21:T54f,Guanosine monophosphate, among the nucleotides, has the unique property to self-associate and form nanoscale cylinders consisting of hydrogen-bonded G-quartet disks, which are stacked on top of one another. Such self-assemblies describe not only the basic structural motif of G-quadruplexes formed by, e.g., telomeric DNA sequences, but are also interesting targets for supramolecular chemistry and nanotechnology. The G-quartet stacks serve as an excellent model to understand the fundamentals of their molecular self-association and to unveil their application spectrum. However, the thermodynamic stability of such self-assemblies over an extended temperature and pressure range is largely unexplored. Here, we report a combined FTIR and NMR study on the temperature and pressure stability of G-quartet stacks formed by disodium guanosine 5'-monophosphate (Na₂5'-GMP). We found that under abyssal conditions, where temperatures as low as 5 °C and pressures up to 1 kbar are reached, the self-association of Na₂5'-GMP is most favoured. Beyond those conditions, the G-quartet stacks dissociate laterally into monomer stacks without significantly changing the longitudinal dimension. Among the tested alkali cations, K⁺ is the most efficient one to elevate the temperature as well as the pressure limits of GMP self-assembly.22:T4ed,The syntheses of the novel amino alcohols NH(CH₂CMe₂OH)₂(CMe₂CH₂OH) (1) and N(CH₂CMe₂OH)(CMe₂CH₂OH)(CH₂CH₂OH) (2) as well as the stannatranes N(CH₂CMe₂O)(CMe₂CH₂O)(CH₂CH₂O)SnX (3, X = Ot-Bu), N(CH₂CMe₂O)₃SnOC(O)C₉H₁₃O₂, 4, and germatranes N(CH₂CMe₂O)(CMe₂CH₂O)(CH₂CH₂O)GeX (5, X = OEt; 6, X = Br) are reported. The compounds were characterized by ¹H, ¹³C (1-6), ¹¹⁹Sn (3, 4), and ¹⁵N (2, 3, 5) NMR and IR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray diffraction analysis. Graphset analyses were performed for compounds 1 and 2. Detailed NMR spectroscopic studies including variable temperature ¹H (3, 5, 6) and ¹¹⁹Sn (3, 4) DOSY experiments reveal the stannatrane 3 being involved in a monomer-dimer equilibrium. Both the stannatranes 3 and 4 as well as the germatranes 5 and 6 show Λ ⇌ Δ isomerization of the atrane cages in solution.

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