Synthesis and Characterization of Novel Platinum Acetylide Oligomers
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Synthesis and Characterization of Novel Platinum Acetylide Oligomers Thomas M. Cooper†, Benjamin C. Hall‡, Daniel G. McLean*, Joy E. Rogers**, Aaron R. Burke***, Kenneth Turnbull# and Andrew Weisner# †
Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH, 45433; ‡Systran, Inc, Dayton, OH, 45431; *Science Applications International Corporation, Dayton, OH, 45433; **UES, Inc. Dayton, OH, 45432; ***Anteon Corporation, Dayton, OH, 45431; #Dept. of Chemistry, Wright State University, Dayton, OH, 45435 ABSTRACT As part of an effort to develop a spectroscopic structure-property relationship in platinum acetylide oligomers, we have prepared a series of bidentate Pt(PBu3)2L2 compounds. The ligand was the series o-syd-C6H4-C≡C-(C6H4-C≡C)n-H, n = 0,1,2. The terminal oligomer unit consisted of a sydnone group ortho to the acetylene carbon. The compounds were characterized by various methods, including 13C-NMR, ground state absorption, fluorescence, phosphorescence and laser flash photolysis. The acetylenic 13C-NMR resonances showed sydnone influences that decreased with increasing number of monomer units. The ground state absorption spectra were slightly red shifted from those of the baseline oligomers not having a sydnone group. The low temperature emission and excitation spectra showed complex dependence on excitation and emission wavelengths, suggesting the chromphores resided in a distribution of solvent environments and conformations. Finally, broad triplet state absorption spectra were observed, with absorption throughout the visible and near infrared regions. INTRODUCTION The photophysics and photochemistry of transition metal acetylide complexes have recently received considerable attention. This class of compounds is an emerging nanomaterial with applications in electroluminescence and photonics. In our group we have been investigating the relation between chemical structure and spectroscopic properties[1,2]. To extend our understanding of this relation, we prepared a series of sydnone-containing platinum acetylide complexes. Spectroscopic studies of the photophysics of sydnones are rare, with only one flash photolysis study reported[3] as well as one recent investigation of photochromism[4]. Their nonlinear optical properties have also been investigated[5]. PBu3 Pt PBu3 N N O
N O
O
N O
PE1-syd PBu3 Pt PBu3 N N O
N O
O
N O
PE2-syd PBu3 Pt PBu3 N N O
N O
PE3-syd
O
N O
Figure 1. Chemical formulas of sydnone complexes
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EXPERIMENTAL The ligands were synthesized according to the scheme in Figure 2. The higher oligomers were prepared by attachment of 1-bromo-4-iodobenzene to the terminal acetylene by Sonogashira coupling followed by another coupling with trimethylsilylacetylene and removal of the trimeth
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