Metalloporphyrin Dimers Bridged by a Peptoid Helix: Host-Guest Interaction and Chiral Recognition

Co-facial porphyrins have been designed to construct porphyrin tweezers with versatile molecular recognition capabilities. In this study, we synthesized metalloporphyrin⁻peptoid conjugates (MPPCs) displaying two metalloporphyrins on a peptoid scaffold with either achiral unfolded ( ) or helical ( and ) secondary structures. Host⁻guest complexation of MPPCs was realized with various guests of different lengths and basicities, and the extent of complexation was measured by UV-vis and circular dichroism (CD) spectroscopic titration. Intermolecular and intramolecular chirality induction were observed on achiral and chiral peptoid backbones, respectively. Spectroscopic data indicated that a broad scope of achiral guests can be recognized by chiral ; in particular, longer and more flexible guests were seen to bind more tightly on . In addition, chiral provided a distinct CD couplet with dl-, d-, or l-Lys-OMe, which was a result of the diastereomeric host⁻guest complex formation. Our results indicated that MPPCs can recognize, contrast, and analyze various achiral, chiral, or racemic molecules. Based on co-facial metalloporphyrins present on peptoid scaffolds, we developed a novel class of porphyrin tweezers, which can be further utilized in asymmetric catalysis, molecular sensing, and drug delivery.