The title compound (H3tpda)2[CdCl4] (H2tpda = 2,6-bis(2-pyridylamino)pyridi-ne) was synthesized by the reaction of CdCl2 with H2tpda in methanol under acidic condition. Single- crystal X-ray analysis reveals that the compound crystallizes in monoclinic, space group P21/n with a = 13.377(3), b = 16.978(3), c = 14.328(3) ?, β = 94.75(3)°, V = 3243.1(11) ?3, Z = 4, Dc = 1.603 g/cm3, μ = 1.042 mm–1, F(000) = 1576, C30H28CdCl4N10, Mr = 782.82, T = 291(2) K, R = 0.0433 and wR = 0.0848 for observed 4554 reflections with I > 2σ(I). The cadmium(II) atom in the complex anion is tetrahedrally coordinated by four chlorine atoms, whereas, in each [H3tpda]+ cation, one pyridyl nitrogen is protonated. A 3D network is formed by multiple intermolecular hydrogen bonds between the cations and anions as well as π-π interactions among the pyridyl rings.
Granule chitosan was prepared from chitosan,chemically-modified, then used as carrier and covalently linked with polyphenol oxidase(PPO) from tobacco by using glutaraldehyde as cross-linking agent.The desirable granule chitosan could be obtained when the molecular mass of chitosan was about 250000 and its concentration was about 30%.The absorbing ability and the category, distribution and number of active groups on the surface of granule chitosan were all improved by formol titration under weak basic condition after protecting parts of free amino-groups with Cu 2+ .The optimal conditions for immobilization of PPO were as follows: the ratio of PPO to granule chitosan: 0.8∶100(mass);concentration of glutaraldehyde:0.6%; immobilization time: 80 min.The resulting immobilized PPO had specific activity of 73 U·g -1 , and activity retention value of 83.2% was achieved.The K m value of immobilized PPO was 4.67 mmol·L -1 and that of soluble PPO was 1.26 mmol·L -1 .The optimal pH values were 6.0 for soluble PPO and 7.0 for immobilized PPO; the optimal temperature were 40 ℃ for soluble PPO and about 50 ℃ for immobilized PPO.In addition, stability of immobilized PPO to temperature and pH was obviously increased.
