Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-3179
Reiher, M; Kirchner, B; Hutter, J; Sellmann, D; Hess, B A (2004). A photochemical activation scheme of inert dinitrogen by dinuclear Ru(II) and Fe(II) complexes. Chemistry - A European Journal, 10(18):4443-4453.
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A general photochemical activation process of inert dinitrogen coordinated to two metal centers is presented on the basis of high-level DFT and ab initio calculations. The central feature of this activation process is the occupation of an antibonding pi orbital upon electronic excitation from the singlet ground state S-0 to the first excited singlet state S-1. Populating the antibonding LUMO weakens the triple bond of dinitrogen. After a vertical excitation, the excited complex may structurally relax in the S-1 state and approaches its minimum structure in the S-1 state. This excited-state minimum structure features the dinitrogen bound in a diazenoid form, which exhibits a double bond and two lone pairs localized at the two nitrogen atoms, ready to be protonated. Reduction and de-excitation then yield the corresponding diazene complex; its generation represents the essential step in a nitrogen fixation and reduction protocol. The consecutive process of excitation, protonation, and reduction may be rearranged in any experimentally appropriate order. The protons needed for the reaction from dinitrogen to diazene can be provided by the ligand sphere of the complexes, which contains sulfur atoms acting as proton acceptors. These protonated thiolate functionalities bring protons close to the dinitrogen moiety. Because protonation does not change the pi-antibonding character of the LUMO, the universal and well-directed character of the photochemical activation process makes it possible to protonate the dinitrogen complex before it is irradiated. The pi-antibonding LUMO plays the central role in the activation process, since the diazenoid structure was obtained by excitation from various occupied orbitals as well as by a direct two-electron reduction (without photochemical activation) of the complex; that is, the important bending of N-2 towards a diazenoid conformation can be achieved by populating the pi-antibonding LUMO.
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|Item Type:||Journal Article, refereed, original work|
|Communities & Collections:||07 Faculty of Science > Department of Chemistry|
|Deposited On:||27 Mar 2009 09:52|
|Last Modified:||05 Jun 2014 13:51|
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