Physics and Chemistry of Molecule-Based Strongly Isotropic Lattices: Hidden Frustrations, Flat Bands, Chirality, and Electrochemical Control

Strongly isotropic lattices are geometrically constrained networks in which all bonds connected to a common vertex are topologically equivalent. Only the honeycomb, diamond, and K4 lattices satisfy this condition, giving rise to characteristic electronic structures such as Dirac cones and Dirac nodal lines. In this Award Account, we describe our efforts to construct molecule-based strongly isotropic lattices and to explore emergent phenomena arising from the interplay of topology and molecular degrees of freedom. Strong isotropy provides a common origin for hidden frustrations: line-graph transformations generate kagome and hyper-kagome spin networks with quantum-spin-liquid-like behavior, while a molecule-based diamond network exhibits bond frustration associated with a structural phase transition. Strongly isotropic molecular lattices also provide a route to flat-band engineering, where Dirac dispersions are dictated by lattice topology and flat bands by molecular-orbital symmetry. We further demonstrate chirality-related phenomena, including enhanced circularly polarized luminescence in a chiral K4 framework and spontaneous formation of chiral honeycomb monolayers from an achiral molecule. Finally, solid-state electrochemistry enables active control of electronic states, establishing strong isotropy as a versatile design principle for molecule-based materials with emergent magnetic, electronic, chiral, and electrochemical functionalities.