Luminescence spectra of isoelectronic square-planar d complexes with 3d, 4d, and 5d metal centers show d-d luminescence with an energetic order different from that of the spectrochemical series, indicating that additional structural effects, such as different ligand-metal-ligand angles, are important factors. Variable-pressure luminescence spectra of square-planar nickel(II), palladium(II), and platinum(II) complexes with dimethyldithiocarbamate ({CH}DTC) ligands and their deuterated analogues show unexpected variations of the shifts of their maxima. High-resolution crystal structures and crystal structures at variable pressure for [Pt{(CH)DTC}] indicate that intermolecular M···H-C interactions are at the origin of these different shifts.

We present the variable-pressure d-d luminescence spectra of crystalline bis-dimethyldithiocarbamate palladium(ii) and its deuterated analog. The energies and shifts of the band maxima provide evidence for intermolecular PdH-C interactions, with quantitative differences observed for the deuterated complex. Shifts show distinct interactions in three pressure ranges between 1 bar and 85 kbar.