Molecular Machines and Assemblies

Molecular Machines and Assemblies

Molecular robots are electromechanical machines that are integrated with feedback control systems to achieve autonomous operation at the nanoscale. This goal is increasingly becoming a reality. While many molecular actuators, in the form of molecular machines, are being realized, the true revolution in control will come once we begin to understand the mechanisms of motion. To this end, we are focused on quantifying the thermodynamics and kinetics of movement. We also contend that the integration with control systems will be facilitated with voltage-gated molecular systems. With that goal in mind, we have developed redox-active ligands that can serve as switches to the investigation of mechanical motion at the molecular level. Attention is focused on the Cu(I) as a labile transition metal coupled with non-innocent bridging ligands. . We intend to broaden the diversity of ligand-based switching to other metals and extend the complexity of what can be achieved using catenates and rotaxanes that can perform a range of functions -- such as molecular muscles. See also our work on light-driven foldamers for binding and releasing anions.

References

128. Benson, C. R.; Maffeo, C.; Fatila, E. M.; Liu, Y.; Sheetz, E. G.; Aksimentiev, A.; Singharoy, A.; Flood, A. H., “Inchworm movement of two rings switching onto a thread by biased Brownian diffusion: a three-body problem” Proc. Natl. Acad. Sci. USA 2018, 38, 9391-9396. DOI

115. Qiao, B.; Liu, Y.; Lee, S.; Pink, M.; Flood, A. H., High-yield Synthesis and Acid-base Response of Phosphate-templated [3]Rotaxanes, Chem. Commun. 2016, 52, 13675-13678. DOI

114. Benson, C. R.; Fatila, E. M.; Lee, S.; Marzo, M. G.; Pink, M.; Mills, M. B.; Preuss, K. E.; Flood, A. H., Extreme Stabilization and Redox Switching of Organic Anions and Radical Anions by Large-cavity, CH Hydrogen-Bonding Cyanostar Macrocycles, J. Am. Chem. Soc. 2016, 138, 15057-15065. DOI (See highlight in Cutting Edge Chemistry from the ACS)

109. Benson, C. R.; Share, A. I.; Marzo, M. G.; Flood, A. H., Double switching of two rings in palindromic [3]pseudorotaxanes: Cooperativity and mechanism of motion, Inorg. Chem. 2016, 55, 3767-3776 DOI

95. Benson, C. R.; Hui, A. K.; Parimal, K.; Cook, B. J.; Chen, C.-H.; Lord, R. L.; Flood, A. H.; Caulton, K. C., Amplifying the Redox Activity of a bis-Tetrazine Pincer Ligand, Dalton. 2014, 43, online. DOI

94. Manck, L. E.; Benson, C. R.; Share, A. I.; Park, H.; Vander Griend, D. A.; Flood, A. H., Self-Assembly Snapshots of a 2×2 Copper(I) Grid, Supramol. Chem. 2014, 26, accepted (Special Issue for the ISMSC-8, Arlington, VA, July 7-11, 2013)

88. Book Chapter: Benson, C. R.; Share, A. I., Flood, A. H., Bioinspired Molecular Machines, in Bioinspiration and Biomimicry in Chemistry: Reverse Engineering Nature, Ed. Swiegers, G. F., Wiley, Hoboken, 2012. ebook

85. Book Chapter: Flood, A. H.; Kaifer, A. E., Supramolecular Electrochemistry, (Volume 2: Techniques), in Supramolecular Chemistry: From Molecules to Nanomaterial, Eds. Gale, P. A.; Steed, J. W., John Wiley and Sons, 2012. DOI

78. Parimal, K.; Vyas, S.; Chen, C.-H.; Hadad, C. M.; Flood, A. H., Bond Elongation in the Anion Radical of Coordinated Tetrazine Ligands: A Crystallographic, Spectroscopic and Computational Study of a Reduced {Re(CO)₃Cl} Complex, Inorg. Chim. Acta. 2011, 374, 620-626. Special Issue Dedicated to Wolfgang Kaim. DOI

68. Parimal, K.; Witlicki, E. H.; Flood, A. H., Two different classes of architectures can be interconverted by reduction of a self-sorting mixture, Angew. Chem. Int. Ed. 2010, 49, 4628-4632. DOI

67. Share, A. I.; Flood, A. H., Thinking inside and outside the box (News and Views Article), Nature Chem. 2010, 2, 349-350. DOI

66. Share, A. I.; Parimal, K.; Flood, A. H., Bi-lability is defined when one electron is used to switch between concerted and step-wise pathways in Cu(I)-based bi-stable [2/3]pseudorotaxanes, J. Am. Chem. Soc. 2010, 132, 1665-1675. DOI

62. Li, G.; Parimal, K.; Vyas, S.; Hadad, C. M.; Flood, A. H.; Glusac, K. D., Pinpointing the extent of electronic delocalization in the Re(I)-to-tetrazine charge-separated excited state using time-resolved infrared spectroscopy, J. Am. Chem. Soc. 2009, 131, 11656-11657. DOI

57. McNitt, K. A.; Parimal, K.; Share, A. I.; Fahrenbach, A. C.; Witlicki, E. H.; Pink, M.; Bediako, D. K.; Plaisier, C. L.; Le, N.; Heeringa, L. P.; Vander Griend, D. A.; Flood, A. H., Reduction of a redox-active ligand drives switching in a Cu(I) pseudorotaxane by a bimolecular mechanism, J. Am. Chem. Soc. 2009, 131, 1305-1313. DOI

47. Li, Y.; Huffman, J. C.; Flood, A. H. “Can Terdentate 2,6-Bis(1,2,3-Triazol-4-yl)Pyridines form Stable Coordination Compounds?” Chem. Commun. 2007, 2692-2694. DOI

Book Chapter

*Flood, A. H.; Kaifer, A. E., Supramolecular Electrochemistry, for Supramolecular Chemistry: From Molecules to Nanomaterials, Eds. Steed, J. W.; Gale, P. A. John Wiley and Sons, in press

Collaborations on Molecular Switches

We are extending the capabilities learnt on Cu(I)-based supramolecular switches to redox-active systems of collaborators

Yi Liu

54. Koshkakaryan, G.; Parimal, K.; He, J.; Zhang, X.; Abliz, Z.; Flood, A. H.; Liu, Y., pi-Stacking enhanced dynamic and redox-switchable self-assembly of donor-acceptor metallo-[2]catenanes from diimide derivatives and crown ethers, Chem. Eur. J. 2008, 14, 10211-10218. DOI

Jan O Jeppesen

136. Andersen, S.; Saad, A. W.; Kristensen. R.; Pedersen T. S.; O’Driscoll, L. J.; Flood, A. H.; Jeppesen, J. O., Salts accelerate the switching kinetics of a cyclobis(paraquat-p-phenylene)[2]rotaxane, Org. Biol. Chem. 2019, 17, 2432-2441. DOI

98. Andersen, S. S.; Share, A. I.; Poulsen, B. L. C.; Korner, M.; Duedal, T.; Benson, C. R.; Hansen, S. W.; Jeppesen, J. O.; Flood, A. H., Mechanistic Evaluation of Motion in Redox-Driven Rotaxanes Reveal Longer Linkers Hasten Forward Escapes and Hinder Backward Translations, J. Am. Chem. Soc. 2014, 136, 6373-6384. DOI

90. Sorensen, A.; Andersen S. S.; Flood, A. H.; Jeppesen, J. O., Pressure effects in the synthesis of isomeric rotaxanes, Chem. Commun. 2013, 49, 5936-5938. DOI

87. Andersen, S. S.; Jensen, M.; Sorensen, A.; Miyazaki, E.; Takimiya, K.; Laursen, B. W.; Flood, A. H.; Jeppesen, J. O., Anion effects on the cyclobis(paraquat-p-phenyelen) host, Chem. Commun. 2012, 48, 5157-5159. DOI

82. Hansen, S. W.; Stein, P. C.; Sorensen, A.; Share, A. I.; Witlicki, E. H.; Kongsted, J.; Flood, A. H.; Jeppesen, J. O., Quantification of the pi-pi Interactions that Govern Tertiary Structure in Donor-Acceptor [2]Pseudorotaxanes, J. Am. Chem. Soc. 2012, asap. DOI

49. Nygaard, S.; Laursen, B. W.; Hansen, T. S.; Bond, A. D.; Flood, A. H.; Jeppesen, J. O., “Preparation of cyclobis(paraquat-p-phenylene)-based [2]rotaxanes without flexible glycol chains”, Angew. Chem. Int. Ed. 2007, 46, 6093-6097. DOI

48. Nygaard, S.; Hansen, S. W.; Huffman, J. C.; Jensen, F.; Flood, A. H.; Jeppesen, J. O. “Two Classes of Alongside Charge-Transfer Interactions Defined in One [2]Catenane,” J. Am. Chem. Soc. 2007, 129, 7354-7363. DOI

46. Nygaard, S.; Liu, Y.; Stein, P. C.; Flood, A. H.; Jeppesen, J. O. “Using Molecular Force to Overcome Steric Barriers in a Spring-Like Molecular Ouroborous,” Adv. Funct. Mat. 2007, 17, 751-762.

42. Nygaard, S.; Flood, A. H.; Jeppesen, J. O.; Bond, A. D. “Cis- andTrans-Bis(2-cyanoethylsulfanyl)(decane-1,10-diyldithio)Tetrathiafulvalene,” Acta. Cryst. C 2006, 62, 677-680.