Long-Lived LMCT in a d⁰ Vanadium(V) Complex by Internal Conversion to a State of 3d_xy Character

Abstract

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=5da554e5-7ac2-43d0-bfc9-07b668c650eb http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=5da554e5-7ac2-43d0-bfc9-07b668c650eb ABSTRACT:The excited state dynamics of a d 0 vanadium(V) oxido ligand-tometal charge transfer (LMCT) complex, VOL F , were investigated via a combination of static optical and X-ray absorption (XAS) spectroscopy, transient optical absorption spectroscopy, and time-dependent density functional theory (TD-DFT). Upon excitation of the LMCT in the visible region, transient absorption data reveal that internal conversion traps the excited carrier population into a long-lived charge transfer state of 3d xy electron character, S 1 (d xy ). The internal conversion is substantiated by an isosbestic point in the transient absorption data, two nearby charge transfer states that couple well by TD-DFT, multiple rates in the ground state recovery, and the decay kinetics of an excited state absorption with the energy of a d-d transition in O K-edge XAS spectra. The long lifetime (∼420 ps) of S 1 (d xy ) can be ascribed to its poor optical and vibrational coupling to a distorted ground state (S 0 *) via a negligible electronic dipole transition in TD-DFT. The lack of luminescence or an identifiable triplet state also suggests attributing the lifetime to electronic contributions. In conjunction with its strong visible absorption and reduction potential, the long-lived LMCT suggests that molecules such as VOL F could have potential utility for energy conversion applications. Moreover, the results show that internal conversion between two nearby charge transfer states, differentiated by their 3d character, can form a long-lived charge transfer excitation, broadly informing the discovery of 3d metalcentered optical absorbers with long-lived charge transfer lifetimes.

Photoinduced Electron Transfer from ZrOCo Binuclear Light Absorber to Pyridine Elucidated by Transient Optical and Infrared Spectroscopy

“…[28][29][30] Due to the well-known shortcomings of DFT in computing electron transfer processes (electrons tend to be overly delocalized) and electronic transitions (time-dependent DFT is necessary to find transition probabilities), modeling complete binuclear units with organics on silica surfaces is beyond the scope of this work. 31,32 3. Results…”

“…Data averaging, fitting, and plotting were performed using scripts written in Python 3.5.2 through the Enthrough Canopy IDE (v.2.1.9) with the lmfit package (v.0.9.2.9) for nonlinear least-squares fitting . Density functional theory (DFT) geometric optimization and frequency calculations for neutral and radical pyridine species were performed using Q-Chem 4.3 running on an IBM System x3850 high-performance computer. − The density functionals B3LYP, BP86, and ωB97X-D were used with 6-31G*, 6-31++G**, and aug-cc-pVDZ basis sets. − Due to the well-known shortcomings of DFT in computing electron transfer processes (electrons tend to be overly delocalized) and electronic transitions (time-dependent DFT is necessary to find transition probabilities), modeling complete binuclear units with organics on silica surfaces is beyond the scope of this work. , …”

Emergence of ligand-to-metal charge transfer in homogeneous photocatalysis and photosensitization

“…In 2015, the Cuk, Weare, and co-workers described a combination of experimental and computational studies to probe a V V trigonal bipyramidal complex supported by oxo, phenoxide, and alkoxide donors. 45 The steady-state UV-visible spectrum showed an absorption maximum around 425 nm, which was deconvoluted into four LMCT transitions (S1* to S4*, vertical lines in Figure 2a) by TD-DFT calculations. 45 An example of the contributions of the S3* transition clearly illustrated the LMCT originating from the promotion of the electron from the phenoxy rings to the 3dyz and the 3dx2-y2 orbitals of V. To obtain additional detailed information about the electronic structure, they conducted elegant O K-edge X-ray absorption spectroscopic (XAS) experiments to estimate the ligand field gap in the complex (Figure 2b).…”

Long-Lived Mixed 2MLCT/MC States in Antiferromagnetically Coupled d3 Vanadium(II) Bipyridine and Phenanthroline Complexes

“…Unfortunately, the most popular dyes are derived from ruthenium­(II), iridium­(III), and rhenium­(I), which are expensive and rare. Consequently, there is interest in investigating earth-abundant first-row transition-metal complexes for photoredox activity. − Our groups have focused on examining and improving the excited-state (ES) properties of first-row iron­(II) and chromium­(III) polypyridyl complexes. − With specific relevance to the current work, [Cr­(bpy) 3 ] 3+ (bpy = 2,2′-bipyridine) and its derivatives have proven to be remarkably good photooxidants because of their large ES reduction potentials { E 0 ([Cr­(bpy) 3 ] 3+ * /2+ ) = 1.08 V vs ferrocenium/ferrocene} and long ES lifetimes . The latter property is a result of the spin-forbidden nature of the transition linking the lowest-energy ES (which is 2 E in the octahedral ligand-field designation) with the quartet ground state ( 4 GS) and the fact that both states (with nominal t 2g 3 configurations) are structurally similar, thereby inhibiting nonradiative relaxation pathways …”