Theoretical Studies of Observable Transitions to Recoupled Pair Bonded
States of Sulfur Halide CompoundsJeff Leiding, D. E. Woon, T. H. Dunning, Jr.
University of Illinois
SF/SCl, SF2/SFCl/SCl2
Motivation for Current Work
SF2: Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2009, 113, 7915.SFCl: Leiding, J.; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 329.SCl2: Leiding, J; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 4757.
a4Σ-
X2Πσ*π*π*
Motivation for Current Work
SF2: Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2009, 113, 7915.SFCl: Leiding, J.; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 329.SCl2: Leiding, J; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 4757.
a4Σ-
X2Πσ*π*π*
Spin-forbidden
Motivation for Current Work
SF2: Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2009, 113, 7915.SFCl: Leiding, J.; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 329.SCl2: Leiding, J; Woon, D. E.; Dunning, T. H., Jr. J. Phys. Chem. A 2011, 115, 4757.
a4Σ-
A2Σ-
X2Πσ*π*π*
Spin-forbidden
Spin-allowed
Methods
•CASSCF/MRCI+Q•aug-cc-pV(5+d)Z for diatomics•aug-cc-pV(Q+d)Z for triatomics•Transform CAS orbitals into GVB orbitals: singly occupied, atom-centered
CASSCF: Complete active space self-consistent fieldMRCI: Multireference configuration interactionGVB: Generalized valence bond
Low-Lying States of SClSCl(a4Σ-)SCl(X2Π)
Low-Lying States of SClSCl(a4Σ-)SCl(X2Π)
Low-Lying States of SClSCl(a4Σ-)SCl(X2Π)
No experimental data for excited states of SCl/SF
Covalent SCl(X2Π) GVB Orbitals
SCl(a4Σ-) GVB Orbitals
Recoupled SCl(2,4Σ-)
GVBL GVBR
re(4Σ-) orbs
2,4Σ- orbs coupled
coupled
MO/GVB
Recoupled SCl(2,4Σ-)
antibonding
GVBL GVBR
re(4Σ-) orbs
2,4Σ- orbs coupled
coupled
MO/GVB
4Σ- : “Recoupled pair bond”
Recoupled SCl(2,4Σ-)
antibonding
GVBL GVBR
re(2Σ-) orbs
re(4Σ-) orbs
2,4Σ- orbs coupled
coupled
coupled
MO/GVB
2Σ- : “Frustrated recoupled pair bond”
4Σ- : “Recoupled pair bond”
Low-Lying Triatomic States
SX(2Π)
SX(2Σ-)
1. Li et al. J. Phys. Chem. A 1998, 102, 7233.2. Colton et al. J. Elec. Spec. Relat. Phenom. 1974, 3, 345.3. Gholivand, K. et al. Phosphorus, Sulfur and Silicon, 1996, 1, 269.
Low-Lying Triatomic States
SX2(1A1)SX(2Π)
SX(2Σ-)
1. Li et al. J. Phys. Chem. A 1998, 102, 7233.2. Colton et al. J. Elec. Spec. Relat. Phenom. 1974, 3, 345.3. Gholivand, K. et al. Phosphorus, Sulfur and Silicon, 1996, 1, 269.
Low-Lying Triatomic States
SX2(1A1)
SX2(1B1)
SF2 singly occupied orbitals
SF2(1B1)
SX(2Π)
SX(2Σ-)
Te, Tv (eV)1. Li et al. J. Phys. Chem. A 1998, 102, 7233.2. Colton et al. J. Elec. Spec. Relat. Phenom. 1974, 3, 345.3. Gholivand, K. et al. Phosphorus, Sulfur and Silicon, 1996, 1, 269.
2.3
Low-Lying Triatomic States
SX2(1A1)
SX2(1B1)
SX2(1A2)SF2 singly occupied orbitals
SF2(1A2)
SF2(1B1)
SX(2Π)
SX(2Σ-)
Te, Tv (eV)1. Li et al. J. Phys. Chem. A 1998, 102, 7233.2. Colton et al. J. Elec. Spec. Relat. Phenom. 1974, 3, 345.3. Gholivand, K. et al. Phosphorus, Sulfur and Silicon, 1996, 1, 269.
2.3
0.7
Low-Lying Triatomic States
SX2(1A1)
SX2(1B1)
SX2(1A2)SF2 singly occupied orbitals
SF2(1A2)
SF2(1B1)
SX(2Π)
SX(2Σ-)
Te, Tv (eV)1. Li et al. J. Phys. Chem. A 1998, 102, 7233.2. Colton et al. J. Elec. Spec. Relat. Phenom. 1974, 3, 345.3. Gholivand, K. et al. Phosphorus, Sulfur and Silicon, 1996, 1, 269.
2.3
0.7
SFCl Bond-Stretch Isomers
F-recoupled
Cl-recoupled
SFCl(A1A″): Minima on same PES
SFCl Bond-Stretch Isomers Singly occupied orbitals
∆E=9.0 kcal/mol
1.594 Å
θ=86.9º2.421 Å
1.912 Å
1.962 Å θ=88.5º
F-recoupled
Cl-recoupled
SFCl(A1A″): Minima on same PES
(PES for a3A″)
SFCl Bond-Stretch Isomers Singly occupied orbitals
∆E=9.0 kcal/mol
1.594 Å
θ=86.9º2.421 Å
1.912 Å
1.962 Å θ=88.5º
We predict observable signature of bond-stretch isomerism due to recoupled-pair bonding:
“1A2” line will split.
F-recoupled
Cl-recoupled
fe=oscillator strengthEnergies (eV)
SFCl(A1A″): Minima on same PES
(PES for a3A″)
Conclusions
1.RPB exhibited in low-lying states of SF/SCl and SF2/SFCl/SCl2
2.Understand excited state behavior via RPB model3.Good agreement of excited state observables with
experiment4.Predictions for excited states of SF/SCl and
SF2/SFCl/SCl25.Possibility of observing electronic signature of
bond-stretch isomers in SFCl via electronic spectroscopy
Acknowledgements• Professor Thom Dunning• Dr. David Woon• Dr. Lina Chen• Dunning Group• Funding: NCSA, Distinguished Chair for Research Excellence in
Chemistry
Low-Lying triatomic states (Te)
SX2(1A1)
SX2(1B1)
SX2(1A2)
Low-Lying triatomic states (Te)
Excitation energies (kcal/mol)
Singlet-Triplet gap (kcal/mol)
52.9
20.3
16.2
SCl2SF2
50.2
14.5
18.513.3
20.0
SX2(1A1)
SX2(1B1)
SX2(1A2)
Relaxed geometries
1A1 geometries
SCl2(1B1) SF2(1B1)
unfavorable
Low-Lying triatomic states (Tv,Te)
Molecule State Method Te Tv
SF2 1B1 Theo 53.0 119.3
1A2 Theo 69.1 82.0
SCl2 1B1 Theo 50.2 78.4
1A2 Theo 70.3 83.3
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