Molecular Recognition, Nobel Prizes, and MRT
Richard P. Feynman, 1965 Nobel Laureate in physics, made the following prophetic observation in 1960  about the prospect of rearranging atoms at the molecular level: “What would the properties of materials be if we could really arrange the atoms the way we want them? They would be very interesting to investigate theoretically. I can’t see exactly what would happen, but I can hardly doubt that when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do.”
Already, in the 1960s, there was a stirring in the minds of many scientists about the question of how molecules recognize each other, often referred to as molecular recognition. Strong interest in science developed in the United States following World War II spurred by competition with the USSR, increased funding of research at universities by government, and GI Bill opportunities for World War II veterans. Synthetic organic chemistry developed rapidly in this environment and became an important factor in the creation of new pre-designed molecules that fueled production of novel products that changed the face of society and still does.
Supramolecular chemistry, macrocyclic chemistry, and nanoscience — building blocks of molecular recognition — had their roots in this period with significant developments led by Charles J. Pedersen, Jean-Marie Lehn, and Donald J. Cram who received the 1987 Nobel Prize in chemistry for their pioneering work . This Prize was awarded for “their development and use of molecules with structure-specific interactions of high selectivity.”
The 1970s and 1980s were fruitful times for workers in the field of molecular recognition. This field is central to understanding selective interactions in chemistry and biology and attracted the attention of many research workers. Developments in these decades were aided by characterization, using physical chemistry methods, of chemical interactions between ligand hosts and guest species such as metal ions, anions, and neutral molecules [3-6]. As the field broadened, greater attention was given to rearranging molecules at the molecular level to create systems capable of accomplishing tasks that were formerly impossible.
2016 Nobel Prize in Chemistry. The 2016 Nobel Prize in Chemistry was given to Jean-Pierre Sauvage, Sir J. Fraser Stoddart, and Bernard Feringa  for the design and production of molecular machines, i.e., molecular arrangements that mimic machine action at a macro level.
These scientists developed molecules with controllable movements, which can perform a task when energy is added. If you think about it, that is what machines that we use daily do. An automobile has controllable movements and can take us places when energy is added. On the Nobel Prize website , the rationale for awarding the 2016 Nobel Prize in Chemistry is given as follows:
- “The development of computing demonstrates how the miniaturization of technology can lead to a revolution. The 2016 Nobel Laureates in Chemistry have miniaturized machines and taken chemistry to a new dimension.
- “The first step towards a molecular machine was taken by Jean-Pierre Sauvage in 1983, when he succeeded in linking two ring-shaped molecules together to form a chain, called a catenane. Normally, molecules are joined by strong covalent bonds in which the atoms share electrons, but in the chain they were instead linked by a freer mechanical bond. For a machine to be able to perform a task it must consist of parts that can move relative to each other. The two interlocked rings fulfilled exactly this requirement.
- “The second step was taken by Fraser Stoddart in 1991, when he developed a rotaxane. He threaded a molecular ring onto a thin molecular axle and demonstrated that the ring was able to move along the axle. Among his developments based on rotaxanes are a molecular lift, a molecular muscle, and a molecule-based computer chip.
- “Bernard Feringa was the first person to develop a molecular motor; in 1999 he got a molecular rotor blade to spin continually in the same direction. Using molecular motors, he has rotated a glass cylinder that is 10,000 times bigger than the motor and also designed a nanocar.
- “2016’s Nobel Laureates in Chemistry have taken molecular systems out of equilibrium’s stalemate and into energy-filled states in which their movements can be controlled. In terms of development, the molecular motor is at the same stage as the electric motor was in the 1830s, when scientists displayed various spinning cranks and wheels, unaware that they would lead to electric trains, washing machines, fans and food processors. Molecular machines will most likely be used in the development of things such as new materials, sensors and energy storage systems.”
The achievements that led to the 2016 Nobel Prize confirm Feynman’s suggestion  that when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do.
The importance of molecular recognition in science is attested to by the awarding of Nobel Prizes in 1987 and 2016 to six individuals. Understanding molecular recognition at the molecular level allows creative scientists to design and construct molecular systems that mimic processes that occur at the macro level. This activity feeds upon itself as evidenced by the enthusiasm and productivity of a large segment of the scientific community in molecular recognition-based research .
Molecular Recognition Technology (MRT). MRT is one commercial metal separations enterprise that has its origins in the molecular recognition mix of the 1960s and succeeding decades that produced these Nobel Prizes. The term “MRT” was coined by Steven Izatt in 1989  to describe the process used by newly founded IBC Advanced Technologies, Inc. (IBC) to accomplish highly selective, green chemistry metal separations without the use of solvent extraction or corrosive chemicals. Adding the word technology to molecular recognition signifies the accomplishment of practical applications (i.e., products or systems for which a customer will pay money). IBC was created in 1988 as a spin-off company from the molecular recognition research program of Reed M. Izatt, Jerald S. Bradshaw, and James J. Christensen (deceased 1987) at Brigham Young University (BYU) . Creation of IBC was greatly aided through receipt by BYU of a large Centers of Excellence Grant (1997-1992) to these professors from the State of Utah aimed at commercializing their research results. Professors Izatt and Bradshaw received the 1996 National American Chemical Society Award for Separation Sciences and Technology based on their innovative work in metal separations . Inscribed on the award plaque were the words: For advancing the separations science of metals and for new technology to forward industrial-scale recovery of metals from aqueous solutions.
The potential for the MRT green chemistry separation process, as visualized by these professors, is presented in the opening paragraph of a 1988 communication to Analytical Chemistry . “Sir: The recent permanent attachment of macrocycles such as the crown ethers to silica gel via a hydrocarbon-type linkage has made possible the design of systems capable of the selective and quantitative removal of cations from aqueous solutions. These systems can be operated indefinitely without loss of the expensive macrocycle and maintain the selectivity shown toward metal ions in aqueous solution by the particular macrocycle in the free state. These systems are of potential value in concentrating cations present at the nanogram-per milliliter level, making their analysis by conventional procedures possible, and in selectively removing either wanted or unwanted metal cations from solutions in which they are present in the milligram-per-milliliter to the nanogram-per milliliter range.”
Important features of the MRT system described in this Analytical Chemistry article have been further developed in subsequent decades to make MRT an important global player in current commercial metallurgical metal separations and recovery. High selectivity by proprietary SuperLig® products (trade name of silica gel-tether-ligand particle) for targeted metals is the critical component of the MRT system. High selectivity results in minimal loss of targeted metal minimizing recovery steps downstream and makes possible a relatively simple separation process . The significant positive environmental consequences of MRT processes in metal separations and recovery have been presented  together with the favorable capital and operating advantages of these systems [14-16].
Practical Metal Separations and Recovery Using MRT. A disruptive technology in highly selective metallurgical separations and recovery, MRT is a practical illustration of the prediction by Feynman  that remarkable results could be obtained if we could really arrange the atoms the way we want them. Recent green chemistry separations of all sixteen rare earth elements (REE) from a pregnant leach solution (PLS) derived from Bokan-Dotson Ridge virgin ore illustrates the power of being able to design molecules and use them for desired metal separations [15-18]. Separations of individual REE from each other were first achieved at the laboratory scale [17a]. These results provided the information necessary to scale up the separation process to pilot plant scale which was subsequently done. In the pilot plant, SuperLig® products were effective in separating the suite of REE into heavy (Sm-Lu) and light (Pr, Nd, Y) groups (Ce and Sc had been separated previously) [17b,17c]. The heavy REE group was further subdivided into Sm-Dy and Ho-Lu subgroups [17d]. Individual REE can be separated at desired purity levels from any of these groups. This capability was demonstrated by separation of Dy at the 99.99% level versus other REE from the Sm-Dy subgroup [17e]. The purity of the separated Dy was confirmed by two independent laboratories [17f]. High metal selectivity by the SuperLig® resin results in many fewer stages in the separations and reduces the need for separations downstream to recover lost REE. Non-use of solvents and corrosive chemicals also make significant contributions to favorable operating and capital expenses. It is significant that Dy and other REE are recovered at the 99% level versus the constituents of the original PLS solution. REE are not lost to the environment during separation stages. This is a remarkable accomplishment considering the much lower recovery rates of REE in Chinese operations and in the Mt. Pass operation when it was functioning. Overall recovery of REE values at Mt. Pass were reported to be 65-70% and the tailings assayed around 1-2 % REE .
MRT is used worldwide for the green chemistry separations of platinum group metals (PGM) from primary and secondary sources [14,15,20]. Significant advantages accruing through use of MRT include simplicity of the separation and recovery systems saving space, labor, and time; non-use of solvents and highly corrosive chemicals; high metal selectivity resulting in reduced number of separation stages and lowered space requirements; marked reduction of PGM inventory time; high PGM recovery rates; and use of modular systems on skids making PGM separations in localized global regions possible.
MRT, Nobel Prize Winners, and Projections for the Future. In 1977, Jim Christensen and I organized the First Symposium on Macrocyclic Chemistry held at BYU in Provo, UT . A series of symposia followed and today the symposium is held annually in locations worldwide under the name International Symposium on Macrocyclic and Supramolecular Chemistry (ISMSC). In 1991, Jerald Bradshaw and Steven Izatt arranged with officers of the Symposium to establish an Izatt-Christensen Award, named after the founders, to recognize outstanding and creative work in macrocyclic chemistry. This Award is presented annually at ISMSC meetings. A book edited by me and published by Wiley presents papers by 21 of the 26 recipients of the Award from 1991-2016 . This book contains chapters authored by Jean-Pierre Sauvage, first recipient of the Award in 1991 , and J. Fraser Stoddart, third recipient of the Award in 1993 . These Awards recognized the work done by these individuals that resulted in their receipt of the 2016 Nobel Prize. Professor Sauvage recognized the significance of the Award in his chapter  as follows: “In 1991, the senior author of this chapter, Jean-Pierre Sauvage, was awarded the Izatt-Christensen Award in Macrocyclic Chemistry. This event had very important consequences for his research and his career. Obviously, the work done in his group became more visible to the community. In addition, this recognition convinced him that he had been right 7 or 8 years earlier when he reoriented his research themes to follow contemporary research directions in relation to interlocking ring compounds.”
IBC has a close association with the Symposium and with individuals who have made significant contributions in the molecular recognition field. Feynman’s projections  have been vindicated and there are exciting prospects for the future. The world of the 21st century aims at reduction of dependence on fossil fuel-derived energy sources and increased use of high technology items as global population and affluence increase. MRT can have significant positive effects on both outcomes through more effective green chemistry separation and recovery from virgin and secondary sources of the rare metals that are required for their accomplishment. Wastage of the global metal supply is a tremendous and growing problem in our society [13,24,25]. Highly selective green chemistry processes such as MRT are needed to increase metal sustainability and to decrease environmental and health burdens caused by ineffective metal separation and recovery processes. Feynman  visualized this outcome in his thought that when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do. Development of commercial MRT processes for a wide variety of metal separations over the past quarter of a century  demonstrates the wide variety of different things that we can do when we are able to design highly selective, green chemistry separation systems using molecular recognition principles.
- Feynman, R.P., 1960. There’s Plenty of Room at the Bottom, Engineering and Science, 23, 22-36.
- Press Release: The Nobel Prize in Chemistry 1987. Accessed October 24, 2016.
- Izatt, R.M., Bradshaw, J.S., Nielsen, S.A., Lamb, J.D., Christensen, J.J., Sen, D., 1985. Thermodynamic and Kinetic Data for Cation-Macrocycle Interaction, Chemical Reviews, 85, 271-339.
- Izatt, R.M., Pawlak, K., Bradshaw, J.S., Bruening, R.L., 1991. Thermodynamic and Kinetic Data for Macrocycle Interaction with Cations and Anions, Chemical Reviews, 91, 1721-2085.
- Izatt, R.M., Pawlak, K., Bradshaw, J.S., Bruening, R.L., 1995. Thermodynamic and Kinetic Data for Macrocycle Interaction with Cations, Anions and Neutral Molecules, Chemical Reviews, 95, 2529‑2586.
- Christensen, J.J., Eatough, D.J., Izatt, R.M., 1975. Handbook of Metal Ligand Heats and Related Thermodynamic Quantities, 2nd ed.; Dekker, M.; New York, 495 pp.
- Press Release: The Nobel Prize in Chemistry 2016, Accessed October 23, 2016.
- Izatt, R.M. (Ed.)., 2016. Macrocyclic and Supramolecular Chemistry: How Izatt-Christensen Award Winners Shaped the Field, Wiley, Oxford, U.K., 481 pp.
- IZA 89. Izatt, S.R., Personal Communication, July 26, 2015, as documented in IBC archives, 1989.
- Izatt, R.M., How Molecular Recognition Developed into Molecular Recognition Technology, Accessed October 23, 2016.
- Reed M. Izatt and Jerald S. Bradshaw, Joint Recipients of the 1996 American Chemical Society Award in Separations Science and Technology, Chemical & Engineering News, January 22, 1996, p 56.
- Izatt, R.M.; Bruening, R.L.; Bruening, M.L.; Tarbet, B.J.; Krakowiak, K.E.; Bradshaw, J.S.; Christensen, J.J. 1988, Removal and Separation of Metal Ions from Aqueous Solutions Using a Silica Gel Bonded Macrocycle System, Analytical Chemistry, 60, 1825-1826.
- Izatt, R.M., Izatt, S.R., Bruening, R.L., Izatt, N.E., Moyer, B.A., 2014, Challenges to Achievement of Metal Sustainability in Our High‐Tech Society, Chemical Society Reviews, 43, 2451–2475.
- Izatt, R.M., Izatt, S.R., Izatt, N.E., Krakowiak, K.E., Bruening, R.L., Navarro, L., 2015, Industrial Applications of Molecular Recognition Technology to Green Chemistry Separations of Platinum Group Metals and Selective Removal of Metal Impurities from Process Streams, Green Chemistry, 17, 2236–2245.
- Izatt, S.R., McKenzie, J.S., Bruening, R.L., Izatt, R.M., Izatt, N.E., Krakowiak, K.E., 2016. Selective Recovery of Platinum Group Metals and Rare Earth Metals from Complex Matrices using a Green Chemistry-Molecular Recognition Technology Approach. In Izatt, R.M. (Ed.), Metal Sustainability: Global Challenges, Consequences, and Prospects, Wiley, Oxford, U.K.
- Izatt, R.M., High Strength Permanent Magnets: An Untapped Source of Critical Rare Earth Metals, but can the Metals be Economically Recovered?, Accessed October 23, 2016.
- (a) Press release: March 2, 2015, Ucore Successfully Separates Entire Suite of Individual Rare Earth Elements at High Purity, Accessed October 23, 2016; (b) Press release: May 24, 2016, Ucore Separates Scandium at 99%+ Recovery via SuperLig®-One Pilot Plant, Accessed September 14, 2016; (c) Press Release: June 7, 2016, Ucore separates HREE and LREE Classes at 99%+ Purity via SuperLig®-One Pilot Plant, Accessed October 23, 2016; (d) Press Release: July 5, 2016, Ucore Separates Dy and Ho Sub-Groups at 99%+ Purity via SuperLig®-One Pilot Plant, Accessed October 23, 2016; (e) Press Release: August 15, 2016, Ucore Produces 99.99% Dysprosium via SuperLig®-One Pilot Plant, Accessed October 23, 2016; (f) Press Release: September 26, 2016, Ucore Confirms Success of SuperLig®-One Pilot Plant via Independent Analysis, Accessed October 23, 2016
- Izatt, S.R., McKenzie, J.S., Izatt, N.E., Bruening, R.L., Krakowik, K.E., Izatt, R..M., Molecular Recognition Technology: A Green Chemistry Process for Separation of Individual Rare Earth Metals, Accessed September 14, 2016.
- Pradip, Fuerstenau, D.W., 2013, Design and Development of Novel Flotation Reagents for the Benefication of Mountain Pass Rare Earth Ore, Minerals & Metallurgical Processing, 30, 1-9.
- Izatt, R.M., Precious Metals: A Resource Worth Recycling, Accessed October 23, 2016.
- Izatt, R.M., Bradshaw, J.S., Izatt, S.R., Harrison, R.G., 2016. The Izatt-Christensen Award in Macrocyclic and Supramolecular Chemistry: A 25-Year History (1991-2016), In Izatt, R.M. (Ed.), Macrocyclic and Supramolecular Chemistry: How Izatt-Christensen Award Winners Shaped the Field Wiley, Oxford, U.K. 1-9.
- Sauvage, J-P., Duplan, B., Niess, F., 2016. Contractile and Extensile Molecular Systems: Towards Molecular Muscles, In Izatt, R.M. (Ed.), Macrocyclic and Supramolecular Chemistry: How Izatt-Christensen Award Winners Shaped the Field Wiley, Oxford, U.K. 444-464.
- McGonigal, P.R., Stoddart, J.F., 2016. Serendipity, In Izatt, R.M. (Ed.), Macrocyclic and Supramolecular Chemistry: How Izatt-Christensen Award Winners Shaped the Field Wiley, Oxford, U.K. 444-464, 389-414.
- Williams, I.D., 2016. Global Metal Reuse, and Formal and Informal Recycling from Electronic and Other High-Tech Wastes, In Izatt, R.M. (Ed.), Metal Sustainability: Global Challenges, Consequences, and Prospects, Wiley, Oxford, U.K. 23-51.
- Izatt, R.M., Izatt, Hagelüken, C., 2016. Recycling and Sustainable Utilization of Precious and Specialty Metals, In Izatt, R.M. (Ed.), Metal Sustainability: Global Challenges, Consequences, and Prospects, Wiley, Oxford, U.K. 1-22.
- Izatt, R.M., Izatt, S.R., Izatt, N.E., Krakowiak, K.E., Bruening, R.L., Green Chemistry Molecular Recognition Processes Applied to Metal Separations in Ore Beneficiation, Element Recycling, Metal Remedation, and Elemental Analysis. in Beach, E.S. and Kundu, S., (Eds.) Handbook of Green Chemistry Volume 12 – Tools for Green Chemistry. (Anastas, P.T., (Ed). Handbook of Green Chemistry Series.) Wiley-VCH, Weinheim, Gremany, in Press.
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Reed M. Izatt received a BS degree in Chemistry from Utah State University (1951) and a PhD degree in Chemistry with an Earth Sciences minor ... <Read more about Reed M. Izatt, PhD>