Gemini 2000 spectrometer

The elemental analyses of the synthesized silver(I) complexes for carbon, hydrogen, and nitrogen were performed by the Microanalytical Laboratory, Faculty of Chemistry, University of Belgrade. The ¹H and ¹³C NMR spectra of the N-heterocyclic ligands and the silver(I) complexes were recorded at room temperature on a Varian Gemini 2000 spectrometer (¹H at 200 MHz, ¹³C at 50 MHz). 5.0 mg of each compound was dissolved in 0.6 mL of DMSO-d₆ and transferred into a 5 mm NMR tube. Chemical shifts, δ, are reported in parts per million (ppm) and scalar couplings (J) are reported in Hertz. Chemical shifts were calibrated relative to those of the solvent. The abbreviations for the peak multiplicities are as follows: s (singlet), d (doublet), dd (doublet of doublets), and m (multiplet). In order to investigate the solution behavior of silver(I) complexes, the ¹H NMR spectra were recorded immediately after their dissolution and after 48 h standing in the dark at room temperature. The UV-Vis spectra were recorded on a Shimadzu double-beam spectrophotometer after dissolving the corresponding silver(I) complex in DMSO over the wavelength range of 200–900 nm. The concentration of the silver(I) complexes was 2.36·10⁻⁴ (1), 4.31^.10⁻⁵ (2), and 1.50^.10⁻⁵ M (3). The IR spectra were recorded as KBr pellets on a PerkinElmer Spectrum 100 spectrometer over the wavenumber range of 450–4000 cm⁻¹.

Preparative column chromatography was performed using a silica gel 60 (0.04–0.063 mm, ROSS, Overijse, Belgium). Thin-layer chromatography (TLC) was carried out on Kieselgel 60F₂₅₄ plates (Merck, Darmstadt, Germany) in the following eluent systems: CHCl₃–MeOH 9:1 (A), CHCl₃–MeOH 95:5 (B), CHCl₃–MeOH 97.5:2.5 (C), hexane–ethyl acetate 6:4 (D).
All ¹H NMR spectra were recorded with Varian Gemini-2000 spectrometer (400 MHz, Varian, Palo Alto, CA, USA) in DMSO-d₆ using tetramethylsilane as an internal standard; chemical shifts are given in ppm.
Liquid chromatography mass spectrometry (LC-MS) analysis was performed in positive and negative ion detection mode using Agilent 1100 LC/MSD SL instrument equipped with APCI ionization module (Agilent Technologies, Santa Clara, CA, USA) and Zorbax SB C-18 Rapid Resolution HT Cartridge (4.6 × 30 mm, particle size 1.8 µm) using 0–100% gradient of acetonitrile containing 0.1% formic acid.

Chemicals used in syntheses (4-hydroxybenzaldehyde 99%, acetylacetone, B₂O₃, tri-n-butyl borate 98%, n-butanamine, ethylacetate, palladium(II) acetate, methanol, chloroform) were of reagent grade and were used as purchased. Bisdemethoxycurcumin was synthesized as described previously in the literature [47 (link)]. Intermediate palladium(II) complexes containing N,N,N′,N′-tetramethylcycohexane-1,2-diamine and N,N′-dimethylpiperazine, were prepared based on a reported [30 (link)].
For measurements of NMR spectra, a Varian Gemini 2000 spectrometer was used at a frequency of 300 MHz (for ¹H-NMR) and 75 MHz (for ¹³C-NMR). All spectra were measured in CD₃OD and the chemical shifts are reported relative to TMS used as an internal standard (Supplementary Materials).
The MS measurements were performed on an LTQ Orbitrap XL spectrometer using the electrospray ionization in positive mode. The operating parameters used: spray voltage (SV) 3.6 kV, sheath gas (Sh.G) 5 psi, capillary voltage (CV) 41 V, capillary temperature 275 °C. Spectra were recorded for both complexes (1 and 2) from m/z 150 to 800 (Supplementary Materials).
Infrared spectra were measured with a Nicolet 6700 FT-IR spectrophotometer in the range of 600–4000 cm⁻¹ (Supplementary Materials).