An experimental and theoretical study into the valence electronic structure of bicyclo[2.2.1]hepta-2,5-dione

Abstract

The results from an electron momentum spectroscopy (EMS) study of the outer valence electronic region of bicyclo[2.2.1]hepta-2,5-dione (C7H8O2) are reported for the first time. The measured binding energy spectra are presented for the azimuthal angles 0°, 10° and 0° + 10°, respectively, and are compared to new He(I) photoelectron spectroscopy results, which are measured as a part of this work. These experimental data are compared further with results from theoretical computations, using various methods including Hartree–Fock, density functional and an outer valence Green's function theory. Measured orbital momentum distributions are compared on an orbital by orbital basis against those obtained by calculations which employ the plane-wave impulse approximation. These calculations use orbital wavefunctions obtained from Hartree–Fock and density functional theory with a couple of generalized gradient approximation exchange correlation (XC) functionals and the DGauss triple zeta valence polarization basis set. Agreement between the measured and calculated momentum distributions was found to be only fair. Nonetheless, the orbital momentum distributions of the molecule still provide an orbital based assessment of the XC functionals of the density functional theory employed, and an understanding of the chemical bonding mechanisms within the species. Finally, the spectroscopic strengths calculated using outer valence Green's function theory are compared against those derived from our EMS measurements.

New Diagnostic of the Most Populated Conformer of Tetrahydrofuran in the Gas Phase

“…In addition, in a most recent EMS measurement for bicyclo[2.2.1]hepta-2,5-dione from one of the world's leading EMS groups, the overlaps between the binding energy spectra at either φ = 0° and φ ≠ 0° in the band of 11−15 eV of bicyclo[2.2.1]hepta-2,5-dione are more significant than the present study. However, the unique assignment of the EMS binding energy spectra (Figure in ref ) was achieved with the help of higher resolution PES spectra as well as quantum mechanical calculations.…”

“…Dual space analysis (DSA) 17 is employed in the present work. Information obtained in position and momentum spaces is complementary, and they are connected by the uncertainty principle, which in one-electron systems may be interpreted as a statement about the correlation between measurement of the coordinates r and momenta p. The mutual information density in momentum space illustrates that this localization is accompanied by strong correlation at small values of p. 30 Momentum space information such as orbital momentum distributions [30][31][32][33][34][35] and momentum space maps 36 are particularly convenient for the determination of contributions to a given molecular orbital from orbitals associated with particular atoms. 30 Electronic structural calculations for the ground state of tetrahydrofuran with a C s symmetry (X 1 A′), a C 2 symmetry (X 1 A), and a C 1 symmetry (X 1 A) are performed using three parallel quantum mechanical modelssB3LYP, OVGF, and SAOP.…”

Experimental and Theoretical Electron Momentum Spectroscopic Study of the Valence Electronic Structure of Tetrahydrofuran under Pseudorotation

“…EMS features in the binding energy spectra as well as the ability of orbital images. When combined with quantum mechanics, EMS provides additional information of orbital-based valence electronic structures to the majority of energy focused approaches. − Previous studies have established that EMS is an attractive technique to investigate conformations of organic molecules and small biomolecules. − ,− It has been demonstrated that the symmetries of the HOMOs with respect to the minimal structures of C s and C 2 on the potential-energy surface (PES) produced by pseudorotation differentiate the conformers of THF . This finding is further supported by a detailed theoretical analysis of the individual valence orbitals of the three important structures, C s , C 2 , and C 1 produced by pseudorotation of THF .…”

“…[19][20][21][22][23][24][25][26][27] Previous studies have established that EMS is an attractive technique to investigate conformations of organic molecules and small biomolecules. [17][18][19][20][21][28][29][30][31][32][33] It has been demonstrated that the symmetries of the HOMOs with respect to the minimal structures of C s and C 2 on the potential-energy surface (PES) produced by pseudorotation differentiate the conformers of THF. 17 This finding is further supported by a detailed theoretical analysis of the individual valence orbitals of the three important structures, C s , C 2 , and C 1 produced by pseudorotation of THF.…”

“…When combined with quantum mechanics, EMS provides additional information of orbitalbased valence electronic structures to the majority of energy focused approaches. [19][20][21][22][23][24][25][26][27] Previous studies have established that EMS is an attractive technique to investigate conformations of organic molecules and small biomolecules. [17][18][19][20][21][28][29][30][31][32][33] It has been demonstrated that the symmetries of the HOMOs with respect to the minimal structures of C s and C 2 on the potential-energy surface (PES) produced by pseudorotation differentiate the conformers of THF.…”