A mononuclear Cu complex Cu_0.5(4,4'?bipy)(H₂O)·L·0.5(4,4'?bipy)·2H₂O (1) was obtained by hydrothermal reaction with Cu²⁺ as the central ion and 4,4'?bipy as the nitrogen?containing auxiliary ligand. Its structure and composition were characterized by modern characterization methods, such as X?ray single crystal diffraction, elemental analysis and infrared spectrum. The results show that Cu²⁺ is six coordinated with four nitrogen atoms of 4,4'?bipy molecules and two oxygen atoms of H₂O molecules, showing a distorted octahedral coordination configuration. L^2- anion only balances the positive charges in compound 1 and does not participate in the coordination of metal Cu²⁺. Cu²⁺ coordinates with 4,4'?bipy and H₂O molecules to form a lattice layered structure [Cu(4,4'?bipy)₂(H₂O)₂]²⁺, the hydroxyl group of L^2- anion and free H₂O molecules form hydrogen bonds with H₂O molecules in the layered structure respectively, which increases the thermal stability of H₂O molecules in compound 1. The fluorescence emission of compound 1 is at 409 nm, which can be attributed to the intraligand emission state. Compared with the ligand, there is a slight red shift, which may be caused by the coordination between 4,4'? bipy ligand and Cu²⁺.

Using sodium 1,4?dihydroxybenzene?2?sulfonate sodium (NaH₂L), 4,4'?bipyridine (bipy), Co(NO₃)₂·6H₂O and NiSO₄·6H₂O as raw materials, two mononuclear complexes containing nitrogen?donor ligands with similar structures, M(bipy)(H₂O)₄·(2H₂L)·4H₂O（M=Co（1）， Ni（2））, were synthesized by heating reflux method. The molecular structurse and composition were determined by single crystal X?ray diffraction, elemental analyses and thermogravimetric analyses. Co²⁺ and Ni²⁺ are six?coordinated, showing octahedral configuration, which are binded with one bipy molecule and four water molecules. H₂L^- anion does not coordinate with metal ions, balancing charges. In the complexes, H₂L^- anions, free water molecules and [M(bipy)(H₂O)₄]²⁺ cations can generate hydrogen bonds, which can form a network structure and increase the stability of the complexes. The fluorescence studies indicate that the maximum emission peaks of complexes 1 and 2 were 380 nm and 390 nm, respectively, which are characteristic fluorescence emission peaks of NaH₂L. The red shifts of the fluorescence emission peaks were due to the charge transfers between metal and ligand.