Impact of a Carboxyl Group on a Cyclometalated Ligand: Hydrogen-Bond- and Coordination-Driven Self-Assembly of a Luminescent Platinum(II) Complex

A new luminescent cyclometalated platinum­(II) complex containing a carboxyl group, trans-[Pt­(pcppy)­(pic)]­[1-COOH; Hpcppy = 2-(p-carboxyphenyl)­pyridine and Hpic = picolinic acid] has been synthesized and characterized. The luminescence behavior of 1-COOH in the solid and solution states is completely different despite the similarity of the luminescence in both states for the nonsubstituted complex, [Pt­(ppy)­(pic)] (1-H; Hppy = 2-phenylpyridine). Interestingly, 1-COOH exhibits concentration-dependent absorption and emission behavior based on its aggregation in a basic aqueous solution despite the absence of amphiphilic character.