DFT/TD-DFT analysis of structural, electrochemical and optical data from mononuclear osmium and heterobinuclear osmium-ruthenium alkynyl complexes

Erandi Kulasekera, Simon Petrie, Rob Stranger, Marie P. Cifuentes, Mark G. Humphrey*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    6 Citations (Scopus)

    Abstract

    Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations of the molecular structures, optical absorption spectra, and spectroelectrochemical behavior of the complexes trans-[Os(CCC6H 4-4-CCH)Cl(dppe)2] (1), trans,trans-[(dppe) 2ClOs(CCC6H4-4-CC)RuCl(dppe)2] (2), trans,trans-[(dppe)2ClOs(CCC6H4-4-CC) Ru(CCC6H4-4-CCH)(dppe)2] (3), trans-[Os(CCC6H4-4-CCC6H4-4-CCH) Cl(dppe)2] (4), and trans,trans-[(dppe)2ClOs(CCC 6H4-4-CCC6H4-4-CC)RuCl(dppe) 2] (5) were undertaken. The calculated structures for the mononuclear osmium complexes 1 and 4 are in good agreement with the X-ray data, a 0.3 Å lengthening of the Os-Cl bond in proceeding from the theoretical model for 4 to the experimental structure being rationalized on the basis of intermolecular H-bonding effects for the latter. For the non-oxidized forms of these five complexes, the lowest-energy bands are assigned to MLCT transitions along the main molecular axis from orbitals with mostly Os d, Cl p and alkynyl character to orbitals on the alkynyl backbone. The calculations indicate that the heterobimetallic complexes 2, 3 and 5 do not undergo metal-centred oxidation. Instead, the electron is lost from an orbital that is delocalized across the bridge and both metal centres. The mono-oxidized and di-oxidized species show new bands in the low-energy region arising from LMCT transitions, primarily corresponding to transitions from the dppe ligands to metal- and alkynyl-based orbitals. For structures involving two or more phenylethynyl units along the main axis of the molecule, the TD-DFT calculations are in significantly better agreement with the observed spectra when the phenyl groups adopt a non-coplanar conformation.

    Original languageEnglish
    Pages (from-to)21-28
    Number of pages8
    JournalJournal of Organometallic Chemistry
    Volume748
    DOIs
    Publication statusPublished - 2013

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