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Cyclometalated heteronuclear Pt/Ag and Pt/Tl complexes: A structural and photophysical study

Jamali, S ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1039/c3dt52209a
  3. Abstract:
  4. To investigate the factors influencing the luminescent properties of polymetallic cycloplatinated complexes a detailed study of the photophysical and structural properties of the heteronuclear complexes [Pt2Me 2(bhq)2(μ-dppy)2Ag2(μ-acetone) ](BF4)2, 2, [PtMe(bhq)(dppy)Tl]PF6, 3, and [Pt2Me2(bhq)2(dppy)2Tl]PF 6, 4, [bhq = benzo[h]quinoline, dppy = 2-(diphenylphosphino)pyridine] was conducted. Complexes 3 and 4 synthesized by the reaction of [PtMe(bhq)(dppy)], 1, with TlPF6 (1 or 1/2 equiv.) and stabilized by unsupported Pt-Tl bonds as revealed by multinuclear NMR spectroscopy and confirmed by X-ray crystallography for 3. DFT calculations for the previously reported butterfly Pt2Ag2 cluster 2 reveal that in the optimized geometry the bridging acetone molecule is removed and the metal core displays a planar-shaped geometry in which according to a QTAIM calculation and natural bond orbital (NBO) analysis the Ag⋯Ag metallophilic interaction is strengthened. In contrast to the precursor 1, which is only emissive in glassy solutions (3MLCT 485 nm), all 2-4 heteropolynuclear complexes display intense emissions in the solid state and in glassy solutions. Time-dependent density functional theory (TD-DFT) is used to elucidate the origin of the electronic transitions in the heteronuclear complexes 2 and 3. The low energy absorption and intense orange emission for cluster 2 (solid 77 K and glass) are attributed to metal-metal to ligand charge transfer (MM′LCT) with a minor L′LCT contribution. For 3 and 4 two different bands are developed: the high energy band (602-630 nm) observed for 4 at 77 K (solid, glass) and in diluted glasses for 3 is ascribed to emission from discrete Pt2Tl units of mixed 3L′LCT/3LM′CT origin. However, the low energy band (670-690 nm) observed at room temperature (solid) for both complexes and also in concentrated glasses for 3 is assigned to 3ππ excited states arising from intermolecular interactions
  5. Keywords:
  6. Heteronuclear complexes ; Heteropolynuclear complexes ; Intermolecular interactions ; Metallophilic interactions ; Multinuclear NMR spectroscopy ; Natural bond orbital analysis ; Photophysical studies ; Time dependent density functional theory ; Acetone ; Band structure ; Chemical bonds ; Density functional theory ; Glass ; Nuclear magnetic resonance spectroscopy ; Platinum ; X ray crystallography ; Synthesis (chemical)
  7. Source: Dalton Transactions ; Vol. 43, issue. 3 , 2014 , pp. 1105-1116 ; ISSN: 14779226
  8. URL: http://pubs.rsc.org/en/Content/ArticleLanding/2014/DT/C3DT52209A