  We present the results of first-principle calculations using the Vienna
Ab-initio Simulation Package (VASP) for a new class of organometallics labeled
TM3C6O6 (TM =Sc, Ti, V, Cr, Fe, Co, Ni and Cu) in the form of planar,
two-dimensional, periodic free-standing layers. These materials, which can be
produced by on-surface coordination on metallic surfaces, have a kagome lattice
of TM ions. Calculating the structural properties, we show that all considered
materials have local magnetic moments in the ground state, but four of them
(with Fe, Co, Ni and Cu) show spin-crossover behavior by changing the lattice
constant, which could be valuable for possible epitaxy routes on various
substrates. Surprisingly, we find a very large richness of electronic and
magnetic properties, qualifying these materials as highly promising
metal-organic topological quantum materials. We find semi-conductors with
nearest-neighbor ferromagnetic (FM) or antiferromagnetic (AFM) couplings for V,
and Sc and Cr, respectively, being of potential interest to study spin ice or
spin liquids on the 2D kagome lattice. Other TM ion systems combine AFM
couplings with metallic behavior (Ti, Fe and Ni) or are ferromagnetic kagome
metals like Cu3C6O6 with symmetry protected Weyl crossings at the Fermi
surface. For the latter compound, the spin orbit coupling is shown to be
responsible for small gaps which should allow the observation of the quantum
anomalous Hall effect (QAHE).
