Antiviral, Antibacterial, Antifungal, and Cytotoxic Silver(I) BioMOF Assembled from 1,3,5-Triaza-7-Phoshaadamantane and Pyromellitic Acid

Abstract

The present study reports the synthesis, characterization, and crystal structure of a novel bioactive metal-organic framework, [Ag₄(µ-PTA)₂(µ₃-PTA)₂(µ₄-pma)(H₂O)₂]_n·6nH₂O (bioMOF 1), which was assembled from silver(I) oxide, 1,3,5-triaza-7-phosphaadamantane (PTA), and pyromellitic acid (H₄pma). This product was isolated as a stable microcrystalline solid and characterized by standard methods, including elemental analysis, ¹H and ³¹P{¹H} NMR and FTIR spectroscopy, and single crystal X-ray diffraction. The crystal structure of 1 disclosed a very complex ribbon-pillared 3D metal-organic framework driven by three different types of bridging ligands (µ-PTA, µ₃-PTA, and µ₄-pma^4-). Various bioactivity characteristics of bioMOF 1 were investigated, revealing that this compound acts as a potent antimicrobial against pathogenic strains of standard Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria, as well as a yeast (Candida albicans). Further, 1 showed significant antiviral activity against human adenovirus 36 (HAdV-36). Finally, bioMOF 1 revealed high cytotoxicity toward an abnormal epithelioid cervix carcinoma (HeLa) cell line with low toxicity toward a normal human dermal fibroblast (NHDF) cell line. This study not only broadens the family of PTA-based coordination polymers but also highlights their promising multifaceted bioactivity.

Keywords: 1,3,5-triaza-7-phosphaadamantane; antimicrobial activity; antiviral activity; coordination polymers; cytotoxic activity; metal-organic frameworks; pyromellitic acid; silver complexes.

Scheme 1

Synthesis of 1 and its structural formula.

Figure 1

Crystal structure of 1. (a) Connectivity of Ag(I) centers and ligands. (b) One-dimensional (1D) chain motif (ribbon) based on honeycomb-like [Ag₃(PTA)₃]_n subunits. (c) Ribbon-pillared 3D metal-organic framework. (d) Topological view of 3D net showing a 3,3,4,4-linked tetranodal framework. Details: (a–c) H atoms and crystallization H₂O are omitted, Ag (magenta balls), P (orange), N (blue), O (red), and C (cyan); (c, d) view along the b axis; (d) 3- and 4-connected Ag1/Ag2 atoms (magenta balls), centroids of 4-connected µ₄-pma²⁻ blocks (cyan), and centroids of µ- and µ₃-PTA blocks (blue).