Сольватохромні та протонохромні властивості 4-гідроксістирилових барвників

Abstract

Нами синтезовано та досліджено поведінку у водних та органічних розчинах деяких 4-гідроксістирилових барвників – похідних 1,3,3-триметил-3Н-індолію, 1- метил- і 1,5,6-триметилбензтіазолію, 4-(N-етил)піридинію та 2- і 4-(N-етил)хінолінію.

The solvatochromic and protochromic properties of synthesized 4-hydroxystyryl merocyanine dyes – derivatives of 1,3,3-trimethylindolenine (TMI), 1,5,6 trimethylbenztiazole (TMB), 4-ethylpyridine (EP-4), 2-(MQ-2) and 4-methylquinoline (EQ-4) have been investigated. Absorption maximums of merocyanine forms in different solvents has been determined by specrophotometric method. The influence of heterocyclic and styrene fragments on absorption maximums has been studied. The transformation protonated form to merocyanine is accompanied by bathochromic shift more than 100 nm. Absorption maximums of cationic and merocyanine forms and acidity constants (pKa) such dyes have been determined by specrophotometric method. Acidity constants (pKa) of 4-hydroxystyryl dyes are: 7,78 (TMB-MS); 8,54 (EP4-MS). Molar absorption coefficients of merocyanine forms are much higher in organic solvents than aqueous ones and lie within (4-8)×104 l·mol-1·sm-1. Dyes can be divided by increasing of maximums of solvatochromic shifts λmax (water-DMSO) in such range: EQ4-DMS > EP4-DMS > MP4-S > MP2-S > EP4-MS > TMB-MS > MQ2-DMS > TMBDMS > TMI-S > TMI-MS.