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

Abstract

The electronic structure of a trigonally distorted vanadium(III) complex, [V(urea)6](ClO4)3, and its deuterated analogue, [V(urea-d4)6](ClO4)3 has been investigated with Raman, luminescence, and high-frequency high-field electron paramagnetic resonance spectroscopies and with magnetic measurements. A broad electronic Raman transition is observed at around 1400 cm(-1) and attributed to a transition to the (3)E (D3) component of the (3)T1g (O(h)) ground state. The same splitting is seen in the near-infrared luminescence spectrum in the form of a similarly broad peak at 8450 cm(-1), 1400 cm(-1) lower in energy than the (1)E --> (3)A2 spin-flip transition. Powder high-frequency and high-field electron paramagnetic resonance spectra, magnetic susceptibilities, and magnetization studies give a precise measurement of the zero-field splitting and of the g values in this complex (D = 6.00(2) cm(-1), E = 0.573(6) cm(-1), g(x) = 1.848(2), g(y) = 1.832(4), and g(z) = 1.946(7)). A set of angular overlap model parameters is proposed that reproduces all spectroscopic observations, and an analysis of the influence of the bonding of urea on the trigonal distortion of the complex is given.

Electronic structure of V3+ in NaMgAl(ox)3·9H2O probed by Fourier transform spectroscopy

“…An even weaker temperature-dependent vibronic sideband (shown with a Gaussian profile) was also detected below the origin that is mirrored by the vibronic absorption feature at 9635 cm À1 . We were unable to observe emission to the 3 Ê state component of the ground-state multiplet, which has been reported in other V 3+ compounds [2,8]. The measured luminescence decay time for the 2.9% V 3+ partially deuterated crystal was of the order of 450 ns at 4.0 K. The decay was nearly temperature independent below 20 K with a steady decrease above 20 K (see inset Fig.…”

“…Pseudooctahedral V 3+ has a 3 T 1g ground state that is difficult to study by classical electron resonance spectroscopy due to the large axial zero-field splitting (ZFS). Study of the ground-state electronic structures of integer-spin systems, like V 3+ , has received renewed attention in part due to the evolution of high field, high-frequency electron paramagnetic resonance (HFEPR) and inelastic neutron scattering spectroscopies [2][3][4][5].…”

“…Intra-configurational spin-forbidden d-d transitions, for V 3+ of the type 3 G(t 2g ) 2 -1 G(t 2g ) 2 , have negligible changes in geometry, and the resulting transition line widths can be of the order of 1 cm À1 , as for V 3+ in a-Al 2 O 3 [6,7]. A great deal of ground-state electronic structural information has been elucidated by studying these transitions using electronic absorption [7], luminescence [8], and Zeeman spectroscopies [6] for V 3+ in Al 2 O 3 , including the magnitude and sign of D and g-values.…”

A perspective on applications of ligand-field analysis: inspiration from electron paramagnetic resonance spectroscopy of coordination complexes of transition metal ions

“…24 Another locus of these older theories is the place where they were brought into full flower, Copenhagen, Denmark. The work by Jesper Bendix [25][26][27] and Høgni Weihe 28 and their co-workers in Copenhagen, together with Philip L. W. TregennaPiggott in Switzerland, [29][30][31][32][33][34][35][36][37] represent superb examples of state-of-the-art experimental (not only HFEPR, but also optical and vibrational spectroscopy, and most significantly, inelastic neutron scattering (INS) 31 ) and computational studies. In particular, Bendix has directly compared LFT to the current luminary, DFT.…”

Aminocarboxylate complexes of vanadium(III): Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy

“…This difficulty of observing EPR can be overcome by the use of high frequencies going into sub-THz and THz range (on the order of 100 cm À1 ) with correspondingly high resonant magnetic fields (up to 45 T in a continuous mode at the NHMFL in Tallahassee; higher fields operated in a pulsed mode are used at the NHMFL operation in Los Alamos, and elsewhere [13]). This technique is referred to as HFEPR and has been successfully applied to a wide variety of non-Kramers systems [14,15], including V(III) [16][17][18][19][20][21]. All of these systems were studied in the solid state, usually as a pure powder, although in some cases as a doped single crystal [17,19].…”