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Leveraging Torsional and Steric Strains: A Pre-macrocyclization Strategy Enables Conformation-Specific Fullerene Binding in m-Cyclophanes |
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| Authors: | Dr Pawan Kumar V B Raja Mani Kandan Prabukumar Balakrishnan Dr P K Sudhadevi Antharjanam Dr Venkatakrishnan Parthasarathy |
| Institution: | 1. Department of Chemistry, Indian Institute of Technology Madras, 600036 Chennai, Tamil Nadu, India
These authors contributed equally to this work. Contribution: Formal analysis (equal), Investigation (equal), Methodology (equal), Validation (equal);2. Department of Chemistry, Indian Institute of Technology Madras, 600036 Chennai, Tamil Nadu, India These authors contributed equally to this work. Contribution: Data curation (equal), Formal analysis (equal), Resources (equal), Software (equal);3. Department of Chemistry, Indian Institute of Technology Madras, 600036 Chennai, Tamil Nadu, India;4. Sophisticated Analytical Instrument Facility (SAIF), Indian Institute of Technology Madras, 600036 Chennai, Tamil Nadu, India Contribution: Data curation (supporting), Formal analysis (supporting), Resources (supporting), Software (supporting) |
| Abstract: | Though the chemistry of resorcinarenes is half a century old, the conformationally-locked resorcinarene crowns are generally constructed using hydrogen bonds or covalent tethers. Often, covalent tethering involves extra post-macrocyclization steps involving upper-rim functionalities. We have leveraged the torsional and steric strains through α-substituents of the lower-rim C-alkyl chains and accomplished conformationally-rigid fluorescent m-cyclophane deep-crowns in a predetermined way. The strategy offers a pre-macrocyclization route conserving upper-rim functionalities, an aspect overlooked in resorcinarene chemistry. X-ray structural and computational analyses unveil the cause for conformational rigidity in m-cyclophanes due to α-branching in C-alkyls (linear vs. α-/β-branched). The conformationally-locked fluorescent deep-crown with a preorganized cavity captures hydrophobic spherical guest C60 in both solution and solid states specifically, when compared to conformationally-dynamic boats, enabling conformation-specific binding. |
| Keywords: | Conformational Rigidity Cyclophane Fullerenes Host-Guest Interaction Supramolecular |