designed a soft organic molecule with multiple emissions of TADF, RTP, and ML by selectively expressing chromophores. Despite these excellent works, multifunctional organic emitters are still very scarce partly due to the lack of reliable guidance. Meanwhile, the abovementioned multifunctional organic emitters are found serendipitously because it is tricky to obtain various kinds of crystals from one single molecule. Herein, we focus on studying the solid-state luminescence of basic dyes to develop multifunctional organic materials with simple structure and easy accessibility. Triphenylamine (TPA) is a promising candidate in this context because it exhibits a simple propeller-shaped structure and is susceptible to further modifications. Furthermore, positional isomerism, a fundamental concept in organic chemistry, can remarkably influence the physicochemical properties of organic molecules. Indeed, a minor change in the substitution position has been demonstrated to drastically influence the optoelectronic properties of organic semiconductors. Nevertheless, the role of positional isomerism in controlling the excited-state properties is less developed. With these in mind, we have designed three simple positional isomers with the Cl group located in the ortho-, meta-, and para-positions on the TPA core, respectively (Figure ). These isomers can be easily prepared via the same one-step reaction from commercially available raw materials. Meanwhile, the ester and Cl groups can not only promote the spin-orbit coupling (SOC) between the singlet and triplet states but also facilitate the intramolecular charge transfer (CT) to regulate tripletexciton behaviors. Experimental results show that although the three isomers have similar photophysical properties in dilute solutions, diversified emissive behaviors of typical AIE, TADF, ML, RTP and unique dual-RTP are successfully realized in crystals (Table ). In particular, the ortho-isomer achieves simultaneous AIE, TADF, and ML properties while typical AIE and unique dual-RTP coexist in the para-isomer. The crystal structure analysis reveals that a slight difference in the substitution position can significantly alter intermolecular interactions and molecular packings, which in turn drastically impacts excited-state electronic structures and thus emissive properties in crystals. Theoretical studies not only reveal the emission mechanisms of TADF, RTP, and dual-RTP of these isomers but also unveil the crucial contributions of intermolecular interactions and molecular packings rather than intrinsic excited-state electronic structures to the diversified emissive behaviors in the crystal state. This work elaborates the underlying reasons for the significantly different effect of positional isomerism on the luminescent properties in solution and crystal states of simple isomers, which could aid in designing multifunctional organic materials. Firstly, the photophysical properties of these isomers are studied in dilute THF solutions. As illustrated in Figure , the three isomers display similar absorption spectra with two sets of absorption bands in the range of 250 ~ 450 nm, which can be attributed to the locally-excited (LE) and intramolecular charge transfer (ICT) transitions, respectively. Owing to the reduced steric hindrance resulting from the subtle variation in the substitution position of the Cl atom, the ICT absorption band is gradually redshifted from o-MCBA to m-MCBA and then to p-MCBA. Likewise, the three isomers also show similar fluorescence spectra with a broad and featureless emission band originating from the radiative transition of the CT excited state (Figure ). Additionally, when the polarity of the THF/water mixture is gradually increased by progressively increasing the water fraction, the fluorescent emission of these isomers is gradually redshifted with reduced intensity (Figure ). Until a high water fraction (99%), the fluorescence emission is blueshifted with enhanced intensity due to the formation of aggregates.