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

Molecular assembly has emerged as an alternative platform for superlattice engineering via heterointegration compared to traditional vdW moire engineering. The electronic properties of the self-assembled square lattice monolayer of metal-free naphthalocyanine (H₂Nc), including its density of states, band dispersion, and tunability by metal substrates, remain incompletely characterized. Using density functional theory, supported by ARPES and STM, we compare the electronic structure of a free-standing H₂Nc monolayer with that of an H₂Nc lattice assembled on a noble metal. In the freestanding film we identify nearly flat, molecule-localized states and more dispersive bands, each of which can be compactly described by an anisotropic tight-binding Hamiltonian that yields band-resolved hopping anisotropies. Adsorption on Ag(100) induces 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 show 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.