The synthesis, structural characterization, photoluminescence properties, and density functional theory analysis of three Pt(II) diimine complexes, Pt(dbbpy)(CdropCR)(2) [dbbpy = 4,4'-di(tert-butyl-2,2'-bipyridine; R = -SiMe3, -CdropC-SiMe3, or -t-Bu], are presented. The Pt(dbbpy)(CdropC-tBu)(2) complex serves as a carbon-based ligand structure for which the photophysical properties of the two silicon-bearing complexes are compared in dichloromethane. Pt(dbbpy)(CdropC-SiMe3)(2) and Pt(dbbpy)(CdropC-CdropC-SiMe3)(2) display visible absorptions with strong green emission (lambda(emmax) = 526 and 524 nm, respectively) while Pt(dbbpy)(CdropCt-Bu)(2) displays efficient, long-lived yellow emission (lambda(emmax) = 557 nm). Direct side by side comparisons of Pt(dbbpy)(CdropC-SiMe3)(2) and Pt(dbbpy)(CdropC-t-Bu)(2) suggest that the difference in excited state energy results from the relative sigma-donor strength of the acetylide ligands.