Synthesis, spectroscopic and structural elucidation of discrete, one dimensional and two dimensional coordination compounds of 1,3,5-triaza-7-phosphaadamantane, N-methyl-1,3,5-triaza-7-phosphaadamantane and silver(I).
Zamisa, Sizwe Joshua.
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Novel discrete complexes and coordination polymers of silver(I) and the water soluble 1,3,5-triaza-7-phosphaadamantane (PTA) or N-methyl-1,3,5-triaza-7-phosphaadamantane (PTAMe) have been isolated from the reactions of various silver(I) salts (AgX; X = CNˉ, CO₃²ˉ, NO₃ˉ, O₂CCH₃ˉ, O₂CCF₃ˉ, ClO₄ˉ, O₃SCF₃ˉ, O₃SCCH₃ˉ, BF₄ˉ) with PTA or PTAMe giving a total of 15 compounds. The Ag-PTA coordination compounds are named DCC₁₋₃ for discrete complexes, CP₁₋₅ for one dimensional coordination polymers and CN₁₋₅ for two dimensional coordination networks while the Ag-PTAMe coordination compounds are named m-CP₁₋₄ for one dimensional coordination polymers. The synthesized silver(I) coordination compounds were analysed using Nuclear Magnetic Resonance (NMR) spectroscopy, infrared spectroscopy (IR), Electron Spray Ionization Mass Spectrometry (ESI-MS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Coordination of PTA and PTAMe via the phosphorus and nitrogen atoms of the PTA moieties was confirmed by ¹H-, and ³¹P-NMR. IR spectroscopic studies confirmed the presence of ligands and the silver(I) salt counter ions used whilst the ESI-MS results showed m/z peaks that are attributed to the products, fragmentation of the polymeric species and the formation of multiple charged ionic species. Thermal stability studies (TGA and DSC) revealed that the silver(I)-PTA coordination compounds were thermally stable up to approximately 210 °C. [Ag(PTA)(μ²-O₂CCH₃)]n.2H₂O (CP₂) and [Ag(PTA)(μ¹-O₂CCF₃)]n (CP₃) formed double stranded, ladder-like structures in which the carboxylate anions bridge Ag(I) centres in a μ²-O₂ and μ¹-O₂ fashions resulting in short and long Ag…Ag separation, respectively. [Ag₂(μ²-O₂CCF₃)₂(μ¹-O₂CCF₃)(PTAMe)]n (m-CP₃) has a 1D single stranded coil-like structure which contains PTAMe groups coordinating via the phosphorus atom only. The polymer propagates via the trifluoroacetate groups which bridge the Ag(I) centres in an alternating μ₂-O₂ and μ₁-O₂ bridging modes. The two bridging modes of the trifluoroacetate groups also resulted in the formation of alternating segments displaying Ag…Ag interactions and non-Ag…Ag interactions along the coil-like polymer. 2D coordination networks [Ag(PTA)(H₂O)]n(NO₃)n (CN₁) and [Ag₂(PTA)₂(H₂O)]n(O₃SCF₃)₂n (CN₂) have stacked 2D corrugated sheet-like structures with channels filled with uncoordinated anions between the stacked sheets. The 2D networks contained PTA groups that displayed an alternating P-,N-,N’- coordination mode which is responsible for the growth of the polymer. O-H…O, O-H…N, C-H…O, C-H…N and C-H…F types of hydrogen bonding were observed in most crystal structures. This work also included the preparation of a silver(I)-PTA coordination compound containing ancillary ligands such as 4-nitrophenol from the solvothermal reaction of AgNO₃, PTA and 4-nitrophenol (4-NP). In an attempt to grow crystals for structural determination, a discrete, tri-coordinated silver-PTA complex [Ag(PTA)₃][4-NP]̣₁₀ (DCC₃) crystallized in a monoclinic system that co-crystallized along with ten molecules of 4-nitrophenol and a two-dimensional silver(I)-PTA sheet-like polymer [Ag₂(PTA)₂(μ₁-NO₃)(H₂O)](NO₃)(4-NP)(H₂O) (CN₅) co-crystallized with the 4-NP molecules positioned in between the sheets were obtained.