Incorporation of a Fluorine Atom in a Bridging Ligand of Half-Lantern PtII2 Complexes Provides Up to 10-Fold Enhancement of Electroluminescence Brightness

The binuclear half-lantern platinum(II) complexes [Pt(pbt)(μ-S∧N)]2 (pbtH = 2-phenylbenzothiazole, S∧N = benzo[d]thiazole-2-thiolate Pt1, 6-fluorobenzo[d]thiazole-2-thiolate Pt2, 6-chlorobenzo[d]thiazole-2-thiolate Pt3, 6-bromobenzo[d]thiazole-2-thiolate Pt4, and 6-iodobenzo[d]thiazole-2-thiolate Pt5) were synthesized by the treatment of the in situ formed [Pt(pbt)(NCMe)2]NO3 complex and appropriate benzo[d]thiazole-2-thiole in the presence of tBuOK; yield: 51-84%. Complexes Pt1-5 exhibit intense red photoluminescence originated from 3MMLCT state reaching 22% room temperature quantum yields in a CH2Cl2 solution. All complexes display excited-state decay kinetics both in solution and in the solid state; the kinetics was adequately modeled by single exponentials. The complexes display more than 10-fold higher electroluminescence brightness for the F-containing Pt2 (900 cd/m2) and 2-fold higher electroluminescence brightness for the Cl-containing Pt3 (143 cd/m2) compared to the H-substituted complex Pt1 (77 cd/m2). It is argued that this impressive device luminance growth, occurred on formal replacement of H-to-F, is associated with the intermolecular strong hydrogen bonding H···F relevant to the H-bond found in the structure of Pt2.