In-Situ Measurements and Molecular Orientation by External Reflection Spectrometry of Liquid-Liquid Interfacial Adsorbates of Porphyrins.

采用部分反射光谱法，研究了质子化形式的亲脂卟啉（H_2P）在惰性有机溶剂/水无机酸（HX）溶液界面上的吸附状态，包括外反射（ER）和部分内反射（PIR）。用一个由液池和棱镜组成的简单装置，对聚集体（H_4PX_2）_<n,i>中的质子化四苯基卟啉进行了化学计量分析。(1)在甲苯- 4mh_2so_4体系中，ER光谱法可有效区分有机相（H_2P）_o中的界面吸附物和亲脂溶质。(2)在十二烷- 4mh_2so_4体系中，所有（H_2P）_o都被质子化生成（H_4PX_2）_<n,i>和水相H_4P^<2+>_<aq>。各波段反射吸光度与界面分子密度[H_4PX_2]_i的关系表明，界面吸附状态由单层转变为具有不同反射系数的多层吸附状态。(3)十二烷-4 M H_2SO_4体系饱和界面分子密度为1.20×10^<-10> mol cm^<-2>；它使吡咯环面与界面法线的倾斜角为47°。中间苯基邻位取代基的亲脂性四苯基卟啉衍生物无聚集现象。而质子化的四对苯基卟啉则能缔合形成聚集体。这些结果表明，苯基的分子结合依赖于苯基的旋转性质，从而产生平面型分子结构。利用自制的变角装置，研究了反射光谱与入射角的关系。在p极化PIR光谱中观察到正负带，其带位与p极化ER光谱中的带位相对应。然而，p-PIR谱带与p-ER谱带呈现相反的符号。这说明p-PIR光谱的界面选择规律具有p-ER的反转规律，PIR也可用于分子取向的分析。少

The authors investigated the interfacial adsorption states of lipophilic-porphyrins (H_2P) in a protonated form (H_4PX_2) at the inert organic solvent/aqueous inorganic acid (HX) solution interface by development of in situ measurement devices for partial reflection spectrometry, including external reflection (ER) and partial internal reflection (PIR).1.Stoichiometric analysis of protonated tetraphenylporphyrin in an aggregate (H_4PX_2)_<n,i> was accomplished using a simple device comprising a liquid cell and prisms. (1)In the toluene-4 M H_2SO_4 system, ER spectrometry was effective to distinguish interfacial adsorbates from lipophilic solute in the organic phase (H_2P)_o. (2)In the dodecane-4 M H_2SO_4 system, all (H_2P)_o was protonated to yield (H_4PX_2)_<n,i> and aqueous species, H_4P^<2+>_<aq>. The relationship of reflection absorbance at each of bands for interfacial molecular density [H_4PX_2]_i suggested that the interfacial adsorption state changed from a monolayer form to a … More multilayer one with a different reflection coefficient. (3)The saturated interfacial molecular density in the dodecane-4 M H_2SO_4 system was estimated to be 1.20×10^<-10> mol cm^<-2> ; it yields a tilt angle 47°of pyrrole ring plane against the interface normal.2.No aggregation was found in the lipophilic tetraphenylporphyrin derivatives with substituent at ortho-position in meso-phenyl group. Whereas, protonated tetra-p-torylporphyrin could associate to form some aggregate. These suggest the molecular association is depend on the rotation nature of phenyl-group to yield a planar-type molecular structure.3.The incident angle dependence of reflection spectra was studied using a home-made variable-angle device. Positive and negative bands have been observed in the p-polarized PIR spectra, whose band location correspond to those in p-polarized ER spectra. Nevertheless, the bands in the p-PIR exhibited reversed sign to those of p-ER spectra. These suggest that the interface selection rule of the p-PIR spectrometry has a reversal rule of p-ER, and PIR can also be used for the analysis of molecular orientation. Less