  Two-dimensional materials can be crafted with structural precision
approaching the atomic scale, enabling quantum defects-by-design. These defects
are frequently described as artificial atoms and are emerging
optically-addressable spin qubits. However, interactions and coupling of such
artificial atoms with each other, in the presence of the lattice, is remarkably
underexplored. Here we present the formation of artificial molecules in solids,
introducing a new degree of freedom in control of quantum optoelectronic
materials. Specifically, in monolayer hexagonal boron nitride as our model
system, we observe configuration- and distance-dependent dissociation curves
and hybridization of defect orbitals within the bandgap into bonding and
antibonding orbitals, with splitting energies ranging from $\sim$ 10 meV to
nearly 1 eV. We calculate the energetics of $cis$ and $trans$ out-of-plane
defect pairs CH$_\textrm{B}$-CH$_\textrm{B}$ against an in-plane defect pair
C$_\textrm{B}$-C$_\textrm{B}$ and find that in-plane defect pair interacts more
strongly than out-of-plane pairs. We demonstrate an application of this
chemical degree of freedom by varying the distance between C$_\textrm{B}$ and
V$_\textrm{N}$ of C$_\textrm{B}$V$_\textrm{N}$ and observe changes in the
predicted peak absorption wavelength from the visible to the near-infrared
spectral band. We envision leveraging this chemical degree of freedom of defect
complexes to precisely control and tune defect properties towards engineering
robust quantum memories and quantum emitters for quantum information science.
