As far as the DMA-oC-PhEPy (4) structure, again the o-carborane cage system is at the apex of a V-shaped molecule (see Figure ). The amine portion essentially replaces the Br in (3), and the pyrene, phenyl and acetylenic groups are on the other leg. The molecules stack in an interleaved relationship, and there is no π-π stacking observed (see Figure ). However, there are some close contacts between the carborane ring system and the pyrene of an adjacent molecule (as depicted in Figure ). These values are all given in the SI in Table ), as well as the acetylenic distances for C9 and C10. The acetylenic distance found here is 1.199(2) Å (again, normal), and the C-C distance for the o-carbon atoms in the carborane = 1.748(2) Å, again possibly form the substituents on these two carbon atoms. The phenyl rings of the DMA-oC-PhEPy (4), however, exhibit an almost perpendicular orientation with respect to the pyrene planes: 87.71(4)° between the phenyl and the pyrene, and 87.05(4) o between the pyrene and the substituted phenyl ring. The absorption spectra of p-BrPh-oC-PhEPy and DMA-oC-PhEPy in THF solutions (1.0 x 10 -5 M) exhibit 367 and 400 nm bands assigned to π-π* transitions and a vibronic structure similar to that of pyrene, and are red-shifted when compared to 1-(phenylethynyl)pyrene, Figure . The 4 to 10 - M, with a new broad emission band at 450 nm, and the appearance of an additional band in the tentatively assigned to excimer formation, as the compounds aggregate. A similar trend is also observed for (4) with the emergence of a new broad emission band at approximately 525 nm. This band can be attributed to the excimer's emission band (Figure ). To investigate AIE properties, emission spectra were collected in diluted (1.0 x 10 -5 M) THF solutions with increasing amount of water, in which ( ) and ( ) are insoluble, as shown in Figure . Upon addition of water (10%), following aggregates formation, there was a decrease in the emission intensity and, in the spectrum of (3), the appearance of a small band centered at 500 nm (A), which is assigned as the emission band from the pyrene excimer. This is consistent with the spectra in hexane, in Figure , a solvent in which (3) has low solubility. At high water fraction (>70%), there was a noticeable disappearance of the monomer emission band and the appearance of an intense emission band around 643 nm (B) for (3) and 628 nm for (4). Our hypothesis is that this new emission predominantly arises from intramolecular charge transfer, and is consistent with AIE observed in other carborane derivatives, a result of the restricted rotations of the substituents in o-carborane in the solid state, which suppress nonradiative emission. The emission intensity of (4) was enhanced 3-fold as the water content increased, compared to the intensity in pure THF Considering the crystal structure of (3), which reveals close …π interactions between the carborane cage and pyrene rings, we considered whether differences in the emission properties of p-BrPh-oC-PhEPy in the solid state (amorphous, single crystalline or microcrystalline) are the result of a combination of both intra-and inter-molecular charge transfer. To demonstrate this assumption, we prepared PMMA films with increasing wt% of ( ) and ( ), and compared them with the spectra of ( ) and ( ) in the solid microcrystalline state (see Figure ). The pronounced 584 nm emission observed in p-BrPh-oC-PhEPy in PMMA (Figure ) is attributable to the restriction of intramolecular rotations in a solid matrix and it is red shifted by 10 nm at increasing wt% of (3), but not to aggregation. A similar trend is observed for (4) with a band at 576 (1%) to 592 nm (10%). In comparison, a significantly red-shifted emission at 650 nm was observed for neat solid (3) (Figure , red line) but not for (4) (604 bands, Figure , red line). PMMA film at 25 °C with increasing wt% of 3 and 4, respectively, compared to the emission of spectrum of ( ) and (4) as a neat solid (red line). exc = 367nm.