Electronic Raman spectroscopy of the vanadium(III) hexaaqua cation in guanidinium vanadium sulphate: Quintessential manifestation of the dynamical Jahn–Teller effect

Abstract

Single-crystal Raman spectra are presented for the salt [C(NH2)3][V(OH2)6](SO4)2, displaying electronic transitions between the trigonal components of the vanadium(III) 3T1g(Oh) ground term. The 3A-->3E(C3) electronic Raman band is centered at approximately 2720 cm-1, and exhibits extensive structure, revealing the energies of the spinor components of the 3E(C3) term for the two crystallographically distinct [V(OH2)6]3+ cations. The data are interpreted in conjunction with parameters previously reported from an electron paramagnetic resonance study of the salt. A satisfactory reproduction of the electronic Raman profile and ground-state spin-Hamiltonian parameters is achieved by employing a (3A plus sign in circle3E)multiply sign in circle e vibronic coupling model, in which the spin-orbit splitting of the 3E(C3) is quenched significantly by the Ham effect, and the intensity of harmonics of the Jahn-Teller active vibration enhanced by their proximity to the electronic Raman bands. The model gives an excellent account of the intensities of the electronic Raman bands, which are shown to depend profoundly on both temperature and the selected component of the polarizability tensor. The electronic Raman profile changes notably upon deuteriation, a result that exposes deficiencies in the single-mode coupling model.

Adding Remnant Magnetization and Anisotropic Exchange to Propeller‐like Single‐Molecule Magnets through Chemical Design

“…This quite small value, which lies at the lowest end of the reported literature range for vanadium(III),34 may suggest a non‐negligible role of the vibronic coupling, which has been demonstrated to lead to a decrease of g z and to an increase of g x,y compared with the static case 26b. 35 Substituting into Equation (12) standard values of P =1.25, k =0.8, and λ =75 cm −1 gives an estimated trigonal splitting for the vanadium(III) ion of about 300 cm −1 ; thus, extremely small.…”

The Electronic Ground State of [V(urea)6]3+ Probed by NIR Luminescence, Electronic Raman, and High-Field EPR Spectroscopies

“…This band, absent from the spectra of the uncoordinated ligands, is too broad and too high in energy to be a metal−ligand vibration and is assigned to an electronic Raman transition between two components of the electronic ground state. Such transitions are not uncommon in six-coordinated complexes of vanadium(III). ,,− In contrast to peaks corresponding to vibrational transitions, the electronic band shows a significant decrease of intensity and becomes broader with increasing temperature for both [V(urea) 6 ](ClO 4 ) 3 and [V(urea- d 4 ) 6 ](ClO 4 ) 3 2 Solid-state Raman spectra of urea- d 4 , [V(urea- d 4 ) 6 ](ClO 4 ) 3 , [V(urea) 6 ](ClO 4 ) 3 , and urea, at 77 K. Asterisks denote vibrations of the perchlorate anion.…”

“…The electronic structure of octahedral coordination compounds containing transition-metal ions with the d 2 configuration is a classic case used to present ligand-field theory − and has been probed for more than 50 years with a variety of experimental techniques. − One area of current interest is the use of these complexes for near-infrared (NIR) to visible upconversion of light, illustrating the need for a detailed determination of their electronic structure, an aspect of key importance for understanding these phenomena. The characterization of low-lying electronic states of many transition metal complexes is challenging, from both experimental − and theoretical − perspectives. This challenge is illustrated by the study of deceptively simple complexes, such as [V(H 2 O) 6 ] 3+ , for which new insight on the interplay between ligand coordination and the electronic structure of metal-centered states has been obtained. − ,, …”

“…The characterization of low-lying electronic states of many transition metal complexes is challenging, from both experimental − and theoretical − perspectives. This challenge is illustrated by the study of deceptively simple complexes, such as [V(H 2 O) 6 ] 3+ , for which new insight on the interplay between ligand coordination and the electronic structure of metal-centered states has been obtained. − ,, …”

“…[5][6][7][8][9][10][11][12] One area of current interest is the use of these complexes for near-infrared (NIR) to visible upconversion of light, 13 illustrating the need for a detailed determination of their electronic structure, an aspect of key importance for understanding these phenomena. The characterization of low-lying electronic states of many transition metal complexes is challenging, from both experimental [14][15][16][17][18] and theoretical [19][20][21][22][23][24] perspectives. This challenge is illustrated by the study of deceptively simple * To whom correspondence should be addressed.…”