Single quantum emitters play a fundamental role in the development of quantum
technologies such as quantum repeaters, and quantum information processing.
Isolating individual molecules with stable optical emission is an essential
step for these applications, specially for those molecules that present large
coherence times at room temperature. Among them, vanadium-oxide phthalocyanine
(VOPc) molecules stand out as promising candidates due to their large coherence
times measured in ensemble. However, the optical properties of individual
molecules have not yet been reported. Here we show that single VOPc molecules
with stable optical properties at room temperature can be isolated. We find
that the optical response of the molecule under laser illumination of different
polarization agrees well with a system having pyramidal C4v symmetry.
Furthermore, the molecule reveals a non-radiative transition rate that depends
on the excitation wavelength when its lifetime is interrogated. We provide
theoretical calculations that support our experimental findings and provide
insight to the role of phonons and internal electronic structure of the
molecule. These results demonstrate that this single paramagnetic molecule can
function as a single quantum emitter while displaying optical stability under
ambient conditions to have their intrinsic properties investigated