Excited states of titanium(2+):  sharp-band and broad-band near-infrared luminescence from titanium(2+) in magnesium chloride and magnesium bromide

Jacobsen, Stuart M.; Guedel, Hans U.; Daul, Claude

doi:10.1021/ja00231a005

Cited by 43 publications

(57 citation statements)

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“…The 3 T 1g (F) → 3 A 2g transition was not observed for Ti II :MgBr 2 . 132 For visual comparison between Ti II :MgCl 2 and trans-[(py) 4 TiCl 2 ], we show in Figure 2 a Tanabe−Sugano diagram generated using the LFT parameters derived for the latter complex (vide inf ra). Not all transitions observed by Jacobsen et al are depicted, 132 but the relationship between the two systems in the context of electronic transitions in octahedral d 2 complexes can be readily seen.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Specifically, band 4 would arise from the 3 A 2g excited state, with bands 5 and 6, which consist of a pseudo-A term centered at 18 800 cm −1 , due to the second 3 E g excited state. The MCD features above 23 000 cm −1 would 132 Moreover, the Ti(II) ion had homoleptic chlorido hexacoordination with only a small magnitude trigonal distortion (calculated as V trig = −246 cm −1 , using only the 3 T 1g levels). It was thus possible using LFT to match perfectly all of the excited states of this system.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

“…These LFT parameters can be compared to those obtained for Ti: MgCl 2 : B = 527 (74% of the free-ion value), C = 1983 (C/B = 3.76), Dq = 1018, Dσ = +281, Dτ = −142. 132 The greater covalency in the molecular complex, trans-[(py) 4 TiCl 2 ], as well as its heteroleptic coordination, leads to lower Racah parameters and overall larger magnitude crystal-field parameters with a greater distortion from an octahedral field.…”

Section: Inorganic Chemistrymentioning

confidence: 99%

“…Thus, use of LFT, whether with a crystal-field or AOM parametrization, provides a reasonable explanation of the optical spectra of trans-[(py) 4 TiCl 2 ], analogous to, albeit less precise than, the crystal-field analysis of Ti:MgCl 2 . 132 Quantum Chemistry Theory (DFT and CASSCF/ NEVPT2) Electronic Structure Computations. We next turn to more sophisticated QCT calculations, the likes of which were unavailable to Jacobsen et al 132 (and likely would still be a challenge for an extended solid system).…”

Section: Inorganic Chemistrymentioning

confidence: 99%

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Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

et al. 2015

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A facile and high-yielding protocol to the known Ti(II) complex trans-[(py)4TiCl2] (py = pyridine) has been developed. Its electronic structure has been probed experimentally using magnetic susceptibility, magnetic circular dichroism, and high-frequency and high-field electron paramagnetic resonance spectroscopies in conjunction with ligand-field theory and computational methods (density functional theory and ab initio methods). These studies demonstrated that trans-[(py)4TiCl2] has a (3)Eg ground state (dxy(1)dxz,yz(1) orbital occupancy), which, as a result of spin–orbit coupling, yields a ground-state spinor doublet that is EPR active, a first excited-state doublet at ∼60 cm(–1), and two next excited states at ∼120 cm(–1). Reactivity studies with various unsaturated substrates are also presented in this study, which show that the Ti(II) center allows oxidative addition likely via formation of [Ti(η(2)-R2E2)Cl2(py)n] E = C, N intermediates. A new Ti(IV) compound, mer-[(py)3(η(2)-Ph2C2)TiCl2], was prepared by reaction with Ph2C2, along with the previously reported complex trans-(py)3Ti═NPh(Cl)2, from reaction with Ph2N2. Reaction with Ph2CN2 also yielded a new dinuclear Ti(IV) complex, [(py)2(Cl)2Ti(μ2:η(2)-N2CPh2)2Ti(Cl)2], in which the two Ti(IV) ions are inequivalently coordinated. Reaction with cyclooctatetraene (COT) yielded a new Ti(III) complex, [(py)2Ti(η(8)-COT)Cl], which is a rare example of a mononuclear “piano-stool” titanium complex. The complex trans-[(py)4TiCl2] has thus been shown to be synthetically accessible, have an interesting electronic structure, and be reactive toward oxidation chemistry.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

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Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

et al. 2015

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“…[4][5][6] The d 2 spin-flip transition energies are expected to be slightly reduced with respect to the corresponding 1 D→ 3 F free ion values due to the so called nephelauxetic effect, 1 which has been interpreted as a consequence of the radial expansion of the 3d orbitals in the crystal field; however, Brunold et al 4 have observed a very irregular trend of this reduction at the end of the mentioned Ti͑III͒-Fe͑VI͒ series, together with a very unusual, tremendous decrease observed in K 2 CrO 4 :Fe 6ϩ , where the 1 E -3 A 2 energy difference is shown to be less than 40% of the 1 D -3 F free Fe͑VI͒ value. 4 These experimental results deserve some explanation.…”

Section: Introductionmentioning

confidence: 99%

A new interpretation of the bonding and spectroscopy of the tetraoxoferrate(VI) FeO42− ion

Al-Abdalla¹,

Seijo²,

Barandiarán³

1998

The Journal of Chemical Physics

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In this paper we present an ab initio study of the absorption spectrum of the FeO 4 2Ϫ ion. The wavefunctions and energies of the ground and excited states of the FeO 4 2Ϫ cluster are calculated by means of the Restricted Active Space self-consistent-field method ͑RASSCF͒. The molecular orbitals of the cluster with main character Fe(3d) define a complete active space; all single, double, triple, and quadruple excitations from the molecular orbitals of main character O(2p) to those of main character Fe(3d) are allowed. The multiconfigurational expansions resulting from these ligands-to-metal excitations include between 50000 to 100000 configuration state functions. The results of the calculations lead to a new interpretation of the bonding and of the absorption spectra of FeO 4 2Ϫ ͑which were observed in the solid state and in solution͒, both of them stem from the near degeneracy between Fe(3d) and O(2 p) levels, which is ultimately due to the high and unstable oxidation state of Fe͑VI͒ in the FeO 4 2Ϫ complex. The analysis of the ground and excited state wavefunctions reveals that the electronic structure of FeO 4 2Ϫ does not correspond to the ionic image of Ligand Field Theory ͓d 2 -Fe͑VI͒ϩclosed-shell O 2Ϫ ions͔, nor does it correspond to simple extensions of it which take into account ligands-to-metal 2 p→3d single excitations, nor to any other simple image; on the contrary, it corresponds to the superposition of a large number of configurations with a very large weight of high-order ligands-to-metal excitations, which indicates a remarkable intra-cluster inwards delocalization of electron density away from the closed-shell ligands, impelled by the unstable high formal charge of Fe͑VI͒. The calculated absorption spectrum allows for a thorough interpretation of the features observed in the experimental spectra measured in Fe͑VI͒-doped K 2 MO 4 ͑MϭS, Cr͒ and in 9 M KOH solution ͑absorption maxima, intensities, electronic origins, band shapes͒, which implies completely new assignments. This is particularly so for the broad intense bands observed between 10000-25000 cm Ϫ1 , which, according to our calculations, are found to be associated to electronic transitions from the 3 A 2 ground state to increasingly dense sets of excited states that include not only spin singlet and triplet states ͑as expected for a d 2 configuration from Ligand Field Theory͒, but also spin quintet electronic states, all of which can be understood as direct effects of the above-mentioned oxygens(2p)-iron(3d) near degeneracy.

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ChemInform Abstract: Excited States of Titanium(2+): Sharp‐Band and Broad‐Band Near‐Infrared Luminescence from Ti2+ in MgCl2 and MgBr2.

1989

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Absorption and luminescence spectral investigations of Ti2+(3d2) doped into the MgCl2 host show a sharp-band near-IR emission at low temp. with a radiative decay time of 109 ms. From the sharp emission an accurate determination of the energy splitting within the 3T1g(Oh) ground state of Ti2+ in this crystal environment is obtainable. Besides the near-IR emission Ti2+:MgCl2 exhibits a broad-band emission, which dominates above 70 K. In the bromide host a broad-band near-IR luminescence at low temp. with a decay time of 750 µs is observed. A combination of the spectroscopic results with lifetime measurements as a function of temp. leads to radiative and nonradiative mechanisms for both systems.

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Excited states of titanium(2+): sharp-band and broad-band near-infrared luminescence from titanium(2+) in magnesium chloride and magnesium bromide

Cited by 43 publications

References 0 publications

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II)

A new interpretation of the bonding and spectroscopy of the tetraoxoferrate(VI) FeO42− ion

ChemInform Abstract: Excited States of Titanium(2+): Sharp‐Band and Broad‐Band Near‐Infrared Luminescence from Ti2+ in MgCl2 and MgBr2.

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