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Three new coordination compounds containing 5‑diethylamino‑2‑((4‑(phenyldiazenyl) phenylimino) methyl) phenol ligand have been synthesized and fully characterized. Single crystal structure showed that the ligand shows multiple coordination mode and the phenyl group next to azo group could rotate during the coordination process. In Mn(HDAPPP)2Cl2·CH3CN (1), the HDAPPP behaved as a mono ligand because of the N of the imine group is protonated in the keto form and does not participate in coordination. While the Cu(DAPPP)2 (2) and Ni(DAPPP)2 (3) are classic complexes containing azo-Schiff base ligand. The fluorescence emission peaks of compounds indicated that the fluorescence of the compounds are mainly derived from the π-π* charge transition of the ligand and affected by the rotation of ligand. The UV–Vis data revealed that the compound 1–3 with the maximum absorption peak at 425 nm, 440 nm and 338 nm, respectively. This clearly confirmed that the compound 1 is mainly based on the keto configuration while the compound 3 is mainly based on the enol configuration. Z-scan experiments showed that all compounds exhibited reverse saturable absorption effect and self-defocusing effect for nonlinear optical materials. The nonlinear absorption coefficients (β) of compound 1–3 are evaluated to be 6 × 10−11 m·W−1, 4.4 × 10−11 m·W−1, and 1.7 × 10−11 m·W−1 respectively, and the nonlinear refraction coefficients (n2) are −1.4 × 10−17 m2·W−1, −1.6 × 10−17 m2·W−1, −7.0 × 10−18 m2·W−1 respectively. The nonlinear optical property of compound 1 and 2 are better than compound 3, which are influenced by ligand rotation after coordination.

The diethylphosphonate ligand HL 1 substituted pyridylpyrrole was synthesized by treatment of 2-bromo-6-(1H'-pyrrol-2-yl)pyridine and diethylphosphite in presence of base triethylamine and catalyst Pd(PPh 3 ) 4 under refluxing toluene conditions. The HL 1 ligand was treated with bromotrimethylsilane and followed hydrolysis by methanol to afford diphosphonic acid ligand H 3 L 2 . Treatment of H 3 L 2 with [Ru(NO)Cl 3 ] in presence of triethylamine in refluxing thf was generated diruthenium nitrosyl complex [Ru(L 2 )(NO)(Cl)] 2 ·(Et 3 NH) 2 ([ 1 ]·(Et 3 NH) 2 ), which is water soluble. The ligands and metal complex were fully characterized by NMR, IR, ESI-MS and single crystal X-ray diffraction technology. The solid state structure analysis displays 1 2- is dinuclear species, of which two ruthenium atoms are linked by two PO 3 2- groups. Photorelease of nitric oxide from 1 2- was monitored by UV-Vis spectra and the amount of the NO was determined by Griess reaction and DPPH radical scavenging reaction.