Analysis of Bonding Properties of Osmabenzyne in the Ground State ( S 0 ) and Excited Singlet ( S 1 ) State: A Quantum-C
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TRUCTURE OF MATTER AND QUANTUM CHEMISTRY
Analysis of Bonding Properties of Osmabenzyne in the Ground State (S0) and Excited Singlet (S1) State: A Quantum-Chemical Calculation Vahid Daneshdoosta, Reza Ghiasib,*, and Azam Marjania aDepartment bDepartment
of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran of Chemistry, East Tehran Branch, Islamic Azad University, Tehran, Iran *e-mail: [email protected]
Received October 10, 2019; revised October 10, 2019; accepted December 17, 2019
Abstract—The hybrid density functional MPW1PW91 theory was applied in the ground state (S0) and first excited singlet (S1) state to highlight the structure, electronic properties, and aromaticity of an osmabenzyne complex. The first singlet excited state was determined by time-dependent DFT (TD-DFT) method. It was tried to explore the geometry, frontier orbital energies, reactivity indices, and aromaticity in the first singlet excited state of osmabenzyne complex and compare to ground state. Moreover, this study determined the involvement of the fragments of the studied complexes in the frontier orbitals regarding the ground state and first singlet excited state. Energy decomposition analysis (EDA) for S0 and S1 states was applied to study the nature of the chemical bond between the [Os (PH3)2Cl2]2+ and [C5H4]2– fragment. In addition, the Os–C, Os–Cl, and Os–P bonds in the studied osmabenzyne were clarified using quantum theory of atoms in molecules analysis (QTAIM) calculations. Keywords: osmabenzyne, excited state, energy decomposition analysis (EDA), quantum theory of atoms in molecules analysis (QTAIM) computations, para-delocalization index (PDI) DOI: 10.1134/S0036024420120080
INTRODUCTION Metallabenzynes [1–6] are organometallic compounds; they are closely associated to metallabenzenes and are derived by formally replacing a carbon atom or a C–H group in benzyne with an isolobal transition metal fragment. Initially, it has been argued that metallabenzynes are highly unstable and it is impossible isolate them since organic compounds with a C≡C bond in the six-membered ring, for instance, benzyne and cyclohexyne, are thermally too unstable due to ring strain. The first stable metallabenzyne [Os(≡CC(SiMe3)=C(CH3)C–(SiMe3)=CH)Cl2(PPh3)2] was obtained unexpectedly during effort to prepare osmium vinylidene complexes of the type [OsCl2(=C=CHR)(PR3' )2] [7]. However, in recent years, numerous stable osmabenzynes have been isolated [8–18] and their interesting chemical properties have been determined. For instance, osmabenzynes, such as metallabenzenes and aromatic compounds, can undergo electrophilic substitution reactions [9]. Also, the electronic explanation for the stabilization of osmabenzyne has been studied with the aid of orbital interaction analysis and density functional theory calculations [19]; the structure, molecular orbital analysis, reactivity, electronic spectra, hyperpolarizability, and natural bond orbital analysis in osmabenzyne, and substituted osmabenzyne has been investigated [20].
In the present w
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