Halogen Bonding Involving CO and CS with Carbon as the Electron Donor
AbstractMP2/aug’-cc-pVTZ calculations have been carried out to investigate the halogen-bonded complexes formed when CO and CS act as electron-pair donors through C to ClF, ClNC, ClCl, ClOH, ClCN, ClCCH, and ClNH2. CO forms only complexes stabilized by traditional halogen bonds, and all ClY molecules form traditional halogen-bonded complexes with SC, except ClF which forms only an ion-pair complex. Ion-pair complexes are also found on the SC:ClNC and SC:ClCl surfaces. SC:ClY complexes stabilized by traditional halogen bonds have greater binding energies than the corresponding OC:ClY complexes. The largest binding energies are found for the ion-pair SC–Cl+:−Y complexes. The transition structures which connect the complex and the ion pair on SC:ClNC and SC:ClCl potential surfaces provide the barriers for inter-converting these structures. Charge-transfer from the lone pair on C to the σ-hole on Cl is the primary charge-transfer interaction stabilizing OC:ClY and SC:ClY complexes with traditional halogen bonds. A secondary charge-transfer occurs from the lone pairs on Cl to the in-plane and out-of-plane π antibonding orbitals of ClY. This secondary interaction assumes increased importance in the SC:ClNH2 complex, and is a factor leading to its unusual structure. C–O and C–S stretching frequencies and 13C chemical shieldings increase upon complex formation with ClY molecules. These two spectroscopic properties clearly differentiate between SC:ClY complexes and SC–Cl+:−Y ion pairs. Spin–spin coupling constants 1xJ(C–Cl) for OC:ClY complexes increase with decreasing distance. As a function of the C–Cl distance, 1xJ(C–Cl) and 1J(C–Cl) provide a fingerprint of the evolution of the halogen bond from a traditional halogen bond in the complexes, to a chlorine-shared halogen bond in the transition structures, to a covalent bond in the ion pairs. View Full-Text
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Del Bene, J.E.; Alkorta, I.; Elguero, J. Halogen Bonding Involving CO and CS with Carbon as the Electron Donor. Molecules 2017, 22, 1955.
Del Bene JE, Alkorta I, Elguero J. Halogen Bonding Involving CO and CS with Carbon as the Electron Donor. Molecules. 2017; 22(11):1955.Chicago/Turabian Style
Del Bene, Janet E.; Alkorta, Ibon; Elguero, José. 2017. "Halogen Bonding Involving CO and CS with Carbon as the Electron Donor." Molecules 22, no. 11: 1955.
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