Synthesis, Structure, and Photophysical Properties of Blue‐Emitting Zinc(II) Complexes with 3‐Aryl‐Substituted 1‐Pyridylimidazo[1,5‐<i>a</i>]pyridine Ligands

<jats:title>Abstract</jats:title><jats:p>Six zinc(II) complexes of the general formula [Zn(L<jats:sup>R</jats:sup>)X<jats:sub>2</jats:sub>] (<jats:bold>1</jats:bold>: R = Me, X = Cl; <jats:bold>2</jats:bold>: R = Me, X = Br; <jats:bold>3</jats:bold>: R = Me, X = I; <jats:bold>4</jats:bold>: R = OH, X = Cl; <jats:bold>5</jats:bold>: R = OH, X = Br; <jats:bold>6</jats:bold>: R = OH, X = I), in which L<jats:sup>R</jats:sup> is 1‐(pyridin‐2‐yl)‐3‐<jats:italic>o</jats:italic>‐tolylimidazo[1,5‐<jats:italic>a</jats:italic>]pyridine (L<jats:sup>Me</jats:sup>) or 2‐[1‐(pyridin‐2‐yl)imidazo[1,5‐<jats:italic>a</jats:italic>]pyridin‐3‐yl]phenol (L<jats:sup>OH</jats:sup>), have been prepared and characterized. The X‐ray structural analysis performed on complexes <jats:bold>1</jats:bold>, <jats:bold>3</jats:bold>, and <jats:bold>4</jats:bold> showed that both L<jats:sup>Me</jats:sup> and L<jats:sup>OH</jats:sup> act as <jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐bidentate ligands and coordinate to the Zn<jats:sup>II</jats:sup> metal center through the pyridine ring (N<jats:sub>py</jats:sub>) and the pyridine‐like nitrogen atom of the imidazo[1,5‐<jats:italic>a</jats:italic>]pyridine group (N<jats:sub>im</jats:sub>). The photophysical properties of these compounds have been investigated, both in solution and in the solid state. The complexes showed intense blue luminescence when excited with UV light (<jats:italic>λ</jats:italic><jats:sub>exc</jats:sub> = 366–410 nm) with <jats:italic>λ</jats:italic><jats:sub>max</jats:sub> of emission between 440–460 nm in the solid state. Complexes <jats:bold>1</jats:bold>–<jats:bold>3</jats:bold> showed moderate‐to‐good absolute photoluminescence quantum yields (PLQYs) in the solid state with a maximum PLQY of 0.40 for <jats:bold>1</jats:bold>. These values were slightly lower than the PLQY of free L<jats:sup>Me</jats:sup> (0.60). On the other hand, the PLQY of L<jats:sup>OH</jats:sup> increased after coordination to ZnCl<jats:sub>2</jats:sub>, and a PLQY of 0.29 was recorded for <jats:bold>4</jats:bold>. A possible interpretation of this behavior is reported.</jats:p>