Self-Assembled H2NC Molecular Lattices as a Platform for Substrate-Tunable Quantum Superlattices

Compared to van der Waals moir\'e systems, molecular assembly has emerged as an exciting alternative platform for superlattice engineering via heterointegration. The electronic properties of the self-assembled square lattice monolayer molecular crystal of metal-free naphthalocyanine (H2Nc), in particular the electronic band dispersion and their tunability by metal substrates, remain less explored. Using density functional theory, supported by angle-resolved photoemission and scanning tunneling microscopy, we compare the electronic structure of a free-standing H2Nc monolayer with that of H2Nc lattice assembled on noble metal substrates. In the freestanding film, we identify both nearly flat, molecule-localized states and more dispersive bands, and we show that each can be compactly described by an anisotropic tight-binding Hamiltonian that yields band-resolved hopping anisotropies. We further reveal wide tunability in the Coulomb interaction and inter-site hopping based on different molecular orbitals. Adsorption on Ag(100) drives strong orbital hybridization, charge transfer, and C2 symmetry breaking, producing partially filled, substrate-mediated dispersive states that metallize the molecular lattice. Orbital analysis identifies C2-even and C2-odd components and maps the spatial pattern of charge redistribution tied to symmetry breaking. Complementary ARPES on H2Nc/Au(111) qualitatively corroborates the predicted dispersion and partial filling. These results clarify how metal substrates convert H2Nc from isolated molecules into a tunable 2D lattice and highlight molecular superlattices as a versatile platform to simulate anisotropic lattice models.