Materials Solvents such as THF, chloroform, dichloromethane (DCM), and hexane were distilled under normal pressure under nitrogen immediately prior to use. Milli-Q water was used as deionized water. 4-Bromobenzaldehyde, tetrakis(triphenylphosphine)palladium(0), citric acid, and sodium hydrogen phosphate were purchased from Sigma-Adrich. Aniline was purchased from Int. Lab. All the chemicals were used as received without further purification. Compound 1 1 and 4 2 were prepared according to the

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... eviously published procedures. Buffer solutions with pH 113 were purchased from Merk, Riedel-de Haen and Sigma-Aldrich. Buffers with pH 5.107.13 were prepared by citric acid and sodium hydrogen phosphate 3 and confirmed by pH meter. The aqueous mixtures of TPE-Cy for pH-responsive UV and PL tests were prepared by adding an aliquot of DMSO stock solution into aqueous buffers with specific pH values. Instruments pH measurements were performed on a Beckman 340 pH/Temp meter. 1 H and 13 C NMR spectra were measured on a Bruker ARX 400 NMR spectrometer using CDCl 3 , DMSO-d 6 , or D 2 O as solvent and tetramethylsilane (TMS) as internal reference. UV absorption spectra were taken on a Milton Ray Spectronic 3000 array spectrophotometer. Photoluminescence (PL) spectra were recorded on a Perkin-Elmer LS 55 spectrofluorometer. Solid state quantum efficiency was measured using an integrating sphere at an excitation wavelength of 325 nm. High-resolution mass spectra (HRMS) were obtained on a GCT Premier CAB 048 mass Electronic Supplementary Material (ESI) for Chemical Science This journal is