Synthesis and Characterization of Zinc Complexes with Diethyl 2‑Hydroxyazulene-1,3-dicarboxylate as a Ligand.

The reaction of diethyl 2-hydroxyazulene-1,3-dicarboxylate (DEHA) with zinc species (Zn-(OAc)2 and ZnCl2) in the presence of various alkali metal carbonates (M2CO3) was investigated. The resulting complexes were characterized by nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis, mass spectrometry, single-crystal X-ray structural analysis, and UV-vis and fluorescence spectroscopy. The reaction between DEHA and Zn-(OAc)2 in the presence of Rb2CO3 or K2CO3 as bases afforded Zn-DEHA-Rb or Zn-DEHA-K, respectively, where three DEHA anions were coordinated to Zn2+, with an alkali metal ion as the counter cation. On the other hand, the reaction between DEHA and Zn-(OAc)2 in the presence of Na2CO3 afforded Zn-DEHA-Na-1, in which four DEHA anions were coordinated to two Zn2+ and Na+, with two acetoxy ions present. The reaction between DEHA and ZnCl2 in the presence of Na2CO3 provided Zn-DEHA-Na-2, where three DEHA anions were coordinated to Zn2+, with Na+ as the countercation. The zinc complexes exhibited S1 emission despite differences in their structures. Furthermore, the synthesized complexes were mixed with poly-(methyl methacrylate) to form composite films.