Ligand Perturbations on Fluorescence of Dinuclear Platinum Complexes of 5,12-Diethynyltetracene: A Spectroscopic and Computational Study

To understand how the Pt-II ion perturbs the electronic structures of tetracene, 10 dinuclear [X(Et3P)(2)Pt-II](2)-5,12-diethynyltetracene complexes with different auxiliary ligands were synthesized. Interactions between the Pt-II ion and 5,12-diethynyltetracene were probed spectroscopically and computationally. The dinuclear [X(Et3P)(2)Pt-II]2-5,12-diethynyltetracene complexes exhibit red-shifted absorption and fluorescence in comparison with those of 5,12-bis-(triisopropylsilylethynyl)tetracene, with the neutral complexes with g-donating auxiliary ligands showing a larger red shift than the cationic complexes with pi-accepting ligands. Electronic structures of the complexes and effects of the metal ions and the ligands on the electronic transitions of the complexes were investigated by TD-DFT calculations, the results of which showed that the electronic structure of the 5,12-diethynyltetracene core is perturbed by g interactions with the Pt fragments, the extent of which depends on the energies of the dg orbitals of the Pt fragments.