Here, we unveil fluorescence anisotropies of a series of phosphole oxide-based dyes with an elongated -conjugated system, on which the transition dipole moment lies, in nematic liquid crystals. We observe that, as the number, size, and rigidity of substituents protruding from the pi-conjugated plane increase, the transition dipole moment tends to tilt away from the nematic director over the magic angle, ~54.7°, showing conspicuous negative fluorescence anisotropy. Analysis of molecular shapes suggests that the substitutions modulate the interaction with the nematic mean field, impacting the direction of the principal molecular axis aligned with the nematic director.