Phosphorescent platinum(ii) alkynyls end-capped with benzothiazole units.

Symmetric trans-bis(alkynyl)bis(phosphine) Pt complexes based on the 2-phenylbenzothiazole (pbt) unit [trans-Pt(C[triple bond, length as m-dash]C-pbt)L] [L = PPh1, PEt2, 1,3,5-triaza-7-phosphaadamantane (PTA) 3] and the mixed alkynyl-cyanide anionic complex (NBu)[trans-Pt(C[triple bond, length as m-dash]C-pbt)(CN)] (4) were synthesized. The complexes have been fully characterized including X-ray crystallography for 2 and 4. All complexes display long-lived emission with moderate quantum yields (ϕ 6.8-22.6%) in doped PMMA films at 298 K and complex 4 is also emissive in DMSO fluid and in rigid media (solid, glass at 77 K). Complex 4 displays a negative solvatochromic behavior. Absorption and emission energies have been analyzed by means of linear solvation energy based on Kamlet-Taft solvatochromism parameters and the Gutmann's acceptor numbers. The study indicates that solvatochromism is due to the contribution of solvent-to-cyanide hydrogen bonding and increased solvent dipolarity-polarizability. TD and TD-DFT calculations were performed on the ground and excited states of two different conformers of 2 and 4 to provide insight into the structural, electronic and optical properties of these systems.