The synthesis, electronic spectra, photochemical properties, and DFT calculations of four phenylpyridine (ppy)-derived C boolean AND N ligands and their cyclo-metalated [((CN)-N-boolean AND)Pt(II)(acac)] ((CN)-N-boolean AND = trans-n-(4-NR2-styryl)-2-phenylpyridine, where n = 3' or 4 and R = Me or Ph, and acac = acetylacetonate) complexes are reported. The results allow one to address the effects of the styryl position (n = 3' or 4) and the amino N-substituents (N-Me or N-Ph) on the photoluminescence and trans -> cis photoisomerization quantum efficiencies (Phi(f) and Phi(tc)) of the free ligands and the Pt complexes. In general, the styryl position effect is more significant than the amino substituent effect. The relative Phi(f) and Phi(tc) values are distinct between the free ligands and the corresponding Pt complexes. However, the phenomenon of Phi(f) + Phi(tc), approximate to 1.0 is observed for all cases in solutions at room temperature. This phenomenon is interpreted by the conventional one-bond-twist mechanism for photoisomerization, S-1 but barrierless in T-1. We conclude that ca. 50% of the C = C bond torsion in the excited-state manifold leads to the cis isomer and the excited-state deactivations are dominated by fluorescence and trans -> cis isomerization for both the ligands and the complexes.