RESEARCH / SUGA GROUP
What properties might lie hidden in molecules that have not yet been made? And what characteristics and advantages do familiar molecules have compared with other molecules that could exist?
By exploring a wide range of molecular structures and properties, we identify molecules with new properties and functions while reassessing familiar molecules within a broader chemical space. Discovering unknown molecules and understanding known ones are complementary ways to investigate the relationship between structure, properties, and function.
Beyond the reach of intuition.
Molecular exploration depends not only on how candidates are selected, but also on which molecules can be explored. We design molecular representations and structural transformation rules to construct networks in which transformations connect molecules. Which molecules can we move from, and which can we reach? By building these connections, we expand the chemical space available for exploration. We pursue the development of this exploration framework together with the discovery of molecules with new properties and functions within it.
We developed CARBOT, a molecular generation method that constructs a chemical space of π-conjugated hydrocarbons through structural transformations. Building on this work, we will extend molecular representations and transformation rules to broaden the diversity of structures available for exploration.
The transformations we allow and the connections we establish between molecules affect both which molecules can be reached and how exploration proceeds. We study the design of these connections to develop ways of reaching molecules that human intuition alone would not readily suggest. To explore the chemical spaces we construct, we will also use established approaches such as Bayesian optimization, Monte Carlo search, and genetic algorithms.
We use quantum chemical calculations to investigate optical, electronic, and spin-related properties of π-conjugated organic molecules, including excited-state behavior. By comparing molecular structures and properties within the chemical spaces we construct, we search for molecules with desired properties.
We also focus on how much properties change as a result of structural transformations. We develop machine-learning frameworks to predict these differences—how a particular transformation changes the properties of a given molecule—and apply them to molecular exploration.
We evaluate candidates in terms of the desired properties, molecular stability, and structural simplicity. By comparing known molecules and unexplored candidates using the same criteria, we reconsider the strengths and limitations of familiar molecules while searching for new alternatives.
Bringing molecular outliers to life.
We compare the structures and properties of diverse π-conjugated molecules to find those with distinctive properties that depart from the trends expected from their structures. Outliers in property distributions and correlations guide us toward the molecular frameworks that give rise to these properties.
We synthesize candidate molecules and measure their properties, both to verify their behavior and to understand the structural origins of their distinctive responses. Through exploration guided by molecular properties and experimental investigation, we aim to discover molecular frameworks that enable new functions.
Shaping new responses, inside and out.
How do shape and internal structure influence the mechanical properties of polymer materials? We focus on macroscopic shapes produced by 3D printing and nanoscale internal structures formed through polymerization-induced microphase separation (PIMS).
We control these structures individually and investigate experimentally how they relate to deformation and force transmission. By combining the design of external shape and internal structure, we aim to create polymer materials with new mechanical responses.
Future directions include lattice structures whose responses depend on the direction of applied force, as well as metamaterials whose distinctive mechanical properties arise from structural design.
We use quantum chemical calculations to evaluate molecular aromaticity in both ground and excited states. By examining how aromaticity changes with electronic state and molecular structure, we investigate the origins of distinctive properties and functions.
We also collaborate on aromaticity analysis to understand experimentally observed properties and phenomena in terms of molecular electronic states.
We investigate how molecules deform under force and how these changes affect fluorescence and other optical responses. By clarifying the relationship between molecular structure and response, we seek to understand how molecular responses can reveal the forces acting on them.
We can also explore collaborations that incorporate force-responsive molecules into polymer materials and investigate their responses during stretching. By relating material deformation to molecular responses, we examine how force is transmitted within the material.
COLLABORATION
“If only a molecule had these properties.” We turn such questions into concrete molecular exploration. Combining collaborators’ expertise with our exploration framework, we search for new molecular candidates while considering the target properties and synthetic feasibility.
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