Polarized luminescence spectra of single crystal W (CO )5-X (with X = pyridine, 4-methylpyridine, 4-t-butylpyridine, 3,4-dimethylpyridine, 4-am inopyridine, 3-acetylpyridine, 3,5-dibromopyridine, 3-benzoylpyridine, 4-formylpyridine) at low temperatures (1.9 K≦ T ≦ 80 K) are reported. Depending on the nature of the pyridine substituent the emitting state is either a ligand field (LF) state or a metal to ligand charge transfer (CT) state. This results in drastic differences in both bandshape and temperature behaviour of the luminescence spectra. The CT-luminescence is structureless and is not influenced by temperature variation, whereas the LF-lum inescence spectra exhibit in most cases a distinct vibrational fine structure at low temperatures and show a remarkable temperature dependence. The emission spectra of single crystal W (CO )5-3,4-dim ethylpyridine and W (CO )5-pyridine can be strongly influenced by magnetic fields (H ≦ 6 T). The results are explained within a model assuming molecular C4v symmetry and regarding spin orbit coupling.