scholarly journals Toward an understanding of electronic excitation energies beyond the molecular orbital picture

2020 ◽  
Vol 22 (11) ◽  
pp. 6058-6080 ◽  
Author(s):  
Patrick Kimber ◽  
Felix Plasser
Keyword(s):  
Molecular Orbital ◽  
Electronic Excitation ◽  
Excitation Energies ◽  
Molecular Picture

Can we gain an intuitive understanding of excitation energies beyond the molecular picture?

scholarly journals Toward an Understanding of Electronic Excitation Energies Beyond the Molecular Orbital Picture

2020 ◽  
Author(s):  
Patrick Kimber ◽  
Felix Plasser
Keyword(s):  
Molecular Orbital ◽  
Electronic Excitation ◽  
Triplet States ◽  
Central Research ◽  
Excitation Energies ◽  
Correlated Electron ◽  
Rough Approximation ◽  
Electron Hole Pair ◽  
Molecular Excitation ◽  
Excitation Processes

<pre><div><div><div><p>Tuning the energies of molecular excited states is a central research theme in modern chemistry with high relevance for optoelectronic applications and chemical synthesis. Whereas frontier orbitals have proven to be an intuitive and simple model in many cases, they can only provide a very rough approximation of the underlying wavefunctions. The purpose of this Perspective is to explore how our qualitative understanding of electronic excitation processes can be promoted beyond the molecular orbital picture by exploiting methods and insights from modern quantum chemistry. For this purpose, the physics of a correlated electron-hole pair is analysed in detail to show the origin of exchange repulsion and a dynamic Coulomb attraction, which determine its energy aside from the orbital energies. Furthermore, we identify and discuss the two additional effects of secondary orbital relaxation and de-excitations. Rules for reconstructing these four contributions from general excited-state computations are presented and their use is exem- plified in three case studies concerned with the relative ordering of the singlet and triplet ππ∗ and nπ∗ states of uracil, the large energetic differences between the first singlet and triplet states of the polyacenes, and the assignment of plasmonic states in octatetraene. Finally, we lay out some general ideas for how the knowledge gained could ultimately lead to new design principles for tuning molecular excitation energies as well as for diagnosing possible shortcomings of commonly used electronic structure methods.</p></div></div></div></pre>

scholarly journals Toward an Understanding of Electronic Excitation Energies Beyond the Molecular Orbital Picture

2020 ◽  
Author(s):  
Patrick Kimber ◽  
Felix Plasser
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Electronic Excitation ◽  
Triplet States ◽  
Central Research ◽  
Excitation Energies ◽  
Correlated Electron ◽  
Rough Approximation ◽  
Electron Hole Pair ◽  
Excitation Processes

<div><div><div><p>Tuning the energies of molecular excited states is a central research theme in modern chemistry with high relevance for optoelectronic applications and chemical synthesis. Whereas frontier orbitals have proven as an intuitive and simple model in many cases, they can only provide a very rough approximation of the underlying wavefunctions. The purpose of this Article is to explore how our qualitative understanding of electronic excitation processes can be promoted beyond the molecular orbital picture by exploiting methods and insights from modern quantum chemistry. For this purpose, the physics of a correlated electron-hole pair is analysed in detail to show the origin of exchange repulsion and a dynamic Coulomb attraction, which determine its energy aside from the orbital energies. Furthermore, we identify and discuss the two additional effects of secondary orbital relaxation and de-excitations. Rules for reconstructing these four contributions from general excited states computations are presented and their use is exemplified in three case studies. First, the relative ordering of the singlet and triplet ππ∗ and nπ∗ states of uracil is explained. Second, the large differences between the energies of the first singlet and triplet states of the polyacenes are examined. Third, the identification of plasmonic states in the case of octatetraene is explored. Finally, we lay out some general ideas for how the knowledge gained could ultimately lead to new design principles for tuning molecular excitation energies as well as for diagnosing possible shortcomings of commonly used electronic structure methods.</p></div></div></div>

scholarly journals Toward an Understanding of Electronic Excitation Energies Beyond the Molecular Orbital Picture

2020 ◽  
Author(s):  
Patrick Kimber ◽  
Felix Plasser
Keyword(s):  
Molecular Orbital ◽  
Electronic Excitation ◽  
Triplet States ◽  
Central Research ◽  
Excitation Energies ◽  
Correlated Electron ◽  
Rough Approximation ◽  
Electron Hole Pair ◽  
Molecular Excitation ◽  
Excitation Processes

<pre><div><div><div><p>Tuning the energies of molecular excited states is a central research theme in modern chemistry with high relevance for optoelectronic applications and chemical synthesis. Whereas frontier orbitals have proven to be an intuitive and simple model in many cases, they can only provide a very rough approximation of the underlying wavefunctions. The purpose of this Perspective is to explore how our qualitative understanding of electronic excitation processes can be promoted beyond the molecular orbital picture by exploiting methods and insights from modern quantum chemistry. For this purpose, the physics of a correlated electron-hole pair is analysed in detail to show the origin of exchange repulsion and a dynamic Coulomb attraction, which determine its energy aside from the orbital energies. Furthermore, we identify and discuss the two additional effects of secondary orbital relaxation and de-excitations. Rules for reconstructing these four contributions from general excited-state computations are presented and their use is exem- plified in three case studies concerned with the relative ordering of the singlet and triplet ππ∗ and nπ∗ states of uracil, the large energetic differences between the first singlet and triplet states of the polyacenes, and the assignment of plasmonic states in octatetraene. Finally, we lay out some general ideas for how the knowledge gained could ultimately lead to new design principles for tuning molecular excitation energies as well as for diagnosing possible shortcomings of commonly used electronic structure methods.</p></div></div></div></pre>

scholarly journals A Class of Non-Kekulé Molecules with Low Excitation Energies

2007 ◽  
Vol 62 (11) ◽  
pp. 1433-1436
Author(s):  
Fritz Dietz ◽  
Nedko Drebov ◽  
Nikolai Tyutyulkov
Keyword(s):  
Molecular Orbital ◽  
Ground State ◽  
Excitation Energies ◽  
Triplet Ground State ◽  
Molecular Systems ◽  
Structural Principle

A class of non-Kekulé molecular systems with a new structural principle and low excitation energies or with a triplet ground state was investigated theoretically. The systems consist of a non-Kekulé monoradical, possessing a non-bonding molecular orbital linked in a specific way to another monoradical.

Electronic Excitation Energies of ZniOiClusters

2003 ◽  
Vol 125 (31) ◽  
pp. 9494-9499 ◽  
Author(s):  
Jon M. Matxain ◽  
Jose M. Mercero ◽  
Joseph E. Fowler ◽  
Jesus M. Ugalde
Keyword(s):  
Electronic Excitation ◽  
Excitation Energies

Tensor Hypercontraction Equation-of-Motion Second-Order Approximate Coupled Cluster: Electronic Excitation Energies in O(N4) Time

2013 ◽  
Vol 117 (42) ◽  
pp. 12972-12978 ◽  
Author(s):  
Edward G. Hohenstein ◽  
Sara I. L. Kokkila ◽  
Robert M. Parrish ◽  
Todd J. Martínez
Keyword(s):  
Electronic Excitation ◽  
Equation Of Motion ◽  
Second Order ◽  
Coupled Cluster ◽  
Excitation Energies

Excitation Energies from a Partially Spin-Restricted Wave Function

2007 ◽  
Vol 3 (1) ◽  
pp. 65-69 ◽  
Author(s):  
V.N. Glushkov
Keyword(s):  
Wave Function ◽  
Excited States ◽  
Electron Correlation ◽  
Electronic Excitation ◽  
Slater Determinant ◽  
Molecular Orbitals ◽  
Reference Configuration ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Natural Base

A singe Slater determinant consisting of restricted and unrestricted, in spins, parts is proposed to construct a reference configuration for singlet excited states having the same symmetry as the ground one. A partially restricted Hartree-Fock approach is developed to derive amended equations determining the spatial molecular orbitals for singlet excited states. They present the natural base to describe the electron correlation in excited states using the wellestablished spin-annihilated perturbation theories. The efficiency of the proposed method is demonstrated by calculations of electronic excitation energies for the Be atom and LiH molecule.

Experimental and Theoretical Studies of 2- (naphthalen-1-yl (piperidin-1-yl) methyl)phenol Compound

2020 ◽  
Vol 42 (6) ◽  
pp. 818-818
Author(s):  
Yeliz Ula Yeliz Ula
Keyword(s):  
Molecular Orbital ◽  
Theoretical Data ◽  
Biologically Active ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Petasis Reaction ◽  
Vis Spectroscopy ◽  
Phenol Compound ◽  
Lowest Unoccupied Molecular Orbital ◽  
Experimental Values

The 2- (naphthalen-1-yl (piperidin-1-yl) methyl) phenol compound is an alkylaminophenol compound and has been experimentally synthesized by the Petasis reaction. In this study Structural analysis was carried out by FT-IR, NMR, UV-Vis spectroscopy. The high antioxidant value of the compound showed that it could be a potential biologically active drug. Theoretical data support all experimental analysis of the new compound. Comparisons were made by double method. For this purpose, DFT (B3LYP) and HF methods have been used with 6-311G ++ (d, p) set. Also, the compoundand#39;s electronic and structural properties (bond lengths, bond angles and dihedral angles), the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, electrostatic potential (MEP), vibrational frequencies, Mulliken atomic charges, excitation energies, and oscillator strengths were calculated. As a result; the theoretical and experimental values were found to be compatible.

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