Introductory Perspective Toward complex matter: Supramolecular chemistry and self-organization Jean-Marie Lehn* Institut de Science et d’Inge´nierie Supramole´culaires, Universite´Louis Pasteur, 67000 Strasbourg, France and Colle`ge de France, 75005 Paris, France s the wind of time blows into the sails and provide a vision. This essay therefore patterns (hydrogen bonding arrays, se- Aof space, the unfolding of the uni- will not be extensively documented (numer- quences of donor and acceptor groups, ion verse nurtures the evolution of matter ous reviews and books are available) but coordination sites, etc.). This venture in- under the pressure of information. From rather outline some conjectures for the fu- volved the design and investigation of divided to condensed and on to organized, ture, mainly based on, illustrated by, and more or less strictly preorganized molec- living, and thinking matter, the path is extrapolated from work performed in the ular receptors of numerous types, capable toward an increase in complexity through author’s laboratories. Looking toward the of binding specific substrates with high self-organization. horizon of supramolecular chemistry, and efficiency and selectivity. Thus emerges the prime question set to more generally of supramolecular science Three overlapping phases may be consid- science, in particular to chemistry, the (1, 3), special attention will be given to ered in the development of supramolecular science of the structure and transforma- exposing the forest(s) rather than to describ- chemistry, each exploring a main theme. tion of matter: how does matter become ing the trees! The first is that of molecular recognition complex? What are the steps and the and its corollaries, supramolecular reactiv- processes that lead from the elementary Supramolecular Chemistry and the ity, catalysis, and transport; it relies on de- particle to the thinking organism, the Information Paradigm sign and preorganization and implements (present!) entity of highest complexity? One of the major lines of development of information storage and processing. And there are two linked questions: an chemical science resides in the ever The second concerns self-assembly ontogenetic one, how has this happened, clearer perception, deeper analysis, and and self-organization, i.e., self-processes in how has matter become complex in the more deliberate application of the infor- general; it relies on design and implements history of the universe leading up to the mation paradigm in the elaboration and programming and programmed systems. evolution of the biological world, and an transformation of matter, thus tracing the The third, emerging phase, introduces PERSPECTIVE epigenetic one, what other and what path from merely condensed matter to adaptation and evolution; it relies on self- INTRODUCTORY higher forms of complex matter can there more and more highly organized matter organization through selection in addition be to evolve, are there to be created? toward systems of increasing complexity. to design, and implements chemical diver- Chemistry provides means to interro- In chemistry, like in other areas, the lan- sity and ‘‘informed’’ dynamics. gate the past, explore the present, and guage of information is extending that of build bridges to the future. constitution, structure, and transforma- From Preorganization Toward Molecular chemistry has created a wide tion as the field develops toward more and Self-Organization and Programmed range of ever more sophisticated mole- more complex architectures and behav- Systems: Design cules and materials and has developed a iors. It will profoundly influence our per- Supramolecular chemistry has first relied on SPECIAL FEATURE very powerful arsenal of procedures for ception of chemistry, how we think about preorganization for the design of molecular constructing them from atoms linked by it, how we perform it. receptors effecting molecular recognition, covalent bonds. Supramolecular chemistry has paved the catalysis, and transport processes (1, 2). Beyond the molecule, supramolecular way toward apprehending chemistry as an Supramolecular preorganization also chemistry aims at developing highly com- information science through the implemen- has provided new ways and means to plex chemical systems from components tation of the concept of molecular informa- chemical synthesis (1, 7–9). Supramolecu- interacting by noncovalent intermolecular tion with the aim of gaining progressive lar, noncovalent synthesis, i.e., the con- forces (1, 2). It has over the last quarter of control over the spatial (structural) and struction of the supramolecular entities a century grown into a major field and has temporal (dynamic) features of matter and themselves, rests on the making and fueled numerous developments at the in- over its complexification through self- breaking of noncovalent bonds following terfaces with biology and physics, thus organization, the drive to life (4–6). an Aufbau strategy incorporated into the giving rise to the emergence and estab- Supramolecular chemistry has devel- design of the molecular components. On lishment of supramolecular science and oped as the chemistry of the entities gen- the other hand, supramolecular assistance technology, as a broad multidisciplinary erated by intermolecular noncovalent in- to synthesis provides a powerful tool in- and interdisciplinary domain providing a teractions (1, 2). Through the appropriate volving first the noncovalent synthesis of a highly fertile ground for the creativity of manipulation of these interactions, it be- supramolecular architecture, which posi- scientists from all origins. The breadth and came progressively the chemistry of mo- tions the components, followed by post- depth of its scope is evidenced and illus- lecular information, involving the storage assembly modification through covalent trated by the wide selection of many of the of information at the molecular level, in bond formation. Both areas will continue major players in the field gathered in the the structural features, and its retrieval, Special Feature in this issue of PNAS. transfer, and processing at the supramo- Rather than adding another facet to this lecular level, by interactional algorithms Abbreviations: CDC, constitutional dynamic chemistry; already breathtaking panorama, it appeared operating through molecular recognition DCC, dynamic combinatorial chemistry. appropriate here to emphasize perspectives events based on well-defined interaction *E-mail: [email protected]. www.pnas.org͞cgi͞doi͞10.1073͞pnas.072065599 PNAS ͉ April 16, 2002 ͉ vol. 99 ͉ no. 8 ͉ 4763–4768 Downloaded by guest on September 25, 2021 to provide in the future a range of highly tions (such as secondary metal coordina- information and may display kinetic con- sophisticated noncovalent as well as cova- tion, van der Waals stacking, etc.) or trol, generating kinetic products before lent entities. A particularly impressive il- toward modifications of parameters (such reaching the thermodynamic one(s). This lustration of the latter is the synthesis of as concentrations and stoichiometries of is the case in the initial assembly of a triple interlocked compounds (see below). the components, presence of foreign spe- helical complex that evolves toward a cir- Beyond preorganization lies the design cies, etc.). When the assembly occurs only cular helicate (20). Such a process may of systems undergoing self-organization, in a narrow range of conditions, the system either be sequential, if the kinetic product i.e., systems capable of spontaneously gen- is unstable and presents a singularity; it is an intermediate located on the pathway erating well-defined, organized, and func- may also display a bifurcation or a switch- toward the final product, or it may be tional supramolecular architectures by ing point between different assemblies. bifurcated, if this is not so. self-assembly from their components, thus On the other hand, sensitivity to pertur- A sequential process may be either behaving as programmed systems (1, 10). bations, while limiting the operation commutative, if given steps may be inter- Chemical programming requires the in- range, introduces diversity and adaptabil- changed along the overall pathway leading corporation into molecular components ity (3) in the self-organization process. to the final superstructure, or it may of suitable instructions for generation of a Self-selection with self-recognition oc- be noncommutative if its progressive well-defined supramolecular entity. The curs when the structural instructions are build-up occurs through a defined se- program is molecular, the information sufficiently strong, as is the case in the quence of molecular instructions and al- being contained in the covalent structural ‘‘correct’’ pairing of strands of different gorithms, where the generation of a given framework; its operation is supramolecu- lengths in the assembly of helicates, inor- intermediate depends on the previous one lar, making use of recognition algorithms ganic double helices (11). The process and sets the stage for the next one. For based on specific interaction patterns. Un- bears relation to the implementation of example, discotic liquid crystals form by derstanding, inducing, and directing self- combinatorial chemistry in its ‘‘dynamic’’ the assembly of ‘‘sector’’-shaped compo- processes is key to unraveling the progres- version (see below). It reveals a broader nents into disks, which thereafter organize sive emergence of complex matter.