Extremely strong tubular stacking of aromatic oligoamide macrocycles† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc02380c Click here for additional data file.

Aromatic oligoamide macrocycles 3 undergo extremely strong stacking in both solution and the solid state, forming tubular assemblies that further aggregate.


General Experimental Methods
Compounds 3a-3d were synthesized as reported before. 1 Chemical grade reagents were used without further purification. The 1X lysis buffer mentioned in the legend of Figure 6a was provided by Gene and Cell Technologies, Inc., CA. 1  increments from 3 to 94% of the maximum gradient strength in a linear ramp, diffusion gradient length is set to 2 ms, diffusion delay is 100 ms.

Dynamic Light Scattering (DLS)
DLS measurements were performed on a Brookhaven 90plus Particle Analyzer. The wavelength of laser is 532 nm. Fluorescence spectra were recorded on a Perkin Elmer LS55 luminescence spectrometer.
The hydrodynamic diameters of the assembly of macrocycles 3a and 1a in mixed solvents containing DMF and CHCl 3 were measured at room temperature. A total of three experiments were performed per data set and averaged.
Two stock solutions of 3a (1 mM), each prepared in DMF and CHCl 3 respectively, were filtered immediately through a 0.45-µm filter to remove dust and debris, and left to stand for 15-min before each series of measurements. The first measurement started with 3 mL of 3a (1 mM) in DMF, followed by removing a pre-calculated aliquot from the DMF solution that had been measured, to which the same volume of the 3a stock solution in CHCl 3 was added to result in the desired volume percent CHCl 3 while the concentration of 3a was maintained at 1 mM. This procedure was repeated by removing the needed volume of the measured solution out of the cuvette, followed by adding the same volume of the 3a stock solution in CHCl 3 to the cuvette, until measurements were completed on all the compositions of CHCl 3 .

S3
To let the aggregational process reach equilibrium, a 15-min rest period after mixing was allowed before each measurement was performed.  Fluorescence emission spectra of the samples were collected immediately following the above procedure (λ ex = 282 nm, Slit ex = 8 nm, Slit em = 10 nm).

Fluorescence Spectroscopy
All time-resolved intensity decays were measured by using an IBH model 5000 W SAFE time-correlated single photon counting (TCSPC) fluorescence lifetime instrument. A 280 nm light emitting diode (Nano LED) served as the excitation source. Emission was recorded at 450 nm (32 nm bandpass). All experiments were conducted until there were at least 10 4 counts in the peak multichannel analyzer channel. The typical time resolution for an experiment was between 0.04 and 0.05 ns/channel and 1024 total channels were used.
The TCSPC traces were analyzed by using Globals WE (Globals Unlimited), a commercially available nonlinear least-squares analysis software package, and evaluate the reduced χ 2 , residuals and autocorrelation traces to determine the best fit model. The solvent blank was paramatized within a Global analysis strategy to account for its contribution to the sample signal.

Fluorescence Anisotropy
All steady-state fluorescence measurements were performed by using a SLM-AMINCO and the experimentally determined r 0 , r, and τ values, the rotational correlation time θ of the aggregate of 3a was calculated to be 1.94 ns.
The rotational correlation time is in turn given by: where η is solvent viscosity, T temperature in K, R the gas constant, and V the molar volume of the rotating unit (i.e., the aggregate) being examined. Based on the value of θ, the molar volume (V) of the aggregate of 3a was found to be 14.76 nm 3 . If a spherical shape is assumed for the aggregate, a diameter of 3.0 nm, a value very close to the diameter of the macrocyclic molecule, was obtained for the rotating "sphere" formed by 3a, which suggests that the measured rotational correlation time for 3a reflects the spin of the cylindrical stacks of 3a around their long axes.
Instead of assuming a spherical shape for the aggregate of 3a 10 nM in CHCl 3 , a model based on a cylinder consisting of stacked 3a may allow the number of macrocyclic molecules S6 that form such stacks to be estimated. Given that the radius (r) of 3a monomer is 14.9 Å (XRD data, Figure 5), and the molar volume of the aggregate of 3d is 14.76 nm 3 (see above), based on the equation for the volume of a column: The average height (h) of the stacks of 3a is 2.12 nm, which, based on the stacking distance of 3a in a column (3.66 Å, Figure 5), gives an average number of ~6 (5.79) molecules for the stacks of 3a.

Computational Study
Figure S16  Figure S17, the dimer with r = 3.486 Å and θ = 60.5° has the largest binding energy of about -49.77 kcal/mol. The strong binding is most likely due to the strong π−π interaction as well as local dipole interaction between two monomers. Figure S1. 1         The molecular axis is highlighted by a blue arrow. The rotation angle (θ) and interlayer distance (r) are respectively defined as the angle between two molecular axes and the distance between the center of mass of each monomer. Binding Energy (kcal/mol) 3