Four platinum(II)
complexes Pt-1, Pt-2, Pt-3,
and Pt-4 with the isomeric donor–acceptor (D–A)
conjugated ligand framework are designed and prepared, and their thermal,
photophysical, and electrochemical characteristics investigated. Crystal
structures for Pt-1 and Pt-4 are determined
with single-crystal X-ray diffraction analysis, showing distorted
and nonplanar geometry. Complex Pt-4 exhibits much greater
distortion, attributed to the steric interactions between benzothiadiazole
and naphthalene. Remarkably different photophysical, electrochemical,
and electroluminescent properties are found for these platinum(II)
complexes. Photoluminescence wavelengths of these complexes range
from 590 to 800 nm with bandgaps of 1.7–2.0 eV. Coordination
with [1,2,5]thiadiazolo[3,4-c]pyridine and triphenylamine
can enhance D–A interactions, reducing the bandgap and producing
near-infrared emission for Pt-3. Organic light-emitting
devices (OLEDs) display electroluminescence with emission peaks at
626, 645, 826, and 571 nm, with maximum external quantum efficiencies
of 0.13%, 0.04%, 0.49%, and 0.22% for Pt-1, Pt-2, Pt-3, and Pt-4 doped OLEDs, respectively.
Thus, adjusting the coordination position with the isomeric conjugation
framework ligand is an appropriate strategy to tune the light-emitting
properties of platinum complexes in OLEDs.