Metal-to-Ligand Charge Transfer Excited-State ν(CO) Shifts in Rigid Media

Dattelbaum, Dana M.; Meyer, Thomas J.

doi:10.1021/jp014057z

Cited by 24 publications

(33 citation statements)

References 51 publications

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“…Under C s symmetry, there are three CO stretching modes: a′-(1) at 2035 cm -1 and the overlapping symmetric (a′ (2)) and antisymmetric a′′ modes at 1910 cm -1 . 55,56 The peak positions shift slightly with pH (less than 7 cm -1 ) over pH 0-9, showing no obvious trends. The reason for the shift remains unclear.…”

Section: Ph Dependence Of Photophysicsmentioning

confidence: 95%

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

et al. 2005

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Photoinduced interfacial electron transfer (ET) from molecular adsorbates to semiconductor nanoparticles has been a subject of intense recent interest. Unlike intramolecular ET, the existence of a quasicontinuum of electronic states in the solid leads to a dependence of ET rate on the density of accepting states in the semiconductor, which varies with the position of the adsorbate excited-state oxidation potential relative to the conduction band edge. For metal oxide semiconductors, their conduction band edge position varies with the pH of the solution, leading to pH-dependent interfacial ET rates in these materials. In this work we examine this dependence in Re(L P )(CO) 3 Cl (or ReC1P) [L P ) 2,2′-bipyridine-4,4′-bis-CH 2 PO(OH) 2 ] and Re-(L A )(CO) 3 Cl (or ReC1A) [L A ) 2,2′-bipyridine-4,4′-bis-CH 2 COOH] sensitized TiO 2 and ReC1P sensitized SnO 2 nanocrystalline thin films using femtosecond transient IR spectroscopy. ET rates are measured as a function of pH by monitoring the CO stretching modes of the adsorbates and mid-IR absorption of the injected electrons. The injection rate to TiO 2 was found to decrease by 1000-fold from pH 0-9, while it reduced by only a factor of a few to SnO 2 over a similar pH range. Comparison with the theoretical predictions based on Marcus' theory of nonadiabatic interfacial ET suggests that the observed pH-dependent ET rate can be qualitatively accounted for by considering the change of density of electron-accepting states caused by the pH-dependent conduction band edge position.

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Section: Ph Dependence Of Photophysicsmentioning

confidence: 95%

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

et al. 2005

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“…This type of π* SCN back-bonding has been successfully used by a number of researchers as a spectroscopic tag for TRIR (time-resolved infrared) experiments involving electronic excitation of transition metal complexes. [19][20][21][22][23][24][25][26][27] Similarly, we can analyze the frequency changes in the ground and excited states to investigate the electron transition during the excitation. The frequencies were calculated based on the optimized geometries in the ground and the lowest-lying excited states, respectively.…”

Section: Molecular Orbital Analysismentioning

confidence: 99%

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2′‐bipyridyl)platinum(II)

Hu¹,

Liu²,

Feng³

2007

Chin. J. Chem.

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This paper presents a Density Functional or Time Dependent Density Functional (DFT/TDDFT) study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers: bis(isothiocyanato-S)(2,2'-bipyridyl) platinum(II) ([Pt(SCN) 2 (bpy)]), (isothiocyanato-S)(thiocyanato-N)-(2,2'-bipyridyl) platinum(II) ([Pt(SCN)(NCS)(bpy)]), and bis(thiocyanato-N)(2,2')-bipyridyl)platinum(II) ([Pt(NCS) 2 (bpy)]), in which different coordination ligands based on the N-and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries were compared to the experimentally observed structures. TDDFT calculation was carried out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model (PCM) to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agreement with the experimental determinations. The first two absorptions were found to originate from mixed platinum-SCN (or NSC) to bipyridyl-π* transitions rather than pure metal-to-ligand-charge-transfer (MLCT) transitions, whereas the higher-energy bands arose from intraligand π→π* transitions. The stretching frequencies of C≡N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper.

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“…Here, by using transient IR spectroscopy, we can directly identify the redox state of the Re(I) complex on the surface also after the initial quenching event via the carbonyl stretch vibrations, which serve as spectroscopic markers for redox state of the Re center. 30,31 Figure 1 Scheme of the investigated system of the rhenium carbonyl complex on the surface with the quencher in solution (RePOH@ZrO2) and with the quencher co-adsorbed (RePOH+Phtz@ZrO2). For comparison, a system with all compounds in solution has been considered as well with RePOH and RePOas the electron acceptor.…”

Section: Introductionmentioning

confidence: 99%

Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO₂

et al. 2019

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In the wider context of artificial photosynthesis, this work aims to explore the functionality and characteristics of rhenium tricarbonyl complexes as photosensitizers in heterogeneous water reduction systems. To that end, the reductive quenching of an excited ReICl(2,2-bipyridine-4,4-bisphosphonic acid)(CO)3 adsorbed on a redox-neutral scaffold by phenothiazine was observed by transient IR spectroscopy. From the spectroscopic and time response, the full reaction cycle could be elucidated, and the intrinsic lifetime of the excited Re complex, together with rates for reductive quenching, cage escape, as well as geminate recombination and secondary back electron transfer could be determined. Three different scenarios have been explored, which decrease the mobility of the reactants in the system in a stepwise manner: Starting from a reference system with all compounds in solution, first the Re complex was immobilized on the surface, and in a second step also the quencher. The overall reaction cycle for all reactants in solution is preserved as long as the quencher is in solution, with relatively minor changes of the rates of the individual reaction steps. The overall cage escape yield was found to be larger on the surface. As soon as the quencher is co-adsorbed alongside the Re-complex, however, the reaction cycle changes completely. Electron transfer occurred only from quencher molecules that sit next to an excited Re complex, and there is no possibility of cage escape. Varying the ratio of quencher molecules and Re-complexes, it is concluded that molecules do not cluster on the surface, and that excitation energy migration is not a very efficient process.

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Metal-to-Ligand Charge Transfer Excited-State ν(CO) Shifts in Rigid Media

Cited by 24 publications

References 51 publications

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2′‐bipyridyl)platinum(II)

Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO₂

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Metal-to-Ligand Charge Transfer Excited-State ν(CO) Shifts in Rigid Media

Cited by 24 publications

References 51 publications

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2′‐bipyridyl)platinum(II)

Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO2

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Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO₂