Spin density and orbital optimization in open shell systems: A rational and computationally efficient proposal

2016 ◽  
Vol 144 (10) ◽  
pp. 104104 ◽  
Author(s):  
Emmanuel Giner ◽  
Celestino Angeli
Keyword(s):  
Spin Density ◽  
Open Shell ◽  
Computationally Efficient ◽  
Orbital Optimization

scholarly journals Linear Response Functions of Densities and Spin Densities for Systematic Modeling of the QM/MM Approach for Mono- and Poly-Nuclear Transition Metal Systems

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 821
Author(s):  
Colin Kitakawa ◽  
Tomohiro Maruyama ◽  
Jinta Oonari ◽  
Yuki Mitsuta ◽  
Takashi Kawakami ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Transition Metal ◽  
Spin Density ◽  
Linear Response ◽  
Transition Metal Ions ◽  
Open Shell ◽  
Reaction Centers ◽  
Oxygen Evolving ◽  
The Relationship ◽  
Spin Densities

We applied our analysis, based on a linear response function of density and spin density, to two typical transition metal complex systems-the reaction centers of P450, and oxygen evolving center in Photosystem II, both of which contain open-shell transition metal ions. We discuss the relationship between LRF of electron density and spin density and the types of units and interactions of the systems. The computational results are discussed in relation to quantum mechanics (QM) cluster and quantum mechanics/molecular mechanics (QM/MM) modeling that are employed to compute the reaction centers of enzymes.

Oxophenalenoxyl: Novel stable neutral radicals with a unique spin-delocalized nature depending on topological symmetries and redox states

2008 ◽  
Vol 80 (3) ◽  
pp. 507-517 ◽  
Author(s):  
Yasushi Morita ◽  
Shinsuke Nishida ◽  
Junya Kawai ◽  
Takeji Takui ◽  
Kazuhiro Nakasuji
Keyword(s):  
Spin Density ◽  
Open Shell ◽  
Two Stage ◽  
Neutral Radical ◽  
Redox States ◽  
Density Distributions ◽  
Alternant Hydrocarbon ◽  
Redox Ability ◽  
Unique Spin ◽  
Oxygen Atoms

Stable organic open-shell systems have attracted much attention in the field of molecule-based magnetism. We have been exploring novel stable neutral radicals based on a phenalenyl system known as an odd-alternant hydrocarbon π-radical with a highly spin-delocalized nature. Recently, we have designed and synthesized novel oxophenalenoxyl neutral radical systems possessing two oxygen atoms on the phenalenyl skeleton. These systems are unique in comprising some topological isomers depending on the positions of oxygen substituents on the phenalenyl skeleton. The isomers exhibit different topological symmetries of spin density distributions (spin topological symmetry control). In addition, two-stage one-electron reductions of these systems give the corresponding radical dianions, which show remarkably different topological symmetries of a spin-delocalized nature from those of the neutral radical systems (redox-based spin diversity). In this paper, we discuss the unique spin-delocalized nature of 3-, 4-, and 6-oxophenalenoxyl systems in view of the topological symmetry and redox ability, emphasizing the results from the radical dianion of 4-oxophenalenoxyl system from both experimental and theoretical sides.

scholarly journals Stable Carbon-Centered Radicals Based on N-Heterocyclic Carbenes

Synlett ◽  
2019 ◽  
Vol 30 (15) ◽  
pp. 1765-1775 ◽  
Author(s):  
Rajendra S. Ghadwal
Keyword(s):  
Rational Choice ◽  
Spin Density ◽  
Open Shell ◽  
Heterocyclic Carbenes ◽  
Structure And Properties ◽  
Stable Carbon ◽  
Aryl Group ◽  
New Class ◽  
Diradical Character ◽  
Density Delocalization

Carbon-centered radicals and diradicaloids based on classical N-heterocyclic carbene (NHC) scaffolds are readily accessible as crystalline solids. The presence of an aryl (Ar) substituent at the C2-position is the key to the remarkable stability of these open-shell species as it provides appropriate room for the spin-density delocalization. Two catalytic as well as high-yielding protocols have been developed to install a suitable aryl group at the C2-position of NHCs. The spin-density in mono-radicals (NHCAr)• is mostly located on the parent carbene carbon (C2) atom. The bridging of two NHCs through a phenylene spacer (C6H4) n enables the isolation of various p-quinodimethane (p-QDM) derivatives, which may be considered as open-shell Kekulé diradicaloids. The diradical character of these NHC-analogues of Thiele (n = 1), Chichibabin (n = 2), and Müller (n = 3) hydrocarbons [(NHC)(C6H4) n (NHC)] can be tuned by a rational choice of the size and/or the topology of spacers. In this account, the synthesis, structure, and properties of this new class of radical hydrocarbons is presented.1 Introduction2 NHC-Monoradicals3 NHC-Diradicaloids4 Conclusion

scholarly journals Importance of Orbital Optimization for Double-Hybrid Density Functionals: Application of the OO-PBE-QIDH Model for Closed- and Open-Shell Systems

2016 ◽  
Vol 120 (10) ◽  
pp. 1756-1762 ◽  
Author(s):  
J. C. Sancho-García ◽  
A. J. Pérez-Jiménez ◽  
M. Savarese ◽  
E. Brémond ◽  
C. Adamo
Keyword(s):  
Open Shell ◽  
Density Functionals ◽  
Orbital Optimization

THEORY OF ORBITAL SPLITTING IN METALS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 255-257 ◽  
Author(s):  
LUKAS SEVERIN ◽  
M. S. S. BROOKS ◽  
BÖRJE JOHANSSON
Keyword(s):  
Density Matrix ◽  
Ab Initio ◽  
Spin Density ◽  
Open Shell ◽  
Spin Density Matrix ◽  
Hartree Fock ◽  
Local Spin ◽  
Scaling Procedure ◽  
Good Agreement

A theory for orbital splitting is derived from a statistical Hartree-Fock (HF) treatment of open shell interactions. In a scaling procedure, where the HF spinpolarization matrix is replaced by the corresponding local spin density matrix, an expression for the orbital splitting is derived which is well suited for implementation in the standard ab initio calculational scheme. Results for Co metal as well as for the itinerant 5f ferromagnet US is presented, which are in good agreement with experiment.

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