Study the crystal structure of 4,4′-(propane-1,3-diyl)dipiperidinium sulfate monohydrate and its hydrogen bond catalytic activity in the mechanochemical synthesis of BIMs

Abstract

The crystal structure and vibrational frequencies of 4,4′-(propane-1,3-diyl)dipiperidinium sulfate monohydrate were investigated. Nanosize of particles and interplanar spacing were confirmed by XRD analysis. Robust electrostatic interaction and hydrogen bonding between [TMDPH2]2+, [SO4]2−, and water of crystllization, demonstrated by single-crystal X-ray diffraction, cause a high melting point and thermal stability (290–307 °C). Crystal structure parameters were studied and discussed in details and compared with previous report. The mechanosynthesis of bis(3-indolyl)methanes using as-prepared organic salt hydrated with strong and multi-hydrogen bonding using a planetary ball mill was demonstrated. The solvent-free and metal-free conditions and the mechanochemical process are some of the green and sustainable principles in the current hydrogen bond catalytic synthesis of BIMs. The organic salt catalyst showed high recyclability with any changes in chemical structure and loss of its catalytic activity. The present method was scalable and generated minimal hazardous wastes, and it can be apply to continuous mode using twin-screw extrusion.