5 bromo 2 hydroxybenzaldehyde

4-Aminobenzoic hydrazide, 5-bromo-2-hydroxybenzaldehyde, tungsten(vi) chloride (WCl₆), propionyl chloride-functionalized silica gel (1 mmol g⁻¹ loading) and solvents were purchased from Sigma-Aldrich and used as received. FT-IR spectra were recorded as KBr disks with a Bruker FT-IR spectrophotometer. The UV-Vis spectra of solution were recorded on a thermos-spectronic Helios Alpha spectrophotometer between 200-800 nm. The ¹H and ¹³C NMR spectra were taken from Bruker DRX-300 spectrometer in DMSO-d₆ solution. Diffuse-reflectance UV-Vis spectroscopy (DRS) were recorded with Sinco S4100 instrument. Elemental analyses (C, H, N) were performed on a Carlo ERBA Model EA 1108 analyzer and the tungsten content of the compounds was measured by atomic absorption spectroscopy using a Varian AA-220 instrument. Thermal gravimetric analysis (TGA) curves were taken from TA Q600 instrument in the range of 25–1000 °C. X-ray diffraction analyses (XRD) for heterogeneous catalyst were obtained from PHILIPS PW1730 instrument. Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were recorded with TESCAN MIRA III instrument. X-ray photoelectron spectroscopy (XPS) analysis was performed by using a Bes Tec 8025 instrument.

1,10-phenanthrolin-5-amine, 5-bromo-2-hydroxybenzaldehyde, and thiophene-3-carbaldehyde were procured from Sigma (Sigma, Mumbai, India), and S.D. Chemicals (RD Chem, Mumbai, India) and used without further purification. All the solvents were obtained from Merck (Goa, India), which were dried before using them in the experiments. Thin Layer Chromatography (TLC) was used to check the completion of reaction by spotting the reaction mixture on pre-coated silica-gel plates (Merck, Mumbai, India) and the spots were visualized by UV irradiation. Infrared spectral studies were performed on Perkin-Elmer spectrometer (PerkinElmer, Waltam, MA, USA) version 10.03.09 (KBr pellet technique). ¹H and ¹³C NMR were recorded on a 500 MHz Bruker Avance DPX spectrometer (Bruker, Ettlingen, Germany) with TMS as internal standard. Mass spectra (ESI-MS) of the compounds were measured on Agilent mass spectrometer (Agilent, Santa Clara, CA, USA). The UV-Visible absorption spectra were recorded using UV-1800 spectrophotometer (Shimadzu, Koyto, Japan).