紫外-可见光谱法研究超支化分子与Cr^(3+)配位行为

Coordination behavior between hyper-branched molecule and Cr^(3+) with UV-visible spectrum method

采用熔融缩聚法一步合成了端羧基超支化聚酯(HBP-1)和端羧基超支化聚酰胺(HBP-2)2种水性端羧基超支化分子,利用红外线照射(IR)、核磁共振(~1H NMR)对产物的结构进行了表征。同时采用了紫外-可见光谱法研究了超支化分子与Cr^(3+)的配位行为,根据特征吸收峰的位置变化、吸收峰的强弱及2特征吸收峰的摩尔系数之比R值,判定超支化分子配体与Cr^(3+)配位能力的强弱情况。结果表明:引入超支化结构能够提高分子与铬的配位能力,且由于N原子电负性小于O原子,比O原子更容易提供孤对电子,d轨道分裂能大,配体场强强,因而端羧基超支化聚酰胺比超支化聚酯与铬的配位能力强,这一研究结果为后期设计合成超支化铬鞣助剂,提供了理论依据和技术支撑。

Two kinds of waterborne carboxyl-terminated hyper-branched molecule of polyester （ HBP- 1 ） and polyamide（HBP-2） were synthesized through one-step by melt phase polycondensation. Molecule structures were characterized by Infrared radiation （ IR）, 1H nuclear magnetic resonance （1HNMR）. Coordination behavior between hyper -branched molecules and Cr3＋was studied by Ultraviolet-visible （UV-visible） spectrum method. The coordination ability of hyper-branched molecules and Cr3＋ was assessed according to location changing and values of characteristic absorption peaks and molar ratios of the two absorption peaks （ R ）. Results show that the introducing of hyperbranched structure can improve the coordination ability of hyper-branched molecules with Cr3＋. The coordination ability of carboxyl-terminated hyper-branched polyamide is better than that of the polyester owing to lower electronegativity of N atom than O atom, that is N can provide lone electron pair easier than O atom, it has better splitting enegy of d-orbtital and stronger field intensity of ligand. These conclusions build theoretical foundation and technical support for the further synthesis of hyper-branched chrome tanning auxiliaries.