We assume that the stronger intermolecular interactions of p-ClTPA in crystals are beneficial to restrict molecular motions and thus stabilize the higher T2 state for the realization of dual-RTP emission. Besides, although the crystal structures are all centrosymmetric (Table ), the molecular dipole moment of o-ClTPA is calculated to be the largest among the three isomers (Figure ). Therefore, the synergy of large dipole moment, abundant intermolecular interactions, and tight packing motif should be responsible for the distinctive ML behavior of o-ClTPA in crystals. To reveal the mechanism of diversified emissive behaviors and establish the structureproperty relationship, the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations are performed on the three isomers in the gas and crystal phases, respectively. As shown in figure , in the gas phase, the three isomers have similar energy level diagrams, as well as the energy splitting (∆EST) and SOC constants (S1-Tn) between the lowest singlet state (S1) and involved triplet states (Tn). Especially, this relatively large S1-Tn and small ∆EST are conducive to generating triplet excitons via promoting ISC, thus activating the low-temperature phosphorescence of isolated molecules in dilute solutions. Meanwhile, these isomers display similar HOMO and LUMO distributions because of their similar optimized molecular configurations (Figure ). The natural orbital transitions (NOTs) analysis indicates that the three isomers display extremely similar transition configurations of S0→S1 and S0→T1, mainly composed of the HOMO→LUMO component (Figure ). These qualitative and quantitative calculations manifest those similar luminescent properties of these isomers in dilute solutions can be ascribed to their similar excited-state electronic structures and transition configurations.