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Issue 12, 2011
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Pt–Ag clusters and their neutral mononuclear Pt(II) starting complexes: structural and luminescence studies

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The mononuclear complexes [Pt(bzq)(S⁁S)] [S⁁S = pyrrolidinedithiocarbamate (pdtc 1), dimethyldithiocarbamate (dmdtc 2)] were prepared by reaction of [Pt(bzq)(NCMe)2]ClO4 with an equimolecular amount of [NH4(pdtc)] and [Na(dmdtc)·2H2O] respectively in MeOH. Reactions of 1 and 2 with AgClO4 in 1 : 1 and 2 : 1 molar ratios rendered the heteropolinuclear compounds [{Pt(bzq)(S⁁S)Ag}2](ClO4)2 (S⁁S = pdtc 3, dmdtc 4) and [{Pt(bzq)(S⁁S)}2Ag](ClO4) (S⁁S = pdtc 5, dmdtc 6) respectively. The X-ray studies on single crystals of 3 and 4 showed that both consist of tetranuclear [Pt2Ag2] clusters with the Pt–Ag and the Ag–Ag distances in the range of those corresponding to Pt–Ag dative bonds and argentophilic interactions. In 3 the tetranuclear [Pt2Ag2] clusters are connected into infinite polymeric chains by Pt⋯Pt metallophilic interactions (Pt⋯Pt = 3.1890(7) Å). The X-ray study on a single crystal of 5 showed that it is a polymer based on trinuclear [Pt2Ag] clusters containing two unsupported Pt–Ag dative bonds and connected by Ag–S bonds in such a way that the “Pt–Ag–S–Pt–Ag–S” atoms draw a zigzag polymeric chain. TD-DFT calculations carried out for 1 indicate that the lowest energy absorption band in CH2Cl2 can be described as a mixture of 1MLCT, 1IL and 1L′LCT transitions. Powdered samples of 1 at 298 K and 77 K show a green-yellow emission band coming mainly from a 3LC excited state. However complex 2 shows “luminescence thermochromism”: the colour of its luminescence changes from green-yellow at 77 K to orange-red at 298 K. The emission of the Pt–Ag clusters, 3–6, in the solid state, are due to excimeric 3ππ and/or 3MMLCT (dσ* → π*) low-lying excited states, indicating that the presence of silver in the clusters makes the “Pt(bzq)(S⁁S)” fragments interact to a large extent through Pt⋯Pt and/or π–π interactions. Solid 3 is a highly selective vapochromic compound towards acetonitrile although this behaviour is not fully reversible.

Graphical abstract: Pt–Ag clusters and their neutral mononuclear Pt(ii) starting complexes: structural and luminescence studies

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The article was received on 22 Oct 2010, accepted on 21 Dec 2010 and first published on 11 Feb 2011

Article type: Paper
DOI: 10.1039/C0DT01451F
Citation: Dalton Trans., 2011,40, 2898-2912
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    Pt–Ag clusters and their neutral mononuclear Pt(II) starting complexes: structural and luminescence studies

    J. Forniés, V. Sicilia, J. M. Casas, A. Martín, J. A. López, C. Larraz, P. Borja and C. Ovejero, Dalton Trans., 2011, 40, 2898
    DOI: 10.1039/C0DT01451F

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