Solid-state emission enhancement in vaulted trans-bis(salicylaldiminato)platinum(II) crystals with halogen functionality.

The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(ii) complexes 1-3 with halogen functionalities are described and compared with the non-substituted analogues. Chloro-substitution provided an improvement of the low emission properties of short-vaulted, non-substituted complexes 1 and 2 in the crystalline state at ambient temperature, while the intense emission of long-vaulted analogues 3 remained unchanged. Bromo-substituted crystals also emit intensively, while the fluoro analogue is non-emissive under the same conditions. Temperature-dependent emission spectra indicate that all chloro- and bromo-substituted crystals with enhanced emission properties at ambient temperature exhibit improved heat resistance properties towards emission decay with the halogen functionalities. X-ray diffraction studies revealed that such a positive effect of halogenation for the enhancement of solid-state emission is due to significant molecular constraints in the crystals by a combination of the vaulted structure and three-dimensional HX hydrogen bonding interactions.