Shreykar Milind R, Sekar Nagaiyan
Department of Dyestuff Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai, 400019, India.
J Fluoresc. 2017 Sep;27(5):1687-1707. doi: 10.1007/s10895-017-2106-2. Epub 2017 May 13.
The newly synthesized three coumarin pyrazole hybrid excited state intramolecular proton transfer (ESIPT) dyes show efficient charge transfer from the pyrazole ring and the coumarin towards the electron withdrawing dicyanovinylene group as revealed from the frontier molecular orbitals. Aggregation induced emission enhancement (AIEE) studies with 2-((3-(4-hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)methylene) malononitrile showed 9 fold increase in the emission enhancement in 90% DMF-HO mixture. Lippert-Mataga theory explained the solvatochromic behavior of the dyes in various solvents. The charge transfer characteristics and non-linear optical (NLO) properties have been supported and correlated with bond length alternation, bond order alternation and vibrational spectrum. As values of bond order alternation (BOA) tend to be more towards negative and as the value of α increases β decreases while the values of γ depends on the values of α and β. The observed values of γ are positive which revealed that β contributes significantly. The dyes exhibit linear and NLO properties superior to urea. (E)-2-(3-(2-(3-(4-Hydroxy-2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile shows enhanced linear and non-linear properties among the three dyes.
新合成的三种香豆素吡唑杂化激发态分子内质子转移（ESIPT）染料显示，从前沿分子轨道可以看出，存在从吡唑环和香豆素向吸电子二氰基亚乙烯基的有效电荷转移。对2-((3-(4-羟基-2-氧代-2H-色烯-3-基)-1-苯基-1H-吡唑-4-基)亚甲基)丙二腈的聚集诱导发光增强（AIEE）研究表明，在90%二甲基甲酰胺-水混合物中，发光增强增加了9倍。Lippert-Mataga理论解释了染料在各种溶剂中的溶剂化显色行为。电荷转移特性和非线性光学（NLO）性质得到了支持，并与键长交替、键级交替和振动光谱相关。由于键级交替（BOA）值更趋于负值，且随着α值的增加β值减小，而γ值取决于α和β的值。观察到的γ值为正，这表明β有显著贡献。这些染料表现出优于尿素的线性和NLO性质。（E）-2-（3-（2-（3-（4-羟基-2-氧代-2H-色烯-3-基）-1-苯基-1H-吡唑-4-基）乙烯基）-5,5-二甲基环己-2-烯-1-亚基）丙二腈在这三种染料中显示出增强的线性和非线性性质。
