the complex in D2O or CD3CN or when DNA-bound.

scholarly journals Ruthenium Assemblies for CO2 Reduction and H2 Generation: Time Resolved Infrared Spectroscopy, Spectroelectrochemistry and a Photocatalysis Study in Solution and on NiO

2021 ◽  
Vol 9 ◽  
Author(s):  
Florian J. R. Cerpentier ◽  
Joshua Karlsson ◽  
Ralte Lalrempuia ◽  
Michael P. Brandon ◽  
Igor V. Sazanovich ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Excited States ◽  
Co2 Reduction ◽  
Carbonyl Groups ◽  
Intermediate Species ◽  
Time Resolved ◽  
H2 Generation ◽  
Catalytic Metal ◽  
The One ◽  
Time Resolved Infrared Spectroscopy

Two novel supramolecular complexes RuRe ([Ru(dceb)2(bpt)Re(CO)3Cl](PF6)) and RuPt ([Ru(dceb)2(bpt)PtI(H2O)](PF6)2) [dceb = diethyl(2,2′-bipyridine)-4,4′-dicarboxylate, bpt = 3,5-di(pyridine-2-yl)-1,2,4-triazolate] were synthesized as new catalysts for photocatalytic CO2 reduction and H2 evolution, respectively. The influence of the catalytic metal for successful catalysis in solution and on a NiO semiconductor was examined. IR-active handles in the form of carbonyl groups on the peripheral ligand on the photosensitiser were used to study the excited states populated, as well as the one-electron reduced intermediate species using infrared and UV-Vis spectroelectrochemistry, and time resolved infrared spectroscopy. Inclusion of ethyl-ester moieties led to a reduction in the LUMO energies on the peripheral bipyridine ligand, resulting in localization of the 3MLCT excited state on these peripheral ligands following excitation. RuPt generated hydrogen in solution and when immobilized on NiO in a photoelectrochemical (PEC) cell. RuRe was inactive as a CO2 reduction catalyst in solution, and produced only trace amounts of CO when the photocatalyst was immobilized on NiO in a PEC cell saturated with CO2.

scholarly journals Excited States and Intermediates by Time-Resolved Infrared Spectroscopy

1999 ◽  
Vol 19 (1-4) ◽  
pp. 245-251 ◽  
Author(s):  
J. J. Turner ◽  
M. W. George ◽  
I. P. Clark ◽  
I. G. Virrels
Keyword(s):  
Infrared Spectroscopy ◽  
Excited State ◽  
Charge Transfer ◽  
Excited States ◽  
Fast Time ◽  
Time Resolved ◽  
Excited Species ◽  
Charge Transfer Transitions ◽  
Time Resolved Infrared Spectroscopy ◽  
Kinetics Of

For coordination compounds containing CO or CN groups, fast time-resolved infrared spectroscopy (TRIR) provides a convenient method of probing excited states and intermediates. TRIR has proved particularly powerful for probing the structure and kinetics of organometallic intermediates. The interpretation is particularly straightforward when combined with IR data from matrix isolation experiments, although there can be some subtle differences. In excited state studies, shifts in ν(CO) and ν(CN) frequencies, from ground to excited state, are sensitive to the changes in electron distribution on excitation, thus allowing the distinction between charge-transfer and non-charge-transfer transitions. Subtle effects on excited state ν(CO) band positions occur with change from fluid to rigid solvent-“infrared rigidochromism”. There is often a change in ν(CO) band width on excitation; this can be interpreted in terms of specific interactions between the excited species and the solvent. This paper presents some of our recent work in this area.

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