The estimation of CO bond length changes in the excited states of transition metal carbonyls

Morrison, Sara L.; Turner, James J.

doi:10.1016/0022-2860(93)07859-u

Cited by 20 publications

(8 citation statements)

References 44 publications

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“…The pattern of bands is consistent with the adoption of a facial geometry for the three CO units about the rhenium(I) center . The bands are assigned from highest to lowest wavenumber as a‘(1), a‘ ‘, and a‘(2), respectively, according to recent computational and spectroscopic papers. − ,, The vibrational analysis assigns the three carbonyl bands 26 going from highest to lowest frequency as 0.47 r 18 + 0.62 r 17 + 0.62 r 21 (Figure ) which has a‘ symmetry, designated a‘(1), in the C s point group, 0.88 r 18 − 0.33 r 17 − 0.33 r 21 , designated a‘(2), also with a‘ symmetry, and 0.71 r 17 − 0.71 r 21 with a‘ ‘ symmetry, designated a‘ ‘. The wavenumbers observed are slightly higher for the a‘(1) and a‘(2) vibrations in [Re(dbq)(CO) 3 Cl] than for the [Re(dbn)(CO) 3 Cl] complex.…”

Section: Resultssupporting

confidence: 55%

The Effect of Reduction on Rhenium(I) Complexes with Binaphthyridine and Biquinoline Ligands: A Spectroscopic and Computational Study

et al. 2005

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A number of rhenium complexes with binaphthyridine and biquinoline ligands have been synthesized and studied. These are [Re(L)(CO)3Cl] where L = 3,3'-dimethylene-2,2'-bi-1,8-naphthyridine (dbn), 2,2'-bi-1,8-naphthyridine (bn), 3,3'-dimethylene-2,2'-biquinoline (dbq), and 3,3'-dimethyl-2,2'-biquinoline (diq). This series represents ligands in which the electronic properties and steric preferences are tuned. These complexes are modeled using density functional theory (DFT). An analysis of the resonance Raman spectra for these complexes, in concert with the vibrational assignments, reveals that the accepting molecular orbital (MO) in the metal-to-ligand charge transfer (MLCT) transition is the LUMO and causes bonding changes at the inter-ring section of the ligand. The electronic absorption spectroelectrochemistry for the reduced complexes of [Re(dbn)(CO)3Cl], [Re(dbq)(CO)3Cl], and [Re(diq)(CO)3Cl] suggest that the singly occupied MO is delocalized over the entire ligand structure despite the nonplanar nature of the diq ligand in [Re(diq)(CO)3Cl]. The IR spectroelectrochemistry for [Re(dbn)(CO)3Cl], [Re(dbq)(CO)3Cl], and [Re(bn)(CO)3Cl] reveal that reduction lowers the CO ligand vibrational frequencies to a similar extent in all three complexes. The substitution of naphthyridine for quinoline has little effect on the nature of the singly occupied MO. These data are supported by DFT calculations on the reduced complexes, which reveal that the ligands are flattened out by reduction: This may explain the similarity in the properties of the reduced complexes.

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Section: Resultssupporting

confidence: 55%

The Effect of Reduction on Rhenium(I) Complexes with Binaphthyridine and Biquinoline Ligands: A Spectroscopic and Computational Study

et al. 2005

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“…This is evident in the spectra of the rhenium(I) complexes which show enhancement of the CO stretch. 37 The CO ligands attached to the rhenium centre show significant wavenumber shifts on going to the MLCT excited state, because the Re(I) centre becomes formally oxidized to Re(II). 38 The calculations performed previously 6,9,39 and reported herein suggest that the dppz ligand has ring-localized MOs that may accept charge and ring-localized vibrations.…”

Section: Resultssupporting

confidence: 49%

Electronic absorption, resonance Raman and excited-state resonance Raman spectroscopy of rhenium(I) and copper(I) complexes, with substituted dipyrido[3,2-a : 2′,3′-c]phenazine ligands, and their electron reduced products

Waterland

Gordon

2000

J. Raman Spectrosc.

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The electronic absorption and resonance Raman spectra of a series of rhenium(I) and copper(I) complexes with substituted dipyrido[3,2-a : 2 ,3 -c]phenazine (dppz) ligands were investigated. The ligands were benzo[i ]dipyrido[3,2-a : 2 ,3 -c]phenazine, 11,12-dimethyldipyrido[3,2-a : 2 ,3 -c]phenazine, 10-methyldipyrido[3,2-a : 2 ,3 -c]phenazine and 11-methyoxydipyrido[3,2-a : 2 ,3 -c]phenazine. The spectroelectrochemistry of the reduced complexes and the emission and resonance Raman spectra of the excited states are reported. Vibrational wavenumber calculations of the unsubstituted ligand suggest the presence of normal modes that are localized to various sections of the ligand structure; the resonance Raman spectra of the complexes are interpreted with reference to these calculations. The analysis of the spectra revealed that the Franck-Condon state initially formed by visible photoexcitation (450 nm) is metal-to-ligand charge-transfer in nature. Spectroelectrochemical resonance Raman and electronic absorption measurements revealed the spectral signatures for the radical anions of each of the ligands used in this study. These spectral features were used to assign the excited states formed by the complexes. Most of the complexes studied show spectral features in their excited-states that suggest that the predominant state formed within 5 ns of excitation is ligand-centred.a See Fig. 1 for numbering scheme. b The values in parentheses show the difference between the corresponding free ligand resonance, i.e. υ(complex) υ(ligand). c Insufficiently soluble in CDCl 3 to obtain a spectrum.

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“…This was handled by calculating the triplet structure for Re(pqx)(CO) 3 Cl, assuming that structure at least distorted in a similar direction to the resonant 1 MLCT state and used the observed bond length changes to derive plausible or at least consistent bond length distortions. This analysis is consistent with other experiments that have attempted to determine bond length changes, notably the work of Morrsion et al [91,92] in which the bond lengths for the CO ligands in metal carbonyls such as Re(CO) 3 (bpy)Cl were estimated using an empirical relationship of the form r CO = 1.6916-0.1736ln(k CO ) (r/Å, k/mdyn Å −1 ) akin to Badger's rule [93,94], and the shifts in the carbonyl vibration were found on going from the ground to 3 MLCT excited state. The study of Re(pqx)(CO) 3 Cl [90] demonstrates rather well the limitations of resonance Raman excitation profile studies in metal polypyridyl systems-although 2 may be established with reasonable confidence the ability to go beyond that and determine bond length and angle changes is somewhat limited and probably not generally applicable using transformation methods as outlined in this study.…”

Section: Linking Experimentally Determined Distortions With Dftsupporting

confidence: 88%

Understanding excited-state structure in metal polypyridyl complexes using resonance Raman excitation profiles, time-resolved resonance Raman spectroscopy and density functional theory

Horvath

Gordon

2010

Coordination Chemistry Reviews

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The estimation of CO bond length changes in the excited states of transition metal carbonyls

Cited by 20 publications

References 44 publications

The Effect of Reduction on Rhenium(I) Complexes with Binaphthyridine and Biquinoline Ligands: A Spectroscopic and Computational Study

The Effect of Reduction on Rhenium(I) Complexes with Binaphthyridine and Biquinoline Ligands: A Spectroscopic and Computational Study

Electronic absorption, resonance Raman and excited-state resonance Raman spectroscopy of rhenium(I) and copper(I) complexes, with substituted dipyrido[3,2-a : 2′,3′-c]phenazine ligands, and their electron reduced products

Understanding excited-state structure in metal polypyridyl complexes using resonance Raman excitation profiles, time-resolved resonance Raman spectroscopy and density functional theory

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