  To enrich and enhance the diversity of the \textsc{quest} database of
highly-accurate excitation energies
[\href{https://doi.org/10.1002/wcms.1517}{V\'eril \textit{et al.},
\textit{WIREs Comput.~Mol.~Sci.}~\textbf{11}, e1517 (2021)}], we report
vertical transition energies in transition metal compounds. Eleven diatomic
molecules with singlet or doublet ground state containing a fourth-row
transition metal (\ce{CuCl}, \ce{CuF}, \ce{CuH}, \ce{ScF}, \ce{ScH}, \ce{ScO},
\ce{ScS}, \ce{TiN}, \ce{ZnH}, \ce{ZnO}, and \ce{ZnS}) are considered and the
corresponding excitation energies are computed using high-level coupled-cluster
(CC) methods, namely CC3, CCSDT, CC4, and CCSDTQ, as well as
multiconfigurational methods such as CASPT2 and NEVPT2. In some cases, to
provide more comprehensive benchmark data, we also provide full configuration
interaction estimates computed with the \textit{"Configuration Interaction
using a Perturbative Selection made Iteratively"} (CIPSI) method. Based on
these calculations, theoretical best estimates of the transition energies are
established in both the aug-cc-pVDZ and aug-cc-pVTZ basis sets. This allows us
to accurately assess the performance of CC and multiconfigurational methods for
this specific set of challenging transitions. Furthermore, comparisons with
experimental data and previous theoretical results are also reported.
