Photophysical properties of a series of electron-donating and -withdrawing platinum acetylide two-photon chromophores.

To explore spectroscopic structure−property relationships in platinum acetylides, we synthesized a series of complexes having the molecular formula trans-bis(tributylphosphine)-bis(4-((9,9-diethyl-7-ethynyl-9H-fluoren-2-yl)ethynyl)-R)-platinum. The substituent, R = NH2, OCH3, N(phenyl)2, t-butyl, CH3, H, F, benzothiazole, CF3, CN, and NO2, was chosen for a systematic variation in electron-donating and -withdrawing properties as described by the Hammett parameter σp. UV/vis, fluorescence, and phosphorescence spectra, transient absorption spectra on the fs−ps time scale, and longer time scale flash photolysis on the ns time scale were collected. DFT and TDDFT calculations of the T1 and S1 energies were performed. The ES and ET values measured from linear spectra correlate well with the calculated results, giving evidence for the delocalized MLCT character of the S1 state and confinement of the T1 exciton on one ligand. The calculated T1 state dipole moment ranges from 0.5 to 14 D, showing the polar, charge-...