Spange Stefan, Prause Silvio, Vilsmeier Elmar, Thiel Werner R
Polymer Chemistry and Biophysical Chemistry, Institute of Chemistry, Chemnitz University of Technology, Strasse der Nationen 62, D-09111 Chemnitz, Germany.
J Phys Chem B. 2005 Apr 21;109(15):7280-9. doi: 10.1021/jp040521z.
Solvatochromism and sorptiochromism of the dye 3-(4-amino-3-methylphenyl)-7-phenyl-benzo1,2b:4,5b'difuran-2,6-dione (1) are studied with an extended set of solvents and various solid acids including silicas, aluminas, and alumosilicates. 1 shows a positive solvatochromism with increasing basicity and dipolarity/polarizability of the solvent; its solvent-induced bathochromic UV-vis absorption band shift ranges from formic acid (upsilon(max) = 21 630 cm(-1)) to hexamethylphosphoric acid triamide (upsilon(max) = 14 200 cm(-1)). Multiple square analyses of upsilon(max) of the solvent-dependent solvatochromic UV-vis absorption band of 1 with several empirical solvent polarity parameters prove that a composite of basicity, acidity, and dipolarity/polarizability of the environment must be taken into account. For the analysis of the solvent-dependent UV-vis shift of 1, the Kamlet-Taft and Catalan solvent parameters have been evaluated. It could be shown that the Catalan solvent parameter set is more suitable to reflect multiple solvation processes involving both strong basic and strong acidic solvents. Quantum chemical calculations indicate that an interaction of the silanol oxygen atom with the protons of the amino group is clearly favored over various acidic attacks of silanol groups upon 1. Accordingly, surface basicity of silica, alumina, and alumosilicates can be determined using the linear solvation energy relationship derived from the solvent-dependent UV-vis band of 1. An unambiguous interpretation of the UV-vis spectroscopic data of 1 adsorbed on surfaces containing Lewis-acid sites is sometimes difficult. UV-vis monitoring of 1-loaded solid acids during surface titration with 2,6-di-tert-butyl pyridine allows the discrimination of whether Brønsted- or Lewis-acid sites interfere with 1. Additionally, adsorbed water has an important influence on the actual surface basicity of solid acids. 1 is recommended as a sensitive probe for checking both basicity and acidity when directly compared with solvatochromism of the established hydrogen-bond-donating indicator (cis-dicyano)bis(1,10-phenanthroline)iron(II) (2).
研究了染料3-(4-氨基-3-甲基苯基)-7-苯基-苯并[1,2 -b:4,5 -b']二呋喃-2,6-二酮(1)在一系列溶剂以及包括二氧化硅、氧化铝和硅铝酸盐在内的各种固体酸中的溶剂致变色和吸附致变色现象。1随着溶剂碱性和偶极矩/极化率的增加呈现正溶剂致变色；其溶剂诱导的紫外-可见吸收带红移范围从甲酸(υ(max)=21630 cm⁻¹)到六甲基磷酸三酰胺(υ(max)=14200 cm⁻¹)。用几个经验性溶剂极性参数对1的溶剂依赖性溶剂致变色紫外-可见吸收带的υ(max)进行多元平方分析证明，必须考虑环境的碱性、酸性和偶极矩/极化率的综合作用。为了分析1的溶剂依赖性紫外-可见位移，评估了Kamlet-Taft和加泰罗尼亚溶剂参数。结果表明，加泰罗尼亚溶剂参数集更适合反映涉及强碱性和强酸性溶剂的多种溶剂化过程。量子化学计算表明，硅醇氧原子与氨基质子的相互作用明显优于硅醇基团对1的各种酸性攻击。因此，可以使用从1的溶剂依赖性紫外-可见带导出的线性溶剂化能关系来确定二氧化硅、氧化铝和硅铝酸盐的表面碱性。对吸附在含有路易斯酸位点的表面上的1的紫外-可见光谱数据进行明确解释有时很困难。在用2,6-二叔丁基吡啶进行表面滴定时，对负载1的固体酸进行紫外-可见监测，可以区分布朗斯台德酸或路易斯酸位点是否与1相互作用。此外，吸附的水对固体酸的实际表面碱性有重要影响。与已确立的氢键供体指示剂(顺式-二氰基)双(1,10-菲咯啉)铁(II)(2)的溶剂致变色现象直接比较时，1被推荐为检查碱性和酸性的灵敏探针。
