In order to examine the role of pi topology in spin alignment of organic molecules, a novel high-spin hydrocarbon, 3,4’-bis(phenylmethylene)biphenyl, has been designed, synthesized, and characterized by powder-pattern and single-crystal ESR spectroscopies. The spin multiplicity of its electronic ground state is a quintet (S = 2) in contrast to its x-topological isomer, 3,3’-bis(phenylmethylene)biphenyl (ground-state singlet). The g and fine-structure tensors have been determined accurately : g = 2.003 (isotropic), D = 0.1250 cm(-1), and E = -0.0065 cm(-1). The striking contrast in spin multiplicity clearly shows that spin alignment in organic molecules is highly dependent on the topology in their pi electron networks. This electronic structure has been clarified by an unrestricted Hartree-Fock calculation using a generalized Hubbard model, demonstrating that this approach is useful for large quantum systems such as organic high-spin hydrocarbons. The mechanism of the intramolecular spin alignment in this molecule has been discussed with the help of the theoretical calculation. The most probable molecular conformation of this high-spin molecule in benzophenone host crystals has been derived from the observed fine-structure tenser as compared with those calculated semiempirically.