Hole delocalization in oxidized cerium(IV) porphyrin sandwich complexes

Electronic structure, molecular structure, and electronic spectra of lanthanide III mono-and bisporphyrin complexes are investigated using a DFT/TDDFT method. These complexes include YbP (acac), YbP 2 , [YbP 2 ] + , YbHP 2 , and [YbP 2 ] − (where P = porphine and acac = acetylacetonate). To shed some light on the origin of the out-of-plane displacement of Yb in YbP(acac), unligated model systems, namely planar D 4h and distorted C 4v YbP, were calculated. For comparison, the calculations were also extended to include the Ce IV P 2 and [Ce IV P 2 ] + systems. Even without an axial ligand, the lanthanide atom lies considerably above the porphyrin plane; the distortion of the YbP molecular structure from a planar D 4h to the non-planar C 4v symmetry leads to a considerable energy lowering. The axial ligand makes the metal out-of-plane displacement even larger, and it also changes the redox properties of the lanthanide mono-porphyrin. The ground state configurations of YbP 2 and YbHP 2 were determined by considering several possible low-lying states. YbP 2 is confirmed to be a singlehole radical. The special redox properties of the bis-porphyrin complexes can well be accounted for by the calculated ionization potentials and electron affinities. The TDDFT results provide a clear description of the UV-visible and near-IR absorption spectra of the various lanthanide porphyrins.

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“…21 In the cation π-radical, the 5b 1 → 5a 2 transition results in a strong near-IR absorption feature, similar to the situation for Yb(Por) 2 …”

Section: Ybp 2 -Experimental Spectral Data Are Available For Yb(oep)mentioning

confidence: 53%

DFT/TDDFT Study of Lanthanide^III Mono- and Bisporphyrin Complexes

2006

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“…This implies that statistical hole localization is not sensible. Results of NMR, ENDOR [19] and resonance Raman spectrum [48] measurements on bis-porphyrin analogues have given supportive data for delocalization of the hole over the two rings.…”

Section: Hole Delocalization In Pc Dimer Radicalsmentioning

confidence: 80%

Electronic structures and spectral properties of double- and triple-decker phthalocyanine complexes in a localized molecular orbital view

Ishikawa

2001

J. Porphyrins Phthalocyanines

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This paper reviews the studies on the electronic structures and spectroscopic properties of sandwich-type complexes M ( Pc )2 and M 2( Pc )3. The subjects discussed are as follows. (1) Electronic spectra of closed-shell Pc dimers and trimers. The complexes with closed-shell systems, such as [ Lu ( Pc )2]−, Sn ( Pc )2 and Lu 2( Pc )3, can be thought of as stacked systems composed only of Pc 2−. The excited states of these complexes can be described by locally excited and charge transfer configurations. The coupling terms of the configurations are written using orbitals localized on each Pc ring. Assignments of the observed absorption bands are discussed. Computational studies on the band assignments were carried out using a localized molecular orbital (LO) basis which maximizes orbital populations on one of the Pc rings. (2) Electronic structures of πelectron-deficient Pc dimers and trimers. Oxidation of [ Lu ( Pc )2]− or Lu 2( Pc )3 yields systems with π-electron deficiency or π-hole(s) residing on multiple Pc sites. The delocalized nature of the π-hole in Lu ( Pc )2 is elucidated by comparison of the electronic spectra of symmetric and asymmetric dimers composed of Pc and Nc ( H 2 Nc ≡ naphthalocyanine ). The band assignments of the dimer radicals are discussed. The Pc trimer radical shows an intense absorption band at about 5000 cm−1, which is 2000 cm−1 lower than the valence resonance band of Lu ( Pc )2. The two-electron-deficient complexes [ Lu ( Pc )2]+ and [ Lu 2( Pc )3]2+ also show intense near-IR bands at higher energy than the corresponding monoradical species. The interactions that determine the excitation energies of the near-IR bands of the π-electron-deficient species are elucidated.

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“…Therefore, an NIR absorption band was observed at 1153 nm, in addition to the blue shi of the Soret peak of the radical form 3 (387 nm) relative to those of the BDP ligand (404 nm), protonated form 1 (392 nm), and anionic form 2 (396 nm). In the radical form 3, the cofacial distance between the two porphyrin rings decreases because of an increase in the bond order, due to the removal of an electron from the antibonding orbital of the HOMO, [69][70][71][72][73] ultimately resulting in blue-shiing of the Soret band of 3 (Fig. S3 †).…”

Section: Uv-vis Spectroscopic Measurements Of Tb III -Porphyrin Bdp Cmentioning

confidence: 99%