**4. Materials and Methods**

Unless otherwise noted, all reagents, solvents and precursors (tetraphenylmethane and 1-bromoadamantane) were purchased from commercial sources and used as received, without further purification. Nuclear magnetic resonance (NMR) spectra were recorded at room temperature on a Varian Unity Plus (400 MHz) spectrometer (Agilent Technologies, Inc., Santa Clara, CA, USA). Chemical shifts for 1H-NMR spectra were referenced to the residual protio impurity peaks in the deuterated solvents, while 13C{1H} NMR spectra were referenced against the solvent 13C resonances. A Nicolet 380 FT-IR system (Thermo Fisher Scientific Inc., Waltham, MA, USA) was used for the infrared (IR) spectroscopic analysis. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed on TA Q20 and TA Q50 (TA Instruments, New Castle, DE, USA), respectively. In order to calculate the molecular surface electrostatic potentials of tetra-halogenated TPM and TPA species, their geometries were optimized (using Spartan '14 software [55]) at hybrid functional B3LYP/6-311+G\*\* and B3LYP/6-311++G\*\* levels of theory, respectively, and potential values were subsequently mapped onto 0.002 au isosurface. Detailed crystallographic information about data collections, solutions, and refinements can be found in the Supplementary Materials. Structural visualizations and void mapping were done using Mercury software [56]. For free volume calculations, the voids function in Mercury (with contact surface, 1.2 Å probe radius and 0.2 Å approximate grid spacing) and/or the solvent-masking tool in Olex2 (with its default parameters) were employed [56,57].

### *4.1. Synthesis of Tetrakis(4-bromophenyl)methane (Br4TPM)*

The bromination of tetraphenylmethane was performed neat using an excess of molecular bromine. To a 100-mL round-bottom flask containing tetraphenylmethane (2.00 g, 6.24 mmol, 1 equiv.), bromine liquid (6.4 mL, 124.8 mmol, 20 equiv.) was added carefully at 0 ◦C. After attaching a water-cooled reflux condenser, the resultant dark reddish slurry was stirred vigorously at room temperature for one hour, and then cooled to −78 ◦C by using a dry ice/acetone bath. Ethanol (25 mL) was added slowly and the reaction mixture was allowed to warm to room temperature overnight. Then, to destroy excess/unreacted bromine, it was treated with 40% aqueous solution of sodium bisulfite (approximately 75 mL) and stirred for an additional 30 min until the orange color disappeared. The tan colored solid was collected by filtration, washed well with distilled water (100 mL) and oven-dried at 60 ◦C for five hours. This solid was further purified by re-crystallization from chloroform/ethanol (2:1), affording tetrakis(4-bromophenyl)methane, **Br4TPM,** as an off-white crystalline material. Yield: 3.65 g (5.74 mmol, 92%). 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.39 (d, 8H); 7.01 (d, 8H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 144.64, 132.57, 131.30, 121.02, 63.84. ATR-FTIR (cm−1): 3059, 1919, 1569, 1478, 1395, 1185, 1077, 1007, 948, 808, 753.

### *4.2. Synthesis of Tetrakis(4-((trimethylsilyl)ethynyl)phenyl)methane (TMS4TEPM)*

This step involved a Sonogashira cross-coupling reaction of tetrakis(4-bromophenyl)methane with trimethylsilylacetylene. Tetrakis(4-bromophenyl)methane (3.50 g, 5.50 mmol, 1 equiv.) and triphenylphosphine (462 mg, 1.76 mmol, 32 mol%) were placed in a 250-mL round-bottomed flask. Diisopropyl amine (100 mL) was added and the resulting solution was purged with dinitrogen gas for 30 min. Then, bis(triphenylphosphine)palladium(II) dichloride (618 mg, 0.88 mmol, 16 mol%), copper(I) iodide (168 mg, 0.88 mmol, 16 mol%) and trimethylsilylacetylene (6.2 mL, 44.0 mmol, 8 equiv.) were added. The reaction flask was fitted to a water-jacketed condenser, cooled to −78 ◦C, subjected to a brief vacuum/backfill cycle and refluxed for 24 h under nitrogen atmosphere. After removing volatile materials in vacuo, the residue was re-dissolved in chloroform (100 mL) and filtered through a pad of Celite, using an extra 50 mL portion of chloroform to wash the filter pad. The combined filtrate was then washed with distilled water (2 × 25 mL) and brine (25 mL), dried over anhydrous magnesium sulfate, and evaporated to dryness under vacuum. The crude product was flash-column-chromatographed on silica gel using pure hexanes followed by hexanes/ethyl acetate (4:1) as eluents to obtain the title compound, **TMS4TEPM,** as a pale yellowish solid. Yield: 3.30 g (4.68 mmol, 85%). 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.33 (d, 8H), 7.05 (d, 8H), 0.24 (s, 36H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 146.21, 131.59, 130.95, 121.42, 104.82, 95.00, 64.98, 0.18. ATR-FTIR (cm−1): 2957, 2157, 1496, 1405, 1247, 1187, 1019, 835, 758.

### *4.3. Synthesis of Tetrakis(4-(iodoethynyl)phenyl)methane (I4TEPM)*

The one-pot/in situ desilylative iodination (i.e., direct trimethylsilyl-to-iodo conversion) method was employed. Acetonitrile (150 mL) was transferred into a 250-mL round-bottom flask that contained tetrakis(4-((trimethylsilyl)ethynyl)phenyl)methane (2.50 g, 3.54 mmol, 1 equiv.). The flask was wrapped in aluminium foil, and then silver(I) fluoride (2.70 g, 21.3 mmol, 6 equiv.) and *N*-iodosuccinimide (4.78 g, 21.3 mmol, 6 equiv.) were added. It was then evacuated (while stirring), refilled with nitrogen and stirred at room temperature for 24 h. Distilled water (200 mL) was added and the resulting mixture was extracted with diethyl ether (4 × 50 mL). The combined organic layers were washed with saturated sodium bisulfite (40 mL), distilled water (40 mL) and brine (40 mL), and dried over anhydrous magnesium sulfate. The evaporation of the solvent under reduced pressure resulted in an orange colored residue. Additional cleanup by column chromatography (silica gel, hexanes/ethyl acetate = 9:1) gave the desired compound, **I4TEPM**, as a yellow solid. Crystals suitable for single-crystal X-ray diffraction were grown from hexanes. Yield: 1.83 g (1.98 mmol, 56%). 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.32 (d, 8H), 7.06 (d, 8H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 146.34, 132.04, 130.87, 121.81, 93.87, 65.02, 7.03. 1H-NMR (400 MHz, DMSO-*d*6) δ (ppm): 7.37 (d, 8H), 7.04 (d, 8H). 13C-NMR (100 MHz, DMSO-*d*6) δ (ppm): 145.68, 131.66, 130.36, 121.08, 92.11, 64.26, 18.41. ATR-FTIR (cm−1): 2944, 2167, 1490, 1400, 1186, 1112, 1016, 955, 898, 827, 722.

### *4.4. Synthesis of 1,3,5,7-Tetraphenyladamantane (TPA)*

In a 250-mL round-bottom flask, *tert*-butyl bromide (3.9 mL, 34.9 mmol, 2.5 equiv.) was added to a solution of 1-bromoadamantane (3.00 g, 13.9 mmol, 1 equiv.) in anhydrous benzene (30 mL). The flask was placed in an ice bath and aluminium chloride (186 mg, 1.39 mmol, 10 mol%) was carefully charged to the chilled stirring solution. The mixture was then heated under reflux until the evolution of hydrogen bromide ceased (the top of the condenser was connected to a gas absorption trap containing 30% aqueous sodium hydroxide). The resultant heterogeneous mixture was allowed to cool to room temperature and filtered, and the residue was washed sequentially with chloroform (30 mL), water (50 mL) and chloroform (30 mL). The off-white solid was further purified by washing overnight with refluxing chloroform in a Soxhlet apparatus, which gave 1,3,5,7-tetraphenyladamantane, **TPA**, as a fine white powder. Yield: 5.04 g (11.4 mmol, 82%). Mp: > 300 ◦C. ATR-FTIR (cm−1): 3055, 3020, 2918, 2849, 1597, 1493, 1442, 1355, 1263, 1078, 1030, 918, 889, 844, 788, 760, 746, 699.

### *4.5. Synthesis of 1,3,5,7-Tetrakis(4-iodophenyl)adamantane (I4TPA)*

To a 250-mL round-bottom flask containing a suspension of 1,3,5,7-tetraphenyladamantane (4.00 g, 9.08 mmol, 1 equiv.) in chloroform (100 mL) was added iodine (5.76 g, 22.7 mmol, 2.5 equiv.). This mixture was stirred vigorously at room temperature until the iodine fully dissolved. The flask was flushed with nitrogen gas and bis(trifluoroacetoxy)iodo)benzene (9.76 g, 22.7 mmol, 2.5 equiv.) was added. The resulting mixture was stirred at room temperature for 12 h. It was then filtered <sup>o</sup>ff, and the collected solid was washed with an excess amount of chloroform (200 mL). The combined dark purple filtrate was washed with 5% sodium bisulfite solution twice (2 × 50 mL), followed by distilled water (100 mL) and saturated sodium chloride solution (100 mL). It was dried with anhydrous magnesium sulfate and the solvent was removed under reduced pressure, which resulted in a pale-yellow solid. After refluxing in methanol (200 mL) for 12 h, the pure compound, **I4TPA**, was isolated as a white solid by filtration and air-drying. Yield: 5.91 g (6.26 mmol, 69%). 1H-NMR (400 MHz, CDCl3) δ (ppm): 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.67 (d, 8H), 7.18 (d, 8H), 2.06 (s, 12H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 148.63, 137.75, 127.34, 91.96, 46.92, 39.29. ATR-FTIR (cm−1): 3046, 2928, 2898, 2851, 1900, 1782, 1647, 1579, 1483, 1441, 1390, 1355, 1180, 1120, 1064, 1001, 888, 819, 775, 701, 659.

### *4.6. Synthesis of 1,3,5,7-Tetrakis(4-((trimethylsilyl)ethynyl)phenyl)adamantane (TMS4TEPA)*

As in the synthesis of **TMS4TEPM**, this step involved a four-fold Sonogashira cross-coupling reaction of 1,3,5,7-tetrakis(4-iodophenyl)adamantane (**I4TPA**) with trimethylsilylacetylene. Yield: 88%. 1H-NMR (400 MHz, CDCl3) δ (ppm): 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.45 (d, 8H), 7.38 (d, 8H), 2.09 (s, 12H), 0.24 (s, 36H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 149.63, 132.29, 125.13, 121.32, 105.19, 94.20, 46.97, 39.53, 0.25. ATR-FTIR (cm−1): 3033, 2958, 2897, 2852, 2155, 1604, 1502, 1445, 1398, 1355, 1248, 1115, 1016, 859, 835, 758.

### *4.7. Synthesis of 1,3,5,7-Tetrakis(4-(iodoethynyl)phenyl)adamantane (I4TEPA)*

The same one-pot desilylative iodination method described above for the synthesis of **I4TEPM** (i.e., the direct trimethylsilyl-to-iodo transformation using silver(I) fluoride and *N*-iodosuccinimide) was employed. Yield: 63%. 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.42 (d, 8H), 7.39 (d, 8H), 2.09 (s, 12H). 13C-NMR (100 MHz, CDCl3) δ (ppm): 149.82, 132.64, 125.16, 121.57, 94.16, 46.88, 39.50, 6.18. 1H-NMR (400 MHz, DMSO-*d*6) δ (ppm): 7.51 (d, 8H), 7.37 (d, 8H), 2.00 (s, 12H). 13C-NMR (100 MHz, DMSO-*d*6) δ (ppm): 150.14, 131.74, 125.48, 120.50, 92.59, 45.48, 38.95, 17.02. ATR-FTIR (cm−1): 3033, 2919, 2896, 2849, 2165, 1908, 1701, 1603, 1501, 1439, 1355, 1241, 1176, 1115, 1016, 837, 822, 769, 693.
