The Aggregations and Strong Emissions of d⁸ and d¹⁰ Metal−8-Hydroxyquinaldine Complexes

Five new d⁸ and d¹⁰ metal complexes, Pd(8-hq)₂ (1), [Ag(8-Hhq)₂]NO₃ (2), Ag(8-hq)(8-Hhq) (3), [(8-H₂hq)₂PdCl₄]·2H₂O (4), and Pt(8-hq)(tht)Cl (5) (tht = tetrahydrothiophene), all with a fluorogenic chelating agent, 8-hydroxyquinaldine (8-Hhq), have been synthesized and characterized. The aggregations of their photoactive metal centers through π−π stacking and hydrogen bonding interactions construct the interesting frameworks. The strong emissions of 1−3 and 5 in solid states with orange, cyan, and green luminescences originating from metal···metal and π−π interactions are assigned as metal to ligand charge transfer/metal–metal to ligand charge transfer/intraligand emissions. The solvent effects on their photophysical properties are examined, which exhibit a wide range of strong luminescences in the different organic solvents. In addition, time-dependent density functional theory calculations using the B3LYP functional on 1 are in good agreement with the experiments. Thermogravimetric analyses and UV/vis spectra with composition of certain simulated results are also reported.