Coordination polymers (CPs) have gained popularity in numerous research areas due to their high surface area and large porosities. Several accounts have suggested their potential for biomedical applications including drug delivery. This research is focused on finding novel crystalline phases of previously synthesized CPs using a bisphosphonate (BP) ligand and the bioactive zinc (II) ion. It is hypothesized that employing the same starting materials, but changing the synthesis conditions (temperature, molar ratio, pH) may lead to the development of materials presenting larger surface areas and increased porosity than those reported thus far. Hydrothermal synthesis of the starting materials produced a new phase, BP-Zn form II, which was obtained by changing the molar ratio (Zn(II)/BP) from 2:1 to 1:1 and increasing the pH from 7.00 to 7.25 with respect to BP-Zn form I. BP-Zn form II was thoroughly characterized using optical microscopy, Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and powder and single crystal X-ray diffraction. Polarized microscopy demonstrated the single crystal quality of the produced material, while SEM gave a closer look at its morphology. Raman spectra of the product helped to assign active vibrational modes characteristic to phosphate groups, and Zn-O shifts. Thermal stability was investigated by TGA and the decomposition of the ligand and metal were observed. EDS confirmed the presence of a CP with signals from both BP and Zn(II). PXRD patterns of the new phase demonstrated low angle reflections indicative of a porous network and a unique crystalline arrangement compared to BP-Zn form I. Elucidation of the structure yielded a good R-factor (4.16%) with an adequate solution corroborated by overlaying the simulated and experimental PXRDs. These methods provided evidence that an unprecedented phase has been obtained and gives insights into other potential phases for CPs with better properties than those currently reported.

Synthesis and elucidation of a novel crystalline phase for a phosphonate-based biocompatible coordination polymer

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.