Control over multiple molecular states with directional changes driven by molecular recognition

Recently, ligand–metal coordination, stimuli-responsive covalent bonds, and mechanically interlinked molecular constructs have been used to create systems with a large number of accessible structural states. However, accessing a multiplicity of states in sequence from more than one direction and doing so without the need for external energetic inputs remain as unmet challenges, as does the use of relatively weak noncovalent interactions to stabilize the underlying forms. Here we report a system based on a bispyridine-substituted calix[4]pyrrole that allows access to six different discrete states with directional control via the combined use of metal-based self-assembly and molecular recognition. Switching can be induced by the selective addition or removal of appropriately chosen ionic guests. No light or redox changes are required. The tunable nature of the system has been established through a combination of spectroscopic techniques and single crystal X-ray diffraction analyses. The findings illustrate a new approach to creating information-rich functional materials.

H-porphine (9): To a solution of 8 (3.88 g, 21.9 mmol) in 45 mL of pyrrole (the solvent) was added methanesulfonic acid (5.7 mL, 87 mmol) dropwise at 0°C. The mixture was allowed to warm to room temperature and then stirred for 8 h under a nitrogen atmosphere. Triethylamine (4.3 mL) was added to the reaction vessel and the resulting mixture was extracted with CH 2 Cl 2 . The organic layer was washed with saturated aqueous NaCl, dried over Na 2 SO 4 , and concentrated in vacuo.
The resulting oil was dissolved in acetone (75 mL) and trifluoroacetic acid (1.6 mL, 21 mmol) was added at room temperature. The reaction mixture stirred for 8 hours and quenched with triethylamine (4.0 mL). The resulting mixture was extracted with CH 2 Cl 2 . The organic layer was washed with saturated aqueous NaCl, dried over Na 2 SO 4 , and concentrated in vacuo. Column chromatography on silica gel (0%-30% ethyl acetate in n-hexane, eluent) gave the desired product 3 (5%, for 2 steps) and its isomer 9 (7%, for 2 steps).
Supplementary Note 3. conpound data for 3 and 9                 Table 2. Data reduction were performed using the Rigaku Americas Corporation's Crystal Clear version 1.40. 5 The structure was solved by direct methods using SIR97 6 and refined by full-matrix least-squares on F 2 with anisotropic displacement parameters for the non-H atoms using SHELXL-97. 7 Structure analysis was aided by use of the programs PLATON98 8 and WinGX. 9 The hydrogen atoms on carbon were calculated in ideal positions with isotropic displacement parameters set to 1.2xUeq of the attached atom (1.5xUeq for methyl hydrogen atoms). The hydrogen atoms on the water molecule were observed in a ∆F map and refined with isotropic displacement parameters.
One of the acetonitrile molecules was disordered about a crystallographic two-fold rotation axis at 1, 1, ¾. The function, use of an Oxford Cryosystems 600 low-temperature device. A total of 1836 frames of data were collected using ω and φ-scans with a scan range of 0.5° and a counting time of 30 seconds per frame. Details of crystal data, data collection and structure refinement are listed in Supplementary Table 3. Data reduction were performed using SAINT V8.27B. 12 The structure was solved by direct methods using SUPERFLIP 13 and refined by full-matrix least-squares on F 2 with anisotropic displacement parameters for the non-H atoms using SHELXL-2013. 7 Structure analysis was aided by use of the programs PLATON98 8 and WinGX. 9 The hydrogen atoms were calculated in idealized positions. The tetrafluoroborate anion was disordered across a crystallographic two-fold rotation axis along ½, y, ¾. Additionally, a molecule of acetonitrile was also disordered about two orientations of approximately 50% occupancy.
The disorder was modeled in the same manner for both molecules. For one DMSO molecule, the variable x was assigned to the site occupancy factors for the atoms in one component of the disorder. The variable (1-x) was assigned to the site occupancy factors for the alternate component. A common isotropic displacement parameter was refined while refining the variable x. The geometry of the DMSO molecules was restrained to be equivalent throughout the refinement process.
In this way, the major component for one DMSO molecule refined to 55 (2)   seconds per frame with a detector offset of +/-109.9°. The data were collected at 100 K using an Oxford Cryostream low temperature device. Details of crystal data, data collection and structure refinement are listed in Supplementary Table 5.
Data collection, unit cell refinement and data reduction were performed using Agilent Technologies CrysAlisPro V 1.171.37.31. The structure was solved by direct methods using SIR97 6 and refined by full-matrix least-squares on F 2 with anisotropic displacement parameters for the non-H atoms using SHELXL-2013. 7 Structure analysis was aided by use of the programs PLATON98 8 and WinGX. 9 The hydrogen atoms were calculated in ideal positions with isotropic displacement parameters set to 1.2xUeq of the attached atom (1.5xUeq for methyl hydrogen atoms). The hydrogen atoms bound to nitrogen were located in a ∆F map and refined with isotropic displacement parameters.
A molecule of acetonitrile was badly disordered about a crystallographic inversion center at 0, ½, 1. Attempts to model the disorder were unsatisfactory. The contributions to the scattering factors due to the solvent molecule were removed by use of the utility SQUEEZE 15 in PLATON98.

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The function, Σw(|F o | 2 -|F c | 2 ) 2 , was minimized, where w = 1/[(σ(F o )) 2 + (0.0496*P) 2 + (11.5937*P)] and P = (|F o | 2 + 2|F c | 2 )/3. R w (F 2 ) refined to 0.118, with R(F) equal to 0.0462 and a goodness of fit, S, = 1.02. Definitions used for calculating R(F), R w (F 2 ) and the goodness of fit, S, are given below. 9 The data were checked for secondary extinction effects but no correction was necessary. Neutral atom scattering factors and values used to calculate the linear absorption coefficient are from the International Tables for X-ray Crystallography (1992). 10  1.5418 Å) with collimating mirror monochromators. A total of 965 frames of data were collected using ω-scans with a scan range of 1° and a counting time of 2 seconds per frame with a detector offset of +/-40.5° and 5 seconds per frame with a detector offset of +/-111°. The data were collected at 100 K using an Oxford Cryostream low temperature device.
Details of crystal data, data collection and structure refinement are listed in Supplementary Table 6. Data collection, unit cell refinement and data reduction were performed using Agilent Technologies CrysAlisPro V 1.171.37.31. 14 The structure was solved by direct methods using SuperFlip 12 and refined by full-matrix least-squares on F 2 with anisotropic displacement parameters for the non-H atoms using SHELXL-2013. 7 Structure analysis was aided by use of the programs PLATON98 8 and WinGX. 9 The hydrogen atoms on carbon were calculated in ideal positions with isotropic displacement parameters set to 1.2xUeq of the attached atom (1.5xUeq for methyl hydrogen atoms). The hydrogen atoms on the pyrrole nitrogen atoms were observed in a ∆F map and refined with isotropic displacement parameters. Cryosystems 600 low-temperature device. A total of 629 frames of data were collected using w and φ-scans with a scan range of 1.1° and a counting time of 85 seconds per frame. Details of crystal data, data collection and structure refinement are listed in Supplementary Table 7. Data reduction were performed using SAINT V8.27B. 12 The structure was solved by direct methods using SHELXT 11 and refined by full-matrix least-squares on F 2 with anisotropic displacement parameters for the non-H atoms using SHELXL-2014/7. 7 Structure analysis was aided by use of the programs PLATON98 8 and

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WinGX. 9 The hydrogen atoms bound to carbon atoms were calculated in idealized positions. The hydrogen atoms on the water molecule were observed in a ∆F map and constrained in a riding model with Uiso set to 1.5xUeq of the water molecule, O3. The hydrogen atoms on the pyrrole nitrogen atoms were observed in a ΔF map and refined with isotropic displacement parameters.
The calixpyrrole di-hydrate complex resides around a crystallographic inversion center at ½, ½, ½. The pyrrole NH groups H-bond to the water molecule, which, in turn, is H-bound to the pyridine ring. The terminal methyl group of the 2-methylbutyl group is disordered. The disorder was modeled by assigning the variable x to the site occupancy factor for C20 and (1-x) was assigned to the site occupancy factor for the alternate component, C20a, of the disordered atom.
A common isotropic displacement parameter was refined for both atoms while refining x. The site occupancy for C20 refined to 52 (1) were checked for secondary extinction but no correction was necessary. Neutral atom scattering factors and values used to calculate the linear absorption coefficient are from the International Tables for X-ray Crystallography (1992). 10 All figures were generated using SHELXTL/PC. 11 Tables of positional and thermal parameters, bond lengths and angles, torsion angles and figures may be obtained from the Cambridge Crystallographic Data Centre.