Esi tof ms

UV-Vis absorption spectra was recorded on a Shimadzu UV-2550 Spectrophotometer. Mass spectrum was recorded on an Agilent Technologies ESI-TOF-MS. Fourier-transform infrared spectroscopy (FT-IR) spectra were collected in the range of 4000–400 cm⁻¹ with a Bruker FT-IR spectrometer. Nuclear magnetic resonance (NMR) data were collected on a JEOL ECS-400 spectrometer. X-ray photoelectron spectroscopy (XPS) studies were performed on PHI Quantum-2000 XPS. The sample was put under UHV to reach the10⁻⁸ Pa range. The non-monochromatized Al Kα source was used at 10 kV and 10 mA. All binding energies were calibrated using the C (1s) carbon peak (284.6 eV), which was applied as an internal standard. High resolution narrow-scan spectra were recorded with the electron pass energy of 50 eV and takeoff angle of 55° to achieve the maximum spectral resolution.

Negative ion mode ESI-MS of the DMF solutions of crystals of 1′ and 2′ were measured on an LTQ linear ion trap spectrometer by Agilent Technologies ESI-TOF-MS (6230). The spray voltage was 5.48 kV and the capillary temperature was kept at 300 °C. The capillary voltage was 30 V. The samples were made up inside a glovebox under a nitrogen atmosphere and rapidly transferred to the spectrometer in an airtight syringe by direct infusion with a Harvard syringe pump at 0.2 mL/min.