Molecular Engineering of Triphenylamine Based Aggregation Enhanced Emissive Fluorophore: Structure-Dependent Mechanochromism and Self-Reversible Fluorescence Switching

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• 作者：Palamarneri Sivaraman Hariharan ; Viki Kumar Prasad ; Surajit Nandi ; Anakuthil Anoop ; Dohyun Moon ; Savarimuthu Philip Anthony
• 刊名：Crystal Growth & Design
• 出版年：2017
• 出版时间：January 4, 2017
• 年：2017
• 卷：17
• 期：1
• 页码：146-155
• 全文大小：682K
• ISSN：1528-7505

文摘

Triphenylamine (TPA), a propeller-shaped optoelectronic molecule, has been used to generate stimuli-responsive smart fluorescent organic materials and correlate the effect of subtle structural changes on the molecular packing and mechanochromic fluorescence (MCF). The substituent (OCH₃) position in the TPA phenyl ring and acceptors (malononitrile, cyanoacetamide, cyanoacetic acid, ethyl cyanoacetate, and diethylmalonate) strongly influenced the solid state and mechanochromic fluorescence as well as the molecular packing. The structure–property studies revealed that (i) TPA derivatives without the OCH₃ substituent exhibit strong fluorescence (Φ_f = 85% (TCAAD-1, 55% (TDEM)), (ii) higher dihedral angle (τ) between donor (aminophenyl) and acceptor lead to weak/non fluorescent material, (iii) substituent at the ortho position to acceptor increased the dihedral angle (τ = 26.49 (TCAAD-2), τ = 27.14 (TDMM)), and (iv) the increase of alkyl groups produced self-reversible high contrast off-on fluorescence switching materials (TDEM). Powder X-ray diffraction studies indicate that stimuli induced reversible phase transformation from crystalline to amorphous and vice versa was responsible for fluorescence switching. The computational studies also supported that OCH₃ substitution at ortho to acceptor increased the dihedral angle and optical band gap. Thus, the present studies provide a structural insight for designing TPA based organic molecules for developing new smart organic materials.