Issue 15, 2013

Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions

Abstract

Heterodinuclear complexes, syn-[MPt(μ-pyt)2(bpy)2]n+ (syn-[MPt], M = Pd2+, Au3+, Hpyt = pyridine-2-thiol, bpy = 2,2′-bipyridine), were synthesized as a selective geometrical isomer by stepwise complexation. X-ray analyses of the hexafluorophosphate salts of these complexes proved their dinuclear structures with short M⋯Pt distances (2.9084(4) Å for syn-[PdPt] and 2.9071(4) Å for syn-[AuPt]), similar to the homodinuclear complex (2.9292(2) Å for syn-[PtPt]). In the syn-[PdPt] crystal, two dinuclear motifs are arranged closely in a head-to-head manner with a short Pt⋯Pt distance (3.3757(3) Å), forming a dimer-of-dimer structure as in the case of syn-[PtPt], whereas the corresponding crystal of syn-[AuPt] has a discrete arrangement of the dinuclear motifs. By the isomerisation of syn-[PdPt], anti-[PdPt] with equivalent environments of the Pd2+ and Pt2+ ions was also obtained successfully. Syn-[PdPt](PF6)2 exhibits vapochromic behaviour based on the absorption/desorption of CH3CN vapour, similar to that observed for syn-[PtPt](PF6)2. The reversible structural transformations induced by the uptake and release of CH3CN molecules were investigated by powder and single-crystal X-ray diffraction studies. These revealed that the vapochromic behaviour was based on the interconversion between two phases, the dimer-of-dimer structure with a short Pt⋯Pt distance and a π–π stacked arrangement with no Pt⋯Pt intermolecular interaction. The introduction of the heterometal ions enabled control of the colour region: orange ↔ red for syn-[PdPt] vs. light red ↔ dark red for syn-[PtPt], reflecting the weaker metal–metal interaction between Pd2+ and Pt2+ ions in the dinuclear motif. In addition, these complexes were found to exhibit mechanochromic behaviour based on a crystal-to-amorphous transformation upon grinding, and the reconstruction of the crystal structures by vapour sorption.

Graphical abstract: Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions

Supplementary files

Article information

Article type
Paper
Submitted
28 Dec 2012
Accepted
31 Jan 2013
First published
21 Feb 2013

Dalton Trans., 2013,42, 5514-5523

Vapour and mechanically induced chromic behaviour of platinum complexes with a dimer-of-dimer motif and the effects of heterometal ions

T. Ohba, A. Kobayashi, H. Chang and M. Kato, Dalton Trans., 2013, 42, 5514 DOI: 10.1039/C3DT33100H

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