Effect of -Conjugation and Interruption

FIGURE 7. The absorption and PL spectra of 16, 17, 53, and 71—74. The absorption spectra are the higher energy dotted lines measured at 290 K. PL spectra were taken at both 290 (dashed lines, in CH2C12) and 20 K solid lines, as thin films). For 74, the PL spectrum (dashed/dotted line) as thin film at 290 K is also included. 

FIGURE 8. Electronic energy level diagram of Pt polyynes with group 14 and 16 main group elements based on absorption and PL data. Dashed lines represent the levels for P3. The S0 levels are arbitrarily shown to be of equal energy, and all energy values are 

TABLE 1., Optical and Photophysical Data for Platinum(II) Metallopolyynes  

By changing from a trans- to a m-con figured Pt(II) unit (i.e., from 21 to 75), the conjugation chain in 75 is disturbed (Xmax=364 nm for 75 versus 391 nm for 21), resulting in a much stronger triplet emission at room temperature (Fig. 9).32,33 However, the solubility of 75 notably decreases relative to 21, resulting in a lower molecular weight for the soluble fraction of the polymer. 

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