1,3,5-Triaza-7-phosphaadamantane-7-oxide (PTAO): New Diamondoid Building Block for Design of Three-Dimensional Metal–Organic Frameworks

The facile self-assembly reactions of 1,3,5-triaza-7-phosphaadamantane-7-oxide (PTAO) with AgNO3 or Ag2SO4 give rise to the generation of two new distinct silver–organic frameworks [Ag(NO3)(μ3-PTAO)]n (1) and [Ag2(μ2-SO4)(μ5-PTAO)(H2O)]n (2), respectively. They have been characterized by IR, 1H and 31P{1H} NMR spectroscopies, electrospray ionization-mass spectrometry (ESI-MS)(±), and elemental and single-crystal X-ray diffraction analyses, the latter featuring infinite three-dimensional (3D) non-interpenetrating networks driven by multiply bridging PTAO spacers that adopt undocumented N2O- or N3O-coordination modes. The topological analysis of 1 reveals a uninodal 3-connected net with the point (Schläfli) symbol of (103) and the srs topological type, whereas 2 shows a rare trinodal 3,4,5-connected net with the unprecedented topology defined by the point symbol of (5.6.7)(54.6.8)(54.63.83). Compounds 1 and 2 represent the first 3D metal–organic frameworks (MOFs) derived from PTAO or any cage-like PTA derivative, thus opening up their underexplored applications as versatile building blocks in crystal engineering. Furthermore, 1 and 2 exhibit significant antibacterial and antifungal activities studied in vitro against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans.