Rx1 ft ir spectrometer

Commercial chemicals and solvents were used without purification. NMR spectra were measured on a Bruker 400 MHz FT-NMR spectrometer (Bruker, Falladen, Switzerland) using DMSO-d₆ as solvent. HRESI mass spectra were recorded at the Department of Chemistry at the University of Singapore on a MAT 95 x1-T spectrometer at 70 eV (Agilent Technologies, Santa Clara, CA, USA). Melting points were determined using a Mel-Temp II melting point apparatus (Laboratory Devices Inc., Holliston, MA, USA) and are uncorrected. IR spectra were recorded on a RX1 FT-IR spectrometer (Perkin-Elmer, Waltham, MA, USA). The absorbance of the reaction mixtures in the DPPH and FRAP assays were determined by UV spectroscopy using a Power Wave X340, BioTek Inc, Instrument (Winooski, VT, USA). The detailed spectrums and analyze are available in Supplementary Materials.

All materials and solvents were obtained from Sigma–Aldrich (St. Louis, MO, USA). Melting points were determined on a MEL-TEMP II melting point instrument (Barnstead/Thermolyne Corp, North Sioux, SD, USA). IR spectra were recorded on a RX1FT-IR spectrometer (Perkin–Elmer, Waltham, MA, USA). The ¹H- (400 MHz) and ¹³C-NMR (100 MHz) spectra were recorded on a 400 MHz FT-NMR (JEOL Ltd., Tokyo, Japan) using CDCl₃ as a solvent and tetramethylsilane as an internal standard. The abbreviations s = singlet, d = doublet, t = triplet, q = quadruplet, m = multiplet and bs = broad signal were used throughout. HR-mass spectra (ESI) were obtained with a Finnigan MAT95XL mass spectrometer at 70 eV (Thermo Fisher Scientific, Waltham, MA, USA). UV-visible spectra were recorded on a model UV-1650PC UV-visible spectrophotometer (Shimadzu Europe, Duisburg, Germany). The Supplementary Data section reports the ¹H-NMR (Figures S1–S8) and ¹³C-NMR (Figures S9 and S10) spectral data of compounds 3–10.