Optical and Electronic Properties of Metal-containing Poly-ynes and their Organic Precursors
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Optical and Electronic Properties of Metal-containing Poly-ynes and their Organic Precursors Marek Jura, Olivia F. Koentjoro, Paul R. Raithby, Emma L. Sharp and Paul J. Wilson Department of Chemistry University of Bath Claverton Down Bath BA2 7AY U.K. ABSTRACT A series of platinum(II) di-yne complexes with the general formula [PhPt(PR3)2-C≡C-XC≡C-Pt(PR3)2Ph] where R = Et, nBu and X = a range of extended hetero-aromatic spacer groups, have been prepared by the coupling reaction between two molar equivalents of [PhPt(PR3)2Cl] and one molar equivalent of the terminal dialkyne, HC≡C-X-C≡CH, in the presence of CuI catalyst. The complexes have been characterised by IR, NMR and optical spectroscopy. These materials, which are precursors to related platinum(II) poly-yne polymers, have been specifically designed to be incorporated into metal-molecule-metal junctions in nanoelectronic devices. INTRODUCTION Over the last two decades the chemistry of conjugated organic polymers has grown into a major research area because of the use of these materials in electronic and photonic applications [1,2]. The synthetic flexibility and ease of processing of these materials as well as the possibility of being able to tailor their properties to achieve a desired function has made them prime candidates for a plethora of applications in materials science. There are reports of their use as laser dyes [3], scintillators [3], light emitting diodes (LEDs) [4], sensors [5], piezoelectric and pyroelectric materials [6] and photoconductors [7]. They are being investigated for use as optical data storage devices [8], and as optical switches and signal processing devices [9], as well as having their nonlinear optical properties utilised [10]. In these organic conjugated polymers, light emission occurs from the singlet excited state (S1) but emission in LEDs can occur from both the excited singlet (S1) and triplet (T1) states. If the technology in this area is to develop further it is essential that the photophysics of the triplet state is well understood. It will then be possible to alter the materials synthetically so that the relative energies of the singlet and triplet states can be manipulated and the emission from the excited triplet state harvested [11]. One successful method of achieving this is to introduce heavy transition metals, such as platinum, into the backbone of the conjugated organic polymers since the presence of the heavy metal produces sufficient spin-orbit coupling to allow intersystem crossing and hence to allow light emission from the triplet excited state to occur [12]. Thus, platinum(II) poly-ynes are good models for the study of the triplet state in organic polymers [13]. In addition, the unusual photophysics of these “rigid-rod” platinum-containing polymers themselves has led to the fabrication of materials that act as highly efficient electroluminescent devices [14] and they have found applications in laser protection equipment [15].
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